Fatigue and Fracture Resistance of 316H Stainless Steel With Prior Creep Damage

Abstract

316H stainless steel is widely used in high temperature components for advanced gas cooled reactors. Some plats have been de-rated to temperatures below the creep regime, due to the presence of creep damage in some components. However, such damaged or defected components must still satisfy structural integrity criteria for fatigue crack growth and fracture toughness behaviour. Therefore work has been performed to examine the fatigue and fracture toughness resistance of prior creep damaged material. A large block of material has been globally creep damaged (GCD) at 550 °C to the onset of tertiary creep behaviour. In this work, half sized compact tension C(T) specimens have been extracted from 316H blocks which were both pre-compressed and prior creep damaged at 550 °C. Fatigue crack growth and fracture toughness tests were subsequently performed on them. Note that prior to creep, this block was pre-compressed (PC) to 8% plastic strain at room temperature in order to work harden the material and limit the influence of crack tip plasticity in subsequent creep crack growth tests. The results, when compared to those previously obtained from as-received (AR), pre-compressed (PC) and locally creep damaged (LCD) standard sized C(T) samples, show an overall reduction of the fracture energy J. However, the global creep damage method does not introduce substantial changes on the fatigue crack growth behaviour of the material.