Oxidation Behavior of Thermal Barrier Coatings with a TiAl3 Bond Coat on gamma-TiAl Alloy

The thermal barrier coatings investigated in this paper included a TiAl3 bond coat and a yttria partially stabilized zirconia (YSZ) layer. The TiAl3 bond coat was prepared by deposition of aluminum by cold spray, followed by a heat-treatment. The YSZ layer was prepared by air plasma spray. The isothermal and cyclic oxidation tests were conducted at 900 degrees C for 1000 h and 500 cycles to test the oxidation resistance of the thermal barrier coatings. The microstructure and composition of the gamma-TiAl alloy with and without the thermal barrier coatings after oxidation were investigated. The results showed that a dense TGO layer about 5 mu m had grown between the YSZ layer and the TiAl3 bond coat. The TGO had good adhesion to both the YSZ layer and the bond coat even after the TiAl3 bond coat entirely degraded into the TiAl2 phase, which decreased the inward oxygen diffusion. Thus, the thermal barrier coatings improved the oxidation resistance of gamma-TiAl alloy effectively.