JP2013087351A - Nitride metal member and method for manufacturing the same - Google Patents
Nitride metal member and method for manufacturing the same Download PDFInfo
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本発明は、従来にない窒化層を有する窒化金属部材およびその製造方法に関する。 The present invention relates to an unconventional metal nitride member having a nitride layer and a method for manufacturing the same.
金属部材の強度、耐食性、耐摩耗性等を向上させるために、種々の表面改質処理がなされる。代表的な表面改質処理の一つに窒化処理がある。この方法として、ガス窒化法、ガス軟窒化法、塩浴窒化法、放電プラズマ窒化（イオン窒化）法等が一般的である。その一つである放電プラズマ窒化に関する記載が下記の非特許文献１〜３にある。 In order to improve the strength, corrosion resistance, wear resistance and the like of the metal member, various surface modification treatments are performed. One typical surface modification treatment is nitriding treatment. As this method, a gas nitriding method, a gas soft nitriding method, a salt bath nitriding method, a discharge plasma nitriding (ion nitriding) method or the like is generally used. Non-patent documents 1 to 3 below describe discharge plasma nitridation as one of them.
それらの窒化方法とは異なり、チタン系基材へレーザ光を照射して窒化処理を行う提案が、例えば下記の特許文献１および非特許文献４にある。 Unlike those nitriding methods, there are proposals for nitriding by irradiating a titanium-based substrate with laser light, for example, in Patent Document 1 and Non-Patent Document 4 below.
ガス窒化法、非特許文献１〜３にある放電プラズマ窒化法等は、いずれも金属基材の表面から窒素を導入して内部へ拡散させることにより窒化層を形成する方法である。こうして得られる窒化層は、その形成過程に由来して、必ず、窒素濃度が最表面から内部にかけて少なくなる窒素濃度傾斜層となる。このような窒素濃度傾斜層は、消耗環境下において加速的に消耗が進行し短寿命となり得るため、耐摩耗性部材等には不向きである。 The gas nitriding method, the discharge plasma nitriding method described in Non-Patent Documents 1 to 3, and the like are methods for forming a nitrided layer by introducing nitrogen from the surface of a metal substrate and diffusing it inside. The nitride layer obtained in this way is always a nitrogen concentration gradient layer in which the nitrogen concentration decreases from the outermost surface to the inside due to the formation process. Such a nitrogen concentration gradient layer is not suitable for a wear-resistant member or the like because it gradually accelerates the exhaustion under a consumable environment and can have a short life.
さらに上記の窒化方法では、長時間の高温処理が必要なため、金属基材の変形、窒化表面粗さの悪化、窒化組織の粗大化等を生じ易い。放電プラズマ窒化法の場合、そのような課題が少ないが、特別な処理設備（真空チャンバー等）や工程が必要となり生産性も低い。 Furthermore, since the above nitriding method requires high-temperature treatment for a long time, the metal substrate is likely to be deformed, the nitrided surface roughness is deteriorated, and the nitrided structure is coarsened. In the case of the discharge plasma nitriding method, there are few such problems, but special processing equipment (such as a vacuum chamber) and processes are required, and productivity is low.
一方、特許文献１では、連続発振させたＣＯ２レーザを窒素ガス雰囲気中にあるチタン系基材へ照射して、十分に加熱したチタン系基材と窒素ガスを反応させることにより窒化層を形成している。非特許文献４でも、同様な方法で窒化層を形成している。このような窒化方法によれば、局所的な窒化層が短時間で形成可能である。 On the other hand, in Patent Document 1, a nitride layer is formed by irradiating a titanium base material in a nitrogen gas atmosphere with a continuously oscillated CO 2 laser and reacting the sufficiently heated titanium base material with nitrogen gas. doing. Also in Non-Patent Document 4, the nitride layer is formed by the same method. According to such a nitriding method, a local nitrided layer can be formed in a short time.
ところが、これらの方法では、レーザ光を照射した部分が一時的に半溶融状態または溶融状態となるため、再凝固してできた窒化層は表面粗さが粗く、組織が粗大なものとなり易い。また、上記のレーザ光を用いた窒化方法は、適用可能な基材が限られ、例えば、鉄系基材に適用しても有効な窒化層を形成することは困難である。 However, in these methods, the portion irradiated with the laser beam is temporarily in a semi-molten state or a molten state, and thus the nitrided layer formed by resolidification tends to have a rough surface and a coarse structure. In addition, the above-described nitriding method using laser light has limited applicable base materials, and for example, it is difficult to form an effective nitrided layer even when applied to an iron-based base material.
本発明はこのような事情に鑑みて為されたものであり、従来とは形態が全く異なる新たな窒化層を有する窒化金属部材と、その製造方法を提供することを目的とする。 The present invention has been made in view of such circumstances, and an object of the present invention is to provide a metal nitride member having a new nitride layer that is completely different from the conventional one, and a method for manufacturing the metal nitride member.
本発明者は、上記の課題を解決すべく鋭意研究し、試行錯誤を重ねた結果、近紫外ナノ秒パルスレーザを金属基材の被処理部へ照射することにより、全体にわたり窒素濃度が均一的で、微細な結晶組織からなる高特性の窒化層を得ることに成功した。この成果を発展させることにより、以降に述べる本発明を完成するに至った。 As a result of intensive studies to solve the above-mentioned problems and repeated trial and error, the present inventor irradiates the target portion of the metal substrate with a near-ultraviolet nanosecond pulse laser so that the nitrogen concentration is uniform throughout. Thus, we succeeded in obtaining a high-quality nitrided layer consisting of a fine crystal structure. By developing this result, the present invention described below has been completed.
《窒化金属部材》
（１）本発明の窒化金属部材は、窒化可能な金属基材からなり、該金属基材の表面部に窒化層を有する窒化金属部材であって、前記窒化層は、前記金属基材の最表面側から測定して窒化層深さの９０％に相当する位置における窒素濃度（原子％）である深層濃度が、該窒化層深さの１０％に相当する位置における窒素濃度（原子％）である浅層濃度よりも、大きいかまたは同等であることを特徴とする。
《Metal nitride member》
(1) The metal nitride member of the present invention is a metal nitride member made of a metal base material that can be nitrided, and having a nitride layer on the surface of the metal base material. The deep layer concentration, which is the nitrogen concentration (atomic%) at the position corresponding to 90% of the nitrided layer depth as measured from the surface side, is the nitrogen concentration (atomic%) at the position corresponding to 10% of the nitrided layer depth. It is characterized by being greater than or equal to a certain shallow layer concentration.
（２）本発明の窒化金属部材は、先ず、その窒化層中における窒素分布が、従来の窒化層とは全く異なっている。従来の窒化層は、最表層付近に窒素が集中し、内部へ向かうほど窒素が急減する窒素分布を示す。これに対して本発明に係る窒化層は、最表面近傍の浅い部分（浅層部）のみならず、内部の深い部分（深層部）でも窒素が十分に存在する窒素分布を示す。つまり本発明に係る窒化層は、窒素濃度が全体的にほぼ均一であるか、従来の窒化層とは全く逆に、浅層濃度が深層濃度より高いという窒素分布を示す。このため本発明に係る窒化層は、内部でも窒化組織が均質的で安定しており、窒化層内のどの部分が露出しても、安定した特性が発現され得る。この結果、例えば、窒化層の摩耗による窒化金属部材の寿命予測等を適切に行うことが可能となる。 (2) In the metal nitride member of the present invention, first, the nitrogen distribution in the nitride layer is completely different from the conventional nitride layer. The conventional nitride layer has a nitrogen distribution in which nitrogen is concentrated in the vicinity of the outermost layer, and nitrogen decreases sharply toward the inside. On the other hand, the nitride layer according to the present invention exhibits a nitrogen distribution in which nitrogen is sufficiently present not only in a shallow portion (shallow layer portion) near the outermost surface but also in a deep portion (deep layer portion) inside. That is, the nitride layer according to the present invention exhibits a nitrogen distribution in which the nitrogen concentration is substantially uniform as a whole or the shallow layer concentration is higher than the deep layer concentration, contrary to the conventional nitride layer. For this reason, the nitrided layer according to the present invention has a uniform and stable nitrided structure even in the interior, and a stable characteristic can be exhibited no matter what part of the nitrided layer is exposed. As a result, for example, it is possible to appropriately predict the lifetime of the metal nitride member due to wear of the nitride layer.
（３）本明細書では、本発明に係る窒化層が有する特長的な窒素分布を明確に特定するために、敢えて、窒化層の特定位置における窒素濃度（浅層濃度と深層濃度）を便宜的に導入した。浅層濃度および深層濃度の特定位置を、それぞれ窒化層深さの１０％と９０％に相当する位置としたのは、窒化層の両端部における窒素濃度のばらつきを排除して、本発明に係る窒化層を安定して特定できるようにするためである。 (3) In this specification, in order to clearly identify the characteristic nitrogen distribution of the nitride layer according to the present invention, the nitrogen concentration (shallow layer concentration and deep layer concentration) at a specific position of the nitride layer is intentionally deliberate. Introduced. The specific positions of the shallow layer concentration and the deep layer concentration are the positions corresponding to 10% and 90% of the nitrided layer depth, respectively, by eliminating the variation in nitrogen concentration at both ends of the nitrided layer. This is because the nitride layer can be identified stably.
「窒素濃度（原子％）」は、電子線マイクロアナライザー（ＥＰＭＡ）の解析結果に基づき特定した。「窒化層深さ」は、窒化金属部材の表面部に形成された窒化層の最表面から測定して、その窒素濃度が０．１原子％となる境界点までの距離（厚さ）である。 The “nitrogen concentration (atomic%)” was specified based on the analysis result of an electron beam microanalyzer (EPMA). “Nitride layer depth” is the distance (thickness) to the boundary point at which the nitrogen concentration is 0.1 atomic% as measured from the outermost surface of the nitride layer formed on the surface portion of the metal nitride member. .
