Experiments design for hardness optimization of the ni-cr alloy electrodeposited by pulse plating

The hardness of the Ni-Cr alloy which is electrodeposited in chloride solution, is optimized by design of experiment method (central composite design). Various parameters were evaluated in order to find significant factors in this process. Frequency, duty cycle, current density and temperature were selected as effective factors. Analyses of variance (ANOVA) were performed on the results of the designed experiments. The best model which can predict the hardness of the Ni-Cr alloy electrodeposits was found whereas the frequency and quadratic behaviour of the current density were the most significant model terms. Serious interaction of the current density with frequency and duty cycle also were found in this model. Finally the optimum conditions of the factors for obtaining the maximum hardness of the Ni-Cr alloy were found. Ni-Cr alloy with hardness 828 HV (electrodeposited with frequency 63 Hz, current density 1800 A/m2, duty cycle 75% and temperature 31 °C bath) were assessed as the optimum deposit. The deposit under the optimum condition was investigated by scanning electron microscopy (SEM), EDX analysis, polarization method and microhardness.