SILICON-NITRIDE BOUNDARY LUBRICATION - EFFECT OF PHOSPHORUS-CONTAINING ORGANIC-COMPOUNDS

The boundary lubricating characteristics of phosphorus-containing comp ounds on silicon nitride were studied using a ball-on-three-flat wear tester. ?Xe compounds were tested at I % by weight in a pure paraffin oil under a mean pressure of about 2 GPa. The compounds are effective in reducing wear. Continuous surface films were observed in and around the wear scars for most of the phosphorus compounds. These films are complex mixtures containing phosphorus and silicon. A detailed study o n a zinc dithiophosphate (ZDP) surface film revealed high concentratio ns of zinc and phosphorus, but very little sulfur. This is in direct c ontrast to surface analysis results on steel systems in which sulfur-c ontaining species are found on the worn surface. This suggests differe nt chemical reaction, pathways for phosphorus compounds on steel and s ilicon nitride surfaces.