Effect of alumina content on wear behaviour of Ni-P-Al2O3(α) electroless composite coatings

Codeposition of alumina particles within a Ni-P matrix was investigated. These composite coatings were produced on AISI 1045 steel discs by an electroless process and then heat treated at 200, 400 and 600 degrees C for 1 h. Wear resistance of the deposits was measured by the pin on disc method. Structural changes were evaluated by X-ray diffraction (XRD) analysis, and SEM was used to study the surface morphology, cross-sections of coatings, wear surfaces and debris. The volume of codeposited particles was determined using an image analysis system. The results showed that alumina content in the bath to 15 g L-1 led to an increase in both the hardness and the wear resistance of the coatings. It was also found that heat treatment at about 400 degrees C can increase the hardness and wear resistance of these composite coatings to maximum values.