Experimental Analysis of Emissivity in Inconel 718 for Laser Metal Deposition Temperature Monitoring with Thermal Imaging

This contribution investigates the emissivity of Inconel 718 in the context of laser metal deposition, focusing on the impact of surface finish variations resultant from additive manufacturing techniques and the challenges it poses when monitoring the process via thermal imaging. Our methodology involves examining the emissivity of Inconel 718 samples produced through laser metal deposition, with a particular focus on the Mid-Wave Infrared and Long-Wave Infrared spectral ranges, common in industrial-grade thermal cameras. We perform directional spectral measurements from 100 °C to 900 °C in a controlled atmosphere using a custom-made emissometer and analyze the differences between samples synthesized via casting and laser metal deposition. The data were also treated to obtain total hemispherical emissivity values and to compare them with the literature data. Finally, we perform a temperature calculation error analysis to clarify the conditions and emissivity input data under which infrared cameras should operate in these additive manufacturing processes.