JP2008280597A - Oxidation resistant iridium alloy and method for producing the same - Google Patents
Oxidation resistant iridium alloy and method for producing the same Download PDFInfo
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- 229910000575 Ir alloy Inorganic materials 0.000 title claims abstract description 92
- 230000003647 oxidation Effects 0.000 title claims abstract description 78
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 78
- 238000004519 manufacturing process Methods 0.000 title claims description 20
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 75
- 239000000956 alloy Substances 0.000 claims abstract description 75
- 229910052741 iridium Inorganic materials 0.000 claims abstract description 53
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims abstract description 53
- 239000000463 material Substances 0.000 claims abstract description 31
- 239000000843 powder Substances 0.000 claims abstract description 22
- 239000012190 activator Substances 0.000 claims abstract description 9
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- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 6
- 239000012298 atmosphere Substances 0.000 claims description 6
- 229910052804 chromium Inorganic materials 0.000 claims description 6
- 239000011651 chromium Substances 0.000 claims description 6
- 229910017052 cobalt Inorganic materials 0.000 claims description 6
- 239000010941 cobalt Substances 0.000 claims description 6
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 6
- 239000003112 inhibitor Substances 0.000 claims description 6
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- 229910052703 rhodium Inorganic materials 0.000 description 19
- 239000010948 rhodium Substances 0.000 description 19
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 19
- 238000012360 testing method Methods 0.000 description 15
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 14
- 238000002844 melting Methods 0.000 description 11
- 230000008018 melting Effects 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 7
- 239000000654 additive Substances 0.000 description 5
- 230000000996 additive effect Effects 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
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- 239000007789 gas Substances 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 4
- 229910002056 binary alloy Inorganic materials 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 4
- 229910052721 tungsten Inorganic materials 0.000 description 4
- 239000010937 tungsten Substances 0.000 description 4
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 3
- 230000009471 action Effects 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 229910000457 iridium oxide Inorganic materials 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
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- 239000003870 refractory metal Substances 0.000 description 3
- 229910052726 zirconium Inorganic materials 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 2
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 235000019270 ammonium chloride Nutrition 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229910000428 cobalt oxide Inorganic materials 0.000 description 2
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000004453 electron probe microanalysis Methods 0.000 description 2
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- 229910052715 tantalum Inorganic materials 0.000 description 2
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- DDFHBQSCUXNBSA-UHFFFAOYSA-N 5-(5-carboxythiophen-2-yl)thiophene-2-carboxylic acid Chemical compound S1C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)S1 DDFHBQSCUXNBSA-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
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- 229910052735 hafnium Inorganic materials 0.000 description 1
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 238000005240 physical vapour deposition Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 229910052702 rhenium Inorganic materials 0.000 description 1
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
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- 239000006104 solid solution Substances 0.000 description 1
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- 239000010935 stainless steel Substances 0.000 description 1
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- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
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- Other Surface Treatments For Metallic Materials (AREA)
Abstract
Description
本発明は、耐熱性イリジウム合金に関する。 The present invention relates to a heat resistant iridium alloy.
白金族元素であるイリジウムは、タングステン、レニウムに次いで融点が高く、これら非貴金属よりも酸化しにくく、酸化による消耗も少ないことから、高温強度、化学的安定性、耐酸化性とも優れた高温材料として、高温用るつぼ、耐熱器具、ガスタービン、スパークプラグ、高温用センサ、ジェットエンジンなどの広い分野で用いられている。
一方でイリジウムは、高温における耐酸化性が、他の高融点金属よりは優れるものの、十分でないことは周知の問題であり、これまでに合金設計による改善が多数試みられてきた。このようなイリジウム合金の先行例は多数あるが、比較的新しい文献を引用し、この分野の従来技術を説明する。
Iridium, a platinum group element, has the second highest melting point after tungsten and rhenium, is less oxidized than these non-noble metals, and is less consumed by oxidation. Therefore, it is a high-temperature material with excellent high-temperature strength, chemical stability, and oxidation resistance. As high temperature crucibles, heat-resistant appliances, gas turbines, spark plugs, high temperature sensors, jet engines, etc.
On the other hand, although iridium is superior in oxidation resistance at high temperatures to other refractory metals, it is a well-known problem that it is not sufficient, and so far, many improvements have been attempted by alloy design. Although there are many prior examples of such iridium alloys, relatively new literature is cited and the prior art in this field is described.
特許文献１には、ロジウム又は白金を0.5〜40％を含有するイリジウム二元合金製るつぼが開示されている。同文献によれば、これらの二元合金は、純イリジウム製と比較して外観上の変化や酸化が起こらないという。
特許文献２には、高温機器、ガスタービン、センサ、高融点材料溶解用るつぼ、耐熱器具など高温強度・耐酸化性が要求される耐熱材料に関するものとして、白金、パラジウム、ロジウム、ニオブ、タンタル、ハフニウム、チタン、ジルコニウム、イットリウム、ランタン、モリブデンのうちの１種以上を固溶範囲内で含有するイリジウム合金が開示されている。同文献によれば、合金表面に安定被膜が形成されることにより耐酸化性が向上するとされている。
特許文献３には、前記２文献及び他の公知文献を踏まえた上で、タングステン、ジルコニウム又はロジウムを含有するイリジウム合金とこの合金製電極及びその電極を含むスパークプラグが開示されている。同文献に開示された実施例の耐酸化性は、5％白金含有イリジウム二元合金よりすぐれ、かつ、10％ロジウム含有イリジウム二元合金には劣るレベルとされている。
特許文献４には、イリジウム、ロジウム、タングステン及びジルコニウムからなる合金を電極とするスパークプラグが開示されている。同文献においては、イリジウム合金の酸化消耗低減には、高価なロジウムの多量添加が不可欠であることが明らかにされている。
以上概説したように、従来のイリジウム合金の開発は、耐酸化性向上に着目してなされており、高価な白金族元素の多量添加による合金設計が提案されている。 As outlined above, the development of conventional iridium alloys has been focused on improving oxidation resistance, and an alloy design by adding a large amount of expensive platinum group elements has been proposed.
