Laser welding of GH3539 alloy for molten salt reactor: Processing optimization, microstructure and mechanical properties

Abstract

GH3539 is a most promising material for next-generation molten salt reactors (MSR) due to its excellent performance in harsh high temperature molten salt environments. To promote the application of laser welding of GH3539 alloy in the molten salt reactor, the effect of various laser welding parameters on the weld geometry was investigated, as well as the microstructure and mechanical properties of GH3539 laser welded joints. The results indicate that GH3539 alloy has good laser weldability. The weld geometry of the laser welded alloy joint is significantly affected by the laser welding parameters. After processing optimization, the optimized laser welding process parameters were obtained. The microstructure close to the fusion line is a columnar crystal growing perpendicular to the direction of the fusion line. The core of the central portion of the welded joint consists of equiaxed crystals. No apparent “softened” heat-affected zone (HAZ) was discovered in the laser-welded joints. The hardness of the weld metal (WM) is approximately 130% of the hardness of the base metal (BM). Hardness values in different areas of the WM display unique distributions due to the influence of microstructure and intergranular carbides. A small amount of tiny solidification cracking, liquidation cracking is found in welded joints. Compared to specimens at room temperature (RT), both the tensile strength and elongation dropped significantly under the circumstances of elevated temperature. All fractures are located in the BM with a brittle fracture pattern.