On the effect of carbon content and tempering on mechanical properties and stiffness of martensitic Fe–18.8Cr–1.8B–xC high modulus steels

We studied the effects of C concentration (0.1, 0.3 and 0.5 wt%) and tempering temperature (100–700 °C) on the dynamic Young's modulus, mass density, hardness and impact toughness of quenched and tempered martensitic Fe–18.8Cr–1.8B (wt.%) based high modulus steels. Increasing C concentration lead to consistent hardness levels above 600 HV5 for tempering temperatures below 500 °C. While the tensile strength could be adjusted tailored from about 1000 MPa to more than 2000 MPa depending on the tempering temperature and respective C concentration, dynamic Young's modulus and mass density were left virtually unaffected. The E/ρ ratio shows little variability between approximately 31.2–33 GPa g−1 cm3, which is superior to conventional high strength steels and comparable to ferritic Fe–Cr–B steels without carbon additions. Particles identified within the martensitic matrices are mainly (Fe,Cr)2B type borides stemming from solidification, as well as an increasing fraction of (Fe,Cr)23(C,B)6 carbo-borides with increasing C content and tempering temperatures.