40Cr钢表面纳米层形成机理的研究

Discussions on Formation Mechanism of Nanocrystallized Layer of 40Cr Steel

通过扫描电子显微镜、X射线衍射仪和透射电子显微镜分析研究了高能表面处理后40Cr钢表面纳米层的组 织结构,探讨了表面纳米层的形成机理.利用纳米压痕仪测定了表面纳米层的硬度.结果表明,采用高能表面处理 技术在40Cr钢表面制备出平均晶粒尺寸约为11nm的表面纳米层.纳米层的形成过程中,粒状渗碳体易于产生应 力集中,在集中应力的作用下通过破裂碎化形成纳米晶;铁素体通过位错产生、缠结等,细化为小尺寸晶粒.表面纳 米层的硬度明显提高.

The microstructures of the nanocrystalline layer in 40?Cr steel induced by using a high-power surface processing (HPSP) technique were characterized by means of scanning electron microscopy (SEM),X-ray diffraction (XRD) and transmission electron microscopy (TEM).A possible mechanism of the nanocrystallined layer was discussed.Nanohardness of the nanocrystalline layer was measured by nanoindentation.Experimental evidences showed that the nanocrystalline layer was fabricated on the surface of 40?Cr steel treated by HPSP treatment.The mean grain size in the surface layer is about 11 nm.The mechanism of the nanocrystalized layer can be discribed as follows∶particulate cementite is fractured,which is induced by the concentration of stress; after dislocations generation,accumulation and interaction in ferrite,and so on,the dislocation activities lead to the formation of the dislocation cells,ferrite nanocrystals coming into being.The nanohardness in the surface nanocrystallized layer is enhanced significantly after HPSP treatment.