Achieving synergistic enhancement of impact and wear resistance in SCMnH11 high manganese steel by a laser-quenching-induced bimodal microstructure

Given the pronounced wear that high manganese steel experiences during the initial stage of service, pre-hardening is indispensable to ensure sufficient hardness and wear resistance. However, improper pre-hardening can compromise toughness and produce poor fracture performance. In this work, laser quenching was employed as a pre-hardening technique to achieve a synergistic enhancement of hardness, toughness, and wear resistance in SCMnH11 high manganese steel by precisely controlling the laser parameters. The results indicate that laser quenching induced a martensitic transformation at the surface of SCMnH11 high manganese steel. The martensite content initially increased with rising laser power, reaching a maximum at 2 kW, and then decreased at higher powers. At this optimal power, the specimen exhibited the highest microhardness, approximately 1.5 times that of the untreated specimen. This resulted from the synergistic contribution of multiple strengthening mechanisms, including transformation-induced hardening associated with martensitic formation, resistance to dislocation motion due to dislocation-twin interactions, and microstructural heterogeneity derived from the development of a bimodal grain structure. Furthermore, the heterogeneous microstructure consisting of both coarse and fine grains facilitated coordinated deformation, thereby suppressing strain localization and maintaining excellent impact toughness. This enhanced surface also influenced the tribological behavior, as surface hardening increased the coefficient of friction, while the wear process on the high hardness surface promoted the formation of mechanically mixed layers composed of wear debris and tribo-oxides. These layers stabilized the contact interface and enhanced wear resistance.