A Prospective into Rapid Consolidation of W-Ni-Fe Based Tungsten Heavy Alloys with the Addition of Nb and Mo Aided by Spark Plasma Sintering

Spark plasma sintering of tungsten heavy alloys can help achieve optimum penetration properties in kinetic energy penetrators by taking advantage of grain size refinement through rapid consolidation during spark plasma sintering utilizing its unique heating mechanisms. The current study explores the effect of adding 1.25, 2.5, and 3.75 wt.% of Nb and Mo to a 90W-7Ni-3Fe base tungsten heavy alloy sintered by spark plasma sintering. Base alloy and Mo added alloy could be sintered at a lower sintering temperature of 1275 °C compared to 1500 °C in conventional sintering. Moreover, Nb addition further lowered the sintering temperature to 1175 °C in SPS due to a possible eutectic reaction between Ni and Nb, causing liquid formation at lower temperatures. The resulting microstructure exhibited a tungsten grain size of 5.48 ± 2.25 µm for base alloy, which was reduced with Mo addition to 3.72 ± 1.22 µm for 3.75 wt.% Mo alloy and 3.78 ± 1.13 µm for 3.75 wt. % Nb alloy. Contrary to the conventional liquid phase sintering, SPS of tungsten heavy alloys yielded a non-uniform microstructure due to localized and non-uniform heating in the material. Additionally, the shorter sintering durations do not allow the formed liquid phase to be spread evenly in and around the sample. The fine tungsten grain observed in the alloys resulted in a hardness of 352 ± 12 HV for the base alloy, which increased to 453 ± 27 and 470 ± 11 HV for 3.75 wt.% Mo and 3.75 wt.% Nb respectively attributed to tungsten grain refinement.