JP4302930B2 - High corrosion resistance, high strength, high toughness Nitrided Mo alloy processed material and its manufacturing method - Google Patents
High corrosion resistance, high strength, high toughness Nitrided Mo alloy processed material and its manufacturing method Download PDFInfo
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、内部窒化処理と外部窒化処理を組み合わせて強度・靭性の他に耐食性を改善した窒化処理Ｍｏ合金加工材とその製造方法に関する。
【０００２】
【従来の技術】
Ｍｏは融点が約２６００℃と高く、他の高融点金属に比べて比較的に機械的強度に優れており、熱膨張率が小さく、電気伝導性・熱伝導性が良好、溶融アルカリ金属や塩酸に対する耐食性が良好、などの特徴を有し、電極、管球用部品、半導体部品、耐熱構造部品、原子炉用材料などの用途がある。
【０００３】
しかし、加工組織を有する加工材ではクラック伝播が困難で高靭性を示すのに対して、一旦、加熱（約１０５０℃以上）後の再結晶材では、クラック伝播が容易になり脆化するので高温強度が十分ではなく、高温強度を改善したＭｏ合金としてＴＺＭ合金（Mo-0.5Ti-0.08Zr-0.03C)やＴＺＣ(Mo-1.5Nb-0.5Ti-0.03Zr-0.03C）合金が開発されている。
【０００４】
本発明者らは、先に、多段階の内部窒化処理を行って超微細窒化物を分散含有させたＭｏなどの高融点金属合金加工材において、加工材の少なくとも表面側は加工組織を維持したままとすることにより高靭性・高強度が得られることを見出だした（特開２００１−７３０６０号公報）。
【０００５】
Ｍｏは上記のように優れた特性を有するが、熱濃硫酸や硝酸などの酸化性の酸に対する耐食性がない。耐食性改善に関して、本発明者らは、ＭｏおよびＭｏ系合金を窒化処理して厚さ０．５〜１０μｍのＭｏ２Ｎ層を設けた高耐食性Ｍｏ系複合材料を開発した（特開平１１−２８６７７０号公報）。
【０００６】
【発明が解決しようとする課題】
超苛酷腐食条件下（例えば、沸騰濃硫酸溶液）での装置材料としては、現在までＴａ金属しか有用でなかった。しかし、Ｔａ金属は低強度であり、特に高温度での強度は低く、高強度が要求される装置・構造材料としては適していない。また、Ｔａ金属に代わる材料として本発明者らが開発した上記の高耐食性Ｍｏ系複合材料は製造過程において母材が再結晶する結果、材料全体が脆化する欠点があった。
【０００７】
そこで、本発明は、沸騰濃硫酸溶液（例：75％Ｈ２ＳＯ４水溶液(180℃））など超苛酷腐食条件下でも十分に高耐食性および高強度を示し、その上、高温においても高強度で、かつ低温でも高靭性を有するこれまでにない物性を合わせ持つ革新的材料とその効率的な製造方法の提供を目的とする。
【０００８】
【課題を解決するための手段】
本発明者らは、Ｍｏ加工材に内部窒化処理と外部窒化処理を組み合わせることにより、効率的に安価に高強度・高靭性とともに酸化性の酸に対しても優れた耐食性を有するＭｏ合金加工材が得られることを見出した。
【０００９】
すなわち、本発明は、Ｍｏ合金加工材のＭｏ母相中に固溶した窒化物形成金属元素が内部窒化されて生成した窒化物粒子が該加工材内部の表面側の加工組織または回復組織に分散した層が形成され、さらに、該加工材表面の加工組織または回復組織が外部窒化されて生成したδ−ＭｏＮ、γ−Ｍｏ ２ Ｎまたはβ−Ｍｏ ２ Ｎの少なくとも１種からなる厚さ３μｍ以下のＭｏ窒化物層が表面に形成されており、該加工材内部が再結晶組織層である、三層構造からなり、前記内部窒化した段階よりも大きな降伏強度を有することを特徴とする高耐食性・高強度・高靭性窒化処理Ｍｏ合金加工材である。
【００１０】
また、本発明は、Ｍｏ合金加工材のＭｏ母相中に固溶した窒化物形成金属元素が内部窒化されて生成した窒化物粒子が該加工材内部の表面側の加工組織または回復組織に分散した層が形成され、さらに、該加工材表面の加工組織または回復組織が外部窒化されて生成したδ−ＭｏＮ、γ−Ｍｏ ２ Ｎまたはβ−Ｍｏ ２ Ｎの少なくとも１種からなる厚さ３μｍ以下のＭｏ窒化物層が表面に形成されている、内部まで加工組織が保持され、再結晶層のない二層構造からなり、前記内部窒化した段階よりも大きな降伏強度を有することを特徴とする高耐食性・高強度・高靭性窒化処理Ｍｏ合金加工材である。
【００１１】
さらに、本発明は、Ｍｏを母相とし、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａの少なくとも１種を固溶した合金加工材に段階的に処理温度を上げて少なくとも３段階の内部窒化処理を行い、次いで外部窒化処理を９００℃以下で行い厚さ３μｍ以下のＭｏ窒化物層を表面に形成することを特徴とする上記の窒化処理Ｍｏ合金加工材の製造方法である。
【００１２】
また、本発明は、内部窒化処理をＮ２ガスで行い、次いで外部窒化処理をＮＨ３ガスで行うことを特徴とする上記の窒化処理Ｍｏ合金加工材の製造方法である。
【００１３】
【発明の実施の形態】
