Dry sliding wear behaviour of ZrB2-based ceramics: Self-mated and cross coupling with alumina

Systematic dry sliding wear tests with monolithic ZrB and AlO pins coupled to ZrB, ZrB-20 vol% SiC and AlO discs were carried out in a disc-on-pin configuration. The steady state friction of ZrB self-mated or cross coupled with AlO was about 1.1. Self-mated monolithic ZrB discs worn about three orders of magnitude more than self-mated AlO discs. ZrB pin wear rate was almost double when coupled to ZrB or ZrB-20 vol% SiC discs than when coupled to AlO discs. The wear track of ZrB-based materials showed an oxygen increment due to humidity-driven tribo-reaction. In all the systems, the main wear mechanisms observed were microfracture and abrasion. Numerical calculations and fracture models were employed to describe the wear mechanisms. By nanoindentation tests on worn and unworn areas, a significant lower hardness of the debris layer formed when ZrB materials were involved.