Characterisation and Oxidation Behaviour of Plasma Surface Alloyed on Γ-Tial Alloy

The double glow plasma surface alloying process (DGP) is an emerging alternative technology for fabricating thermal barrier coating. In spite of its merits such as gradient metallurgical bond and thickness controllability, DGP method is less well known than electron beam-physical vapour deposition and plasma spraying technique for the bond coatings. This paper serves as a preliminary study into the use of this technology for preparation of gradient MCrAlY bond coating on titanium alloys, with a focus on the oxidation performance at 750, 850 and 950 degrees C. In this study, a gradient MCrAlY bond coating was successfully synthesised on gamma-TiAl alloy by DGP. The as-deposited coating was composed of gamma '-Ni3Al, gamma-TiAl, AlCr2 and sigma-NiCoCr. The maximum load that the as-deposited coating could bear was 60 N. The MCrAlY coating exhibited much better oxidation resistance than the bare TiAl alloy due to the formation of multilayer oxide scales. The research opportunities for further optimisation of this type of MCrAlY coatings are also discussed.