渗碳齿轮钢中的纳米级第二相粒子研究

Researoh on precipitation behavior of nanoscale second phase in carburized gear steels

以20CrMnTiH,SAE8620H两种渗碳齿轮钢为研究对象,利用透射电子显微分析、电子探针显微分析与金相显微组织分析对纳米级第二相粒子(<500 nm)的析出行为进行研究,探讨了纳米级第二相粒子的大小、分布等对奥氏体组织结构的影响规律。研究结果表明:20CrMnTiH渗碳齿轮钢中有AlN,TiN,Ti_(2)AlN三种第二相粒子析出,第二相粒子的数量与轧制温度相关,在900~1050℃高温轧制时第二相粒子数量最少;SAE8620H渗碳齿轮钢中有第二相粒子AlN析出,在800~890℃温度范围内,第二相粒子的析出数量会随正火温度升高先增加后减少,尺寸随温度升高先减小后增大;纳米级第二相粒子的大小和分布会影响渗碳齿轮钢的晶粒,粗大的第二相粒子会减弱其对奥氏体晶粒的钉扎,分布不均匀的第二相粒子会造成奥氏体晶粒异常长大。

In the present paper,the precipitation behavior of nanoscale second phase particles in 20CrMnTiH and SAE8620H carburized gear steels is studied by means of transmission electron mi⁃croscopy,electron probe and metallographic analysis.The results show that the particles including AlN,TiN and Ti_(2)AlN have an important effect on the grain size of austenite in 20CrMnTiH.The number of the particles is dependent on the temperature of rolling and normalizing,and the number of second phase particles is the least in the range of 900℃to 1050℃.The number of the AlN particles in SAE8620H,first increases and then decreases with the increase of normalizing temperature in the range of 800℃to 890℃.The coarse second phase decreases the pinning for the austenite grains.The irregular distribution of the second phase particles lead to abnormal growth of the austenite grains.