Preparation and Tribological Properties of Copper-Based Composites Reinforced with Dual Phases of Cu-Coated Ti₃SiC₂ and Graphite

In this study, electroless plating was used to deposit a Cu layer on the surfaces of graphite and titanium silicon carbide (Ti₃SiC₂) particles to improve their interfacial bonding strength with the Cu matrix. Furthermore, copper-based composite materials reinforced with either copper-coated graphite or copper-coated Ti₃SiC₂, either singly or in combination, were prepared by ball milling, cold pressing and hot pressed sintering. The organization structure, physical mechanical properties, and tribological properties of the composite materials were studied. It was found that the copper-based composites reinforced with Cu-coated graphite exhibited the lowest friction coefficient (0.26), but their physical and mechanical properties and wear resistance 1.86×10⁻⁶ cm³/(N·m) were poor. Cu-coated Ti₃SiC₂ could significantly improve the composites’ physical and mechanical properties as well as wear resistance 0.88×10⁻⁶ cm³/(N·m), while the decrease in friction coefficient (0.49) was not significant. The copper-based composites reinforced with dual phases of Cu-coated Ti₃SiC₂ and graphite exhibited excellent physical and mechanical properties, friction reducing and wear resistance performances. In addition, it was found that research had found that overly large graphite sizes could adversely affect the local uniformity of the material, leading to internal damage within the graphite during testing and subsequently reducing the physical and mechanical properties of the material. In friction tests, the use of smaller graphite sizes (40 μm) enhanced the uniformity of the friction material structure, facilitating the even distribution of graphite from the matrix to the friction contact surface, thereby improving the tribological properties of the material. Conversely, larger graphite sizes were prone to flaking during the friction process, leading to three-body wear, which increased the friction coefficient and wear rate. Composite materials reinforced with 40 μm copper-coated graphite and Ti₃SiC₂ exhibited superior physical and mechanical properties, with the lowest friction coefficient (0.35) and wear rate 0.54×10⁻⁶ cm³/(N·m). During the friction process, graphite, due to its special lamellar structure, adhered easily to the worn surface, providing lubrication, while Ti₃SiC₂ oxidizes and decomposes to form a Ti-Si oxide film, thereby reducing friction. The friction performance of the sample largely depended on the coverage of its lubricating film on the friction surface. When the load too low, it's difficult for the sample surface to form a dense and continuous lubricating film. Under the friction conditions of 80 N and 800 r/min, the copper-coated Ti₃SiC₂ lubricant was sufficiently enriched on the worn surface and fully oxidized, together with graphite, to form a smooth and well-dense lubricating film, thus exhibiting excellent anti-friction and anti-wear properties. However, when the load and speed were too high, the friction film was destroyed and cannot be replenished, resulting in a sharp increase in the friction coefficient and wear rate of the sample.