浅層濃度と深層濃度が「同等」とは、上述した窒化層中の特定位置で、各窒素濃度がほぼ等しいことを意味する。敢えて厳密に規定するなら、「同等」とは、浅層濃度と深層濃度の窒素濃度差が５原子％以内とすればよい。勿論、窒素濃度差が３原子％以内さらには２原子％以内であると、窒化層内の窒素分布が全体的により均一であるといい得る。 “Equivalent” between the shallow layer concentration and the deep layer concentration means that each nitrogen concentration is substantially equal at the specific position in the nitride layer described above. If stipulated strictly, “equivalent” means that the nitrogen concentration difference between the shallow layer concentration and the deep layer concentration is within 5 atomic%. Of course, if the difference in nitrogen concentration is within 3 atomic% or even within 2 atomic%, it can be said that the nitrogen distribution in the nitride layer is more uniform overall.
（４）本発明に係る窒化層深さの上下限値は特に問わない。窒化層によって所望する特性が安定して発現される範囲ならよい。窒化層深さが１μｍ以下でも十分な場合もあるが、例えば、耐摩耗性部材に用いる窒化層なら、窒化層深さは１μｍ以上、１０μｍ以上、５０μｍ以上さらには８０μｍ以上であると好ましい。逆に窒化層深さは、窒化層の最表面（窒化面）を研磨等する場合を考慮しても、１０００μｍ以下さらには５００μｍ以下あれば、通常は十分である。 (4) The upper and lower limits of the nitrided layer depth according to the present invention are not particularly limited. Any range in which desired characteristics are stably expressed by the nitride layer is acceptable. A nitride layer depth of 1 μm or less may suffice, but for example, in the case of a nitride layer used for an abrasion resistant member, the nitride layer depth is preferably 1 μm or more, 10 μm or more, 50 μm or more, and more preferably 80 μm or more. On the other hand, the depth of the nitride layer is usually sufficient if it is 1000 μm or less, further 500 μm or less, even when the outermost surface (nitrided surface) of the nitride layer is polished.
《窒化金属部材の製造方法》
（１）上述した窒化金属部材は、例えば、次のような本発明の製造方法により得られる。すなわち、本発明の窒化金属部材の製造方法は、窒素含有雰囲気下にある窒化可能な金属基材の被処理部へ、該被処理部に対して高エネルギービームを相対移動させつつ照射することにより、該被処理部でアブレーションを生じさせると共に該被処理部の近傍にプラズマ化した窒素を生成させる照射工程を備え、上述した窒化金属部材が得られることを特徴とする。
<< Production Method of Metal Nitride Member >>
(1) The above-described metal nitride member can be obtained, for example, by the following production method of the present invention. That is, the method for producing a metal nitride member of the present invention irradiates a target portion of a metal base capable of nitriding in a nitrogen-containing atmosphere while moving a high energy beam relative to the target portion. The above-mentioned metal nitride member is obtained by providing an irradiation step of generating ablation in the portion to be processed and generating nitrogen in the vicinity of the portion to be processed.
（２）本発明の製造方法により上述した窒化金属部材が得られる理由は必ずしも定かではないが、現状では次のように考えられる。高エネルギービームが金属基材の被処理部へ適切に照射されると、金属基材の被処理部ではアブレーションが生じ得る。このアブレーションにより、被処理部にあった金属基材を構成する原子等が、気化、蒸発、蒸散、飛散等して放出される。こうして放出された粒子（適宜「放出粒子」という。）は、原子、分子、イオン、電子、光子、ラジカル、クラスター等の様々な形態をとり得る。このような放出粒子が被処理部の近傍にある雰囲気ガス（窒素等）に何らかの影響を与える。そして放出粒子と活性な窒素（単に「活性窒素」という。）の混合状態からなる反応場が、アブレーションを生じた被処理部（適宜「アブレーション部」という。）またはその近傍に生成され得る。 (2) The reason why the above-described metal nitride member can be obtained by the production method of the present invention is not necessarily clear, but at present, it is considered as follows. When the high energy beam is appropriately applied to the processing portion of the metal base, ablation may occur in the processing portion of the metal base. By this ablation, atoms or the like constituting the metal substrate in the processing target are released by vaporization, evaporation, evaporation, scattering, or the like. The particles thus released (referred to as “emitted particles” where appropriate) can take various forms such as atoms, molecules, ions, electrons, photons, radicals, and clusters. Such emitted particles have some influence on the atmospheric gas (nitrogen or the like) in the vicinity of the portion to be processed. A reaction field consisting of a mixed state of emitted particles and active nitrogen (simply referred to as “active nitrogen”) can be generated at or near the part to be treated (referred to as “ablation part” where ablation occurs).
高エネルギービームの照射域が金属基材の被処理部上を移動することにより、上記の現象が次々とほぼ連続的に生じ、被処理部およびその近傍は、反応場を生成する放出粒子および活性窒素が多数存在した状態となる。 The above-mentioned phenomenon occurs almost continuously one after another as the irradiation area of the high energy beam moves on the treated part of the metal substrate, and the treated part and the vicinity thereof are emitted particles and actives that generate a reaction field. A large amount of nitrogen is present.
活性窒素は、金属基材のアブレーション部またはその近傍へ浸入して窒化物または窒素固溶体を形成するか、または放出粒子と結合してアブレーション部へ充填等されていく。このような現象が繰り返されることにより、内部深くまで窒素が十分に導入された窒化層が形成されたと考えられる。 The active nitrogen penetrates into or near the ablation part of the metal substrate to form a nitride or nitrogen solid solution, or is combined with the released particles and filled into the ablation part. By repeating such a phenomenon, it is considered that a nitride layer in which nitrogen was sufficiently introduced deep inside was formed.
なお、本発明の製造方法では、従来の窒化方法とは異なり、窒化層の形成にアブレーションを利用しているため、金属基材や窒化層には殆ど熱的影響が及ばない。従って本発明の製造方法によれば、金属基材の変形、表面粗さの悪化、組織の粗大化等はほとんど生じない。またアブレーションを利用する場合、金属基材の材質にほとんど依存せずに、短時間内に深い窒化層が形成され得る。従って本発明の製造方法によれば、深い窒化層を形成する場合でも、金属基材の材質に関する選定自由度が非常に大きく、特定の窒化処理を長時間行う必要ない。 In the manufacturing method of the present invention, unlike the conventional nitriding method, ablation is used for forming the nitride layer, so that the metal base material and the nitride layer are hardly affected by heat. Therefore, according to the production method of the present invention, the deformation of the metal substrate, the deterioration of the surface roughness, the coarsening of the structure and the like hardly occur. When ablation is used, a deep nitride layer can be formed within a short time without depending on the material of the metal substrate. Therefore, according to the manufacturing method of the present invention, even when a deep nitrided layer is formed, the degree of freedom in selecting the material of the metal substrate is very large, and it is not necessary to perform a specific nitriding treatment for a long time.
（３）こうして形成される窒化層は、従来のＣＯ２レーザーを用いて得られる（半）溶融後の凝固組織からなる窒化層とは明らかに異なり、非常に微細な結晶組織でもある。具体的にいうと、本発明に係る窒化層（窒化組織）は、平均結晶粒径が１０μｍ以下、１μｍ以下さらには４００ｎｍ以下となり得る。平均結晶粒径の下限値は問わないが、生産コストや品質安定化等の点で、例えば、１ｎｍ以上さらには２０ｎｍ以上としてもよい。 (3) The nitride layer thus formed is clearly different from a nitride layer composed of a (semi) melted solidified structure obtained by using a conventional CO 2 laser, and has a very fine crystal structure. Specifically, the nitride layer (nitriding structure) according to the present invention may have an average crystal grain size of 10 μm or less, 1 μm or less, or even 400 nm or less. The lower limit value of the average crystal grain size is not limited, but it may be, for example, 1 nm or more, further 20 nm or more in terms of production cost, quality stabilization, and the like.
本明細書でいう「平均結晶粒径」は次のようにして特定した。先ず、組織の断面を観察し、認められる粒子の断面形状を楕円と仮定して、その長軸と短軸の平均値を一つの結晶粒径とする。次に、観察している組織断面中から無作為に抽出した５点について算出した結晶粒径の単純平均（相加平均）を本明細書でいう平均結晶粒径とした。 The “average crystal grain size” in the present specification was specified as follows. First, the cross section of the structure is observed, the cross sectional shape of the recognized particles is assumed to be an ellipse, and the average value of the major axis and the minor axis is defined as one crystal grain size. Next, the simple average (arithmetic average) of crystal grain sizes calculated for five points randomly extracted from the observed cross section of the tissue was used as the average crystal grain size referred to in this specification.
（４）本発明の製造方法では、高エネルギー（収束）ビームを用いているため、従来の窒化方法では困難であった局所的な窒化や微細な窒化も可能となる。例えば、幅１０μｍ以下、１μｍ以下さらには０．５μｍ以下の窒化層を形成することも可能である。 (4) In the manufacturing method of the present invention, since a high energy (convergent) beam is used, local nitridation and fine nitridation that are difficult with the conventional nitriding method are possible. For example, a nitride layer having a width of 10 μm or less, 1 μm or less, or 0.5 μm or less can be formed.
また、形成される窒化層の形態は、高エネルギービームの照射域の軌跡により定まる。高エネルギービームの可動域に制限はないため、広狭を問わず、所望する形態の窒化層が形成され得る。窒化層の形成される被処理部は、平面に限らず種々の曲面でもよいし、曲線状（直線状を含む）でも点状（斑点状等の多数点状を含む）でもよい。さらに、高エネルギービームが到達する限り、被処理部は、窪んだ形状でも、奥まったところにあっても、アンダーカット的な形態でもよい。 In addition, the form of the nitride layer to be formed is determined by the locus of the irradiation area of the high energy beam. Since there is no limitation on the movable range of the high energy beam, a nitride layer having a desired form can be formed regardless of the width. The portion to be processed on which the nitride layer is formed is not limited to a flat surface, and may be various curved surfaces, a curved shape (including a straight line shape), or a point shape (including a multipoint shape such as a spot shape). Furthermore, as long as a high energy beam reaches | attains, a to-be-processed part may be a hollow shape, or it may exist in the back part, and may be an undercut form.
