Time-Resolved Detection of Vaporization during Laser Metal Processing with Laser-induced Fluorescence
Brian J. Simonds, Paul A. Williams, John H. Lehman
Element loss during high-power laser processing of metals can lead to deleterious chemical and mechanical effects that negatively impact the processed materials quality. Currently, there is no suitable way to measure element loss in situ and in real time during laser processing. In this work, we show that laser-induced fluorescence (LIF) can be used to temporally resolve individual element vaporization during a laser spot welding of 316L stainless steel. As a proof-of-concept, we measure iron loss during a 500 µs laser spot weld with a time resolution of 5 microseconds. We find that keyhole formation can clearly be identified by a dramatic increase in iron emission from the weld pool. This conclusion is validated by independent, time-dependent measurements of laser absorptance during laser spot welding from our previous work.