Structure and properties of pulse electrodeposited Cr–WC coating

Pure Cr and Cr–WC coatings are electrodeposited by both direct current (DC) and pulse current (PC) methods. The deposition was carried out with different (0, 3 and 5 kHz) pulse frequencies with varying nano-sized tungsten carbide (WC) loading (0, 3, 5 and 7 g l⁻¹) of the electrolytic bath. X-ray diffraction (XRD) results of the coatings display Cr coating with BCC structure along with minor WC peak after the enlargement of the peaks. Scanning electron microscope (SEM) images depict uniform and finer morphology for the coatings prepared at 3 kHz pulsing conditions. However, the coatings prepared at 5 kHz pulse show non-uniform coarse morphology. All the coatings display low surface roughness i.e. <1 μm. The hardness result of the coatings was mainly depended on WC incorporation. The Cr–WC coatings show excellent tribological properties, unlike pure Cr coating. After analysis of all the properties, it is observed that Cr-5 g l⁻¹ WC (3 kHz) shows optimum properties in terms of coating morphology, hardness, and wear behavior. (paper)