Modelagem Microestrutural De Aços Martensíticos Resistentes Ao Calor Para Aplicações a 650°c Com Suporte De Cálculos De Equilíbrio

Abstract

Precipitation of large Z-phase particles, Cr(V, Nb)N, replacing fine MX carbonitrides, Nb(C,N) or V(N,C), has recently been identified as a major cause for premature losses in long-term creep strength in high chromium martensitic steels for power plants applications. For developing a new heat-resistant steel with better creep performance for applications in modern power plants with service temperatures around 650 °C, martensitic steels with 9 wt.%Cr were studied to achieve a chemical composition without the presence of a reversion/formation of detrimental Z-phase from consumption of thermally stable carbonitrides. The alloy composition was design to control deleterious Z-phase precipitation based on extrapolation of conventional vanadium content. The modelling of the alloy content is relied on thermodynamic equilibrium calculations using MatCalc software and Schaeffler modified diagram to achieve a fully martensitic microstructure.