Study of the mean size and fraction of the second-phase particles in a 13% chromium steel at high temperature

Abstract

The mean size and fraction of the second-phase particles in a 13% chromium steel are investigated, while no plastic deformation was applied. The results of the measurement are compared with the modelling results from a physicallybased model. The heating sequence is performed on samples using a Gleeble thermo-mechanical simulator over the temperature range of 850-1200°C. Using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), the size distribution and composition of the carbides were evaluated, respectively. For obtaining particle size distribution (PSD), an image-processing software was employed to analyse the SEM images. Additionally, the relation between the 2D shape factor and size of the particles is also studied at different temperatures and most of the particles turned out to have a shape factor close to two. In order to measure the carbide weight fraction, electrochemical phase isolation was employed. The Ms and fraction of the martensite phase after quenching of samples are calculated and the results were comparable with the measured hardness values at corresponding temperatures. The measured hardness of the samples is found to comply very well with the measured mean size of the precipitates. The calculated mean size of the particles from the model shows very good agreement with both hardness value and experimentally measured mean size, while the calculated volume fraction from simulation follows a slightly different trend. ARTICLE HISTORY

Modeling precipitation kinetics in multicomponent alloys during deformation

“…The volume fractions that have been back calculated from Safara et al in their second work (Safara et al, 2020) while calibrating their hardness equation to their experimental measurements are 1.3%, 1.6%, and 0.3% at 900, 1,000, and 1,100 °C, respectively. These values were obtained without any plastic deformation, but they were determined using the ratio f/r m obtained with plastic deformation.…”

“…In this work, we investigate the microstructural evolution of chromium steel subjected to a thermomechanical treatment simulating hot compression. The steel, with the composition given in Table 1, has previously been experimentally investigated by Safara et al (2019) and Safara et al (2020) by means of a Gleeble thermomechanical simulator, hardness measurements, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The non-isothermal thermomechanical treatment applied consists of cooling from the austenitization temperature, 1,250 °C, with a rate of 5 °C/s down to holding temperatures (900, 1,000, and 1,100 °C).…”

“…Table 2 gives the evolution of the ratio between the volume fraction and mean size of precipitates, as estimated by Safara et al (2019). In addition, in a second work, Safara et al (2020) performed the Gleeble test on the same steel and with the same thermal profile but without plastic deformation. The holding at the holding temperature was stopped after 15 s in order to experimentally characterize the microstructure of the steel right before the deformation in comparison to their first work.…”

“…In this work, we, therefore, use the expression of the dislocation density evolution, as given by Engberg and Lissel (2008). The main equations of the set of equations are given, but for more information regarding their derivation refer to Safara et al (2019), Safara et al (2020), andSafara Nosar (2021). The dislocation density rate is then expressed as follows:…”

“…The parameters related to the micromechanical model that are necessary in Eq. 12, are taken from Safara et al (2019), Safara et al (2020), andSafara Nosar (2021). The molar volume and lattice parameter are extracted from a thermodynamic database (TCFE12, 2022).…”