Multicriteria optimization of mechanical and morphological properties of chromium electrodeposits under reverse pulse plating

In this work, a central composite design experiment was performed to estimate the effect of the electroplating parameters (temperature of electrolyte, cathodic and anodic pulse current densities, and cathodic and anodic pulse lengths,) on four properties of hard chromium electrodeposits. The studied responses were the hardness (Hv), the roughness quantified by the two criteria R_a (nm) and R (μm)), and the specific abrasive energy, E_s (μJ μm⁻³). Analysis of the responses using optimal path technique did not lead to a common set of experimental conditions which fulfilled the required properties. Thus, the desirability function approach has been employed in order to find the best compromise between the different experimental responses. The optimal conditions are: electrolyte temperature: 49.9 °C; cathodic pulse current density: 42.0 A dm⁻²; anodic pulse current density: 51.5 A dm⁻², cathodic pulse length: 6.23 s and anodic pulse length: 28.5 ms. Under these conditions, the estimated response values are 738 Hv, 262 nm, 2.61 μm and 0.027 μJ μm⁻³ for hardness, R_a, R and specific abrasive energy respectively, validated experimentally. The resultant coating, examined by AFM, exhibits a nodular fine-grained morphology.