Comportamento a fatica di acciai sinterizzati trattati termicamente.

To develop a material with high fatigue strength and acceptable machinability, unnotched and notched (Ksubt=1.0 and Ksubt=2.8) samples in the density 7.1 g/cbm made a Distaloy AB (Fe-1.75Ni-1.5Cu-0.5Mo) mixed with 0.5 % C and 0.5 % MnS in as-quenched and tempered states have been subjected to fatigue testing (axial loading, R=0,-1,-2). Three tempering temperatures (250, 300 and 350 degree C) have been investigated in order to optimize fatigue strength and machinability. The results of the fatigue and machinability testing have been discussed as a function of tempering temperature and compared to the results of previous investigations. The temperature of 300 degree C revealed to be the optimum tempering temperature, because it allows to obtain materials with acceptable machinability without substancial reduction of fatigue strength. Owing to their noticeable fatigue strength and low notch sensitvity these materials can be effectively used for the production of notched components subject ed to axial fatigue loading, like con-rods. However, owing to their relatively low ductility, the mean stress sensitivity results high and this has to be taken into account when designing.