The Effect of a CrN Interlayer on the Corrosion-Fatigue Performance of DLC-Coated C55 Steel in Simulated Seawater

The work focused on evaluating the tribological, corrosion, and fatigue properties of a Diamond like Carbon (DLC) coating and a duplex CrN/DLC coating in a 3.5% NaCl solution simulating the aggressive environment of seawater. C55 steel was selected as the substrate material due to its widespread industrial application in the production of highly stressed machine components and its relatively low resistance to corrosion damage. The experimental results demonstrated that the application of DLC and CrN/DLC coatings significantly improved the tribological and corrosion properties of the investigated material in a chloride corrosive environment. At the same time, it was shown that the duplex CrN/DLC coating not only eliminated the negative effect of the corrosive environment on the fatigue properties of C55 steel but even led to their improvement. The fatigue limit of C55 steel with the CrN/DLC coating reached 717 MPa, representing an increase of 3.3% compared with the base material and 29.2% compared with uncoated C55 steel after 72 h of corrosion exposure in a 3.5% NaCl solution. The superior fatigue performance of the CrN/DLC system was associated with its improved adhesion and barrier properties provided by the duplex coating architecture and the CrN interlayer.