ON THE ANNEALING OF RAPIDLY SOLIDIFIED HIGH CHROMIUM-HIGH CARBON TOOL STEEL

摘要

In this paper, a systematic effort was made to study the effect of cooling rate and undercooling on carbide precipitation after annealing rapidly solidified (RS) high chromium-high carbon tool steel. Rietveld analyses on XRD and neutron diffraction data on rapidly solidified powders showed an expansion in lattice parameter of retained austenite to 0.3615nm due to supersaturation of carbon and chromium during rapid solidification. The effect of isochronal annealing on the RS powders was evaluated using Vickers microhardness measurements. The fraction of austenite transformed to ferrite at different annealing temperatures (from 350°C to 810°C) was also calculated using Rietveld analysis technique. Using high resolution SEM images, results of measurements taken on the size and fraction of precipitated carbides as a function of cooling rate and undercooling will be reported. Effect of degree of supersaturation on the nucleation and growth of precipitates will be discussed.