Effect of Pt on interdiffusion and mechanical properties of theγandγ′ phases in the Ni–Pt–Al system

Abstract

The effect of Pt on the growth kinetics of the γ′-[Ni(Pt)]3Al ordered intermetallic phase and the γ-Ni(Pt, Al) solid solution diffusion rates of the species, hardness and elastic modulus was examined by employing the diffusion couple experimental technique. Experiments were conducted by using the β-Ni(Pt)Al phase and Ni(Pt) alloy couples, each of which had a fixed amount of Pt (5, 10 and 15 at. %) in both the end members so that the Pt content is more or less constant throughout the interdiffusion zone. The results suggest that the growth kinetics of both phases and the average effective interdiffusion coefficients of Ni and Al increase with the increase in Pt content. Nanoindentation studies across the compositional gradients show that the mechanical properties of the intermetallic phase in the superalloy are relatively insensitive to the presence of Pt but are more sensitive to the Ni/Al ratio. In contrast, the marked variation in the hardness of the γ phase were noted, increasing markedly with Al concentration in a given couple and also increasing with increasing Pt content. Possible causes for the observed variations are discussed.