Surface Modified Copper Alloy Powder for Reliable Laser-based Additive Manufacturing

Abstract

Owing to the high optical reflectivity of copper, silver, and gold in the infrared region, high laser power is required for laser-based additive manufacturing (L-AM). This increases the risk of damaging the laser optics due to sustained back-reflections and renders L-AM of reflective metals an unsustainable technology. To tackle this issue, a novel, industrially upscalable powder surface modification method is proposed and validated using a CuCr1 alloy. The surface of CuCr1 powder is modified by the outward diffusion of chromium in a nitrogen atmosphere, forming a rim around the powder particles. This doubled the optical absorption of the powder. Consequently, a mere 20% of the laser energy is required to process the surface-modified powder by laser powder bed fusion compared to the virgin CuCr1 powder. The fabricated parts demonstrate a very high thermal conductivity of 370 ± 15 W/(m·K) and tensile strength of 439 ± 19 MPa, after applying a suitable post-heat treatment.