Improved rotating bending fatigue performance of laser directed energy deposited Ti6Al4V alloys by laser shock peening

Abstract

A major challenge for additive manufactured titanium blades is to improve an unfavorable fatigue life. In this work, the rotating bending fatigue test was carried out on the laser direct energy deposited (L-DED) titanium alloy to simulate the service condition of the rotating blade, and the laser shock peening (LSP) post-processing was adopted to enhance the fatigue performance. The results showed that LSP induced gradient layer and phase transformation in L-DED Ti6Al4V alloy, and increased the fatigue limit to 570 MPa. The compressive residual stress dominated the crack source transfer confirmed by the finite element method, and its retention capacity under fatigue cycles reduced the semi-elliptical crack growth rate. A fatigue limit prediction formula was established to quantify the contribution of microstructure, residual stress and roughness changes.