Improved wear behaviors of lead-free electroless Ni B and Ni-B/CeO2 composite coatings

Abstract

NiB and Ni-B/CeO2 coatings were deposited by the electroless deposition method using a bath containing nickel sulfate hexahydrate, dimethylamine borane, and sodium acetate. Instead of lead and tantalum-based stabilizers, thiourea was used as the stabilizing agent for an environmentally friendly and cost-effective process. Different amounts of submicron CeO2 particles were used as reinforcement for composite coatings. The main aim is to investigate the effects of CeO2 particles on the structural properties, hardness, crystallite size, strain, and tribological behavior of coatings. Surface analysis of pure NiB and Ni-B/CeO2 composite coatings was performed by scanning electron microscope (SEM) device equipped with energy-dispersive spectroscopy (EDS) attachment. Cross-section examinations were carried out by field emission scanning electron microscopy (FESEM). Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to obtain the nickel and boron percentages in the coating. X-ray diffraction (XRD) was applied to analyze phase structures of the coatings, nanohardness measurements of coatings were performed by nanoindenter, and wear tests were performed with a ball-on-disc test device. Roughness measurements and worn surface analyses were performed using a 3D profilometer. Experimental results showed that the CeO2 particle concentration in the plating bath of 10 g/l is the optimum amount to provide a noticeable enhancement in hardness and wear resistance compared to the other composites.