Analysis of the precipitation behaviour in a high-speed steel by means of small-angle neutron scattering

Abstract

Small-angle neutron scattering (SANS) and energy filtering transmission electron microscopy (EFTEM) were employed to characterise the precipitation behaviour in the high-speed steel HS6-5-2 during tempering. With SANS the evolution of size, distribution, particle number density and volume fraction of the precipitates were determined. SANS data show that tempering at 590°C leads to at least three populations of precipitates. The smallest population is assumed to be Fe-rich carbides or carbon clusters. The intermediate-sized particles are either MC and/or M2C carbides but they cannot clearly be distinguished by SANS. However, the ratio A of magnetic to nuclear scattering intensity was used to gain information on the composition of the precipitates. Here, the A-value indicates a substitution of iron by carbide forming elements with increasing tempering time. The results obtained by SANS for the intermediate-sized precipitates correlate well with those achieved by EFTEM.