JP4925202B2 - Composition-gradient molybdenum-niobium alloy powder - Google Patents
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- 239000000843 powder Substances 0.000 title claims description 207
- DTSBBUTWIOVIBV-UHFFFAOYSA-N molybdenum niobium Chemical compound [Nb].[Mo] DTSBBUTWIOVIBV-UHFFFAOYSA-N 0.000 title claims description 74
- 229910001257 Nb alloy Inorganic materials 0.000 title claims description 4
- 239000010955 niobium Substances 0.000 claims description 81
- 229910045601 alloy Inorganic materials 0.000 claims description 67
- 239000000956 alloy Substances 0.000 claims description 67
- 239000000203 mixture Substances 0.000 claims description 34
- 239000002245 particle Substances 0.000 claims description 29
- 239000006104 solid solution Substances 0.000 claims description 29
- 229910052750 molybdenum Inorganic materials 0.000 claims description 28
- 229910052758 niobium Inorganic materials 0.000 claims description 26
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 13
- 239000011733 molybdenum Substances 0.000 claims description 11
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 11
- 238000006722 reduction reaction Methods 0.000 description 30
- 238000005275 alloying Methods 0.000 description 26
- 238000009792 diffusion process Methods 0.000 description 26
- 230000009467 reduction Effects 0.000 description 22
- 238000000034 method Methods 0.000 description 21
- QXYJCZRRLLQGCR-UHFFFAOYSA-N dioxomolybdenum Chemical compound O=[Mo]=O QXYJCZRRLLQGCR-UHFFFAOYSA-N 0.000 description 18
- 238000010438 heat treatment Methods 0.000 description 18
- 238000005245 sintering Methods 0.000 description 18
- 239000002994 raw material Substances 0.000 description 15
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 11
- 238000011105 stabilization Methods 0.000 description 11
- 239000013078 crystal Substances 0.000 description 10
- 239000001257 hydrogen Substances 0.000 description 10
- 229910052739 hydrogen Inorganic materials 0.000 description 10
- 238000002156 mixing Methods 0.000 description 10
- 230000008569 process Effects 0.000 description 10
- 230000006641 stabilisation Effects 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 9
- 239000011812 mixed powder Substances 0.000 description 8
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Chemical compound O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 description 8
- 239000002344 surface layer Substances 0.000 description 8
- 238000009826 distribution Methods 0.000 description 7
- 230000007423 decrease Effects 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- BFRGSJVXBIWTCF-UHFFFAOYSA-N niobium monoxide Chemical compound [Nb]=O BFRGSJVXBIWTCF-UHFFFAOYSA-N 0.000 description 6
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 238000005452 bending Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 229910000476 molybdenum oxide Inorganic materials 0.000 description 4
- 229910000484 niobium oxide Inorganic materials 0.000 description 4
- PQQKPALAQIIWST-UHFFFAOYSA-N oxomolybdenum Chemical compound [Mo]=O PQQKPALAQIIWST-UHFFFAOYSA-N 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 229910003460 diamond Inorganic materials 0.000 description 2
- 239000010432 diamond Substances 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- HFLAMWCKUFHSAZ-UHFFFAOYSA-N niobium dioxide Chemical compound O=[Nb]=O HFLAMWCKUFHSAZ-UHFFFAOYSA-N 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 238000000859 sublimation Methods 0.000 description 2
- 230000008022 sublimation Effects 0.000 description 2
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000009770 conventional sintering Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000005551 mechanical alloying Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical compound S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 description 1
- 229910052982 molybdenum disulfide Inorganic materials 0.000 description 1
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Inorganic materials O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 description 1
- 238000005121 nitriding Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006557 surface reaction Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000002411 thermogravimetry Methods 0.000 description 1
- 229920001187 thermosetting polymer Polymers 0.000 description 1
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Description
この発明は、粉末表面から粉末中心部へ向かうにしたがってニオブ成分の含有割合が変化する組成傾斜型モリブデン−ニオブ合金粉末に関し、特に、焼結用の原料粉末として用いた場合に、焼結性にすぐれ、しかも、焼結体が高密度、微細結晶組織を有し、耐熱性にすぐれ、均質かつすぐれた機械的特性を有するようになる組成傾斜型モリブデン−ニオブ合金粉末に関するものである。 The present invention relates to a composition-graded molybdenum-niobium alloy powder in which the content ratio of the niobium component changes from the powder surface toward the center of the powder, and in particular, when used as a raw material powder for sintering, In addition, the present invention relates to a composition-gradient molybdenum-niobium alloy powder having a sintered body having a high density, a fine crystal structure, excellent heat resistance, homogeneous and excellent mechanical properties.
モリブデン材料は、高融点であり、熱膨張率が小さく、機械的強度・靭性・加工性に優れ、また、電気伝導性・熱伝導率も高く、さらに、耐熱性・耐蝕性にもすぐれていることから、これらの特性を生かし、従来から、発熱体、ボート、熱反射板等の高温炉用材料、半導体部品、高温成形金型材料、耐蝕構造材、原子炉構造材等として幅広い分野で利用されている。
このようなモリブデン材料からなる各種製品の製造法としては、大別して溶製法と焼結法が知られているが、溶製法により製造したＭｏ製品は、粗大結晶粒となりやすく、強度の低下が生じ、また、製品特性が不均質なものとなりやすい。
そこで、最近では、焼結法によるモリブデン製品の製造が主流となっており、例えば、
（ａ）モリブデン粉末に、ＣｅＯ２粉末、Ｔｉ粉末、Ｚｒ粉末、Ｈｆ粉末、Ｖ粉末、Ｎｂ粉末、Ｔａ粉末等の粉末を添加混合し、プレス成形後、１６００〜１８００℃程度の水素雰囲気中で焼結する方法、
（ｂ）モリブデン粉末に、ＴｉＣ粉末、ＺｒＣ粉末、ＨｆＣ粉末等を添加し、メカニカルアロイング処理した後、アルゴンガス中１３００℃で焼結する方法、
（ｃ）二硫化モリブデン粉末に硝酸ランタン溶液を加え、乾燥後水素還元してモリブデン−Ｌａ２Ｏ３粉末を作成し、これをプレス成形し、その後、水素気流中約１８００℃で焼結する方法、等が知られている。
Molybdenum material has a high melting point, a low coefficient of thermal expansion, excellent mechanical strength, toughness, and workability, high electrical conductivity and thermal conductivity, and excellent heat resistance and corrosion resistance. Therefore, taking advantage of these characteristics, it has been widely used in a wide range of fields as materials for high-temperature furnaces such as heating elements, boats, heat reflectors, semiconductor parts, high-temperature molding mold materials, corrosion-resistant structural materials, and reactor structural materials. Has been.
As a manufacturing method of various products made of such molybdenum materials, a melting method and a sintering method are roughly classified. However, Mo products manufactured by the melting method tend to be coarse crystal grains, resulting in a decrease in strength. Also, product characteristics tend to be inhomogeneous.