図１は、本発明の窒化処理Ｍｏ合金加工材の断面構造の一例を示す模式図である。図１に示す本発明の窒化処理Ｍｏ合金加工材は、加工材１の内部の表面側の加工組織または回復組織層３に分散したナノサイズ窒化物粒子２の層、加工材の表面の加工組織または回復組織層３が外部窒化されて生成したＭｏ２Ｎ表面層４と加工材の内部のＭｏ再結晶組織層５からなる三層構造となる。加工材が比較的薄い場合には内部まで完全に加工組織が保持されたままとすることも可能であり、その場合はＭｏ再結晶層５のない二層構造となる。
【００１４】
加工材は、Ｍｏを母相とし、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａの少なくとも１種を固溶した希薄合金を圧延などの加工を行ったものである。なお、希薄合金とは固溶体合金の溶質元素の濃度が約５重量％以下の微少量含有される合金をいう。
【００１５】
本発明の高耐食性・高強度・高靭性窒化処理Ｍｏ合金加工材は下記の内部窒化処理（１）〜（３）と外部窒化処理（４）により製造される。図２の（１）〜（３）は、段階的に処理温度を上げて行う内部窒化処理（１）〜（３）の各段階の加工材の組織を示す模式図である。
【００１６】
（１）第１段窒化処理：窒化雰囲気中において再結晶上限温度以下で、かつ再結晶下限温度−２００℃以上の温度で加熱して、窒化物形成用金属元素の超微細窒化物粒子を分散形成させる。第１段窒化処理では、希薄合金加工材の加工組織Ｘ１を維持したまま窒素を加工材に拡散することにより母相中に固溶されている窒化物形成金属元素を優先窒化して直径１〜２ｎｍ程度のサブナノ板状窒化物粒子を形成し、母相に分散させる。なお、優先窒化とは、母相の金属ではなく窒化物形成元素のみが優先的に窒化される現象をいう。この窒化処理により生成した析出粒子のピン止め効果により加工材表面部の再結晶温度が上昇する。
【００１７】
（２）第２段窒化処理：窒化雰囲気中において第１段窒化処理で得られた加工材の再結晶下限温度以上の温度で加熱して、超微細窒化物粒子を粒成長させ安定化させる。第２段窒化処理により析出粒子の成長・安定化により再結晶温度がさらに上昇する。窒化時に加工材内部は再結晶し加工組織Ｘ２が残るが、加工材が比較的薄い場合（３ｍｍ以下）には内部まで完全に加工組織の保持が可能である。
【００１８】
（３）第３段以降の窒化処理：窒化雰囲気中において前段処理で得られた加工材の再結晶下限温度以上の温度で加熱して、窒化物粒子を粒成長させ安定化させる。第３段以降の窒化処理は、加工組織Ｘ３を残したまま、窒化物粒子の更なる成長・安定化を目的とするものであり、太さ約１０ｎｍ、長さ約５０ｎｍの棒状窒化物粒子がＭｏ母相に均一に分散する。第３段以降の第４段、第５段などの窒化処理は適宜行うことができる。
【００１９】
（４）外部窒化処理：強い窒化処理によりＭｏの窒化物層を表面に形成する。窒化雰囲気は、アンモニアガス雰囲気、Ｎ２ガス雰囲気、フォーミングガス雰囲気（水素ガス：窒素ガス＝１：９〜５：５）、およびこれら三者のガスのそれぞれにプラズマ放電させた雰囲気などいずれでもよい。形成されるＭｏ窒化物はδ−ＭｏＮ、γ−Ｍｏ２Ｎまたはβ−Ｍｏ２Ｎの少なくとも１種からなる。表面のＭｏ窒化物層と加工材内部のＭｏ母相との間には加工組織または回復組織が残るようにする。
【００２０】
外部窒化処理の加熱処理温度と皮膜の厚さの関係をＭｏ−０．５ｗｔ％Ｔｉ合金の場合について下記の表１に示す。加熱温度が高いほど膜厚が大きくなる。耐食性の観点からは膜厚は厚い方がよいといえるが、厚くするにつれ内部窒化した段階よりも靭性（曲げ特性）が低下することが分かった。したがって、靭性と耐食性を兼ね備える条件としては、９００℃以下の外部窒化処理（厚さ約３μｍ以下）とする必要がある。
【００２１】
【表１】
本発明の窒化処理Ｍｏ合金加工材は、半導体・セラミックス・金属高温焼成用支持板、高温加熱炉用ヒーター、高温加熱炉用部材、腐食環境下の化学設備・装置用構造材（高温焼却炉等も含む）、超臨界・亜臨界溶液反応装置材料などの他、硫酸、硝酸などの酸化性の酸用の耐酸容器や管材、超苛酷腐食条件下（例えば、沸騰濃硫酸溶液）での装置材料、超高温ヒーター、金属射出成型金型、ディーゼルエンジン用噴射ノズルなどとして有用である。
【００２３】
【実施例】
比較例１
厚さ１ｍｍ、一辺１０ｍｍの平板状のＭｏ−１．０ｗｔ％Ｔｉ合金加工材をＮ２ガス（１気圧）気流中にて加熱温度を変えて４段内部窒化した。加熱温度は、９００℃→９５０℃→１２００℃→１５００℃とした。
【００２４】
この多段窒化処理により、加工材の表面域（表面から深さ約２００μｍまで）は加工・回復組織を保持し（内部は再結晶組織）、加えて微細なＴｉＮ粒子を分散析出させた。さらに、ＮＨ３ガス（１気圧）気流中にて１０００℃、４時間外部窒化処理して加工材の表面に厚み１４．０μｍのＭｏ窒化物（γ‐Ｍｏ２Ｎなど）層を形成した。
【００２５】
この加工材では、加工材の表面がＭｏ窒化物層、その内側が微細ＴｉＮ粒子が分散析出した加工・回復結晶粒組織のＭｏを母相とする固溶元素の窒化物層、さらにその内側は大きな等軸再結晶粒組織のＭｏ合金層の三層構造を呈する。しかしながら、表面のＭｏ窒化物層の膜厚が大きく内部窒化した段階よりも靭性が低下した。
【００２６】
次に、苛酷腐食環境下での耐食性を検討するため、７５％濃硫酸沸騰溶液（１８５℃）中で腐食試験を行った結果を図３に示す。図３中には、比較試料として純Ｍｏの結果も示す。純Ｍｏの腐食速度は８ｍｍ／年と高く、激しく腐食するのに対して、比較例１の加工材は０．０７６ｍｍ／年と殆ど腐食せず、ほぼ完全耐食性（腐食速度：＜０．０５ｍｍ／年）を示すことが見出された。
