18CrNbTi铁素体不锈钢的高温疲劳性能

High-temperature fatigue property of 18CrNbTi ferritic stainless steel

为了确定应力保载和气氛环境对18CrNbTi铁素体不锈钢高温疲劳性能的影响规律,在800℃及轴向拉-拉应力控制模式下研究了18CrNbTi铁素体不锈钢在氩气和模拟汽车尾气环境中且在最大拉应力处引入10s保载时间的高温疲劳行为,并与18CrNbTi不锈钢在大气环境中无保载时间的高温疲劳行为进行了对比。此外,利用扫描电子显微镜对高温疲劳断口形貌进行了观察与分析。结果表明,在大气环境中,18CrNbTi铁素体不锈钢的疲劳极限为25MPa;引入10s保载时间后,18CrNbTi不锈钢的疲劳抗力和疲劳寿命均显著降低;与在氩气环境中相比,18CrNbTi不锈钢在模拟汽车尾气环境中的疲劳抗力和疲劳寿命进一步降低。在不同实验条件下,疲劳裂纹均是以穿晶方式萌生并以穿晶方式扩展。

In order to determine the influence of dwell time and atmosphere environment on high-temperature fatigue properties of 18 CrNbTi ferritic stainless steel,the high-temperature fatigue behaviors of 18 CrNbTi steel with 10 s dwell time at maximum stress in argon and simulated automobile exhaust gas were investigated under axial tensiontension stress-controlled mode at 800℃,and compared with its high-temperature fatigue behavior in air without dwell time.The fracture surfaces of fatigued specimens were observed with scanning electron microscope.The results show that：the fatigue limit of 18 CrNbTi steel in air is 25 MPa;the fatigue resistance and fatigue life of18 CrNbTi steel significantly reduce after introducing 10 sdwell time;in comparison with those in argon,the fatigue resistance and fatigue life have a further decrease in the simulated automobile exhaust gas;the fatigue cracks both initiate and propagate in a transgranular mode under all testing conditions.