喷丸对25CrNi2MoV钢滚动接触疲劳性能的影响

目的提高25CrNi2MoV钢的滚动接触疲劳性能。方法对25CrNi2MoV钢进行表面喷丸处理,并采用3D形貌仪、光学显微镜、显微硬度仪、X射线应力分析仪与滚动接触疲劳试验机等仪器,对试样表面形貌、表面显微组织、显微硬度、表面残余压应力与滚动接触疲劳性能等进行测试分析。结果与未处理试样相比,经喷丸处理后,试样表面形貌由磨削加工槽型向酒窝状的弹坑转变,表面粗糙度增大,表面显微硬度由503HV0.2增大到577HV0.2,增加了14.7%,表面残余压应力由-90.0 MPa增大到-758.0 MPa。当喷丸强度为0.445 mmA时,试样具有最好的滚动接触疲劳寿命,其额定寿命(L10)、中值寿命(L50)、特征寿命(L63.2)分别为4.973×10^6次、6.578×10^6次和6.945×10^6次,分别是未处理试样对应寿命的11.1倍、7.3倍和7.0倍,试样滚动接触疲劳失效形式主要为疲劳剥落。当喷丸强度为0.596 mmA时,试样表面出现微裂纹,导致滚动接触疲劳寿命降低,此时试样疲劳失效形式主要为点蚀与疲劳剥落。未处理试样疲劳失效形式主要为分层。结论喷丸处理能细化试样表层晶粒组织,增大试样表面粗糙度、表面硬度与表面残余压应力。合适强度的喷丸处理可以抑制试样表面与次表面裂纹的萌生与扩展,显著提高滚动接触疲劳性能。

Effect of Shot Peening on Rolling Contact Fatigue Properties of 25CrNi2MoV Steel

The work aims to improve the rolling contact fatigue properties of 25CrNi2MoV steel. The surface of 25CrNi2MoV steel was treated by shot peening. 3D profilemeter, optical microscope, microhardness tester, X-ray stress analyzer and rolling contact fatigue testing machine were used to detect and analyze the surface morphology, surface microstructure, microhardness, surface residual compressive stress and rolling contact fatigue properties of the samples before and after shot peening, respectively. Compared with untreated sample, the surface morphology of shot peened sample was changed from grinding groove to dimple-like crater, the surface roughness of the treated sample was increased, the surface microhardness of the treated sample was increased from 503HV0.2 to 577HV0.2, with an increase by 14.7%, the surface residual compressive stress of the treated sample was increased from -90.0 MPa to -758.0 MPa. When the shot peening intensity was 0.445 mmA, the sample had the best contact fatigue life, and its specified life (L10), median life (L50) and characteristic life (L63.2) were 4.973×106, 6.558×106 and 6.945×106 cycles, which were 11.1, 7.3 and 7.0 times the corresponding life of the untreated sample, respectively, and the main rolling contact fatigue failure mode of the sample was classified as fatigue spalling. When the shot peening intensity was 0.596 mmA, the micro cracks appeared on the surface of the sample, resulting in a decrease in rolling contact fatigue life, the main fatigue failure modes of the sample were pitting and fatigue spalling. The main fatigue failure mode of untreated sample was delamination. Shot peening can refine the surface grain of the sample, the surface roughness, surface hardness and surface residual compressive stress of the sample were increased by shot peening. Shot peening with appropriate intensity can inhibit initiation and growth of surface and subsurface cracks on the sample, which can significantly improve the rolling contact fatigue properties.