Therefore, recently, the production of molybdenum products by the sintering method has become mainstream, for example,
(A) Powders such as CeO 2 powder, Ti powder, Zr powder, Hf powder, V powder, Nb powder, and Ta powder are added to molybdenum powder and mixed, and after press molding, in a hydrogen atmosphere at about 1600 to 1800 ° C. A method of sintering,
(B) A method of adding TiC powder, ZrC powder, HfC powder, etc. to molybdenum powder, performing mechanical alloying, and then sintering at 1300 ° C. in argon gas,
(C) A method in which a lanthanum nitrate solution is added to molybdenum disulfide powder, dried and then hydrogen-reduced to produce molybdenum-La 2 O 3 powder, which is press-molded and then sintered at about 1800 ° C. in a hydrogen stream. , Etc. are known.
そして、上記従来の焼結法により作製されたモリブデン系焼結体に対しては、鍛造、圧延等の塑性加工、あるいは、アニール、内部窒化等の熱処理を施すことにより、焼結体の強度、靭性、加工性、異方性等の改善が図られているが、このような従来のモリブデン焼結体では、より過酷な使用条件下での要求に応えるためには、未だ十分な機械的特性を有しているとは言い難い。 And, for the molybdenum-based sintered body produced by the conventional sintering method, the strength of the sintered body is obtained by performing plastic working such as forging and rolling, or heat treatment such as annealing and internal nitriding, Improvements in toughness, workability, anisotropy, etc. have been made, but such conventional molybdenum sintered bodies still have sufficient mechanical properties to meet the demands under more severe use conditions. It is hard to say that it has.
そこで、本発明は、モリブデン−ニオブ（以下、Ｍｏ−Ｎｂで示す）系焼結体を製造するに好適な焼結用原料粉末としてのＭｏ−Ｎｂ合金粉末を提供することを目的とするものであり、具体的には、このＭｏ−Ｎｂ合金粉末を焼結用原料粉末として用いることにより、焼結に際しての原料粉末の焼結性を向上させ、その結果として、焼結体が、高密度、微細結晶粒組織、耐熱性と均質かつすぐれた機械的特性を有するようになるＭｏ−Ｎｂ合金粉末を提供せんとするものである。 Then, this invention aims at providing the Mo-Nb alloy powder as a raw material powder for sintering suitable for manufacturing a molybdenum-niobium (hereinafter referred to as Mo-Nb) -based sintered body. Yes, specifically, by using this Mo-Nb alloy powder as a raw material powder for sintering, the sinterability of the raw material powder during sintering is improved. As a result, the sintered body has a high density, It is an object of the present invention to provide a Mo—Nb alloy powder that has a fine grain structure, heat resistance, and uniform and excellent mechanical properties.
本発明者らは、かかる課題を解決すべく、Ｍｏ−Ｎｂ系焼結体を製造する際に用いる焼結原料粉末について、鋭意研究を行なったところ、
（ａ）従来は、Ｍｏ粉末単体とＮｂ粉末単体とを混合し、この混合粉末を焼結原料粉末として用いていたが、Ｍｏ粉末に代えてＭｏ酸化物粉末を、また、Ｎｂ粉末に代えてＮｂ酸化物粉末を用い、このＭｏ酸化物粉末とＮｂ酸化物粉末とを所定配合割合となるように混合し、この混合酸化物粉末を５〜５０℃／分の昇温速度で１３５０〜１７００℃の温度にまで昇温し、水素雰囲気中、かつ、この温度範囲で、１〜６時間加熱保持することにより焼結原料粉末を調製すると、Ｎｂ酸化物単体粉末では還元することが難しい比較的低温度の領域（上記１３５０〜１７００℃という温度領域）であっても、Ｍｏ酸化物とともにＮｂ酸化物とが容易に還元される酸化物の還元反応が生じ、さらに、還元されたＭｏとＮｂとの間で、拡散・合金化反応が生じ、粉末表層部から粉末中心部へ向かうにしたがってＮｂ成分の含有量が変化する組成傾斜型のＭｏ−Ｎｂ固溶体からなるＭｏ−Ｎｂ合金粉末が形成されること。
In order to solve such problems, the present inventors have conducted intensive research on the sintering raw material powder used when producing the Mo—Nb-based sintered body.
(A) Conventionally, Mo powder alone and Nb powder alone were mixed, and this mixed powder was used as a sintering raw material powder, but instead of Mo powder, Mo oxide powder was replaced with Nb powder. Using the Nb oxide powder, the Mo oxide powder and the Nb oxide powder are mixed so as to have a predetermined mixing ratio, and the mixed oxide powder is 1350-1700 ° C. at a heating rate of 5-50 ° C./min. When the sintered raw material powder is prepared by heating and holding in this temperature range for 1 to 6 hours in a hydrogen atmosphere, it is relatively low that it is difficult to reduce with the Nb oxide simple substance powder. Even in the temperature range (the temperature range of 1350 ° C. to 1700 ° C.), the reduction reaction of the oxide that easily reduces the Nb oxide together with the Mo oxide occurs, and further, the reduced Mo and Nb Diffusion / alloying reaction Occurs, the Mo-Nb alloy powder content of Nb component toward the powder surface portion to the powder center consists of Mo-Nb solid solution composition gradient type of change is formed.
（ｂ）上記（ａ）により得たＭｏ−Ｎｂ合金粉末を焼結原料粉末として用い、通常の焼結法によりＭｏ−Ｎｂ系焼結体を製造したところ、組成傾斜型のＭｏ−Ｎｂ固溶体からなる原料粉末相互の表面反応の活性化により焼結性が向上し、高密度の焼結体が形成されるとともに、原料粉末自体には組成傾斜がある（即ち、原料粉末をミクロ的にみれば、粉体内では不均質な組成分布構造となっている）にもかかわらず、これが焼結されることによって、得られた焼結体全体にわたって、あたかもＭｏ−Ｎｂ均一固溶体によって形成されたが如き均質な特性を示し、しかも、抗折力、硬度、耐熱性等が向上し、さらに、均一で微細かつ緻密な結晶粒組織を有するため、均質かつすぐれた機械的特性を備えたＭｏ−Ｎｂ系焼結体が得られること。
以上、（ａ）、（ｂ）に示される研究結果を得たのである。
(B) Using the Mo—Nb alloy powder obtained in the above (a) as a sintering raw material powder, a Mo—Nb sintered body was produced by a normal sintering method. From the composition gradient type Mo—Nb solid solution, The activation of the surface reaction between the raw material powders improves the sinterability and forms a high-density sintered body, and the raw material powder itself has a composition gradient (that is, if the raw material powder is viewed microscopically). In spite of the fact that it has a non-homogeneous composition distribution structure in the powder), this is sintered, so that it is homogeneous as if it were formed by the Mo—Nb homogeneous solid solution over the entire sintered body obtained. Mo-Nb-based firing with uniform mechanical properties and excellent mechanical properties because it has excellent characteristics, has improved bending strength, hardness, heat resistance, etc., and has a uniform, fine and dense crystal grain structure. A knot is obtained.
As described above, the research results shown in (a) and (b) were obtained.
