ガスタービン動翼コーティング材の長時間熱時効による組織変化

抄録

The degradation of coatings and substrates would be a great influence on the integrity of gas turbine blades for electric power generation. This paper describes the effect of thermal aging at 870°C and 920°C for 8000h in air on the microstructure and chemical composition in aluminized CoCrAlY coatings and directionally-solidified Ni-base superalloy substrates of advanced gas turbine blades. The unaged and thermally aged coatings consisted of four layers with different microstructure and chemical composition. Thermal aging led to a little oxidation, nitridation and decrease in the Al content in near-surface regions. In the adjacent region, coarse Cr rich precipitates formed during the thermal aging. During the thermal aging, Ni diffused extensively from the substrates into near-surface regions. The interdiffusion of Ni/Co resulted in the formation of Al/Ni rich intermetallic phases in various coating regions. The thermal aging formed the coating/substrate interdiffusion zone, which comprised Al/Ni rich elongated precipitates.