Electroless nickel-boron coatings on metal carbides

Electroless deposition is a very simple process which can be used to obtain amorphous metallic coatings of uniform thickness on metallic or non-metallic substrates. In this work, nickel-boron coatings were deposited by electroless plating on WC and VC powders and sintered substrates. Two electrolyte solutions for the deposition of Ni-B coatings were developed: an alkaline and an acidic bath, both based on nickel chloride. Coating characterization was carried out by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Auger electron spectroscopy (AES) and X-ray diffraction (XRD). Both electrolytes produced continuous films of uniform thickness on sintered carbide substrates; the acidic bath showed a higher deposition rate. Furthermore on the carbide powders it produced crack-free Ni-B continuous coatings. Ni was detected by EDS and the coating purity was confirmed by AES. XRD proved that amorphous coatings were obtained in all cases.