Effect of electrodeposition conditions on properties of Ni–Al composite coatings

Ni–Al composite coatings were prepared on 6061 Al alloy by pulse electrodeposition from a modified Watts bath containing suspended Al particles. The effect of surfactant and Al concentrations as well as electrodeposition parameters on composition, crystallographic texture, microhardness, adhesion strength and wear resistance of the coatings was investigated. The results indicated that addition of surfactant up to 0·25 g L⁻¹ increased the amount of codeposited Al particles in nickel matrix. The incorporation of Al particles changed the preferred crystallographic orientation of the coating from (200) to (111). By increasing the current density and duty cycle, the amount of Al particles embedded in Ni matrix decreased and, therefore, the adhesion strength of the coating was improved whereas its microhardness reduced. Meanwhile, codeposition of Al particles increased the wear rate of composite coating with respect to pure nickel one. In other words Ni–Al coating is not suitable for wear resistant applications.