19.06.2006 Pressing & Sintering

Evaluating the Effects of Mass and Density on the Sinterhardening Response of Different PM Steels

The sinterhardening response of PM steels is affected by many factors, including the alloy system, the cooling rate, density, and component size. In this paper influence of mass and density on the response to sinter hardening has been investigated for some PM steels. Micro structural transformations, macro hardness and plane bending fatigue performance of un-notched and notched specimens have been evaluated. It is shown that the performance is highly depending on both surface hardness but also strongly on the martensite gradient in the part. Higher amount of martensite in the surface induces compressive residual stresses that are beneficial for the fatigue performance. The effect is more pronounced for notched materials compared to un-notched and this strongly compensates for the raised stress in the notch root. This information is of great value for selecting optimal sinter hardening material and processing parameters for a given application.