FV520B钢在湿H2S+Cl-环境中的腐蚀疲劳性能

Corrosion Fatigue Behavior of FV520B Steel in Aqueous H2S+Cl- Environment

针对离心压缩机叶轮叶片疲劳寿命研究的需要,考虑到服役环境对疲劳寿命的影响,开展叶轮典型材料FV520B钢在湿H2S+Cl-环境中的腐蚀疲劳试验研究,结合断口形貌观察分析其疲劳失效机理,建立疲劳寿命预测模型。结果表明,FV520B钢在湿H2S+Cl-环境中的疲劳性能相较于大气环境大幅下降,并随着环境中H2S浓度升高而下降;随着应力幅值降低,介质中的H2S对疲劳性能的影响逐渐显现并随应力幅值降低而增大。疲劳断口形貌观察表明,试样表面存在点蚀坑,疲劳裂纹在点蚀坑处萌生并扩展。最后,在点蚀演化寿命预测模型的基础上,结合氢对疲劳演化过程的影响,建立考虑应力及腐蚀介质共同作用的疲劳寿命预测模型,预测结果与试验数据吻合较好。该模型可为湿H2S+Cl-环境下材料的疲劳寿命预测提供基础支持。

In order to investigate the fatigue life of centrifugal compressor impeller, corrosion fatigue tests of FV520B stainless steel in air and aqueous H2S+Cl- environment are carried out. The corrosion fatigue failure mechanism of FV520B steel is analyzed combining with the fracture morphology observation and a modified fatigue life prediction model is built. The results demonstrate that corrosion fatigue lives of FV520B steel aqueous H2S+Cl- environment are dramatically decreased compare with those in air and decreased further with the increasing of H2S. Corrosion fatigue damages caused by hydrogen emerge gradually when the applied stress amplitude is relatively low and increased with the decreasing of applied stress amplitude. Microstructure observation revealed that corrosion pits are found on the surface of the specimens and the fatigue cracks are initiated on the surface of the specimens in all corrosion mediums and then propagated. Considering the effect of hydrogen on fatigue behavior of FV520B steel, a modified fatigue life prediction model is proposed on the basis of pitting corrosion mechanism. The model predictions are in good agreement with the test results, which can provide some insight into fatigue life prediction of materials exposed to aqueous H2S+Cl- environment.