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).