EFFECT OF RAPID SOLIDIFICATION AND HEAT-TREATMENT ON D2 STEEL

Chill block melt spinning has been employed to produce rapidly solidified (RS) ribbons of D2 steel (in wt% 1.7 C, 12.0 Cr, 0.69 V, balance Fe) and the effect of melt-spinning parameters on ribbon geometry has been studied. Microstructure and phases have been examined using SEM, XRD and magnetic measurements. In addition to a substantial refinement of grain size and of carbide precipitation, RS suppresses martensitic transformation and produces a supersaturated austenite phase. The effect of isochronal (1 h) heat treatment (623 to 1073 KA) has been evaluated using Vickers microhardness measurements. It shows that RS imparts to D2 steel the ability to age-harden. The peak ageing in 1 h occurs at 833 KA with an apparent activation energy of 225 kJ mol-1 estimated by differential thermal analysis. The aged ribbons are found to contain M7C3, M23C6 and Fe3C in a ferritic matrix