Shot Peening of Sintered Steels: Effect of Density and of the Diffusion Bonded Ni on Surface Modification and on the Contact Fatigue Resistance

摘要

In a previous work it has been demonstrated that shot peening improves the contact fatigueresistance of a Cu-Mo diffusion bonded sintered steel by 30%. Such an improvement is due to thecombination of compressive residual stresses, surface densification and strain hardening. By means of atheoretical model to predict contact fatigue crack nucleation, it has been concluded that the effect ofphenomena related to plastic deformation (surface densification and strain hardening) prevails on that ofresidual stresses. In the present work, the study was extended to other materials, having a lower resistanceto plastic deformation resulting from either a lower density or the presence of diffusion bonded Ni. Even inthis case, shot peening improves the contact fatigue resistance but surface modifications related to plasticdeformation are enhanced in comparison to the Ni-free steel with a higher density. As a consequence,compressive residual stresses are smaller. The theoretical model was applied and the effect of theresistance to plastic deformation of the base material on the improvement of the contact fatigue resistance isdiscussed.