The investigation of plume and spatter signatures on melted states in selective laser melting

•Melted state detection by monitoring with plume and spatter signatures.•Distinctive plume and spatter signatures among different melting processes.•Plume and spatter signature variation with changing laser power and scanning speed.•During melting, laser power plays a more decisive role than scanning speed. Plume-spatter signatures during Selective Laser Melting (SLM) are a good indication of their corresponding melt states. It is important to build the relationship between the signatures and defects for the SLM process monitoring. In this work, the mechanism of the plume and the spatter was investigated for the melted state detection. Single tracks were produced on the 304L stainless steel powder with monitoring by a Near-Infrared (NIR) camera. Signatures of the plume and spatter during the SLM process were collected for the analyses of the characteristics. Results provided the properties of the plume, the spatter, and the entire target region of the image as well as their relations with the melted tracks. Plume-spatter signatures had distinct behaviors among the underheating, normal, and overheating melting processes. In the melted state variation, laser power played a more decisive role than scanning speed by changing laser energy density. This work contributed to the feasibility and possibility for the SLM process monitoring by the plume and spatter signatures.