The lubricated wear of ceramics .1. The wear and friction of silicon nitride, alumina and steel in the presence of a mineral oil based lubricant

The friction and wear characteristics of combinations of silicon nitride, alumina and AISI 52100 steel in the presence of mineral oil containing anti-wear, dispersant and detergent additives have been investigated in a tri-pin-on-disc machine. The tests were carried out at a nominal temperature of 100 degrees C for a range of sliding speeds, loads and total sliding distances. In Part II of this two-part paper a comparison will be made between the tribological performance of these sliding pairs of materials in mineral oil and ester based lubricant environments. The results of the investigation showed that the alumina performed relatively poorly under these test conditions, whereas silicon nitride showed good potential as an improved wear resisting material compared with 52100 steel. Wear factors of the order of 10(-10) mm(3)/Nm were deduced for the alumina, while values as low as 10(-11) mm(3)/Nm were typical of the silicon nitride sliding against 52100 steel discs. The alumina pins wore by a process of brittle fracture at the surface, whereas the silicon nitride pins wore primarily by a tribo-chemical polishing mechanism. The rate of tribo-chemical wear was found to be proportional to the nominal contact area.