Strain-time effects in low-cycle fatigue of nickel-base heat-resistant alloys at high temperature

Abstract

A series of strain controlled low-cycle fatigue tests in the simulated high-temperature gas-cooled reactor (HTGR) helium environment were conducted at 900°C on Hastelloy X and its modified version, Hastelloy XR. In those tests the effects of strain rate and hold time on high-temperature low-cycle fatigue behavior were investigated. Decreasing the strain rate led to notable reductions in the fatigue life. In the tests with the trapezoidal strain waveform, the fatigue life was found to be reduced most effectively in tensile hold-time experiments. The tendency was interpreted through the feature of the crack morphology.