稀土La对高碳合金工具钢高温氧化性的影响

Effect of Rare Earth La on High Temperature Oxidation of High Carbon Alloy Tool Steel

研究了添加稀土La对高碳合金工具钢高温氧化性的影响。通过热分析仪及增重法分析未添加和添加稀土La的高碳合金工具钢的高温氧化行为,并利用扫描电镜观察氧化膜形貌;通过观察氧化层断面形貌分析氧化层结构及分层情况。结果表明,未添加和添加La的高碳合金工具钢在900、1 000、1 100、1 200℃下的恒温氧化动力学曲线均符合抛物线规律,二者的氧化膜均具有保护性。添加稀土La的高碳合金工具钢的氧化反应激活能比未添加稀土La的合金工具钢提高了23%,其氧化速率常数也更低。添加稀土La的高碳合金工具钢的氧化膜粘附性更强,氧化层更坚固。加入稀土La细化了高碳合金工具钢表面氧化膜晶粒,减小了氧化膜晶粒间空隙,使氧化膜不易脱落。

The effect of La addition on high temperature oxidation of high carbon alloy tool steel was stud- ied. The high-temperature oxidation behavior of high carbon alloy tool steel without and with rare earth La was analyzed with thermal analyzer and weight gain method. The morphology of oxide film was observed by scanning electron microscopy. The structure of the oxide layer and its layering were analyzed by observing the cross-sectional morphology of the oxide layer. The results show that all the kinetic curves of iso- thermal oxidation at 900 ℃, 1 000 ℃, 1 100 ℃ and 1 200 ℃ of high carbon alloy tool steels with and without La are in accordance with the parabolic law,and the oxide films of the two alloy tool steels are protective. The oxidation reaction activation energy of high carbon alloy tool steel with rare earth La is 23% higher than that without La addition, and its oxidation rate constant is also lower. The adhesion of the oxide film on the high carbon alloy tool steel with rare earth La is stronger,and its oxide layer is more solid. The addition of rare earth La refines oxide film grains on high carbon alloy tool steel surface, and reduces the interspace among oxide film grains, resulting in the oxide films not easy to peel off.