Hardness gradient multilayer coating for enhancing tribological property of AISI 1045 steel

Abstract

Specialized equipment vehicles typically operate in complex environments, resulting in wear and failure of the AISI 1045 mild steel rotary seal shaft of the chassis. Extending the life of a material by depositing a hard coating on its surface is an efficient method, and the matrix in the previous study was cemented carbide. However, there is a significant difference in physical properties between the soft AISI 1045 steel and the hard coating, resulting in poor mechanical and tribological property. In this study, we design and prepared CrN/TiAlN multilayer coatings with hardness gradient by arc ion plating to reduce the residual stress inside the coating and enhance the tribological property. The CrN/TiAlN multilayer coatings are composed of CrN layer, CrN/TiAlN alternating layer, and TiAlN layer, in which the coating interfaces are well bonded without obvious defects. The hardness and modulus of CrN/TiAlN multilayer coatings increase with the CrN transition layer thickness, and the coating with 3.53 μm thick CrN layer has the largest hardness of 39.86 GPa, modulus of 386.72 GPa, and binding force of 24.59 N, as well as the smallest residual stress of −449.6 ± 42.3 MPa. After a 10,000 km simulated vehicle driving test, the wear depth of AISI 1045 steel is greater than 70 μm, while the surface of CrN/TiAlN coating has no obvious wear marks. Gradient design reduces the difference in physical parameters between the coating and the substrate, and the thickness increase of the CrN transition layer reduces the influence of the substrate on the coating strength, which together reduces the residual stress of the coating, improves its bonding force, and enhance tribological property. This work provides important prospects for the application of rotating sealing components in vehicles and theoretical references for improving the wear resistance of sealing surfaces.