Influences of Carbon and Nitrogen Content on the Precipitation of 18Cr18Mn Steel

Abstract:

The effect of carbon and nitrogen contents on microstructure and the mechanism of precipitation of 18Cr18Mn steels at as-cast and aging treatment state were investigated by thermodynamics calculation, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results show that the increase in carbon and nitrogen contents promotes the precipitation of carbides and nitrides, respectively, inhibiting σ phase precipitation during solidification process. The rod-like σ phases present in 18Cr18Mn0.44N as-cast steel with 0.025%C. The coarse lamellar structure Cr₂₃C₆ phases with a space width of 0.34μm exist in 18Cr18Mn0.44N as-cast steel with 0.16%C. However, Cr₂₃C₆ and σ phase disappear in the interior of the grains and a small amount of nitrides exist only in grain boundaries of 18Cr18Mn0.72N0.020C as-cast steel. The precipitation of Cr₂₃C₆ and σ phases are greatly inhibited in high nitrogen austenitic stainless steels at 800°C aging treatment. Additionally, Cr₂N, the main precipitation phase, nucleates at austenitic grain boundary and grows towards inner grains with a lamellar morphology. Moreover, the quantity of Cr₂N increases and incubation time of it decreases as nitrogen or carbon content increasing.

• Periodical: Materials Science Forum (Volume 789)
• Pages: 297-302
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.789.297
• Online since: April 2014
• Authors: Jing Yuan Li*, Fei Fang, Yi De Wang, Bo Li, Xiang Jun Zhang
• Keywords: Austenitic Stainless Steel, Carbon, Microstructure, Nitrogen Content, Precipitation

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