Microstructure evolution and interdiffusion behaviors of (Ni,Pt)Al coating with and without Re-diffusion barrier on IC21 substrate at 1100°C

Abstract

The degradation of high temperature oxidation resistance and mechanical properties caused by the high temperature interdiffusion between the coating and the single crystal intermetallic superalloy substrate has become a heavily researched topic within aeronautical materials research in recent years. In order to study the microstructural evolution and interdiffusion behaviors of the coating and superalloy, the (Ni, Pt)Al coating with and without Re-diffusion barrier (Re-DB) was prepared on the Ni3Al based superalloy (Grade: IC21). The thermal exposure tests were carried out on the specimens in air at 1100 °C for 200 h. The results revealed that the Al content in the coating gradually reduced during thermal exposure, and both coatings underwent phase transformation from β-(Ni, Pt)Al to Ni3Al. The coating with Re-DB had a lower phase transformation ratio. Moreover, the coating with Re-DB had smaller and fewer TCP phases precipitated in the inter-diffusion zone (IDZ) and secondary reaction zone (SRZ), showing that the Re-DB contributed to a lower extent of interdiffusion. Based on the actual measured composition-distance data, the interdiffusion coefficients between the (Ni, Pt)Al coating and the IC21 substrate with and without Re-DB were determined using HitDIC software, which verified that Re-DB impeded the diffusion of Re, Mo and Cr from substrate to the coating.