【００２７】
実施例１
Ｍｏ−０．５ｗｔ％Ｔｉ合金加工材をＮ２ガス（１気圧）気流中にて加熱温度を変えて３段内部窒化した。温度は、９００℃→１２００℃→１５００℃とした。３段内部窒化処理したＭｏ合金を、さらに、１気圧ＮＨ３気流中で９００℃、４ｈ加熱（外部窒化処理）して、加工材表面にＭｏ窒化物（δ−ＭｏＮ，γ−Ｍｏ２Ｎ）層を均一に形成した。この多段窒化処理により、微細ＴｉＮ粒子が分散析出し、加工・回復結晶粒組織の内部窒化層は３１０μｍであり、Ｍｏ窒化物の外部窒化層は２．８μｍであった。また、加工材表面のＸ線回折パターンより、δ−ＭｏＮとγ−Ｍｏ２Ｎの外部窒化物層の形成が認められた。
【００２８】
７５％濃硫酸沸騰溶液（１８５℃）中で腐食試験を行った結果を図３に示す。実施例２の加工材では、０．０４６ｍｍ／年と殆ど腐食せず、完全耐食性（腐食速度：＜０．０５ｍｍ／年）を示す。
【００２９】
さらに、実施例１の３段内部窒化処理（９００℃→１２００℃→１５００℃）した加工材とその後に外部窒化処理（９００℃−４ｈ）した加工材の室温における曲げ強度（降伏強度と最大強度）を表２に示す。また、図４に（ａ）断面組織写真と（ｂ）曲げ試験後の試片のマクロ写真を示す。
【００３０】
表２より、実施例１の９００℃、４ｈ外部窒化処理した加工材（Ｍｏ窒化物層厚さ：約２．８μｍ）の降伏強度と最大強度は、いずれも３段内部窒化処理材（高強度・高靭性化）よりも大きく、外部窒化処理により内部窒化した段階よりも大きい降伏応力値を示すことが見出された。
【００３１】
即ち、本発明の窒化処理Ｍｏ合金加工材は高耐食性とともに極めて高い強度を有することが明らかとなった。
【００３２】
【表２】
【発明の効果】
本発明は、窒化処理のみにより効率的に安価に高強度・高靭性とともに酸化性の酸に対しても優れた耐食性を有し、極限腐食環境に対応できる窒化処理Ｍｏ合金加工材を提供するもので、従来のＭｏまたはＭｏ合金の各種用途はもちろん、超苛酷腐食条件下（例えば、沸騰濃硫酸溶液）での装置材料、超高温ヒーター、金属射出成型金型、ディーゼルエンジン用噴射ノズルなどの各種用途へのＭｏ材料の実用化に貢献するものである。
【図面の簡単な説明】
【図１】本発明の窒化処理Ｍｏ合金加工材の断面構造を示す模式図である。
【図２】本発明の窒化処理Ｍｏ合金加工材を製造する工程における内部窒化処理（１）〜（３）の各段階の加工材の組織を示す模式図である。
【図３】比較例１および実施例１により得られた窒化処理Ｍｏ合金加工材と比較例（純Ｍｏ材料）の腐食試験結果を示すグラフである。
【図４】実施例１により得られた窒化処理Ｍｏ合金加工材の図面代用断面組織写真（ａ）および曲げ試験後の窒化処理Ｍｏ合金加工材試片の図面代用マクロ写真（ｂ）である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nitrided Mo alloy processed material having improved corrosion resistance in addition to strength and toughness by combining an internal nitriding treatment and an external nitriding treatment, and a method for producing the same.
[0002]
[Prior art]
Mo has a high melting point of about 2600 ° C. and relatively excellent mechanical strength compared to other refractory metals, has a low coefficient of thermal expansion, good electrical conductivity and thermal conductivity, molten alkali metal and hydrochloric acid It has a feature such as good corrosion resistance to, and has applications such as electrodes, tube components, semiconductor components, heat-resistant structural components, and reactor materials.
[0003]
However, in the processed material having a processed structure, crack propagation is difficult and exhibits high toughness, whereas in a recrystallized material after heating (about 1050 ° C. or higher), crack propagation becomes easy and embrittles, so TZM alloys (Mo-0.5Ti-0.08Zr-0.03C) and TZC (Mo-1.5Nb-0.5Ti-0.03Zr-0.03C) alloys have been developed as Mo alloys with insufficient strength and improved high-temperature strength. Yes.
