Effect of heat treatment on microstructure and high temperature tensile properties of cast nickel-base superalloy with high W, Mo and Nb contents

The microstructural features and high temperature tensile properties of M963 superalloy at as-cast, as-solutioned and as-aged conditions were investigated in detail. The results show that the solution treatment at 1220 degreesC for 4 h, AC causes an increase in high temperature yield strength but a drastic drop in high temperature ductility due to the precipitation of both the secondary carbide KC along grain boundaries and at the interdendritic regions and very fine gamma' particles in the dendrite cores. Aging treatment following the solution treatment can improve the high temperature tensile properties of M963 superalloy due to the coarsing of the gamma' precipitate. One stage aging at 850 degreesC for 16 h following the solution treatment causes an increase in both strength and ductility of alloy M963, and two-stage aging of 1089 degreesC /2 h, AC plus 850 degreesC /16 h, AC following the solution treatment further increases the ductility of alloy M963 but slightly decreases its strength.