Precipitation kinetics in a 10.5%Cr heat resistant steel: Experimental results and simulation by TC-PRISMA/DICTRA

• Published in: Materials chemistry and physics 2017-10, Vol.200, p.342-353
• Main Authors: Sanhueza, J.P., Rojas, D., Prat, O., Garcia, J., Espinoza, R., Montalba, C., Melendrez, M.F.
• Format: Article
• Language: English
• Subjects: Boundary conditions; Carbides; Coarsening; DICTRA; Grain boundaries; Heat resistance; Heat resistant steels; Interfacial energy; Kinetics; Laves phase; Modeling; Nuclear electric power generation; Nucleation; Simulation; Steel; TC-PRISMA; TEM characterization
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2017.07.083

The precipitation kinetics of secondary phases in a 10.5%Cr heat resistant steel, designed by the authors, was studied experimentally and theoretically. Experimental data of nucleation, growth and coarsening stages for M23C6 carbides, V-MX, Nb-MX and Laves phase were obtained by HRTEM-characterization on samples after tempering (780°C/2 h) and isothermally aging for 1440 h and 8760 h at 650 °C. Theoretical studies of precipitation behavior of M23C6 and Laves phase were carried out by TC-PRISMA and complemented with DICTRA. A good fit between TC-PRISMA simulation and experimental results was obtained for M23C6 carbides considering a heterogeneous nucleation in grain boundaries, a semi-coherent interfacial energy of 0.3 J/m2, and decreasing the atomic mobility along grain boundary in order to include the effect of B. Experiments and simulation indicate a low coarsening rate for M23C6 carbides. Furthermore, precipitation of Laves phase at 650 °C was simulated by TC-PRISMA considering the effect of W and Si segregation at grain boundary, prior to the beginning of the nucleation and growth processes. Therefore, thermodynamic and kinetic boundary conditions were changed purposely in TC-PRISMA. Best agreement with the experimental results was obtained for an interfacial energy of 0.6 J/m2 and heterogeneous nucleation in grain boundary. [Display omitted] •Design, production and characterization of 10%Cr steel assisted by ThermoCalc.•Long term aging (8760 h) and TEM characterization of M23C6, MX and Laves phase.•Simulation of nucleation-growth-coarsening of M23C6 and Laves by PRISMA and DICTRA.•The effect of Boron on M23C6 carbides was satisfactory simulated by PRISMA.•PRISMA simulation of Laves Phase considering micrograin segregation of Si and W.