Abstract: Tribological properties of plasma-sprayed self-mated Cr₃C₂-NiCr, WC-Co and Cr₂O₃ coatings and the Cr₂O₃ coating against WC+Co hard alloy and toughened SiC ceramics were investigated under water-lubricated sliding. It was found that
Cr₂O₃ coating was the most wear-resistant among the three kinds of self-mated coatings and had a wear coefficient less than
10^-6mm³N^-1m^-1. Wear mechanisms of the coatings were explained in terms of microcracking and grain fracturing. The higher the fracture toughness, and the lower the porosity and the length of microcrack of the coating, the more wear-resistant the
coating was. The friction coefficient and wear coefficient of Cr₂O₃ coating were obviously reduced when it was mated to WC+Co hard alloy and toughened SiC ceramics, which may be related to surface condition and tribochemical reaction of material of friction pair.

Key words: plasma spraying, Cr₃C₂-NiCr, WC-Co, Cr₂O₃ coating, distilled water lubrication, tribological property