Effect of Cooling Rate on Pitting Corrosion Behavior of 904L Austenitic Stainless Steel in a Simulated Flue Gas Desulfurization Solution

• Published in: Metals and materials international 2023-03, Vol.29 (3), p.730-747
• Main Authors: Li, Miaomiao, Zou, Dening, Li, Yunong, Tong, Libo
• Format: Article
• Language: English
• Subjects: Austenitic stainless steels; Characterization and Evaluation of Materials; Chemistry and Materials Science; Chromium; Concentration gradient; Cooling; Cooling effects; Cooling rate; Corrosion effects; Corrosion rate; Corrosion resistance; Corrosion resistant steels; Corrosion tests; Depletion; Desulfurizing; Engineering Thermodynamics; Flue gas; Heat and Mass Transfer; Machines; Magnetic Materials; Magnetism; Manufacturing; Materials Science; Metallic Materials; Molybdenum; Pitting (corrosion); Processes; Sigma phase; Solid Mechanics; Solidification; Stainless steel
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-022-01255-z

904L super austenitic stainless steel is prone to harmful secondary phase precipitation, which reduces corrosion resistance. The cooling rate during the solidification of steel is one of the critical factors affecting the precipitation of brittle phases in stainless steel metals. In this paper, the effect of the cooling rates (6, 50, 100, 500, and 1000 °C min −1 ) on the initial corrosion behavior of 904L steel in a simulated flue gas desulfurization (FGD) solution was studied by electrochemical measurements and microscopic morphology observation. The results show that as the cooling rates increases, the primary solidification temperature and the secondary dendrite arm spacing decrease. The precipitated phase in the steel is a σ-phase mainly distributed interdendrites and forms zones of chromium and molybdenum depletion, reducing pitting resistance. With the increase in the cooling rate, the corrosion resistance increases first and then decreases, and reaches the maximum at 100 °C min −1 . At the same time, different cooling rates result in different contents of Cr and Mo in σ phase. At 100 °C min −1 , the concentration gradient of Cr and Mo near the interdendrites is the lowest compared with other cooling rates, which inhibits the growth rate of the σ phase nuclei and produces a more uniform microstructure. Corrosion test results show that pitting corrosion is sensitive to the increase in the contents of Cr and Mo in the σ phase. The higher the content of Cr and Mo in the σ phase, the more serious the depletion of Cr and Mo near the interdendrites, and the worse the corrosion resistance. Graphical Abstract