Intensity-dependent absorption signature for in situ process characterization in laser processing of 316L

Abstract

Recent research has introduced custom beam shapes as a novel tool to stabilize laser-based powder bed fusion of metals (PBF-LB/M) and laser welding. To facilitate beam shaping in the future, new processes must be developed. However, the process development in PBF-LB/M and laser welding is time-consuming due to its empirical and iterative approach. In the center of this procedure stands the ex situ analysis of test specimens. The process development could be significantly accelerated by replacing the physical ex situ analysis with digital in situ data analysis. Therefore, this work investigates the possibility of an in situ data-based process characterization under process-near conditions for laser welding and PBF-LB/M. For this, the changes in the degree of absorption over a stepwise increase in laser power are studied for various combinations of laser spot size and beam profiles. The measurements are taken using an integrating sphere within a custom-designed testing setup. Additionally, a high-speed camera was deployed. An intensity-dependent absorption signature was found that describes the changes in the degree of absorption over an increase in mean radiation intensity independent from the beam shapes. This absorption signature contains information about the corresponding process behavior and its characteristic trend. These results are the next steps toward in situ absorption-based process characterization for accelerating process development in PBF-LB/M and laser welding.