A study of direct welding of dissimilar materials of borosilicate glass and 304 stainless steel using a green picosecond laser

Welding borosilicate glass to stainless steel is challenged by their vastly different thermophysical properties, which typically induces stress and cracking. Ultrafast lasers overcome this by utilizing non-thermal, nonlinear absorption to create joints with minimal heat input. However, the nanoscale mechanisms governing interface formation are still unclear. In this study, borosilicate glass and stainless steel were successfully joined using a green picosecond laser. The effects of key parameters including laser power, repetition frequency, and pressing force on the weld quality were systematically investigated. Advanced characterization via SEM and TEM revealed that the interfacial microstructure consists of laser-induced periodic surface structures (LIPSS) and blocky glass, with the transition zone containing amorphous, crystalline, and mixed phases. Elemental migration was observed to mitigate composition segregation, thereby enhancing bonding. Although microcracks formed due to thermally induced stresses from material property differences, the joints achieved an average load capacity of 67.14 N under optimal parameters. The improved mechanical performance is primarily attributed to the mechanical interlocking from serrated interface structures and the reduced microstructural gradients across the reaction layers. This work provides significant insights into the interfacial mechanisms of glass-metal welding and demonstrates the potential of picosecond laser processing for high-performance dissimilar material joining in the field of manufacturing.