Modelling and Optimization Study on Hardness of Ni-Fe Alloy Thin Films through Electroplating Process

The hardness of the coated surfaces by nickel-iron electroplating process is closely linked to the characteristics of deposited layer. These characteristics depend on various process variables, such as current density, temperature, pH and stirring. This work presents the modelling and the optimization of nickel-iron electroplating process variables to maximize the surface hardness. To study the combined effect of current density J (A/dm2), temperature T (°C) and pH were used a 23 orthogonal central composite experimental design for experiments design and Response Surface Methodology for analysis of experimental results. The modelling was performed using the following intervals for process variables: 1.75 - 3.51 A/dm2 for current density, 25-35 °C for temperature and 2.5-3.5 for pH. The empirical model was further used in the optimization process using the Gradient method. The optimum values of these electroplating process variables were found to be J = 2.23 A/dm2, T = 30.80°C and pH = 2.81; in this point the surface hardness is 136.89 HV given by empirical model and 137.52 confirmed experimentally.