Effects of Laser Welding on the Mechanical Properties and Microstructure of AISI 304 Stainless Steel

The search for new processes in the manufacture of agricultural machinery and implements has identified stainless steel laser welding as a promising alternative to conventional welding methods such as Gas Metal Arc Welding (GMAW) and Gas Tungsten Arc Welding (GTAW). However, its effects on mechanical and microstructural properties are not yet well-documented in the literature. This study aims to evaluate the performance of manual welds using the CO₂ laser process and understand its effects on welding 2 mm thick AISI 304 steel sheets. The welding was performed under various conditions: autogenous with no root opening, with filler metal, with a 1 mm root opening, and using filler metal without root opening. To analyze the joints, Scanning Electron Microscopy (SEM), microhardness testing, mechanical resistance evaluation, fatigue testing under uniaxial loading, and fractographic analysis of the tested components were employed. The results showed significant pore formation in the molten regions during autogenous welding, as observed in the microstructure. The microstructure of these regions predominantly displayed delta ferrite and lathy ferrite phases across all conditions. In terms of mechanical resistance, autogenous welding achieved higher load-bearing capacities, with fractures consistently occurring in the weld metal region across all conditions. Despite a large variance in fatigue resistance, the data indicates that both autogenous welding and welding with filler metal and no root opening resulted in a higher number of cycles to failure.