Impact of pre-treatments on the surface composition, the optical and flow properties of a CuCrZr powder dedicated to laser powder bed fusion use

International audienceProcessing Copper-Chromium-Zirconium alloy by Laser Powder Bed Fusion is not power efficient due to the high reflectivity of the powder at the standard wavelength of the laser (1070 nm). A way to reduce the optical reflectivity is to modify the powder surface. This work aims to study the impact of reduction and oxidation pre-treatments on the surface chemistry of the particles, and their consequences on the powder properties. X-ray photoelectron spectroscopy analyses show that, starting from a 2-3 nm thick native Cu2O layer, a wet atmosphere leads to the formation of a 54 nm thick Cu$_2$O layer, whereas a reduction under hydrogen leads to pure copper. Under Argon, the Cu$_2$O thickness slightly increases to 3-4 nm. The oxidation and the reduction treatments improve the flowability, respectively, by 46 % and 26 %. The reduction increases the reflectivity by 2 %, whereas the oxidation reduces it by 26 %