Effect of the degree of densification on the unlubricated sliding-wear behaviour of monolithic B4C ceramics

The unlubricated sliding-wear behaviour of monolithic B4C ceramics with densification degree from ∼62 % up to ∼99.1 %, and therefore hardness from ∼7.9 GPa up to ∼35.3 GPa, was investigated. It was found that the specific wear rate decreases somewhat asymptotically by one order of magnitude (from 10–7 down to 10–8 mm3/(N m)) with the increase of densification degree/hardness. This is because, while wear always occurred by abrasion, below a certain threshold of densification/hardness it took place predominantly in brittle mode by fracture-dominated three-body abrasion and above that threshold predominantly in ductile mode by plasticity-dominated two-body abrasion. Finally, it was found that over-sintering of monolithic B4C ceramics above their near-full densification condition is impractical and could even be detrimental for tribological applications.