Transition of creep damage region in P91-Alloy800-SS316LN dissimilar metals weld joint

Abstract

The creep behaviour of P91-Alloy800-SS316LN dissimilar metals weld joint (DMWJ) has been assessed at 823 K in the stress range of 180–260 MPa. Creep strain accumulation in the DMWJ was higher under high stress regime than the low stress regime. Transition of creep damage and fracture in the DMWJ occurred from P91 steel base metal at high stress regime to the interface region of P91 CGHAZ-IN182 weld metal at lower applied stress with significant reduction in ductility. Kernel average misorientation indicates that the localized increase in strain at the P91 CGHAZ-IN182 weld metal interface region under creep loading in comparison to that of the pre-creep condition. Enhanced heterogeneity in strain distribution, carbon migration, coarser precipitates and soft zone formation at the P91 CGHAZ-IN182 interface region have been attributed to the premature failure of DMWJ in comparison to P91 steel.