Coating-related deterioration mechanism of creep performance at a thermal exposed single crystal Ni-base superalloy

The Pt-modified aluminide coating is applied on the superalloy in advanced turbine aero-engines due to its excellent oxidation resistance. However, the interdiffusion between the coatings and substrates would occur under high service temperatures. It could deteriorate the microstructure and mechanical performance of the substrates. The present study investigates the creep properties of coated samples with different holding times at 1100°C (0–500 h). The bare alloys are exposed and tested at the same temperature with various stresses to build the Larson-Miller curves. Owing to the topological inversion and the precipitation of TCP phases, the creep life of the bare alloys reduces with the increased holding time. The coated samples show an elevated creep rate compared with bare alloys. Only a slight degradation in the creep life of the coated samples is observed within 100 h thermal exposure, but a further deterioration happens with the extended exposure time. The load-bearing capacity of the coats shows a dependence on the exposure time, and it can be attributed to the microstructure and elemental distribution changes in the coating during thermal exposure.