Influence of deposition temperature and heat treatment on the performance of electroless Ni-B films

Electroless nickel-boron (Ni-B) was synthesized on mild steel or copper surface. The deposition of thin electroless Ni-B films using an acidic bath having nickel chloride as a source of nickel and dimethylamine borane (DMAB) as a reducing agent and operated at low temperature has been investigated in this paper. The effect of the plating time and temperature on the quality of Ni-B coatings was estimated. The results revealed that the plating rate decreases with increasing plating time and increases with increasing plating temperatures. The boron (B) content of the electroless Ni-B layer increased with increasing temperature. The resulting surfaces were examined and characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). XRD analysis was performed to investigate structural modifications. Microhardness, corrosion and oxidation resistance of electroless as-plated and heat-treated Ni-B coatings, were evaluated. The effect of heat treatment temperature on the phase structure and microhardness of Ni-B coated at different temperatures was discussed. XRD patterns reveal that electroless Ni-B coatings deposited at 60 and 80 °C are amorphous in as-plated condition and undergo phase transformation to crystalline nickel and nickel borides upon heat-treatment. Heat treatment achieved significant improvement in the microhardness and corrosion resistance due to the formation of the Ni-B compound phases (Ni3B).