On the fatigue behavior of medical Ti6Al4V roughened by grit blasting and abrasiveless waterjet peening

Flat fatigue specimens of biomedical Ti6Al4V ELI alloy were surface-processed by high pressure waterjet peening (WJP) without abrasive particles using moderate to severe conditions that yield roughness values in the range of those obtained by commercial grit blasting (BL) with alumina particles. Fatigue behavior of WJP and BL specimens was characterized under cyclical uniaxial tension tests (R=0.1). The emphasis was put on a comparative analysis of the surface and subsurface induced effects and in their relevance on fatigue behavior. Within the experimental setup of this investigation it resulted that blasting with alumina particles was less harmful for fatigue resistance than abrasiveless WJP. BL specimens resulted in higher subsurface hardening and compressive residual stresses. Specimens treated with more severe WJP parameters presented much higher mass loss and lower compressive residual stresses. From the analysis performed in this work, it follows that, in addition to roughness, waviness emerges as another important topographic parameter to be taken into account to try to predict fatigue behavior. It is envisaged that optimization of WJP parameters with the aim of reducing waviness and mass loss should lead to an improvement of fatigue resistance