ところで、イリジウム合金の耐酸化性が不十分なのは、前記各文献にも開示される通り、約1000℃以上で生成するイリジウム酸化物の蒸気圧が高く、この温度以上では昇華又は揮発してしまうことによる。これはイリジウム固有の性質であるから、耐酸化性を向上させるためには、他の元素を添加して、イリジウム含有量を減じることが有効である、との技術思想に基づき、合金設計において種々の工夫がなされてきた。
しかし、合金中のイリジウムを減じれば融点が低下し、高温強度が低下するなどの問題があり、反対にイリジウムが多ければ酸化消耗の問題が解決できない、というジレンマを克服できていない。
あえて耐酸化性を向上させるには、イリジウム含有量を低下させるほかなく、そのために耐酸化性が極めて高いが、極めて高価なロジウムや白金の多量添加が必須となって、大変高価な合金とならざるを得ず、経済的合理性を解決できない問題も依然としてある。こうした高価な合金は、耐酸化性に優れるとしても、その用途はおのずと限られてしまう。
By the way, the reason why the oxidation resistance of the iridium alloy is insufficient is that the vapor pressure of the iridium oxide generated at about 1000 ° C. or higher is high, and it is sublimated or volatilized at this temperature or higher, as disclosed in the respective documents. by. Since this is an inherent property of iridium, it is effective to add various elements to reduce the iridium content in order to improve oxidation resistance. Has been devised.
However, if the iridium in the alloy is reduced, the melting point is lowered and the high temperature strength is lowered. On the other hand, the dilemma that the problem of oxidative consumption cannot be solved if there is a large amount of iridium has not been overcome.
In order to improve the oxidation resistance, the iridium content must be reduced. Therefore, the oxidation resistance is extremely high, but a very large amount of rhodium or platinum must be added. There are still problems that cannot be solved economically. Even if such an expensive alloy is excellent in oxidation resistance, its use is naturally limited.
本発明の目的は、以上説明したように従来のイリジウム合金の宿命的問題点に鑑み、耐酸化性を飛躍的に向上させ、より長期にわたって安定的に使用可能な低コストのイリジウム合金、その応用製品及びその製造方法を提供することである。 As described above, the object of the present invention is to provide a low-cost iridium alloy that can dramatically improve oxidation resistance and can be used stably over a long period of time, in view of the fate of conventional iridium alloys. It is to provide a product and a manufacturing method thereof.
上記目的を達成するために、本願の第１の発明は、耐熱性イリジウム合金において、イリジウム又はイリジウム合金からなる基材と、その基材表面の一部又は全部に基材成分と不動態酸化被膜形成元素とを含んでなる合金層を備え、その合金層中のイリジウムが基材界面から表面にかけて連続的に組成傾斜することを特徴とする耐酸化性イリジウム合金である。
ここで、イリジウム合金とは、イリジウムが主成分である耐熱金属を意味し、溶融法により製造されるものや焼結法により製造されるものなどがある。
不動態酸化被膜形成元素とは、要するに高温の酸素存在下において合金表面に保護性の緻密な酸化被膜を形成する元素であればよい。
又、前記合金層中のイリジウムが基材界面から表面にかけて連続的に組成傾斜するということは、基材と合金層との界面において基材側イリジウム濃度と合金層側イリジウム濃度が等しく、かつ、合金層の表面では、イリジウム濃度が基材中のイリジウム濃度より小さいことを意味し、例えば、合金層断面のイリジウム濃度が、界面から表面にかけて、単調減少しなくてもよい。
In order to achieve the above object, a first invention of the present application is a heat-resistant iridium alloy, a substrate made of iridium or an iridium alloy, and a substrate component and a passive oxide film on a part or all of the surface of the substrate. An oxidation-resistant iridium alloy comprising an alloy layer containing a forming element, wherein iridium in the alloy layer is continuously gradient in composition from the substrate interface to the surface.
Here, the iridium alloy means a refractory metal containing iridium as a main component, and includes those manufactured by a melting method and those manufactured by a sintering method.
In short, the passive oxide film forming element may be an element that forms a protective dense oxide film on the alloy surface in the presence of high-temperature oxygen.
Further, the iridium in the alloy layer is continuously compositionally inclined from the base material interface to the surface, the base material side iridium concentration and the alloy layer side iridium concentration are equal at the interface between the base material and the alloy layer, and On the surface of the alloy layer, it means that the iridium concentration is smaller than the iridium concentration in the substrate. For example, the iridium concentration in the cross section of the alloy layer does not have to monotonously decrease from the interface to the surface.
第２の発明は、前記耐熱性イリジウム合金において、前記不動態酸化被膜形成元素が、クロム、コバルト及び珪素からなる群より選択される１又は２以上の元素であることを特徴とする耐酸化性イリジウム合金である。
クロム、コバルト又は珪素のうちの１種以上を含んでなる合金層は、酸化熱処理又は使用環境において、これら元素の酸化物被膜を形成し、基材中のイリジウムを酸化消耗から保護する。
According to a second aspect of the present invention, in the heat resistant iridium alloy, the passive oxide film forming element is one or more elements selected from the group consisting of chromium, cobalt, and silicon. Iridium alloy.
An alloy layer containing one or more of chromium, cobalt, and silicon forms an oxide film of these elements in an oxidation heat treatment or use environment, and protects iridium in the substrate from oxidation consumption.
第３の発明は、前記耐熱性イリジウム合金において、第２の発明に記載した合金層に、さらにアルミニウムを含むことを特徴とする耐酸化性イリジウム合金である。
前記合金層にさらにアルミニウムを含んでなる合金層は、前記不動態酸化被膜形成元素とアルミニウムと複合酸化被膜又はアルミナ被膜を形成し、基材中のイリジウムを酸化消耗から保護する。
A third invention is an oxidation-resistant iridium alloy characterized in that in the heat-resistant iridium alloy, the alloy layer described in the second invention further contains aluminum.
