IMPACT RESPONSE OF Mo PREALLOYED SINTERED STEELS DETERMINED BY INSTRUMENTED TESTING

摘要

The impact behaviour is one of the inherent weaknesses of sintered steels but on the other hand also a very sensitive indicator for the quality of interparticle bonding. In the present work, unnotched impact bars based on prealloy steel powder Fe-1.5% Mo were prepared, carbon content, compacting pressure, and sintering temperature being varied. In part, heat treatment by austenitizing, quenching and tempering was applied. Charpy impact testing using an instrumented pendulum hammer showed that there is a clearly positive correlation between dynamic maximum stress and yield stress on one hand and the displacement on the other hand for the effect of density and sintering intensity but a negative correlation for the effect of heat treatment, in the latter case higher density and/or sintering intensity rather increasing the stress values while in the as-sintered state the displacement grows. The carbon content has a significant effect in case of the sintered materials but hardly for the heat treated ones. Tempering in part changes the shape of the load-displacement curves, at least at high temperatures, but without too much effect on the integral impact energy.