Fretting fatigue characteristic of Ti–6Al–4V strengthened by wet peening

•We invented a new apparatus for the fretting fatigue tests.•The fretting fatigue property of Ti–6Al–4V was increased by wet peening treatment.•The hardness and residual stress synergistically retard the crack growing. This study investigated the effects of wet peening treatment on the fretting fatigue behavior and crack propagation in Ti–6Al–4V alloy. Wet peening induced a compressive residual stress at 0–160μm depth and enhanced the hardness at 0–80μm depth. Results of the fretting fatigue tests show that the fretting damage could efficiently reduce the fatigue life of both the un-peened and wet peened samples. Moreover, wet peening could effectively increase the fretting fatigue resistance. Investigation on crack propagation mechanism revealed that the increased resistance is due to the synergistic effect of the enhanced hardness and the induced compressive residual stress in the wet peening modified layer. The enhanced hardness could resist the local fatigue in the fretting cracking stage and the compressive residual stress could retard crack growth.