Electrodeposition and structural characteristics of intermetallic nickel-tin based coatings

Ni-Sn alloy intermetallic coatings with different Sn contents, were electrodeposited on Vanadis 23 steel substrates. Structural and chemical characterisation of these coatings was performed by x-ray diffraction, scanning electron microscopy and electron dispersive x-ray analysis. The as-plated Ni-Sn coatings were found to consist of a crystalline Ni solid solution with dispersed Ni-Sn intermetallic phases, whereas in certain cases bulk intermetallic coatings were obtained. The addition of Sn as an alloying element into electrolytic Ni coatings led to a significant increase of hardness and Young's modulus of these coatings. In addition, the effect of a post-deposition heat treatment at 400°C for 1 h on the microstructure and mechanical characteristics of these electrolytic Ni-Sn alloy coatings was investigated.