Effects of adding Ni and Co on microstructure and gamma prime phase stability in Ni superalloy Inconel 738 with 1 wt.-% Al

Abstract

Abstract The effects of adding nickel and cobalt to Inconel 738 along with adding 1 wt.-% of aluminum were investigated in this study. The alloys, with various amounts of nickel and cobalt, were prepared using a vacuum arc melting process. The alloys were heat treated using a standard heat treatment procedure which consisted of solution treatment at 1448 K for 14.4 ks and precipitation aging at 1118 K for 86.4 ks. Increased nickel content was shown to enhance the stability of gamma prime particles and the gamma matrix as well as assist the formation of gamma prime particles. In the case of the addition of cobalt, the coarsening rate of gamma prime particles decreased with increasing cobalt content. Furthermore, a further addition of aluminum to Inconel 738 resulted in an increase in the area fraction of the gamma prime phase and more rapid growth of gamma prime particles during long-term heating compared to standard Inconel 738.