JP5118947B2 - Nano surface modification method with enhanced high-temperature durability, metal member subjected to nano surface modification method, and exhaust guide assembly in VGS type turbocharger to which this member is applied - Google Patents

Nano surface modification method with enhanced high-temperature durability, metal member subjected to nano surface modification method, and exhaust guide assembly in VGS type turbocharger to which this member is applied Download PDF

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JP5118947B2
JP5118947B2 JP2007302151A JP2007302151A JP5118947B2 JP 5118947 B2 JP5118947 B2 JP 5118947B2 JP 2007302151 A JP2007302151 A JP 2007302151A JP 2007302151 A JP2007302151 A JP 2007302151A JP 5118947 B2 JP5118947 B2 JP 5118947B2
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隆弘 秋田
健介 三浦
茂 平田
雄二 池上
寛治 青木
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Nippon Yakin Kogyo Co Ltd
Air Water Inc
Akita Fine Blanking Co Ltd
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本発明は、例えばステンレス鋼に事前フッ化処理を行うことによる浸炭処理や浸窒処理を現実に行えるようにした表面改質処理（公知）において、低温（500 ℃前後）非平衡過飽和浸炭／浸窒時に、結晶粒内にナノ寸法レベルの転位（以下、これを「浸入型原子誘起転位」と称する）が導入され、消滅することなく温存されることを知見し、ステンレス鋼の熱処理サイクルによって生じる元来忌避すべき鋭敏化現象（Ｃｒ炭化物の粒界析出による粒界や粒界脆化を生じ易いため）を結晶粒内にあえて故意に生じせしめて（以下、これを「擬鋭敏化」と称する）、鋼材の高温耐久性向上に生かすようにした新規なナノ表面改質処理手法に係るものである。因みに、本発明の名称において、表面改質の前に「ナノ」と付したのは、ナノ寸法レベルの転位（数ナノメートル〜数100 ナノメートル）を析出核生成サイトに利用するためである（図４参照）。   The present invention provides a low temperature (around 500 ° C.) non-equilibrium supersaturated carburization / carburization in a surface modification process (known) that can actually perform a carburizing process or a nitrocarburizing process by, for example, pre-fluoriding a stainless steel. It is found that during the nitriding, a nano-dimensional dislocation (hereinafter referred to as “intrusion-type atom-induced dislocation”) is introduced into the crystal grains and is preserved without disappearing, and is caused by a heat treatment cycle of stainless steel. Sensitive sensitization that should be avoided by nature (because it tends to cause grain boundaries and grain boundary embrittlement due to grain boundary precipitation of Cr carbide) intentionally in the crystal grains (hereinafter referred to as “pseudo-sensitization”) This relates to a novel nano-surface modification method that is used to improve the high-temperature durability of steel materials. Incidentally, in the name of the present invention, “nano” was given before the surface modification in order to use a nano-dimensional dislocation (several nanometers to several hundred nanometers) as a precipitation nucleation site ( (See FIG. 4).

一般に金属素材の表面から炭素や窒素を浸透させて、素材の表面硬化を図る手法が知られており、これらは各々、浸炭処理、浸窒処理と称されている。しかしながら、浸炭処理だけをみても、全ての金属素材を対象として行える処理法はなく、例えば耐食性に優れた鋼材として知られているオーステナイト系ステンレス鋼には、この浸炭処理が不向きであることが知られている。これは、一つには耐食性に寄与する不動態皮膜（クロム水和化合物）が表層に形成されること、二つにはこの材料の原子密度の高い面心立方結晶からなる単一相組織に起因し、更にはFe、Cr、Ni原子相互間の結合エネルギ（原子間力）が歪場を形成し、浸炭／浸窒を阻害するためである。従って、通常は少なくとも930 ℃以上の高温下で、特に第３の要因を緩和して浸炭／浸窒を行わざるを得ない。この際に、浸入型原子誘起転位（図４参照）が生じるかも知れないが、高温下処理であるため、瞬時に解放・消滅してしまうのである。前記〔０００１〕において述べた浸炭／浸窒処理は、これよりはるかに低温の400 〜650 ℃で行うことを可能にしたものであるが、この処理中に浸入型原子誘起転位が結晶粒内に微細・高密度に導入・温存されることを透過電子顕微鏡で確認・知見し、これを利用したことによる、従来にない新規且つ進歩性に富む高温耐久性向上を可能にした新表面改質法を実現したものである。   In general, there is known a technique for infiltrating carbon or nitrogen from the surface of a metal material to achieve surface hardening of the material, and these are called carburizing treatment and nitrocarburizing treatment, respectively. However, even if only carburizing treatment is considered, there is no processing method that can be applied to all metal materials.For example, it is known that this carburizing treatment is not suitable for austenitic stainless steel known as a steel material having excellent corrosion resistance. It has been. This is because, in part, a passive film (chromium hydrated compound) that contributes to corrosion resistance is formed on the surface, and in part, this material has a single-phase structure consisting of face-centered cubic crystals with high atomic density. This is because the bond energy (interatomic force) between Fe, Cr, and Ni atoms forms a strain field and inhibits carburizing / nitriding. Therefore, the carburization / nitrogenation must be carried out usually at a high temperature of at least 930 ° C., particularly by mitigating the third factor. At this time, intrusion-type atom-induced dislocations (see FIG. 4) may occur, but since they are processed at a high temperature, they are released and disappeared instantaneously. The carburizing / nitriding treatment described in [0001] can be carried out at a temperature much lower than 400 to 650 ° C. During this treatment, the intrusion-type atom-induced dislocations are formed in the crystal grains. A new surface modification method that enables the improvement of high-temperature durability, which has never been seen before, and which is highly innovative by confirming and finding out that it is introduced and preserved in a fine and high-density manner using a transmission electron microscope. Is realized.

すなわち、本出願人は、ステンレス鋼に対しても浸炭処理や浸窒処理を実現できる技術を見出すべく鋭意研究開発を行い、事前にフッ化処理を行えば、浸炭処理や浸窒処理が行えることを見出し、当該素材を対象とした浸炭処理／浸窒処理に関する発明の特許出願、及び特許取得に至っている（例えば特許文献１、２参照）。この特許文献１、２では、いずれも処理温度を低温（例えば約500 ℃程度）にし、被処理材の寸法変化を大幅に低減させつつ、それまで不可能と考えられていた浸炭処理や浸窒処理を、特にオーステナイト系ステンレス鋼についても現実に行い得るようにした点で斯界の期待に応え得たと言える。しかしながら、現存する種々の表面改質処理及び、この事前フッ化処理を伴う低温浸炭や浸窒処理のいずれにおいても、量産性と経済性とを前提とした高温耐久性（特に熱サイクルを伴う長時間耐久）は不十分であり、必要十分な高温耐久性を有する新しい表面改質手法が強く望まれていた。そして、本出願人は、ステンレス鋼を対象とする当該処理技術を実用化レベルに具現化しただけにとどまらず、更に探究を続け、その過程において以下のような知見を見出した。   In other words, the present applicant has conducted intensive research and development to find a technology that can realize carburizing treatment and nitriding treatment even for stainless steel, and if fluorination treatment is performed in advance, carburizing treatment and nitriding treatment can be performed. The patent application of the invention regarding the carburizing process / nitriding process for the material and the patent acquisition have been achieved (for example, refer to Patent Documents 1 and 2). In each of Patent Documents 1 and 2, the processing temperature is low (for example, about 500 ° C.), and the dimensional change of the material to be processed is greatly reduced. It can be said that it was possible to meet the expectation of the world in that the treatment could be actually performed especially for austenitic stainless steel. However, in any of various existing surface modification treatments and low-temperature carburizing and nitrocarburizing treatments involving this pre-fluorination treatment, high-temperature durability (especially with long thermal cycles) is premised on mass production and economic efficiency. Time durability) is insufficient, and a new surface modification method having high and sufficient high temperature durability has been strongly desired. The present applicant has not only realized the processing technology for stainless steel at a practical level, but has continued to search, and has found the following knowledge in the process.

すなわち本出願人は、特許文献１、２による表面改質処理を行った被処理材の内部には、例えば図４に示すように、炭素原子（または窒素原子）が非平衡・過飽和に拡散浸透する際に結晶粒内にナノ寸法レベル（数ナノメートル〜数100 ナノメートル）の浸入型原子誘起転位が導入されることを知見した。このことは特許文献３に示した低温プラズマ浸炭及び浸窒処理においても同様である。なお、このような原子誘起転位が起こるのは、事前のフッ化処理によって被処理材表面の不動態皮膜（クロム水和化合物）が除去されるため、原子状の炭素（窒素）もしくは減圧下の低温プラズマ処理によりイオン状態の炭素（窒素）が、被処理材内部の格子間位置に浸入する際に結晶格子を歪ませたためと考えられる。もちろん、このような浸入型原子誘起転位は、それ自体が、すぐに被処理材に不具合を生じさせるものではないものの、あくまでも歪の一種であり、できれば存在しない方が良いと考えられているものである。その意味では、この浸入型原子誘起転位は特許文献１、２における技術上の不具合とも言えるかも知れないが、本出願人は、更なる技術的改良を行うことにより、このような転位を被処理材の性能向上に生かす手法を見出し、本発明に至ったものである。
特開平３−４４４５７号公報 特開平８−１５８０３５号公報 特開２００５−２７２９７８号公報 In other words, the present applicant has diffused and penetrated carbon atoms (or nitrogen atoms) in a non-equilibrium and supersaturated state, for example, as shown in FIG. It was found that intrusion-type atom-induced dislocations at the nano-dimensional level (several nanometers to several hundred nanometers) were introduced into the crystal grains. The same applies to the low temperature plasma carburizing and nitriding treatment disclosed in Patent Document 3. This kind of atom-induced dislocation occurs because the passive film (chromium hydrated compound) on the surface of the material to be treated is removed by the prior fluorination treatment. This is probably because carbon (nitrogen) in an ionic state has distorted the crystal lattice when entering the interstitial position inside the material to be processed by the low temperature plasma treatment. Of course, such an intrusion-type atom-induced dislocation itself does not immediately cause a defect in the material to be treated, but it is only a kind of strain, and it is considered that it should be absent if possible. It is. In that sense, this intrusion-type atom-induced dislocation may be said to be a technical defect in Patent Documents 1 and 2, but the applicant has made such dislocations treated by further technical improvements. The present inventors have found a technique that can be used to improve the performance of a material and have arrived at the present invention.
JP-A-3-44457 Japanese Patent Laid-Open No. 8-158035 JP 2005-272978 A

本発明は、このような背景を認識してなされたものであり、例えばオーステナイト系ステンレス鋼を被処理材とし、このものに施す浸炭または浸窒処理を実用的に、はるかに有用なものとする手法であり、ステンレス鋼に浸炭または浸窒処理を施した際に不可避的に出現する浸入型原子誘起転位を、更なる技術改良によって被処理材の性能向上に生かすようにした新規な表面改質処理方法並びにこの表面改質処理を施した金属部材並びにこの金属部材を適用して構成したＶＧＳタイプターボチャージャにおける排気ガイドアッセンブリに係るものである。   The present invention has been made in view of such a background. For example, austenitic stainless steel is used as a material to be treated, and carburizing or nitrocarburizing treatment applied thereto is practically much more useful. This is a new surface modification that utilizes intrusion-type atom-induced dislocations that appear inevitably when carburizing or nitriding stainless steel is used to improve the performance of treated materials through further technological improvements. The present invention relates to a treatment method, a metal member subjected to the surface modification treatment, and an exhaust guide assembly in a VGS type turbocharger configured by applying the metal member.

すなわち請求項１記載の高温耐久性を高めたナノ表面改質方法は、
少なくともクロムを含有する金属素材を被処理材とし、
この被処理材をフッ素系ガス雰囲気下で加熱保持してフッ化処理を行い、
その後、またはこのフッ化処理中に、処理温度を400 〜600 ℃に設定した低温浸炭処理および／または浸窒処理を施すか、あるいは減圧下の低温プラズマ浸炭処理および／または低温プラズマ浸窒処理を施して、結晶粒内に多発せしめた浸入型原子誘起転位を炭化物または窒化物の生成核とする擬鋭敏化処理を行い、最終的に被処理材の断面表層部に、クロム炭化物またはクロム窒化物を微細且つ均一に出現させて、被処理材の表面硬化とカバリング効果を図り、被処理材の耐高温摩擦摩耗特性を向上させるようにしたことを特徴として成るものである。
ここで「ナノ（表面改質）」、「浸入型原子誘起転位」、「擬鋭敏化」という用語（文言）については、上記〔０００１〕において説明した通りである。また、「カバリング効果」とは、クロム炭化物またはクロム窒化物が被処理材の断面表層部を密に覆うことにより、摺動に際し、摺動面における固溶原子の相互移動を低減して親和性を阻害する効果、すなわち耐高温摩擦摩耗特性を向上させる効果をいうものとする。更に、高温使用中の外部酸素の浸入を阻止する効果も併せ、いうものとする。 That is, the nano-surface modification method with improved high temperature durability according to claim 1,
A metal material containing at least chromium is used as the material to be treated.
This material to be treated is heated and held in a fluorine gas atmosphere to perform fluorination treatment,
After or during this fluorination treatment, low-temperature carburization and / or nitrocarburization with a treatment temperature set to 400 to 600 ° C. is performed, or low-temperature plasma carburization and / or low-temperature plasma nitridation under reduced pressure. Applied, and pseudo-sensitization treatment using the intrusion-type atom-induced dislocations frequently generated in the crystal grains as carbide or nitride formation nuclei, and finally the chromium carbide or chromium nitride on the cross-sectional surface layer of the material to be treated Is characterized in that the surface treatment of the material to be treated and the covering effect are improved by finely and uniformly appearing to improve the high temperature friction and wear resistance of the material to be treated.
Here, the terms (words) of “nano (surface modification)”, “intrusion-type atom-induced dislocation”, and “pseudo-sensitization” are as described in [0001] above. “Covering effect” means that chromium carbide or chromium nitride covers the cross-sectional surface layer of the material to be treated to reduce the mutual movement of solid solution atoms on the sliding surface during sliding. That is, the effect of improving the high temperature friction and wear resistance. Furthermore, the effect of preventing the entry of external oxygen during high temperature use is also referred to.

また請求項２記載の高温耐久性を高めたナノ表面改質方法は、前記請求項１記載の要件に加え、
前記結晶粒内に多発せしめる浸入型原子誘起転位は、10 8 〜1015/cm2の転位密度で生じさせるものであり、
また前記擬鋭敏化処理を被処理材に施すにあたっては、処理温度を550 〜850 ℃に設定するようにしたことを特徴として成るものである。
ここで「転位密度」とは、結晶の単位体積中に含まれる転位線の長さの総和、または結晶の切断面の単位面積を貫く転位線の数である。 Further, the nano-surface modification method with improved high-temperature durability according to claim 2, in addition to the requirements of claim 1 ,
Interstitial atoms induced dislocations allowed to multiple prior Symbol crystal grains, which causes in the dislocation density of 10 8 ~10 15 / cm 2,
Further, when performing the pseudo-sensitization treatment on the material to be treated, the treatment temperature is set to 550 to 850 ° C.
Here, the “dislocation density” is the total length of dislocation lines contained in the unit volume of the crystal, or the number of dislocation lines penetrating through the unit area of the cut surface of the crystal.

また請求項３記載の高温耐久性を高めたナノ表面改質方法は、前記請求項１または２記載の要件に加え、
前記擬鋭敏化処理後の被処理材には、擬鋭敏化処理によって生じ得る断面表層部のクロム欠乏層中のクロム量を補填するために、当該欠乏層より内部の被処理材マトリックスから、逆濃度勾配を利用して固溶状態のクロム原子をクロム欠乏層に移動させる逆拡散処理を行い、被処理材の耐高温酸化特性を向上させるようにしたことを特徴として成るものである。
ここで「マトリックス」とは、もともとの被処理材（母材）のことで表面改質が施されていない深部のことである。また「逆濃度勾配」について説明すると、一般の浸炭では、例えば図２（ａ）に示すように、被処理材の板厚断面内で表層部分の元素濃度が高く、板厚内部に向かって濃度が低下するものであるが、本願のクロム欠乏層を含むクロム濃度は、図２（ｂ）に示すように断面表層に向かって低下するものであり、本願では、このクロム濃度変化を「逆濃度勾配」と称している。また「逆拡散」とは、このような逆濃度勾配に起因する元素の固体拡散を称するものである。 In addition to the requirement of claim 1 or 2, the nano-surface modification method with improved high temperature durability according to claim 3,
The擬鋭The Satoshika after treatment of the material to be treated,擬鋭Satoshika to compensate the chromium of chromium-depleted layer in the cross section surface portion which may occur I by the process, the processed material matrix inside than the depletion layer From the above, it is characterized by performing reverse diffusion treatment to move chromium atoms in a solid solution state to the chromium-deficient layer using a reverse concentration gradient to improve the high temperature oxidation resistance of the material to be treated. .
Here, the “matrix” refers to the original material to be treated (base material) that is not deeply surface-modified. Further, the “reverse concentration gradient” will be described. In general carburization, as shown in FIG. 2A, for example, the element concentration in the surface layer portion is high within the plate thickness section of the material to be processed, and the concentration increases toward the inside of the plate thickness. However, the chromium concentration including the chromium-deficient layer of the present application decreases toward the cross-sectional surface layer as shown in FIG. 2 (b). It is called “gradient”. “Reverse diffusion” refers to solid diffusion of elements caused by such a reverse concentration gradient.

