Microstructure and properties of self-lubricating Cu-NiP-C coatings produced by high-pressure cold spray

The microstructure and functional properties of self-lubricating copper-matrix coatings deposited on a copper substrate by high-pressure cold spray were studied. Thick coatings were obtained by spraying mixtures of Cu and NiP-cladded graphite powders with contents of 31, 43 and 54 vol%. The fabricated coatings were characterized by SEM , EDS , XRD , Vickers and instrumental indentation, dry friction tests and eddy current technique. The embedment of cladded particles resulted in the formation of a lamellar coating structure containing microdefects along the inter-splat boundaries of copper matrix. The phase composition of the coatings was unchanged compared to the feedstock powders, but an increase in the Cu crystallite size was found after spraying. Increasing the content of NiP-C in the coating resulted in a monotonic growth in coating hardness , reduction in elastic modulus and specific electrical conductivity . Despite lower coefficients of friction , the specific wear rate of the composite coatings was higher compared to pure copper coatings, which was explained by differences in wear mechanisms. With the increase in the content of NiP-C, a change in wear mechanism from oxidative wear and plastic deformation to delamination and then to abrasive wear was detected. • Cu-matrix coatings with different NiP-graphite content were obtained by cold spray. • Effect of plated graphite on microstructure and properties of coatings was studied. • Hardening and self-lubricating effects for composite coatings were demonstrated. • Presence of 14 vol% NiP-graphite in coating showed attractive set of properties.