[0004]
In the refractory metal alloy processed material such as Mo in which ultra-fine nitride is dispersed and subjected to multi-stage internal nitriding treatment, the inventors previously maintained a processed structure on at least the surface side of the processed material. It has been found that high toughness and high strength can be obtained by keeping it as it is (JP-A-2001-73060).
[0005]
Mo has excellent characteristics as described above, but does not have corrosion resistance to oxidizing acids such as hot concentrated sulfuric acid and nitric acid. Regarding improvement of corrosion resistance, the present inventors have developed a highly corrosion-resistant Mo-based composite material provided with a Mo 2 N layer having a thickness of 0.5 to 10 μm by nitriding Mo and an Mo-based alloy (Japanese Patent Laid-Open No. 11-286770). Issue gazette).
[0006]
[Problems to be solved by the invention]
Until now, only Ta metal has been useful as a device material under super severe corrosion conditions (for example, boiling concentrated sulfuric acid solution). However, Ta metal has low strength, particularly low strength at high temperatures, and is not suitable as a device / structural material that requires high strength. Further, the high corrosion resistance Mo-based composite material developed by the present inventors as a material to replace Ta metal has a drawback that the entire material becomes brittle as a result of recrystallization of the base material in the manufacturing process.
[0007]
Therefore, the present invention exhibits sufficiently high corrosion resistance and high strength even under super severe corrosion conditions such as boiling concentrated sulfuric acid solution (eg, 75% H 2 SO 4 aqueous solution (180 ° C.)), and also high strength at high temperatures. In addition, an object of the present invention is to provide an innovative material having unprecedented physical properties that have high toughness even at low temperatures and an efficient manufacturing method thereof.
[0008]
[Means for Solving the Problems]
The present inventors combined Mo nitriding treatment with internal nitriding treatment and external nitriding treatment to efficiently and inexpensively provide high strength and high toughness as well as excellent corrosion resistance against oxidizing acids. It was found that can be obtained.
