Study on tribological behavior of electrodeposited Cu–Si3N4 composite coatings

• Cu–Si3N4 composite coatings were prepared using direct electroplating.
• Effects of current density and particle concentration were investigated.
• Effect of Si3N4 particles on the microstructure of the coatings was determined.
• Effect of Si3N4 particles on the mechanical properties of the coatings was studied.
• Cu–Si3N4 composite coatings presented improved wear resistance.

Cu–Si3N4 composite coatings were prepared by electrolysis from a copper sulphate solution containing dispersed Si3N4 particles of 0.4 or 1 μm mean size. Wear behavior of Cu–Si3N4 composite and pure copper coatings were evaluated using a pin-on-disc test machine under dry condition sliding. Effects of current density and particle concentration on the incorporation percentage of Si3N4, the preferred orientation of copper crystallites, the microstructure, the microhardness and the wear resistance of the coatings were determined. Si3N4 particles in the copper matrix resulted in the production of composite deposits with smaller grain sizes and led to change the preferred orientation growth from [1 0 0] to [1 1 0]. It was proved that the presence of Si3N4 particles decreases the wear loss and the friction coefficient of the coating. According to the results, the friction coefficient decreased dramatically from 0.52 to 0.26 for pure copper coatings to 0.16–0.24 for Cu–Si3N4 composite coatings. In addition, fluctuation of friction coefficient values for Cu–Si3N4 composite coating was lower compared with the pure copper coating. The wear properties of Cu–Si3N4 composite coatings were shown to depend on the weight fraction, the size and the distribution of co-deposited particles.