Alloying element losses in pulsed Nd : YAG laser welding of stainless steel 316

Experimental studies of pulsed laser welding of stainless steel 316 in keyhole mode were done to examine a vaporization model based on the kinetic theory of gases and the thermodynamic laws. Undesirable loss of volatile elements affects the weld metal composition and properties. The profile of the keyhole was simulated as a function of time from a 'hydrodynamic' physical model. The power density and pulse duration were the main investigated variables. The model predicts that loss of alloying elements increases at higher peak powers and longer pulse durations. Accordingly, the concentrations of iron, chromium, nickel and manganese were determined in the weld pool by means of the proton-induced x-ray emission and energy dispersive x-ray/wavelength dispersive x-ray analysis. It was shown that the composition alteration, predicted by the model due to varying laser parameters, accords well with the corresponding experimental data.