[0009]
That is, according to the present invention, nitride particles produced by nitriding a nitride-forming metal element dissolved in the Mo matrix of a Mo alloy processed material are dispersed in the processed or recovered structure on the surface side inside the processed material. the layers are formed, further, the workpiece surface of the processed structure or restore tissue [delta]-MoN was generated externally nitride, γ-
[0010]
The present invention also provides that nitride particles produced by internal nitridation of a nitride-forming metal element dissolved in the Mo matrix of a Mo alloy processed material are dispersed in the processed or recovered structure on the surface side inside the processed material. And a thickness of 3 μm or less composed of at least one of δ-MoN, γ-Mo 2 N or β-Mo 2 N generated by external nitriding of the processed structure or the recovered structure on the surface of the processed material of Mo nitride layer is formed on the surface, processing the tissue into the inside held, Ri bilayer structure without recrystallization layer Tona, characterized by having a greater yield strength than the stage of the internal nitriding High corrosion resistance, high strength, high toughness Ni-treated Mo alloy processed material.
[0011]
Furthermore, the present invention provides at least three stages of internal nitriding by increasing the processing temperature stepwise to an alloy processed material in which Mo is the matrix and at least one of Ti, Zr, Hf, V, Nb, and Ta is dissolved. was carried out, followed by an above-described production method of nitriding Mo alloy workpiece, which comprises forming an external nitriding treatment to the surface lines have thickness 3μm following Mo nitride layer at 900 ° C. or less.
[0012]
Further, the present invention is the above-described method for producing a nitriding-treated Mo alloy processed material, characterized in that the internal nitriding treatment is performed with N 2 gas and then the external nitriding treatment is performed with NH 3 gas.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic diagram showing an example of a cross-sectional structure of a nitrided Mo alloy processed material of the present invention. The nitriding Mo alloy processed material of the present invention shown in FIG. 1 is a processed structure on the surface side inside the processed
[0014]
The processed material is obtained by rolling a dilute alloy containing Mo as a matrix and at least one of Ti, Zr, Hf, V, Nb, and Ta as a solid solution. The dilute alloy refers to an alloy containing a very small amount of a solute element concentration of a solid solution alloy of about 5% by weight or less.
[0015]
The high corrosion resistance, high strength and high toughness nitriding Mo alloy processed material of the present invention is produced by the following internal nitriding treatments (1) to (3) and external nitriding treatment (4). (1) to (3) in FIG. 2 are schematic views showing the structure of the processed material at each stage of the internal nitriding treatments (1) to (3) performed by gradually increasing the processing temperature.
[0016]
(1) First-stage nitriding treatment: Disperse ultrafine nitride particles of nitride-forming metal element by heating at a temperature lower than the recrystallization upper limit temperature and lower than the recrystallization lower limit temperature −200 ° C. in a nitriding atmosphere Let it form. In the first stage nitriding treatment, the nitride forming metal element dissolved in the matrix phase is preferentially nitrided by diffusing nitrogen into the work material while maintaining the work structure X1 of the dilute alloy work material. Sub-nano plate-like nitride particles of about 2 nm are formed and dispersed in the parent phase. Note that the preferential nitridation refers to a phenomenon in which only a nitride-forming element is preferentially nitrided, not a matrix metal. Due to the pinning effect of the precipitated particles generated by this nitriding treatment, the recrystallization temperature on the surface of the workpiece is increased.
[0017]
(2) Second stage nitriding treatment: Heating is performed at a temperature equal to or higher than the recrystallization lower limit temperature of the workpiece obtained by the first stage nitriding treatment in a nitriding atmosphere to grow and stabilize ultrafine nitride particles. The recrystallization temperature further increases due to the growth and stabilization of the precipitated particles by the second stage nitriding treatment. During nitriding, the inside of the work material is recrystallized and the work structure X2 remains. However, when the work material is relatively thin (3 mm or less), the work structure can be completely held up to the inside.
[0018]
(3) Nitriding treatment after the third stage: Heating is performed at a temperature equal to or higher than the recrystallization lower limit temperature of the workpiece obtained by the preceding stage treatment in a nitriding atmosphere to grow and stabilize the nitride particles. The nitriding treatment after the third stage is for the purpose of further growth and stabilization of the nitride particles while leaving the processed structure X3, and rod-like nitride particles having a thickness of about 10 nm and a length of about 50 nm are formed. Disperse uniformly in the Mo matrix. The nitriding treatment in the fourth and fifth stages after the third stage can be appropriately performed.
