压应力对Fe-20Cr合金高温氧化膜生长和失效影响

Compressive stress effects on oxide-scale growth and failure of Fe-20Cr alloys during high temperature oxidation

为了明确外加应力对于合金高温氧化行为的影响,采用热重(TGA)方法测定了Fe-20Cr合金在900℃无应力及外加压应力5、8、10及15 MPa下氧化20 h内的氧化速率,通过扫描电镜(SEM)观察了有无应力作用下的氧化膜表面形貌,分析了压应力下氧化动力学的变化和氧化膜的失效.结果表明:外加压应力得到的氧化速率较无应力下大.从氧化膜形貌上观察,压应力下的氧化物颗粒明显小于无应力下的氧化物颗粒.另外,氧化膜的失效显示了45°剪切滑移的特征.从应力对氧化物形核讨论了压应力下Fe-20Cr合金的高温氧化行为,认为压应力通过促进氧化形核,进而晶界数量增多,晶界扩散占优,氧化速率得到提高促进了Fe-20Cr合金的氧化动力学.

In order to better understand the effects of external loads on the high temperature oxidation behavior of alloys,the oxidation behavior of a Fe-20Cr alloy under compressive stress was investigated by thermogravimetric analysis（TGA）.Compressive samples were subjected to stresses in the range of 5 to 15MPa and the oxidation behavior was also studied at a temperature of 900℃ in air.This study primarily compared oxidation kinetics and surface morphology of the oxidized samples.The results showed that applying a compressive stress induced an increase in the oxidation rate.Morphological observation showed that the size of the oxide particle formed under the compressive stress was obviously smaller than that without stress.In addition,the failure of oxide scales showed shear failure and slip bands generated under 45° shear cut.The oxidation behavior of the Fe-20Cr alloy under compressive stress was analyzed in terms of the effect of compressive stress on oxide nucleation.It was suggested that the application of compressive stresses promoted oxide nucleation.The oxide particle size was so small that grain boundary diffusion controlled the growth process,thereby increasing the oxidation kinetics of Fe-20Cr.