The alloy layer further comprising aluminum in the alloy layer forms a composite oxide film or an alumina film with the passive oxide film forming element and aluminum, and protects iridium in the substrate from oxidation consumption.
第４の発明は、前記耐熱性イリジウム合金において、第１〜第３の発明に記載した合金層の厚さが、1〜50μmであることを特徴とする耐酸化性イリジウム合金である。
合金層厚さをこの範囲とすると好適で、合金層厚さが1μm以上であれば、耐熱性を向上させるに十分な量の保護性酸化被膜が形成され、又、50μm以下であれば、合金層と基材との線膨張差や弾性係数の差に起因するクラックや合金層のはく離を効果的に防止できる。
前記耐酸化性イリジウム合金を用いることにより、本発明の目的を達成する耐熱部材又は電極を提供することができる。
A fourth invention is an oxidation-resistant iridium alloy characterized in that, in the heat-resistant iridium alloy, the thickness of the alloy layer described in the first to third inventions is 1 to 50 μm.
It is preferable that the alloy layer thickness is within this range. If the alloy layer thickness is 1 μm or more, a sufficient amount of a protective oxide film is formed to improve heat resistance. Cracks and peeling of the alloy layer due to differences in linear expansion and elastic modulus between the layer and the substrate can be effectively prevented.
By using the oxidation-resistant iridium alloy, a heat-resistant member or electrode that achieves the object of the present invention can be provided.
第５の発明は、上記第１〜第４の発明の何れかに記載の耐酸化性イリジウム合金からなる耐熱部材である。
ここで、耐熱部材とは、高温で使用され、高い耐酸化性を要求される部材を意味し、具体的には、例えば、ガラス溶解用るつぼ、器具、ガスタービン部品などがある。
5th invention is a heat-resistant member which consists of an oxidation-resistant iridium alloy in any one of the said 1st-4th invention.
Here, the heat-resistant member means a member that is used at a high temperature and requires high oxidation resistance, and specifically includes, for example, a glass melting crucible, an instrument, and a gas turbine component.
第６の発明は、上記第１〜第４の発明の何れかに記載の耐酸化性イリジウム合金からなる電極である。
ここで、電極とは、高温で使用され、高い耐酸化性を要求される電極を意味し、具体的には、例えば自動車用ガスセンサの電極、航空機エンジン、自動車エンジンの点火プラグ用電極などがある。
A sixth invention is an electrode made of the oxidation-resistant iridium alloy according to any one of the first to fourth inventions.
Here, the electrode means an electrode that is used at a high temperature and requires high oxidation resistance, and specifically includes, for example, an electrode for an automobile gas sensor, an aircraft engine, an electrode for an ignition plug of an automobile engine, and the like. .
第７の発明は、不動態酸化被膜形成元素と活性化剤と焼結防止剤を混合してなる浸透剤粉末と、イリジウム又はイリジウム合金からなる基材とを接触して配置し、600℃以上の不活性雰囲気又は真空中で10分以上加熱保持して拡散処理した後、冷却することを特徴とする耐酸化性イリジウム合金の製造方法である。 7th invention arrange | positions the penetrant powder which mixes a passive oxide film formation element, an activator, and a sintering inhibitor, and the base material which consists of iridium or an iridium alloy, contacts 600 degreeC or more. A method for producing an oxidation-resistant iridium alloy, wherein the diffusion treatment is performed by heating and holding in an inert atmosphere or vacuum for 10 minutes or more, and then cooling.
第８の発明は、上記第７の発明に記載の耐酸化性耐熱合金製造方法において、前記接触して配置する方法が、浸透剤粉末のペースト状組成物をイリジウム又はイリジウム合金に塗布することを特徴とする耐酸化性イリジウム合金の製造方法である。 According to an eighth aspect of the present invention, in the method for producing an oxidation-resistant heat-resistant alloy according to the seventh aspect, the method of placing in contact applies a paste-like composition of a penetrant powder to iridium or an iridium alloy. A feature is a method for producing an oxidation-resistant iridium alloy.
第９の発明は、上記第７又は８の発明に記載の耐酸化性耐熱合金製造方法において、前記浸透剤粉末が不動態酸化被膜形成元素10〜50％と活性化剤3〜20％と焼結防止剤30〜87％を混合してなることを特徴とする耐酸化性イリジウム合金の製造方法である。 According to a ninth invention, in the method for producing an oxidation-resistant heat-resistant alloy as set forth in the seventh or eighth invention, the penetrant powder is sintered with 10-50% of a passive oxide film-forming element, 3-20% of an activator. It is a method for producing an oxidation-resistant iridium alloy characterized by mixing 30 to 87% of an anti-caking agent.
第１０の発明は、上記第７又は８の発明に記載の耐酸化性耐熱合金製造方法において、前記拡散処理の温度が900〜1300℃、かつ、時間が30分〜10時間であることを特徴とする耐酸化性イリジウム合金の製造方法である。 A tenth invention is characterized in that, in the oxidation-resistant heat-resistant alloy manufacturing method according to the seventh or eighth invention, the temperature of the diffusion treatment is 900 to 1300 ° C. and the time is 30 minutes to 10 hours. This is a method for producing an oxidation-resistant iridium alloy.
本発明によれば、従来のイリジウム合金の宿命的問題点を解消し、耐酸化性を飛躍的に向上させ、より長期にわたって安定的に使用可能な低コストのイリジウム合金、その応用製品及びその製造方法を提供することができる。 The present invention eliminates the fatal problems of conventional iridium alloys, dramatically improves oxidation resistance, and can be used stably over a long period of time, its application products, and its production A method can be provided.
本発明の実施の形態について、以下詳細に述べる。 Embodiments of the present invention will be described in detail below.
既に述べたとおり、従来のイリジウム合金の宿命的課題は、耐酸化性の改善であり、多数の従来技術に開示される通り、多年に渡り合金設計による改良が重ねられてきた。 As already mentioned, the fatal problem of conventional iridium alloys is the improvement of oxidation resistance, and as disclosed in many prior arts, improvements by alloy design have been repeated for many years.
