Microstructure and mechanical properties of laser beam welded Inconel 718

Inconel 718 plates were welded using a 2.5 kW CO2 laser. The effects of post-weld solution annealing on the microstructure and tensile properties of the laser beam (LB) welds were investigated, and they were compared with those of gas tungsten are (GTA) welds. While interdendritic gamma/Laves phase eutectic was observed in the fusion zones of both the LB welds and the GTA welds, the size of the gamma/Laves phase and the dendrite arm spacing of the former was significantly finer than that of the latter because of rapid cooling. While the interdendritic gamma/Laves phase dissolved and a certain amount of MC-type carbides remain in the weld fusion zones after solution annealing at 1353K and 1373K, the LB welded joint with the annealing at 1373K followed by ageing treatment was fractured in the base metal and had ductility equivalent to that of the aged base alloy. In contrast to this, since coarse and clustered carbides remained in the GTA weld fusion zones even after annealing at 1373K, the ductility of the GTA welded joints were lower than those of the LB welded joints.