Study on fatigue crack growth behavior of the TA15 titanium alloy repaired by laser deposition

Laser deposition repair was employed to repair the body and surface of the forged TA15 titanium alloy. Subsequently, the fatigue crack growth behavior of the repaired components after annealing was investigated. The results showed that the fatigue crack growth rate (FCGR) of the body-repaired specimen decreased from the initial cracks in the heat-affected zone (HAZ), interface, and repaired zone (RZ). The increase in the repair layer thickness drastically reduced the FCGR in the surface-repaired specimen. The main crack growth mode was crossing the primary α and transformed β in the substrate zone (SZ), primarily crossing the lamellae α and along lamellae α in the HAZ, and crossing the lamellae α in the RZ. The RZ developed a tighter bond with the substrate interface, making crack growth more difficult. Crossing the lamellae α in the basket-weave structure required higher amount of energy and exhibited significant increase in tortuosity. Hence, the FCGR of the initial crack within the RZ exhibited the lowest rate. An increase in the thickness of the repair layer increased the proportion of the basket-weave, improving the resistance against crack growth, and increased the tortuosity associated with the crack path, reducing the FCGR. It was confirmed that the proposed body and surface repair methodology improved the FCGR of investigated specimens.