Effect of Alumina Concentration on Morphology, Wear, and Corrosion: Electroless Ni-W-P/Al2O3 Composite Coatings on Aluminum Surfaces

Electroless nickel-based coatings are frequently used in the field of coatings to improve the surface properties of materials such as wear, hardness, and corrosion. In this study, Ni-W-P alloy and Ni-W-P/Al2O3 composites were coated on the aluminum substrate by electroless technique. Composite coatings were carried out after suspending process of alumina (Al2O3) particles at different concentrations in the electroless bath. The characterizations of the coatings were studied to be able to reach optimum particle concentration. Aluminum oxide particles (average particle size 300 nm) with different concentrations (5, 10, 15, 20 g/L) were added to the bath to determine the concentration effect. Scanning electron microscope (SEM) and field emission scanning electron microscopy (FESEM) analyses were performed to examine the microstructure images of the composite coatings. x-ray diffraction (XRD) analysis was performed to determine the coating layers' phase structures. The hardness of the coatings was determined by applying the hardness test on a microscopic scale. CSM tribometer was used to establish the wear and friction properties of the coatings. Galvanometer was used to determine corrosion resistance. After the studies, hardness values of coatings were successfully increased from 552 to 700 HV depending on the amount of particles in the coating layer. The friction coefficient was also improved by decreasing that from 0.45 to 0.1 mu grades with the contribution of Al2O3 particle reinforcement to Ni-W-P coating. The wear rate of the coatings decreased from 5.96 x 10(-5) to 3.16 x 10(-5) mm(3)/Nm) with the increase of Al2O3 particles in the composite coating which indicates approximately two times improvement in the wear resistance. The corrosion resistance of composite coatings also increased, and an improvement in corrosion rate was achieved from 392 value to 063 mu m/year value with increasing particle concentration.