Study on the weldability, microstructure and mechanical properties of thick Inconel 617 plate using narrow gap laser welding method

Abstract

Multi-pass narrow-gap welding of thick Inconel 617 plate was conducted with YLS-10000 fiber laser. The influence of different welding parameters on the joint geometry and defects was investigated. The dendrite morphology, grain distribution, crystal texture and stress distribution were analyzed. The microstructure evolution such as element segregation and precipitate behavior was also studied. The micro-hardness, tensile strength at room and high temperature, and toughness impact were measured to evaluate the mechanical properties. The results revealed that the U-shaped or V-shaped filling pass could help the formation of good layer without defects. The maximum grain size of base metal and heat affected zone was less than 200 μm. The grain size of weld zone was large, and the maximum grain size reached 500 μm. Serious stress concentration occurred in the WZ and HAZ. The elements Ti and Mo segregated seriously in the dendrites. The carbides including M6C, Ti(C, N), (Cr, Ni)(C, N) and M23C6 were precipitated in the weld metal. The microhardness, tensile strength and impact toughness of WZ were higher than that of BM at room temperature. The tensile strength decreased with increasing temperature. The fracture mode at high temperature was ductile rupture, which was caused by the accumulation of tiny cavities. Keywords: Narrow gap laser welding, Inconel 617 thick section, Microstructure, Precipitates, Mechanical strength