Combined solid and liquid lubrication of silicon nitride under boundary conditions

The present study showed that an effective way of lubricating ceramic surfaces under boundary conditions both at room temperature and at high temperatures of 150 degreesC and 250 degreesC was the combined effect of solid, ie soft metal-Ag, and liquid lubricants, ie polyol-ester-based synthetic oil. Compared to dry sliding of uncoated materials, oil-lubricated sliding of silver-coated silicon nitride surface resulted, for the conditions tested, in a decrease of the friction coefficient by a factor of 18 (0.9 vs 0.05) and of specific wear rate by more than four orders of magnitude (10 "SUP 7" vs 10 "SUP -7" mm "SUP 3" /N.m). The only observed drawback was the occurrence of a chemical interaction between the Ag film and sulfur from the oil, which reduced the durability of the Ag film. (from Authors)