GCr15SiMn轴承钢超声滚压表层组织及性能分析

Analysis of Surface Microstructures and Properties of GCr15SiMn Bearing Steel Processed by Ultrasonic Rolling Technology

目的 通过不同超声滚压加工工艺对GCr15SiMn轴承钢磨削态试样进行表面强化处理,并研究超声滚压加工工艺对表层组织及性能的影响。方法 采用扫描电子显微镜(SEM)对试样表面、截面组织进行观察,并用粗糙度仪和硬度仪对表面粗糙度、显微硬度进行表征。对不同电流、静压力参数下超声滚压加工试样表面、截面组织和性能的差异进行了分析。结果 根据机加工细晶层及微裂纹可将原始试样分为3类:第1类为无裂纹机加工细晶层;第2类为有裂纹机加工细晶层;第3类为无机加工细晶层。超声滚压加工后,3类表层均被预置塑性变形层,但塑性变形层厚度有明显差别,第3类原始试样形成的塑性变形层最厚,约为2μm;试样表面磨削犁沟变浅,粗糙度显著改善,较原始粗糙度值降低了67%,表层磨削微裂纹扩展,部分表层机加工细晶剥落,表面微裂纹尖端角度减小,表面缺陷减少;表面硬度分布均匀性得到改善并预置表面硬化层,较原始表面硬度提升2%。结论 随电流的增加,粗糙度降低,塑性变形层的厚度和连续性提高,硬化层的硬度及厚度基本不变。随静压力的增加,硬化层的硬度及厚度增加,塑性变形层的厚度和连续性提高,粗糙度基本不变。

This paper aims to strengthen the surface of GCr15SiMn bearing steel with a grinding state by different ultrasonic rolling processes, and studies the influence of ultrasonic rolling process on microstructures and properties of the surface. The main methods used that specimen surface and microstructure of cross-section were observed by scanning electron microscope(SEM), and the surface roughness and microhardness were respectively characterized by roughness and Vickers hardness meters;The differences in microstructures and properties of the ultrasonic rolling specimens processed by different current and static pressure were analyzed. The results showed that the original specimens could be classified into three categories: fine-grain layer without crack, fine-grain layer with crack and layer without fine-grain, according to the fine-grains layer and microcracks.After ultrasonic rolling processing, the three kinds of surface layers were preset by the plastic deformation layer, but the thickness of the plastic deformation layer was significantly different. The plastic deformation layer formed by the layer without fine-grain was the thickest, which was about 2 μm;The grinding furrow of the specimen’s surface became shallower, and the roughness was significantly improved, 67% lower than original roughness. The grinding microcracks of the specimen’s surface were expanded, and some surface machining fine grains were peeled off. The angle of the surface microcracks tip was smaller,and the surface defects were reduced;The uniformity of surface hardness distribution was improved and the surface hardening layer was preset, 2% higher than original surface hardness. The conclusion of the paper is that with the increase of current, the roughness is decreased, and the thickness and continuity of the plastic deformation layer are increased, and the hardness and thickness of the hardened layer remain basically unchanged;With the increase of static pressure, the hardness and thickness of the hardened layer are increased, and the thickness and continuity of the plastic deformation layer are increased, and the roughness remains basically unchanged.