Effect of high-temperature preheating on pure copper thick-walled samples processed by laser powder bed fusion

The Laser Powder Bed Fusion (LPBF) also called Selective Laser Melting technology uses for the layer-based part fabrication laser beam as the main energy source for melting a powdered material. The processing of pure copper by LPBF technology is a challenge due to its high laser beam reflectivity, thermal conductivity and affinity to oxygen. Thus, for reaching homogeneous sample in an acceptable quality a high power Nd: YAG fibre laser sources are used. In this study, the effect of Nd: YAG fibre laser with a maximum power of 400 W and 400 degrees C high-temperature base plate preheating as another heat source on the relative density of pure copper thin-walled and thick-walled samples was investigated. Moreover, the effect of layer thickness, laser speed, laser velocity, hatch distance, sample width, scanning and remelting strategy was studied. Further on, the effect of powder bed preheating on the copper powder melting, laser beam reflectivity, wetting and solidification conditions and powder and part oxidation was discussed. Using the statistical methods for experimental planning the behaviour of each observed process parameter was revealed and the proper combination of process parameters was stated. It was found that for reaching relative density over 99% the process parameters should be set from observed range as following: layer thickness 0.03 mm, laser power 400 W, laser velocity 505 mm center dot s 1, hatch distance 0.06 mm and powder bed preheating of 400 degrees C. Despite the high value of relative density, the issues connected with layer and track bonding attributed to thin oxide layers were not successfully eliminated.

Automated summary

The study investigated the impact of using a high-power laser source and high-temperature base plate preheating as a heat source on the relative density of pure copper thin-walled and thick-walled samples, as well as the effects of various process parameters on the quality of the parts. The results showed that to achieve a relative density of over 99%, the proper combination of process parameters must be set.