A functionally gradient nano-Ni–Co/SiC composite coating on aluminum and its tribological properties

Functionally graded (FG) nano-structured Ni–Co/SiC coating was electrodeposited on an aluminum substrate. The mechanical properties of this coating compared with those of uniform Ni–Co/SiC and FG Ni/SiC coatings. The crystallographic texture and surface morphology of the coatings were studied by means of X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Hardness, adhesion strength and wear resistance of coatings were also measured. The results indicated that FG Ni–Co/SiC coating showed lower friction coefficient and wear rate than FG Ni/SiC. It was due to the role of cobalt in refining microstructure and increasing SiC content into coating. In addition, FG Ni–Co/SiC coatings exhibited higher adhesion strength and wear resistance compared to those of the uniform coatings. Under wear load FG Ni–Co/SiC coating showed excellent wear resistance while uniform coatings failed due to large wear loss or delamination of coatings from substrate.