Processing of ZrB2 tribo-ceramics by reactive spark plasma sintering of ZrH2+2B subjected to high-energy pre-ball-milling

Abstract

The reactive spark plasma sintering (RSPS) of monolithic ZrB2 ceramics from ZrH2+2B powder mixtures subjected to shaker pre-milling was investigated, and compared with other three sintering approaches. It was found that RSPS is optimal at 1850 °C, which results in fully-dense ZrB2 ceramics with ∼20 GPa hardness. Comparatively, at 1850 °C RSPS from the simply-mixed ZrH2+2B powder mixture, SPS from the commercial ZrB2 powder, and SPS from the shaker-milled ZrB2 powder result in non-dense (76.7–86.7%) and softer (6.0–11.8 GPa) ZrB2 ceramics. Furthermore, the optimally RSPS-ed ZrB2 ceramic was subjected to unlubricated sliding-wear tests against diamond under 40 N load for 1000 m of sliding, demonstrating that it is a promising tribo-ceramic that only undergoes mild tribo-oxidative wear at 10–8 mm3/(N·m) in the form of a slight plasticity-dominated two-body abrasion with eventual formation and partial loss of a self-lubricating and protective oxide tribolayer.