Determining hot deformation behavior and rheology laws of selected austenitic stainless steels

Abstract

Due to their versatile properties, austenitic stainless steels have a wide application potential, including in specific fields, such as the nuclear power industry. ChN35VT steel is a chromium–nickel– tungsten type of steel stabilized by titanium, and it is suitable for parts subjected to considerable mechanical stress at elevated temperatures. However, the available data on its deformation behavior at elevated/high temperatures is scarce. The core of the presented research was thus the experimental characterization of the deformation behavior of the ChN35VT steel under hot conditions via the determination of flow stress curves, and their correlation with microstructure development. The obtained data was further compared with data acquired for 08Ch18N10T steel, which is also known for its applicability in the nuclear power industry. The experimental results were subsequently used to determine the Hensel-Spittel rheology laws for both the steels. The ChN35VT steel exhibited notably higher flow stress values in comparison with the 08Ch18N10T steel. This difference was more significant the lower the temperature and the higher the strain rate. Considering the peak stress values, the lowest difference was ~8 MPa (1250 ◦C and 0.01 s−1 ), and the highest was ~150 MPa (850 ◦C and 10 s−1 ). These findings also corresponded to the microstructure developments—the higher the deformation temperature, the more negligible the observed differences as regards the grain size and morphology.