この発明は、上記研究結果に基づいてなされたものであって、
「平均粒径が０．５〜１０μｍのモリブデン（Ｍｏ）とニオブ（Ｎｂ）の固溶体からなる合金粉末であって、該合金粉末におけるモリブデン（Ｍｏ）の平均含有量は９０〜９９ａｔ％、ニオブ（Ｎｂ）の平均含有量は１〜１０ａｔ％であり、しかも、合金粉末表層部における固溶ニオブ（Ｎｂ）含有量は、合金粉末中心部における固溶ニオブ（Ｎｂ）含有量よりも大きい組成傾斜型のモリブデン（Ｍｏ）とニオブ（Ｎｂ）の固溶体からなるモリブデン−ニオブ（Ｍｏ−Ｎｂ）合金粉末。」
に特徴を有するものである。
This invention was made based on the above research results,
“Alloy powder composed of a solid solution of molybdenum (Mo) and niobium (Nb) having an average particle size of 0.5 to 10 μm, and the average content of molybdenum (Mo) in the alloy powder is 90 to 99 at%, niobium ( The average content of Nb) is 1 to 10 at%, and the solid solution niobium (Nb) content in the surface portion of the alloy powder is larger than the content of solid solution niobium (Nb) in the center portion of the alloy powder. Molybdenum-Niobium (Mo-Nb) alloy powder comprising a solid solution of molybdenum (Mo) and niobium (Nb). "
It has the characteristics.
以下に、この発明を、より具体的かつ詳細に説明する。 Hereinafter, the present invention will be described more specifically and in detail.
まず、この発明でいう組成傾斜型Ｍｏ−Ｎｂ合金粉末とは、図１に示されるように、合金粉末表層部から合金粉末中心部へ向かって、固溶Ｎｂ含有量（以下、単にＮｂ含有量という）が次第に少なくなるようなＮｂ濃度分布を示すＭｏ−Ｎｂ固溶体からなる合金粉末をいう。
図１には、最大直径約６μｍのＭｏ−Ｎｂ合金粉末の表層部、中間部、中心部におけるＮｂ含有量が等高線で示されており、表層部におけるＮｂ含有量は７ａｔ％以上、中間部では５ａｔ％、また、中心部におけるＮｂ含有量は３ａｔ％であること、即ち、合金粉末表層部から合金粉末中心部へ向かって、Ｎｂ含有量が次第に少なくなっていることがわかる。
First, the composition gradient type Mo—Nb alloy powder referred to in the present invention, as shown in FIG. 1, is a solid solution Nb content (hereinafter simply referred to as Nb content) from the surface portion of the alloy powder toward the center of the alloy powder. Refers to an alloy powder made of a Mo-Nb solid solution showing an Nb concentration distribution that gradually decreases.
In FIG. 1, the Nb content in the surface layer portion, the middle portion, and the center portion of the Mo—Nb alloy powder having a maximum diameter of about 6 μm is indicated by contour lines, and the Nb content in the surface layer portion is 7 at% or more. It can be seen that the Nb content is 5 at% and the Nb content in the center is 3 at%, that is, the Nb content gradually decreases from the alloy powder surface layer to the alloy powder center.
この発明では、組成傾斜型Ｍｏ−Ｎｂ合金粉末の平均粒径を０．５〜１０μｍと定めているが、平均粒径が０．５μｍ未満では、合金粉末全体がＭｏ−Ｎｂの均一固溶体となってしまい、組成傾斜型のＭｏ−Ｎｂ固溶体を得ることができない。
一方、前記したように、この発明の組成傾斜型Ｍｏ−Ｎｂ合金粉末は、例えば、酸化モリブデン粉末と酸化ニオブ粉末とを混合し、この混合粉末に特定の処理を施し拡散を行わせることにより得ることができるのであるが、合金粉末の平均粒径が１０μｍを超えると、粉末中心部にまでＮｂが十分拡散せず、或いは、十分な拡散を行うのに長時間を要し、粉末中心部近傍では、Ｍｏ−Ｎｂ固溶体を形成することができなくなり、また、焼結性の低下を招くようになるので、組成傾斜型Ｍｏ−Ｎｂ合金粉末の平均粒径を０．５〜１０μｍと定めた。
In this invention, the average particle size of the composition gradient type Mo—Nb alloy powder is determined to be 0.5 to 10 μm. However, if the average particle size is less than 0.5 μm, the entire alloy powder becomes a uniform solid solution of Mo—Nb. Therefore, a composition gradient type Mo—Nb solid solution cannot be obtained.
On the other hand, as described above, the composition gradient type Mo—Nb alloy powder of the present invention is obtained, for example, by mixing molybdenum oxide powder and niobium oxide powder, subjecting this mixed powder to specific treatment, and performing diffusion. However, if the average particle size of the alloy powder exceeds 10 μm, Nb does not diffuse sufficiently to the center of the powder, or it takes a long time to perform sufficient diffusion, and the vicinity of the center of the powder. Then, since it becomes impossible to form a Mo-Nb solid solution and a sinterability fall will be caused, the average particle diameter of the composition inclination type Mo-Nb alloy powder was determined to be 0.5-10 micrometers.
また、この発明では、合金粉末のＭｏの平均含有量は９０〜９９ａｔ％、Ｎｂの平均含有量は１〜１０ａｔ％と定めているが、Ｍｏ、Ｎｂの平均含有量とは、酸化モリブデン粉末と酸化ニオブ粉末とを混合して合金粉末を形成する際の、酸化モリブデン粉末、酸化ニオブ粉末の中にそれぞれ含有されるＭｏ量、Ｎｂ量と、それぞれの粉末の配合割合とから求めることができる。
そして、組成傾斜型Ｍｏ−Ｎｂ固溶体からなる合金粉末におけるＮｂの平均含有量が１ａｔ％未満では、Ｎｂ量の絶対量が少なく、Ｍｏ粉末の中心部にまでＮｂが十分拡散しないため、組成傾斜型のＭｏ−Ｎｂ固溶体を形成することができず、一方、Ｎｂの平均含有量が１０ａｔ％を超えるようになると、酸化ニオブ粉末の還元反応速度が低下し、同時に、Ｍｏ、Ｎｂの合金化反応速度も低下するため、合金粉末中におけるＮｂの平均含有量は１〜１０ａｔ％、Ｍｏの平均含有量は９０〜９９ａｔ％と定めた。
In this invention, the average content of Mo in the alloy powder is 90 to 99 at% and the average content of Nb is 1 to 10 at%. The average content of Mo and Nb is the molybdenum oxide powder and It can be determined from the amount of Mo and Nb contained in each of the molybdenum oxide powder and the niobium oxide powder and the blending ratio of each powder when the alloy powder is formed by mixing the niobium oxide powder.
And if the average content of Nb in the alloy powder composed of the composition gradient type Mo—Nb solid solution is less than 1 at%, the absolute amount of Nb is small, and Nb does not sufficiently diffuse to the center of the Mo powder. On the other hand, when the average content of Nb exceeds 10 at%, the reduction reaction rate of the niobium oxide powder decreases, and at the same time, the alloying reaction rate of Mo and Nb. Therefore, the average content of Nb in the alloy powder was determined to be 1 to 10 at%, and the average content of Mo was determined to be 90 to 99 at%.
