Fully Reversed Uniaxial Tension-Compression High Cycle Fatigue Behaviour of Shot-peened Steels

The effect of shot-peening on the uniaxial fatigue behaviour of four engineering steels, heat treated to a similar final hardness was investigated. Forged 0.39%C and 0.72%C steels, a quenched and tempered 0.51%C steel and a 0.50%C powder forged (PF) steel were fatigue tested under fully reversed (R=-1) push-pull loading conditions. Following long life (107) cycling, shot-peening had little effect on the fatigue limit of the 0.39%C and 0.72%C steels whereas the fatigue limit of the PF steel increased 10.4%. Conversely, the fatigue limit of the quenched and tempered steel decreased 12.0% after shot-peening. The results showed that the beneficial effects of shot-peening, such as compressive residual stresses and work hardening, balanced the effects of surface roughness since crack initiation tended to occur below the surface. Microhardness profiles showed that the greatest amount of cyclic softening in the shot-peened regions occurred in the hot rolled steels. Softening was accompanied by a decrease in the depth of surface hardness.