Tribological Reaction Generated on Ceramic – Steel Couples Under Boundary Lubrication

The effect of ZnDTP on Al₂O₃, Si₃C, and Si₃N₄ surface was investigated with ceramic-steel couples under lubricated conditions. Metal transfer to the ceramic surfaces was found to increase with load and surface roughness, depending on the kind of ceramic. P, S, and Zn as atomic constituent elements of ZnDTP were measured on the ceramic surface in all three types of ceramic-steel couple. The amount of each of these elements deposited increased as the Fe content transferred onto the surfaces increased. Measurements of hardness and fracture toughness were conducted on SiC and Si₃N₄ in SiC - and Si₃N₄-steel couples with and without additive to determine changes in mechanical properties of the ceramic surfaces. Further investigations were conducted to determine the effect of the gases, O₂ and N₂, on friction and wear properties of the Si₃N₄-steel couple. Saturation of the lubricant oil with O₂ and N₂ was found to cause an increase of the wear rate at about 100 N in this couple.