Heat treatment structure modification of wrought nickel based superalloy and its creep resistance

The effect of structure modification on creep characteristics of nickel based superalloy EI 698 VD has been studied. The substructure changes were caused by variation of the temperature and time parameters in solution treatments and in precipitation annealing process of the alloy. Through the change of gamma prime morphology and extent of M 23 C 6 carbide precipitation on grain boundaries the creep strength and plastic characteristics were influenced. Significant decrease of lifetime was accompanied with remarkable increase of relative proportion of intercrystalline cleavage fracture mechanisms