The effect of chromium on the solubility limits of the [gamma][prime]-forming elements in a Ni-Fe-Cr base superalloy

The belief that chromium lowers the solubility limit of the [gamma][prime]-forming elements in the matrices of nickel-base superalloys is widespread among materials scientists. The main constituents of the [gamma][prime]-precipitates are nickel, aluminum and titanium. This idea also afford an explanation for the occurrence of [gamma][prime]-free zones along grain boundaries in superalloys: (1) chromium precipitates as carbide in the grain boundaries; and (2) the ensuing chromium depletion in seams along the grain boundaries raises the solubility of the [gamma][prime]-forming elements and thus suppresses the formation of [gamma][prime]-precipitates. Ternary and quaternary phase diagrams published by Taylor and Floyd lent some support to the mentioned belief. The doubt shed on it by Tien and Gamble did not receive the attention it deserved. Below the results of an experimental investigation into the effect of chromium additions on the solubility limits of the [gamma][prime]-forming elements in a commercial nickel-base superalloy are reported.