Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Effect of Tungsten on the Ostwald Ripening of M23C6 Carbides in Martensitic Heat Resistant Steel
Mitsuru YOSHIZAWAMasaaki IGARASHITaiji NISHIZAWA
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2005 Volume 91 Issue 2 Pages 272-277

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Abstract

It is well known that tungsten (W) is the key element for creep strength of the advanced martensitic heat resistant steels developed for main steam pipe in ultra-super critical power plant. W is found to suppress coarsening of M23C6 type carbide during creep at elevated temperatures, which can never be predicted according to the conventional Ostwald ripening model for a Fe-X-C system in αFe. In this study, therefore, the effect of W on the coarsening of M23C6 during aging has been analyzed in a detailed experiment and modeled using a modified Ostwald ripening equation for Fe-X1-X2-C system. It is found that W substitutes only for Cr in M23C6 lattice to form [Fe4(Cr, W)19]C6. Using the modified Ostwald ripening equation the coarsening of M23C6 is found to be controlled by the lattice-diffusion of W, resulting in the coarsening rate reduced about one order of magnitude by 1% W addition.

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© The Iron and Steel Institute of Japan
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