The multichannel pyrometer of the spectral ratio for on-line monitoring in the powder bed additive technologies

Optical diagnostic methods were used to study the physical processes occurring on the surface of the melt in the technology of selective laser melting (SLM) of metallic powders. Independent registration of the fraction of reflected laser radiation and thermal radiation from several points of the surface of the melt were carried out simultaneously. This made it possible to distinguish changes in the surface relief and subsurface processes of heat and mass transfer during laser heating. It is shown that the frequency and amplitude characteristics of signals obtained by optical diagnostics make it possible to identify the moments of intensification of convective heat and mass transfer. The results of the research can be used to develop methods and tools for on-line monitoring and control of the SLM process.