また窒化層は、高エネルギービームの照射域の軌跡上に形成されるため、窒化されていない非窒化層と混在させることも自在に調整できる。例えば、窒化層と非窒化層が交互に配置されたストライプ状や格子状の表面部を形成することも容易である。このように、窒化層と非窒化層が共存して金属基材の表面部に形成された改質組織を、本明細書ではテクスチャ組織という。 Further, since the nitride layer is formed on the locus of the irradiation region of the high energy beam, it can be freely adjusted to be mixed with a non-nitrided layer that is not nitrided. For example, it is easy to form a stripe-shaped or lattice-shaped surface portion in which nitrided layers and non-nitrided layers are alternately arranged. Thus, the modified structure formed in the surface part of the metal base material by coexisting the nitrided layer and the non-nitrided layer is referred to as a texture structure in this specification.
なお、窒化層やテクスチャ組織は、二次元的な形態に留まらず三次元的な形態でもよい。高エネルギービームの出力密度、ビーム径、焦点等を調整することにより、窒化層の幅や深さを、その形成位置に応じて容易に変化させ得る。さらに、処理後の表面をディンプル状にすることも容易である。このように本発明によれば、金属基材の形状や仕様等に応じて、最適な窒化層を自在に形成可能である。ちなみに、従来の窒化層深さは高々数十μｍ程度であるが、本発明の製造方法によれば、５０μｍ以上さらには１００μｍ以上の窒化層深さを得ることも容易である。 The nitride layer and the texture structure are not limited to a two-dimensional form, but may be a three-dimensional form. By adjusting the output density, beam diameter, focus, etc. of the high energy beam, the width and depth of the nitride layer can be easily changed according to the formation position. Furthermore, it is easy to make the surface after treatment a dimple. Thus, according to the present invention, an optimum nitride layer can be freely formed according to the shape and specifications of the metal substrate. Incidentally, the conventional nitride layer depth is about several tens of μm at most, but according to the manufacturing method of the present invention, it is easy to obtain a nitride layer depth of 50 μm or more, further 100 μm or more.
（５）「被処理部」は、高エネルギービームの照射が可能な部分である限り、外表面側でも内表面側でもよい。また、必ずしも金属基材の最表面には限られず、その内部も被処理部に含まれる。これらは、金属基材の「表面部」についても同様である。 (5) The “target portion” may be on the outer surface side or the inner surface side as long as it is a portion that can be irradiated with a high energy beam. Moreover, it is not necessarily restricted to the outermost surface of a metal base material, The inside is also contained in a to-be-processed part. The same applies to the “surface portion” of the metal substrate.
「高エネルギービーム」は、光線または電子線であって、金属基材をアブレーションするのに十分なエネルギーと、照射部周辺をプラズマ化させる強電界とを併せもつビームである。具体的には、レーザ、電子ビーム等である。 The “high energy beam” is a light beam or an electron beam, and has a sufficient energy for ablating the metal substrate and a strong electric field that turns the periphery of the irradiated portion into plasma. Specifically, a laser, an electron beam, or the like.
「窒素含有雰囲気」は、窒化源となる窒素（Ｎ）が分子レベルまたは原子レベルで存在し、アブレーションにより活性窒素が発生し得る雰囲気である。具体的には、窒素ガスのみからなる窒素ガス雰囲気、窒素ガスを含む混合窒素ガス雰囲気（例えば大気雰囲気）、窒素（Ｎ）の化合物（アンモニア等）を含む化合物ガス雰囲気等である。窒素含有雰囲気の気圧や温度は、適宜調整され得るが、本発明の製造方法によれば、常温大気圧雰囲気中でも所望する窒化層の形成が可能である。 The “nitrogen-containing atmosphere” is an atmosphere in which nitrogen (N) serving as a nitriding source exists at a molecular level or an atomic level, and active nitrogen can be generated by ablation. Specifically, a nitrogen gas atmosphere composed of only nitrogen gas, a mixed nitrogen gas atmosphere containing nitrogen gas (for example, air atmosphere), a compound gas atmosphere containing nitrogen (N) compound (such as ammonia), and the like. The pressure and temperature of the nitrogen-containing atmosphere can be adjusted as appropriate. However, according to the manufacturing method of the present invention, a desired nitride layer can be formed even in a normal temperature and atmospheric pressure atmosphere.
《その他》
特に断らない限り本明細書でいう「ｘ〜ｙ」は下限値ｘおよび上限値ｙを含む。本明細書に記載した種々の数値または数値範囲に含まれる任意の数値を、新たな下限値または上限値として「ａ〜ｂ」のような範囲を新設し得る。
<Others>
Unless otherwise specified, “x to y” in this specification includes a lower limit value x and an upper limit value y. Any numerical value included in various numerical values or numerical ranges described in the present specification can be newly established as a range such as “ab” as a new lower limit value or upper limit value.
本明細書で説明する内容は、本発明の窒化金属部材のみならず、その製造方法にも該当し得る。上述した本発明の構成要素に、本明細書中から任意に選択した一つまたは二つ以上の構成要素を付加し得る。この際、製造方法に関する構成要素は、プロダクトバイプロセスとして理解すれば物に関する構成要素ともなり得る。なお、いずれの実施形態が最良であるか否かは、対象、要求性能等によって異なる。 The contents described in this specification can be applied not only to the metal nitride member of the present invention but also to the manufacturing method thereof. One or two or more components arbitrarily selected from the present specification may be added to the above-described components of the present invention. At this time, the component related to the manufacturing method can be a component related to an object if understood as a product-by-process. Note that which embodiment is the best depends on the target, required performance, and the like.
《窒化金属部材》
（１）金属基材
本発明に係る金属基材は、窒化可能なものであれば、純金属でも合金でもよく、その種類や成分組成を問わない。「窒化可能」とは、導入された窒素が窒化物または窒素固溶体を形成して、金属基材の特性（硬さ等）が改善され得ることをいう。この際、窒素による改善の程度は問わない。金属基材は、例えば、鉄鋼材、ステンレス鋼材、チタン材、アルミニウム材等である。本発明の製造方法によれば、金属基材は高温環境下に曝されることなく窒化され得る。このため、高温処理される従来の窒化方法には不適であった金属基材も本発明の対象となる。
《Metal nitride member》
(1) Metal base material The metal base material according to the present invention may be a pure metal or an alloy as long as it can be nitrided, regardless of the type or composition of the components. “Nitrizable” means that the introduced nitrogen can form a nitride or nitrogen solid solution, and the properties (hardness, etc.) of the metal substrate can be improved. At this time, the degree of improvement by nitrogen does not matter. The metal substrate is, for example, a steel material, a stainless steel material, a titanium material, an aluminum material, or the like. According to the production method of the present invention, the metal substrate can be nitrided without being exposed to a high temperature environment. For this reason, the metal base material which was unsuitable for the conventional nitriding method processed at high temperature is also the object of the present invention.
鉄鋼材は、一般的な炭素鋼でも種々の合金元素を含む特殊鋼でもよい。本発明の製造方法によれば、合金元素を含まない鉄鋼材の表面部にも、優れた特性の窒化層が形成され得る。勿論、金属基材が、窒化鋼のように硬質な窒化物を形成し得るＡｌ、ＣｒまたはＭｏ等の合金元素を含んでもよい。 The steel material may be general carbon steel or special steel containing various alloy elements. According to the production method of the present invention, a nitride layer having excellent characteristics can be formed also on the surface portion of a steel material that does not contain an alloy element. Of course, the metal substrate may contain an alloy element such as Al, Cr, or Mo that can form a hard nitride such as nitrided steel.
ステンレス鋼材は、オーステナイト系ステンレス鋼、フェライト系ステンレス鋼、マルテンサイト系ステンレス鋼等のいずれでもよい。特に炭素を含まないオーステナイト系ステンレス鋼やフェライト系ステンレス鋼は、通常の熱処理による硬化があまり期待できないので、本発明に係る窒化層を形成する意義が大きい。 The stainless steel material may be any of austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, and the like. In particular, austenitic stainless steels and ferritic stainless steels that do not contain carbon are not expected to be hardened by ordinary heat treatment, and are therefore significant in forming the nitride layer according to the present invention.
ステンレス鋼材の最表面には、通常、厚さ数ｎｍ程度の緻密で化学的に安定なクロム系酸化物からなる不動態皮膜が形成されている。従来の窒化方法では、その不動態皮膜により窒素の導入が阻害されて窒化が容易ではなかった。しかし、本発明の製造方法によれば、高エネルギービームの照射によるアブレーションを利用しているため、不動態皮膜の破壊さらには被処理部への活性窒素の導入が容易である。従って本発明の製造方法によれば、特別な前処理や雰囲気制御等を行うまでもなく、良好な窒化層が容易に安定して形成され得る。 On the outermost surface of the stainless steel material, a passive film composed of a dense and chemically stable chromium-based oxide having a thickness of several nanometers is usually formed. In the conventional nitriding method, introduction of nitrogen is inhibited by the passive film, and nitriding is not easy. However, according to the production method of the present invention, since ablation by irradiation with a high energy beam is used, it is easy to destroy the passive film and introduce active nitrogen into the portion to be treated. Therefore, according to the manufacturing method of the present invention, a good nitride layer can be easily and stably formed without performing any special pretreatment or atmosphere control.
