Tensile and fatigue behaviour of sinter hardened Fe-1.5Mo-2Cu-0.6C steels

In the present work the tensile and axial fatigue behaviour of sintered hardened Fe-1.5Mo-2Cu-0.5C at three density levels (6.8, 7.0 and 7.2 g cm(-3)) have been studied. The materials were tested under the as sintered condition, and after tempering at 180 and at 240 degrees C. The results show that steels under the as sintered condition posses a high hardness but a brittle tensile deformation and fracture behaviour. Tempering at 180 and 250 degrees C induces the disappearance of brittleness and tensile fracture is thus ductile although very localised at the necks. Fatigue strength is determined by the resistance of the materials to the internal damage evolution due to the nucleation of small cracks at the pores edges, and their coalescence into a long crack. Tempering induces an increase in the fatigue resistance. The greatest fatigue strength at 2 x 10(6) cycles is displayed by the steel with a density of 7.2 g cm(-3) and tempered at 180 degrees C.