금속간화합물 TiAl 의 고온산화거동 및 기계적성질에 미치는 Yttrium 첨가 Ll2 ( Al , Cr ) 3Ti 코팅의 효과

Abstract

The oxidation behaviors and the mechanical properties of TiAl alloys coated with the Al-21Ti-23Cr and the Al-21Ti-23Cr-0.lY films were investigated. A small addition of yttrium to the coating material was, effective in the improvement of the oxidation resistance of the Ti-48Al. From the scratch test, specimen coated with the Al-21Ti-23Cr-0.1Y film had better adhesion between the Al₂O₃ scale and the coating layer than one coated with the Al-21Ti-23Cr film. And AFM study showed that the Al₂O₃,surface of the Al-21Ti-23Cr-0.1Y coating is more smooth than one of the Al-21Tr-23Cr coating after isothermal oxidation; Thus, it is suggested that this excellent oxidation resistance is attributable to the excellent adhesion between the Al₂O₃ scale and the Al-21Ti-23Cr-0.1Y film and the smooth Al₂O₃ surface of the Al-21Ti-23Cr-0.1Y coating. From the tensile test, it was found that AI-21Ti-23Cr-0.1Y coating enables the TiAl to maintain more effectively its tensile properties in an oxidizing environment than the Al-21Ti-23Cr coating. Moreover, the specimen coated with the Al-21Ti-23Cr-0.1Y film showed lower creep rate and longer time to rupture than the specimen without coating, under the constant stress of 200 ㎫ at 1123 K in air. Therefore. it could be assumed that the Al-21Ti-23Cr-0.1Y alloy was prospective as an oxidation-resistant coating material for TiAl alloys.