Mechanical properties of new low-nickel cobalt-free maraging steels

Abstract

To study the mechanical properties of newly developed low-nickel cobalt-free maraging steels, six laboratory series with varied Ti, Mo, and Cr mass contents (0.003- 1.65, 0.0074- 5 and 0.004- 5 %) were studied. The study showed that increasing Ti and Mo contents improve the tensile strength and yield strength without affecting ductility markedly. The chromium alloyed grades M2, M6, M8 and M12 exhibit properties comparable to those of T 250 grade. To investigate the effects of heat treatment temperature on the mechanical properties, the solution treatment was carried out at temperatures varying between 820 and 1100 °C and holding times of 15 min at different cooling rates. The ageing temperature varied from 400 to 500 °C at ageing times of 60, 120 and 240 min, respectively. The ageing response of hardness as a function of temperature at different soaking conditions was determined to optimise the heat treatment conditions. The mechanical properties of the different steels after solution treatment and ageing at optimum temperature and time were determined.