また請求項４記載の高温耐久性を高めたナノ表面改質方法は、前記請求項３記載の要件に加え、
前記逆拡散処理を被処理材に施すにあたっては、処理温度を850 〜950 ℃に設定するようにしたことを特徴として成るものである。 In addition to the requirement of claim 3, the nano-surface modification method with improved high temperature durability according to claim 4,
In performing the reverse diffusion treatment on the material to be treated, the treatment temperature is set to 85 0 to 950 ° C.

また請求項５記載の高温耐久性を高めたナノ表面改質方法は、前記請求項１または２記載の要件に加え、
前記擬鋭敏化処理後の被処理材には、レアアースメタル元素を導入する添加処理を行い、擬鋭敏化処理によって生じ得るクロム欠乏層の存在に基づく耐高温酸化特性の劣化を回復させるようにしたことを特徴として成るものである。 In addition to the requirement of claim 1 or 2, the nano-surface modification method with improved high temperature durability according to claim 5,
The material to be treated after the pseudo-sensitization treatment is subjected to an addition treatment for introducing a rare earth metal element so as to recover the deterioration of the high-temperature oxidation resistance due to the presence of a chromium-deficient layer that can be caused by the pseudo-sensitization treatment. It is characterized by this.

また請求項６記載の高温耐久性を高めたナノ表面改質方法は、前記請求項５記載の要件に加え、
前記被処理材に導入するレアアースメタル元素の添加量は、0.01〜0.5 ％であることを特徴として成るものである。 Further, the nano-surface modification method with improved high temperature durability according to claim 6, in addition to the requirement according to claim 5,
The addition amount of the rare earth metal element to be introduced into the material to be treated are those comprising as characterized by a 0.01 to 0.5%.

また請求項７記載の高温耐久性を高めたナノ表面改質方法は、前記請求項１、２、３、４、５または６記載の要件に加え、
前記被処理材には、事前に塑性加工を施し、塑性加工転位を導入してから、順次以降の処理を行うようにしたことを特徴として成るものである。
ここで「塑性加工転位」とは、弾性域を越えた外力による塑性加工域における塑性変形に伴って生じる結晶群のずれ（すべり）、すなわち線欠陥のことである。 In addition to the requirement of claim 1, 2, 3, 4, 5 or 6, nano-surface modification method with improved high temperature durability according to claim 7,
The material to be treated is plastically processed in advance, and plastic processing dislocations are introduced, and then subsequent processing is sequentially performed.
Here, the “plastic working dislocation” refers to a crystal group shift (slip) caused by plastic deformation in the plastic working region due to an external force exceeding the elastic region, that is, a line defect.

また請求項８記載の高温耐久性を高めたナノ表面改質方法は、前記請求項７記載の要件に加え、
前記塑性加工転位は、相当真歪εが0.1 〜εu （εu ；相当均一真歪）で被処理材に導入されることを特徴として成るものである。 In addition to the requirement of claim 7, the nano-surface modification method with improved high temperature durability according to claim 8,
The plastic working dislocations equivalent true strain epsilon is 0. 1 ~ε u; those made as a feature to be introduced into the material to be treated with (epsilon u corresponding uniform true strain).

また請求項９記載の高温耐久性を高めたナノ表面改質方法は、前記請求項１、２、３、４、５、６、７または８記載の要件に加え、
前記被処理材には、低温浸炭処理と浸窒処理との双方を施すことを特徴として成るものである。 Further, the nano-surface modification method with improved high-temperature durability according to claim 9 is in addition to the requirement according to claim 1, 2, 3, 4, 5, 6, 7 or 8.
The material to be treated is subjected to both low-temperature carburizing treatment and nitriding treatment.

また請求項１０記載の高温耐久性を高めたナノ表面改質方法は、前記請求項１、２、３、４、５、６、７、８または９記載の要件に加え、
前記被処理材は、
Ｃ：0.02〜0.07 mass ％、Si：0.2 〜1.7 mass％、Mn：5.0mass ％以下、Ni：12.0〜15.0 mass ％、Cr：22.0〜25.0 mass ％、Cu：0.5 〜4.5 mass％、Ｎ：0.05〜0.17 mass ％、且つ、Ca、REM のうちの１種または２種を0.0005〜0.05mass％含有し、残部がFe及び不可避的不純物から成り、下記(1) 式で定義されるNi当量が30.0以上、下記(2) 式で定義されるδcal が0.5 〜8.0 、下記(3) 式で定義されるHvが 120〜160 となるオーステナイト系耐熱素材が適用されることを特徴として成るものである。
記
Ni当量＝Ni＋0.65Cr＋1.05Mn＋0.35Si＋0.6Cu ＋25.2Ｃ＋12.6Ｎ …(1)
δcal ＝3.2 (1.5Si＋Cr) −2.5(30Ｃ＋30Ｎ＋Ni＋0.5Mn ＋0.3Cu)−24.7 …(2)
Hv ＝87Ｃ＋ 2Si−1.2Mn −6.7Ni ＋2.7Cr −2.6Cu ＋690 Ｎ＋88 …(3) In addition to the requirement of claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, the nano-surface modification method with improved high temperature durability according to claim 10,
The material to be treated is
C: 0.02 to 0.07 mass%, Si: 0.2 to 1.7 mass%, Mn: 5.0 mass% or less, Ni: 12.0 to 15.0 mass%, Cr: 22.0 to 25.0 mass%, Cu: 0.5 to 4.5 mass%, N: 0.05 ~ 0.17 mass%, and one or two of Ca and REM are contained in 0.0005 to 0.05 mass%, the balance consists of Fe and inevitable impurities, and the Ni equivalent defined by the following formula (1) is 30.0 As described above, an austenitic heat-resistant material having Δcal defined by the following formula (2) of 0.5 to 8.0 and Hv defined by the following formula (3) of 120 to 160 is applied.
Record
Ni equivalent = Ni + 0.65Cr + 1.05Mn + 0.35Si + 0.6Cu + 25.2C + 12.6N (1)
δcal = 3.2 (1.5Si + Cr) -2.5 (30C + 30N + Ni + 0.5Mn + 0.3Cu) -24.7… (2)
Hv = 87C + 2Si-1.2Mn-6.7Ni + 2.7Cr-2.6Cu + 690 N + 88 (3)

また請求項１１記載のナノ表面改質が施された金属部材は、
金属部材の表面に表面改質処理が施され、この処理によって部材の高温耐久性を向上させた金属部材であって、この部材には前記請求項１、２、３、４、５、６、７、８、９または１０記載のナノ表面改質方法が施されて成ることを特徴として成るものである。 Further, the metal member subjected to nano-surface modification according to claim 11 is
Table Men'aratameshitsu treatment to the surface of the metal member is subjected to a metal member having improved high-temperature durability of the member by the process, the claims 1,2,3,4,5,6 This member , 7, 8, 9 or 10 is applied to the nano-surface modification method.

また請求項１２記載の、ＶＧＳタイプターボチャージャにおける排気ガイドアッセンブリは、
排気タービンの外周位置に、複数の可変翼が回動自在に設けられ、
エンジンから排出された比較的少ない排気ガスを、この可変翼によって適宜絞り込み、排気ガスの速度を増幅させ、排気ガスのエネルギで排気タービンを回し、排気タービンに直結されたコンプレッサで自然吸気以上の空気をエンジンに送り込み、低速回転時であってもエンジンが高出力を発揮できるようにしたＶＧＳタイプターボチャージャの排気ガイドアッセンブリにおいて、
この排気ガイドアッセンブリの構成部材には、前記請求項１１記載の金属部材が適用されて成るものであり、ナノ表面改質の際には事前に適宜の形状に塑性加工されて成ることを特徴として成るものである。 The exhaust guide assembly in the VGS type turbocharger according to claim 12 is:
A plurality of variable blades are rotatably provided at the outer peripheral position of the exhaust turbine,
A relatively small amount of exhaust gas discharged from the engine is appropriately throttled by the variable blades, the speed of the exhaust gas is amplified, the exhaust turbine is rotated by the energy of the exhaust gas, and the air directly above the natural intake air by the compressor directly connected to the exhaust turbine In the exhaust guide assembly of the VGS type turbocharger that allows the engine to exhibit high output even at low speed rotation,
The constituent member of the exhaust guide assembly is formed by applying the metal member according to claim 11 and is plastically processed into an appropriate shape in advance at the time of nano surface modification. It consists of.

これら各請求項記載の発明の構成を手段として前記課題の解決が図られる。
すなわち請求項１または２記載の発明によれば、まず被処理材に上記特許文献１、２の処理、つまり事前フッ化処理後、400 〜600 ℃、一例として500 ℃程度の低温浸炭または浸窒処理のうち、少なくとも一方の処理を施すと、炭素または窒素が非平衡且つ過飽和に断面表層部位（例えば30μｍ程度）の結晶格子間に浸入して濃度勾配を生じる。それに応じて、表面硬化が起こるから、ある程度の高温耐久性を発揮する。そして、難浸炭・浸窒材であるオーステナイト系ステンレス鋼で低温処理によって材料の寸法変化を回避しつつ、浸炭・浸窒を可能にした点で意義がある。特許文献３の低温プラズマ浸炭または浸窒も同様である。しかしながら、長時間熱サイクル高温耐久性に対する要求を満たすには甚だ不十分である。 The above-described problems can be solved by using the configuration of the invention described in each of the claims.
That is, according to the first or second aspect of the invention, first, after the treatment of the above-mentioned Patent Documents 1 and 2, that is, pre-fluorination treatment, 400 to 600 ° C., for example, low temperature carburizing or nitriding at about 500 ° C. When at least one of the treatments is performed, carbon or nitrogen infiltrates between crystal lattices in a cross-sectional surface layer portion (for example, about 30 μm) in a non-equilibrium and supersaturated state to generate a concentration gradient. Correspondingly, surface hardening occurs, so that a certain degree of high temperature durability is exhibited. And, it is significant in that carburizing and nitriding can be performed while avoiding dimensional change of the material by low temperature treatment with austenitic stainless steel which is a hard carburizing and nitriding material. The same applies to low-temperature plasma carburizing or nitriding in Patent Document 3. However, it is far from sufficient to meet the demand for long-term heat cycle high temperature durability.

ここで、あらかじめ推測していた現象であるが、これらの処理法遂行過程で、ナノ寸法レベルの転位が均一・高密度に結晶粒内に導入・温存されていることを透過電子顕微鏡観察によって現認した（図４）。これを上記〔０００１〕で説明したように浸入型原子誘起転位と称する。図示のごとく、ここで知見された浸入型原子誘起転位の長さ・間隔は、それぞれ100 ナノメートル程度、約数10ナノメートルである。なお、転位密度をρ、転位の平均長さと間隔をそれぞれL ave 、d ave とすると、Ａを定数として、ρ≒Ａ（L ave ・d ave ）-1と表せる。また本来的にｆを関数として、ρ＝ｆ（ＣorＮ、Ｔ、ｔ）の関係がある（Ｃ，Ｎ：濃度（質量％）、Ｔ：温度、ｔ：時間）。この知見事実は、上記〔０００４〕で述べたように、本来存在しない方が良いと考えられるものであるが、嘱望されている被処理材の耐高温摩擦摩耗特性及び耐高温酸化特性の向上に利用できないか鋭意研究した結果、一般には忌避すべき結晶粒界の鋭敏化現象（クロム炭化物の析出による粒界腐食の発生を生じてしまう）に思いをいたし、これを逆用して、均一・微細に粒内分布する浸入型原子誘起転位を核生成サイトとして、例えばクロム炭化物を表面近傍の浸炭層中の高濃度炭素と、例えばオーステナイト系ステンレス鋼中のクロムとの結合析出を擬鋭敏化処理によって適正な比率で生起せしめ、硬質のクロム炭化物群の存在及び固溶クロム元素の摺動部での相互移動、すなわち親和性を阻害せしめるカバリング効果とによって目標を実現し得ることを実証したのである。すなわち本願のポイントの一つを要約すると、加工転位に比べると浸入型原子誘起転位は、形状寸法的に均一且つ高密度でタングリング（もつれ）が少なく、表面改質層中に存在するから固体内雰囲気が高炭素・窒素環境にあること、等の特徴を有するため、その後の擬鋭敏化によって炭素や窒素の化学量論的比率の高い高融点、高硬度のクロム炭化物、クロム窒化物が適正に均一微細に容易に生じる。しかも改質層中の固溶炭素・窒素原子と原子誘起転位間平均距離が、従来のように母材中の加工転位と炭素・窒素原子との平均距離よりも短く、反応速度論的にも炭化物・窒化物の生成が容易化される。以上が、原理的な本願のポイントであり、これらを基にして擬鋭敏化処理を施すことにより既述のカバリング効果と相まって耐高温摩擦摩耗特性を著しく向上させるのである。その結果、高温耐久性の２大要素といえる耐高温摩擦摩耗特性、耐高温酸化特性（もちろん高温強度、高温組織安定性なども肝要であるが）のうち耐高温摩擦摩耗特性を大きく向上し得る新規なナノ表面改質法（ナノ寸法レベルの該転位の新しい利用法に基づくことによる名称）を提案するものである。 Here, it is a phenomenon that has been presumed in advance, and it was confirmed by observation with a transmission electron microscope that dislocations at the nano-size level were introduced and preserved uniformly and densely in the crystal grains during the process. (FIG. 4). This is called intrusion-type atom-induced dislocation as described in [0001] above. As shown in the figure, the length and interval of the intrusion-type atom-induced dislocation discovered here are about 100 nanometers and about several tens of nanometers, respectively. If the dislocation density is ρ and the average length and interval of dislocations are L ave and d ave , respectively, A can be expressed as ρ≈A (L ave · d ave ) −1 . Further, there is a relation of ρ = f (CorN, T, t) as a function of f (C, N: concentration (mass%), T: temperature, t: time). As described in the above [0004], this knowledge fact is considered to be better when it does not exist, but it is expected to improve the high temperature friction and wear resistance and high temperature oxidation resistance of the material to be treated. As a result of earnest research as to whether or not it can be used, we generally thought of the grain boundary sensitization phenomenon that would be avoided (resulting in the occurrence of intergranular corrosion due to the precipitation of chromium carbides). Using nucleation sites with finely distributed intragranular atom-induced dislocations, quasi-sensitization treatment of, for example, chromium carbide with high concentration carbon in the carburized layer near the surface and chromium in austenitic stainless steel, for example. By the presence of hard chromium carbide groups and mutual movement of the solid solution chromium element at the sliding part, that is, the covering effect that inhibits the affinity. It was demonstrated that may represent. That is, to summarize one of the points of the present application, intrusion-type atom-induced dislocations are more uniform in shape and density and less tangled (entangled) than processing dislocations, and are present in the surface modification layer. Due to the features such as the high atmosphere in the high carbon / nitrogen atmosphere, high melting point and high hardness chromium carbide and chromium nitride with high stoichiometric ratio of carbon and nitrogen are appropriate by subsequent pseudo-sensitization. It occurs easily in a uniform and fine manner. Moreover, the average distance between the solid-solution carbon / nitrogen atoms and the atom-induced dislocations in the modified layer is shorter than the average distance between the processed dislocations in the base metal and the carbon / nitrogen atoms as in the past, and the reaction kinetics also Formation of carbide and nitride is facilitated. The above is the point of the present application in principle, and by applying the pseudo-sensitization treatment based on these, the high temperature friction and wear resistance is remarkably improved in combination with the covering effect described above. As a result, high-temperature friction and wear resistance, which is one of the two main factors of high-temperature durability, can be greatly improved among high-temperature friction and wear resistance and high-temperature oxidation characteristics (although high-temperature strength and high-temperature structure stability are of course important). A novel nano-surface modification method (name based on a new use of the dislocation at the nano-dimensional level) is proposed.

