Influence of Laser Cutting Parameters on the Microhardness, Roughness, and Microstructure of AISI 304, S355J2, and AlMg3 Alloys

This study provides a comparative and material-specific assessment of how laser cutting parameters affect the surface integrity of three commonly used engineering alloys, thereby extending the current knowledge beyond single-material analyses. The main objective was to quantify and relate changes in surface roughness, microhardness, and microstructure to variations in laser cutting conditions for S355J2 steel, AISI 304 steel, and AlMg₃ aluminum alloy. Variable cutting parameters were applied, including cutting speed, assist gas type and pressure, as well as laser beam power, and their combined effect on the thickness of the remelted and heat-affected zones was evaluated. The results show clear material-dependent trends: S355J2 steel exhibited the lowest surface roughness but the most pronounced surface hardening, with maximum microhardness values reaching approximately 700 HV 0.1 in a relatively narrow heat-affected zone, whereas AISI 304 showed a distinct edge-hardening effect with more moderate roughness. In contrast, the AlMg₃ alloy developed a clearly visible remelted layer and a refined, fine-grained microstructure, accompanied by much lower hardness levels but a more diffuse heat-affected zone. These findings provide original, comparative guidelines for selecting laser cutting parameters tailored to specific materials, enabling the optimization of edge quality and surface properties in industrial applications.