Residual stress distribution and surface geometry of medical Ti13Nb13Zr alloy treated by laser shock peening with flat-top laser beam

The metallic implants made of Ti13Nb13Zr alloy are usually used under the action of the cyclic loads conditions and fatigue failure occurs occasionally. Laser shock peening (LSP) is an innovative surface treatment process, which has been used to improve the fatigue life of metallic materials. The present research was performed on the Ti13Nb13Zr alloy subject to laser modification in order to determine the effects on the residual stress distribution and surface geometry. A neodymium doped yttrium lithium fluoride (Nd: YLF) pulse laser with a flat-top beam was applied at three different overlapping rates (10%, 30%, 50%), laser pulse energies (5J, 6J, 7J), and impact times (1 impact, 2 impacts, 3 impacts), respectively. The residual stresses were determined by X-ray diffractometer with sin 2ψ method. Firstly, the 30% overlap was chosen by comparing the residual stresses induced by LSP with different overlapping rates. Then, the effects of laser energies and impact times on surface residual stresses, in-depth residual stresses, surface deformation, and surface roughness were investigated and compared. The results showed that the residual stresses, surface deformation, and surface roughness increase with the increasing laser energies and impact times. The effected layer depth of residual stress is about 1058 μm with the 6J laser energy.