Numerical and experimental analysis of effects of processing conditions on melt pool stability of CuCr1Zr parts produced by laser powder bed fusion (L-PBF)

Processing CuCr1Zr copper alloy using the L-PBF process is extremely difficult due to its high reflectivity at the common L-PBF wavelength of 1064 nm and high thermal conductivity. Therefore, previous studies utilized a high laser power energy density to perform the 3D printing of CuCr1Zr parts. However, at high laser energy densities, the physics that lead to the formation of the melt pool, such as the laser absorption, Marangoni force, and recoil pressure, are extremely complex. Notably, these phenomena have both individual and interactive effects on the stability of the melt pool. Thus, identifying the processing conditions (i.e., laser power, scanning speed, and hatching space) that lead to stable scan tracks and smooth surface scanning through experimental trial-and-error methods is costly and time-consuming. Accordingly, this study develops a Computational Fluid Dynamics (CFD) simulation model that considers the effects of all three factors on the formation of the CuCr1Zr melt pool. The simulation model is verified with experimental data reported in the literature. The verified model is then utilized to determine the L-PBF processing conditions that lead to stable scan tracks and surface scanning. The numerical and experimental results reveal that the laser power of 500 W, scanning speed of 600 mm/s, and hatching spaces between 80 and 100 µm ensure the stability of both single-scan tracks and surface scanning and yield a smooth surface morphology as a result.