次に、この発明の組成傾斜型Ｍｏ−Ｎｂ固溶体からなるＭｏ−Ｎｂ合金粉末は、例えば、Ｍｏ酸化物粉末とＮｂ酸化物粉末からなる混合酸化物粉末を調製し、該混合酸化物粉末を還元・拡散・合金化処理することによって製造することができるが、各工程について以下に簡単に説明する。 Next, the Mo-Nb alloy powder comprising the composition gradient type Mo-Nb solid solution of the present invention is prepared, for example, by preparing a mixed oxide powder comprising Mo oxide powder and Nb oxide powder, and reducing the mixed oxide powder. Although it can be manufactured by diffusion / alloying, each process will be briefly described below.
（１）Ｍｏ酸化物粉末とＮｂ酸化物粉末からなる混合酸化物粉末の調製；
Ｍｏ酸化物粉末としては、具体的には、三酸化モリブデン（ＭｏＯ３）、二酸化モリブデン（ＭｏＯ２）等の各粉末を単独で又は混合して用いることができ、また、Ｎｂ酸化物粉末としては、五酸化ニニオブ（Ｎｂ２Ｏ５）、二酸化ニオブ（ＮｂＯ２）、一酸化ニオブ（ＮｂＯ）の各粉末を単独で又は混合して用いることができる。
Ｍｏ酸化物粉末とＮｂ酸化物粉末との混合粉末は、各酸化物粉末の配合割合に応じたＭｏ含有量とＮｂ含有量の比が、ほぼそのまま、最終的に得られるＭｏ−Ｎｂ合金粉末の、Ｍｏ、Ｎｂの平均含有量となるので、目標とする合金粉末の成分組成割合に応じて、Ｍｏ酸化物粉末とＮｂ酸化物粉末との配合量を決定し、これを混合してＭｏ酸化物粉末とＮｂ酸化物粉末との混合酸化物粉末を調製する。
Ｍｏ酸化物粉末とＮｂ酸化物粉末、あるいはこれらを混合した混合酸化物粉末は、還元反応、拡散反応および合金化反応を均一に進行させるために、その粒度を０．５〜３．０μｍ程度に調製することが好ましく、また、Ｍｏ酸化物粉末とＮｂ酸化物粉末の純度も、最終的に得られるＭｏ−Ｎｂ系焼結体の特性に影響を与えるので、それぞれ純度９９．９９％以上のものを使用することが望ましい。
(1) Preparation of mixed oxide powder comprising Mo oxide powder and Nb oxide powder;
Specifically, as the Mo oxide powder, each powder of molybdenum trioxide (MoO 3 ), molybdenum dioxide (MoO 2 ) and the like can be used alone or as a mixture, and as the Nb oxide powder, Each powder of niobium pentoxide (Nb 2 O 5 ), niobium dioxide (NbO 2 ), and niobium monoxide (NbO) can be used alone or in combination.
In the mixed powder of Mo oxide powder and Nb oxide powder, the ratio of Mo content and Nb content according to the blending ratio of each oxide powder is almost the same as the Mo-Nb alloy powder finally obtained. Since the average content of Mo and Nb is determined, the blending amount of the Mo oxide powder and the Nb oxide powder is determined according to the component composition ratio of the target alloy powder, and this is mixed to obtain the Mo oxide. A mixed oxide powder of powder and Nb oxide powder is prepared.
Mo oxide powder and Nb oxide powder, or mixed oxide powder obtained by mixing these powders, has a particle size of about 0.5 to 3.0 μm in order to allow the reduction reaction, diffusion reaction and alloying reaction to proceed uniformly. Preferably, the purity of the Mo oxide powder and the Nb oxide powder also affects the properties of the Mo-Nb-based sintered body finally obtained. It is desirable to use
（２）還元・拡散・合金化処理；
還元・拡散・合金化処理は、上記Ｍｏ酸化物粉末とＮｂ酸化物粉末との混合酸化物粉末を水素雰囲気下で加熱することにより、酸化物の還元反応を進行させるとともに、ＭｏとＮｂの拡散・合金化反応を同時に進行させて、組成傾斜型Ｍｏ−Ｎｂ固溶体からなるＭｏ−Ｎｂ合金粉末を形成する処理である。
Ｍｏ酸化物粉末単体の場合、約１０００℃下で還元反応が進行するが、Ｎｂ酸化物粉末単体では、２０００℃程度まで温度を高めても還元反応は進行しないが、本発明のように、それぞれの酸化物粉末を混合し、この混合酸化物粉末を還元すると、そのメカニズムはまだ十分に解明されていないが、Ｎｂ酸化物単体の還元温度に比してはるかに低い温度である１３５０〜１７００℃の温度範囲で還元することができ、さらに、それと同時に、還元によって生成したＭｏとＮｂの拡散・合金化反応を生じさせることができる。
(2) Reduction / diffusion / alloying treatment;
The reduction / diffusion / alloying treatment is performed by heating the mixed oxide powder of the Mo oxide powder and the Nb oxide powder in a hydrogen atmosphere to promote the reduction reaction of the oxide and the diffusion of Mo and Nb. -It is the process which advances alloying reaction simultaneously and forms the Mo-Nb alloy powder which consists of a composition gradient type Mo-Nb solid solution.
In the case of Mo oxide powder alone, the reduction reaction proceeds at about 1000 ° C., but in the case of Nb oxide powder alone, the reduction reaction does not proceed even if the temperature is increased to about 2000 ° C., When the mixed oxide powder is mixed, and the mixed oxide powder is reduced, the mechanism is not yet fully elucidated, but the temperature is 1350-1700 ° C., which is much lower than the reduction temperature of the Nb oxide alone. Further, at the same time, a diffusion / alloying reaction between Mo and Nb produced by the reduction can be caused.
ただ、水素雰囲気に維持された炉中へ混合酸化物粉末を装入し、上記還元・拡散・合金化処理の温度範囲にまで昇温するにあたり、加熱速度（昇温速度）があまりに速すぎると、混合酸化物粉末の表面側と内部側とに急激な温度勾配が生じ、還元反応・拡散反応・合金化反応の進行が部位によって異なったものとなり、その結果、未還元の酸化物粉末が残留する恐れがあり、一方、昇温速度が遅い場合には、還元・拡散・合金化処理に多大な時間を要し、生産効率が低下する。したがって、水素雰囲気炉への混合酸化物粉末の装入に当たっては、昇温速度が５〜５０℃／分になるように、炉温コントロールプログラムや１トレイあたりの混合酸化物粉末のチャージ量等を調整することが必要である。 However, if charging the mixed oxide powder into a furnace maintained in a hydrogen atmosphere and raising the temperature to the above temperature range of reduction / diffusion / alloying, the heating rate (heating rate) is too high. As a result, a rapid temperature gradient occurs on the surface side and the internal side of the mixed oxide powder, and the progress of the reduction reaction, diffusion reaction, and alloying reaction varies depending on the site. As a result, the unreduced oxide powder remains. On the other hand, when the rate of temperature increase is slow, a great deal of time is required for the reduction, diffusion, and alloying treatment, and the production efficiency decreases. Therefore, when charging the mixed oxide powder into the hydrogen atmosphere furnace, the furnace temperature control program, the charge amount of the mixed oxide powder per tray, etc. are set so that the heating rate is 5 to 50 ° C./min. It is necessary to adjust.
