Quantifying Additive Manufacturing Vapor Plumes Using Laser-Induced Breakdown Spectroscopy, Synchrotron X-Ray...

Understanding vaporization phenomena in laser powder bed fusion (LPBF) additive manufacturing has proven challenging; the links between laser-induced metal vaporization, rate of elemental loss, and composition irregularities remain unclear. Here, the vapor plume composition and preferential vaporization effect is quantified during LPBF, using in situ 1 kHz laser-induced breakdown spectroscopy with correlative X-ray synchrotron radiography, multi-physics simulations, and energy dispersive X-ray spectroscopy. It is demonstrated that vaporization increases under keyhole mode, and preferential vaporization causes elemental loss rates of Ni ≈ Fe > Cr > Mo in a Ni-based superalloy, IN625. It is found that the melt pool temperature (T ≈2300 K) can be approximated by cross-referencing vapor pressures, and Raoult's law inadequately describes preferential vaporization. Three simulation approaches are compared to show that introducing temperature-dependent thermophysical properties improves model predictions. The insights into the vapor dynamics of laser-processed IN625 enhance the understanding of compositional changes and elucidate methods to optimize simulations.