Study on morphology, wear and corrosion resistance of ultrasonic-assisted pulse co-electrodeposited B4C reinforced Ni–P composite coating

The B₄C-reinforced Ni–P composite coatings were synthesized on low-carbon steel via ultrasonic-assisted electrodeposition. The optimal condition for producing co-electrodeposited Ni–P coating is to investigate the effects of concentrations of B₄C on the morphology, microstructure, surface roughness, hardness, elastic modulus, friction, wear, and electrochemical properties of the composite coating. Field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and energy dispersive spectrometer (EDS) were used to analyze the surface microstructure, crystallite size, morphology and composition of coating and content and distribution of the particles. The nanohardness and reduced elastic modulus of B₄C-reinforced Ni–P depositions was characterized by the nanoindentation technique. The friction and wear mechanism of the composite coatings was discussed in detail. The electrochemical properties of samples were studied via open circuit potential (OCP), potentiodynamic test and electrochemical impedance spectroscopy (EIS) in the 3.5% NaCl media. The experimental results indicated the highest elastic modulus and nano hardness (147 GPa and 6,92 GPa and the lowest wear rate (3.18 X 10^–8 mm³ /Nm) and average coefficient of friction (0,35) for coatings deposited at 20 gL⁻¹. Moreover, the corrosion resistance is significantly improved; this is shown via the low corrosion current density (I_corr value of 1.48 × 10^–3 A/cm²), the high corrosion potential (E_corr value of – 0.56 V), best corrosion rate (1.36 X10⁻⁵ mpy) and maximum R_ct of 181.8 kΩ cm². These results are attributed to the uniform distribution of the B₄C into nickel coating and the grain refinement effect of electrodeposited Ni–P coating. The formation of the B₄C core–shell structure on the coating surface improved the interfacial bond between the matrix and the ceramic particle, improving wear resistance and anti-corrosion performance.