また、還元・拡散・合金化処理条件については、還元・拡散・合金化処理の温度が１３５０℃未満、あるいは、加熱保持時間が１時間未満の場合には、還元反応が十分に行われないばかりか、Ｍｏ及びＮｂの拡散・合金化反応も不十分となり、組成傾斜型のＭｏとＮｂの固溶体からなる合金粉末を形成することはできず、一方、還元処理温度が１７００℃を超えた場合、あるいは、加熱保持時間が６時間を越えた場合には、得られたＭｏ−Ｎｂ合金粉末の結晶粒組織の粗大化、Ｍｏ−Ｎｂ合金粉末の凝集が生じることによって、還元処理の効率の低下、粉末粒径の粗大化が生じる。また、Ｍｏ−Ｎｂ合金粉末が均一固溶体となってしまい、組成傾斜型の濃度分布構造を形成できなくなることもある。そこで、この発明では、還元・拡散・合金化処理の温度範囲を１３５０〜１７００℃、また、加熱保持時間を１〜６時間と定めた。なお、実用的な処理という観点からは、還元・拡散・合金化処理のより好ましい温度範囲は、１５００〜１６００℃であり、加熱保持時間は２〜３時間である。
上記還元・拡散・合金化処理により、０．５〜１０μｍレベルの微細な粉末粒径の、組成傾斜型のＭｏとＮｂの固溶体からなるＭｏ−Ｎｂ合金粉末を形成することができる。
Regarding the reduction / diffusion / alloying treatment conditions, when the temperature of the reduction / diffusion / alloying treatment is less than 1350 ° C. or the heating and holding time is less than 1 hour, the reduction reaction is not sufficiently performed. Or, the diffusion and alloying reaction of Mo and Nb becomes insufficient, and it is impossible to form an alloy powder composed of a solid solution of Mo and Nb having a composition gradient. On the other hand, when the reduction treatment temperature exceeds 1700 ° C., Alternatively, when the heating and holding time exceeds 6 hours, the grain structure of the obtained Mo—Nb alloy powder becomes coarse, and the aggregation of the Mo—Nb alloy powder occurs, thereby reducing the efficiency of the reduction treatment, The coarsening of the powder particle size occurs. In addition, the Mo—Nb alloy powder may become a uniform solid solution, and a composition gradient type concentration distribution structure may not be formed. Therefore, in this invention, the temperature range of the reduction / diffusion / alloying treatment is set to 1350 to 1700 ° C., and the heating and holding time is set to 1 to 6 hours. From the viewpoint of practical treatment, a more preferable temperature range of the reduction / diffusion / alloying treatment is 1500 to 1600 ° C., and the heating and holding time is 2 to 3 hours.
By the reduction / diffusion / alloying treatment, it is possible to form Mo—Nb alloy powder composed of a compositionally gradient Mo and Nb solid solution with a fine powder particle size of 0.5 to 10 μm.
前記（１）で既に述べたとおり、この発明では、Ｍｏ酸化物粉末としては、三酸化モリブデン（ＭｏＯ３）、二酸化モリブデン（ＭｏＯ２）等の各粉末を単独で又は混合して用いることができるが、Ｍｏ酸化物粉末として、二酸化モリブデン（ＭｏＯ２）を全く含有しないＭｏ酸化物、あるいは、二酸化モリブデン（ＭｏＯ２）含有量が少ないＭｏ酸化物の混合粉末を使用した場合には、このようなＭｏ酸化物粉末とＮｂ酸化物粉末との混合酸化物粉末を、還元・拡散・合金化処理を行う加熱保持温度（１３５０〜１７００℃）に昇温する過程で、混合酸化物粉末中のＭｏ成分が昇華をおこし、その結果、還元・拡散・合金化処理して得た合金粉末中のＭｏとＮｂの含有量比率が変化してしまい、目標とする成分組成割合のＭｏ−Ｎｂ合金粉末を得ることができなくなることがある。
そこで、このような場合には、還元・拡散・合金化処理に先立って、Ｍｏ成分をＭｏＯ２として安定化させ、Ｍｏ成分の昇華と、それに伴うＭｏとＮｂの含有量比率の変化を防止する安定化前処理を行うことが望ましい。
安定化前処理は、混合酸化物粉末を電気炉等に装入し、水素雰囲気中で所定時間加熱保持することによって、Ｍｏ酸化物粉末中のＭｏ成分をＭｏＯ２として安定化させ、還元・拡散・合金化処理の温度範囲にまで昇温される過程でＭｏ成分が昇華してしまうことを防ぎ、Ｍｏ−Ｎｂ合金粉末におけるＭｏとＮｂの含有量比率が変化することを防止する処理である。
As already described in the above (1), in the present invention, as the Mo oxide powder, each powder of molybdenum trioxide (MoO 3 ), molybdenum dioxide (MoO 2 ) and the like can be used alone or in combination. but as Mo oxide powder, Mo oxide contains no molybdenum dioxide (MoO 2), or, in the case of using a mixed powder of molybdenum dioxide (MoO 2) content is less Mo oxide, like this The Mo component in the mixed oxide powder in the process of raising the temperature of the mixed oxide powder of the Mo oxide powder and the Nb oxide powder to a heating and holding temperature (1350 to 1700 ° C.) for performing reduction, diffusion, and alloying treatment. As a result, the content ratio of Mo and Nb in the alloy powder obtained by reduction / diffusion / alloying treatment changes, and Mo—Nb having a target component composition ratio It may be impossible to obtain a gold powder.
Therefore, in such a case, prior to the reduction / diffusion / alloying treatment, the Mo component is stabilized as MoO 2 to prevent sublimation of the Mo component and the accompanying change in the content ratio of Mo and Nb. It is desirable to perform pre-stabilization.
Pre-stabilization is performed by charging the mixed oxide powder into an electric furnace or the like and heating and holding it in a hydrogen atmosphere for a predetermined time to stabilize the Mo component in the Mo oxide powder as MoO 2 for reduction / diffusion. -It is the process which prevents that Mo component sublimes in the process heated up to the temperature range of an alloying process, and prevents that the content ratio of Mo and Nb in Mo-Nb alloy powder changes.
