The effect of temperature and strain rate on the mechanical properties and microstructure of super Cr13 martensitic stainless steel
Hamed Aghajani Derazkola, Eduardo García, Alberto Murillo-Marrodán, Jens Hardell
Abstract
In this study, the formability of super Cr13 martensitic stainless steel (MSS) is examined by means of hot tensile tests at different temperatures (900 o C–1100 °C) and t strain rates (0.01s −1 -10s −1 ). The potential effect of strain rates and temperatures on the mechanical properties, microstructure and fracture surface of super Cr13 MSS were examined. The post-test analysis, which includes hardness measurements, X-ray diffraction (XRD), fracture analysis by scanning electron microscope (SEM), and Energy-dispersive X-ray spectroscopy (EDS), was carried out. Results show that ultimate tensile stress (UTS) decreases with temperature, this way, the highest UTS was obtained at 900 o C-10s −1 (187 MPa), while the lowest UTS (38 MPa) was obtained in the 1100 o C-0.01s −1 sample. By contrast the elongation of the material increases with strain rate, since the elongation of the sample at 900 o C-10s −1 was near 16% and the elongation of the sample at 1100 o C-0.01s −1 was 57%. The XRD and EDS analysis indicated that Cr 23 C 6 and Cr 2 N are formed inside the microstructure of samples tested between 900 °C and 1000 °C, and these carbides are dissolved above 1000 °C. Temperature affects also retained austenite which increases with temperature. Fractography analysis indicated that the δ-ferrite phase has a primary role in high-temperature rapture. Fracture surface evaluation of samples revealed semi-ductile fracture behaviour below 1000 °C and low strain rates, while ductile fracture was detected on the tensile samples at temperatures higher than 1000 °C and high strain rates. Furthermore, the ductility of super Cr13 MSS was increased by increasing strain rate.