Influence of severe shot peening and PVD thin titanium coated on 316 austenitestainless steel microstructure and mechanical properties by laser beam welding

This study investigates the effects of physical vapor deposition (PVD) thin titanium coating and severe shot peening (SSP) on the mechanical characteristics and microstructure of 316 austenitic stainless steel plate with a thickness of 2 mm, using laser beam welding (LBW). This investigating to the grain size and boundary variations, as well as the phase transitions from austenite to other phases in the fusion zone and heat-affected zone (HAZ).The laser beam welding experiments with welding parameters of 800 W laser beam power, 200 mm/min welding speed, and a welding focus distance of 7 mm. The austenite phase in the HAZ changes into ferrite, σ phase and retained austenite during the welding process. The kinetics and extent of these phase transitions are impacted by the intense shot peening and PVD thin titanium coating. The austenite phase also changes into σ phaseand retains austenite at the fusion zone. Grain boundaries and size variations are noted across the weldment zones. The fusion zone and heat-affected zone (HAZ) boundary exhibits distinct microstructural characteristics, such as modified grain boundaries and size as a result of welding's thermal influence. Moreover, the mechanical characteristics and corrosion resistance of the welded joints are impacted by the presence of alpha (α) titanium phases, which are identified by their hexagonal close-packed crystal structure, within the stainless steel matrix. The average hardness values were found to be 222 BHN in the FZ and 187 BHN in the base zone. Present research at the fusion zone of different weldments has enhanced the tensile and bending characterizes and increased corrosion resistance.