Effect of Concentration of Clad Graphite Particles on Tribological Properties of Cold-Sprayed Copper-Matrix Coatings

The structure and tribological properties of self-lubricating Cu – NiP – C coatings deposited on copper substrates by high-pressure cold gas-dynamic spraying are investigated. The coatings are obtained by spraying mixtures of copper and clad graphite powders in an amount of 20, 30 and 40 wt.%. The incorporation of clad particles leads to formation of a lamellar structure and microdefects along the inter-splat boundaries of the copper matrix. Increase in the content of clad particles in the coating causes monotonic growth in its hardness due to shot peening and increases the content of the NiP alloy. Despite the reduction of the coefficient of friction, the wear rate of the composite coatings increases as compared to the pure copper coating. With the increase in the content of clad graphite, the wear mechanism changes from oxidative wear and plastic deformation to delamination and then to abrasive wear.