Study of microstructural transition in dissimilar weld joint from as-welded to PWHT condition using electron backscattered imaging

Abstract

Transition occurring in microstructures of heat affected zone (HAZ) of a P91-316LN SS dissimilar weld joint was studied using electron backscattered diffraction (EBSD). Kernel misorientation angle and grain boundary character distribution maps were used to study local strain accumulation and evolution of low angle grain boundaries in the HAZ regions. Two microstructural conditions i.e. as-welded and post weld heat treated (PWHT) were investigated. It could be seen that PWHT reduced the strain gradient in the P91 steel’s HAZ which was formed during welding and that localised softening occurred within this region after PWHT.