RETARDATION OF CREEP IN [001]-ORIENTED SUPERALLOY CMSX-4 SINGLE-CRYSTALS BY SUPERIMPOSED CYCLIC STRESS

Experimentally it was shown that the cyclic stress superimposed on sta tic load in the case of CMSX-4 single crystals at 800 degrees C slows down the rate of the creep process. This effect was explained with the help of a recently developed model of creep in [001]-oriented nickel base superalloy single crystals taking into account the interplay of c reep in gamma channels by dislocation slip, dynamic recovery of the di slocation structure and migration of the gamma/gamma' interfaces. The simulated creep curves are in reasonable agreement with the experiment ally measured ones both for loading with and without the cyclic stress component provided the jog density for creep/cyclic loading is taken to be lower than that for pure creep loading. Thus the retardation of creep by superimposed cyclic loading is attributed to the more difficu lt formation and/or easier annihilation of jogs on vibrating dislocati ons. (C) 1997 Elsevier Science S.A.