Aluminum Pack Cementation on Mo–Si–B Alloys

Abstract

Following aluminum pack cementation on Mo-Si-B alloys, the oxidation response has been examined in the range 700-1400°C in 0.20× 105 Pa of oxygen under isothermal and cyclic conditions. The initial coating is mainly composed of Mo3 Al8, which reacts with the oxygen to produce a surface layer of alumina. The alumina slows the rate of oxidation considerably. The coating also reacts with the alloy substrate to develop an intermediate layer mainly composed of Mo3 (Al,Si) A15 phase. The kinetics of the oxidation and intermediate A15 phase formation reactions have been evaluated in order to model the alloy substrate recession and the overall coating lifetime.