Pulsed laser welding and microstructure characterization of dissimilar brass alloy and stainless steel 308 joints

The laser welding of stainless steel and brass is difficult due to their different physical properties, including thermal conductivity and melting point. In this study, the laser welding of stainless steel 308 and brass was experimentally investigated. To systematically investigate the effects of different thermophysical properties, including the heat transfer rate, thermal conductivity, and laser beam interaction in relation to the beam absorption coefficient, the temperature of the melt pool zone was measured while changing welding conditions. Different temperature gradients were obtained by changing different parameters including the laser peak power, nozzle distance, and laser beam deviation. The results showed that an asymmetric melt pool formed, to which the melting of brass made a higher contribution. Due to the lower melting temperature and the higher thermal conductivity of brass, the measured temperature and the melt size of brass were higher. The microstructure of the melt pool consisted of intermetallic compounds. Variation of melt pool size (width and depth) and temperature could be affected by laser peak power and reductions in the nozzle distance than the other parameters. For instance, 1 mm increase in the nozzle distance reduced the melt pool zone temperature by approximately 20 °C for stainless steel. Furthermore, an increase in the laser peak power raised the maximum measured temperature to about 225 and 160 °C for brass and stainless steel sides, respectively. At the same time, the amount of temperature reduction at a period of 20 s for stainless steel is almost half that of brass.