Recently, Professor Jiang Zhouhua's team from the School of Metallurgy, NEU, has made an important breakthrough in improving the innovative design of stainless steel corrosion resistance. The study titled Design for Improving Corrosion Resistance of Duplex Stainless Steels by Wrapping Inclusions with Niobium Armour was published in the journal Nature Communications. The authors of this paper are Zhang Shucai, Feng Hao, Li Huabing, Jiang Zhouhua, Zhang Tao, Zhu Hongchun, Lin Yue, Zhang Wei and Li Guoping, among whom the first author is lecturer Zhang Shucai from the School of Metallurgy, and the corresponding author is Professor Li Huabing from the School of Metallurgy/ Polymetallic Symbiotic Ore Ecochemical Metallurgy, Key Laboratory of the Ministry of Education. The School of Metallurgy of NEU is the first completion unit, Professor Zhang Tao from the School of Materials Science and Engineering of NEU, Dr. Zhang Wei from CITIC Metal, and Professor and Senior Engineer Li Guoping from Shanxi Taigang Stainless Steel are the co-authors.
Corrosion of steel materials will not only lead to catastrophic safety accidents, but also cause huge economic losses. To meet the long life requirements of infrastructure and equipment, a series of highly corrosion-resistant stainless steels have been developed. However, with the increasingly harsh service environment, such stainless steel will still be corroded. Non-metallic inclusions are one of the main causes of corrosion, usually resulting in serious impact. In extremely harsh environments such as high temperature and high chlorine, the harm of non-metallic inclusions is particularly prominent. In this regard, researchers have explored many methods to reduce the harm of these inclusions, such as deep deoxidation, deep desulfurization and modification treatment. However, the effectiveness of these methods is limited, and the inclusions or surrounding matrix will still be corroded. Therefore, how to effectively prevent corrosion caused by inclusions has become an imminent challenge in the field of corrosion prevention of steel materials.
This study has broken the limitation of the traditional thinking of "relying on cleanliness control and modification treatment to reduce the harm of inclusions". It innovatively proposes the strategy of "using corrosion-resistant niobium armour (Z phase) to wrap harmful inclusions to significantly improve the corrosion resistance of duplex stainless steel". The strategy cleverly uses the principles of microalloying and heterogeneous nucleation to achieve two key objectives: effective inclusion wrapping with niobium-containing Z phase (FIG. 1) and good corrosion resistance of Z phase and its surrounding matrix (FIG. 2).
In this study, a new and ingenious strategy is developed to use corrosion-resistant "niobium armour" (Z phase) to wrap harmful inclusions, overcoming the problem of "corrosion caused by inclusions". This strategy has strong universality in the series of duplex stainless steels (S32101, S32304, S32205, S32507, and S32707) and industrial production (FIG. 3).。This study has provided a new idea for corrosion prevention of stainless steel materials, which is of great significance to ensure long life and safe and stable operation of high-end equipment.
The research work has received support from the National Natural Science Foundation of China, the Special Project of Liaoning Province for Guiding Local Science and Technology Development, the Fundamental Research Funds for the Central Universities, the China Postdoctoral Science Foundation, CITIC Metal and TISCO, and the help from the Analysis and Test Center of NEU in organizational characterization.
