HIGH-CYCLE FATIGUE BEHAVIOR OF MO ALLOYED SINTERED STEEL

Low alloy PM steel Fe-1.5 %Mo-0.7 %C was prepared from elemental powde rs by pressing and sintering. Unnotched specimens were fatigue tested in the push-pull mode at 20 kHz up to N > 10(8). It showed that heat t reated materials offer better fatigue endurance strength than as-sinte red ones especially at high numbers of cycles. The total porosity lowe rs the fatigue limit, the relative decrease being quite similar to tha t found with PM iron. Sintering temperature and time also strongly aff ect the fatigue behaviour. For predicting the fatigue limit, the load bearing cross-section A(c) was found to be a well suited microstructur al parameter which can be measured in low-deformation fracture surface s.