快速多重旋转碾压对碳钢表面组织结构及渗硼的影响

Effect of Rapid Multiple Rotating Rolling on Surface Structure and Boronizing of Carbon Steel

目的进一步提高碳钢表面低温B-Cr-Re固体渗硼层的质量。方法采用快速多重旋转碾压法(Fast multiple rotation rolling,FMRR)对碳钢表面进行预处理,然后进行低温B-Cr-Re固体共渗研究。利用透射电子显微镜、高分辨透射电子显微镜、扫描电子显微镜、X射线衍射仪等测量仪器对基体表层组织结构、显微硬度和渗硼层组织结构进行了表征。结果经FMRR处理后,基体表层发生严重塑性变形,沿着垂直于基体表面由表及里的方向,变形程度逐渐变小,总变形层厚度约为30μm,变形方向呈方向一致的流线结构;部分晶粒发生破碎现象,晶粒逐渐细化,出现约为30nm的纳米结构层,同时观察到基体表层存在非晶、孪晶、高密度位错等结构缺陷。经FMRR处理后,只有?-Fe相的X射线衍射峰变宽,但未发现新相产生。结论经FMRR处理后,基体表层显微硬度明显提高,基体表面得到明显强化。FMRR方法提高了基体表面低温B-Cr-Re共渗速度,低温渗硼层的平均厚度约为30μm,约为未处理低温渗硼层厚度的1.7倍,低温渗硼层质量也明显得到改善。

The work aims to further improve the quality of low temperature B-Cr-Re solid boronizing layer on carbon steel surface. The surface of carbon steel was treated by Fast Multiple Rotation Rolling(FMRR). Then, the low temperature B-Cr-Re solid permeation was studied. The structure, microhardness and boronizing layer of the substrate were characterized by transmission electron microscope, high resolution transmission electron microscope, scanning electron microscope and X-ray diffraction. After FMRR treatment, severe plastic deformation occurred on the surface of the matrix and along the vertical surface of the matrix, the degree of deformation decreased gradually from the inside to the outside. The total deformation layer thickness was about 30 μm and the formation direction was streamline structure with uniform direction. Some of the grains were broken,the grains were gradually refined and the nanostructure layer was about 30 nm. Meanwhile, defects such as uncrystaline state,twin and high density dislocation were observed on the surface of the carbon steel. After FMRR treatment, the X-ray diffraction peak became wider, but no new phase was found. The microhardness of the surface of the matrix increases obviously and the surface of matrix is obviously strengthened. The FMRR improves the low temperature co-permeation speed of the substrate. The average thickness of the low-temperature boronizing layer is about 30 μm, which is 1.7 times that of the untreated low-temperature boronizing layer. The quality of the low-temperature boronizing layer is obviously improved.