Backscatter absorption spectroscopy for process monitoring in powder bed fusion

Laser powder bed fusion is a metal 3D printing technology that involves melting and solidifying a metal powder using a process laser or electron beam. The interaction of metal vapors with the melt pool is known to cause manufacturing defects. Here we use absorption spectroscopy of laser light reflected from the liquid metal surface to measure atomic Ti vapor during processing of Ti-6Al-4V inside the vapor cavity forming in the melt pool. The absorption line strength and shape were found to vary significantly with processing parameters. In addition, laser-induced fluorescence (LIF) was observed, providing further opportunities for in situ diagnostics.