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The absorptivity of laser radiation of metals is investigated in several studies. Therefore, absorption coefficients depending on temperature or roughness are known. However, many processes use iterative processing strategies, such as additive manufacturing, laser beam bending, or laser-assisted incremental forming. Simulations of these processes often use literature data for absorption coefficients and do not consider the variation of absorptivity during the process. In this study, the influences of multiple laser beam processing on absorptivity are investigated for stainless steel sheets. Absorption and roughness measurements are compared before and after heating treatments with the laser beam or in an oven. It is shown that an increasing amount of laser heating cycles correlates with higher absorptivity and higher roughness values. However, this increase of roughness is not considered to be sufficient for enhanced absorptivity. On the one hand, similar changes of absorptivity were detected when heating steel sheets in an oven. These oven-heated specimens do not show extensive roughness changes. On the other hand, the same amount of laser heating cycles with additional cool down time after each cycle results in a negligible absorptivity change. Therefore, the variation of the absorptivity is attributed to oxidation.

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