Additive manufacturing of CuCr1Zr by development of a gas atomization and laser powder bed fusion routine

Abstract

The research focuses on alloy design, powder production, and laser powder bed fusion (LPBF) of copper alloys. Copper and its alloys play a fundamental role for modern industrial applications due to their excellent thermal and electric conductivity in conjunction with considerable mechanical strength, for example, as welding electrodes and nozzles. By precipitation hardening, the hardness of low-alloyed copper, like CuCr1Zr, can be increased significantly. A combination of the geometry freedom of additive manufacturing with a tailor-made alloy design during powder production offers the opportunity to develop new alloy systems with a focus on the respective application. Experimental results regarding gas atomization, LPBF, property investigations, and property optimization of CuCr1Zr are presented. Powder particles and LPBF parts were analyzed with respect to phase and precipitate formation and compared to benchmark experiments of conventionally cast copper alloys. The microstructure differs significantly. Furthermore, the relative density of the LPBF parts reaches a value of 99.8%.

CuCrZr processed by laser powder bed fusion—Processability and influence of heat treatment on electrical conductivity, microstructure and mechanical properties

“…Process parameters for a laser power of 400 W and a hatch distance of 110 μm, resulting in a volume energy density of 220 J/mm 3 , were developed with respect to the highest density. The volume energy density used is within the process windows of the common literature on LB‐PBF of CuCrZr 35,38–41 . The finally achieved relative density determined by optical microscopy for this parameter set is 99.4%.…”

Pyrometric-Based Melt Pool Monitoring Study of CuCr1Zr Processed Using L-PBF

“…Therefore, the LPBF of copper alloys is being explored, leading to major challenges due to the high thermal conductivity of the powder, poor absorption of laser wavelengths in the range of ≈1070 nm found in standard LPBF machines, and balling (e.g., Reference [ 6 , 7 ]). As a consequence, densities for LPBF copper alloys achieved with common 200–400 W lasers are inferior to those obtained using EBM; the latter being in the range of 93.7% for Cu-4Sn [ 8 ] to 97.9% for Cu-Cr-Zr-Ti [ 9 ] and from 97.65% [ 10 ] to 99.5% [ 11 ] or even 99.8% [ 12 , 13 ] for CuCr1Zr. On LPBF machines with a non-standard high-powered laser, even pure copper powder can be processed: e.g., a density of 96.6% was achieved using an 800 W laser power [ 14 ].…”

A Micro-Computed Tomography Comparison of the Porosity in Additively Fabricated CuCr1 Alloy Parts Using Virgin and Surface-Modified Powders

“…Thanks to new advancements, the processability problem of pure copper or high-copper-containing alloys has been almost completely solved. It concerns both LPBF machine hardware improvements, with lasers having higher power or different emitted wavelengths [14,15], and advancements on the proper selection and modification of the starting raw powder material, with surface-modified powders [16][17][18] or tuned copper alloys [19,20]. Nevertheless, still a higher porosity and higher number of defects are expected from parts manufactured in pure or nearly pure copper, with densities often below the industrial average requirement of ≥99.7% for LPBF.…”

“…For example, densities up to 99.1% were reported by Yan et al for pure copper; similar densities were achieved by Jadhav et al [21] and others [22] with the employment of a high-power (≥1 kW) fiber laser. In the realm of high-copper-content alloys, densities above >99% are reached for, e.g., CuCr1Zr (99.84% in [19]), CuSn0.3 (99.6% in [17]), or CuCr1 (99.1% in [16]).…”