Improvement of wear and corrosion resistance of AZ91 magnesium alloy by applying Ni–SiC nanocomposite coating via pulse electrodeposition

Abstract

To improve the surface properties of AZ91 magnesium alloy, Ni–SiC nanocomposite coatings with various SiC contents were pulse electrodeposited in modified Watts baths containing SiC nano-particles with the concentration of 0–15 g/L. The morphology of the coatings was studied by scanning electron microscope (SEM). The SiC content of the coatings was measured by energy dispersive spectroscopy (EDS) analyzer. Microhardness measurement of the coatings showed up to 600% enhancement for the sample produced from the bath with 15 g/L SiC. The corrosion behavior of the coated AZ91 alloy was investigated by potentiodynamic polarization method. The results reveal a significant improvement in the corrosion resistance, that is, the corrosion current density decreases from 0.13 mA/cm2 for uncoated specimen to 1.74×10−6 mA/cm2 for the sample coated from the bath containing 15 g/L SiC and the corrosion potential increases from −1.6 V for uncoated specimen to −0.31 V for the sample coated from the bath. The wear resistance of both coated and uncoated samples was evaluated by pin-on-disc tribotester. The results show that the wear volume loss of coated sample is 8 times less than the bare alloy.