The present study investigates optimisation of microhardness of electroless Ni-Co-P alloy coating over copper substrate. The microhardness of the coating was significantly higher compared to the substrate. Three different design factors i.e., the concentration of cobalt sulphate, concentration of sodium hypophosphite and bath temperatures were used as the process parameters which were optimised by using Box Behnken Design (BBD) and coating micro hardness was taken as a response factor. Vickers' hardness test was conducted to obtain the micro hardness values of the coated samples. From the model analysis results, it was found 15 g/L of cobalt sulphate, 25 g/L of sodium hypophosphite and a bath temperature of 85 °C were the optimum conditions for the coating deposition in order to obtain the hardness value of 1921 HV10g. After annealing at 350 °C the hardness value was further enhanced to 1990 HV10g. Analysis of variance (ANOVA) was carried out to find the graphical relationship between the different process parameters. The detail surface morphology of the Ni-Co-P coating was studied by using an optical microscope and a Scanning Electron Microscope (SEM). The phase and elemental compositions were determined by X-Ray Diffraction (XRD) analysis and Energy Dispersive X-Ray analysis (EDX).

The current study focuses on the parametric optimization of electroless Ni-Co-P coating considering surface roughness as a response using Box-Behnken Design (BBD) of experiment. The two bath parameters namely the concentration of cobalt sulphate and sodium hypophosphite were varied along with the bath temperature to predict the variation in surface roughness. Analysis of variance (ANOVA) method has been applied to determine the interactions of the substantial factors which dominate the surface roughness of the coating. The process parameters for surface roughness of the coating were optimized by successfully utilizing the statistical model of Box-Behnken Design (BBD) of experiment. From the BBD model, the optimum condition for the deposition of the coating has been evaluated. In that specific condition, the surface roughness of the as-deposited coating is found to be 0.913μm. Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and X-Ray Diffraction (XRD) study have been utilized to characterize the electroless Ni-Co-P coating deposited in optimized condition.

The present work deals with the synthesis of chemically deposited nickel–phosphorous (Ni–P) coating on copper substrate. The process parameters are optimized for maximum hardness based on L[Formula: see text] Taguchi orthogonal design with three process parameters, viz., bath temperature, concentration of nickel Sulphate (a nickel source) and concentration of sodium hypophosphite (a reducing agent), respectively. This is considered and fitted into an L[Formula: see text] orthogonal array (OA) to find out the optimized condition for improved hardness of the coating. The optimized results were obtained from 35[Formula: see text]g/L of Nickel Sulphate, 20[Formula: see text]g/L of Sodium Hypophosphite and 90∘C of temperature. Analysis of variance (ANOVA) was performed to determine the significance of the individual process parameters. ANOVA showed that the factor Nickel Sulphate, the interaction between Sodium Hypophosphite and Temperature were significant in determining the hardness of the coating deposited in the optimized condition. The surface morphology, compositional and phase structure analysis of optimized sample are conducted with the help of scanning electron microscope (SEM), energy-dispersive X-ray analysis and X-ray diffraction (XRD) analyzer, respectively.

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