Microstructure and Properties of Copper-Coated Titanium Nitride Particle-Reinforced Copper Matrix Graphite Composites

In this paper, titanium nitride particles (TNPs) reinforced copper-matrix graphite composites were prepared by powder metallurgy, in which copper-coated (Cu-coated) graphite (2 wt %) was used as solid lubricating phase and uncoated/Cu-coated TNPs (0, 1, 3, 5, 10, 15 wt %) was used as reinforcing phase. The effects of uncoated/Cu-coated TNPs on microstructure, density, porosity and mechanical properties of composites were studied and compared. The strengthening and wear mechanism of uncoated/Cu-coated TNPs in copper-matrix graphite composites were investigated. The results showed that electroless copper plating on the surface of TNPs can effectively improve the wettability between TNPs and copper matrix. In composites reinforced by Cu-coated TNPs, TNPs have a better interface bonding state with the matrix. Under the same content of TNPs, composites reinforced by Cu-coated TNPs have lower porosity, wear, friction coefficient, higher hardness and compressive strength than those reinforced by uncoated TNPs. TNPs can effectively strengthen the friction surface of composites. In processes of friction, TNPs will form a titanium oxide protective film on friction surfaces, which makes composites exhibit better self-lubrication, thus reducing the peeling wear. Copper plating can effectively reduce spalling of TNPs and weaken the abrasive wear and exfoliation wear of composites. Considering wear and friction coefficient, composites containing 3 wt % Cu-coated TNPs, exhibited better friction and wear resistance properties.