Spatial distributed spectroscopic monitoring of melt pool and vapor plume during the laser metal deposition process

Abstract Laser metal deposition is an additive manufacturing process that allows the production of near net shape structures. In order to obtain structures with reproducible and excellent material properties, it is necessary to understand the behaviour of the process better. Also the monitoring and the development of useful control approaches require a better physical understanding of the process. In this paper we present calibrated spectral measurement results from 400 nm up to 850 nm at different locations in the melt pool region of stainless steel (316L). The spectral information can be used for temperature estimation and the extraction of spectral characteristics. The collected spectra contain specific discrete spectral absorption and emission lines. These lines indicate the onset of the formation of a plasma for the vapor plume and shield gas. The onset takes place even at the applied laser power density level. The presented results can contribute to a better understanding of the process.