Influence of Temperature and Microstructure on the Fatigue Behaviour in the Threshold Regime for a Super Duplex Stainless Steel

摘要

The fatigue crack propagation behaviour of a super duplex stainless steel in the near threshold regime at -50°C, 20°C (RT) and 150°C has been studied. The fatigue threshold values of the stress intensity factor range and the effective threshold value of this material are higher at -50°C and 150°C than at RT. The closure threshold value is also smaller at RT than at -50°C, but comparable with that at 150°C. The material aged at 475°C for 3 hours shows similar effective threshold value, but a smaller closure threshold value. Crack propagation mismatch at the interface of the two phases and brittle to ductile fracture transition in the material at -50°C or in the aged material at RT were observed, and possible mechanisms were discussed.