かかる効果を現出させるためには、低温浸炭や低温浸窒等の処理温度を、400 〜600 ℃の範囲に設定するものである。その理由は、400 ℃未満では、浸入型原子の浸入・拡散速度が過小となって処理に長時間を要し（非実用的）、また600 ℃を超えると、せっかく導入された浸入型原子誘起転位が過大な熱エネルギのために相当程度消滅してしまい、望ましい転位密度の下限108/cm2 以下となってしまうからである。
また低温浸炭や低温浸窒等によって導入される浸入型原子誘起転位の密度は、108 〜1015/cm2が望ましい。その理由は、108/cm2 未満では、後続の擬鋭敏化処理を行っても核生成サイトが過少のためクロム炭化物／クロム窒化物析出が不十分で耐高温摩擦摩耗特性を必要十分に確保できず、1015/cm2を越えると核生成サイトが過剰となって析出物の適正な小寸法への成長・分布が阻害されるからである。
また擬鋭敏化処理が550 〜850 ℃で実施されるのが望ましい理由は、次の通りである。当該処理温度が550 ℃未満の場合は、該導入転位を核にしたクロム炭化物が、析出条件を充分に満たすことができないため所要の微細炭化物析出を生じ得ないからである。他方、処理温度が850 ℃を越えると、クロムと炭素もしくは窒素の原子間親和力が低下し、折角の導入転位の核生成サイト（機能）が存在しても、やはりクロム化合物の生成が全く不十分となるからである。このように適正領域を見出し、限定条件を付したのであるが、この現象の本質は、遊離クロム、炭素原子（窒素原子）のそれぞれの自由エネルギと、析出化合物の自由エネルギの温度依存性の相違に基づくものである。 To revealing such effects, the treatment temperature of the low temperature carburization and low-temperature immersion窒等are those set in the range of 400 to 600 ° C.. The reason for this is that if the temperature is lower than 400 ° C, the intrusion / diffusion rate of the intrusive atoms is too low and the treatment takes a long time (unpractical). This is because the dislocation disappears to some extent due to excessive thermal energy, and the lower limit of desirable dislocation density is 10 8 / cm 2 or less.
The density of the intrusion-type atom-induced dislocation introduced by low-temperature carburizing or low-temperature nitriding is preferably 10 8 to 10 15 / cm 2 . The reason for this is that if it is less than 10 8 / cm 2 , even if the subsequent pseudo-sensitization treatment is performed, the number of nucleation sites is so small that the precipitation of chromium carbide / chromium nitride is insufficient and the high temperature friction wear resistance is sufficiently and sufficiently secured. This is because if it exceeds 10 15 / cm 2 , nucleation sites become excessive and growth and distribution of precipitates to an appropriate small size are hindered.
The reason why the pseudo-sensitization treatment is preferably performed at 550 to 850 ° C. is as follows. This is because when the treatment temperature is lower than 550 ° C., the chromium carbide having the introduced dislocation as a nucleus cannot sufficiently satisfy the precipitation conditions, so that the required fine carbide precipitation cannot occur. On the other hand, when the processing temperature exceeds 850 ° C, the affinity between chromium and carbon or nitrogen decreases, and even if there is a nucleation site (function) for the introduction dislocation at the corner, the formation of chromium compound is still insufficient. Because it becomes. In this way, we found the appropriate region and attached the limiting conditions. The essence of this phenomenon is the difference between the free energy of free chromium and carbon atom (nitrogen atom) and the temperature dependence of the free energy of the precipitated compound. It is based on.

図４にすでに示したように、「浸入型原子誘起転位」が導入されることは実証された。次に、この転位を核にして擬鋭敏化処理によって微細析出物が生成した証拠を図５、６に示す。図５は、冷陰極電解放射型走査電子顕微鏡（ＦＥ−ＳＥＭ；通常の走査電子顕微鏡(SEM) に比べて焦点深度が極めて大きいのが特徴）による処理層（表面改質層；500 ℃×16時間の低温浸炭→700 ℃×2 時間の擬鋭敏化処理）の断面観察像である（倍率×5,000 ）。明らかに微細析出物が一様に生成していることが判別される。つまり、通常回避しなければならない結晶粒界析出ではなく、結晶粒内析出であるところから、この擬鋭敏化析出は、低温浸炭に際して、導入された転位を核とした析出現象であることが明白であり、原理的推測どおりの結果と言えるものである。この図において、直線状の模様は、もちろん摩耗キズなどではなく、金属の組織の一部であり、おそらく焼鈍双晶だと考えられる。   As already shown in FIG. 4, it has been demonstrated that “intrusive atom-induced dislocations” are introduced. Next, the evidence that fine precipitates are generated by pseudo-sensitization treatment with this dislocation as a nucleus is shown in FIGS. FIG. 5 shows a treatment layer (surface modified layer; 500 ° C. × 16) by a cold cathode electrolytic emission scanning electron microscope (FE-SEM; characterized by a very large depth of focus compared to a normal scanning electron microscope (SEM)). This is a cross-sectional observation image of time low temperature carburization → 700 ° C. × 2 hours pseudo-sensitization treatment (magnification × 5,000). It is clearly determined that fine precipitates are uniformly formed. In other words, it is obvious that this pseudo-sensitized precipitation is a precipitation phenomenon with the introduced dislocations as the core during low-temperature carburization because it is not a grain boundary precipitation, which must normally be avoided, but an intra-grain precipitation. It can be said that the result is in line with the principle assumption. In this figure, the straight line pattern is not part of the scratches of course, but is a part of the metal structure, and is probably an annealing twin.

図６は、図５では形態が必ずしも明確とは言い難い析出物を明確にするためにＦＩＢ（収束イオンビーム）法によって0.1 μｍ以下の表面改質層断面の薄膜サンプルを作成し、透過電子顕微鏡観察した明視野像である（倍率＝×800,000 ）。これから若干アスペクト比（長径と短径の比率）の異なる長楕円もしくは紡錘状形の析出物が生じていることが明らかである。
そして、この析出物について電子線回析・解析及びＥＤＸ（エネルギ分散型Ｘ線回析分光器）定性分析を行った結果（図７）、これらはCr3C2 、Cr7C3 を主体としたクロム炭化物であることが判明した。硬度は、それぞれＨｖ＝1800、1550と大変硬質であり、（後述のごとく）高温における耐摩擦摩耗特性を大幅に改善することが実証されたものである。 In FIG. 6, a thin film sample having a cross section of a surface modification layer of 0.1 μm or less was prepared by FIB (focused ion beam) method in order to clarify precipitates whose form is not necessarily clear in FIG. It is an observed bright field image (magnification = × 800,000). From this, it is clear that long ellipse or spindle-shaped precipitates having slightly different aspect ratios (ratio of major axis to minor axis) are generated.
As a result of electron diffraction / analysis and qualitative analysis of EDX (energy dispersive X-ray diffraction spectrometer) (FIG. 7), these precipitates are mainly composed of Cr 3 C 2 and Cr 7 C 3. Was found to be chromium carbide. The hardness is very hard with Hv = 1800 and 1550, respectively, and it has been demonstrated that the frictional wear resistance characteristics at a high temperature are significantly improved (as described later).

図８に低温浸炭→擬鋭敏化処理後にクロム欠乏層が生じた例を示す。この図は、ＥＰＭＡ（Ｘ線マイクロアナライザー）による材料断面の測定チャートであり、クロム、炭素（及び酸素）の濃度の分布を表している。図から断面表層近傍（斜線を施した部分）でクロム量の減少が見られる。すなわち、擬鋭敏化過程においてクロム炭化物析出によるクロム欠乏層が生じていることを示す。なお、炭素量（＝浸炭による固溶炭素＋クロム炭化物としての炭素量）が、表層付近で濃度勾配を呈しつつ、表層に近いほど濃度が増加していることが分かる（図２参照）。
そして、このクロム欠乏層を補填する（元に戻す）ため、逆拡散処理を行った後のＥＰＭＡチャートを図９に示す。上記の予想の通り、クロム欠乏層は、逆拡散によって修復され、耐高温酸化特性の劣化が、かかる処理によって回復され得ることが示された。なお、炭素量は、固溶炭素の板厚内部への拡散によって、量・濃度勾配ともに図８に比べて小さくなっていることが分かる（以上図２参照）。 FIG. 8 shows an example in which a chromium-deficient layer is formed after low-temperature carburization → pseudo-sensitization treatment. This figure is a measurement chart of the material cross section by EPMA (X-ray microanalyzer), and represents the distribution of the concentration of chromium and carbon (and oxygen). The figure shows a decrease in the chromium content in the vicinity of the cross-sectional surface layer (shaded area). That is, it shows that a chromium-deficient layer is generated due to chromium carbide precipitation in the pseudo-sensitization process. In addition, it turns out that the density | concentration is increasing, so that the carbon amount (= solid solution carbon by carburization + carbon amount as chromium carbide) shows a concentration gradient in the vicinity of the surface layer and is closer to the surface layer (see FIG. 2).
FIG. 9 shows an EPMA chart after the reverse diffusion process is performed to compensate (return to) the chromium-deficient layer. As expected above, it was shown that the chromium deficient layer was repaired by backdiffusion and the degradation of the high temperature oxidation resistance could be recovered by such treatment. It can be seen that the amount of carbon and the concentration gradient are smaller than those in FIG. 8 due to the diffusion of solute carbon into the plate thickness (see FIG. 2 above).

また請求項３または４記載の発明によれば、まず上記低温浸炭もしくは浸窒後の擬鋭敏化処理によって、格段の耐高温摩擦摩耗特性の向上を図れるのであるが、この処理によって例えばオーステナイト系ステンレス鋼の場合、クロム炭化物の結晶粒内析出に伴って、材料所定の固溶クロム（固体内で拡散移動し化合物、特に耐高温酸化特性に寄与するクロム酸化物を形成し得る原子状クロムのこと）が、典型例として浸炭層（例えば30μｍ厚み程度）中で低下するクロム欠乏現象が生じ、耐高温酸化特性が劣化して、実用上、問題が生じることがあり得る。つまり高温耐久性向上の阻害要因となり得るということである。
この現象に対する実用的な対策を鋭意検討した結果、本願請求項３に係る発明に至ったものである。すなわち、請求項３に係る発明では、固溶クロム量は断面表層部に近い程、減少する逆濃度勾配（低温浸炭における固溶炭素量の濃度勾配とは逆になっており、これは表層部に近い程、炭素量が多いので多量のクロム炭化物が生じて所定の固溶クロムがより多く消費されるためである）を利用して、擬鋭敏化後に、高温短時間熱処理を施すことによって、材料の板厚内部から固溶クロムを表層部に向けて拡散移動せしめ、欠乏層を補填して当初の固溶クロム量に戻すというものである。すなわち、熱力学上の生成自由エネルギやエントロピー増大の法則に従って、内方のクロムはランダム化するため表層方向に移動するわけである。 According to the invention described in claim 3 or 4, first, the pseudo-sensitization treatment after low-temperature carburization or nitriding can achieve a marked improvement in high-temperature frictional wear resistance. By this treatment, for example, austenitic stainless steel In the case of steel, as the chromium carbide precipitates in the crystal grains, it is a solid solution chromium (a kind of atomic chromium that can diffuse and move within the solid to form compounds, especially chromium oxides that contribute to high-temperature oxidation resistance). However, as a typical example, a chromium deficiency phenomenon that decreases in a carburized layer (for example, about 30 μm thickness) occurs, and the high-temperature oxidation resistance deteriorates, which may cause problems in practice. In other words, it can be an impediment to improving high temperature durability.
As a result of intensive studies on practical measures against this phenomenon, the present invention according to claim 3 of the present application has been achieved. That is, in the invention according to claim 3, the concentration of solid solution chromium decreases as the cross-sectional surface layer portion is closer to the reverse concentration gradient (the concentration gradient of the solid solution carbon amount in low-temperature carburizing is opposite to the surface layer portion. As the amount of carbon is closer, the larger the amount of carbon, the greater the amount of chromium carbide that is produced and the more the prescribed solute chromium is consumed) The solute chromium is diffused and moved from the thickness of the material toward the surface layer portion, and the deficient layer is compensated to return to the original solute chromium amount. That is, the inner chromium moves in the direction of the surface layer in order to randomize according to the free dynamic energy of generation and the law of increasing entropy.

この際、付言しておきたい点は、以下の２点である。
(1) クロム欠乏層は30μｍ程度であるのに比べ、被処理材（材料）の板厚は耐熱用途では数ｍｍ（＝数1000μｍ）であるから、欠乏層が補填されても材料初期状態の所定クロム濃度の低下は、実質的に無視できること（欠乏層末端より内方のクロム量は、欠乏層に対して圧倒的に多量に存在することを意味している）。
(2) 移動拡散してきた固溶クロムが、断面表層部の浸炭処理で導入された後に擬鋭敏化処理でクロム炭化物にならなかった固溶炭素と結合してクロム炭化物になってしまうのではないかという懸念がある。これに関しては、逆拡散処理が擬鋭敏化条件（温度と時間で決まるＣ字状曲線から成り、この範囲内で擬鋭敏化析出が起こる）を外した高温（短時間）で行うゆえ（850 〜950 ℃、一例として950 ℃×２時間）、かかる懸念は存在しないのである。
なお、逆拡散を行う処理温度として約850 〜950 ℃が好ましいのは、850 ℃未満では拡散が遅く、Cr欠乏層の修復ができず、また950 ℃を超えると、寸法精度の劣化を招くためである。 At this time, the following two points should be added.
(1) The thickness of the material to be treated (material) is several mm (= several thousand μm) for heat-resistant applications compared to the chromium-deficient layer is about 30 μm. The decrease in the predetermined chromium concentration is substantially negligible (meaning that the amount of chromium inward from the end of the deficient layer is overwhelmingly larger than the deficient layer).
(2) The solute chromium that has migrated and diffused does not become chromium carbide by combining with the solute carbon that did not become chromium carbide by pseudo-sensitization treatment after being introduced by carburizing treatment of the cross-section surface layer part. There is a concern. In this regard, the reverse diffusion treatment is performed at a high temperature (short time) excluding the quasi-sensitizing condition (consisting of a C-shaped curve determined by temperature and time, and quasi-sensitizing precipitation occurs within this range) (850 to 950 ° C., for example, 950 ° C. × 2 hours), there is no such concern.
The treatment temperature for reverse diffusion is preferably about 850 to 950 ° C because diffusion is slow at less than 850 ° C and the Cr-deficient layer cannot be repaired, and when it exceeds 950 ° C, dimensional accuracy is degraded. It is.

また請求項５または６記載の発明によれば、上記〔００２４〕、〔００２５〕の擬鋭敏化処理による固溶クロム欠乏層の生成に起因する耐高温酸化特性の劣化に対する二つ目の対応が実用上可能となる。すなわち、クロム欠乏層の存在はそのままにしておいて、被処理材の表面に、例えばランタンやセリウム等のレアアースメタル（希土類元素）を浸透導入させる添加処理をガス雰囲気中で行い、耐高温酸化特性の劣化を回復・向上せしめることである。レアアースメタルを鋼中（材料）に添加したり、場合によって鋼材表面に浸入させて耐高温酸化特性（のみ）を向上させ得ることは従来より知られているが、本願のごとく「寸法変化フリーの低温浸炭→擬鋭敏化処理によるクロム炭化物形成と、それによる耐高温摩擦摩耗特性の向上及び固溶クロム欠乏層の出現による耐高温酸化特性の劣化→レアアースメタルの浸透導入による耐高温酸化特性の回復・向上→高温耐久性の格段の向上」という一連の連続複合技術としてレアアースメタル添加を行った例は従来存在せず、新規な発想に基づく、工業的に実施可能な新技術である（また上記〔００１８〕、〔００１９〕のように転位が析出核サイトになることも既知であるが、高温耐久性向上を意図した一連の複合技術である点で（上述）、新規な発想に基づく工業的に実施可能な新技術であることを付言しておく）。   According to the invention of claim 5 or 6, the second response to the deterioration of the high-temperature oxidation resistance caused by the formation of a solid solution chromium-deficient layer by the pseudo-sensitization treatment of [0024] and [0025] Practically possible. In other words, with the presence of the chromium-deficient layer as it is, an addition treatment for permeating and introducing rare earth metals (rare earth elements) such as lanthanum and cerium into the surface of the material to be treated is performed in a gas atmosphere, and high temperature oxidation resistance It is to recover and improve the deterioration of the. Although it has been known in the past that rare earth metals can be added to steel (materials) or infiltrated into the steel surface in some cases to improve high-temperature oxidation resistance (only), Low-temperature carburization → Chromium carbide formation by pseudo-sensitization treatment, thereby improving high-temperature friction and wear resistance, and deterioration of high-temperature oxidation resistance due to the appearance of a solid solution chromium-deficient layer → Recovery of high-temperature oxidation resistance by infiltration of rare earth metal There has been no example of rare earth metal addition as a series of continuous composite technologies of "improvement → marked improvement in high-temperature durability", and it is a new technology that can be implemented industrially based on a new idea (and above) Although it is known that dislocations become precipitation nucleus sites as in [0018] and [0019], this is a series of composite technologies intended to improve high-temperature durability (described above). Keep additional remark that Do is industrially feasible new technology that is based on the idea).

ここでレアアースメタル添加効果について述べる。表層にレアアースメタルが添加され、且つクロム炭化物と固溶炭素及び固溶クロム欠乏層が併存した状況で、材料が高温酸化雰囲気に晒されると、レアアースメタルは優先的に外部酸素と結合して酸化に対する保護皮膜薄層を形成し、同時にクロム欠乏状態ではあるが、クロム酸化物保護皮膜も若干二次的に形成され、酸化に対して補助的な抵抗を示す。このようにして主にレアアースメタル酸化物が外部酸素の浸入を阻害することによって、耐酸化能が確保・発揮され、同時にクロム炭化物が耐高温摩擦摩耗特性（耐摺動性）を有することと相まって高温耐久性が格段に向上することが見出されたのである（図２参照）。
なお、レアアースメタルの添加量は、効果と経済性を勘案して0.01〜0.5 ％とする。 Here, the effect of rare earth metal addition will be described. If rare earth metal is added to the surface layer and chromium carbide, solute carbon, and solute chromium-deficient layer coexist, and the material is exposed to a high-temperature oxidizing atmosphere, the rare earth metal is preferentially combined with external oxygen and oxidized. At the same time, although a chromium protective layer is formed in a slightly secondary state, a chromium oxide protective coating is also slightly formed, and provides an auxiliary resistance to oxidation. In this way, mainly rare earth metal oxides prevent external oxygen from entering, ensuring and exhibiting oxidation resistance, and at the same time, chromium carbide has high temperature friction and wear resistance (sliding resistance). It has been found that the high temperature durability is remarkably improved (see FIG. 2).
The amount of rare earth metal added is set to 0.01 to 0.5% in consideration of effects and economic efficiency.

