Multi-laser powder bed fusion of Cu10Sn using low-power 450nm diode lasers

Due to its inherent high reflectivity, the processing of copper and its alloys is challenging using low power lasers. Literature reviews indicate that using a 450 nm blue laser for processing copper increases absorptivity dramatically from 5% to 65% (x13 higher) compared to traditional laser powder bed fusion (LPBF). Therefore, this study aims to demonstrate that diode lasers with a wavelength of 450 nm are suitable for producing Cu10Sn samples. In this work, diode point melting additive manufacturing technique was used and single layers were produced using diode lasers connected to the X-Y portal to scan on the copper substrate. Various hatch distances (i.e., 50, 75, 100, and 125 µm), scanning speeds (ranging from 150 to 2100 mm/min), and laser powers (20 and 40 W) were selected as process parameters. To determine the mechanical and physical properties of the sample, surface roughness, relative density and melt pool characterization were examined. The results showed that the surface roughness value of samples produced with low hatch distance and low scanning speeds (i.e., in high surface energy values) for 20 W laser power is approximately up to 3.5 times lower than that of 40 W laser power. Additionally, optical analysis of the top surface images revealed that the surface energy density values of Cu10Sn samples with a relative density of 85% or higher ranged between 22 and 30 J/mm². Furthermore, the highest relative density value was found to be 87.84% with laser power of 40 W, hatch distance of 50 µm, and scanning speed of 2100 mm/min.