イリジウム合金の耐酸化性が劣る原因は、主成分であるイリジウムが、約1000℃以上の高温酸素存在下で揮発性酸化イリジウムを生成することにある。そのため、合金設計の方針は、同環境でも酸化しがたい添加元素の探索であり、多くの例で高融点金属が選択されている。なかでも、比較的融点が高く、酸化しにくい白金族元素の１種であるロジウムを添加することによる耐酸化性の改善が注目されてきた。 The cause of the poor oxidation resistance of the iridium alloy is that iridium as a main component generates volatile iridium oxide in the presence of high-temperature oxygen of about 1000 ° C. or higher. Therefore, the policy of alloy design is to search for additive elements that are difficult to oxidize even in the same environment, and in many cases, a refractory metal is selected. Among them, attention has been focused on improving oxidation resistance by adding rhodium, which is a kind of platinum group element that has a relatively high melting point and is difficult to oxidize.
しかしながら、ロジウムを添加元素とする場合には、合金の融点低下及び価格高騰の問題が無視できない。ロジウムの融点は1960℃で、主成分イリジウムの８割程度に過ぎず、耐酸化性向上のための多量添加は、合金の融点を下げ、高温強度を低下させてしまう。又、ロジウム地金価格は、2007年3月現在で１ｇあたり24,000円を超え、近年稀に見る暴騰が続いており、ロジウムを多量に使用することが困難となっている。 However, when rhodium is used as an additive element, the problems of the melting point decrease and the price increase of the alloy cannot be ignored. The melting point of rhodium is 1960 ° C., which is only about 80% of the main component iridium. Addition of a large amount for improving the oxidation resistance lowers the melting point of the alloy and lowers the high temperature strength. In addition, the rhodium price is over 24,000 yen per gram as of March 2007, and it has been rarely soaring in recent years, making it difficult to use a large amount of rhodium.
このように添加元素として有望視されるロジウムの問題はもとより、他の添加元素にしても、多量に添加すれば、加工性を著しく悪化させる問題、添加元素自体の酸化消耗の問題が顕在化し、十分な耐酸化性を発現するには、合金設計による改良には、自ずと限界がある。 Thus, not only the problem of rhodium which is considered promising as an additive element, but also other additive elements, if added in a large amount, the problem of remarkably degrading workability, the problem of oxidative consumption of the additive element itself, In order to develop sufficient oxidation resistance, there is a limit to improvement by alloy design.
本発明は、従来のイリジウム合金の問題に鑑みて鋭意研究の末、完成されたもので、次に述べる耐酸化性に優れたイリジウム合金を得ることができる。 The present invention has been completed after intensive studies in view of the problems of conventional iridium alloys, and an iridium alloy having excellent oxidation resistance described below can be obtained.
本発明は、耐熱性イリジウム合金において、イリジウム又はイリジウム合金からなる基材と、その基材表面の一部又は全部に基材成分と不動態酸化被膜形成元素と含んでなる合金層を備え、その合金層中のイリジウムが基材界面から表面にかけて連続的に組成傾斜することを特徴とする耐酸化性イリジウム合金である。 The present invention comprises a base material made of iridium or an iridium alloy in a heat-resistant iridium alloy, and an alloy layer containing a base material component and a passive oxide film forming element on part or all of the surface of the base material, It is an oxidation-resistant iridium alloy characterized in that iridium in the alloy layer has a composition gradient continuously from the substrate interface to the surface.
本発明のイリジウム合金は、その表面に前記合金層を備えるために、高温酸素存在下に不動態酸化被膜が形成される。この不動態酸化被膜は、雰囲気中の酸素の、イリジウム合金内部への拡散を遮断するから、基材のイリジウム自体は酸化することなく、したがって、揮発性酸化イリジウムを生成することもない。又、前記合金層中のイリジウムが基材界面から表面にかけて連続的に組成傾斜するために、合金層と基材との密着に優れる。 Since the iridium alloy of the present invention has the alloy layer on its surface, a passive oxide film is formed in the presence of high-temperature oxygen. This passive oxide film blocks the diffusion of oxygen in the atmosphere into the iridium alloy, so that the iridium of the substrate itself does not oxidize and therefore does not generate volatile iridium oxide. Moreover, since the iridium in the alloy layer continuously inclines from the substrate interface to the surface, the alloy layer and the substrate are excellent in adhesion.
本発明のイリジウム合金の特徴的な構成は、こうした作用によってイリジウムの酸化消耗を抑制し、合金層の耐久性を向上させ、高い耐酸化性を発現するのである。 The characteristic configuration of the iridium alloy of the present invention suppresses oxidative consumption of iridium by such an action, improves the durability of the alloy layer, and exhibits high oxidation resistance.
基材のイリジウム合金は、イリジウムを主成分とする合金であれば、任意の組成でよく、合金層は後工程で付与可能であるから、基材の製法も任意としてよい。一般的な板材や線材の他、微小なチップ様電極、形状が複雑なタービンエンジン部品などにも用いることができる。 The iridium alloy of the base material may be of any composition as long as it is an alloy containing iridium as a main component, and the alloy layer can be applied in a subsequent step, and therefore the manufacturing method of the base material may be arbitrary. In addition to general plate materials and wires, it can also be used for minute chip-like electrodes, turbine engine parts with complicated shapes, and the like.
本発明の第１の効果である高い耐酸化性を得るには、イリジウム又はイリジウム合金の表面に前記合金層を形成すれば足り、高価な白金族元素、例えばロジウムを多量に添加する必然性はまったくない。したがって、低価格でありながら、高い信頼性が得られ、世界的に進行するといわれる資源インフレのさなかにありながら、さまざまな利用分野において経済合理性の高い機器・部品を提供することができる。 In order to obtain the high oxidation resistance which is the first effect of the present invention, it is sufficient to form the alloy layer on the surface of iridium or an iridium alloy, and it is absolutely necessary to add a large amount of an expensive platinum group element such as rhodium. Absent. Accordingly, it is possible to provide equipment and parts with high economic rationality in various fields of use in spite of resource inflation, which is said to be highly reliable and to be advanced worldwide, at a low price.