また請求項７または８記載の発明によれば、前記被処理材に事前に塑性加工を施し、塑性加工による転位を導入してから順次、請求項１、２、３、４、５または６記載の高温耐久性を高めたナノ表面改質方法を適用し、前記課題の解決を図るものである。
ここで塑性加工とは、弾性変形域を越えた外力が加えられて、マクロ的には永久変形が生じた状態であり、ミクロ的には局所的な結晶格子変形、すなわち転位などの格子欠陥を生ずる加工のことで、その態様はプレス成形、鍛造、造形、圧延、引き抜き・押し出し、切削（機械加工）、ショットピーニング、ワイヤカット、打ち抜き、研削、研摩など広範にわたる。本願では、かかる塑性加工で生じた線状欠陥を塑性加工転位と称しており、特にその中で改質層中の加工転位が、上述した浸入型原子誘起転位と相まって、例えば擬鋭敏化によるクロム炭化物の生成割合を増大せしめ、一層、この炭化物を均一・微細に析出させることを意図したものである。
その理由は、クロム炭化物生成率が増えるほど、硬質層とカバリング効果（上記〔００１９〕が発揮されて耐高温摩擦摩耗特性が向上すること、またより均一・微細に析出すればするほど実際使用時の、特に長時間多数回の熱サイクル下でのクロム炭化物の成長・凝集（一般に「オストワルド成長」と称される）及び解離・再固溶が抑制され、結果として耐高温摩擦摩耗特性が維持されることにある。
かかる効果を現出させるには加工様式に拘らず相当真歪εがε＝0.1 〜εu であることが望ましい。ここにεu は相当均一真歪である。このときの転位密度ρは大略ρ＝108 〜1013/cm2程度である。
なお、重ねて言えば本願は、上記〔００１９〕に記したように浸入型原子誘起転位の存在を前提としており、加工転位との併存によって望ましい炭化物・窒化物の析出がなされるものであり、既知の、ステンレス鋼の鋭敏化の軽減を意図して応用されることのある加工転位のみによる炭化物・窒化物の析出処理とは一線を画すものであることを強調しておきたい。 According to the invention of claim 7 or 8, the plastic material is preliminarily subjected to plastic working, and dislocations by plastic working are introduced, and then, sequentially from claim 1, 2, 3, 4, 5 or 6. The above-mentioned problems are solved by applying a nano-surface modification method with improved high-temperature durability.
Here, the plastic working is a state in which an external force exceeding the elastic deformation region is applied and macroscopic permanent deformation has occurred, and microscopically, local crystal lattice deformation, that is, lattice defects such as dislocations are eliminated. In terms of the processing that occurs, the mode is wide, including press molding, forging, shaping, rolling, drawing / extruding, cutting (machining), shot peening, wire cutting, punching, grinding, and polishing. In the present application, linear defects generated by such plastic working are referred to as plastic working dislocations. In particular, the working dislocations in the modified layer are coupled with the above-described intrusion-type atom-induced dislocations, for example, chromium due to pseudo-sensitization. It is intended to increase the generation rate of carbides and to further precipitate the carbides uniformly and finely.
The reason for this is that the higher the chromium carbide production rate, the harder layer and covering effect (the above [0019] is exhibited and the high temperature friction and wear resistance is improved, and the more uniform and finer the precipitation is, the more the actual use time is. In particular, the growth and aggregation of chromium carbide (generally referred to as “Ostwald growth”) and dissociation / re-solidification under a large number of thermal cycles for a long time are suppressed, and as a result, the high temperature friction and wear resistance is maintained. There is to be.
It is desirable true strain epsilon equivalent regardless to the processing style to be revealing such an effect is ε = 0.1 ~ε u. Here, ε u is a substantially uniform true strain. At this time, the dislocation density ρ is approximately about ρ = 10 8 to 10 13 / cm 2 .
In addition, in other words, the present application is based on the premise of the presence of intrusion-type atom-induced dislocations as described in the above [0019], and desirable carbide / nitride is precipitated by coexisting with the processing dislocations. It should be emphasized that the known carbide / nitride precipitation treatment only by working dislocations, which may be applied with the intention of reducing the sensitization of stainless steel, is in a line.

ここで以下の事柄を付言しておく。
(1) 低温浸炭に際して過剰・不均一な塑性加工転位の存在は、マイナス要因となりかねないことであり、場合によって事前フッ化処理に先行して適切な熱処理を行う必要があること
(2) 上記のごとき塑性加工には種々の変形様式があり、多くの場合、金属素材（被処理材）から加工部品形状が規定されているのが通例であるから、塑性加工転位の処理性及び処理後特性（高温耐久性）発現・向上に対しては塑性加工様式とその条件及び低温浸炭前処理条件を十分考慮すべきこと（各加工様式における真歪（相当真歪εではない）をそれぞれ考慮した場合）
(3) 塑性加工転位もやはりナノ寸法レベルに属するところから、本願請求項７、８に係る発明もナノ表面改質と言えること Here are some additional notes:
(1) Excessive and non-uniform plastic working dislocations during low-temperature carburization can be a negative factor, and in some cases, appropriate heat treatment must be performed prior to pre-fluorination treatment.
(2) There are various deformation modes for plastic working as described above, and in many cases, it is customary that the shape of the machined part is defined from the metal material (material to be treated). In addition, for the development and improvement of post-treatment characteristics (high temperature durability), the plastic working mode and its conditions and the low-temperature carburizing pre-treatment conditions should be fully considered (true strain (not equivalent true strain ε) in each processing mode) When considering each)
(3) Since the plastic working dislocations also belong to the nano dimension level, the inventions according to claims 7 and 8 of the present application can also be said to be nano surface modification.

また請求項９記載の発明によれば、被処理材に低温浸炭と浸窒処理との双方を施すため、以下のような効果を奏する。なお、「双方の処理を施す」とは、以下の三つのケースを包含するものである。
(1) 浸炭と浸窒とを同時に行う場合
(2) 浸炭→浸窒処理（浸炭処理を行った後に浸窒処理）を行う場合
(3) 浸窒→浸炭処理（浸窒処理を行った後に浸炭処理）を行う場合
まず(1) の同時処理は、部品または製品の適用使用温度範囲が広い場合（例えば650 〜1050℃）に効果的である。その理由は、低温域（例えば650 〜850 ℃）で、クロム炭化物が比較的安定的に機能を発揮するため、浸炭処理の効果が得られ易く、高温域（例えば850 〜1050℃）で、クロム窒化物が比較的安定的に機能を発揮するため、浸窒処理の効果が得られ易いからである。
また(2) の浸炭→浸窒処理は、適用使用温度範囲が高温域の場合に効果的である（例えば850 〜1050℃）。その理由は、高温域では、相対的に、より断面表層部位に存在するクロム窒化物が比較的安定的に機能を発揮するために、この処理の効果が得られ易いからである。
更に(3) の浸窒→浸炭処理は、適用使用温度範囲が低温域の場合に効果的である（例えば650 〜850 ℃）。その理由は、低温域では、相対的に、より断面表層部位に存在するクロム炭化物が比較的安定的に機能を発揮するために、この処理の効果が得られ易いからである。
このように、いずれの場合も、浸炭、浸窒の複合処理の効果は、単独処理に比較して効果の程度はより優れ、安定的且つ適用温度依存性が緩和される。つまり許容条件が広がるという効果が期待できるが、生産性・経済性を考えると、複合・単独の各処理を適用ケースに応じて選択するのが望ましい。 According to the ninth aspect of the invention, since both the low-temperature carburizing and the nitriding treatment are performed on the material to be treated, the following effects are obtained. Note that “performing both processes” includes the following three cases.
(1) When carburizing and nitriding are performed simultaneously
(2) Carburization → Nitrogen treatment (Nitrogen treatment after carburization)
(3) When carburizing → carburizing (carburizing after carburizing) First, the simultaneous processing in (1) is performed when the application temperature range of parts or products is wide (eg 650 to 1050 ° C). It is effective. The reason is that chromium carbide exhibits a relatively stable function in a low temperature range (for example, 650 to 850 ° C.), so that the effect of carburizing treatment can be easily obtained, and chromium can be obtained in a high temperature range (for example, 850 to 1050 ° C.). This is because the effect of the nitriding treatment is easily obtained because the nitride exhibits the function relatively stably.
In addition, the carburization → nitrogenation treatment (2) is effective when the application operating temperature range is a high temperature range (for example, 850 to 1050 ° C.). The reason is that the effect of this treatment is easily obtained because the chromium nitride present in the surface layer portion of the cross section exhibits a relatively stable function in the high temperature range.
Furthermore, the nitriding → carburizing treatment (3) is effective when the application temperature range is low (for example, 650 to 850 ° C.). The reason is that the effect of this treatment is easily obtained because the chromium carbide present in the surface layer portion of the cross section exhibits a relatively stable function in the low temperature range.
As described above, in any case, the effect of the combined treatment of carburizing and nitriding is superior to that of the single treatment, and the effect is stable and the dependence on the applied temperature is relaxed. In other words, the effect of widening the allowable conditions can be expected, but considering the productivity and economy, it is desirable to select the combined processing and the single processing according to the application case.

また請求項１０記載の発明によれば、被処理材を特定したため、以下のような効果を奏する。なお、請求項１０で特定した被処理材は、本出願人が既に特許出願に及んでいる材料（特願２００５−２１５６３２「高温耐久性に優れるオーステナイト系耐熱材料、耐熱部品及びエンジン周り用耐熱部品」）であり、以下、これを本明細書では「新材料」と称する。
(1) 新材料に本願のナノ表面改質処理を施す場合、例えばSUS310S 級の完全オーステナイト系ステンレス鋼の場合に比べてニッケル量を大幅に低減しているためフッ化処理による不動態皮膜除去性に優れるので（しかし組成バランスを考慮した材料設計によってやはり完全オーステナイト系ステンレス鋼である）、低温浸炭もしくは浸窒が容易であり、これは工業化の上で大きなメリットとなる。
(2) 過大な高温延性が制約され適度な値（例えば850 ℃で30〜40％の伸び）を有するために、多数回の熱サイクル使用に際してもナノ表面改質層に過大な変形・応力を与えずに済むから、改質層の品質が長時間安定に保たれる。
(3) カルシウム及び銅添加によって特に機械的加工性（切削性）に優れるので、低温浸炭・窒化に際して事前処理の負荷が少なく、工業的に作業がし易く、作業能率も上がる。
(4) 新材料は、ナノ表面改質処理後の表面平滑度が良好なのでアッセンブリし易く、且つ耐高温摩擦摩耗特性（特に凝着摩耗）も従来鋼（上記SUS310S ）より良好である。
(5) 材料の耐高温摩擦摩耗特性が良好な反面、高温（水蒸気）酸化に対して、例えばSUS310S に比較しても遜色ないので、ナノ表面改質が施された場合の改質層のマトリックス部分（及び改質層境界より板厚方向内部のマトリックスも）の高温耐久に対する抵抗力も充分である。
(6) Ni当量、δcal 、Hvに対する適正化制御がなされているので、高温耐久性の重要因子である高温組織安定性に優れている（上記SUS310S と比較した熱サイクルによる鋭敏化現象（耐食性、耐脆化特性を劣化させる）及びシグマ相生成現象（材料脆化の原因となる）に関わる組織安定性の例を図１０、１１に示す。組織安定性は経済的にも有利な新材料の方がSUS310S よりも優れていることが認識される。つまり、新材料に本願の表面改質を施すことにより、従来にない新技術を提供することができる）。また、特に完全オーステナイト鋼に通弊の難製造性が回避できるので量産性・経済性に優れ、加工性も高窒素の弊害（窒素は高温強度維持のためと完全オーステナイト化のために高値としている）は、ニッケルの低減と銅、カルシウム（もしくはレアアースメタル）の添加と、結晶粒度制御によって回避されており、且つ本質的に優れた耐高温摩耗特性を有するから、ナノ表面改質処理とのコンビネーションによって、従来にない新規な耐熱部材の製造が可能となる。 According to the invention described in claim 10, since the material to be treated is specified, the following effects can be obtained. The material to be treated specified in claim 10 is a material already filed by the present applicant (Japanese Patent Application No. 2005-215632 “Austenitic heat-resistant material excellent in high-temperature durability, heat-resistant component, and engine-resistant heat-resistant component). This is hereinafter referred to as “new material”.
(1) When the new material is subjected to the nano-surface modification treatment of the present application, the nickel content is significantly reduced compared to, for example, SUS310S grade fully austenitic stainless steel. (Although it is still a complete austenitic stainless steel due to the material design considering the composition balance), low-temperature carburizing or nitriding is easy, which is a great merit for industrialization.
(2) Excessive high temperature ductility is constrained and has an appropriate value (e.g., 30 to 40% elongation at 850 ° C). Since it does not need to be given, the quality of the modified layer is kept stable for a long time.
(3) Addition of calcium and copper is particularly excellent in mechanical workability (cutting property), so there is less pre-treatment load at low temperature carburizing / nitriding, industrial work is easy, and work efficiency is improved.
(4) The new material has good surface smoothness after nano-surface modification treatment, so it is easy to assemble, and the high-temperature friction and wear resistance (particularly adhesive wear) is also better than the conventional steel (SUS310S above).
(5) The high temperature friction and wear resistance of the material is good, but the high temperature (steam) oxidation is comparable to that of, for example, SUS310S, so the matrix of the modified layer when subjected to nano surface modification The resistance to high temperature durability of the part (and the matrix inside the thickness direction from the boundary of the modified layer) is also sufficient.
(6) Since optimization control for Ni equivalent, δcal and Hv is performed, it is excellent in high-temperature structure stability, which is an important factor for high-temperature durability (sensitization phenomenon (corrosion resistance, 10 and 11 show examples of structure stability related to sigma phase formation phenomenon (which causes material embrittlement), which deteriorates the resistance to embrittlement, and is an economically advantageous new material. It is recognized that SUS310S is superior to SUS310S, that is, by applying the surface modification of this application to a new material, an unprecedented new technology can be provided). In addition, it is possible to avoid the difficult productivity, which is especially true for fully austenitic steels, so it is excellent in mass production and economy, and the workability is also adversely affected by high nitrogen (nitrogen is high for maintaining high-temperature strength and for complete austenite. ) Is avoided by the reduction of nickel, addition of copper and calcium (or rare earth metal), grain size control, and essentially excellent high temperature wear resistance, so it is combined with nano surface modification treatment Thus, it becomes possible to manufacture a new heat-resistant member that has not existed before.

また請求項１１記載の発明によれば、当該金属部材には上述したナノ表面改質処理が施されるため、上記〔０００３〕の課題が解決でき、上記〔００１８〕〜〔００３１〕で述べた性能を有する種々の工業材料・部品・製品が提供される。なお、金属部材には、上記〔００３１〕の新材料から成るものや、適宜の塑性加工を施した部材等が含まれ、また用途としては一般耐熱用途に広く適用され得る。   Further, according to the invention described in claim 11, since the metal surface is subjected to the above-described nano-surface modification treatment, the above-mentioned problem [0003] can be solved, as described in the above [0018] to [0031]. Various industrial materials, parts, and products with performance are provided. Metal members include those made of the new material [0031] described above, members subjected to appropriate plastic working, and the like, and can be widely applied to general heat resistance applications.

また請求項１２記載の発明によれば、ＶＧＳタイプターボチャージャの排気ガイドアッセンブリは、構成部品として前記請求項１１記載の金属部材が適用されるものであり、この種のターボチャージャは、高温・排ガス雰囲気下で使用され、また繰り返し熱負荷を受けるため、高温耐久性に優れた排気ガイドアッセンブリひいてはＶＧＳタイプターボチャージャ（ＶＧＳユニット）を量産レベルで現実に提供し得る。   According to the invention described in claim 12, the exhaust gas guide assembly of the VGS type turbocharger is applied with the metal member described in claim 11 as a constituent part. Since it is used in an atmosphere and repeatedly subjected to a heat load, an exhaust guide assembly excellent in high temperature durability, and thus a VGS type turbocharger (VGS unit) can be actually provided at a mass production level.

本発明を実施するための最良の形態は、以下の実施例に述べるものをその一つとするとともに、更にその技術思想内において改良し得る種々の手法を含むものである。   BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention includes one described in the following examples, and further includes various methods that can be improved within the technical idea.

実施例の説明に先立ち、本発明の技術思想（骨子）をまとめておく。まず、本発明の趣旨は、高温耐久性が格段に優れた新規な発想に基づく表面改質方法と、この方法によって高温耐久性に優れた金属部材を得ることであり、更に、これらを現実に実施できる手段と支配メカニズムを明示するものである。もちろん、工業化に際しては、作業性・生産／量産性・経済性に優れていなければならない。本出願人は、これらの事項に基づき、上記特許文献１、２及び特願２００５−２１５６３２等において技術的改良を行い、新しい発想・着眼によって本手法を実現し、本発明に至ったものである。   Prior to the description of the embodiments, the technical idea (main point) of the present invention will be summarized. First, the gist of the present invention is to obtain a surface modification method based on a novel idea that is extremely excellent in high-temperature durability, and to obtain a metal member that is excellent in high-temperature durability by this method. It specifies the means that can be implemented and the control mechanism. Of course, in industrialization, it must be excellent in workability, production / mass productivity and economy. Based on these matters, the present applicant made technical improvements in the above-mentioned Patent Documents 1 and 2 and Japanese Patent Application No. 2005-215632, etc., and realized the present technique by new ideas and attentions, resulting in the present invention. .

