Investigation of austenitic FeCrNi steels with regard to stacking-fault energy and thermal austenite stability

Abstract

The mechanical properties of face-centered cubic (fcc) metals are influenced by physical parameters of the material, such as the stacking fault energy (SFE). It is known that a low SFE improves the strain hardening, thus increasing the abrasive wear resistance over a wide temperature range. Therefore, investigating the SFE is highly important for the characterization of the physical properties of materials at elevated temperatures. In the present study, the SFE of several austenitic stainless steels was determined by using a calculation model based on Calphad data for investigating the SFE depending on temperature. It can be shown that the lowest SFE value was calculated for the system Fe-27Cr-22Ni including interstitial elements (C+N < 0.1 mass%). This constitution was found by increasing the Cr content to a maximum considering the thermal austenite stability. In this context, the influence on the SFE and austenitic stability of the main alloying elements (Cr, Ni) were examined in detail. To determine the SFE values experimentally, alloys were produced on a laboratory scale and analyzed using X-ray diffraction line-profile analysis (XRD-LP). The results show good match between the calculated and measured SFE values. The calculations show that an increase of the Cr/Ni ratio decreases the SFE in FeCrNi alloys. Moreover, the represented calculation model is suitable for estimating the SFE over a wide temperature range, avoiding costly and time-consuming experiments.