Influence of processing parameters on particulate dispersion in direct laser sintered WC-Cop/Cu MMCS

Homogenizing the particulate dispersion in the matrix is an important consideration in obtaining high-quality particulate reinforced metal matrix composites (MMCs) using direct metal laser sintering (DMLS). In this paper, the effects of processing parameters in terms of laser power, scan speed, and powder layer thickness on the particulate dispersion in the DMLS-processed submicron WC-Cop/Cu-1 MMCs were investigated. It shows that for a given scan speed larger than 0.04 m/s, a proper increase in the laser power between similar to 650 W and similar to 750 W leads to a uniform dispersion of smooth and fine WC particulates, due to a sufficient liquid formation and an improved wettability. Whereas, an excessive increase in the laser power results in a severe particulate aggregation, because of the balling effect. There exists a critical scan speed of 0.04 m/s, above which the particulates can be well engulfed by the advancing dendritic front, thereby homogenizing the particulate dispersion in the matrix. A proper decrease in the powder layer thickness to 0.20 mm can alleviate the particulate aggregation, due to the elevated Marangoni convection and liquid capillary forces. (C) 2007 Elsevier Ltd. All rights reserved.