GCr15SiMn贝氏体轴承钢超声滚压表层组织与性能

Effect of Ultrasonic Rolling Process on Surface Microstructures and Properties of GCr15SiMn Bainitic Bearing Steel

目的 研究超声滚压加工对贝氏体轴承钢的影响,并分析超声滚压工艺参数对贝氏体轴承钢试样表层组织及性能的影响规律,为提升贝氏体轴承表面性能提供理论及试验依据。方法 通过超声滚压加工前后试样对比分析,确定超声滚压处理技术对贝氏体轴承钢组织性能的提升;通过单因素试验法,研究超声滚压工艺试样组织、性能的影响规律;通过表面与截面组织相结合的方法,分析贝氏体轴承钢组织的类别特征。结果 根据试样表面状态可将原始试样分为3类:细晶层存在表面微裂纹的截面组织、细晶层无裂纹的截面组织及无细晶层截面组织。超声滚压后,3类截面组织均产生塑性变形层,无细晶层截面组织形成的塑性变形层最厚。超声滚压处理后,存在于原始试样表面的机加工纹理变细,犁沟变浅;试样表面粗糙度降幅可达75%,试样表面硬度增幅为4%,且试样表面产生了约90μm硬化层。结论 相同静压力下,随电流增加,试样表面粗糙度显著降低,塑性变形层显著增加,硬度、硬化层深度增加但增幅较小;相同电流下,随静压力增加,试样表面硬度、塑性变形层深度、硬化层深度及表面硬度增加,粗糙度变化不大。

In contemporary mechanical production,bearings are referred to as "mechanical joints" because they support the rotation of various equipment components,reduce friction during usage,and ensure rotational precision.The failure of bearings,which affects the machine's operational state and potentially its safety,has drawn a lot of attention.Bainitic steel(especially lower bainitic steel) demonstrates significant benefits in rolling contact fatigue resistance due to its high hardness,toughness,and excellent comprehensive qualities.This work involved applying the ultrasonic rolling method to the surface treatment of bainitic bearing steel and examining how it affected the surface microstructures and properties of the GCr15Si Mn bainitic bearing steel.The surface microstructures and properties of the race specimens of bainite bearings were compared and analyzed before and after the ultrasonic rolling treatment,and the effects of different ultrasonic rolling processes(current and static pressure) on the surface microstructures and properties of the samples were investigated,which offered a theoretical and experimental foundation for enhancing contact fatigue resistance and service life of GCr15SiMn bainite bearings.The three-dimensional morphology,surface morphology and cross section of the sample surface before and after ultrasonic rolling were observed with a Leica three-dimensional microscope and a scanning electron microscope,and the surface roughness and microhardness were measured with a roughness meter and a microhardness tester.The surface and cross-sectional microstructures of samples subjected to ultrasonic rolling with different parameters were analyzed.The results indicated that the surface condition of the original samples could be categorized into three types:cross section with surface microcracks in the fine-grained layer,cross section without cracks in the fine-grained layer,and cross section without the fine-grained layer.The ultrasonic rolling process created a plastic deformation layer in the three types of cross sections,and the thickness of the resulting plastic deformation layer was proportional to the fine crystalline layer of the surface,with the cross section without the fine-grained layer possessing the thickest layer.The cross section with surface microcracks in the fine-grained layer was fragmented and uneven,and there were grinding cracks at a depth of approximately 1 μm that extend parallel to the surface.The fine-grained structure was distributed on both sides of the crack,and the lowest portion of the fine-grained layer contained an approximately 0.5 μm thick plastic deformation layer.The surface of the original cross section without the fine-grained layer was generally flat,with nearly no microcracks,and there was a uniform structure morphology along the depth direction.After ultrasonic rolling,the surface's machined texture became thinner,and the furrow became shallower.The surface roughness of the sample decreased by 75%,the surface hardness of the sample increased by 4%,and the sample surface created a hardened layer of approximately 90 μm.Although the depth of the hardened layer and surface hardness of the sample increase with an increase in static pressure,the depth of the plastic deformation layer,the hardened layer,and the surface hardness of the sample decrease significantly with the increase of current.However,the depth of the hardened layer and surface hardness of the sample increase significantly with the increase of static pressure.