[0019]
(4) External nitriding treatment: Mo nitride layer is formed on the surface by strong nitriding treatment. The nitriding atmosphere may be any of an ammonia gas atmosphere, an N 2 gas atmosphere, a forming gas atmosphere (hydrogen gas: nitrogen gas = 1: 9 to 5: 5), and an atmosphere in which plasma discharge is performed on each of these three gases. . The formed Mo nitride is composed of at least one of δ-MoN, γ-Mo 2 N, and β-Mo 2 N. Between the Mo nitride layer on the surface and the workpiece inside the Mo parent phase so as worked structure or recovered structure remains.
[0020]
The relationship between the heat treatment temperature of the external nitriding treatment and the film thickness is shown in Table 1 below for the case of Mo-0.5 wt% Ti alloy. The film thickness increases as the heating temperature increases. From the viewpoint of corrosion resistance, it can be said that a thicker film is better, but it has been found that as the film is thickened, the toughness (bending properties) is lower than that at the stage of internal nitriding . Therefore, as a condition having both toughness and corrosion resistance, an external nitriding treatment (thickness of about 3 μm or less) of 900 ° C. or less is required.
[0021]
[Table 1]
The nitrided Mo alloy processed material of the present invention includes a semiconductor / ceramic / metal high-temperature firing support plate, a heater for a high-temperature heating furnace, a member for a high-temperature heating furnace, a structural material for a chemical facility / equipment in a corrosive environment (such as a high-temperature incinerator) In addition to supercritical / subcritical solution reactor materials, acid-resistant containers and tubes for oxidizing acids such as sulfuric acid and nitric acid, and equipment materials under super severe corrosion conditions (for example, boiling concentrated sulfuric acid solution) It is useful as an ultra-high temperature heater, metal injection mold, diesel engine injection nozzle, and the like.
[0023]
【Example】
Comparative Example 1
A plate-shaped Mo-1.0 wt% Ti alloy processed material having a thickness of 1 mm and a side of 10 mm was subjected to four-stage internal nitriding while changing the heating temperature in an N 2 gas (1 atm) air stream. The heating temperature was 900 ° C. → 950 ° C. → 1200 ° C. → 1500 ° C.
[0024]
By this multi-stage nitriding treatment, the surface area of the workpiece (from the surface to a depth of about 200 μm) retained the processing / recovery structure (inside, the recrystallized structure), and fine TiN particles were dispersed and precipitated. Further, an external nitridation treatment was performed at 1000 ° C. for 4 hours in a stream of NH 3 gas (1 atm) to form a Mo nitride (γ-Mo 2 N, etc.) layer having a thickness of 14.0 μm on the surface of the processed material.
[0025]
In this processed material, the surface of the processed material is a Mo nitride layer, the inner side is a solid solution element nitride layer having Mo as a parent phase of the processed and recovered crystal grain structure in which fine TiN particles are dispersed and precipitated, and the inner side is It exhibits a three-layer structure of a Mo alloy layer having a large equiaxed recrystallized grain structure. However, the toughness was lower than in the stage where the surface of the Mo nitride layer was thick and internally nitrided.
[0026]
Next, FIG. 3 shows the results of a corrosion test conducted in a 75% concentrated sulfuric acid boiling solution (185 ° C.) in order to examine the corrosion resistance under severe corrosion environment. In FIG. 3, the result of pure Mo is also shown as a comparative sample. The corrosion rate of pure Mo is as high as 8 mm / year, and it corrodes vigorously, whereas the processed material of Comparative Example 1 does not corrode as much as 0.076 mm / year and is almost completely corrosion resistant (corrosion rate: <0.05 mm / year). Year).
[0027]
Example 1
The Mo-0.5 wt% Ti alloy processed material was subjected to three-stage internal nitriding while changing the heating temperature in an N 2 gas (1 atm) airflow. The temperature was set to 900 ° C. → 1200 ° C. → 1500 ° C. The Mo alloy subjected to the three-stage internal nitriding treatment was further heated at 900 ° C. for 4 hours (external nitriding treatment) in a 1 atm NH 3 stream, and Mo nitride (δ-MoN, γ-Mo 2 N) was formed on the surface of the workpiece. The layer was formed uniformly. By this multi-stage nitriding treatment, fine TiN particles were dispersed and precipitated, the inner nitride layer of the processed / recovered crystal grain structure was 310 μm, and the outer nitride layer of Mo nitride was 2.8 μm. Further, from the X-ray diffraction pattern on the surface of the processed material, formation of an outer nitride layer of δ-MoN and γ-Mo 2 N was recognized.
[0028]
FIG. 3 shows the results of a corrosion test conducted in a 75% concentrated sulfuric acid boiling solution (185 ° C.). The processed material of Example 2 is hardly corroded at 0.046 mm / year, and exhibits complete corrosion resistance (corrosion rate: <0.05 mm / year).
