An effective and low-cost method to prepare Re-doped aluminide coating on a Ni-based single crystal superalloy

Abstract

In order to prepare Re doped aluminide coating, an effective and low-cost method of electroplating Ni-Re layer and subsequent low temperature high activity pack cementation method was used. Re-doped Ni2Al3 coating was consisted of an outer Ni2Al3 layer with dispersed Re-rich precipitates, a middle Ni2Al3 layer with dispersed W-rich precipitates and a bottom layer of interdiffusion zone (IDZ). Interestingly, Re existed in the outer coating in form of fine Re-rich precipitates because of low solid solubility of Re in Ni2Al3. [Al] was produced and absorbed on the surface of Ni-Re layer, and the activity of Al was far higher than that of Ni during pack cementation at 800 °C. Thus, Re-doped Ni2Al3 coating was mainly formed by virtually singular inward diffusion of [Al] through the Ni2Al3 layer.