Effect of micro-texture on substrate surface on adhesion performance of electroless Ni-P coating

Fabricating textured substrate surfaces is an effective way to improve adhesion at a coating-substrate interface. In this study, the radial ultrasonic vibration assisted turning (RUVT) technique is proposed for the fabrication of complex micro-textures on substrate surfaces before they are coated. Electroless Ni-P coatings were deposited on substrates with various texture densities and their surface and cross section morphologies were characterized. The bonding properties of the prepared coatings were investigated and compared by scratching and three-point bending tests. The test results confirm that the coating adhesion was improved by the prepared micro-textures. The mechanism involves two aspects: mechanical anchoring at the coating interface and substrate surface wettability. As a result, the complex micro-textures formed by RUVT facilitate bonding between a Ni-P coating and stainless-steel substrate. Therefore, the RUVT technique is a convenient and controllable way to prepare micro-textures without the risk of thermal damage and warrants further exploration.