Diffusion behaviors of Rh, Ta, W, Re, Os and Ir in ternary L12-Ni3Al alloys

Diffusion behaviors of Rh, Ta, W, Re, Os, and Ir in ternary γ′-Ni3Al alloys were investigated at 1373-1473 K using solid-solid single-phase diffusion couples together with the recently developed HitDIC software. The temperature- and concentration-dependent ternary interdiffusivities in Ni3Al-X (X = Rh, Ta, W, Re, Os, and Ir) were determined from the experimental concentration profiles, and also fully validated. After that, a thorough comparison among the interdiffusivities in γ′ Ni-22.9 at% Al-0.1 at% X (X = Ti, V, Cr, Fe, Co, Ni, Nb, Mo, Ru, Rh, Ta, W, Re, Os, Ir and Pt) alloys at 1373-1473 K was then conducted, from which it can be concluded that W exhibits the lowest interdiffusivities in γ′-Ni3Al alloy, followed by Ta. It is finally suggested that addition of W and Ta in γ′ phase can retard the coarsening of γ′ phase and stabilize the microstructure of the nickel-based single crystal superalloys in terms of the diffusion coefficient.