[0029]
Further, the bending strength (yield strength and maximum strength) at room temperature of the processed material subjected to the three-stage internal nitriding treatment (900 ° C. → 1200 ° C. → 1500 ° C.) and the external nitriding treatment (900 ° C.-4 h) after that in Example 1. ) Is shown in Table 2. FIG. 4 shows (a) a cross-sectional structure photograph and (b) a macro photograph of a specimen after a bending test.
[0030]
From Table 2, the yield strength and the maximum strength of the work material (Mo nitride layer thickness: about 2.8 μm) subjected to the external nitriding treatment at 900 ° C. for 4 hours in Example 1 are both three-stage internal nitriding treatment materials (high strength). It has been found that the yield stress value is larger than that obtained by internal nitriding by an external nitriding treatment .
[0031]
That is, it became clear that the nitrided Mo alloy processed material of the present invention has extremely high strength as well as high corrosion resistance.
[0032]
[Table 2]
【The invention's effect】
The present invention provides a nitriding-treated Mo alloy processed material that has high corrosion resistance against oxidizing acids as well as high strength and high toughness efficiently and inexpensively only by nitriding treatment, and can cope with an extreme corrosion environment. In addition to various applications of conventional Mo or Mo alloys, various materials such as equipment materials under extremely severe corrosion conditions (for example, boiling concentrated sulfuric acid solution), ultra-high temperature heaters, metal injection molds, injection nozzles for diesel engines, etc. This contributes to the practical use of Mo materials for applications.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a cross-sectional structure of a nitrided Mo alloy processed material of the present invention.
FIG. 2 is a schematic diagram showing the structure of the workpiece in each stage of internal nitriding treatments (1) to (3) in the process for producing the nitriding Mo alloy workpiece of the present invention.
FIG. 3 is a graph showing corrosion test results of a nitrided Mo alloy processed material obtained in Comparative Example 1 and Example 1 and a comparative example (pure Mo material).
4 is a drawing-substitute sectional structure photograph (a) of the nitrided Mo alloy workpiece obtained in Example 1, and a drawing-substitute macro photograph (b) of the nitrided Mo alloy workpiece specimen after the bending test. FIG.
Claims (4)
さらに、該加工材表面の加工組織または回復組織が外部窒化されて生成したδ−ＭｏＮ、γ−Ｍｏ ２ Ｎまたはβ−Ｍｏ ２ Ｎの少なくとも１種からなる厚さ３μｍ以下のＭｏ窒化物層が表面に形成されており、
該加工材内部が再結晶組織層である、
三層構造からなり、
前記内部窒化した段階よりも大きな降伏強度を有することを特徴とする高耐食性・高強度・高靭性窒化処理Ｍｏ合金加工材。 A layer is formed in which nitride particles formed by nitriding a nitride-forming metal element solid-solved in the Mo matrix of the Mo alloy processed material are dispersed in the processed structure or the recovered structure on the surface side inside the processed material ,
Furthermore, processed structure or restore tissue of the workpiece surface [delta]-MoN was generated externally nitride, gamma-Mo 2 N, or beta-Mo 2 at least one thickness 3μm following Mo nitride layer consisting of N is Formed on the surface ,
The inside of the processed material is a recrystallized structure layer,
It consists of a three-layer structure,
A high corrosion resistance, high strength, high toughness nitriding Mo alloy processed material characterized by having a higher yield strength than the internal nitriding stage .
さらに、該加工材表面の加工組織または回復組織が外部窒化されて生成したδ−ＭｏＮ、γ−ＭｏFurthermore, δ-MoN, γ-Mo generated by external nitriding of the processed structure or the recovered structure on the surface of the processed material ２2 Ｎまたはβ−ＭｏN or β-Mo ２2 Ｎの少なくとも１種からなる厚さ３μｍ以下のＭｏ窒化物層が表面に形成されている、A Mo nitride layer made of at least one of N and having a thickness of 3 μm or less is formed on the surface;
内部まで加工組織が保持され、再結晶層のない二層構造からなり、Processed structure is maintained to the inside, and consists of a two-layer structure without a recrystallized layer.
前記内部窒化した段階よりも大きな降伏強度を有することを特徴とする高耐食性・高強度・高靭性窒化処理Ｍｏ合金加工材。A high corrosion resistance, high strength, and high toughness nitriding Mo alloy processed material having a yield strength greater than that of the internal nitriding stage.
