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Chinese Academy of Sciences on stainless steel pitting mecha

Time:2020-11-14 11:34Source:未知 Author:admin Click:
Recently, China Metal Research Institute of Shenyang National Laboratory for Materials Science (joint) laboratory researcher Ma Xiuliang led the team, using high resolution transmission electron microscopy and found that manganese sulfide inclusions dispersed in the structure with eight oxide (MnCr2O4) nanoparticles. In situ environment in the simulation of materials under the conditions of the causative (outer) of electron microscopy showed that the equivalent of manganese sulfide inherent in the tiny nano oxides in the presence of these tumors". Under certain conditions, the local dissolution of manganese sulfide originated from the interface between it and the tumor, and then expanded to the material.
It is also shown that the presence of the nano eight - surface of the oxide leads to the difference in the rate of dissolution of manganese sulfide. On this basis, the research team and Professor Hu Peijun of The Queen's University of Belfast in the UK, to identify those with strong activity, easy to make the rapid dissolution of manganese sulfide oxide around eight surface with metal ions as the feature of its outer surface ("malignant tumor"); on the contrary, the lower activity of nano eight body surface the oxygen ion as the outer surface ("benign"). This discovery provides direct evidence for the starting position to reveal early pitting corrosion of stainless steel manganese sulfide dissolved, so that people on the understanding of the mechanism of pitting corrosion of stainless steel from the previous micron scale to the atomic scale, provides the structure and composition of the atomic scale information for exploring new ways to improve the pitting corrosion resistance of stainless steels. The results of this study have been published recently in Acta Materialia (Journal of materials) online.
The surface of stainless steel has high corrosion resistance due to the formation of dense chromium oxide film, which can be widely used in the field of modern industry and daily life. However, at the same time, it is difficult to avoid localized corrosion (pitting) of stainless steel. The occurrence of pitting is initiated on the surface of the material, and the nucleation and growth of the two stages, and finally to the depth of the material in the direction of the depth of the rapid expansion. Therefore, the pitting corrosion is of great concealment and burstiness. Especially in the oil, chemical, nuclear power and other fields, pitting corrosion prone to pipe wall perforation, so that a large number of oil and gas leaks, and even cause fire, explosion and other disasters.
Since the beginning of the 30s of last century, the exploration of pitting nucleation mechanism of stainless steel has never been interrupted, pitting has become one of the classic problems in the field of materials science and engineering. Although researchers generally believe that the occurrence of pitting caused by local dissolution of manganese sulfide inclusions in stainless steel, but due to the lack of information structure and composition of micro scale, the initial pitting nucleation site is described as "random and unpredictable". The "unclear" of the initial location of pitting corrosion has been restricted to the understanding of the pitting mechanism and the improvement of pitting corrosion resistance.
The mechanical properties of micron scale oxide inclusions have been widely concerned and have been effectively controlled. For example, the "super clean" steel is obtained by reducing the size of non-metallic inclusions in metallurgical technology. Ma Xiuliang et al. Have shown that even if the size of the oxide is reduced to the order of nanometers, they can still damage the structure of the material by electrochemical means. Therefore, the small scale of oxide inclusions in the traditional (or model) formation and function of metal materials in concern, which is of great significance to improve the long-term service in the service behavior of a medium under the condition of metal materials and biomedical materials.
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