さらに、本発明のイリジウム合金は、表面が酸化被膜で覆われ、基材金属が露出することがないため、強度低下が抑制できる。例えば、純イリジウムの場合には、高温酸化によって、表面がポーラスになり、又、ロジウムなどとの合金の場合には、表面上の粒界からの酸化消耗が顕著である。このような表面の変化は、予亀裂が多数存在するに等しく、したがって、比較的延展性に乏しいイリジウム合金にあっては、消耗前に比べ顕著な強度低下を示し、単なる酸化消耗に次いで、寿命低下の原因となるのである。本発明のイリジウム合金は、酸化被膜で覆われることにより、表面の多孔質化や粒界の予亀裂発生を効果的に防ぐことができ、強度低下が抑制されるのである。
これと同様の作用により、電気部品として用いた場合には、エロージョン等による表面劣化を防止し、断線を防ぐことができるため、電気部品の信頼性が向上する。
又、同様の作用により、表面に酸化被膜が形成されるために、イリジウム又はイリジウム合金に含まれる他の金属と使用環境中に含まれる腐食性物質との接触を遮断でき、直接反応によって生じる腐食を未然に防ぐ効果も期待できる。
Furthermore, since the surface of the iridium alloy of the present invention is covered with an oxide film and the base metal is not exposed, a decrease in strength can be suppressed. For example, in the case of pure iridium, the surface becomes porous due to high-temperature oxidation, and in the case of an alloy with rhodium or the like, oxidation consumption from the grain boundary on the surface is remarkable. Such a surface change is equivalent to the presence of many precracks, and therefore, in an iridium alloy with relatively poor extensibility, it shows a significant decrease in strength compared to that before consumption, and after mere oxidation consumption, It will cause a drop. By covering the iridium alloy of the present invention with an oxide film, it is possible to effectively prevent the surface from becoming porous and the occurrence of precracking at grain boundaries, and the strength reduction is suppressed.
Due to the same action, when used as an electrical component, the surface deterioration due to erosion or the like can be prevented and disconnection can be prevented, so that the reliability of the electrical component is improved.
In addition, since an oxide film is formed on the surface due to the same action, the contact between the iridium or other metal contained in the iridium alloy and the corrosive substance contained in the use environment can be blocked, and the corrosion caused by the direct reaction. It can be expected to prevent this.
さらに好適には、前記合金層に含まれる不動態酸化被膜形成元素が、クロム、コバルト及び珪素の内のいずれか１種又は２種以上の組合せが望ましい。又、これら不動態酸化被膜形成元素に加え、アルミニウムを含む合金層を備えたイリジウム合金も好適である。イリジウム、又は、クロム、コバルト若しくは珪素を含まないイリジウム合金と、アルミニウムとからなる合金層は、大変脆く亀裂を生じやすいため、本発明の目的である耐久性向上においては不向きである。 More preferably, the passive oxide film forming element contained in the alloy layer is desirably one or a combination of two or more of chromium, cobalt and silicon. An iridium alloy provided with an alloy layer containing aluminum in addition to these passive oxide film forming elements is also suitable. An alloy layer made of iridium or an iridium alloy not containing chromium, cobalt, or silicon and aluminum is very brittle and easily cracked, so that it is not suitable for improving durability, which is an object of the present invention.
さらに好適には、前記合金層の厚さを1〜50μmとするとよい。合金層厚さが1μm以上であれば、耐熱性を向上させるに十分な量の保護性酸化被膜が形成され、又、50μm以下であれば、合金層と基材との線膨張差や弾性係数の差に起因するクラックや合金層のはく離を効果的に防止できる。 More preferably, the thickness of the alloy layer is 1 to 50 μm. If the alloy layer thickness is 1 μm or more, a sufficient amount of protective oxide film is formed to improve heat resistance, and if it is 50 μm or less, the difference in linear expansion and elastic modulus between the alloy layer and the base material are formed. It is possible to effectively prevent cracks and peeling of the alloy layer due to the difference between the two.
以上説明した本発明のイリジウム合金は、その特徴を活かして耐熱部材として用いるのが好適である。特に、表面の一部又は全部が前記合金層を備えるガラス溶解用るつぼや耐熱器具、ガスタービンの耐熱部材に適する。これら耐熱部材は、耐酸化性、耐食性に優れ、強度低下が生じないため信頼性及び耐久性が高く、さらに従来のイリジウム合金製耐熱部材より低コストで提供されるため経済合理性に優れるなど、利点が多い。 The iridium alloy of the present invention described above is preferably used as a heat-resistant member taking advantage of its characteristics. In particular, a part or all of the surface is suitable for a glass melting crucible, a heat-resistant appliance, and a heat-resistant member of a gas turbine provided with the alloy layer. These heat-resistant members are superior in oxidation resistance and corrosion resistance, have high reliability and durability because strength does not decrease, and are economically rational because they are provided at a lower cost than conventional iridium alloy heat-resistant members. There are many advantages.
又、本発明のイリジウム合金は、その特徴を活かして電極として用いるのが好適である。特に、表面の一部又は全部が前記合金層を備える電極として、高温酸素存在下又は腐食環境下で用いられるセンサ用電極や航空機・自動車のエンジンに用いる点火プラグ電極に適する。これら電極は、耐酸化性、耐食性に優れ、強度低下が生じないため組込まれる電気機器の信頼性及び耐久性を向上させ、さらに従来のイリジウム合金製電極より低コストで提供されるため経済合理性に優れるなど、利点が多い。 The iridium alloy of the present invention is preferably used as an electrode taking advantage of its characteristics. In particular, as an electrode having a part or all of the surface provided with the alloy layer, it is suitable for a sensor electrode used in the presence of high-temperature oxygen or in a corrosive environment, and a spark plug electrode used for an aircraft / automobile engine. These electrodes are excellent in oxidation resistance and corrosion resistance, and do not cause a decrease in strength, improving the reliability and durability of the incorporated electrical equipment, and being provided at a lower cost than conventional iridium alloy electrodes, the economic rationality There are many advantages, such as being excellent.
