Sintering of tungsten powder with and without tungsten carbide additive by field assisted sintering technology

Tungsten powder (0.6–0.9 μm) was sintered by field assisted sintering technology (FAST) at various processing conditions. The sample sintered with in-situ hydrogen reduction pretreatment and pulsed electric current during heating showed the lowest amount of oxygen. The maximum relative density achieved was 98.5%, which is from the sample sintered at 2000 °C, 85 MPa for 30 min. However, the corresponding sintered grain size was 22.2 μm. To minimize grain growth, nano tungsten carbide powder (0.1–0.2 μm) was used as sintering additive. By mixing 5 and 10 vol.% WC with W powder, densification was enhanced and finer grain size was obtained. Relative density above 99% with grain size around 3 μm was achieved in W–10 vol.% WC sintered at 1700 °C, 85 MPa, for 5 min.

► W powder (0.6-0.9 µm) sintered by FAST (2000oC, 85 MPa, for 30 min) was ~99% dense.
► Excessive grain growth could not be avoided and the final grain size was 22 µm.
► WC additive(10 vol.%) allowed >99% density even at 1800oC, 85 MPa, for 5 min.
► The grain size of the material was reduced to 3 µm (86% reduction).
► The hardness was increased from 35 HRC in pure W to 50 HRC in W-10 vol.%WC.