1988 Fiscal Year Final Research Report Summary
Surface Modification of Heat Resistant Alloys with Rare-Earth Chromium Composite Oxides Coatings
| Project/Area Number |
62550508
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属材料(含表面処理・腐食防食)
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| Research Institution | Hokkaido University |
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Principal Investigator |
HIDETAKA KONNO Fac. of Engineering, Hokkaido University, 工学部, 助手 (50002316)
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| Co-Investigator(Kenkyū-buntansha) |
HIDEAKI TAKAHASHI Fac. of Engineering, Hokkaido University, 工学部, 助手 (70002201)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Oxide coatings / Rare-earth chromium oxides / Electrodeposition / High temperature oxidation / Stainless steel / Perovskite structre oxides / 活性元素 |
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| Research Abstract |
The incorporation of reactive elements such as rare-earths, Zr, Ti, etc. to heat resistant alloys improves the oxidation resistance markedly. In the present work, methods to form the composite oxide films of reactive elements and chromium on heat resistant alloys were developed employing electrodeposition. The results are summarized as follows:
(1) By cathodic polarization, thin gel like films of reactive elements and chromium were formed on metals from acidic chromate solutions containing reactive elements. The film was converted to the composite oxide by heating. The Zr-Cr and Ti-Cr composite oxide films thus formed provided good oxidation resistance to Fe-Cr alloys and SUS 430 stainless steel.
(2) The LaOH(CrO_4)_xH_2O films were obtained with good reproducibility by cathodic polarization of metals in lightly acidic La(III)-Cr(VI) solutions. The compound was found to decompose to perovskite structure LaCrO_3 at lower temperatures and with shorter pyrolysis times than La(III) and Cr(III) compounds precursors.
(3) The LaCrO_3 is resistant to oxidation or corrosion at elevated tempeatures, and the film on SUS 304 and SUS 430 stainless steels extended the lifetime to breakaway more than ten times.
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