Numerical modelling and validation of precipitation kinetics in advanced creep resistant austenitic steel

Abstract

The austenitic steel Sanicro 25 is one of the most promising austenitic steels for the application in superheater tubes in coal fired thermal power plants. In this work, the microstructural evolution of this material during heat treatment and thermal ageing has been investigated. The investigations were carried out by light microscopy (LOM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). Scheil calculations were carried out by thermo-kinetic software MatCalc to analyse the solidification process which indicates Nb(C,N), Cr2N and Laves phase in the melt. Long term precipitation calculations predict the formation of five precipitate types in Sanicro 25: M23C6, Z-phase, Nb(C,N), Laves and Cr2N. Phase fractions and mean radii evolution of precipitates were calculated and compared to the experimental results. Calculated precipitate evolution shows good compliance with experimental data.