Precipitation of μ Phase in Nickel-based Powder Metallurgy Superalloy FGH97

The precipitation behavior of topological close-packed (TCP) μ phase in powder metallurgy (P/M) nickel-based supcralloy FGH97 was investigated. The results showed that proper addition of solution strengthening elements, such as Co, Cr, W, Mo, improved tensile strength, while excessive addition of those elements facilitated the precipitation of μ phase, which seriously aggravated the plasticity of the P/M superalloy. For the heat-treated specimens, the relationship between critical aging time (when μ started to precipitate), aging temperature, and the average electron vacancy number of γ matrix was established.