安定化前処理：
使用するＭｏ酸化物粉末の純度、粒度分布、平均粒度あるいは使用する電気炉・トレイの容量等により、安定化前処理の具体的な条件は多少異なるが、いずれにしても、Ｍｏ酸化物粉末中のＭｏ成分をＭｏＯ２として安定化させのための前処理であって、例えば、純度９９．９９％以上、平均粒度０．９μｍであれば、チャージ量を３００〜５００ｇ／トレイ、水素ガス流量を２０〜６０Ｌ／ｍｉｎとした場合には、通常、加熱温度５００〜６５０℃（好ましくは、５４０〜６２０℃）で６０〜９０分保持することによって、Ｍｏ酸化物を二酸化モリブデン（ＭｏＯ２）として安定化することができる。なお、加熱温度が６５０℃を超えた場合には、Ｍｏ成分の昇華が生じる恐れがあり、また、５００℃未満では、Ｍｏ成分の安定化に長時間を要し、処理効率が低下することから、安定化前処理の加熱温度範囲は５００〜６５０℃とすることが望ましい。
Stabilization pretreatment:
Depending on the purity of the Mo oxide powder used, particle size distribution, average particle size or capacity of the electric furnace / tray used, the specific conditions for the stabilization pretreatment are slightly different. Pretreatment for stabilizing the Mo component as MoO 2 , for example, if the purity is 99.99% or more and the average particle size is 0.9 μm, the charge amount is 300 to 500 g / tray, and the hydrogen gas flow rate is In the case of 20 to 60 L / min, the Mo oxide is usually stabilized as molybdenum dioxide (MoO 2 ) by holding at a heating temperature of 500 to 650 ° C. (preferably 540 to 620 ° C.) for 60 to 90 minutes. Can be In addition, when heating temperature exceeds 650 degreeC, there exists a possibility that sublimation of Mo component may arise, and when it is less than 500 degreeC, since stabilization of Mo component requires a long time, processing efficiency falls. The heating temperature range for the stabilization pretreatment is preferably 500 to 650 ° C.
なお、上記安定化前処理は、Ｍｏ酸化物粉末中のＭｏ成分を二酸化モリブデン（ＭｏＯ２）として安定化させるための処理であるから、Ｍｏ酸化物粉末が二酸化モリブデン（ＭｏＯ２）粉末単独である場合には、本来このような安定化処理は必要とされない。
しかし、Ｍｏ酸化物粉末として、純度がそれほど高くない二酸化モリブデン（ＭｏＯ２）粉末を用いたような場合には、該酸化物粉末中のＭｏ成分は、厳密な意味で全てが二酸化モリブデン（ＭｏＯ２）として存在しているわけではなく、実際上は、三酸化モリブデン（ＭｏＯ３）等も微量存在していることから、Ｍｏ酸化物粉末の配合量と得られる合金粉末の成分組成の対応関係をより一致させるためには、上記安定化前処理を行ってＭｏ成分を安定化させ、Ｍｏ成分の含有比率の変動を防止しておくことは非常に有効である。
Incidentally, the stabilization pretreatment, since the Mo component of Mo oxide powder is a process for stabilizing a molybdenum dioxide (MoO 2), Mo oxide powder is molybdenum dioxide (MoO 2) powder alone In some cases, such a stabilization process is not originally required.
However, when molybdenum dioxide (MoO 2 ) powder having a low purity is used as the Mo oxide powder, the Mo component in the oxide powder is all molybdenum dioxide (MoO 2 in a strict sense). In fact, a small amount of molybdenum trioxide (MoO 3 ) etc. is present, so the correspondence between the amount of Mo oxide powder blended and the component composition of the resulting alloy powder In order to make them more consistent, it is very effective to stabilize the Mo component by performing the pre-stabilization process and to prevent fluctuations in the content ratio of the Mo component.
使用するＭｏ酸化物粉末に応じて、上記（２）の還元・拡散・合金化処理、あるいは、上記（２）、（３）の安定化前処理後の還元・拡散・合金化処理を行うことによって、不純物の混入が少なく純度が維持されたままで、粉末粒径も微細な０．５〜１０μｍという微細な粉末粒径の組成傾斜型Ｍｏ−Ｎｂ固溶体からなるＭｏ−Ｎｂ合金粉末が製造される。
そして、上記Ｍｏ−Ｎｂ合金粉末におけるＮｂ、Ｍｏの平均含有量は、目標とした合金成分組成割合と実質的に一致するばかりか、該合金粉末は、合金粉末表層部から合金粉末中心部へ向かってＮｂ含有量が次第に少なくなっている組成傾斜型の濃度分布構造を有し、しかも、均一微細な結晶粒組織を備えているものである。
Depending on the Mo oxide powder to be used, the reduction / diffusion / alloying treatment described in (2) above or the reduction / diffusion / alloying treatment after stabilization (2) and (3) is performed. Thus, a Mo—Nb alloy powder made of a composition gradient type Mo—Nb solid solution having a fine powder particle diameter of 0.5 to 10 μm and a fine powder particle diameter while maintaining a low purity with little contamination of impurities is manufactured. .
In addition, the average content of Nb and Mo in the Mo—Nb alloy powder substantially matches the target alloy composition ratio, and the alloy powder moves from the alloy powder surface layer to the center of the alloy powder. Therefore, it has a composition gradient type concentration distribution structure in which the Nb content is gradually decreasing, and also has a uniform fine crystal grain structure.
目標とするＭｏ−Ｎｂ系焼結体の成分組成に応じて、Ｍｏ酸化物粉末とＮｂ酸化物粉末の配合割合を調整し、組成傾斜型のＭｏ−Ｎｂ固溶体からなるＭｏ−Ｎｂ合金粉末を製造し、このＭｏ−Ｎｂ合金粉末を原料粉末として用いて、表５に示される従来から通常に行われている焼結条件で、所定組成のＭｏ−Ｎｂ系焼結体を作製したところ、例えば、表６に示されるように、抗折力、硬度、耐熱性、相対密度が非常に優れ、また、平均結晶粒径が非常に小さく（平均結晶粒径４０μｍ以下）、しかも、焼結体全体として均質な特性を備えたＭｏ−Ｎｂ系焼結体を得ることができた。 According to the component composition of the target Mo—Nb-based sintered body, the mixing ratio of the Mo oxide powder and the Nb oxide powder is adjusted, and a Mo—Nb alloy powder made of a composition gradient type Mo—Nb solid solution is produced. Then, using this Mo—Nb alloy powder as a raw material powder, a Mo—Nb-based sintered body having a predetermined composition was produced under the sintering conditions conventionally performed as shown in Table 5, for example, As shown in Table 6, the bending strength, hardness, heat resistance, and relative density are very excellent, the average crystal grain size is very small (average crystal grain size of 40 μm or less), and the sintered body as a whole A Mo—Nb-based sintered body having homogeneous characteristics could be obtained.
この発明の組成傾斜型のＭｏ−Ｎｂ固溶体からなるＭｏ−Ｎｂ合金粉末を焼結用原料粉末として用いれば、焼結性にすぐれ、均質かつ微細結晶粒組織の高密度の焼結体が得られるとともに、不純物の混入がなく高純度が維持されたまま、すぐれた抗折力、高温硬さ、耐熱性を有するＭｏ−Ｎｂ系焼結体を得ることができる。 If the Mo—Nb alloy powder comprising the composition gradient type Mo—Nb solid solution of the present invention is used as a raw material powder for sintering, a sintered body having excellent sinterability and a homogeneous and fine crystal grain structure can be obtained. At the same time, it is possible to obtain a Mo—Nb-based sintered body having excellent bending strength, high-temperature hardness, and heat resistance while maintaining high purity without mixing impurities.
