Electrodeposition of Ni-Fe/Bn nano-composite coatings from a non-aqueous bath and their characterization

Abstract

Ni-Fe alloy matrix nano-composite coatings containing uniformly dispersed 24 wt% BN (boron nitride) particles (micron-sized) were electrolytically codeposited under direct current condition from a non-aqueous sulfamate-ferrous sulphate-dimethylformamide bath. Effect of various deposition parameters like Fe++ ion concentration, current density, temperature, stirring rate, etc. on the composition and properties of the electrodeposits was studied and optimum condition for maximum incorporation of BN particles was determined. The composite coatings thus obtained were characterized by XRD, SEM, EDAX, DSC and spectrophotometric analyses. The iron content in the alloy deposits varied between 7-25 wt%. The deposition of alloy matrix showed anomalous behaviour and was found under charge transfer and diffusion control. The calculated crystallite size of the composite deposits was found between 4-13 nm while the calculated strain in the composite coatings ranged 0.017-0.02. All the composite coatings showed fcc structure with preferred orientation in <111> crystallographic direction. The lattice parameter of the composite coatings was found to be slightly larger than that of pure nickel. Hardness of as deposited and heat treated nano-composite coatings was found to be significantly higher than that of the parent Ni-Fe alloy. A correlation between crystallite size and strain with hardness has been worked out. The hydrogen content analysis of the composites showed almost minimal hydrogen inclusion (~ 1-2 ppm) in the deposits. © 2013 by ESG.