Laser and hybrid laser welding of type 316L(N) austenitic stainless steel plates

The effect of laser, Hybrid Laser-Tungsten inert gas (HLT) and Hybrid Laser-Metal inert gas (HLM) welding processes on the microstructure and mechanical properties of 5.6 mm thick 316L(N) stainless steel weld joints have been studied. The differences in weld metal microstructure and mechanical properties of the weld joints were evaluated and discussed. Weld bead geometry, ferrite number (FN), solidification mode, secondary dendrite arm spacing, hardness and tensile properties are compared. Laser weld joint showed narrow weld bead profile and a higher cooling rate than the hybrid laser arc weld joints and the weld metal manifested austenitic solidification mode. HLT weld displayed coarser weld metal microstructure due to higher heat input and austenitic ferritic solidification mode. HLM process possesses moderate heat input and cooling rate. The HLM weld metal exhibited ferritic austenitic solidification mode and 2.5 FN. The hardness of weld metal was higher in hybrid welding processes due to the higher ferrite content. HLM weld joint has higher yield strength, ultimate tensile strength and ductility compared to that of the other weld joints. HLM welding process also permits higher gap tolerance with filler metal addition and is recommended for welding of type 316L(N) stainless steel.