Effect of Boron in the Coarsening Rate of Chromium-Rich Carbides in 9%–12% Chromium Martensitic Creep-Resistant Steel: Experiment and Modeling at 650 °C

Abstract: In this study, three martensitic creep-resistant steels with 100, 90, and 70 ppm of boron were investigated. The experimental data obtained from isothermal aging and creep test at 650 °C were compared with the results of simulation conducted using TC-PRISMA software. Tungsten was found to be the rate-controlling element in the coarsening of (Cr, Fe, W)23C6 carbides; however, this result differed in terms of boron-containing steel. Several studies indicate that the low solubility of boron in ferrite promotes boron enrichment in (Cr, Fe, W)23C6 carbide, thereby reducing its coarsening rate. However, this mechanism is not universally agreed upon. In the present study, a comparison between experimental and theoretical results revealed that in boron-containing steels, the coarsening of (Cr, Fe, W)23C6 carbide is controlled probably by boron volume diffusion or by trans-interface diffusion. Graphic Abstract: [Figure not available: see fulltext.] © 2020, The Korean Institute of Metals and Materials.