以下、本発明のナノ表面改質方法について説明する。図１は、ナノ表面改質方法の工程の一例を模式的・概念的に示した図であり、横軸が処理の経過（時間の経過）を示し、縦軸が温度を示している。まず被処理材としては、焼なまし状態の金属素材が適用され、より好ましくは本願請求項１０に記載した新材料（完全オーステナイトステンレス鋼）が適用される。なお、被処理材には、そのままナノ表面改質処理が施されることもあるが、一般的には塑性加工が施され、あらかじめ被処理材を何らかの形状に変形、凍結することが多い。また、塑性加工に際しては、被処理材に塑性加工転位が導入され、適宜、後述するナノ表面改質に生かされる。
なお、塑性加工によって被処理材に導入される転位（塑性加工転位）は、約108 〜1013/cm2の転位密度となる。 Hereinafter, the nano surface modification method of the present invention will be described. FIG. 1 is a diagram schematically and conceptually showing an example of the steps of the nano-surface modification method, in which the horizontal axis indicates the progress of processing (elapse of time), and the vertical axis indicates the temperature. First, as the material to be treated, an annealed metal material is applied, and more preferably, the new material (completely austenitic stainless steel) described in claim 10 of the present application is applied. The material to be treated may be subjected to a nano-surface modification treatment as it is, but generally is subjected to plastic working, and the material to be treated is often deformed and frozen in advance in some shape. Further, in the plastic working, plastic working dislocations are introduced into the material to be processed, and are appropriately utilized for nano surface modification described later.
The dislocation (plastic working dislocation) introduced into the material to be processed by plastic working has a dislocation density of about 10 8 to 10 13 / cm 2 .

次いで、被処理材には一例として低温浸炭処理が施される。具体的には上記塑性加工状態（つまり形状、加工度、加工様式）によって、特に浸炭すべき断面表層近傍（例えば表面から30μｍ程度）の塑性加工転位状況が低温浸炭の難易度に影響することが多いところから、多くの場合、軽度の短時間予備熱処理を行う。そしてＮＦ3 ガスなどで事前フッ化処理を行って不動態皮膜薄層を除去した後、ＣＯ、ＣＯ2 、Ｈ2 、Ｎ2 などの混合ガス雰囲気中で低温浸炭（400 〜600 ℃、一例として500 ℃）を行い、炭素を非平衡過飽和に導入する。この際、上記〔０００４〕で述べたように、浸入型原子誘起転位が生成し、炭素の（正）濃度勾配が生ずる（図８参照）。
なお、低温浸炭や低温浸窒等の処理の際に、被処理材に生成される転位（浸入型原子誘起転位）は、約108 〜1015/cm2の転位密度となる。 Next, the material to be treated is subjected to a low-temperature carburizing treatment as an example. Specifically, depending on the plastic working state (that is, shape, working degree, working style), the plastic working dislocation situation in the vicinity of the cross-sectional surface layer to be carburized (for example, about 30 μm from the surface) may affect the difficulty of low-temperature carburizing. In many cases, mild pre-heat treatment is often performed. Then, after pre-fluorination treatment with NF 3 gas or the like to remove the passive film thin layer, low-temperature carburization (400 to 600 ° C., one example) in a mixed gas atmosphere of CO, CO 2 , H 2 , N 2, etc. And introduce carbon into the nonequilibrium supersaturation. At this time, as described in [0004] above, intrusion-type atom-induced dislocations are generated, and a (positive) concentration gradient of carbon is generated (see FIG. 8).
Note that dislocations generated in the material to be treated (penetration-type atom-induced dislocations) during the treatment such as low-temperature carburizing and low-temperature nitriding have a dislocation density of about 10 8 to 10 15 / cm 2 .

次いで浸入炭素、浸入型原子誘起転位、塑性加工転位（予備熱処理条件によっては消滅していることもある）、既存の固溶クロム元素の存在などを利用して擬鋭敏化処理を行い（擬鋭敏化Ｃ曲線（図１２に半模式的に示すように擬鋭敏化曲線はＣ型の温度・時間関係で表される。既述の通り、処理温度の上・下限は850 ℃及び550 ℃である）内の例えば700 ℃において）、浸炭領域の材料組織の結晶粒内に適量のクロム炭化物を均一・微細に析出させる。この際に固溶クロム欠乏現象が大なり小なり発生する（クロム元素の逆濃度勾配；図８）。この影響を看過できる場合は、ナノ表面改質は、ここまでの処理で終了する。つまり金属部材（加工部材）としては、ここまでの処理後にアッセンブル・実用に供され、耐高温摩擦摩耗特性が向上した高温耐久能を発揮する。   Next, pseudo-sensitization treatment is performed using the presence of intruded carbon, intrusion-type atom-induced dislocation, plastic working dislocation (which may disappear depending on preheat treatment conditions), existing solid solution chromium element (pseudo-sensitive) C curve (as shown semi-schematically in FIG. 12, the pseudo-sensitization curve is expressed by the temperature-time relationship of the C type. As described above, the upper and lower limits of the processing temperature are 850 ° C. and 550 ° C. ), For example, at 700 ° C.), an appropriate amount of chromium carbide is uniformly and finely precipitated in the crystal grains of the material structure in the carburized region. At this time, a solute chromium deficiency phenomenon occurs more or less (reverse concentration gradient of chromium element; FIG. 8). If this influence can be overlooked, the nano-surface modification ends with the processing so far. In other words, the metal member (processed member) is assembled and put to practical use after the processing so far, and exhibits high temperature durability with improved high temperature frictional wear resistance.

一方、クロム欠乏層の発生が耐高温酸化特性を阻害し、実用条件上、高温耐久性向上に支障をきたす場合は、擬鋭敏化処理に続いてクロム元素の逆濃度勾配を利用した逆拡散処理もしくはキャリアガスを用いてレアアースメタル添加処理を行い、劣化した材料表面（近傍）の耐高温酸化特性を回復させる。金属部材（加工部材）は、その後、アッセンブル・実用に供され、耐高温摩擦摩耗特性及び耐高温酸化特性が向上した高温耐久能を発揮する。   On the other hand, if the generation of chromium-deficient layers interferes with high-temperature oxidation resistance and impairs the improvement of high-temperature durability under practical conditions, reverse diffusion treatment using a reverse concentration gradient of chromium element is followed by pseudo-sensitization treatment. Alternatively, a rare earth metal addition treatment is performed using a carrier gas to restore the high temperature oxidation resistance of the deteriorated material surface (near). The metal member (processed member) is then subjected to assembly and practical use, and exhibits high temperature durability with improved high temperature friction and wear resistance and high temperature oxidation resistance.

なお、被処理材（金属部材）は、前記〔００３８〕、〔００３９〕の各処理後に冷却、ガラスビーズなどによる表面変色層の除去、検査などに適宜供されるものであり、これはアッセンブル、実地使用に際して、通常要求される工程（処置）である。
また、図１では、被処理材に低温浸炭処理を施す場合を示したが、浸炭処理に代えて浸窒処理（低温浸窒）を施しても構わないし、これら双方の処理を被処理材に施しても構わない。また、低温プラズマ浸炭および／または浸窒処理で行う場合は、図１の工程においてフッ化処理が不要となり、替わりに真空プラズマ発生装置（炉）が必要となる。
なお、フッ化処理、低温浸炭または低温プラズマ浸炭、擬鋭敏化、逆拡散処理またはレアアースメタル添加処理の各工程を、同一炉で連続的に行うこともできるし、それぞれ別の炉で１つあるいは２つ以上に分けて併行して行うこともできる。 In addition, the material to be treated (metal member) is appropriately provided for cooling, removal of the surface discoloration layer by glass beads, inspection, etc. after each treatment of [0038] and [0039]. This is a process (treatment) that is usually required for practical use.
Further, FIG. 1 shows the case where the material to be treated is subjected to the low-temperature carburizing treatment. However, the carburizing treatment may be performed in place of the carburizing treatment, and both treatments may be performed on the material to be treated. You may give it. In the case of low temperature plasma carburizing and / or nitriding, fluorination is not required in the process of FIG. 1, and a vacuum plasma generator (furnace) is required instead.
In addition, each process of fluorination treatment, low temperature carburization or low temperature plasma carburization, pseudo-sensitization, reverse diffusion treatment or rare earth metal addition treatment can be performed continuously in the same furnace, or each in a separate furnace. It can also be performed by dividing into two or more.

ここで上記一連の連続処理を行った際の高温耐久性（特に耐高温摩擦摩耗特性と耐高温酸化特性）に関連するメカニズムとして、図２の模式図を参照して、関連諸元素、化合物の一例として浸炭の場合の断面表層近傍の変化状況について以下説明する。   Here, as a mechanism related to high temperature durability (especially high temperature friction and wear resistance and high temperature oxidation resistance) when performing the above-described series of continuous treatments, referring to the schematic diagram of FIG. As an example, the change state in the vicinity of the cross-sectional surface layer in the case of carburizing will be described below.

図２（ａ）は、一例として、クロムを含有する典型的耐熱材料である高級オーステナイト系ステンレス鋼（例えばSUS310S ）を被処理材とし、このものに低温浸炭処理を施した状態、つまり擬鋭敏化処理は行っていない状態の固溶クロム量、浸入型原子として被処理材表層部（例えば30μｍ）に浸入した固溶炭素量の断面内分布を模式的に示したものである。クロムは板厚内表層部より内部に向けて素材中の所定量と同一の値（Cr0 ）になる。そして低温浸炭により表層付近の炭素量が、素材の所定量（C0）より増加して、表面でC1の濃度に達し、浸炭距離ｄにおいて濃度C0になる。すなわち（固溶）炭素濃度は、C1→C0間で濃度勾配（これを本明細書では「正濃度勾配」と称している）を呈し、また距離ｄがナノ表面改質層の厚み（例えばｄ＝30μｍ）となる。この処理を行った実際のＥＰＭＡ（既出図８の説明文を参照）測定チャートを図１３に示す。上記記述のごとく浸炭した固溶炭素の正濃度勾配を呈する明瞭な濃度曲線が表層部において見られる。例えば上記特許文献２による、この低温浸炭処理のみの場合、上記〔００１８〕に記載したように、ある程度の硬度アップへの寄与が生じ、マイルドな環境であれば、ある程度の耐久性を有するが、本願の意図している650 〜1050℃における長時間熱サイクル環境下での使用には甚だ不十分で、実際上の使用に耐え難い（後段の図１５、図１６に各改質条件の実施例を示す）。 FIG. 2 (a) shows, as an example, a high-grade austenitic stainless steel (for example, SUS310S), which is a typical heat-resistant material containing chromium, and a low-temperature carburizing treatment on this material, that is, pseudo-sensitization. The amount of solid solution chromium in a state where the treatment is not performed and the distribution in the cross section of the amount of solid solution carbon infiltrated into the surface layer of the material to be treated (for example, 30 μm) as an intrusion type atom are schematically shown. Chromium has the same value (Cr 0 ) as a predetermined amount in the material from the surface layer inside the plate thickness toward the inside. Then, the carbon content near the surface layer increases from the predetermined amount (C 0 ) of the raw material by low temperature carburizing, reaches the concentration of C 1 on the surface, and becomes the concentration C 0 at the carburizing distance d. That is, the (solid solution) carbon concentration exhibits a concentration gradient between C 1 and C 0 (this is referred to as “positive concentration gradient” in this specification), and the distance d is the thickness of the nano-surface modified layer ( For example, d = 30 μm). FIG. 13 shows an actual EPMA (see the explanatory note in FIG. 8) measurement chart in which this processing has been performed. A clear concentration curve showing a positive concentration gradient of carburized solute carbon as described above can be seen in the surface layer portion. For example, in the case of only this low-temperature carburizing treatment according to Patent Document 2, as described in the above [0018], a contribution to a certain degree of hardness increase occurs, and if it is a mild environment, it has a certain degree of durability. It is extremely insufficient for use in a long-time heat cycle environment at 650 to 1050 ° C. as intended by the present application, and it is difficult to withstand practical use (FIGS. Show).

そこで塑性加工転位及び浸入型原子誘起転位を利用した逆転の発想で擬鋭敏化処理を行う。すなわち浸炭部分（ナノ表面改質層領域の固溶炭素、固溶クロム量が十分存在する部位）で、硬質のクロム炭化物を結晶粒内に均一・微細に析出させるため擬鋭敏化処理を、低温浸炭処理に続けて同一炉で効率的な連続処理として行うのである。その結果の模式図が図２（ｂ）である。クロム炭化物は、表面から深さｄまでの領域で、濃度A →A0（＝０）となって正濃度勾配を呈しつつ均一・微細に析出し、耐高温摩擦摩耗特性を格段に向上させる（図５、６、７参照）。クロム炭化物にならなかった炭素は、固溶状態でC2→C0の正濃度勾配を示す（もちろんC2＜C1；処理条件によって浸炭固溶総炭素のうちクロム炭化物になる比率と固溶クロムの内方拡散程度とが変化するため、使用条件に適合するように、これらを制御する）。ここで、クロム炭化物の生成に伴って距離０→ｄの範囲で固溶クロムの低下、すなわちクロム欠乏層が生じ（Cr1 →Cr0 となる逆濃度勾配を呈する）、耐高温酸化特性を劣化させる（図８参照）。この状態でも高温使用状態でクロム欠乏層は、板厚内部からの固溶クロムがエントロピー増大の定則に従い、逆濃度勾配を消滅させるべく逆拡散・移動して徐々に回復する可能性があるから、使用条件によっては十分適用可能である。しかしながら、欠乏層が補填回復されるまでの（初期）酸化が懸念されるとともに、使用条件によっては適用不可となる。 Therefore, pseudo-sensitization treatment is performed with the idea of reversal using plastic working dislocations and intrusion-type atom-induced dislocations. In other words, pseudo-sensitization treatment is performed at a low temperature in order to deposit hard chromium carbide uniformly and finely in the crystal grains at the carburized part (the part where the amount of solid solution carbon and solid solution chromium in the nano-surface modified layer region is sufficient). The carburizing process is followed by an efficient continuous process in the same furnace. A schematic diagram of the result is shown in FIG. Chromium carbide precipitates uniformly and finely in a region from the surface to the depth d, with a concentration of A → A0 (= 0), exhibiting a positive concentration gradient, and remarkably improves the high-temperature frictional wear resistance (Fig. 5, 6, 7). Carbon that did not become chromium carbide shows a positive concentration gradient of C 2 → C 0 in the solid solution state (of course C 2 <C 1 ; depending on the processing conditions, the ratio of carbon carbide solid solution to the chromium carbide and the solid solution Since the degree of inward diffusion of chromium changes, these are controlled so as to meet the usage conditions). Here, with the formation of chromium carbide, solid solution chromium decreases in the range of distance 0 → d, that is, a chromium-deficient layer is formed (exhibiting a reverse concentration gradient from Cr 1 to Cr 0 ), and the high-temperature oxidation resistance is degraded. (See FIG. 8). Even in this state, the chromium-deficient layer can be recovered gradually by reverse diffusion and migration to eliminate the inverse concentration gradient according to the entropy increase rule according to the entropy increase rule in the chromium-deficient layer under high temperature use. It is fully applicable depending on the conditions of use. However, there is a concern about (initial) oxidation until the deficient layer is replenished and repaired, and it is not applicable depending on the use conditions.

この対応策として、本願請求項３や上記〔００２４〕で記載したように、図２（ｂ）のクロムの逆濃度勾配を利用した逆拡散処理を行い、クロム欠乏層を回復せしめたのが図２（ｃ）の状態である。これにより図２（ｂ）中のクロム濃度Cr1 〜Cr0 の欠乏部分は、全て素材所定量Cr0 に回復している（本願では、特願２００５−２１５６３２の新材料を含め、ステンレス鋼（クロム１２％以上含有）、耐熱材料、超合金などを対象としており、且つナノ表面改質層は数10μｍであり、クロム源といえる被処理材の板厚は数ｍｍ（すなわち数1000μｍ）であるから、逆拡散によって改質層より内部のマトリックス（母材）におけるクロム濃度の低下は、完全に無視できる）。逆拡散処理（850 〜950 ℃、特にここでは950 ℃×２時間）によって既生成クロム炭化物が分解・再固溶することも成長・凝集することもないため、分布状態は図２（ｂ）と同じである。残存している固溶炭素量は、正濃度勾配による内方への拡散によって、C2→C3へと若干分布状態が平滑化に向かうが、高温耐久性への副作用（悪影響）は特にない。以上のように、クロム逆拡散処理によって欠乏層が修復されて、被処理材（金属部材）の耐高温酸化特性を回復し、高温耐久性の向上が保証される（図９参照）。 As a countermeasure against this, as described in claim 3 of the present application and [0024] above, the reverse diffusion treatment using the reverse concentration gradient of chromium in FIG. 2B is performed to recover the chromium deficient layer. 2 (c). As a result, the deficient portions of the chromium concentrations Cr 1 to Cr 0 in FIG. 2B are all recovered to the raw material predetermined amount Cr 0 (in this application, including the new material of Japanese Patent Application No. 2005-215632, stainless steel ( Chromium 12% or more), heat resistant materials, superalloys, etc., and the nano-surface modified layer is several tens of μm, and the thickness of the material to be treated, which can be said to be a chromium source, is several mm (that is, several thousand μm). Therefore, the decrease in chromium concentration in the matrix (base material) inside the modified layer due to back diffusion is completely negligible). Since the formed chromium carbide does not decompose, re-solidify, grow or aggregate due to the reverse diffusion treatment (850 to 950 ° C., particularly 950 ° C. × 2 hours in this case), the distribution state is as shown in FIG. The same. The amount of solid solution carbon that remains is smoothed slightly from C 2 to C 3 due to inward diffusion due to the positive concentration gradient, but there is no side effect (adverse effect) on high temperature durability. . As described above, the deficient layer is repaired by the chromium reverse diffusion treatment, the high temperature oxidation resistance of the material to be treated (metal member) is restored, and the high temperature durability is improved (see FIG. 9).

