Tribological investigation of Si3N4-hBN on HXLPE bearing couple: Effects of sliding velocity and contact load

Abstract

In present study, the effects of sliding velocity and contact load on the tribological properties of silicon nitride based bearing couples were investigated via the pin-on-plate tests. Pure Si3N4 and its composite (20 vol% hBN content) pins were sliding against highly cross-linked polyethylene (HXLPE) discs under simulated body fluid lubrication. Moreover, the solid lubrication film forming mechanism was investigated via worn surface characterization.For Si3N4–20 vol% hBN/HXLPE bearing couple, friction coefficients and wear rates were decreased with increasing of the contact load or sliding velocity (p-values < 0.001). Two-way ANONA analysis show that these two factors are significantly correlated (p-value = 0.011). Abrasion of the polymer disc is the main wear mechanism. Interfacial lubrication is achieved via the formation of a solid lubrication film on the ceramic pin. It contains H3BO3, SiO2·nH2O, Mg(OH)2, and HXLPE wear debris (-CH2CH2-)n. In comparison, the effects of contact load and velocity on the tribological performance of Si3N4/HXLPE bearing couple are similar to that of Si3N4–20 vol% hBN/HXLPE bearing couple. However, poor quality solid lubrication films (e.g. discontinuity, rough, and uneven appearances) were observed, this may cause by the lack of hBN compound to promote the formation of H3BO3.