表１に示す粒度と成分分析値のＭｏ酸化物粉末およびＮｂ酸化物粉末を使用し、表２に示すように、目標組成として、Ｎｂ平均含有量が１at％〜１０at％のＭｏ−Ｎｂ合金粉末が得られるように、Ｍｏ酸化物粉末とＮｂ酸化物粉末の種類と配合割合をかえた１０種類の混合粉末１〜１０を用意した。 Using Mo oxide powder and Nb oxide powder having particle sizes and component analysis values shown in Table 1, Mo-Nb alloy powder having an average Nb content of 1 at% to 10 at% as a target composition as shown in Table 2 10 types of mixed powders 1 to 10 in which the types and blending ratios of the Mo oxide powder and the Nb oxide powder were changed were prepared.
混合粉末１（５００ｇ）を電気炉内に装入し、表３に示すように、水素雰囲気中にて、１６００±２０℃で２時間加熱保持し、還元・拡散・合金化処理を行い、組成傾斜型のＭｏ−Ｎｂ固溶体からなるＭｏ−Ｎｂ合金粉末１を得た。そして、このＭｏ−Ｎｂ合金粉末１には酸化物は残存せず、組成傾斜型のＭｏ−Ｎｂ固溶体となっていることが確認された。
即ち、図１は、組成傾斜型のＭｏ−Ｎｂ合金粉末の断面についてのＮｂ濃度等高線を示す模式図であるが、Ｍｏ−Ｎｂ合金粉末１においても、この模式図に示されるように、粉末表面から粉末中心へ向かうにしたがってＮｂ成分の含有量が次第に減少する組成傾斜型の濃度分布構造となっていることが理解されている。
The mixed powder 1 (500 g) was charged into an electric furnace, and as shown in Table 3, the mixture was heated and held at 1600 ± 20 ° C. for 2 hours in a hydrogen atmosphere, followed by reduction, diffusion, and alloying treatment. A Mo—Nb alloy powder 1 made of an inclined Mo—Nb solid solution was obtained. It was confirmed that no oxide remained in the Mo—Nb alloy powder 1 and a compositionally gradient Mo—Nb solid solution was formed.
That is, FIG. 1 is a schematic diagram showing the Nb concentration contour line for the cross section of the composition-gradient type Mo—Nb alloy powder, but the Mo—Nb alloy powder 1 also shows the powder surface as shown in this schematic diagram. It is understood that the composition has a gradient-type concentration distribution structure in which the content of the Nb component gradually decreases from the powder center toward the powder center.
表２に示される混合粉末２〜１０について、表３に示される条件で還元・拡散・合金化処理を行って、Ｍｏ−Ｎｂ合金粉末２〜１０を得た。そして、このＭｏ−Ｎｂ合金粉末２〜１０についても、酸化物は存在せず、組成傾斜型のＭｏ−Ｎｂ固溶体となっていることを確認した。
なお、Ｍｏ酸化物として三酸化モリブデン（ＭｏＯ３）を使用した混合粉末６〜１０については、還元・拡散・合金化処理に先立って、表３に示される条件で安定化前処理を実施した。
The mixed powders 2 to 10 shown in Table 2 were subjected to reduction / diffusion / alloying treatment under the conditions shown in Table 3 to obtain Mo-Nb alloy powders 2 to 10. And about this Mo-Nb alloy powder 2-10, the oxide did not exist and it confirmed that it became a composition gradient type Mo-Nb solid solution.
Note that the mixed powder 6-10 using molybdenum trioxide (MoO 3) as a Mo oxide, prior to the reduction-diffusion-alloying treatment was performed stabilization pretreatment under the conditions shown in Table 3.
表４には、実施例１、実施例２で得られたＭｏ−Ｎｂ合金粉末１〜１０の、Ｍｏ平均含有量、Ｎｂ平均含有量、粉末表層部および粉末中心部における固溶Ｎｂ含有量とともに、粉末粒径、純度、他の成分（Ｏ，Ｆｅ，Ｎａ，Ｋ）の含有量を示したが、この発明のＭｏ−Ｎｂ合金粉末１〜１０は、組成傾斜型のＮｂ濃度分布構造を備え、９９．９９％以上の高純度を有し、合金粉末中のＭｏ、Ｎｂの平均含有量は、目標組成とほぼ一致した組成が得られ、Ｏ含有量及び不純物（Ｆｅ，Ｎａ，Ｋ）含有量が極めて少なく、粉末粒径も０．５〜１０μｍの範囲内のきわめて微細な組成傾斜型Ｍｏ−Ｎｂ合金粉末であることがわかる。 Table 4 shows Mo-Nb alloy powders 1 to 10 obtained in Example 1 and Example 2, together with Mo average content, Nb average content, powder surface layer portion, and solid solution Nb content in the powder center portion. The powder particle size, purity, and content of other components (O, Fe, Na, K) have been shown, but the Mo—Nb alloy powders 1 to 10 of the present invention have a composition-gradient Nb concentration distribution structure. The average content of Mo and Nb in the alloy powder is almost the same as the target composition, and the O content and impurities (Fe, Na, K) content It can be seen that this is a very fine composition-graded Mo—Nb alloy powder with a very small amount and a powder particle size in the range of 0.5 to 10 μm.
本発明でいう「粉末中心部」、「粉末表層部」とは以下のように定義される。
即ち、Ｍｏ−Ｎｂ合金粉末を熱硬化性樹脂に埋め込み、樹脂表面を研磨して、２〜４μｍ径の粉末粒子断面を得て、この粒子断面を光学顕微鏡で観察し、任意に３０個の測定粉末粒子を決定し、図２に示すように、各測定粉末粒子のＦｅｒｅｔ径（Ｆｅｒｅｔ径については、例えば、粉体工学研究会編「粉体粒度測定法」（１９６５年（株）養賢堂発行）２７〜２９頁、５３頁参照）の長径、短径を辺とする長方形を描き、該長方形の対角線の交点Ａを「粉末中心部」と定義し（図２中、「中心部」と表示）、また、Ａ点を通る任意の線上で、粉末粒子表面との交点を交点Ｂとし、交点Ａと交点Ｂの長さをＬとした場合、直線ＡＢ上で交点Ａから３Ｌ／４離れた位置（あるいは、直線ＡＢ上で交点ＢからＬ／４離れた位置）を「粉末表層部」と定義する（図２中、「表層部」と表示）。
なお、測定粉末粒子の決定に当り、交点Ａ（即ち、「粉末中心部」）が、粉末粒子断面外となってしまうような形状の粉末粒子については、測定対象から除外した。
また、この発明では、「粉末中心部」、「粉末表層部」のＭｏ含有量、Ｎｂ含有量を、エネルギー分散型Ｘ線分析装置（ＨＯＲＩＢＡ ＥＭＡＸ ＥＮＥＲＧＹ ＥＸ−２５０）を用い、粒子断面内の多点分析を行い求めた。電子顕微鏡設定は、加速電圧：１０ｋＶ、Ｗ．Ｄ＝１５ｍｍ、倍率：１０，０００倍。エネルギー分散型Ｘ線分析装置設定はプロセスタイム＝５、デッドタイム＝２０％、分析時間＝２００秒で測定した。
The “powder center part” and “powder surface layer part” in the present invention are defined as follows.
