High temperature plasma nitriding to modify Ti coated C17200 Cu surface: Microstructure and tribological properties

In this work, we studied the microstructure formation and mechanical properties of the Ti alloyed C17200 Cu surface produced by plasma nitriding at 750 °C. The results firstly show that the multiphase coating consists of amorphous and nano-crystalline phases, and various types of Cu-Ti intermetallics, including CuTi₂, CuTi, Cu₃Ti₂, Be₃Ti₂Cu, Cu₂Ti, Cu₃Ti, formed after the plasma nitriding at 750 °C. The formation of the specific type of Cu-Ti intermetallic depends on the processing duration, where a longer duration contributes to the formation of intermetallics with a higher Cu/Ti ratio. The evolution of the phase compositions is responsible for the change in the mechanical properties. The surface hardness of the modified C17200 Cu alloy improves to be 400 HV_0.01 to a depth of 15 μm after plasma nitriding for 6 h, which contributes to a higher surface tribological resistance with a friction coefficient of 0.3 and a wear rate of 4.15 × 10⁻⁹ g/(r·N) for the modified suface.