Evaluation of Adhesion and Corrosion Resistance of Cr/CrN Multilayer Coatings Deposited on Nitrided AISI 4140 Steel

Abstract

CrN multilayer coatings improve steel corrosion resistance as they are chemically inert and the interruption of the layers prevents the defects typical of PVD (Physical Vapor Deposition) techniques to pass through the entirety of the coating. A crucial property to guarantee the coatings’ performance is their adhesion, which can be improved by previously nitriding the steel. In this work, two treatment processes prior to the deposition of Cr/CrN multilayer coatings on nitrided AISI 4140 steel were compared: pre-cleaning by glow discharge sputtering in vacuum argon and hydrogen atmosphere and sputtering in high vacuum with chromium ions applying a 500 V voltage difference. The microstructure, adhesion and corrosion resistance were studied. Pretreatment of the substrate by sputtering with chromium ions showed the best adhesion and corrosion resistance.