Effect of hot extrusion and heat treatment on microstructure of nickel-base superalloy

Effects of hot extrusion (HEX) and heat treatment on prior particle boundary (PPB), MC carbides, γ′ precipitates and grain size of nickel-base FGH96 superalloy were studied. The results show that PPB consists of large γ′, MC carbides enriched with Ti, Nb and a modicum of oxides. Thereafter, it can efficaciously tune γ′ precipitate size from micrometer down to nanometer region and simultaneously results in the annihilation of PPB by HEX process. The activation energy for grain growth of as-HEXed FGH96 superalloy was measured to be 402.6 kJ/mol, indicating that γ′ precipitate serves the critical role in inhibiting grain growth under sub-solvus heat treatment. Moreover, the results reveal that grain growth is primarily restrained by MC carbide in the case of super-solvus temperature.