もう一つのクロム欠乏層対策として、本願請求項５や上記〔００２６〕、〔００２７〕に記載したように、レアアースメタル（ＲＥＭ：rare earth metalの頭文字）をキャリアガス中に気相混合せしめて、条件制御によってナノ表面改質層つまりクロム欠乏層領域に浸透させる手法があり、これを行った状態が図２（ｄ）である。すなわち、ＲＥＭはR →R0（＝０）の正濃度勾配を呈した分布状態となり、このものの存在によってクロム欠乏層が図２（ｂ）と同じ状態で存在し続けても耐酸化保護皮膜を生ずるために、実用的に上記クロム逆拡散と同様の優れた高温耐久性を確保することができる。なお図２（ｄ）において、炭素やクロム炭化物の分布状態も図２（ｂ）と同じであり、それぞれ（C2→C0）、（A →A0（＝０）) を維持する。 As another countermeasure against the chromium deficient layer, as described in claim 5 of the present application and the above [0026] and [0027], rare earth metal (REM: an acronym for rare earth metal) is mixed in a gas phase in a carrier gas. In addition, there is a method of penetrating into the nano-surface modified layer, that is, the chromium-deficient layer region by condition control, and a state in which this is performed is shown in FIG. That is, REM has a distribution state exhibiting a positive concentration gradient of R 1 → R 0 (= 0), and even if the chromium-deficient layer continues to exist in the same state as in FIG. For this reason, the excellent high-temperature durability similar to the chromium back diffusion can be secured practically. In FIG. 2D, the distribution state of carbon and chromium carbide is also the same as in FIG. 2B, and (C 2 → C 0 ) and (A → A 0 (= 0)) are maintained, respectively.

以上述べたナノ表面改質方法を、本願請求項１０の新材料に施し、この金属素材を本願請求項１２で述べたＶＧＳタイプターボチャージャの排気ガイドアッセンブリの構成部品として適用した場合には、工業的差別化技術として特段の効果を発揮するものである。もちろん、こような新材料だけでなく、上記〔００４４〕に記載した超合金を含む種々のステンレス鋼、耐熱材料への適用も、それぞれのケースにおいて顕著な効果をもたらすことは言うまでもない。   When the nano-surface modification method described above is applied to the new material of claim 10 of the present application and this metal material is applied as a component of the exhaust guide assembly of the VGS type turbocharger described in claim 12 of the present application, As a special differentiation technology. Of course, it goes without saying that not only such new materials but also various stainless steels and heat-resistant materials including the superalloy described in the above [0044] can be applied to various cases.

以下に、本発明に基づくナノ表面改質を施した規格材SUS310S と「新材料」の高温（耐久）試験結果例を(1) 高温硬さ、(2) 高温摩擦摩耗、(3) 高温酸化（ＶＧＳターボチャージャへの適用を意図して自動車排気ガスをシミュレートした通常の高温大気雰囲気条件よりも厳しい高温の「大気＋10％水蒸気」雰囲気で試験を実施した）につき実施例として、それぞれ図１４、表１（図１５）、表２（図１６）を示すこととする。   The following are examples of high-temperature (durability) test results of the standard material SUS310S with nano-surface modification and “new material” based on the present invention: (1) high-temperature hardness, (2) high-temperature frictional wear, (3) high-temperature oxidation As an example for each case (the test was conducted in an “air + 10% water vapor” atmosphere at a higher temperature than the normal high-temperature air atmosphere conditions simulating automobile exhaust gas intended for application to a VGS turbocharger), FIG. Table 1 (FIG. 15) and Table 2 (FIG. 16) are shown.

図１４は室温（20℃）を含む900 ℃までの各温度における材料表面のビッカース硬さ（ＨV ）を測定した温度依存性を示す図である。表面改質非処理材（「新材料」及びSUS310S ）の室温におけるＨV ＝130 〜140 程度であり、温度の増加とともにＨV は漸減して行き、800 ℃以上では50以下に低減する。従って、例えば一般的なＶＧＳタイプのターボチャージャの使用温度である800 〜850 ℃程度の温度域における耐高温摩擦摩耗特性が劣化する問題が生じる（非処理状態で、新材料の方が温度の如何を問わず、若干硬さが大きい）。 FIG. 14 is a graph showing the temperature dependence of the Vickers hardness (H V ) of the material surface at various temperatures up to 900 ° C. including room temperature (20 ° C.). An H V = 130 to 140 approximately at room temperature of the surface modification untreated material ( "New Materials" and SUS310S), H V went gradually decreases with increasing temperature, at 800 ° C. or higher to reduce the 50 or less. Therefore, for example, there is a problem that the high-temperature friction and wear resistance deteriorates in a temperature range of about 800 to 850 ° C., which is the operating temperature of a general VGS type turbocharger. Regardless of the hardness)

そこで、新材料にフッ化事前処理による浸炭処理を行うと室温の表面硬さがＨV ＞300 になり、600 ℃位までは余り大きな硬さ低下は示さない。しかし、600 ℃以上になると硬さは急減し、非処理材とほとんど異ならなくなってしまう。これは浸炭した固溶炭素が内部へと拡散してしまうからである（一部は結晶粒界近傍でクロム炭化物の析出、すなわち鋭敏化を生じ、耐食性を損なう原因にもなる）。
一方、浸炭処理後に擬鋭敏化処理を行った新材料は、室温における表面硬さがＨV ＞500 となり、温度増加とともにＨV の低下は免れないが、800 ℃以上でＨV ＞100 を保っており、明らかに高温硬さに対して、一連の処理効果が認められる。すなわち、耐高温摩擦摩耗特性に対する効果が期待される。この擬鋭敏化処理の効果の主因は、図５、６、７に示したように浸炭時の浸入型原子誘起転位の導入によって結晶粒内に高硬度のクロム炭化物が均一析出することによるものである。 Therefore, when carburizing treatment by fluorination pretreatment is performed on the new material, the surface hardness at room temperature becomes H V > 300, and the hardness is not significantly reduced until about 600 ° C. However, when the temperature exceeds 600 ° C, the hardness decreases sharply and becomes almost the same as untreated material. This is because the carburized solid solution carbon diffuses into the interior (some of which causes precipitation of chromium carbide near the grain boundaries, that is, sensitization, which also causes a deterioration in corrosion resistance).
On the other hand, new materials were擬鋭Satoshika treatment after the carburizing treatment, the surface hardness H V> 500 becomes at room temperature, but decrease in H V is inevitable with the temperature increase, keeping the H V> 100 at 800 ° C. or higher Clearly, a series of treatment effects are recognized for high temperature hardness. That is, an effect on high temperature friction and wear resistance is expected. The main reason for the effect of this pseudo-sensitization treatment is that, as shown in FIGS. 5, 6 and 7, high hardness chromium carbide precipitates uniformly in the crystal grains due to the introduction of intrusion-type atom-induced dislocations during carburization. is there.

次いで、本発明のナノ表面改質が、ＶＧＳタイプターボチャージャの排気ガイドアッセンブリの構成部材や、その他種々の耐熱部材の高温耐久性（耐熱性）にとって重要であり、従って本発明の主目的である耐高温摩擦摩耗特性及び耐高温酸化（腐食）特性に関する実施例を表１（図１５）、表２（図１６）に示す（もう一つの重要な高温表面性状である高温表面硬さについては図１４において既述した）。
表１（図１５）にはピンオンディスク法により800 ℃大気中で３ｍ相当の高温摩擦摩耗試験を行った結果を示す。浸炭もしくは浸窒法は、フッ化処理によるそれぞれ500 ℃×16時間、570 ℃×16時間処理によるものであり、擬鋭敏化処理はいずれも700 ℃×2 時間行われた。また、逆拡散処理は900 ℃×2 時間、レアアースメタルの材料表面への添加浸入は、キャリアガスとしてアルゴンを用い、逆拡散処理温度と同一条件とした。浸炭・浸窒処理に先行する塑性加工転位の導入のための塑性加工は圧縮変形によって、相当歪εを約0.3(＝30％) 加えた。このときの転位密度は、約1011/cm2で、浸入型原子誘起転位の転位密度（約1012/cm2）に比べて約1/10である。浸炭、浸入の共存条件は、上記の試験温度で３通りに変えて行った。なお、比較のために主として用いた「新材料（完全オーステナイトステンレス鋼）」の表面改質非処理材と規格材のSUS310S （従来より主としてＶＧＳタイプのターボチャージャの構成部材として使用されている）の実施例も併せて示した。以上のうち、フッ化処理低温処理の替わりに低温プラズマ処理の場合も同様の結果が得られている。 Next, the nano-surface modification of the present invention is important for the high-temperature durability (heat resistance) of exhaust gas guide assembly components of VGS type turbochargers and other various heat-resistant members, and is therefore the main object of the present invention. Examples relating to high temperature friction and wear resistance and high temperature oxidation (corrosion) resistance are shown in Table 1 (FIG. 15) and Table 2 (FIG. 16) (for high temperature surface hardness, which is another important high temperature surface property) 14).
Table 1 (FIG. 15) shows the results of a high temperature frictional wear test equivalent to 3 m in the air at 800 ° C. by the pin-on-disk method. The carburizing or nitrocarburizing methods were carried out by fluorination treatment at 500 ° C. for 16 hours and 570 ° C. for 16 hours, respectively, and pseudo-sensitization treatment was performed at 700 ° C. for 2 hours. In addition, the reverse diffusion treatment was performed at 900 ° C. for 2 hours, and the rare earth metal was added into the material surface using argon as a carrier gas under the same conditions as the reverse diffusion treatment temperature. The plastic working for the introduction of plastic working dislocations prior to carburizing and nitriding treatment added about 0.3 (= 30%) of equivalent strain ε by compressive deformation. The dislocation density at this time is about 10 11 / cm 2 , which is about 1/10 compared to the dislocation density (about 10 12 / cm 2 ) of the interstitial atom-induced dislocation. Carburization and infiltration coexisting conditions were changed in three ways at the above test temperature. For comparison, the “new material (completely austenitic stainless steel)” used mainly for the comparison of the surface-modified non-treated material and the standard material SUS310S (conventionally used as a component of VGS type turbochargers) Examples are also shown. Among the above, the same result is obtained also in the case of the low temperature plasma treatment instead of the fluorination treatment low temperature treatment.

表１（図１５）によれば、表面改質非処理材に比べて、低温浸炭もしくは低温浸窒を行うと、ある程度の効果が得られると考えてよいが、図１４の硬さの実施例からも分かるように、800 ℃ではほとんど硬さの差がなくなるので、（耐高温摩擦摩耗特性は高温硬さのみで決まるものではないが、主たる支配要因としてよい）、この結果は理解できる。これに対して、擬鋭敏化処理を施すと明らかに動摩擦係数、摩耗量（ピンとディスクの双方の摩耗量の和）が低下して、耐摩擦摩耗特性が改善されることが分かる。図５、図６、図７で言及した効果が明白に生じていることが実証された。この状態では、前述のように材料表面にクロム欠乏層が発生している。これに逆拡散処理やレアアースメタル添加処理を行ったときの耐摩擦摩耗特性は、擬鋭敏化処理を行った場合と同等としてよい。また、事前塑性加工を施した後に浸炭もしくは浸窒を行ったままの状態の場合、事前加工を行わなかった際と比較して若干効果がある。且つ、擬鋭敏化処理を行うと、やはり著効があり、特徴として浸炭系の効果が浸窒系に比べて大きい。これは、浸炭の場合は、炭素の過飽和固溶状態での浸入と転位の生成導入とクロム炭化物の析出現象が生じるのに対し、浸窒の場合は、浸入した窒素が鉄と炭化物をつくりながら転位も生成導入され、擬鋭敏化によって処理温度が上がるため鉄炭化物が解離すると同時にクロム窒化物が転位核を生成サイトとしつつ微細均一析出現象が生じるという、現象面でのメカニズムの差が存在することが関係している（これは事前塑性加工処理を行わない擬鋭敏化処理に関しても言えることである）。更に、浸炭・浸窒を併用し擬鋭敏化処理を行った場合であるが、試験温度が600 〜1050℃のほぼ中間の800 ℃における結果ゆえ、三条件の差は既述のごとく必ずしも明確ではないが、敢えて言えば、浸炭と浸窒を同時併行に行うのが相乗効果の観点から最も効果的であると言ってよい。   According to Table 1 (FIG. 15), it may be considered that a certain degree of effect can be obtained by performing low-temperature carburizing or low-temperature nitriding as compared with the surface-modified untreated material. As can be seen from the results, the difference in hardness is almost eliminated at 800 ° C. (high temperature friction and wear resistance is not determined only by high temperature hardness, but may be a main controlling factor), so this result can be understood. On the other hand, it can be seen that when the pseudo-sensitization treatment is performed, the coefficient of dynamic friction and the amount of wear (the sum of the amounts of wear of both the pin and the disk) are lowered, and the friction and wear resistance is improved. It was demonstrated that the effects mentioned in FIGS. 5, 6 and 7 are clearly occurring. In this state, a chromium-deficient layer is generated on the material surface as described above. The frictional wear resistance when the reverse diffusion treatment or the rare earth metal addition treatment is performed may be equivalent to that when the pseudo-sensitization treatment is performed. Further, in the state where the carburizing or nitriding is performed after the pre-plastic working, there is a slight effect compared with the case where the pre-working is not performed. Moreover, when the pseudo-sensitization treatment is performed, there is still a remarkable effect, and as a feature, the effect of the carburizing system is larger than that of the nitriding system. This is because in the case of carburizing, intrusion in the supersaturated solid state of carbon, the introduction of dislocations, and precipitation of chromium carbide occur, whereas in the case of nitriding, the infiltrated nitrogen forms iron and carbide. Dislocations are also generated and introduced, and the processing temperature rises due to pseudo-sensitization, so that iron carbide dissociates, and at the same time, there is a difference in the phenomenon mechanism that chromium nitride causes a fine uniform precipitation phenomenon with dislocation nuclei as production sites. (This is also true for pseudo-sensitization without pre-plastic working). Furthermore, although it is the case where pseudo-sensitization treatment is performed using carburizing and nitrocarburizing, the difference in the three conditions is not always clear as described above because the test temperature is at the middle 800 ° C of 600-1050 ° C. Although there is not, it can be said that performing carburizing and nitriding simultaneously is the most effective from the viewpoint of synergistic effect.

新材料との比較のためにSUS310S の非改質、浸炭のみ、擬鋭敏化の結果を示したが、基本的傾向は新材料と同様である。しかしながら、いずれのデータも新材料よりは劣っており、新材料の方がナノ表面改質効果が得られ易いことが実証された。これは既述のメカニズムに関して予想したように主として新材料のNi量の減少によって、不動態皮膜が浸炭を容易化することに起因している。
表２（図１６）には、ＶＧＳタイプターボチャージャの構成部材を意識して、自動車排ガス中に含まれ高温酸化条件を厳しくする水蒸気を添加させた条件で（ベースは大気）、850 ℃×100 時間の連続高温酸化試験の結果を示した。その他の試験条件は表１（図１５）と同様である。 For comparison with the new material, the results of non-modified SUS310S, only carburizing, and pseudo-sensitization were shown, but the basic trend is the same as the new material. However, all the data are inferior to the new material, and it was proved that the new material can easily obtain the nano-surface modification effect. This is due to the fact that the passive film facilitates carburization, mainly due to the decrease in the Ni content of the new material, as expected for the mechanism described above.
Table 2 (FIG. 16) shows that the components of the VGS type turbocharger are conscious of water vapor that is included in the exhaust gas of the automobile and makes the high-temperature oxidation conditions strict (base is air), 850 ° C. × 100 The results of the time continuous high temperature oxidation test are presented. Other test conditions are the same as in Table 1 (FIG. 15).

表２（図１６）によれば、「新材料」の表面改質処理なしの場合は、酸化重量変化が15.7 g/m2 であり、外観もまだら模様を呈した。浸炭もしくは浸窒処理を施した場合は、若干、腐食量が減少しているが、その程度は、いくらか浸炭処理の場合の方が大きい。これは、前述したように浸炭と浸窒時の炭素もしくは窒素の挙動の差が影響しているものと考えられる。これらに擬鋭敏化処理を施すと摩擦摩耗の場合ほどの効果はないが、ある程度の耐高温酸化特性の改善が見られる。これはクロム炭化物もしくはクロム窒化物析出そのものの材料表面における存在と残存固溶炭素もしくは固溶窒素及び固溶クロム元素の存在に基づく、元素の摺動部での相互移動、すなわち親和性を阻害せしめるカバリング効果に起因するものと考えられる。ただし、前述のように材料表面にクロム欠乏層が生成するのは、回避し難いゆえ、これは耐酸化性に対する阻害要因となる。そこで、更にクロムの逆拡散処理によるクロム欠乏層の回復・補填もしくは気相レアアースメタルの材料表面及び真下への添加・含有処理を行って、耐酸化性の向上を図ったデータを見ると、酸化腐食重量変化（増加）は、浸炭系及び浸窒系新材料ともに明らかに減少しており、予想通りの効果が得られた。 According to Table 2 (FIG. 16), when the surface modification treatment of “new material” was not performed, the change in oxidized weight was 15.7 g / m 2 and the appearance was a mottled pattern. When carburizing or nitriding treatment is performed, the amount of corrosion is slightly reduced, but the extent is somewhat greater in the case of carburizing treatment. As described above, this is considered to be due to the difference in the behavior of carbon or nitrogen during carburizing and nitriding. When these are subjected to pseudo-sensitization treatment, they are not as effective as in the case of frictional wear, but some improvement in high-temperature oxidation resistance is observed. This inhibits the mutual movement, that is, the affinity of the sliding elements, based on the presence of chromium carbide or chromium nitride precipitates on the material surface and the presence of residual solid solution carbon or solid nitrogen and solid solution chromium element. This is thought to be due to the covering effect. However, it is difficult to avoid the formation of a chromium-deficient layer on the surface of the material as described above, and this is an obstacle to oxidation resistance. Therefore, if we look at the data to improve the oxidation resistance by further recovering and filling the chromium-deficient layer by the reverse diffusion treatment of chromium or adding and containing the vapor phase rare earth metal directly below the material surface, Corrosion weight change (increase) was clearly reduced in both carburized and nitrocarburized new materials, and the expected effect was obtained.