Priority Applications (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002098039A JP4302930B2 (en) | 2002-03-29 | 2002-03-29 | High corrosion resistance, high strength, high toughness Nitrided Mo alloy processed material and its manufacturing method |
| PCT/JP2003/003912 WO2003083157A1 (en) | 2002-03-29 | 2003-03-27 | NITRIDED Mo ALLOY WORKED MATERIAL HAVING HIGH CORROSION RESISTANCE, HIGH STRENGTH AND HIGH TOUGHNESS AND METHOD FOR PRODUCTION THEREOF |
| CA002480787A CA2480787A1 (en) | 2002-03-29 | 2003-03-27 | Nitrided mo alloy worked material having high corrosion resistance, high strength and high toughness and method for production thereof |
| AT03745433T ATE533870T1 (en) | 2002-03-29 | 2003-03-27 | NITRIDATED MO ALLOY MATERIAL WITH HIGH CORROSION RESISTANCE, HIGH STRENGTH AND HIGH TOUGHNESS AND PRODUCTION PROCESS THEREOF |
| EP03745433A EP1491651B1 (en) | 2002-03-29 | 2003-03-27 | NITRIDED Mo ALLOY WORKED MATERIAL HAVING HIGH CORROSION RESISTANCE, HIGH STRENGTH AND HIGH TOUGHNESS AND METHOD FOR PRODUCTION THEREOF |
| US10/509,156 US20060054247A1 (en) | 2002-03-29 | 2003-03-27 | Nitrided mo alloy worked material having high corrosion resistance, high strength and high toughness and method for production thereof |
| KR1020047015093A KR100611725B1 (en) | 2002-03-29 | 2003-03-27 | Nitrided Mo alloy worked material having high corrosion resistance, high strenth and high toughness and method for prodution thereof |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002098039A JP4302930B2 (en) | 2002-03-29 | 2002-03-29 | High corrosion resistance, high strength, high toughness Nitrided Mo alloy processed material and its manufacturing method |
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| JP4302930B2 true JP4302930B2 (en) | 2009-07-29 |
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| US (1) | US20060054247A1 (en) |
| EP (1) | EP1491651B1 (en) |
| JP (1) | JP4302930B2 (en) |
| KR (1) | KR100611725B1 (en) |
| AT (1) | ATE533870T1 (en) |
| CA (1) | CA2480787A1 (en) |
| WO (1) | WO2003083157A1 (en) |
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| JP4255877B2 (en) * | 2004-04-30 | 2009-04-15 | 株式会社アライドマテリアル | High-strength and high recrystallization temperature refractory metal alloy material and its manufacturing method |
| JP4558572B2 (en) * | 2005-04-25 | 2010-10-06 | 株式会社アライドマテリアル | High heat resistant molybdenum alloy and manufacturing method thereof |
| CN103409718B (en) * | 2013-05-15 | 2015-08-26 | 厦门虹鹭钨钼工业有限公司 | A kind of High-temperature oxidation-resistant molybdenum material and production method thereof |
| CN106535826A (en) | 2014-06-24 | 2017-03-22 | 怡康医疗股份有限公司 | Improved metal alloys for medical devices |
| US10682437B2 (en) | 2015-07-02 | 2020-06-16 | Mirus Llc | Molybdenum alloys for medical devices |
| WO2017151548A1 (en) | 2016-03-04 | 2017-09-08 | Mirus Llc | Stent device for spinal fusion |
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| JPS59208066A (en) * | 1983-05-13 | 1984-11-26 | Toshiba Corp | Method for working internally nitrided molybdenum-zirconium alloy |
| SU1747535A1 (en) * | 1990-07-29 | 1992-07-15 | Научно-исследовательский физико-химический институт им.Л.Я.Карпова | Method of molybdenum nitriding |
| JPH11286770A (en) | 1998-04-01 | 1999-10-19 | Yoshioka Takashi | High corrosion resistance molybdenum-based composite material and its production |
| JP4307649B2 (en) * | 1999-09-06 | 2009-08-05 | 独立行政法人科学技術振興機構 | High toughness / high strength refractory metal alloy material and method for producing the same |
-
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- 2003-03-27 CA CA002480787A patent/CA2480787A1/en not_active Abandoned
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- 2003-03-27 EP EP03745433A patent/EP1491651B1/en not_active Expired - Fee Related
- 2003-03-27 AT AT03745433T patent/ATE533870T1/en active
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Also Published As
| Publication number | Publication date |
|---|---|
| ATE533870T1 (en) | 2011-12-15 |
| EP1491651A4 (en) | 2008-08-27 |
| KR20040105796A (en) | 2004-12-16 |
| CA2480787A1 (en) | 2003-10-09 |
| EP1491651A1 (en) | 2004-12-29 |
| EP1491651B1 (en) | 2011-11-16 |
| WO2003083157A1 (en) | 2003-10-09 |
| KR100611725B1 (en) | 2006-08-10 |
| JP2003293116A (en) | 2003-10-15 |
| US20060054247A1 (en) | 2006-03-16 |
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