Nanoindentation characterization on the temperature-dependent fracture mechanism of Chinese 316H austenitic stainless steel under creep-fatigue interaction

Since the generation-IV nuclear reactors are aiming to operate at higher temperature, the effect of temperature on the creep-fatigue fracture behavior of 316H austenitic stainless steel were studied using nanoindentation technique. The results indicate that intergranular crack was gradually inconspicuous with increasing temperature from 823 to 923 K. However, as the temperature further increased to 973 K, fracture mechanism was found to be dominated by intergranular cracking. Based on the ex-situ mechanical properties at the nanoscale, i.e., hardness (H), elastic modulus (E), and strain rate sensitivity (m) of the fracture edge, a structural damage indicator ln(H/E)/m was proposed to characterize the damage of grain boundaries, for unfolding the relationship between fracture mechanism of creep-fatigue interaction and temperature.