Optimization of electrodeposited Co–Ag coatings microhardness using Taguchi and ANOVA methods

Abstract

Co–Ag coatings have been prepared by potentiostatic deposition method from a mixed sulfate chloride bath on a Cu substrate. The cyclic voltammetry (CV) results confirm the reduction of Ag and Co ions. The SEM-EDX analyses prove the formation of Co–Ag coatings with compact and uniform surface. The XRD results reveal the presence of FCC-Ag and HCP-CoAg3 phases. The effects of the experimental parameters ([Co2+]/[Ag+] molar ratio (R), deposition potential (P) and deposition time (t)) on the electrodeposited Co–Ag coatings microhardness (HV) has been investigated using the Taguchi experimental design method based on an orthogonal array (OA) L27(313). Statistical signal-to-noise (S/N) results indicate that the optimal coatings parameters combination corresponding to the maximum of microhardness is P1R3t3 (P = 0.6 V, R = 15, t = 20 min). The coatings microhardness is influenced by R and P factors at a confidence level of 95%. According to the ANOVA results, R and P factors are the most influencing parameters with a contribution of 32.94% and 32.92% respectively, while the individual t factor is insignificant. The parameters interactions P × R and P × t are found to be significant with 17.77% and 9.18% respectively. At the optimum level, the microhardness is improved at 25% as compared to the initial conditions. A linear-interaction model for microhardness was developed and shows a high correlation between the experimental and the predicted microhardness values. The obtained results show that 97.8% of the total variations can be explained by the model with 95% confidence interval.