Microstructure evolution during heat treatment of superalloys loaded with different amounts of carbon

The effects of heat treatment for recovering microstructure of a Ni-based single crystal superalloy with carbon addition have been evaluated. The heat treatment resulted in increased levels of chemical homogeneity. All the samples experienced more γ′ coarsening than as-cast samples. Significant changes to as-cast carbide morphologies were observed. Script-type, MC carbide networks transformed during heat treatment to smaller, spherical Ta-rich MC carbides. Heat treatment caused significant MC carbide decomposition and formation of Cr-rich secondary carbides on or near to decomposed carbides in all modifications. The size of carbides after heat treatment was less than that of cast alloy obviously, and the distribution of carbides became more and more dispersion than in cast alloy.