これは、度々、既述してきた通り、かたやクロム欠乏層の回復による表面（近傍）固溶クロム量が回復増量され、ペレブスカイト系酸化クロム保護皮膜（Cr2O3)が耐酸化機能を発揮したこと、他方、レアアースメタルの酸化物の形成による外部酸化遮断作用による酸化腐食抑制効果に起因するものである。前加工の効果は、浸炭系、浸窒系ともに見られず、前加工なしの改質条件の違いによる結果と類似している。浸窒系では、ある程度、効果的であった。この結果は、摩擦摩耗の場合と対照をなしており、前加工による析出強化作用が、耐酸化よりも摩擦摩耗で生じ易いこと、そして浸窒系で両特性ともある程度の効果が得られることが確認できた。この事実は、既述の論理と合致しており、新しい知見と言えるものである。更に浸炭／浸窒の複合処理後、擬鋭敏化処理と逆拡散処理を行った表２（図１６）に示した三条件の結果は、酸化温度が600 〜1050℃のほぼ中間であるところから浸炭／浸窒の同時処理の結果が他の二条件の結果より若干良好な結果となった。これも既述の指導原理並びにそれによる予想と違わない結果と言える。新材料との比較のためにSUS310S の非改質処理、浸炭のみ、浸炭後擬鋭敏化処理、その後さらにクロムの逆拡散処理もしくはレアアースメタル処理を行った結果も示してあるが、基本的に新材料と同等の傾向を示している。ただし、摩擦摩耗の場合と同じく、いずれのデータも新材料よりは劣っており、新材料の方がナノ表面改質性に優れることが実証されたと言える。この事実は、既述のメカニズムに関して予想したように主として新材料の低Ni化による不動態皮膜が浸炭を容易にするとの仮説から説明することができる。 As described above, the amount of solute chromium in the surface (near) by recovery of the person and the chromium-deficient layer was often recovered and increased, and the perovskite chromium oxide protective film (Cr 2 O 3 ) exhibited an oxidation resistance function. On the other hand, this is due to the effect of inhibiting oxidative corrosion due to the external oxidation blocking action due to the formation of rare earth metal oxides. The effect of pre-processing is not seen in both carburizing and nitriding systems, and is similar to the result of the difference in the modification conditions without pre-processing. Nitrogen was effective to some extent. This result is in contrast to the case of frictional wear. Precipitation strengthening effect due to pre-processing is more likely to occur in frictional wear than oxidation resistance, and a certain degree of effect can be obtained for both characteristics in a nitriding system. It could be confirmed. This fact is consistent with the previously described logic and is a new finding. Further, after the combined carburizing / nitriding treatment, the pseudo-sensitization treatment and the reverse diffusion treatment were performed, and the results under the three conditions shown in Table 2 (FIG. 16) are that the oxidation temperature is almost in the middle of 600 to 1050 ° C. The result of simultaneous carburizing / nitriding treatment was slightly better than the results of the other two conditions. This is also a result that is not different from the teaching principle described above and the prediction made there. For comparison with new materials, the results of non-reforming treatment of SUS310S, carburization only, post-carburization pseudo-sensitization treatment, and further chromium reverse diffusion treatment or rare earth metal treatment are also shown. It shows the same tendency as the material. However, as in the case of frictional wear, all the data are inferior to the new material, and it can be said that the new material has been demonstrated to have better nano-surface modification properties. This fact can be explained by the hypothesis that, as expected with respect to the mechanism described above, the passive film of the new material with low Ni facilitates carburization.

本発明のナノ表面改質方法は、被処理材の耐高温摩擦摩耗特性や耐高温酸化特性等の高温耐久性を向上させるのに好適な手法である。このためナノ表面改質方法が施された金属部材は、高温・排ガス下で使用されるＶＧＳターボチャージャの構成部材に適しており、以下、このＶＧＳターボチャージャ（ＶＧＳユニット）について説明する（図３）。   The nano-surface modification method of the present invention is a method suitable for improving high-temperature durability such as high-temperature friction and wear resistance and high-temperature oxidation resistance of a material to be treated. For this reason, the metal member that has been subjected to the nano-surface modification method is suitable as a constituent member of a VGS turbocharger used under high temperature and exhaust gas, and this VGS turbocharger (VGS unit) will be described below (FIG. 3). ).

ＶＧＳターボチャージャは、特にエンジンの低速回転時において排気ガスＧを絞り込んで排気流量を調節するものであり、排気ガイドアッセンブリＡを主な構成要素として成る。排気ガイドアッセンブリＡは、一例として図３に示すように、排気タービンＴの外周に設けられ実質的に排気ガスＧを絞る複数の可変翼１と、可変翼１を回動自在に保持するタービンフレーム２と、排気ガスＧの流量を適宜設定すべく可変翼１を一定角度回動させる可変機構３とを具えて成るものである。以下、各構成部について更に説明する。   The VGS turbocharger adjusts the exhaust gas flow by restricting the exhaust gas G especially when the engine is rotating at a low speed, and the exhaust gas guide assembly A is a main component. As shown in FIG. 3 as an example, the exhaust guide assembly A includes a plurality of variable blades 1 that are provided on the outer periphery of the exhaust turbine T and substantially throttle the exhaust gas G, and a turbine frame that rotatably holds the variable blades 1. 2 and a variable mechanism 3 for rotating the variable blade 1 by a predetermined angle so as to appropriately set the flow rate of the exhaust gas G. Hereinafter, each component will be further described.

まず可変翼１について説明する。このものは一例として図３に示すように、排気タービンＴの外周に沿って円弧状に複数（一基の排気ガイドアッセンブリＡに対して概ね１０個から１５個程度）配設され、そのそれぞれが、ほぼ同程度づつ回動して排気流量を適宜調節するものである。可変翼１は、翼部１１と軸部１２とを具えて成り、以下これらについて説明する。
翼部１１は、主に排気タービンＴの幅寸法に応じて一定幅を有するように形成されるものであり、その幅方向における断面が概ね翼形に形成され、排気ガスＧが効果的に排気タービンＴに向かうように構成されている。なお、ここで翼部１１の幅寸法を便宜上、翼幅ｈとする。
また軸部１２は、翼部１１と一体的に連続形成されるものであり、翼部１１を動かす際の回動軸となる。 First, the variable blade 1 will be described. As an example, as shown in FIG. 3, a plurality of these are arranged in an arc shape along the outer periphery of the exhaust turbine T (approximately 10 to 15 with respect to one exhaust guide assembly A). The exhaust flow rate is adjusted appropriately by rotating approximately the same degree. The variable wing 1 includes a wing portion 11 and a shaft portion 12, which will be described below.
The blade portion 11 is formed to have a constant width mainly in accordance with the width dimension of the exhaust turbine T, and the cross section in the width direction is formed in a substantially airfoil shape so that the exhaust gas G can be effectively exhausted. It is configured to go to the turbine T. Here, the width dimension of the wing part 11 is referred to as a wing width h for convenience.
Further, the shaft portion 12 is formed integrally and continuously with the wing portion 11 and serves as a rotating shaft when the wing portion 11 is moved.

また翼部１１と軸部１２との接続部位には、軸部１２から翼部１１に向かって窄まるようなテーパ部１３と、軸部１２より幾分大径の鍔部１４とが連なるように形成されている。なお、鍔部１４の底面は、翼部１１における軸部１２側の端面と、ほぼ同一平面上に形成され、この平面が、可変翼１をタービンフレーム２に取り付けた際の座面となり、排気タービンＴにおける幅方向（翼幅ｈの方向）の位置規制を図る作用を担っている。
更に軸部１２の先端部には、可変翼１の取付状態の基準となる基準面１５が形成される。この基準面１５は、後述する可変機構３に対しカシメ等によって固定される部位であり、一例として図３に示すように、軸部１２を対向的に切り欠いた二平面が、翼部１１に対してほぼ一定の傾斜状態に形成されて成るものである。 In addition, a tapered portion 13 that is narrowed from the shaft portion 12 toward the wing portion 11 and a flange portion 14 that is somewhat larger in diameter than the shaft portion 12 are connected to the connection portion between the wing portion 11 and the shaft portion 12. Is formed. Note that the bottom surface of the flange portion 14 is formed on substantially the same plane as the end surface of the blade portion 11 on the shaft portion 12 side, and this plane serves as a seating surface when the variable blade 1 is attached to the turbine frame 2. The turbine T is responsible for regulating the position in the width direction (the direction of the blade width h).
Further, a reference surface 15 serving as a reference for the mounting state of the variable wing 1 is formed at the tip of the shaft portion 12. The reference surface 15 is a part fixed to the variable mechanism 3 to be described later by caulking or the like. As an example, as shown in FIG. 3, two planes formed by cutting away the shaft portion 12 are formed on the wing portion 11. On the other hand, it is formed in a substantially constant inclined state.

次にタービンフレーム２について説明する。このものは、複数の可変翼１を回動自在に保持するフレーム部材として構成されるものであって、一例として図３に示すように、フレームセグメント２１と保持部材２２とによって可変翼１（翼部１１）を挟み込むように構成される。
フレームセグメント２１は、可変翼１の軸部１２を受け入れるフランジ部２３と、後述する可変機構３を外周に嵌めるボス部２４とを具えて成る。なお、このような構造からフランジ部２３には、周縁部分に可変翼１と同数の軸受孔２５が等間隔で形成されるものである。
また保持部材２２は、図３に示すように中央部分が開口された円板状に形成されている。そして、これらフレームセグメント２１と保持部材２２とによって挟み込まれた可変翼１の翼部１１を、常に円滑に回動させ得るように、両部材間の寸法が、ほぼ一定（概ね可変翼１の翼幅寸法程度）に維持されるものであり、一例として軸受孔２５の外周部分に、四カ所設けられたカシメピン２６によって両部材間の間隔が維持されている。ここで、このカシメピン２６を受け入れるためにフレームセグメント２１及び保持部材２２に開口される孔をピン孔２７とする。 Next, the turbine frame 2 will be described. This is configured as a frame member that rotatably holds a plurality of variable blades 1, and as an example, as shown in FIG. 3, the variable blade 1 (blade) is constituted by a frame segment 21 and a holding member 22. Part 11).
The frame segment 21 includes a flange portion 23 that receives the shaft portion 12 of the variable wing 1 and a boss portion 24 that fits the variable mechanism 3 described later on the outer periphery. Because of this structure, the flange portion 23 is formed with the same number of bearing holes 25 as the variable blades 1 at equal intervals in the peripheral portion.
Further, the holding member 22 is formed in a disk shape having an opening at the center as shown in FIG. The dimension between the two members is substantially constant (generally the blade of the variable blade 1 so that the blade portion 11 of the variable blade 1 sandwiched between the frame segment 21 and the holding member 22 can be rotated smoothly at all times. As an example, the distance between the two members is maintained by caulking pins 26 provided at four locations on the outer peripheral portion of the bearing hole 25. Here, a hole opened in the frame segment 21 and the holding member 22 to receive the caulking pin 26 is referred to as a pin hole 27.

なお、図３に示す実施例では、フレームセグメント２１のフランジ部２３は、保持部材２２とほぼ同径のフランジ部２３Ａと、保持部材２２より幾分大きい径のフランジ部２３Ｂとの二つのフランジ部分から成り、これらを同一部材で形成するものであるが、同一部材での加工が複雑化する場合等にあっては、径の異なる二つのフランジ部を分割して形成し、後にカシメ加工やブレージング加工等によって接合することも可能である。   In the embodiment shown in FIG. 3, the flange portion 23 of the frame segment 21 has two flange portions, that is, a flange portion 23 </ b> A having substantially the same diameter as the holding member 22 and a flange portion 23 </ b> B having a slightly larger diameter than the holding member 22. These are formed with the same member, but when processing with the same member is complicated, two flange parts with different diameters are formed separately, and then caulking or brazing is performed. It is also possible to join by processing or the like.

次に可変機構３について説明する。このものはタービンフレーム２のボス部２４の外周側に設けられ、排気流量を調節するために可変翼１を適宜回動させるものであり、一例として図３に示すように、アッセンブリ内において実質的に可変翼１の回動を生起する回動部材３１と、この回動を可変翼１に伝える伝達部材３２とを具えて成るものである。
回動部材３１は、図示するように中央部分が開口された略円板状に形成され、その周縁部分に可変翼１と同数の伝達部材３２を等間隔で設けるものである。なお、この伝達部材３２は、回動部材３１に対し回転自在に取り付けられる駆動要素３２Ａと、可変翼１の基準面１５に固定状態に取り付けられる受動要素３２Ｂとを具えて成り、これら駆動要素３２Ａと受動要素３２Ｂとが接続された状態で、回動が伝達される。具体的には四角片状の駆動要素３２Ａを、回動部材３１に対して回転自在にピン止めするとともに、この駆動要素３２Ａを受け入れ得るように略Ｕ字状に形成された受動要素３２Ｂを、可変翼１の先端の基準面１５に固定し、四角片状の駆動要素３２ＡをＵ字状の受動要素３２Ｂに嵌め込み、双方を係合させるように、回動部材３１をボス部２４に取り付ける。 Next, the variable mechanism 3 will be described. This is provided on the outer peripheral side of the boss portion 24 of the turbine frame 2 and appropriately rotates the variable blade 1 in order to adjust the exhaust flow rate. As an example, as shown in FIG. In addition, a rotating member 31 that causes the variable wing 1 to rotate and a transmission member 32 that transmits the rotation to the variable wing 1 are provided.
As shown in the figure, the rotating member 31 is formed in a substantially disk shape with an open central portion, and the same number of transmission members 32 as the variable blades 1 are provided at equal intervals on the peripheral portion. The transmission member 32 includes a driving element 32A that is rotatably attached to the rotating member 31, and a passive element 32B that is fixedly attached to the reference surface 15 of the variable blade 1, and these driving elements 32A. The rotation is transmitted in a state where the passive element 32B and the passive element 32B are connected. Specifically, a square piece drive element 32A is rotatably pinned to the rotation member 31, and a passive element 32B formed in a substantially U shape so as to receive the drive element 32A is provided. The rotating member 31 is attached to the boss portion 24 so as to be fixed to the reference surface 15 at the tip of the variable wing 1 and to be fitted with the square-shaped drive element 32A into the U-shaped passive element 32B.

なお、複数の可変翼１を取り付けた初期状態において、これらを周状に整列させるにあたっては、各可変翼１と受動要素３２Ｂとが、ほぼ一定の角度で取り付けられる必要があり、図３に示す実施例においては、主に可変翼１の基準面１５がこの作用を担っている。また回動部材３１を単にボス部２４に嵌め込んだままでは、回動部材３１がタービンフレーム２と僅かに離反した際、伝達部材３２の係合が解除されてしまうことが懸念されるため、これを防止すべく、タービンフレーム２の対向側から回動部材３１を挟むようにリング３３等を設け、回動部材３１に対してタービンフレーム２側への押圧傾向を賦与するものである。
このような構成によって、エンジンが低速回転を行った際には、可変機構３の回動部材３１を適宜回動させ、伝達部材３２を介して軸部１２に伝達し、図３に示すように可変翼１を回動させ、排気ガスＧを適宜絞り込んで、排気流量を調節するものである。 In the initial state where a plurality of variable blades 1 are attached, in order to align them in a circumferential shape, each variable blade 1 and the passive element 32B must be attached at a substantially constant angle, as shown in FIG. In the embodiment, the reference surface 15 of the variable wing 1 is mainly responsible for this function. Further, if the rotating member 31 is simply fitted in the boss portion 24, there is a concern that the engaging of the transmission member 32 is released when the rotating member 31 is slightly separated from the turbine frame 2. In order to prevent this, a ring 33 or the like is provided so as to sandwich the rotating member 31 from the opposite side of the turbine frame 2, and a tendency to press the rotating member 31 toward the turbine frame 2 is imparted.
With such a configuration, when the engine rotates at a low speed, the rotation member 31 of the variable mechanism 3 is appropriately rotated and transmitted to the shaft portion 12 via the transmission member 32, as shown in FIG. The variable vane 1 is rotated and the exhaust gas G is appropriately throttled to adjust the exhaust flow rate.