That is, Mo—Nb alloy powder is embedded in a thermosetting resin, the resin surface is polished, a powder particle cross section having a diameter of 2 to 4 μm is obtained, this particle cross section is observed with an optical microscope, and optionally 30 measurements are made. The powder particles are determined, and as shown in FIG. 2, the Feret diameter of each measured powder particle (for the Feret diameter, for example, “Powder Particle Size Measurement Method” edited by the Powder Engineering Research Group (1965, Yokendo Co., Ltd.). Issued) Draw a rectangle with sides of the major axis and minor axis (see pages 27-29 and 53), and define the intersection A of the diagonal of the rectangle as “powder center” (in FIG. In addition, on an arbitrary line passing through the point A, when the intersection point with the powder particle surface is the intersection point B and the length of the intersection point A and the intersection point B is L, it is 3L / 4 away from the intersection point A on the straight line AB. (Or a position that is L / 4 away from the intersection B on the straight line AB) Definitions (in FIG. 2, labeled "surface layer portion").
In determining the measurement powder particles, powder particles having such a shape that the intersection A (ie, “powder center”) is outside the cross section of the powder particles were excluded from the measurement target.
In the present invention, the Mo content and Nb content of the “powder center part” and “powder surface layer part” are determined using an energy dispersive X-ray analyzer (HORIBA EMAX ENERGY EX-250). Point analysis was performed. The electron microscope settings are: acceleration voltage: 10 kV, W.V. D = 15 mm, magnification: 10,000 times. The energy dispersive X-ray analyzer settings were measured at process time = 5, dead time = 20%, and analysis time = 200 seconds.
次に、本発明の上記Ｍｏ−Ｎｂ合金粉末１〜１０を原料粉末として用い、表５に示される焼結条件の焼結法により、Ｍｏ−Ｎｂ系焼結体（本発明焼結体１〜１０という）を作製した。
比較のために、酸化モリブデンを水素還元して得られた平均粒径６μｍのＭｏ粉末と、電解法により得た平均粒径１００μｍのＮｂ粉末を、所定組成（Ｎｂが１原子％、１０原子％）となるように配合し、これをそのまま焼結用の原料粉末として用い、表５に示される焼結条件で焼結し、Ｍｏ−Ｎｂ系焼結体（比較焼結体１、２という）を作製した。
Next, the Mo—Nb alloy powders 1 to 10 of the present invention were used as raw material powders, and a Mo—Nb-based sintered body (the present invention sintered body 1 to 1) was obtained by a sintering method under the sintering conditions shown in Table 5. 10).
For comparison, Mo powder having an average particle diameter of 6 μm obtained by hydrogen reduction of molybdenum oxide and Nb powder having an average particle diameter of 100 μm obtained by an electrolysis method have a predetermined composition (Nb is 1 atom%, 10 atom%). And used as raw powder for sintering, and sintered under the sintering conditions shown in Table 5, Mo-Nb-based sintered bodies (referred to as comparative sintered bodies 1 and 2). Was made.
上記本発明焼結体１〜１０と比較焼結体１、２の諸特性を表６に示す。
なお、各焼結体の特性は、まず、得られた焼結体をダイヤモンド砥石で研削し、その後、ダイヤモンド琢磨を行い鏡面とし、これをダイヤモンドカッターにて切断し、８ｍｍ×４ｍｍ×２４ｍｍの試験片を３０本作製して、以下のように測定した。
「坑折力（ＭＰａ）」：支点間距離２０ｍｍで、ＪＩＳ Ｚ２２０３に規定された抗折試験方法に基づいて測定した３０本の試験片の測定値の平均値。
「硬さ（Ｈｖ）」：常温で測定した３０本の試験片のビッカース硬さの平均値。
「耐熱性（％）」：１０本の試験片から１辺１．６ｍｍの立方体の１０サンプルを切出し、ＴＧ−ＤＴＡで、空気流量１５０ｍｌ／ｍｉｎ、昇温速度１０℃／ｍｉｎ、６００℃保持時間１時間で熱重量分析を行い、ＴＧ曲線より重量増加率（％）を測定した１０本のサンプルの平均値。
「相対密度（％）」：アルキメデス（水中天秤）法で測定した上記各３０本の試験片の測定値の平均値。
「平均結晶粒径（μｍ）」：光学顕微鏡（倍率×1,000）の観察により、ランダム５０結晶粒について測定した結晶粒径の平均値。
Table 6 shows various characteristics of the sintered bodies 1 to 10 of the present invention and the comparative sintered bodies 1 and 2.
The characteristics of each sintered body are as follows. First, the obtained sintered body is ground with a diamond grindstone, then diamond-polished to give a mirror surface, which is cut with a diamond cutter, and an 8 mm × 4 mm × 24 mm test. Thirty pieces were prepared and measured as follows.
“Mole folding force (MPa)”: an average value of measured values of 30 test pieces measured based on a bending test method defined in JIS Z2203 at a distance between supporting points of 20 mm.
“Hardness (Hv)”: average value of Vickers hardness of 30 test pieces measured at room temperature.
“Heat resistance (%)”: Ten samples of 1.6 mm cubes were cut out from 10 test pieces, and air flow rate 150 ml / min, heating rate 10 ° C./min, 600 ° C. holding time with TG-DTA. An average value of 10 samples obtained by performing thermogravimetric analysis in 1 hour and measuring a weight increase rate (%) from a TG curve.
“Relative density (%)”: The average value of the measured values of each of the 30 test pieces measured by the Archimedes (underwater balance) method.
“Average crystal grain size (μm)”: average value of crystal grain sizes measured for 50 random crystal grains by observation with an optical microscope (magnification × 1,000).
表６に示される諸特性の対比から、この発明の組成傾斜型Ｍｏ−Ｎｂ合金粉末１〜１０を用いて作製した本発明焼結体１〜１０は、比較焼結体１、２と比較して、焼結性にすぐれ、相対密度は高く、平均結晶粒径は小さく、非常に緻密かつ微細な結晶粒組織になっているとともに、坑折力、硬度、耐熱性にすぐれたものとなっている。
以上のとおり、この発明の組成傾斜型のＭｏ−Ｎｂ合金粉末は、これを原料粉末として用いて焼結体を製造した場合に、得られたＭｏ−Ｎｂ系焼結体は、高純度、微細結晶粒組織、均質であり、すぐれた耐熱性、機械的特性を備えたものとなる。
From the comparison of the characteristics shown in Table 6, the sintered bodies 1 to 10 of the present invention produced using the composition gradient type Mo—Nb alloy powders 1 to 10 of the present invention are compared with the comparative sintered bodies 1 and 2. It has excellent sinterability, high relative density, small average grain size, very fine and fine grain structure, and excellent fold strength, hardness and heat resistance. Yes.
As described above, the composition-gradient type Mo—Nb alloy powder of the present invention has a high purity and fineness when the obtained Mo—Nb-based sintered body is manufactured using this as a raw material powder. The grain structure is homogeneous and has excellent heat resistance and mechanical properties.
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