Creep Deformation of Inconel Alloy 718 in the 650�C to 760�C Temperature Regime

Abstract

The steady-state creep behavior of a commercial grade Inconel alloy 718 has been studied over the temperature range of 650°C to 760°C at initial applied stress levels ranging from 276 MPa up to 724 MPa. Two age heat treatments were also compared and found to exhibit comparable stress exponents and apparent creep activation energies indicating that the fundamental steady-state creep deformation mechanisms were independent of age heat treatment. In the case of both heat treatments, the creep stress exponents and activation energies are significantly higher than those of pure Ni (i.e. n=5 and Qc=Q,=280 kJ/mole) assuming dislocation creep as the rate limiting deformation mechanism. The high stress exponents reflect the strengthening imparted by the Y precipitates while the high creep activation energy is controlled y N suggested to reflect multi-component diffusion precipitate coarsening as rate limiting for steady-state creep deformation.