A comparative evaluation of low cycle fatigue and creep-fatigue interaction behaviour of 316L(N) stainless steel, 316 weld metal and 316L(N)/316 weldjoint at 873 K

Low cycle fatigue (LCF) and creep-fatigue interaction behaviours of 316L(N) base metal, 316 weld metal and weld joints were studied at 873 K over vari ous strain amplitudes. Hold times were introduced in tension or compression peak strains, with the duration varying from I min. to 90 mins. The cyclic hardening observed is attributed to dynamic strain ageing and cyclic softe ning seen in the weld metal is ascribed to the annihilation of dislocations . The better fatigue and creep-fatigue life(1 min. tension) seen in the wel d metal compared to the base metal was due to reduced crack propagation rat e associated with crack deflection by many transformed S-ferrite boundaries . The poor fatigue resistance of the weld joints was ascribed to intergranu lar crack initiation associated with coarse grain size in the heat-affected zone. The factors that contribute to decrease in fatigue life with hold ti me were identified to be enhanced intergranular damage, assisted by oxidati on.