Microstructure and third-body behavior of Cu-MoS₂-TiC composite coatings deposited by cold spray

To investigate the effect of ceramic particle addition on the properties of cold sprayed MoS₂-based metal matrix composite coatings, Cu-MoS₂ and Cu-MoS₂-TiC coatings were deposited using feedstocks containing 0 (CM), 15 (CM-15T), 30 (CM-30T) and 50 (CM-50T) wt% TiC, respectively, while maintaining a constant MoS₂ ratio of 5.5 wt% relative to the combined Cu and MoS₂ powders. The influence of TiC content on the coatings microstructure and mechanical properties was systematically evaluated. TiC addition led to a tamping effect that densified the coatings and enhanced plastic deformation of the Cu matrix, thereby improving cohesion strength as well as nano- and micro-hardness. However, MoS₂ retention decreased in CM-30T and CM-50T. Polished coating surfaces were tested for reciprocating sliding wear using a ball-on-plate tribometer in dry air and nitrogen, with Al₂O₃ spheres as counterbodies. CM showed low coefficients of friction but the highest wear rate in both environments because of its inferior mechanical properties. In dry air, CM-15T demonstrated the lowest friction and superior wear resistance, attributed to its high MoS₂ retention and improved mechanical properties. Mild abrasive wear in CM-15T suggested a significant reduction in adhesive wear which was dominant for the other coatings. In nitrogen, adhesive wear was minimal for all coatings. The high MoS₂ content in CM-15T contributed to low coefficients of friction. CM-50T exhibited the lowest wear rate, benefiting from its high hardness, enhanced cohesion strength, and more retained TiC particles that facilitated the fast formation of hard tribo-layers. These findings highlight the interplay between tribological behavior, mechanical properties, tribo-oxidation, and third-body effects in metal matrix composite coatings incorporating solid lubricants and hard phases.