次いで、前記イリジウム合金の製造方法について述べる。 Next, a method for producing the iridium alloy will be described.
前記合金層は、不動態酸化被膜形成元素と活性化剤と焼結防止剤とからなる浸透剤粉末から、不動態酸化被膜形成元素が基材表面へ拡散することによって形成される。
不動態酸化被膜形成元素は、単一元素の粉末でもよいし、２種以上の元素を選択する場合には、それぞれの単一元素粉末を混合して用いるか、又は、合金粉末などの形態で用いるのがよい。
活性化剤は、600℃以上の不活性雰囲気又は真空中の加熱によって不動態酸化被膜形成元素と反応し、このハロゲン化物を生成するものであればよく、例えば、塩化アンモニウム、フッ化アンモニウムなどが適する。不活性ガス又は真空中とするのは、前記合金層が形成される前に浸透剤又は基材の酸化を防ぐためである。
焼結防止剤は、拡散処理の過程で浸透剤粉末が固く焼結し、過度の収縮により亀裂を発生し、製造上の作業性を損なうことがないようにする目的で配合する。好適な例は、アルミナ粉末で、この他、例えば、ジルコニア系、シリカ系、マグネシア系などの耐火物原料であってもよい。
The alloy layer is formed by diffusing the passive oxide film forming element from the penetrant powder composed of the passive oxide film forming element, the activator, and the sintering inhibitor to the substrate surface.
The passive oxide film forming element may be a single element powder. When two or more kinds of elements are selected, each single element powder is mixed or used in the form of an alloy powder or the like. It is good to use.
Any activator may be used as long as it reacts with a passive oxide film forming element by heating in an inert atmosphere at 600 ° C. or higher or in a vacuum to generate this halide. For example, ammonium chloride, ammonium fluoride, etc. Suitable. The purpose of the inert gas or vacuum is to prevent oxidation of the penetrant or the substrate before the alloy layer is formed.
The sintering inhibitor is blended for the purpose of preventing the penetrant powder from being hardly sintered during the diffusion treatment, causing cracks due to excessive shrinkage, and impairing the workability in production. A suitable example is alumina powder, and in addition, for example, a refractory material such as zirconia, silica, or magnesia may be used.
前記合金層は、前述のように生成するハロゲン化物から不動態酸化被膜形成元素が基材表面に拡散して形成されるので、浸透剤粉末と基材とは、近接して配置されることが望ましく、より好ましくは、接触して配置する。より具体的な手段として、基材を浸透剤粉末に埋め込む方法、又は浸透剤粉末のペースト状組成物を基材表面に塗布する方法がある。 The alloy layer is formed by diffusing the passive oxide film forming element from the halide generated as described above to the surface of the base material, so that the penetrant powder and the base material may be arranged close to each other. Desirably, more preferably, they are placed in contact. As a more specific means, there is a method of embedding the base material in the penetrant powder or a method of applying a paste-like composition of the penetrant powder to the surface of the base material.
不動態酸化被膜形成元素を含む前記合金層の形成手段は、この他に溶融めっき・溶融塩めっきによる方法、スパッタなど物理蒸着による方法など、公知の薄膜形成手段を取り得る。本発明の方法によれば、これらと比べ簡便で、低コストかつ低環境負荷で製造できるなど利点が多い。 As the means for forming the alloy layer containing the passive oxide film forming element, known thin film forming means such as a method using hot dip plating / molten salt plating or a method using physical vapor deposition such as sputtering can be used. According to the method of the present invention, there are many advantages such as simplicity, low cost and low environmental load.
浸透剤粉末の好適な配合割合は、不動態酸化被膜形成元素10〜50％と活性化剤3〜20％と焼結防止剤30〜87％の範囲である。この範囲を好適とする理由は、不動態酸化被膜形成元素が10％以上、又は活性化剤が3％以上であれば、本発明の目的に十分な前記合金層を形成することができ、焼結防止剤が30％以上であれば、浸透剤粉末が固く焼結するなどして作業性を損なう恐れがないからである。 A suitable blending ratio of the penetrant powder is in the range of 10 to 50% of the passive oxide film forming element, 3 to 20% of the activator, and 30 to 87% of the sintering inhibitor. The reason why this range is suitable is that if the passive oxide film forming element is 10% or more, or the activator is 3% or more, the alloy layer sufficient for the purpose of the present invention can be formed, This is because, if the anti-caking agent is 30% or more, there is no risk of impairing workability due to the sintering of the penetrant powder.
拡散処理は、上述の通り、基材への拡散反応が生じる熱処理条件とすればよく、900〜1300℃、かつ、30分〜10時間の範囲であれば、より好適な合金層とすることができる。 As described above, the diffusion treatment may be a heat treatment condition that causes a diffusion reaction to the base material, and if it is in the range of 900 to 1300 ° C. and 30 minutes to 10 hours, a more suitable alloy layer may be formed. it can.
以下、本発明を実施例により説明する。 Hereinafter, the present invention will be described with reference to examples.
（従来例）
まず、表１に示す従来例について説明する。
従来例１は、純イリジウムである。
従来例２は、5％白金添加イリジウム合金である。
従来例３は、10％ロジウム添加イリジウム合金である。
従来例４は、30％ロジウム添加イリジウム合金である。
(Conventional example)
First, a conventional example shown in Table 1 will be described.
Conventional Example 1 is pure iridium.
Conventional Example 2 is a 5% platinum-added iridium alloy.
Conventional Example 3 is a 10% rhodium-added iridium alloy.
Conventional Example 4 is a 30% rhodium-added iridium alloy.
