Influences of Cooling Rate After Solution Treatment on Microstructural Evolution and Mechanical Properties of Superalloy Rene 80

Influences of the cooling rate after solution treatment on microstructural evolution and mechanical properties of Rene 80 nickel-based superalloy were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy and mechanical test. Results showed that the high cooling rate decreased the size of secondary γ＇particles in the supersaturated matrix, but led to a high coarsening rate of γ＇ particles during subsequent aging treatment. Despite various coarsening rates, the size and morphology of γ＇ particles in the final microstructures of all samples were close due to the long enough holding time to an equilibrium state. During the aging of 870 ℃/2 h, primary MC started to decompose with the carbide reaction： MC ＋ γ＇ --＊ MrC or M23C6 -t- γ＇. And a number of observations showed that the coarsening of γ＇ particles on grain boundaries resulted in the depletion of γ＇ during aging treatment. The test results indicated that high cooling rate resulted in the presence of quench crack, and the air cooling method following solution treatment was an optimum heat treatment method for Rene 80.