Sliding wear characteristics of plasma-sprayed Cr2O3 coatings with incorporation of metals and ceramics

Different additives (metals, ceramics, and metal/ceramic assembles) were incorporated into chromium oxide (Cr2O3) coatings to improve its wear resistance. The doping or co-doping effects were compared in terms of the microstructure, phase composition, microhardness and sliding wear properties of plasma-sprayed Cr2O3-7wt.% Mo, Cr2O3-7wt.% Nb2O5, Cr2O3-4wt.% MoO3-3wt.% Mo, and Cr2O3-4wt.% Nb2O5-3wt.% Mo coatings. Under the low sliding loads, the composite coatings mated with WC-Co counterparts have lower friction coefficients than those against Si3N4, which are inverse with their microhardnesses, but more obvious fatigue wear characteristics. Under the high sliding loads, Mo/Nb2O5 co-doped Cr2O3 coating (CNM) has the best wear resistance than other coatings, due to the delaying co-effects of crack formation and propagation on basis of the crack deflection and the toughening effects of Mo additives and the high hardness of Nb2O5 additives. As the reciprocating sliding loads exceed the critical stress of brittle Cr2O3-based coatings, the coating detachments occur, displaying obvious fatigue wear characteristics.