先に引用した先行技術文献によると、純イリジウムに白金族元素を適宜添加することにより耐酸化性が向上するとされており、中でもロジウムの添加はその効果が高いことが開示されている。そこで、耐酸化性が特に優れるとされるこれら合金を用いて、1200℃大気中で20時間加熱する耐熱試験を実施した。
試験片は、表１に示す合金組成となるよう原料を配合し、アーク溶解で合金化し、熱間加工を経て、φ0.6mmの線を作製し、約20mmの長さに切断して作製した。
表１の酸化消耗性は、前記耐熱試験における質量減少率と定義し、従来例３の10％ロジウム添加イリジウム合金の質量減少率を10として規格化して表示している。
According to the prior art documents cited above, it is said that the oxidation resistance is improved by appropriately adding a platinum group element to pure iridium, and it is disclosed that the addition of rhodium is particularly effective. Therefore, a heat resistance test was carried out using these alloys, which are considered to be particularly excellent in oxidation resistance, by heating in the atmosphere at 1200 ° C. for 20 hours.
The test piece was prepared by blending the raw materials so as to have the alloy composition shown in Table 1, alloying by arc melting, hot working, producing a φ0.6 mm wire, and cutting to a length of about 20 mm. .
The oxidation consumability in Table 1 is defined as the mass reduction rate in the heat resistance test, and is normalized and displayed with the mass reduction rate of the 10% rhodium-added iridium alloy of Conventional Example 3 as 10.
結果が示す通り、白金族元素との合金化による耐酸化性の効果は顕著で、ロジウムが多量に含まれる従来例３の合金の酸化消耗性は、純イリジウム比5％にまで、従来例４では、同1.5％にまで低減した。 As the results show, the effect of oxidation resistance by alloying with the platinum group element is remarkable, and the oxidation consumability of the alloy of Conventional Example 3 containing a large amount of rhodium is up to 5% of pure iridium ratio. Then, it was reduced to 1.5%.
（実施例）
次に、表２に示す本発明の実施例を説明する。
(Example)
Next, examples of the present invention shown in Table 2 will be described.
実施例に用いた基材は、前記従来例を踏まえ、5％白金添加イリジウム合金（実施例１〜６）、純イリジウム（実施例７〜９）及び10％ロジウム添加イリジウム合金（実施例１０〜１９）とし、その表面を有機溶剤で脱脂、洗浄した。 The base materials used in the examples are 5% platinum-added iridium alloys (Examples 1 to 6), pure iridium (Examples 7 to 9) and 10% rhodium-added iridium alloys (Examples 10 to 10) based on the above-described conventional examples. 19), and the surface was degreased and washed with an organic solvent.
浸透剤配合は、実施例ごとに表２に示す不動態酸化被膜形成元素粉末30％、塩化アンモニウム10％、アルミナ粉末60％とし、これらを乳鉢で５分間混合し、さらにＶ型混合器を用いて、60rpmで30分間混合した。
なお、不動態酸化被膜形成元素は、前記の通り30％配合したが、複数の元素からなる実施例１６〜１９は、それぞれの元素の粉末を15％ずつ配合し、合計で30％とした。
The penetrant formulation is 30% passive oxide film forming element powder, 10% ammonium chloride, 60% alumina powder shown in Table 2 for each example, and these are mixed for 5 minutes in a mortar and further using a V-type mixer. And mixed at 60 rpm for 30 minutes.
In addition, although the passive oxide film forming element was blended 30% as described above, in Examples 16 to 19 consisting of a plurality of elements, 15% of each element powder was blended to make 30% in total.
拡散処理は、基材と浸透剤粉末とをステンレス製容器に充填し、容器ごと管状炉内に設置して、毎分100mLのアルゴン気流下で室温から1050℃まで昇温し、1時間経過後に室温まで炉冷した。ただし、表２の実施例において、基材及び不動態酸化被膜形成元素が同じもので、合金層厚さが厚いものについては、前記同様の雰囲気及び温度で加熱し、３時間経過後に室温まで炉冷した。 Diffusion treatment is performed by filling the base material and penetrant powder into a stainless steel container, placing the container in a tubular furnace, raising the temperature from room temperature to 1050 ° C. under an argon stream of 100 mL per minute, and after 1 hour The furnace was cooled to room temperature. However, in the examples in Table 2, the same base material and passive oxide film forming element and the thick alloy layer were heated in the same atmosphere and temperature as above, and the furnace was heated to room temperature after 3 hours. Chilled.
このようにして処理した試験片を試料包埋樹脂に埋め込み、鏡面まで研磨した後、断面をＥＰＭＡにて分析したところ、いずれの実施例でも不動態酸化被膜形成元素を含む合金層が確認できた。その合金層の厚さは、表２の通りであり、合金層中のイリジウム濃度は、界面から表面にかけて連続的に変化し、界面では基材と等しく、表面では基材より減少していた。実施例３の表面付近の断面構造を図１に、元素分布を図２に示す。 The test piece thus treated was embedded in a sample embedding resin, polished to a mirror surface, and then analyzed by EPMA. As a result, an alloy layer containing a passive oxide film forming element could be confirmed in any example. . The thickness of the alloy layer is as shown in Table 2. The iridium concentration in the alloy layer continuously changed from the interface to the surface, and was equal to the substrate at the interface and decreased from the substrate at the surface. FIG. 1 shows the cross-sectional structure near the surface of Example 3, and FIG. 2 shows the element distribution.
前記浸透剤をイソプロパノールに溶いてペースト状組成物とし、このペースト状組成物を基材に表面に塗布後乾燥させて、拡散処理を施した場合にも、実施例と同様の合金層が形成された。 Even when the penetrant is dissolved in isopropanol to form a paste-like composition, and this paste-like composition is applied to the surface of the substrate and then dried and subjected to a diffusion treatment, an alloy layer similar to that of the example is formed. It was.
