Preparation and oxidation resistance of a crack-free Al diffusion coating on Ti22Al26Nb |
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| Authors: | K. Zhang Q.M. Wang F.H. Wang |
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| Affiliation: | a State Key Lab for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, PR China
b Chemistry and Life College, Shengyang Normal University, 253 Huanghe Street, Shenyang 110034, PR China |
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| Abstract: | A crack-free Al diffusion coating has been developed to improve the oxidation resistance of Ti22Al26Nb. It was produced by a two-step method; an Al film was deposited on the substrate alloy by arc ion plating followed by a diffusion process conducted at 873 K in pure Ar to form the Al diffusion coating. The two-step method lowers the temperature required to form the diffusion coating, which dramatically decreases the thermal stress developed in the coating and results in it being crack-free. The oxidation resistance of the non-coated Ti22Al26Nb alloy in isothermal and cyclic tests in air at 1073 K was poor, but the coated specimens possessed excellent oxidation resistance because a protective α-Al2O3 scale formed. The life of the Al diffusion coating greatly depends upon the rapid initial formation of a protective Al2O3 scale and interdiffusion between coating and substrate. Once the stable Al2O3 scale has formed and the composition changes from (Ti, Nb)Al3 into (Ti, Nb)Al2, the coating has a long life. |
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| Keywords: | A. Alloy A. Metal coatings A. Titanium C. Effects of strain C. Oxidation |
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