S316L不锈钢压力壳点蚀失效分析

使用S316L不锈钢材质制造的压力壳下体在工作2000 h之后，其内表面存在大量的点蚀坑，压力壳内壁处于柴油燃烧产物的弱酸性气体环境。本文分析了S316L不锈钢压力壳材料的化学成分和力学性能。使用扫描电子显微镜观察了点蚀坑形貌，使用能谱对腐蚀产物进行了表征。金相分析和XRD表明，在奥氏体基体中存在大量的夹杂物和铁素体相。点蚀坑在内表裂纹深处形核。分析认为，材料的自身因素诱发了点蚀的形核，而压力壳所提供的腐蚀环境加速了点蚀的生长过程。

Pitting Corrosion Failure Analysis of a S316L Stainless Steel Pressure Shell

Numerous pits were observed on a S316L stainless steel pressure shell after discontinuous service for 2000 h. The inner side of the pressure vessel was encountered with a weak acid atmosphere mainly consisting of combustion products of oil and oxygen. In order to probe the cause of pitting failure, the microstructure, chemical composition and the mechanical properties of the 316L steel were examined, and the morphology and corrosion product of pits were characterized by means of scanning electron microscopy and energy-dispersive X-ray spectroscopy. Results show that there exist massive inclusions and ferrite bars, which are confirmed by XRD, in the austenite matrix. Pits might initiate in the depths of cracks on the inner side of the shell, and which may be ascribed to the existed weakness within the steel, while the work condition of S316L stainless steel shell could accelerate the pitting propagation process.