これら実施例の耐酸化性は、従来例と同様の耐熱試験を実施し、合金層を形成していない基材の酸化消耗性と比較した。すなわち、実施例１〜６については、表１従来例２の5％白金添加イリジウム合金を、実施例７〜９は、表１従来例１の純イリジウムを、実施例１０〜１９は、従来例３の10％ロジウム添加イリジウム合金を基準として、その比率（酸化消耗比）を表２及び図３に示した。酸化消耗比は、値が小さいほど基材より耐酸化性が向上したことを表す。
表２及び図３から明らかなように、いずれの実施例のイリジウム合金も、基材そのものより格段に酸化消耗が低下した。中でも、コバルト及び珪素の効果は顕著であった。
The oxidation resistance of these examples was compared with the oxidation wear resistance of the base material in which the alloy layer was not formed by performing the same heat resistance test as in the conventional example. That is, for Examples 1 to 6, the 5% platinum-added iridium alloy of Table 1 Conventional Example 2 was used, Examples 7 to 9 were pure iridium of Table 1 Conventional Example 1, and Examples 10 to 19 were conventional examples. The ratio (oxidation consumption ratio) of No. 3 with 10% rhodium added iridium alloy is shown in Table 2 and FIG. The oxidation consumption ratio indicates that the smaller the value, the better the oxidation resistance than the base material.
As is apparent from Table 2 and FIG. 3, the iridium alloy of any of the examples was significantly reduced in oxidation consumption compared to the base material itself. Among them, the effect of cobalt and silicon was remarkable.
耐熱試験後のＥＰＭＡによる断面観察では、試験片表面が不動態酸化被膜形成元素の酸化物被膜で覆われており、この被膜下の基材は、実施例１、実施例２、実施例７、実施例１０、実施例１１及び実施例１６においては、ごく僅かな消耗が確認されたが、その他の実施例では、なんら消耗の痕跡を見出せなかった。 In cross-sectional observation by EPMA after the heat test, the surface of the test piece was covered with an oxide film of a passive oxide film forming element, and the substrates under this film were Example 1, Example 2, Example 7, In Example 10, Example 11 and Example 16, very slight consumption was confirmed, but in other examples, no trace of consumption was found.
図４及び図５に従来例３のイリジウム合金及び実施例３のイリジウム合金の耐熱試験後の断面をそれぞれ示す。従来例のイリジウム合金は、表１に見た通り、純イリジウムより耐酸化性に優れるものの、十分とはいえず、図４のようにイリジウムが酸化、消耗していた。特に粒界は激しく消耗し、脱イリジウムにより気孔やロジウムリッチ相が形成されていた。耐熱試験後の試験片を用いて、引張試験を試みたところ、破断荷重は、元のイリジウム合金を大幅に下回るものであった。 4 and 5 show cross sections of the iridium alloy of Conventional Example 3 and the iridium alloy of Example 3 after a heat resistance test, respectively. As shown in Table 1, the conventional iridium alloy was superior in oxidation resistance to pure iridium, but was not sufficient, and iridium was oxidized and consumed as shown in FIG. In particular, the grain boundaries were exhausted violently, and pores and rhodium-rich phases were formed by deiridium. When the tensile test was tried using the test piece after the heat test, the breaking load was significantly lower than the original iridium alloy.
一方、実施例３のイリジウム合金は、図５のように表面にコバルト酸化物被膜が形成され、その直下には、内部酸化して形成された酸化コバルトが観察された。従来例のような、イリジウムの消耗の痕跡は、まったく認められなかった。耐熱試験後の引張試験では、極端な破断荷重の低下は認められなかった。 On the other hand, in the iridium alloy of Example 3, a cobalt oxide film was formed on the surface as shown in FIG. 5, and cobalt oxide formed by internal oxidation was observed immediately below. As in the conventional example, no trace of iridium consumption was observed. In the tensile test after the heat test, no extreme decrease in breaking load was observed.
（比較例）
次に、表３に示す比較例を説明する。
(Comparative example)
Next, a comparative example shown in Table 3 will be described.
比較例１は、不動態酸化被膜形成元素をアルミニウム単独として拡散処理したものである。合金層は形成されるが、はく離してしまった。 Comparative Example 1 is obtained by subjecting the passive oxide film forming element to diffusion treatment with aluminum alone. An alloy layer was formed, but it was peeled off.
比較例２は、不動態酸化被膜形成元素をクロムとし、拡散処理を900℃、5分間としたもので、表３に示す通り合金層厚さは1μm未満であった。耐熱試験結果は、表３及び図３に示す通り、基材と同程度となり、合金層厚さが不足したために耐酸化性は向上しなかった。
実施例に記載の処理条件でなくても、900℃〜1300℃、かつ、30分〜10時間の範囲で拡散処理したところ、厚さが1〜50μmまでの健全な合金層が形成され、耐酸化性が向上した。
In Comparative Example 2, the passive oxide film forming element was chromium, and the diffusion treatment was 900 ° C. for 5 minutes. As shown in Table 3, the alloy layer thickness was less than 1 μm. As shown in Table 3 and FIG. 3, the results of the heat resistance test were the same as those of the base material, and the oxidation resistance was not improved because the alloy layer thickness was insufficient.
Even if the processing conditions are not described in the examples, when a diffusion treatment is performed in the range of 900 ° C. to 1300 ° C. and 30 minutes to 10 hours, a sound alloy layer with a thickness of 1 to 50 μm is formed, and the acid resistance Improved chemical properties.
比較例３は、基材を厚さ0.5mmのタングステン板としたものである。
比較例４は、基材を厚さ0.5mmのタンタル板としたものである。
これらの比較例は、耐熱試験後には、すべての金属部分が消失し、耐酸化性の向上は認められなかった。
Comparative Example 3 is a tungsten plate having a thickness of 0.5 mm.
In Comparative Example 4, the base material is a tantalum plate having a thickness of 0.5 mm.
In these comparative examples, after the heat resistance test, all metal parts disappeared and no improvement in oxidation resistance was observed.
以上説明の通り、本発明によれば、耐酸化性が、従来のイリジウム合金より飛躍的に優れるイリジウム合金を提供することができる。 As described above, according to the present invention, it is possible to provide an iridium alloy whose oxidation resistance is remarkably superior to that of a conventional iridium alloy.
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