Characterization of the absorptance of laser irradiated steel sheets

This work presents an experimental-numerical methodology aimed at deriving the absorptance of both a low output power CO₂ laser beam and a Yb fiber laser beam applied to an AISI 304 stainless steel cold-rolled sheet under two different conditions of the sample surface: without and with a spray graphite coating. The absorptance values were obtained by minimizing the error between temperature evolution measurements at various locations of the irradiated sheet and the corresponding finite element predictions. The values obtained for the CO₂ laser were a = 0.20 for the stainless steel and a = 0.41 for the graphite coating. For the Yb fiber laser, the values were a = 0.40 for the stainless steel and a = 0.64 for the graphite coating. Degradation of the graphite layer was observed when the resistance temperature of the graphite coating was exceeded.