Effect of alkali cleaning for Ni-P-based metallic glass coating on bearing surface

A systematic alkali cleaning study has been done on the different bearing component surfaces for subsequent Ni-P alloy coating. The alkali-chemical containing only carbonate and phosphate group shows better surface cleaning efficiency. There is a tendency of silica contamination when silicate containing alkali chemical is used, which is responsible for inferior quality of Ni-P alloy coating on the surface of bearing components. The use of ultrasonic energy further enhances alkali cleaning efficiency and thereby reduces the cleaning time with better properties. Amorphous Ni-P alloy coating is uniformly deposited on the surface of the bearing component. After coating, the surface roughness value drops from 0.05 to 0.025 mu m and the hardness value increases from 60 to 63 Rc. The Ni-P alloycoated bearing shows 250 to 350% improvement in resistance against corrosion, around 58% reduction in noise level and improvement in L10 life from 500 h of existing bearing to 1200 h.