Infrared thermal imaging for melt pool analysis in SLM: a feasibility investigation

Abstract

Melt pool dimension can help to relate process parameters and build part quality in selective laser melting (SLM) process. In this study, a near-infrared thermal imager (about 670 nm spectral range) was employed to collect powder layer thermal signal in SLM machine using nickel-based alloy as raw powder material. Radiant temperature distribution at different build heights has been acquired and melt pool sizes have been analysed. The major findings are as follows: (1) It is possible to estimate melt pool dimension based on the identified radiant liquidus temperature and appropriate thermal imager setting, but it is difficult to obtain true temperature. (2) At nominal process conditions of 600 mm/s beam speed and 180 W beam power for Inconel 718 powder, the melt pool has a length of about 0.36 mm and a width of about 0.21 mm. Build height seems to have little effect on melt pool dimensions.

Keywords

• selective laser melting
• infrared
• nickel alloy
• melt pool