Influence of molybdenum on austempering behaviour of ductile iron Part 3 – Austempering kinetics, mechanical properties, and hardenability of ductile iron containing 0·25%Mo

Abstract

Austempering kinetic measurements and mechanical property measurements are reported for an iron containing 0·25%Mo, 0·25%Mn, and 0·25%Cu (all wt-%) for austenitising temperatures of 870 and 920°C and austempering temperatures of 400, 375, 320, and 285°C. The measurements are compared with similar measurements for an iron containing 0·13%Mo. The comparison shows that increasing the Mo content from 0·13 to 0·25% to increase hardenability delays the stage I reaction slightly but the processing windows remain open for all the austempering temperatures studied for an austenitising temperature of 870°C and all grades of the ASTM standard can be satisfied. The hardenability of the 0·25%Mo iron can be increased further by increasing the austenitising temperature from 870 to 920°C. This delays the stage I reaction particularly at higher austempering temperatures but all the processing windows remain open and the ASTM standard is satisfied.