チタン材は、純チタンでもチタン合金でもよい。チタン合金は、α型チタン合金でも、β型チタン合金でも、α−β型チタン合金でもよい。チタン材へ窒化処理を施すと、非常に硬質な窒化チタンが形成され、特有な発色も生じる。 The titanium material may be pure titanium or a titanium alloy. The titanium alloy may be an α-type titanium alloy, a β-type titanium alloy, or an α-β-type titanium alloy. When the titanium material is subjected to nitriding treatment, very hard titanium nitride is formed, and a specific color is generated.
もっとも従来は、チタン材を７００℃以上の高温で長時間加熱して窒化していたため、生産性が低く、基材組織の粗大化等によりチタン材の機械的特性が劣化することがあった。本発明の製造方法によれば、金属基材のアブレーションと窒素のプラズマ化に基づき窒化がなされるため、チタン材への熱的影響は殆ど無く、従来のような不都合はない。つまり本発明の製造方法によれば、優れた特性の窒化金属部材を効率良く生産できる。 However, since the titanium material is conventionally nitrided by heating at a high temperature of 700 ° C. or higher for a long time, the productivity is low, and the mechanical properties of the titanium material may deteriorate due to coarsening of the base material structure or the like. According to the manufacturing method of the present invention, since nitriding is performed based on ablation of the metal base and conversion of nitrogen into plasma, there is almost no thermal influence on the titanium material, and there is no conventional inconvenience. That is, according to the manufacturing method of the present invention, a metal nitride member having excellent characteristics can be produced efficiently.
（２）窒化層
本発明に係る窒化層は、金属基材の窒素固溶体または金属基材中若しくは窒素固溶体中に窒化物が分散した複合組織体からなる。生成される窒化物の種類は金属基材の組成により異なるが、硬質な窒化物として、例えば、Ｆｅ系窒化物（Ｆｅ２Ｎ、Ｆｅ３Ｎ等）、Ｔｉ系窒化物（Ｔｉ２Ｎ、ＴｉＮ等）、Ｃｒ系窒化物、Ｖ系窒化物、Ｍｏ系窒化物、Ａｌ系窒化物などがある。
(2) Nitride layer The nitride layer according to the present invention comprises a nitrogen solid solution of a metal substrate or a composite structure in which a nitride is dispersed in a metal substrate or a nitrogen solid solution. The type of nitride produced varies depending on the composition of the metal substrate, but as hard nitride, for example, Fe-based nitride (Fe 2 N, Fe 3 N, etc.), Ti-based nitride (Ti 2 N, TiN) Etc.), Cr-based nitride, V-based nitride, Mo-based nitride, Al-based nitride and the like.
窒化層中の窒素濃度は、金属基材の組成、結晶構造などにより、自ずと理論的な上限値が定まる。逆にいえば、本発明に係る窒化層内の窒素濃度は、その理論的な上限値以内なら任意である。本発明の製造方法の場合、窒化の金属基材への導入方法が、従来のような表面拡散型ではないため、窒化層の深い部分にも相当量の窒素を導入できる。概していうと、本発明に係る窒化層中の窒素濃度は１〜５０原子％であり、浅層濃度と深層濃度に実質的な相違はない。例えば、鉄鋼材やステンレス鋼材の窒素濃度は１〜３３原子％であり、チタン材の窒素濃度は１〜５０原子％である。なお、本発明に係る窒化層の場合、窒素が均一的に分布しているため、従来の窒化層より平均的な窒素濃度または窒素総量が低くても、従来の窒化層以上の硬さを発揮し得る。 The theoretical upper limit of the nitrogen concentration in the nitride layer is naturally determined by the composition of the metal substrate, the crystal structure, and the like. In other words, the nitrogen concentration in the nitride layer according to the present invention is arbitrary as long as it is within the theoretical upper limit. In the case of the production method of the present invention, since the method of introducing nitriding into the metal substrate is not the conventional surface diffusion type, a considerable amount of nitrogen can be introduced into a deep portion of the nitride layer. Generally speaking, the nitrogen concentration in the nitride layer according to the present invention is 1 to 50 atomic%, and there is no substantial difference between the shallow layer concentration and the deep layer concentration. For example, the nitrogen concentration of steel materials and stainless steel materials is 1-33 atomic%, and the nitrogen concentration of titanium materials is 1-50 atomic%. In the case of the nitride layer according to the present invention, since nitrogen is uniformly distributed, even if the average nitrogen concentration or the total amount of nitrogen is lower than that of the conventional nitride layer, it exhibits hardness higher than that of the conventional nitride layer. Can do.
金属基材の表面部に形成される窒化層のパターン、窒化層の大きさ（幅、深さ等）、窒化層を構成する組織サイズ（平均結晶粒径等）については前述した通りである。 The pattern of the nitride layer formed on the surface portion of the metal substrate, the size (width, depth, etc.) of the nitride layer, and the structure size (average crystal grain size, etc.) constituting the nitride layer are as described above.
《窒化金属部材の製造方法》
（１）高エネルギービーム
高エネルギービームは、金属基材の被処理部でアブレーションを生じさせ、アブレーション部の周囲にある雰囲気ガスから活性窒素が生成される限り、その種類を問わない。高エネルギービームは、例えば、パルスレーザ、電子ビーム等である。
<< Production Method of Metal Nitride Member >>
(1) High energy beam The high energy beam may be of any type as long as it causes ablation at the portion to be treated of the metal substrate and active nitrogen is generated from the atmospheric gas around the ablation portion. The high energy beam is, for example, a pulse laser or an electron beam.
アブレーションを発生させるには、金属基材の被処理部へ、高いエネルギーを瞬時に付与する必要がある。つまり、アブレーションの閾値を超える高いエネルギー密度（フルエンス）をもつ高エネルギービームを、金属基材の被処理部へ照射する必要がある。このような高エネルギービームとして、短パルス幅のパルスレーザが好適である。 In order to generate ablation, it is necessary to instantaneously apply high energy to the processing target portion of the metal substrate. That is, it is necessary to irradiate the processing target portion of the metal substrate with a high energy beam having a high energy density (fluence) exceeding the ablation threshold. As such a high energy beam, a pulse laser with a short pulse width is suitable.
レーザ発振装置の出力や発振周波数等が一定なら、パルス幅が短いほど、フルエンスの高いレーザ光を被処理部へ照射できる。またパルス幅が短いと、その照射域外への熱拡散が抑制され、アブレーションの促進と共に金属基材への熱的影響の抑制を図れる。具体的にいうと、パルスレーザのパルス幅は、例えば、１０ｐｓ〜１００ｎｓさらには１〜５０ｎｓであると好ましい。パルス幅が過大ではアブレーションに必要なフルエンスが得難くなり、パルス幅が過小（例えば多光子吸収が生じる１５０ｆｓ程度）ではレーザ光によるエネルギーの付与形態が変化して、本発明に係る窒化に必要な反応場（窒化反応場）が形成されない可能性がある。 If the output, the oscillation frequency, etc. of the laser oscillation device are constant, the laser beam having a higher fluence can be irradiated to the processing portion as the pulse width is shorter. Moreover, when the pulse width is short, thermal diffusion outside the irradiation region is suppressed, and the thermal influence on the metal substrate can be suppressed while promoting ablation. Specifically, the pulse width of the pulse laser is preferably 10 ps to 100 ns, and more preferably 1 to 50 ns. If the pulse width is too large, it becomes difficult to obtain the fluence necessary for ablation, and if the pulse width is too small (for example, about 150 fs at which multiphoton absorption occurs), the form of energy application by the laser light changes, which is necessary for nitriding according to the present invention. There is a possibility that a reaction field (nitriding reaction field) is not formed.
パルスレーザの出力密度（適宜「レーザフルエンス」または単に「フルエンス」という。）でいえば、例えば、０．３ＭＷ／ｃｍ２〜３０ＧＷ／ｃｍ２さらには３ＭＷ／ｃｍ２〜３ＧＷ／ｃｍ２であると好ましい。フルエンスは窒化層深さに影響し、フルエンスが過小では十分な深さの窒化層が得難くなり、フルエンスが過大では金属基材への熱的影響が大きくなり好ましくない。ちなみに、フルエンスはレーザ出力をレーザスポット面積で除して求まる。 Speaking a pulsed laser power density (suitably referred to as "laser fluence" or simply "fluence".) For example, when 0.3MW / cm 2 ~30GW / cm 2 further is a 3MW / cm 2 ~3GW / cm 2 preferable. The fluence affects the depth of the nitride layer. If the fluence is too small, it is difficult to obtain a nitride layer having a sufficient depth. If the fluence is too large, the thermal influence on the metal substrate is increased, which is not preferable. By the way, the fluence is obtained by dividing the laser output by the laser spot area.
またパルスレーザは波長が短いほど、金属基材によるレーザ光の吸収率が高くなり、アブレーションの促進と非アブレーション部の変質抑制等が図られる。またパルスレーザの波長を適切に調整することにより、十分な窒化層深さをもつ窒化層の形成が容易となる。このようなパルスレーザの波長は、赤外域より短く、さらには可視域よりも短い紫外域（近紫外域を含む）内にあると好ましい。具体的にいうと、パルスレーザの波長は、７００ｎｍ以下、５５０ｎｍ以下さらには３８０ｎｍ以下であると好ましい。またパルスレーザの波長は、１９０ｎｍ以上さらには３２０ｎｍ以上であると好ましい。パルスレーザの波長が過小では、雰囲気ガスによるレーザの吸収が発生して好ましくない。 In addition, the shorter the wavelength of the pulse laser, the higher the absorption rate of the laser beam by the metal substrate, thereby promoting ablation and suppressing alteration of the non-ablation part. In addition, by appropriately adjusting the wavelength of the pulse laser, a nitride layer having a sufficient nitride layer depth can be easily formed. The wavelength of such a pulse laser is preferably in the ultraviolet region (including the near ultraviolet region) shorter than the infrared region and further shorter than the visible region. Specifically, the wavelength of the pulse laser is preferably 700 nm or less, 550 nm or less, and further 380 nm or less. The wavelength of the pulse laser is preferably 190 nm or more, more preferably 320 nm or more. When the wavelength of the pulse laser is too small, the absorption of the laser by the atmospheric gas occurs, which is not preferable.
