GCr15轴承钢表面渗硼层生长动力学与机械性能

对GCr15轴承钢表面渗硼层的生长动力学与机械性能进行了研究.采用固体渗硼的方法,在1123、1173、1223和1323 K温度条件下,分别保温处理2、4、6和8 h,进行渗硼层制备.采用光学显微镜、扫描电镜、X射线衍射仪、维氏硬度计等对制备的渗硼层进行组织观察与性能分析,并通过试验数据对渗硼层的生长动力学特性进行了研究.研究结果表明:试样表面获得了均匀致密的渗硼层,渗硼层的相成分主要是FeB和Fe₂B;渗硼层的厚度随处理温度与保温时间的增加而增厚,变化范围为33.4~318.5 μm;渗硼层的表面硬度随处理温度及保温时间的增加而增大,主要是由于随着渗硼层厚度的增加,高硬度FeB相的含量上升,低硬度Fe₂B相的含量下降,表面硬度HV_0.1变化范围为1630~1950,与基体组织相比,提高了5~6倍;渗层截面硬度测试结果表明,渗层与基体之间有较宽的硬度梯度过渡;通过Arrhenius公式,对渗硼层的生长动力学方程进行了推导,可知B元素在GCr15轴承钢中的扩散激活能为188.595 kJ·mol-1,对推导的动力学方程进行了试验验证,结果表明最大误差仅4.93%,可有效的实现对渗层厚度的预测. 

Kinetics and mechanical properties of borided GCr15 bearing steel

The kinetics and mechanical properties of borided GCr15 bearing steel was investigated. The boriding treatment was carried out in a solid medium at 1123, 1173, 1223, and 1323 K for 2, 4, 6, and 8 h. The microstructures and mechanical properties of the boride layer were characterized by optical microscopy, scanning electron microscopy, X-ray diffraction, and Vickers hardness tester, and the growth kinetics characteristics were also studied based on experimental data. The results indicate that the boride layer has a smooth and compact morphology, and the presence of FeB and Fe₂B on the steel substrate is confirmed by X-ray diffraction analysis. The thickness and hardness of the boride layer increase with treatment time and temperature, where the thickness ranges from 33.4 to 318.5 μm. The increased hardness is mainly because of the increase in the highly hard FeB phase content. The content of Fe₂B phase, which has a low hardness, decreases with an increase of layer thickness. The hardness of the boride layer HV_0.1 ranges within 1630-1950, and it is increased by 5 to 6 times compared with the matrix. The hardness test results of the boride layer cross section indicate that there is a wide transition of hardness gradient between the boride layer and the matrix. The kinetic equation based on the experimental data and Arrhenius equation was investigated, the active energy of B element in the GCr15 bearing steel is 188.595 kJ·mol-1, and the derived kinetic equation is verified by experiments. The results indicate that the maximum error between the theoretical derivation and experimental derivation is 4.93%. Therefore, the derived kinetic equation can effectively predict the thickness of the boride layer on GCr15 bearing steel.