Selective laser melting of tungsten heavy alloys

Selective laser melting (SLM) was used to fabricate different W-Ni-Fe tungsten heavy alloy grades (Ni:Fe=7:3). Microstructural development and the resulting texture in the finished parts was evaluated with respect to the Ni and Fe content, initial powder characteristics, process parameters (laser power, scanning speed, hatch spacing) and the used scanning strategy. The effect of Ta alloying (W5Ta7Ni3Fe) on grain refinement and strength was also investigated. To obtain full densification, a sufficient energy density has to be provided to melt the tungsten particles as the amount of the liquid phase forming elements is not sufficient to densify the material only by liquid phase sintering. Due to the rapid solidification during cooling, a dendritic microstructure of tungsten in γ-phase, as well as increased contiguity of W grains was observed. To obtain the desired microstructure and properties, a post-process heat treatment was required.status: publishe