QT400球墨铸铁的热疲劳行为

Thermal fatigue behavior of ductile iron QT400

采用V形缺口试样,通过上限温度为500-900℃的热疲劳试验研究了QT400球墨铸铁的热疲劳行为,并对不同上限温度下材料热疲劳裂纹的萌生与扩展以及试样的显微组织与硬度等进行了分析。结果表明,热疲劳裂纹主要从试样的V形缺口底部萌生,上限温度越高,裂纹萌生越早,萌生后扩展速率也越快,其热疲劳寿命越低;随着上限温度的升高,试验后试样基体的硬度逐渐增加,上限温度由700℃上升到800℃时,试样硬度快速上升;热疲劳试验过程中的氧化腐蚀、球墨形态以及组织变化等为球墨铸铁QT400的热疲劳破坏的主要影响因素。

Thermal fatigue behavior of QT400 ductile iron was researched by thermal fatigue test at 500-900 ℃ upper limit temperature using v shape samples,the initiation and growth of the thermal fatigue cracks were observed and the microstructure and hardness of the samples were analyzed. The results indicated that the thermal fatigue cracks initiate mainly from the bottom of V shape groove. The higher the upper limit temperature is,the earlier and faster the cracks initiate and grow,and the lower the thermal fatigue life is. The hardness increases with the increase of upper limit temperature, especially at the range of 700-800 ℃. In addition, oxidation, graphite morphology and microstructure changes were main factors to affect the thermal fatigue behavior of QT400.