Liquation cracking behavior and control in the heat affected zone of GH909 alloy during Nd: YAG laser welding

Abstract

In this paper, we describe experimental laser welding of GH909 alloy. The forming mechanism of heat affected zone (HAZ) liquation cracking was investigated and improvements to the welding process are proposed. We determined that the occurrence of HAZ liquation cracking proceeds through three stages: intergranular liquation, crack initiation and crack growth. The presence of liquation cracking is associated with low melting eutectics and composition segregation that occurs at the grain boundaries. The segregation caused lattice distortion at the grain boundaries and inhibited the binding force at the solid/liquid interface. The susceptibility to HAZ liquation cracking can be reduced by the migration of a relatively thin liquid film that is produced by reducing the heat input at the grain boundaries during laser welding. GH909 alloy in solid solution treatment condition rather than standard aging treatment was adopted to facilitate laser welding, which results in significantly lower mechanical.