このようなパルスレーザの具体例として、例えば、Ｆ２（波長１５７ｎｍ）、ＡｒＦ（波長１９３ｎｍ）、ＫｒＦ（波長２４８ｎｍ）、ＸｅＣｌ（波長３０８ｎｍ）、ＸｅＦ（波長３５１ｎｍ）等のエキシマ（励起二量体）を利用したエキシマレーザ、短波長を発振できるＹＡＧレーザなどがある。 Specific examples of such a pulse laser include excimers (excitation dimers) such as F 2 (wavelength 157 nm), ArF (wavelength 193 nm), KrF (wavelength 248 nm), XeCl (wavelength 308 nm), and XeF (wavelength 351 nm). ) Excimer laser, and YAG laser that can oscillate a short wavelength.
（２）照射工程
照射工程は、所望する窒化層の形態に応じて、高エネルギービームを金属基材の表面部へ照射しつつ、その照射域を移動させる工程である。
(2) Irradiation process An irradiation process is a process of moving the irradiation area, irradiating the surface part of a metal base material with a high energy beam according to the form of the desired nitrided layer.
高エネルギービームとしてパルスレーザを用いる場合、隣接して発振する各パルス光の照射域を部分的に重畳（オーバーラップ）させると、連続した窒化層が安定的に形成され易くなる。パルス波の照射域を重畳させる割合（パルスラップ率）は、パルスレーザの発振周波数、被処理部に対する相対移動速度（適宜「走査速度」という。）、被処理部の最表面における照射域の大きさ（またはパルスレーザの焦点位置）等により調整される。窒化層の形成や窒化組織は、前述したパルスレーザの特性にも依るため、パルスラップ率を画一的に特定し難いが、例えば１０〜９９．９％、２０〜９５％さらには５０〜９０％であると好ましい。パルスラップ率が過小では窒化層の形成が困難となり除去加工となり易い。パルスラップ率が過大では窒化処理の効率化や窒化組織の均質化を図り難い。 When a pulsed laser is used as the high energy beam, a continuous nitride layer is easily formed stably if the irradiation regions of the adjacent pulsed light beams are partially overlapped (overlapped). The ratio of overlapping the pulse wave irradiation area (pulse wrap ratio) is the oscillation frequency of the pulse laser, the relative movement speed with respect to the processing target (referred to as “scanning speed” as appropriate), and the size of the irradiation area on the top surface of the processing target. (Or the focal position of the pulse laser) or the like. The formation of the nitrided layer and the nitrided structure depend on the characteristics of the pulse laser described above, and therefore it is difficult to specify the pulse wrap rate uniformly. For example, it is 10 to 99.9%, 20 to 95%, or 50 to 90. % Is preferable. If the pulse wrap ratio is too small, it is difficult to form a nitride layer, which tends to be a removal process. If the pulse wrap ratio is excessive, it is difficult to improve the efficiency of nitriding treatment and homogenize the nitrided structure.
このパルスラップ率は、（ｒ／ｄ）×１００（％）（ｄ：ビーム径、ｒ：隣接するパルス波の重なり径）により算出される。ここでビーム径（ｄ）は、レーザ軸に対する直交面上で測定される、ビーム強度がピーク強度値の１／ｅ２レベルとなるときの幅（直径）である。また隣接するパルス波の重なり径（ｒ）は、ｄ−Ｒ（Ｒ：隣接するビーム間の中心間距離）である。 This pulse wrap rate is calculated by (r / d) × 100 (%) (d: beam diameter, r: overlap diameter of adjacent pulse waves). Here, the beam diameter (d) is a width (diameter) when the beam intensity is 1 / e 2 level of the peak intensity value measured on a plane orthogonal to the laser axis. The overlapping diameter (r) of adjacent pulse waves is dR (R: distance between the centers of adjacent beams).
パルスラップ率に基づいて発振周波数、走査速度、焦点位置等は調整されるが、一例をあげると次の通りである。発振周波数は、例えば、１〜１００ｋＨｚさらには１０〜５０ｋＨｚであると好ましい。発振周波数が過小では走査速度も低くせざるを得ず、窒化処理の効率化を図れない。発振周波数が過大になると、一般的にレーザフルエンスが低下し、均質的な窒化層の形成が困難となる。 The oscillation frequency, scanning speed, focus position, and the like are adjusted based on the pulse wrap ratio. An example is as follows. The oscillation frequency is preferably 1 to 100 kHz, more preferably 10 to 50 kHz, for example. If the oscillation frequency is too low, the scanning speed must be lowered, and the efficiency of the nitriding process cannot be achieved. If the oscillation frequency is excessive, the laser fluence generally decreases, and it becomes difficult to form a uniform nitride layer.
走査速度は、例えば、０．１〜１００ｍｍ／ｓさらには１〜１０ｍｍ／ｓであると好ましい。走査速度が過小では窒化処理の効率化を図れず、走査速度が過大になると、相関する発振周波数が過大な場合と同様に、均質的な窒化層の形成が困難となる。 The scanning speed is preferably 0.1 to 100 mm / s, more preferably 1 to 10 mm / s, for example. If the scanning speed is too low, the efficiency of the nitriding process cannot be improved, and if the scanning speed is too high, it becomes difficult to form a uniform nitrided layer, as in the case where the correlated oscillation frequency is too high.
パルスレーザの焦点位置により、各パルス光の照射範囲が変化する。焦点位置は、金属基材の被処理部の最表面にあっても、その最表面からずれたところにあってもよい。もっとも、焦点位置がパルスレーザの照射部（被処理部の最表面部）から外れるほど、照射部におけるフルエンスは低下し、その照射部近傍における窒化処理の安定性や窒化層深さ等に影響する。この傾向は、レーザを集光させて照射部に微細なスポット径を形成している場合ほど顕著である。 The irradiation range of each pulse light varies depending on the focal position of the pulse laser. The focal position may be on the outermost surface of the portion to be processed of the metal substrate or may be shifted from the outermost surface. However, the fluence at the irradiated portion decreases as the focal position deviates from the pulse laser irradiated portion (the outermost surface portion of the processing target portion), affecting the stability of the nitriding treatment, the nitrided layer depth, etc. in the vicinity of the irradiated portion. . This tendency is more conspicuous as the laser is condensed to form a fine spot diameter at the irradiated portion.
（３）雰囲気
照射工程を行う雰囲気は、既述したように、高エネルギービームを照射した際に、アブレーションにより活性窒素が発生し得る窒素含有雰囲気であればよい。このような雰囲気は、高エネルギービームの種類に応じて適宜選択される。
(3) Atmosphere The atmosphere in which the irradiation step is performed may be a nitrogen-containing atmosphere in which active nitrogen can be generated by ablation when irradiated with a high energy beam as described above. Such an atmosphere is appropriately selected according to the type of the high energy beam.
照射工程は、チャンバー等の密閉雰囲気内で行っても良いが、開放雰囲気内で行ってもよい。高エネルギービームとしてレーザを用いれば、開放雰囲気である常温常圧の大気雰囲気中でも可能である。もっとも、不純物の介在等を回避するために、被処理部へ特定ガスを流入させつつ行うと好ましい。例えば、被処理部の上方または側方から窒素ガス等を吹き付けるとよい。ガスの吹付方向を調整することにより、アブレーションに伴い生じるデブリの抑制等も図られ得る。例えば、その吹付方向を高エネルギービームの光軸と同軸とすることにより、窒素含有雰囲気の制御性が増し、窒化層の均質性が向上し得る。 The irradiation step may be performed in a sealed atmosphere such as a chamber, but may be performed in an open atmosphere. If a laser is used as the high energy beam, it is possible even in an air atmosphere at room temperature and pressure, which is an open atmosphere. However, in order to avoid the inclusion of impurities, etc., it is preferable to carry out the process while allowing the specific gas to flow into the portion to be processed. For example, nitrogen gas or the like may be sprayed from above or from the side of the processing target. By adjusting the gas blowing direction, it is possible to suppress the debris caused by ablation. For example, by making the blowing direction coaxial with the optical axis of the high energy beam, the controllability of the nitrogen-containing atmosphere can be increased and the homogeneity of the nitride layer can be improved.
《用途》
本発明の窒化金属部材は、その用途を問わない。本発明に係る窒化層を有する表面部は、高強度、高靱性であり、また表面粗さも小さく、種々の優れた特性（耐摩耗性、耐食性、電気的特性等）を安定的に発揮し得る。そこで本発明の窒化金属部材は、例えば、自動車部品等の耐摩耗性部材、ターボチャージャー・タービン等の耐食部材、半導体絶縁・放熱基板等の電気機器用部材などに好適である。
<Application>
The use of the metal nitride member of the present invention is not limited. The surface portion having the nitride layer according to the present invention has high strength and high toughness, and also has a small surface roughness, and can stably exhibit various excellent properties (abrasion resistance, corrosion resistance, electrical properties, etc.). . Therefore, the metal nitride member of the present invention is suitable for, for example, wear-resistant members such as automobile parts, corrosion-resistant members such as turbochargers and turbines, and members for electrical equipment such as semiconductor insulation and heat dissipation substrates.
《実施例１：チタン系基材》
〈試料の製作〉
（１）金属基材
市販されている代表的なチタン材であるＴｉ−６質量％Ａｌ−４質量％Ｖ（α−β型チタン合金）からなるチタン合金基材を用意した。基材サイズは基本的に１５．７×６．５×１０．０ｍｍとしたが、ＣＯ２レーザを用いる場合は熱容量を確保して熱的影響を小さくするために基材サイズを１００×１００×５ｍｍとした。
Example 1: Titanium-based substrate
<Production of sample>
(1) Metal base material A titanium alloy base material made of Ti-6 mass% Al-4 mass% V (α-β type titanium alloy), which is a typical commercially available titanium material, was prepared. The base material size is basically 15.7 × 6.5 × 10.0 mm. However, when a CO 2 laser is used, the base material size is 100 × 100 × in order to secure the heat capacity and reduce the thermal influence. It was 5 mm.
