Effects of processing parameters on consolidation and microstructure of W-Cu components by DMLS

The densification behavior and attendant microstructural characteristics of direct laser sintered submicron W-Cu/micron Cu powder system under different processing conditions were investigated in this work. The methods for improving the controllability of laser processing were elucidated. A "linear energy density (LED)", which was defined by the ratio of laser power to scan speed, was used to tailor the powder melting mechanisms. It showed that using a suitable LED between similar to 13 and similar to 19 kJ/m combined with a scan speed less than 0.06 m/s led to a continuous melting of the Cu component, yielding a sound densification larger than 92% theoretical density without any balling phenomena. With a favorable sintering mechanism prevailed, a proper increase in the LED above similar to 13 kJ/m, which was realized by increasing laser power or lowering scan speed, produced a homogeneous microstructure consisting of a novel W-rim/Cu-core structure. Narrowing the scan line spacing to 0.15 mm was able to enhance the inter-track bonding, and to reduce the roughness of laser sintered surface. Decreasing the powder layer thickness to 0.15 mm was a promising approach for improving the inter-layer bonding coherence. A "volumetric energy density (VED)" was defined to facilitate the integrated process control by considering the combined effect of various processing parameters. It was found that setting the VED within similar to 0.6 and similar to 0.8 kJ/mm(3) favored a better yield of high-density sintered parts. (C) 2008 Elsevier B.V. All rights reserved.