Electroless Ni–Al2O3–WS2 Composite Coating on Aluminum Substrate

The purpose of this study is to deposit a layer of Ni–P and Ni–Al2O3–WS2 composite coating by varying the concentration of Al2O3 and WS2 nano-powders in the Ni–P plating bath. A comparative study has been carried out by adding nano-powders into the Ni–P bath and without the use of powders. The addition of powder in the bath yields certain desirous properties to the substrate surface that finds industrial applications. The mechanical properties and surface characteristics are enhanced by varying the powder concentration in the electroless Ni–P plating bath. To analyze the elements present in the coated layers and study the surface morphology, FESEM along with EDX has been used. In addition to that, the intermetallic compounds have been identified by using XRD. The micro-hardness of the coated samples without addition of powder is seen to be improved (789.02 HV) when compared to that of the substrate (76.68 HV). However, adding the nano-powders in the bath shows fluctuation in micro-hardness ranging from 476.37 to 1286.58 HV. It is probably due to the dispersion hardening effect of both the powders into the substrate material. Although the maximum coating thickness is obtained with 3 g/L Al2O3 and 1.4 g/L WS2 powder concentration, uniform thickness is seen at 4 g/L Al2O3 and 1.4 g/L WS2. The surface morphological study is carried out through FESEM images.