齿轮齿根的淬硬层深度研究

A study of the hardened layer at a gear tooth root

研究了齿轮的整体高频淬火工艺,通过不同的淬火时间(分别为12 s和17 s)获得了不同的硬化层.利用显微硬度计测出了齿轮齿根不同厚度的硬度,绘制出了硬度变化规律曲线,并根据经验公式分别测算得到了它们的淬硬层深度.同时利用扫描电镜(SEM)对齿根的淬硬层部分进行了显微组织观察,发现不同的淬火时间在硬化层处获得了不同的淬火组织,淬火时间12 s组织为马氏体+铁素体+残余奥氏体,淬火时间为17 s组织为马氏体+极少量针状铁素体+残余奥氏体,后者组织更均匀,强度更高,因此工艺更理想.

An high-frequency overall quenching process for a gear was conducted,in which various hardened depths at the tooth root were obtained in accordance with the holding time used（12 and 17 seconds）.The microhardness at the root was tested by microhardness tester at various hardened depth,and corresponding curves of microhardness vs.hardened depth were drawn,based on which the overall depth of the hardened layer could be estimated by means of an empirical formula.Meanwhile,the microstructure of the quench-hardened layers were observed by scanning electron microscope（SEM）,showing that the microstructure produced by 12 second holding was composed of martensite,ferrite and residual austenite,while that by 17 second holding composed of martensite,small amount of acicular ferrite and residual austenite.The microstructure yielded by the 17 second quenching was more uniform and stronger than that by the 12 second quenching,thus suggesting that the 17 second quenching process was better than the 12 second one.