（２）高エネルギービーム
高エネルギービームとして、近紫外線領域（１９０〜４００ｎｍ特に３２０〜４００ｎｍ）の波長をもちパルス幅がナノ秒レベルのパルスレーザ（このレーザを単に「近紫外ナノ」レーザという。）と、近赤外線領域（８００〜２５００ｎｍ）の波長をもちパルス幅がナノ秒レベルのパルスレーザ（このレーザを単に「近赤外ナノ」レーザという。）と、赤外線領域の波長をもつレーザを連続的に出力するＣＯ２レーザ（Continuous Wave Laser）を準備した。具体的なレーザの仕様は表１に示した。なお、近赤外ナノレーザは固体ＹＡＧレーザの基本波であり、近紫外ナノレーザはその３倍波である。
(2) High energy beam As a high energy beam, a pulse laser having a wavelength in the near ultraviolet region (190 to 400 nm, particularly 320 to 400 nm) and a pulse width of nanosecond level (this laser is simply referred to as “near ultraviolet nano” laser). A pulse laser with a wavelength in the near infrared region (800-2500 nm) and a pulse width of nanosecond level (this laser is simply called “near infrared nano” laser) and a laser with a wavelength in the infrared region are continuously used. A CO 2 laser (Continuous Wave Laser) that outputs to the above was prepared. Specific laser specifications are shown in Table 1. Note that the near-infrared nanolaser is a fundamental wave of a solid YAG laser, and the near-ultraviolet nanolaser is a triple wave thereof.
（３）照射工程
チタン合金基材の被処理部へ窒素ガスを吹き付けつつ各レーザ光を照射した。この際、レーザの発振周波数、レーザの被処理部に対する相対移動速度（走査速度）、レーザの焦点位置およびレーザの出力および出力密度（レーザフルエンス）は表１に併せて示した。なお、焦点位置は、被処理部の最表面としたので、焦点はずし距離は０μｍとなる。また窒素ガスの吹き付けは、近紫外ナノレーザおよび近赤外ナノレーザの場合は被処理部に平行な側方から、ＣＯ２レーザの場合は光軸に沿った上方向から行った。
(3) Irradiation process Each laser beam was irradiated while blowing nitrogen gas to the to-be-processed part of a titanium alloy base material. At this time, the oscillation frequency of the laser, the relative movement speed (scanning speed) of the laser with respect to the processing target, the focal position of the laser, and the output and output density of the laser (laser fluence) are also shown in Table 1. Since the focal position is the outermost surface of the processing target, the defocusing distance is 0 μm. The blowing of nitrogen gas, the parallel side to the portion to be processed in the case of near-ultraviolet Nanoreza and Kin'akagai Nanoreza, in the case of CO 2 laser was carried out from above along the optical axis.
近紫外ナノレーザと近赤外ナノレーザの照射は、パルスラップ率を８５％とした。なお、パルスラップ率は前述した方法により算出した。また被処理部の表面上における各レーザ光の照射域の軌跡は２０μｍ間隔の平行な直線状とした。こうして照射工程を施した各試料（表２に示す試料Ｎｏ．１１および１２）を得た。なお、ＣＯ２レーザの場合は改質領域が４５０μｍ（ビーム径：２００μｍ）で、その照射域の軌跡は４００μｍ間隔の平行な直線状とした（試料Ｎｏ．１３）。 Irradiation of the near-ultraviolet nanolaser and near-infrared nanolaser had a pulse wrap rate of 85%. The pulse wrap rate was calculated by the method described above. In addition, the locus of the irradiation area of each laser beam on the surface of the processed portion was a parallel straight line with an interval of 20 μm. Thus, each sample (Sample Nos. 11 and 12 shown in Table 2) subjected to the irradiation step was obtained. In the case of a CO 2 laser, the modified region was 450 μm (beam diameter: 200 μm), and the locus of the irradiated region was a parallel straight line with an interval of 400 μm (Sample No. 13).
〈試料の評価〉
各試料における窒化の有無や特性を表２にまとめて示した。以降、それらについて詳述する。
<Evaluation of sample>
Table 2 summarizes the presence and characteristics of nitriding in each sample. Hereinafter, they will be described in detail.
（１）窒化改質の有無
近紫外ナノレーザを照射した試料Ｎｏ．１１とＣＯ２レーザを照射した試料Ｎｏ．１３との被処理部（表面部）には、窒化層が観察された。一方、近赤外ナノレーザを照射した試料Ｎｏ．１２の表面部には窒化層が観察されなかった。
(1) Presence or absence of nitriding modification Sample No. irradiated with near-ultraviolet nanolaser 11 and a sample No. irradiated with a CO 2 laser. A nitrided layer was observed in the portion (surface portion) to be treated with No. 13. On the other hand, the sample No. irradiated with the near infrared nanolaser. No nitride layer was observed on the surface portion of 12.
一例として、試料Ｎｏ．１１の表面部の断面を、走査型電子顕微鏡（ＳＥＭ）で観察した様子を図１に示した。図１から明らかなように、試料Ｎｏ．１１の場合、その表面部の相当深くまで窒化がされており、その窒化組織も均質で微細なことがわかる。 As an example, sample no. FIG. 1 shows a state in which a cross section of the surface portion of 11 is observed with a scanning electron microscope (SEM). As is clear from FIG. In the case of No. 11, nitriding is carried out to a considerable depth on the surface portion, and it can be seen that the nitrided structure is also homogeneous and fine.
試料Ｎｏ．１１の場合、表２に示すように、窒化層深さは１００μｍと深く、レーザ照射１行程あたりに形成される窒化層の最小幅は５μｍ程度であった。一方、試料Ｎｏ．１３の場合、窒化層深さは１３０μｍと深いが、レーザ照射１行程あたりに形成される窒化層の最小幅は４５０μｍ程度とかなり大きかった。ちなみに、近紫外ナノレーザのスポット径は０．７μｍであり、本実施例で用いたマルチモードＣＯ２レーザのスポット径は２００μｍ（カタログ値）とした。 Sample No. 11, the depth of the nitrided layer was as deep as 100 μm as shown in Table 2, and the minimum width of the nitrided layer formed per laser irradiation process was about 5 μm. On the other hand, sample No. In the case of No. 13, the depth of the nitrided layer was as deep as 130 μm, but the minimum width of the nitrided layer formed per laser irradiation process was about 450 μm. Incidentally, the spot diameter of the near-ultraviolet nanolaser was 0.7 μm, and the spot diameter of the multimode CO 2 laser used in this example was 200 μm (catalog value).
（２）硬さ
窒化層が形成された各試料の表面部のビッカース硬さを、最表面から１５μｍ、３０μｍおよび４５μｍの深さ位置で測定した。これらの測定結果に基づく深さ方向の硬さ分布を図２に示した。また、窒化層中の各位置における硬さを相加平均した平均硬さを表２に併せて示した。図２から明らかなように、試料Ｎｏ．１１では、１０００Ｈｖを超える硬さが内部深くまで均一的に得られていることがわかる。
(2) Hardness The Vickers hardness of the surface portion of each sample on which the nitride layer was formed was measured at depth positions of 15 μm, 30 μm, and 45 μm from the outermost surface. The hardness distribution in the depth direction based on these measurement results is shown in FIG. Table 2 also shows the average hardness obtained by arithmetically averaging the hardness at each position in the nitride layer. As is clear from FIG. 11 shows that hardness exceeding 1000 Hv is uniformly obtained deep inside.
一方、試料Ｎｏ．１３の場合、最表面側の硬さや平均硬さは高いものの、内部深くの硬さは急激に低下しており、硬さの変動が大きい。ちなみに、チタン合金基材の母材（生地）硬さは３５０Ｈｖである。 On the other hand, sample No. In the case of 13, the hardness on the outermost surface side and the average hardness are high, but the hardness deep inside is abruptly decreased, and the variation in hardness is large. Incidentally, the base material (fabric) hardness of the titanium alloy base material is 350 Hv.
（３）窒素濃度
試料Ｎｏ．１１および試料Ｎｏ．１３の表面部を電子線マイクロアナライザー（ＥＰＭＡ）により解析した結果（元素マッピング）をそれぞれ図３Ａおよび図３Ｂに示した。また、ＥＰＭＡに基づく定量分析結果から得られた表面部における窒素濃度分布を図４に示した。このときの窒素濃度は、最表面からの深さが１５μｍ、３５μｍおよび５５μｍとなる位置で測定した。これら窒素濃度を相加平均した平均窒素濃度を表２に併せて示した。
(3) Nitrogen concentration Sample No. 11 and sample no. The results (element mapping) of 13 surface portions analyzed by an electron beam microanalyzer (EPMA) are shown in FIGS. 3A and 3B, respectively. Moreover, the nitrogen concentration distribution in the surface part obtained from the quantitative analysis result based on EPMA is shown in FIG. The nitrogen concentration at this time was measured at a position where the depth from the outermost surface was 15 μm, 35 μm and 55 μm. The average nitrogen concentration obtained by arithmetically averaging these nitrogen concentrations is also shown in Table 2.
試料Ｎｏ．１１の場合、窒素が最表面から５０μｍぐらいの深さまで均一的に分布していることがわかる。一方、試料Ｎｏ．１３の場合、平均窒素濃度は大きいが、窒素濃度の分布は位置によって大きく変動する不均一なものであった。 Sample No. 11 shows that nitrogen is uniformly distributed from the outermost surface to a depth of about 50 μm. On the other hand, sample No. In the case of 13, the average nitrogen concentration was large, but the distribution of nitrogen concentration was non-uniform, which fluctuated greatly depending on the position.
