HIGH-TEMPERATURE, LOW-CYCLE FATIGUE BEHAVIOR OF AISI TYPE 316LN BASE-METAL, 316LN-316 WELD JOINT AND 316 ALL-WELD METAL

Studies on the strain-controlled low cycle fatigue (LCF) behaviour of type 316LN stainless steel (SS) base material, type 316 SS all-weld metal and 316LN-316 weldments prepared by the shielded-metal-arc-welding (SMAW) process at 873 K have been conducted at a strain rate of 3 x 10(-3) s-1. The results indicated that the LCF resistance of all-weld metal was better than that of the base material while weldments displayed the least fatigue resistance. The better fatigue resistance of the all-weld metal has been attributed to the beneficial effects associated with fine distribution of delta-ferrite in the austenite matrix while the poor fatigue resistance of the weldment has been ascribed to the detrimental effects associated with coarse grain size and surface intergranular cracking in the heat-affected zone. The cyclic stress amplitude varied with the material condition and strain amplitude in the LCF test.