Effect of parameters on microstructure and mechanical property of dissimilar joints between 316L stainless steel and GH909 alloy by laser welding

Abstract This paper mainly studied the effects of high-power high-welding speed and low-power low-welding speed on 316 L/GH909 dissimilar metals laser welding joints under the same linear energy. The weld morphology, microstructure and mechanical property were compared and analyzed. The different dimensions of the molten pool between the two welds were verified by the finite element temperature field simulation, and the reason was discussed. From the results, the weld with low-power low-welding speed had a smaller temperature gradient and a lower cooling rate at the edge of the molten pool. The condition of small temperature gradient effectively made the element distribution smoother, relieved the microstructure heterogeneity of the interface layer and alleviated the liquefaction of grain boundaries at the HAZ, thus improving the tensile strength of the welded joint. Since both alloys were based on austenite, there was no common intermetallic compound in this type dissimilar joints. The detailed and systematic elemental analysis of the different phases in the 316 L/GH909 dissimilar metal weld was carried out. Especially, we found that a small amount of Cr element was solid solutioned in γ/Laves low melting phases, and the granular phases distributed at the HAZ of GH909 side were analyzed. This study mainly revealed the nuances between the two welds under the same linear energy, which can provide guidance for this type of GH909/316 L dissimilar metal welding.