Tempering effects on the tensile response and fatigue life behavior of a sinter-hardened steel

The mechanical behavior of a sinter-hardened steel has been evaluated for different tempering conditions. Microstructural changes, as a consequence of the post-sinter-hardening treatments, were found to significantly affect the hardness, tensile stress–strain response and high-cycle fatigue resistance of the material. Optimum tempering parameters were found to depend strongly on the service conditions: monotonic or cyclic loading. The material behavior is discussed and rationalized considering: (1) sintering necks as the load bearing units of the sintered material, (2) the role of pore tips as micronotches on these connecting regions, and (3) notch effects (strength, ductility and fatigue sensitivity) at the local level of sintering necks as critical for controlling the macroscopic mechanical properties.