（４）窒化組織
試料Ｎｏ．１１および試料Ｎｏ．１３の表面部の断面を透過型電子顕微鏡（ＴＥＭ）により観察した結果をそれぞれ図５Ａおよび図５Ｂに示した。
(4) Nitrided structure Sample No. 11 and sample no. The results of observation of the cross section of 13 surface portions with a transmission electron microscope (TEM) are shown in FIGS. 5A and 5B, respectively.
試料Ｎｏ．１１の場合、結晶粒（図５Ａ中で黒太線で囲んだ部分）は微細であり、その平均結晶粒径は１５０ｎｍであった。前述したように、平均窒素濃度が少ないにもかかわらず、全体的に十分な硬さを有していたのは、試料Ｎｏ．１１の窒化組織が全体的に微細であるためと考えられる。なお、平均結晶粒径は、既述した通り、ＴＥＭ像の視野内に現れた各結晶粒の長軸と単軸を相加平均して求めた値である。 Sample No. In the case of 11, the crystal grain (portion surrounded by the thick black line in FIG. 5A) was fine, and the average crystal grain size was 150 nm. As described above, although the average nitrogen concentration was small, the sample No. 1 had sufficient hardness overall. This is probably because the nitride structure of 11 is fine as a whole. The average crystal grain size is a value obtained by arithmetically averaging the major axis and the uniaxial axis of each crystal grain appearing in the field of view of the TEM image as described above.
一方、試料Ｎｏ．１３の場合、平均長さ５．７μｍで平均幅０．８μｍ程度の針状結晶（図５Ｂ中で黒太線で囲んだ部分）が多数晶出（または析出）していることがわかった。このような組織が観察されたのは、被処理部がＣＯ２レーザの照射により溶融した後に、再凝固したためと考えられる。 On the other hand, sample No. In the case of 13, it was found that a large number of needle-like crystals (portion surrounded by black thick lines in FIG. 5B) having an average length of 5.7 μm and an average width of about 0.8 μm were crystallized (or precipitated). The reason why such a structure was observed is thought to be that the part to be treated was melted by irradiation with a CO 2 laser and then re-solidified.
試料Ｎｏ．１１の表面部（具体的には最表面から１０μｍの部分）についてＸ線回折（ＸＲＤ）による解析を行った。この結果を図６に示した。その試料の同様の部分について、ＴＥＭによる極微電子線回折測定を３カ所で行った。その結果を図７に示す。 Sample No. 11 surface portions (specifically, 10 μm from the outermost surface) were analyzed by X-ray diffraction (XRD). The results are shown in FIG. The same portion of the sample was subjected to microelectron beam diffraction measurement by TEM at three locations. The result is shown in FIG.
これらの結果から、試料Ｎｏ．１１の表面部には、ＴｉＮ、ＴｉＮ０．２６ 、（ＡｌＴｉ）Ｎ２、ＴｉＶＮ２などの窒化物が分散していることが明らかとなった。すなわち、その表面部は、母材（チタン合金）中へ窒素が固溶した単なる窒素固溶体ではなく、そこに種々の窒化物が微細に分散した複合組織からなることが明らかとなった。一方、試料Ｎｏ．１３の窒化組織は、粗くて脆い組織からなり、最表面には後加工が必要なほどのうねりを生じていた（図３Ｂ参照）。 From these results, sample no. 11 was found to disperse nitrides such as TiN, TiN 0.26 , (AlTi) N 2 , and TiVN 2 . That is, it has been clarified that the surface portion is not a simple nitrogen solid solution in which nitrogen is dissolved in the base material (titanium alloy) but a composite structure in which various nitrides are finely dispersed therein. On the other hand, sample No. The nitrided structure of 13 was a rough and brittle structure, and the outermost surface was undulated so as to require post-processing (see FIG. 3B).
《実施例２：鉄鋼系基材》
〈試料の製作〉
市販されている代表的な鉄鋼材（ＪＩＳ Ｓ４５Ｃ）からなる鉄鋼基材を用意した。この鉄鋼基材に、前述した各レーザによる照射を行った。こうして鉄鋼基材へ各レーザを照射した試料（表２に示す試料Ｎｏ．２１、２２および２３）を得た。各試料における窒化の有無や各特性は表２に併せて示した。なお、本実施例の基材サイズは基本的に１５．７×６．５×１０．０ｍｍとしたが、ＣＯ２レーザを用いる場合は熱容量を確保して熱的影響を小さくするために基材サイズをφ３０×５ｍｍとした。
<< Example 2: Steel base material >>
<Production of sample>
A steel base material made of a representative steel material (JIS S45C) that was commercially available was prepared. This steel substrate was irradiated with each laser described above. In this way, samples (sample Nos. 21, 22, and 23 shown in Table 2) were obtained by irradiating the steel base with each laser. The presence or absence of nitriding and the characteristics of each sample are shown in Table 2. The base material size of this example is basically 15.7 × 6.5 × 10.0 mm. However, in the case of using a CO 2 laser, the base material is used in order to secure the heat capacity and reduce the thermal influence. The size was φ30 × 5 mm.
〈試料の評価〉
（１）窒化の有無
近紫外ナノレーザを照射した試料Ｎｏ．２１の表面部には、チタン合金基材の場合と同様に、微細な窒化組織が観察された。しかし、それ以外のレーザを照射した試料の表面部には、窒素雰囲気中にもかかわらず、窒化組織が観察されなかった。但し、ＣＯ２レーザを照射した試料Ｎｏ．２３の表面部には、図８に示すような焼き入れ組織（焼きなまし組織を含む）が観察された。
<Evaluation of sample>
(1) Presence or absence of nitriding Sample No. irradiated with near-ultraviolet nanolaser As in the case of the titanium alloy base material, a fine nitride structure was observed on the surface portion 21. However, a nitrided structure was not observed on the surface of the sample irradiated with other lasers, despite being in a nitrogen atmosphere. However, the sample No. irradiated with the CO 2 laser. A quenched structure (including an annealed structure) as shown in FIG.
（２）硬さ
実施例１の場合と同様に、試料Ｎｏ．２１および試料Ｎｏ．２３の表面部におけるビッカース硬さを測定し、それらの深さ方向の硬さ分布を図９に示した。図９から明らかなように、試料Ｎｏ．２１では、十分な硬さが内部深くまで均一的に分布していた。
(2) Hardness As in the case of Example 1, sample No. 21 and Sample No. The Vickers hardness in 23 surface parts was measured, and the hardness distribution of those depth directions was shown in FIG. As is clear from FIG. In No. 21, sufficient hardness was uniformly distributed deep inside.
一方、試料Ｎｏ．２３では、全体的に試料Ｎｏ．２１よりも硬さが小さく、硬さ分布も不均一であった。ちなみに、母材である鉄鋼基材自体のビッカース硬さは２００Ｈｖであった。 On the other hand, sample No. 23, sample No. The hardness was smaller than 21, and the hardness distribution was non-uniform. Incidentally, the Vickers hardness of the steel base material itself, which is a base material, was 200 Hv.
（３）窒素濃度
実施例１の場合と同様に、試料Ｎｏ．２１の表面部における窒素濃度分布を図４に示した。図４から明らかなように、試料Ｎｏ．２１の窒素濃度も、内部深くまで均一的であることがわかった。
(3) Nitrogen concentration As in the case of Example 1, sample no. The nitrogen concentration distribution in the surface portion of 21 is shown in FIG. As is clear from FIG. The nitrogen concentration of 21 was also found to be uniform deep inside.
（４）窒化組織
実施例１の場合と同様に、試料Ｎｏ．２１の表面部には、平均結晶粒径が２９１ｎｍの微細な窒化組織が形成されていた。
(4) Nitrided structure As in the case of Example 1, sample No. A fine nitride structure having an average crystal grain size of 291 nm was formed on the surface portion 21.
《実施例３：ステンレス系基材》
〈試料の製作〉
市販されている代表的なオーステナイト系ステンレス材（ＪＩＳ ＳＵＳ３０４）からなるステンレス基材を用意した。このステンレス基材へ、前述した各レーザを照射して各試料（表２に示す試料Ｎｏ．３１、３２および３３）を得た。各試料における窒化の有無や各特性は表２に併せて示した。なお、本実施例の基材サイズは基本的に１５．７×６．５×１０．０ｍｍとしたが、ＣＯ２レーザを用いる場合は熱容量を確保して熱的影響を小さくするために基材サイズを３０×３０×８ｍｍとした。
<< Example 3: Stainless steel base material >>
<Production of sample>
A stainless steel substrate made of a typical austenitic stainless steel (JIS SUS304) that is commercially available was prepared. This stainless steel substrate was irradiated with the lasers described above to obtain samples (Sample Nos. 31, 32 and 33 shown in Table 2). The presence or absence of nitriding and the characteristics of each sample are shown in Table 2. The base material size of this example is basically 15.7 × 6.5 × 10.0 mm. However, in the case of using a CO 2 laser, the base material is used in order to secure the heat capacity and reduce the thermal influence. The size was 30 × 30 × 8 mm.
なお、参考までに、同じステンレス基材へ放電プラズマ窒化した試料（Ｎｏ．３４）も製作した。この放電プラズマ窒化はＮ２＋５０％Ｈ２の雰囲気中で５００℃×１時間行った。 For reference, a sample (No. 34) obtained by discharge plasma nitriding on the same stainless steel substrate was also produced. This discharge plasma nitriding was performed in an atmosphere of N 2 + 50% H 2 at 500 ° C. for 1 hour.
