Stability of NiCrAlY coating/titanium alloy system under pure thermal exposure

In this paper, NiCrAlY coating was deposited on TC4 titanium alloy using arc ion plating, and the stability of NiCrAlY coating/TC4 substrate system under pure thermal exposure was analyzed in a wide temperature range. During the thermal exposure, beta -> gamma'-> gamma phase transformation takes place in the NiCrAlY coating. The NiCrAlY coating phases totally decompose above the allotropic transformation temperature of TC4. The allotropic transformation of alpha-Ti to beta-Ti of the substrate significantly influences the stability of NiCrAlY coating/TC4 substrate system. NiCrAlY coating elements are mainly consumed by interfacial reactions below the allotropic transformation temperature of TC4. Above the allotropic transformation temperature of TC4, NiCrAlY coating elements are mainly consumed by element dissolution in beta-Ti. The NiCrAlY coating totally degrades for the dissolution of coating elements in the substrate to form thick beta-Ti stabilized layer.