Influence of plasma nitriding pre-treatment on the corrosion and tribocorrosion behaviours of PVD CrN, TiN and AlTiN coated AISI 4140 steel in seawater

Abstract

CrN, TiN and AlTiN coatings were applied by the Physical Vapour Deposition (PVD) method on AISI 4140 and plasma nitrided (PN) AISI 4140 steel. The study aimed to investigate the effect of plasma nitriding before PVD on the corrosion and tribocorrosion behaviour of AISI 4140 steel in seawater. The electrochemical corrosion behaviour of the samples was evaluated in natural seawater by the potentiodynamic polarisation method. Tribocorrosion tests were performed against alumina in natural seawater under 5 N load and open circuit potential (OCP) using a ball-on-disk tribometer coupled with an electrochemical cell. As a result of the study, plasma nitriding applied before the coating significantly improved corrosion and tribocorrosion resistance of PVD CrN, TiN and AlTiN coatings. Besides, it was concluded that duplex treated low alloy AISI 4140 steel could be a candidate instead of stainless steel in tribocorrosion conditions for the marine environment.