奥氏体化温度对51CrV4钢组织及疲劳性能的影响

Effect of austenitizing temperature on microstructure and fatigue properties of 51CrV4 steel

利用拉-拉疲劳试验方法对比研究了51CrV4钢不同奥氏体化温度下试样的疲劳性能,并采用扫描电镜(SEM)对其微观组织变化和疲劳断口进行了分析。结果表明,当奥氏体化温度由850℃升高至900℃后,疲劳强度由840 MPa增加到883 MPa,疲劳断口表面二次裂纹数量增多,且主裂纹扩展路径更曲折,裂纹扩展速率降低。且随着奥氏体化温度的升高,组织中合金渗碳体得到细化,部分碳和合金元素从大尺寸合金渗碳体中回溶到基体中,增加了固溶强化,强度和硬度分别增加约32 MPa和20HV。通过分析发现,合金渗碳体细化及碳和合金元素的回溶是疲劳性能改善的主要因素。

Fatigue properties of the 51 CrV4 steel were investigated by comparison at different austenitizing temperature with tension-tension fatigue tests, and the microstructure changes and fatigue fractures were analyzed by scanning electron microscopy(SEM). The results show that the austenitizing temperature increases from 850 ℃ to 900 ℃, the fatigue strength increases from 840 MPa to 883 MPa, the number of secondary cracks on the fatigue fracture surface increases, and the main crack propagation path is more tortuous, and the crack growth rate decreases. The alloy cementite in the microstructure is refined, and some carbon and alloy elements are dissolved back into the matrix from the large-size alloy cementite, which increases the solid solution strengthening, and the strength and hardness increase by about 32 MPa and 20 HV, respectively. Through analysis, it was found that the refinement of large-size alloy cementite and the back-melting of some carbon and alloy elements are main factors to improve the fatigue properties.