热交换管泄漏原因失效分析

Cause analysis of the leakage failure of heat-exchanger tubes

针对某环保设备上热交换换热管的早期泄漏事故,利用直读光谱仪、光学显微镜、扫描电子显微镜、能谱仪等分析手段对其化学成分、金相组织、腐蚀产物进行了分析。试验结果表明,该换热管的失效模式为选择性腐蚀,造成换热管早期失效的主要原因是由于换热管内部介质存在腐蚀性元素S、Cl,并且焊缝区与母材的微区成分、显微组织存在差别,导致焊缝金属与母材在电极电位上存在差异,形成腐蚀原电池而出现选择性腐蚀,最终导致泄漏。

The chemical composition,microstructure,corrosion products of the leaked heat-exchanger tubes used in environmental protection equipments were analyzed by optical emission spectrometer,optical microscope,scanning electron microscope and energy spectrometer.Experimental results demonstrated that the failure mode of the tubes was selective corrosion,and the main reason of the early failure for the tubes was that the tubes were serviced in high corrosion environment which contained S and Cl.The difference in the micro composition and the microstructure between the weld area and the base metal caused a difference in the electrode potential,which formed the corrosion primary cell and caused the selective corrosion and leakage eventually.