Temperature-dependent microstructural evolution and wear resistance enhancement of high manganese steel via thermal ultrasonic shot peening

High manganese steel is widely used in harsh working conditions due to its excellent work-hardening effect, but its poor wear resistance under non-impact/low-impact loads severely limits its service life. To address this issue, this paper proposes thermal ultrasonic shot peening (USP) and systematically investigates the microstructure evolution and mechanical property regulation of high manganese steel subjected to USP at different temperatures, revealing the correlation among peening temperature, microstructure, and mechanical properties. The results indicate that the microstructural evolution of high manganese steel under thermal USP is governed by the competition between USP-induced plastic deformation and temperature-driven dynamic recovery/recrystallization. USP at room temperature introduces high-density dislocations and substructures, while thermal USP allows the regulation of grain size, low-angle grain boundaries, and dislocation density. For wear resistance, compared with the unpeened specimen, the volume losses of the specimens peened at 220 °C and 600 °C are reduced by 54% and 55.5%, respectively; compared with the specimen peened at 25 °C, the reductions are 25% and 27%, respectively. This study establishes a qualitative correlation among peening temperature, microstructure, and properties, providing a new method for improving the wear resistance of high manganese steel and offering a theoretical basis and technical guidance for the engineering application of thermal USP.