Densification of pure copper by selective laser melting process

Abstract

Pure copper is utilized as a material for products with complicated shape and high thermal conductivity such as heat exchangers. However, it is difficult to fabricate pure copper parts with high density by the selective laser melting (SLM) process. One of the reasons is considered to be its high thermal conductivity by which the heat in the melt pool rapidly diffuses away. Additionally, the lower rate of energy absorption of fiber laser power for pure copper makes the size of melt pool smaller. In this research, the optimum fabrication condition of high-purity 99.9% copper fabricated by SLM process was investigated by evaluating the density and microstructure. As a result, it was found that the optimum condition of laser power and scan speed are 800~900W and 300 mm/s, respectively, and the optimum energy density is around 1000 J/mm³, which is much higher than that of other materials due to high reflectivity and high thermal conductivity of pure copper. And also, it was found that the hatch pitch is important factor to achieve the densification of the as-built specimen and the optimum hatch pitch was 0.01 mm. The high density parts were successfully fabricated by the optimum fabrication condition. The maximum density of the as-built specimen was 96.6 % and was much higher than that of the as-built part already reported.