300M steel has been widely utilized in the manufacturing processes of functional parts served in harsh environments. The properties of the parts’ surface layer induced by the grinding process are of great importance for the service performance, which can be determined by the input parameters of processing. This paper carried out evaluation of surface modification of 300M steel material under the scCO₂-assisted grinding process. To further enhance the understanding of this processing design, the generation of surface modification with dry and flood techniques were also compared. The surface morphology, surface roughness, microstructure evolution, work hardening and surface residual stresses were recorded. The mechanism of grain refinement and the substructure of the martensite lath has been revealed. It was found that the scCO₂-assisted grinding processes are responsible for smoother surface profile compared to the dry and flood techniques. Meanwhile, the machined surface roughness was maintained at a stable lower level as the grinding depth increases, proving the great superiority of scCO₂ medium for improving the productivity and process sustainability. The grains in the superficial layer have been noticeably refined after grinding operation while it presents deeper refinement with scCO₂-assisted grinding process. Meanwhile, nanocrystalline and carbide precipitation were clearly found on the refined layer with scCO₂ medium, the crystal defects are mainly the combination of dislocation tangles (DTs), dislocation walls (DWs) and dislocation cells (DCs), and the stacking fault was observed to be the substructure for the lath martensite except the dislocation with TEM analysis. The designed scCO₂-assisted grinding contributes to higher work hardening and compressive stresses compared to dry and flood methods.

300M钢已广泛用于恶劣环境下功能部件的制造过程中。由磨削过程引起的零件表面层的特性对于服务性能非常重要，这可以通过加工的输入参数来确定。本文对scCO ₂条件下300M钢材的表面改性进行了评估。辅助研磨过程。为了进一步增强对该处理设计的理解，还比较了使用干法和溢流技术进行表面改性的产生。记录表面形貌，表面粗糙度，显微组织演变，加工硬化和表面残余应力。揭示了晶粒细化的机理和马氏体板条的下部结构。已经发现，与干法和溢流技术相比，scCO ₂辅助的研磨工艺可实现更平滑的表面轮廓。同时，随着磨削深度的增加，加工的表面粗糙度保持在较低的稳定水平，证明了scCO ₂的巨大优势。提高生产率和过程可持续性的媒介。研磨操作后，表层的晶粒已得到明显的细化，而利用scCO ₂辅助的研磨过程则表现出更深的细化。同时，在scCO ₂介质精制层上清楚地发现了纳米晶和碳化物沉淀，晶体缺陷主要是位错缠结（DTs），位错壁（DWs）和位错晶胞（DCs）的结合，并观察到堆垛层错成为板条马氏体的亚结构，但TEM分析表明其位错除外。与干法和溢流法相比，设计的scCO ₂辅助研磨有助于更高的加工硬化和压缩应力。