Tribological Evaluation of Silicon Nitride Against Retainer Materials

Sliding wear tests were conducted with silicon nitride (Si₃N₄) against five retainer materials using different lubricants. The sliding wear tests were conducted with the Torrington Tribology tester at three normal loads and one sliding speed at an ambient lubricant oil temperature and one hour duration. The retainer materials were polyetheretherketone (PEEK) with glass fill, PEEK with carbon graphite/PTFE (polytetrafluoroethylene) fill, machined aluminum with a WS₂ coating, machined steel with a silver plating, and machined bronze. The Si₃N₄ ceramic specimens (both NBD-100 and NBD-200) did not experience any measurable or observable wear. Friction coefficients varied between 0.03 and 0.16 depending upon the retainer material and the lubricant; the lowest values were obtained with the PEEK materials. Large wear scars were generated on the machined bronze, along with high friction coefficients and slip-stick behavior. Similar slip-stick frictional behavior occurred with the coated aluminum specimens when the WS₂ coating wore off the wear track. Slip-stick behavior was not observed in the frictional traces with the PEEK specimens and wear scars were not measurable.

The silver plating experienced a polishing wear, although it did not wear off the steel.