Combining thermo-diffusing titanium and plasma nitriding to modify C61900 Cu–Al alloy

• Multi-phases coating on C61900 copper alloy was successfully fabricated by thermo-diffusing and plasma nitriding.
• Surface hardness and wear resistance of Cu–Al alloy were obviously improved.
• Surface worn mechanism transferred to be oxidation and abrasive wear against GCr15.

To improve the mechanical properties of C61900 copper–aluminum alloy, a multi-phases coating was fabricated by the combination of thermo-diffusing Ti film and plasma nitriding. The results showed that a smooth coating with fine and uniform grains could be achieved, and the 9 μm thick multi-phases coating, containing Ti–Cu–Al intermetallics (CuTi2, CuTi, AlCu2Ti) and titanium nitride (Ti2N) formed on the nitrided surfaces. The surface hardness of the coating was obviously improved to be 630 HV0.01, and the cross-sectional hardness decreased gradually to that of C61900 Cu–Al alloy. Moreover, the wear rate of the coated specimen decreased significantly, dropping 95.5% compared with the untreated Cu–Al alloy.