Direct Metal Laser Fabrication of Cu slabs from powder precursor: surface depth of melt and furnace temperature issues

Abstract

A DMLF processing unit based on a raster-scanned 80 W CO2 laser beam has been developed to process single layers of metallic powder precursor. The process chamber provides atmosphere control (high vacuum and inert gas refill) besides temperature elevation up to 700 oC. In this work, copper powder precursor is confined inside a refractory steel mask surrounded by an aluminum oxide jacket that acts as insulator. The powder layers can have thicknesses of 0,5 and 1 mm. An infrared pyrometer measures in real time the temperature at one location in the surface of the powder bed. Scan speed, scan step, and furnace temperature have been varied to find combinations of such parameters that render surface melting and maximum densification. Partially melted samples were produced and their mass density was measured. Micro-hardness and surface roughness were also measured along the resolidified surface, the first rendering an average of 80,6 HV compared to the 90-105 HV of oxygen free copper, while the second resulting in an 8 m Ra value. Maximum melt of depth achieved is ~0,15 mm followed by a sintered layer.