Fatigue behavior of a high density powder metallurgy steel

Rotating bending fatigue tests were carried out on a high density Fe–2%Ni based powder metallurgy steel at 50 Hz frequency and at room temperature. The material was subjected to high cycle fatigue to evaluate endurance/fatigue limit and its influence on heat treatment/microstructure. The fractured fatigue surfaces were examined using scanning electron microscope to study the mechanism/s associated with crack propagation. Optical microscopy was carried out to characterize the microstructures resulting from different heat treatments. The microstructure was observed to have an influence on endurance/fatigue limit. As-sintered material exhibited the lowest endurance/fatigue limit when compared with the material in the hardened and tempered condition. Electron microscopy studies demonstrated the mechanism/s of crack linking and/or interconnection of pores characterizing the crack propagation. It has been observed that, by carefully designing the heat treatment the high density powder metallurgy steel can be beneficially used in fatigue loaded components.