Analysis of microstructure and mechanical properties of additive repaired Ti-6Al-4V by Direct Energy Deposition

The recent advances in additive manufacturing have opened new possibilities in aerospace industry; ability to successfully repair turbine blades being one. Repair approaches with Direct Energy Deposition (DED) is one prospective method to overcome the drawback of Integrally Bladed Rotor (IBR/blisks) in its ability to repair damage; which would otherwise require full removal and either an expensive replacement or a complicated repair, for damage beyond a minor dent. In order to attend confidence in such repairs using Additive Manufacturing, the characterization of additively repaired specimen is necessary. Ti-6Al-4V specimens fabricated by DED using two different feedstocks (metal powder and wire) were investigated in this study. The test coupons consist of half-conventional and half additively manufactured (AM) material with a bond line at the center of the specimen gauge. The microstructural features (alpha lath thickness, colony size and prior beta grain size), tensile properties in relation with the microstructural characteristics and fatigue behavior of the built samples were characterized and compared with the 100% stock annealed Ti-6Al-4V coupons. Subsequent analyses of the fracture surfaces were conducted using Scanning Electron Microscopy (SEM) for evaluation of the failure mechanism and the presence of process defects and their impact on overall fatigue performance. The mechanical properties of the DED repaired Ti-6Al-4V were found to be slightly lower than the stock material in this study but compared favorably to published results of annealed Ti-6Al-4V.