Improvement of the Wear Resistance of AISI4140 Steel by Duplex Treatment Combining Gas Nitriding and Physical Vapor Deposition

Previous studies have noted that gas nitriding and physical vapor deposition coating (PVD) considerably affect the wear resistance, friction coefficient and microstructure of AISI 4140 steel. This work studies the impact of gas nitriding and coating treatment (physical vapor deposition) on the wear resistance, friction coefficient and microhardness of this steel. The microhardness of the nitrided and PVD-coated layer increased with increasing nitrogen concentration, reaching approximately 1750 HV0.05 at a processing temperature of 525 ℃ and an ammonia content of 35%. Optical microscopy was used to study the structural properties of the nitrided layers. Furthermore, the presence of nitrogen and the TiN coating had a significant influence on the scratch resistance for a single pass, with a critical load (LC1) of approximately (5 N). Multi-pass scratching tests were used to study the wear volume, degradation process and friction coefficient. Furthermore, the multi-pass scratch method was used to obtain valuable data on the mechanical behavior and damage of the layer following duplex treatment, by combining gas nitriding and coating (PVD).