〈試料の評価〉
（１）窒化の有無
近紫外ナノレーザを照射した試料Ｎｏ．３１の表面部には、チタン合金基材等の場合と同様に、微細な窒化組織が観察された。また、放電プラズマ窒化した試料Ｎｏ．３４にも当然に窒化組織が観察された。しかし、それ以外のレーザを照射した試料の表面部は、窒素雰囲気中にもかかわらず窒化されなかった。なお、本実施例で用いたステンレス基材は炭素を実質的に含まないため、ＣＯ２レーザを照射した試料Ｎｏ．３３には、試料Ｎｏ．２３のような焼き入れ組織も生じなかった。
<Evaluation of sample>
(1) Presence or absence of nitriding Sample No. irradiated with near-ultraviolet nanolaser A fine nitrided structure was observed on the surface portion 31 as in the case of a titanium alloy substrate. In addition, the sample No. No. of discharge plasma nitrided Naturally, a nitrided structure was also observed in 34. However, the surface portion of the sample irradiated with the other laser was not nitrided despite being in a nitrogen atmosphere. Since the stainless steel substrate used in this embodiment is substantially free of carbon, the sample was irradiated with CO 2 laser No. 33 includes sample no. A hardened structure such as 23 was not produced.
（２）硬さ
実施例１の場合と同様に、試料Ｎｏ．３１および試料Ｎｏ．３３の表面部におけるビッカース硬さを測定し、それらの深さ方向の硬さ分布を図１０に示した。図１０から明らかなように、試料Ｎｏ．３１は、内部深くまで、最表面側と同程度の十分な硬さを有していた。一方、試料Ｎｏ．３３は、ステンレス基材の母材（生地）硬さ２００Ｈｖにほぼ等しい硬さしかなく、実質的に硬化していなかった。
(2) Hardness As in the case of Example 1, sample No. 31 and Sample No. Vickers hardness at the surface portion of 33 was measured, and the hardness distribution in the depth direction was shown in FIG. As is clear from FIG. No. 31 had sufficient hardness as deep as the outermost surface side deep inside. On the other hand, sample No. No. 33 had a hardness substantially equal to the base material (fabric) hardness of 200 Hv of the stainless steel substrate, and was not substantially cured.
（３）窒素濃度
実施例１の場合と同様に、試料Ｎｏ．３１の表面部における窒素濃度分布を図４に併せて示した。図４から明らかなように、試料Ｎｏ．３１も、窒素濃度が内部深くまで均一的であった。
(3) Nitrogen concentration As in the case of Example 1, sample no. The nitrogen concentration distribution in the surface portion of 31 is also shown in FIG. As is clear from FIG. No. 31 also had a uniform nitrogen concentration deep inside.
一方、試料Ｎｏ．３４の表面部における窒素濃度は、最表面近傍で１７原子％と非常に高いものの、そこから急激に低下して、高々７μｍ程度の深さ位置でほぼゼロになった。このように従来の放電プラズマ窒化で得られる窒化層は、窒素濃度に関して急激な傾斜層となっていた。 On the other hand, sample No. The nitrogen concentration at the surface portion of 34 was very high at 17 atomic% in the vicinity of the outermost surface, but it suddenly decreased and became almost zero at a depth of about 7 μm at most. Thus, the nitrided layer obtained by conventional discharge plasma nitriding has become a steep graded layer with respect to the nitrogen concentration.
（４）窒化組織
実施例１の場合と同様に、試料Ｎｏ．３１の表面部には微細な窒化組織が観察された。
(4) Nitrided structure As in the case of Example 1, sample No. A fine nitride structure was observed on the surface portion 31.
《実施例４》
近紫外ナノレーザを照射して得られた窒化層を有する窒化金属部材の耐摩耗性を次のようにして評価した。
Example 4
The wear resistance of a metal nitride member having a nitride layer obtained by irradiation with a near-ultraviolet nanolaser was evaluated as follows.
〈試験片の製作〉
実施例１で用意したチタン材からなるブロック状の試験片を３つ用意した。そのうち一つは未処理とした（試験片Ｎｏ．１１０）。残り二つには、実施例１の場合と同様に、近紫外ナノレーザの照射により窒化層を形成した。但し、そのうち一つには全面的に窒化層を形成し（試験片Ｎｏ．１１１）、もう一つには２０μｍピッチのストライプ状の窒化層を形成した（試験片Ｎｏ．１１２）。つまり、試験片Ｎｏ．１１２には、非窒化層と窒化層が共存したテクスチャ組織を形成した。
<Production of test piece>
Three block-shaped test pieces made of the titanium material prepared in Example 1 were prepared. One of them was left untreated (test piece No. 110). In the remaining two, as in Example 1, a nitride layer was formed by irradiation with a near-ultraviolet nanolaser. However, one of them was formed with a nitrided layer over the entire surface (test piece No. 111), and the other was formed with a striped nitride layer with a pitch of 20 μm (test piece No. 112). That is, test piece No. In 112, a texture structure in which a non-nitrided layer and a nitrided layer coexist was formed.
〈試験方法〉
各試験片をブロックオンリング試験に供した。ブロックオンリング試験は、各試験片（ブロック）の摺動面を、回転するリングの円筒状外周面へ押し付けて、試験片の摩耗具合を評価する試験方法である（ＡＳＴＭ規格Ｇ７７−０５参照）。具体的には、非Ｍｏ系エンジンオイルの潤滑下で、回転数：１６４ｒ.ｐ.ｍ. 、押し付け荷重：４．４Ｎ、試験時間：３０分、試験温度：８０℃として行った。
<Test method>
Each specimen was subjected to a block on ring test. The block-on-ring test is a test method in which the sliding surface of each test piece (block) is pressed against the cylindrical outer peripheral surface of the rotating ring to evaluate the wear condition of the test piece (see ASTM standard G77-05). . Specifically, under the lubrication of non-Mo engine oil, the rotation speed was 164 rpm, the pressing load was 4.4 N, the test time was 30 minutes, and the test temperature was 80 ° C.
〈評価〉
各試験片の試験結果を表３に示した。試験片Ｎｏ．１１０は、摺動面が未処理であるため、摩耗幅および摩耗深さが共に大きくなっている。一方、試験片Ｎｏ．１１１およびＮｏ．１１２は、摩耗幅および摩耗深さが共に非常に小さく、高い耐摩耗性を発現することが確認された。しかも、試験片Ｎｏ．１１１と試験片Ｎｏ．１１２の結果から、窒化層の形態が異なっていても、つまり金属基材の表面部がテクスチャ組織となっている場合でも、優れた耐摩耗性が発現されることが確認された。
<Evaluation>
The test results of each test piece are shown in Table 3. Specimen No. In 110, since the sliding surface is untreated, both the wear width and the wear depth are large. On the other hand, test piece No. 111 and no. It was confirmed that No. 112 had a very small wear width and wear depth and exhibited high wear resistance. Moreover, the test piece No. 111 and test piece no. From the result of 112, it was confirmed that excellent wear resistance was exhibited even when the form of the nitrided layer was different, that is, even when the surface portion of the metal substrate had a textured structure.
これにより、本発明の窒化金属部材を耐摩耗性部材として用いる場合、摺動面の全面に窒化層を形成する必要がないことがわかった。すなわち、耐摩耗性部材の仕様や生産性等を考慮して、窒化層または窒化組織の形態を適切に選択し得ることが明らかとなった。 Thereby, when using the metal nitride member of this invention as an abrasion-resistant member, it turned out that it is not necessary to form a nitride layer in the whole sliding surface. That is, it has been clarified that the form of the nitrided layer or nitrided structure can be appropriately selected in consideration of the specifications and productivity of the wear resistant member.
〈その他〉
上述した試験片では、２０μｍピッチの窒化層を形成したが、４０μｍピッチの窒化層を形成した場合でも８０μｍピッチの窒化層を形成した場合でも、上述した場合と同等な耐摩耗性が得られることが確認されている。
<Others>
In the test piece described above, a nitride layer with a pitch of 20 μm was formed. However, even when a nitride layer with a pitch of 40 μm or a nitride layer with a pitch of 80 μm is formed, wear resistance equivalent to that described above can be obtained. Has been confirmed.
また、上述した実施例では全て、被処理部に対して照射工程を一回しか行わなかったが、照射工程を複数繰り返して行ってもよい。照射工程の回数を増やすことにより、被処理部における窒素濃度を一層高めることが可能となる。但し、本発明の製造方法によれば、一回の照射工程でも、均質的であり、かつ十分な深さをもつ窒化層を効率的に形成できる。 In all of the above-described embodiments, the irradiation process is performed only once on the target portion. However, the irradiation process may be repeated a plurality of times. By increasing the number of irradiation steps, the nitrogen concentration in the portion to be processed can be further increased. However, according to the manufacturing method of the present invention, a nitride layer having a uniform and sufficient depth can be efficiently formed even in a single irradiation step.
Claims (9)
前記窒化層は、前記金属基材の最表面側から測定して窒化層深さの９０％に相当する位置における窒素濃度（原子％）である深層濃度が、該窒化層深さの１０％に相当する位置における窒素濃度（原子％）である浅層濃度よりも、大きいかまたは同等であることを特徴とする窒化金属部材。 A metal nitride member comprising a metal substrate capable of nitriding and having a nitride layer on the surface portion of the metal substrate,
The nitride layer has a nitrogen concentration (atomic%) at a position corresponding to 90% of the nitrided layer depth measured from the outermost surface side of the metal substrate, and the nitrided layer depth is 10% of the nitrided layer depth. A metal nitride member characterized by being greater than or equal to a shallow layer concentration which is a nitrogen concentration (atomic%) at a corresponding position.
請求項１に記載の窒化金属部材が得られることを特徴とする窒化金属部材の製造方法。 By irradiating the target portion of the nitridable metal substrate in a nitrogen-containing atmosphere while moving the high energy beam relative to the target portion, ablation occurs in the target portion and the target portion is irradiated. Provided with an irradiation process to generate plasma nitrogen in the vicinity of the processing unit,
A method for producing a metal nitride member, wherein the metal nitride member according to claim 1 is obtained.
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