Improved Mechanical and Wear Properties of AISI-420 Steel by Cathodic Cage Plasma Vanadium Nitride Deposition

In this study, a cathodic cage plasma deposition (CCPD) system equipped with a vanadium cathodic cage is used to deposit vanadium nitride coating on AISI-420 steel. This study aims to improve the tribological and mechanical properties. Specifically, this system is used because it can deposit not only a hard coating but also form a nitrogen diffusion layer that can enhance the load-bearing capacity of the sample and coating adhesion with the substrate. The XRD shows that vanadium nitride (VN) coating is polycrystalline, with a favored orientation along the (200) plane. The SEM results depict that at 673 K, the surface consists of uniformly disseminated spherical nanoparticles agglomerate to form coralloid granular nitrides. At 723 K, polygonal particles are uniformly distributed over the entire surface. The thickness of vanadium nitride films is 0.6 and 1.1 mu m for 673 K and 723 K temperatures. The hardness of the sample increased up to 3 times over the untreated sample, whereas mechanical properties, including elastic modulus, and hardness-elastic modulus ratios H/E,H2/E,H3/E2 are upgraded, specifically at 723 K. Remarkably, the wear rates are reduced more than ten times, and a significant decrease in friction coefficient due to the deposition of VN coating. After the ball-on-disc wear analysis, the wear track is smooth and narrow for coated samples and still covered with vanadium and nitrogen elements, which indicates deposited coating is not detached from the substrate. It shows that VN coating can be deposited effectively to enhance the mechanical and tribological properties of AISI-420 steel.