1997 Volume 83 Issue 1 Pages 66-71
In order to study the difference between the effects of carbon and nitrogen on intergranular corrosion of ferritic stainless steels, Fe-Cr alloys were chosen as a model system. Five different Fe-18Cr alloys with carbon concentrations of 0.001 to 0.013 mass percent and nitrogen concentrations of 0.002 to 0.013 mass percent were utilized to observe the susceptibilities to intergranular corrosion and the growth rates of (Fe, Cr) 7C3 carbide and Cr2N nitride particles precipitated on grain boundaries. The intergranular corrosion of the alloys, which were homogenized at 1273K for 600s and then annealed at 873K for 100 to 1000s, in chrolide solutions is more pronounced at high carbon concentrations than at high nitrogen concentrations. The difference in the susceptibilities to intergranular corrosion is due to greater thickness of chromium depleted zones along grain boundaries in the high carbon alloys than in the high nitrogen alloys, resulting from a greater growth rate for the carbide than for the nitride.