このようなＶＧＳターボチャージャにあっては、エンジンの回転数に応じて、可変翼１を繰り返し回動させる必要があるため、例えば可変翼１（軸部１２）と、タービンフレーム２（軸受孔２５）とは、絶えず摺接する関係にある。このような関係にある部品同士に、本発明のナノ表面改質方法を施すことは、可変翼１を回動させる際の駆動力の低減化、回動時の摩擦抵抗の低減化及び摩滅・焼つき（スティック）の抑制、可変翼１の円滑且つ確実な制御等を実現するという格別な効果をもたらすものである。   In such a VGS turbocharger, since it is necessary to repeatedly rotate the variable blade 1 in accordance with the rotational speed of the engine, for example, the variable blade 1 (shaft portion 12) and the turbine frame 2 (bearing hole 25). ) Is constantly in sliding contact. Applying the nano-surface modification method of the present invention to parts having such a relationship reduces the driving force when rotating the variable blade 1, reduces the frictional resistance when rotating, and reduces wear and tear. This brings about special effects such as suppression of sticking (stick) and smooth and reliable control of the variable blade 1.

本発明の高温耐久性を高めたナノ表面改質方法の一例を示した工程図である。It is process drawing which showed an example of the nano surface modification method which improved the high temperature durability of this invention. 鋼材中のＣ、Cr、クロム炭化物、ＲＥＭ等の各種濃度を示す模式図であって、低温浸炭処理を施した状態の模式図（ａ）、更に（ａ）の状態に擬鋭敏化処理を施した際の模式図（ｂ）、更に（ｂ）の状態に逆拡散処理を施した際の模式図（ｃ）、並びに（ｂ）の状態にレアアースメタル元素を導入する添加処理を施した際の模式図（ｄ）である。It is a schematic diagram showing various concentrations of C, Cr, chromium carbide, REM, etc. in a steel material, and is a schematic diagram (a) in a state where low-temperature carburizing treatment has been performed, and further a pseudo-sensitization treatment is applied to the state of (a). (B), a schematic diagram (c) when the reverse diffusion treatment is applied to the state (b), and an addition treatment for introducing a rare earth metal element to the state (b). It is a schematic diagram (d). 本発明のナノ表面改質方法を施した金属部材の一例であって、これを構成部材として組み付けて成る排気ガイドアッセンブリの斜視図（ａ）、並びにこの排気ガイドアッセンブリを組み込んで成るＶＧＳタイプのターボチャージャの斜視図（ｂ）である。FIG. 2 is an example of a metal member subjected to the nano-surface modification method of the present invention, and is a perspective view (a) of an exhaust guide assembly in which the metal member is assembled as a constituent member, and a VGS type turbo incorporating the exhaust guide assembly. It is a perspective view (b) of a charger. 低温浸炭処理または低温浸窒処理を施した際に、鋼材に生じる浸入型原子誘起転位の様子を観察した透過電子顕微鏡写真である。It is the transmission electron microscope photograph which observed the mode of the penetration type atom induced dislocation which arises in steel materials, when low-temperature carburizing processing or low-temperature nitriding processing was performed. 低温浸炭後に擬鋭敏化処理を施した表面改質層のＦＥ−ＳＥＭによる断面組織写真である（原倍率×5,000 ）。It is the cross-sectional structure | tissue photograph by FE-SEM of the surface modification layer which gave the pseudo-sensitization process after low temperature carburizing (original magnification x5,000). 低温浸炭後に擬鋭敏化処理を施した表面改質層中の析出物のＴＥＭ像である（原倍率×800,000 ）。It is a TEM image of the deposit in the surface modification layer which performed the pseudo-sensitization process after low temperature carburizing (original magnification x800,000). 図６の析出物の制限視野電子線回析像とＥＤＸ定性分析を併せ示す説明図である。It is explanatory drawing which shows the restricted-field electron diffraction image and EDX qualitative analysis of the precipitate of FIG. 新材料を低温浸炭した後、更に擬鋭敏化処理を施した表層断面のＥＰＭＡライン分析結果を光顕組織とともに併せ示す説明図である。It is explanatory drawing which shows the EPMA line analysis result of the surface layer cross section which gave the pseudo sensitization process after low-temperature carburizing of a new material with a light microscope structure | tissue. 図８の状態に更に逆拡散処理を施した表層断面のＥＰＭＡライン分析結果を光顕組織とともに併せ示す説明図である。It is explanatory drawing which shows together the EPMA line analysis result of the surface layer cross section which performed the reverse diffusion process further in the state of FIG. 新材料及び規格材(SUS310S) の結晶粒界鋭敏化を示す写真である。It is a photograph which shows the grain boundary sensitization of a new material and a standard material (SUS310S). 新材料及び規格材(SUS310S) のσ金属間化合物脆化層の生成程度を示す写真である。It is a photograph which shows the production | generation degree of (sigma) intermetallic compound embrittlement layer of a new material and a standard material (SUS310S). 擬鋭敏化Ｃ曲線を示す半模式図である。It is a semi-schematic diagram showing a pseudo-sensitized C curve. 新材料に低温浸炭処理を施した表層断面のＥＰＭＡライン分析結果を光顕組織とともに併せ示す説明図である。It is explanatory drawing which shows the EPMA line analysis result of the surface layer cross section which gave the low temperature carburizing process to the new material with the optical microscope structure. 「新材料」に浸炭処理を施した材料表面と、「新材料」に浸炭処理したのち更に擬鋭敏化処理を行った材料表面とのビッカース硬さの温度依存性を示すグラフであり、表面改質を施していない「新材料」及び規格材(SUS310S) の場合も併せ示したグラフである。It is a graph showing the temperature dependence of Vickers hardness between a material surface that has been carburized to “new material” and a material surface that has been carburized to “new material” and then subjected to pseudo-sensitization treatment. This graph also shows the case of “new material” and standard material (SUS310S) that have not been subjected to quality. 「新材料」に低温浸炭／浸窒処理を施した材料の高温摩擦摩耗試験結果を示す表である。It is a table | surface which shows the high temperature friction wear test result of the material which performed the low temperature carburizing / nitrocarburizing process to "new material". 「新材料」に低温浸炭／浸窒処理を施した材料の連続高温酸化試験結果を示す表である。It is a table | surface which shows the continuous high-temperature oxidation test result of the material which performed the low temperature carburizing / nitriding treatment to "new material".

１ 可変翼
２ タービンフレーム
３ 可変機構
１１ 翼部
１２ 軸部
１３ テーパ部
１４ 鍔部
１５ 基準面
２１ フレームセグメント
２２ 保持部材
２３ フランジ部
２３Ａ フランジ部（小）
２３Ｂ フランジ部（大）
２４ ボス部
２５ 軸受孔
２６ カシメピン
２７ ピン孔
３１ 回動部材
３２ 伝達部材
３２Ａ 駆動要素
３２Ｂ 受動要素
３３ リング
Ａ 排気ガイドアッセンブリ
Ｇ 排気ガス
ｈ 翼幅
Ｔ 排気タービン DESCRIPTION OF SYMBOLS 1 Variable wing | blade 2 Turbine frame 3 Variable mechanism 11 wing | blade part 12 axial part 13 taper part 14 collar part 15 reference plane 21 frame segment 22 holding member 23 flange part 23A flange part (small)
23B Flange (Large)
24 Boss portion 25 Bearing hole 26 Caulking pin 27 Pin hole 31 Rotating member 32 Transmission member 32A Drive element 32B Passive element 33 Ring A Exhaust guide assembly G Exhaust gas h Blade width T Exhaust turbine

Claims (12)

少なくともクロムを含有する金属素材を被処理材とし、
この被処理材をフッ素系ガス雰囲気下で加熱保持してフッ化処理を行い、
その後、またはこのフッ化処理中に、処理温度を400 〜600 ℃に設定した低温浸炭処理および／または浸窒処理を施すか、あるいは減圧下の低温プラズマ浸炭処理および／または低温プラズマ浸窒処理を施して、結晶粒内に多発せしめた浸入型原子誘起転位を炭化物または窒化物の生成核とする擬鋭敏化処理を行い、最終的に被処理材の断面表層部に、クロム炭化物またはクロム窒化物を微細且つ均一に出現させて、被処理材の表面硬化とカバリング効果を図り、被処理材の耐高温摩擦摩耗特性を向上させるようにしたことを特徴とする高温耐久性を高めたナノ表面改質方法。
A metal material containing at least chromium is used as the material to be treated.
This material to be treated is heated and held in a fluorine gas atmosphere to perform fluorination treatment,
After or during this fluorination treatment, low-temperature carburization and / or nitrocarburization with a treatment temperature set to 400 to 600 ° C. is performed, or low-temperature plasma carburization and / or low-temperature plasma nitridation under reduced pressure. Applied, and pseudo-sensitization treatment using the intrusion-type atom-induced dislocations frequently generated in the crystal grains as carbide or nitride formation nuclei, and finally the chromium carbide or chromium nitride on the cross-sectional surface layer of the material to be treated Nano surface modification with improved high-temperature durability, characterized by improving the high-temperature friction and wear resistance of the material to be treated by improving the surface hardening and covering effect of the material to be treated. Quality method.
前記結晶粒内に多発せしめる浸入型原子誘起転位は、10 8 〜1015/cm2の転位密度で生じさせるものであり、
また前記擬鋭敏化処理を被処理材に施すにあたっては、処理温度を550 〜850 ℃に設定するようにしたことを特徴とする請求項１記載の高温耐久性を高めたナノ表面改質方法。
Interstitial atoms induced dislocations allowed to multiple prior Symbol crystal grains, which causes in the dislocation density of 10 8 ~10 15 / cm 2,
2. The nano-surface modification method with improved high-temperature durability according to claim 1, wherein the treatment temperature is set to 550 to 850 [deg.] C. when the pseudo-sensitization treatment is performed on the material to be treated.
前記擬鋭敏化処理後の被処理材には、擬鋭敏化処理によって生じ得る断面表層部のクロム欠乏層中のクロム量を補填するために、当該欠乏層より内部の被処理材マトリックスから、逆濃度勾配を利用して固溶状態のクロム原子をクロム欠乏層に移動させる逆拡散処理を行い、被処理材の耐高温酸化特性を向上させるようにしたことを特徴とする請求項１または２記載の高温耐久性を高めたナノ表面改質方法。
In order to compensate for the amount of chromium in the chromium-deficient layer of the cross-sectional surface layer portion that may be generated by the pseudo-sensitization treatment, the material to be treated after the pseudo-sensitization treatment is reversed from the material matrix inside the deficient layer. 3. The high-temperature oxidation resistance of the material to be treated is improved by performing a reverse diffusion treatment in which solid solution chromium atoms are moved to a chromium-deficient layer using a concentration gradient. Nano surface modification method with improved high temperature durability.
前記逆拡散処理を被処理材に施すにあたっては、処理温度を850 〜950 ℃に設定するようにしたことを特徴とする請求項３記載の高温耐久性を高めたナノ表面改質方法。
4. The nano-surface modification method with improved high-temperature durability according to claim 3, wherein when the reverse diffusion treatment is performed on the material to be treated, the treatment temperature is set to 850 to 950 ° C.
前記擬鋭敏化処理後の被処理材には、レアアースメタル元素を導入する添加処理を行い、擬鋭敏化処理によって生じ得るクロム欠乏層の存在に基づく耐高温酸化特性の劣化を回復させるようにしたことを特徴とする請求項１または２記載の高温耐久性を高めたナノ表面改質方法。
The material to be treated after the pseudo-sensitization treatment is subjected to an addition treatment for introducing a rare earth metal element so as to recover the deterioration of the high-temperature oxidation resistance due to the presence of a chromium-deficient layer that can be caused by the pseudo-sensitization treatment. 3. The nano-surface modification method with improved high temperature durability according to claim 1 or 2.
前記被処理材に導入するレアアースメタル元素の添加量は、0.01〜0.5 ％であることを特徴とする請求項５記載の高温耐久性を高めたナノ表面改質方法。
6. The nano-surface modification method with improved high-temperature durability according to claim 5 , wherein the amount of rare earth metal element added to the material to be treated is 0.01 to 0.5%.
前記被処理材には、事前に塑性加工を施し、塑性加工転位を導入してから、順次以降の処理を行うようにしたことを特徴とする請求項１、２、３、４、５または６記載の高温耐久性を高めたナノ表面改質方法。
7. The material to be processed is subjected to plastic processing in advance and plastic processing dislocation is introduced, and then subsequent processing is sequentially performed. A nano-surface modification method with improved high-temperature durability as described.
前記塑性加工転位は、相当真歪εが0.1 〜εu （εu ；相当均一真歪）で被処理材に導入されることを特徴とする請求項７記載の高温耐久性を高めたナノ表面改質方法。
The high-temperature durability according to claim 7, wherein the plastic working dislocation is introduced into the material to be processed with an equivalent true strain ε of 0.1 to ε u (ε u ; equivalent uniform true strain). Nano surface modification method.
前記被処理材には、低温浸炭処理と浸窒処理との双方を施すことを特徴とする請求項１、２、３、４、５、６、７または８記載の高温耐久性を高めたナノ表面改質方法。
9. The nano material with improved high-temperature durability according to claim 1, wherein both the low-temperature carburizing treatment and the nitriding treatment are performed on the material to be treated. Surface modification method.
前記被処理材は、
Ｃ：0.02〜0.07 mass ％、Si：0.2 〜1.7 mass％、Mn：5.0mass ％以下、Ni：12.0〜15.0 mass ％、Cr：22.0〜25.0 mass ％、Cu：0.5 〜4.5 mass％、Ｎ：0.05〜0.17 mass ％、且つ、Ca、REM のうちの１種または２種を0.0005〜0.05mass％含有し、残部がFe及び不可避的不純物から成り、下記(1) 式で定義されるNi当量が30.0以上、下記(2) 式で定義されるδcal が0.5 〜8.0 、下記(3) 式で定義されるHvが 120〜160 となるオーステナイト系耐熱素材が適用されることを特徴とする請求項１、２、３、４、５、６、７、８または９記載の高温耐久性を高めたナノ表面改質方法。
記
Ni当量＝Ni＋0.65Cr＋1.05Mn＋0.35Si＋0.6Cu ＋25.2Ｃ＋12.6Ｎ …(1)
δcal ＝3.2 (1.5Si＋Cr) −2.5(30Ｃ＋30Ｎ＋Ni＋0.5Mn ＋0.3Cu)−24.7 …(2)
Hv ＝87Ｃ＋ 2Si−1.2Mn −6.7Ni ＋2.7Cr −2.6Cu ＋690 Ｎ＋88 …(3)
The material to be treated is
C: 0.02 to 0.07 mass%, Si: 0.2 to 1.7 mass%, Mn: 5.0 mass% or less, Ni: 12.0 to 15.0 mass%, Cr: 22.0 to 25.0 mass%, Cu: 0.5 to 4.5 mass%, N: 0.05 ~ 0.17 mass%, and one or two of Ca and REM are contained in 0.0005 to 0.05 mass%, the balance consists of Fe and inevitable impurities, and the Ni equivalent defined by the following formula (1) is 30.0 As described above, an austenitic heat-resistant material in which δcal defined by the following formula (2) is 0.5 to 8.0 and Hv defined by the following formula (3) is 120 to 160 is applied. 2. The nano-surface modification method with enhanced high-temperature durability according to 2, 3, 4, 5, 6, 7, 8, or 9.
Record
Ni equivalent = Ni + 0.65Cr + 1.05Mn + 0.35Si + 0.6Cu + 25.2C + 12.6N (1)
δcal = 3.2 (1.5Si + Cr) -2.5 (30C + 30N + Ni + 0.5Mn + 0.3Cu) -24.7… (2)
Hv = 87C + 2Si-1.2Mn-6.7Ni + 2.7Cr-2.6Cu + 690 N + 88 (3)
金属部材の表面に表面改質処理が施され、この処理によって部材の高温耐久性を向上させた金属部材であって、この部材には前記請求項１、２、３、４、５、６、７、８、９または１０記載のナノ表面改質方法が施されて成ることを特徴とする金属部材。
 Table Men'aratameshitsu treatment to the surface of the metal member is subjected to a metal member having improved high-temperature durability of the member by the process, the claims 1,2,3,4,5,6 This member A metal member characterized by being subjected to the nano-surface modification method according to claim 7, 8, 9 or 10.
排気タービンの外周位置に、複数の可変翼が回動自在に設けられ、
エンジンから排出された比較的少ない排気ガスを、この可変翼によって適宜絞り込み、排気ガスの速度を増幅させ、排気ガスのエネルギで排気タービンを回し、排気タービンに直結されたコンプレッサで自然吸気以上の空気をエンジンに送り込み、低速回転時であってもエンジンが高出力を発揮できるようにしたＶＧＳタイプターボチャージャの排気ガイドアッセンブリにおいて、
この排気ガイドアッセンブリの構成部材には、前記請求項１１記載の金属部材が適用されて成るものであり、ナノ表面改質の際には事前に適宜の形状に塑性加工されて成ることを特徴とする、ＶＧＳタイプターボチャージャにおける排気ガイドアッセンブリ。 A plurality of variable blades are rotatably provided at the outer peripheral position of the exhaust turbine,
A relatively small amount of exhaust gas discharged from the engine is appropriately throttled by the variable blades, the speed of the exhaust gas is amplified, the exhaust turbine is rotated by the energy of the exhaust gas, and the air directly above the natural intake air by the compressor directly connected to the exhaust turbine In the exhaust guide assembly of the VGS type turbocharger that allows the engine to exhibit high output even at low speed rotation,
The structural member of the exhaust guide assembly is formed by applying the metal member according to claim 11 and is plastically processed into an appropriate shape in advance at the time of nano surface modification. Exhaust guide assembly for VGS type turbocharger.
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