Unveiling the strengthening mechanism of laser welded fusion zone of dissimilar Ni-based superalloys

Abstract The strengthening mechanism of a laser welded fusion zone between two dissimilar Ni-based superalloys is studied. The microstructure of as-welded fusion zone is columnar grain featured with a micron scale dislocation cellular substructure. Strengthening component analysis of aged fusion zone at 650 °C reveals the hardening contribution of gamma prime phase (~52%), dislocation cellular substructure (~28%) and solid solution elements (~19%). Our results indicate that the formation of dislocation cellular structure endows fusion zone with higher strength particularly at 600 and 650 °C, which provides novel insights into strengthening of welded Ni-based superalloy.