The improvement of fatigue behaviour of sintered steels by surface rolling

In this investigation fatigue-life curves of two low- and high-strength powder metallurgy steels Fe-1.5Cu (rho is equal to 7.15 g cmhighminus3) and Fe-8.0Ni- 1.0Mo-0.5C (rho is equal to 7.35 g cmhighminus3) are compared for three different notch factors in as- sintered and surfacerolled conditions under constant- amplitude loading as well as under variableamplitude loading. The results are interpreted on the basis of the microstructural features, microhardness and residual-stress distributions. Statistically based design data are presented for the improvement of the fatigue strength by surface rolling of powder metallurgy parts taking into account the stress concentration and loading mode.