The State of the Art for Wire Arc Additive Manufacturing Process of Titanium Alloys for Aerospace Applications

Aerospace industries invest a significant amount of resources to meet one common goal, that is, to make the aircraft fly. To keep down its 'buy-to-fly' ratio, researchers have been working hard to introduce additive manufacturing (AM) technique for producing aerospace components. AM technologies are also now being used in major parts of an aircraft like fuel nozzles, turbofan blades, compressor-turbine blades, suspension wishbone, air ducts, etc., due to its just in time production with less complexity, direct tooling, and higher customer satisfaction with significant cost reduction including interior design. Nowadays, aerospace industries face problems meeting the deadline for delivering the aircraft components and replacement parts while maintaining certification standards. The wire arc additive manufacturing (WAAM) technique, one of the AM processes, can fabricate large metallic components with some reduction in lead time. WAAM process can build near net shape parts with high material deposition rate and efficiency while keeping the equipment and feedstock cost and material wastage minimal. This review paper summarizes the latest advancement on wire arc additive manufacturing of titanium and its alloy based on the aerospace application. Titanium and its alloys are used at a large scale in aircraft airframe structures and engine parts due to its high strength-to-weight ratio, excellent corrosion-resistant, high creep and fatigue resistance at an elevated temperature. It has been studied that the mechanical and metallographic properties of titanium and its alloy can be enhanced by using the WAAM process, and it is suited for aerospace applications. The paper will review the challenges like porosity, delamination, residual stress, crack propagation, anisotropic behavior, oxidation, etc., associated with the WAAM process on titanium alloys and propose recommendations for reducing the defects during the WAAM process.