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| Corrosion Failure of Stainless Steel Bellows in Marine Atmosphere |
| Received:August 23, 2020 Revised:September 15, 2020 |
| View Full Text View/Add Comment Download reader |
| DOI：10.7643/issn.1672-9242.2020.12.014 |
| KeyWord:stainless steel bellows ocean atmosphere pitting intergranular corrosion |
| Author | Institution |
| YAO Qiong |
Unit 63796, PLA, Xichang , China |
| CHEN Jun-hang |
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing , China |
| SONG Yu-hong |
Unit 63796, PLA, Xichang , China |
| JIA Hong-liang |
Unit 63796, PLA, Xichang , China |
| LIU Zhi-yong |
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing , China |
| WU Jun-sheng |
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing , China |
| LI Xiao-gang |
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing , China |
| XIAO Kui |
Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing , China |
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| Abstract: |
| The work aims to study the corrosion failure mechanism of 06Cr19Ni10 stainless steel bellows in tropical marine atmosphere. The macro morphology of the failed conduit was analyzed to determine the macroscopic corrosion characteristics. The microstructure and chemical composition of the failed pipe section were further analyzed. Stereo microscope, Scanning Electron Microscope (SEM) and Electronic Differential System (EDS) were used to observe the microscopic corrosion morphology of the failed pipe section and analyze the corrosion products. From a macro point of view, the metal mesh sleeve on the pipe and the outside of the bellows were slightly corroded. The side of the bellows was corroded slightly, and no corrosion was found inside. The metallographic structure showed that the base material of the bellows was austenite grains, and there was a small amount of martensite on the top of the U-shaped bellows. The chemical composition of the base material of the bellows met the requirements of the national standard. Under the scanning electron microscope, serious pitting corrosion occurred on the outer surface of the bellows. There were large pits on the top of the U-shaped bellows and the platform between the corrugations. The pitting on the top of the U-shaped bellows was more serious. And different position of the bellow had obvious intergranular corrosion. The EDS at the pits showed that most of the corrosion products were Fe oxides, a small amount of Cl- was also found in the pits, and the Cr content of the products in the pits was significantly less than that of the matrix. Due to improper solution treatment of the bellows, the intergranular chromium is depleted, causing intergranular corrosion in most areas of the material surface. At the same time, the plastic deformation of the top of the corrugated tube induces the formation of martensite, which makes it more prone to pitting corrosion. The chloride ions in the atmosphere further promoted the occurrence of this kind of pitting corrosion, and finally led to the corrosion failure of the bellows. The pitting corrosion occurring at the top of the U-shape is the main cause of material failure. |
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