Water Lubrication of Ni/Al2O3 Composite Coatings Sliding With Si3N4

Abstract

Abstract Inspired by the excellent water lubrication properties of Al2O3, two methods are used to fabricate Ni/Al2O3 composite coatings for water lubrication. One is the conventional composite electroplating technique (one-step process). The other is depositing the Al2O3 particles layer on a substrate by electrophoresis firstly and then plating of Ni (two-step process). The morphology of surface and cross section, composition, micro-hardness, and bonding strength of the coatings were investigated. The water lubrication properties of the coatings sliding with Si3N4 were tested and compared. The result shows that the electrophoresis combined with electroplating is an efficient way to improve the Al2O3 particles content in the coatings. With the increasing of the particle content, the coating hardness increases while the bonding strength decreases. More importantly, low friction coefficient can only be achieved for Ni/Al2O3 coating with higher particle content. The comprehensive tribo-chemical reactions of Al2O3 and Si3N4 with water could be the dominated reason. The finds evidence the benefits of the ceramic-based composite coating design for water lubrication.