Absorptivity measurements during laser powder bed fusion of pure copper with a 1 kW cw green laser

Abstract

A 1 kW CW green laser source operating at 515 nm was used to investigate the absorptivity of pure copper powder beds and pure copper substrates. Various interaction regimes were considered, ranging from the solid and/or powder layers, to the liquid state and up to the deep penetration keyhole regime. Reflectance measurements were carried out using an Ulbricht integrating sphere during static tests and single L-PBF tracks. For each experiment, absorptivity values were discussed using the real penetration depth observed on cross-section. Absorptivity values were found to be in relatively good agreement with analytical models of the powder bed and the keyhole regime absorptivity. Such results provide useful insight on the use of green wavelengths for the optimization of the L-PBF process on highly reflective and conductive materials like copper.