Surface Layer Properties and Fatigue Behavior in Ti-6Al-4V: Comparing Results after Laser Shock Peening, Shot Peening and Ball-Burnishing

Rotating beam fatigue specimens of Ti-6Al-4V were mechanically surface treated, by various methods. Conventional shot peening (SP), ultrasound shot peening (USP), laser shock peening (LSP) and ball-burnishing (BB) were applied varying the main process parameters to a wide extent. The resulting changes in surface topography, micro-hardness-depth and residual stress-depth profiles were studied. Applying the same Al men intensity in USP and SP, the ball size being larger in USP compared to SP led to lower roughness values and slightly lower micro-hardness values in near-surface regions. However, the residual stress-depth profiles were very similar. LSP and BB led to penetration depths of plastic deformation and residual compressive stresses much greater than those observed on USP and SP specimens. On average, micro-hardness values in near-surface regions were somewhat higher in BB compared to LSP. Among the various mechanical surface treatments, ball-burnishing led to most marked fatigue strength enhancements.