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 ∼13 and ∼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 ∼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 ∼0.6 and ∼0.8 kJ/mm3 favored a better yield of high-density sintered parts.