Modification of Tribological Properties and Microstructure in AISI 4140 Steel with Electromagnetic Coupled Cryogenic Treatment

AISI 4140 steel is widely used to manufacture components with high-stress requirements. These components are often subjected to friction and wear, making wear resistance a key factor affecting their service life and reliability. To enhance the tribological performance of AISI 4140 steel, a novel electromagnetic coupled cryogenic treatment was proposed. The optimal parameters were a cryogenic temperature of − 190 °C, cryogenic time of 24 h, magnetization intensity of 1.5 T, and magnetization time of 15 s. The treatment enhanced the wear resistance by 22.09 and 33.68% relative to cryogenic treatment and heat treatment, respectively, while preserving a high hardness. Microstructure analysis revealed a greater dislocation density and precipitation of Fe₂C carbides, which were numerous, small-sized, and well-dispersed. Notably, high-density dislocations can fragment and refine carbides. However, prolonged magnetization time leads to dislocation pile-up, which adversely affects material properties.