Hybrid SLM/DED Additive Manufacturing of Ti6Al4V Advanced Fuel System Components for Aerospace Industry

Prolonged range capability of aircrafts is vital to shorten travel time, reduces flight and maintenance costs, has beneficial influence on the environment and furthermore improves the traveling comfort of passengers. This project ambitiously proposes a technological upgrade in the field of cost-efficient, high-quality additive manufactured (AM) components for aerospace industry, which cannot be achieved by conventional manufacturing methods. The main goal of the proposed project is the development of Hybrid AM Ti6Al4V advanced fuel system components which merges advantages of two AM technologies, selective laser melting (SLM) and directed energy deposition (DED). Hybrid AM technology enables rapid manufacturing of larger parts with geometrically complex structures, allows better customisation of products, building of hollow structures and therefore reduces weight of the parts, which is crucial in aerospace industry. This approach with significantly reduced buy to fly ratio is also time and cost effective and has the potential to approach Zero Waste due to the possible recycling of used powder materials. On the other hand, Hybrid AM is completely new technology, leaving many questions regarding microstructure, residual stresses, porosity and surface roughness opened. All these aspects need to be exposed in order to design as-built parts with desirable target properties. Our study is based on Ti6Al4V alloy, which is recognized as the leading titanium alloy in aerospace engineering industry due to its high strength, low density, high fracture toughness and superior corrosion properties. The unique thermal features of AM technology, such as rapid melting and resolidification, however profoundly affect microstructure, corrosion and mechanical properties of printed Ti6Al4V alloy. We will therefore focus on optimization of process parameters of both, SLM and DED AM techniques. To improve the ductility, reduce thermal stresses and to achieve superior mechanical properties of Ti6Al4V AM manufactured products suitable heat treatments will be assessed. Furthermore, surface plasma treatment will be employed to additionally improve corrosion resistance trough surface oxide layer thickening. All considered Hybrid AM components will be carefully reviewed, microstructures, corrosion and mechanical properties will be studied in order to obtain a comprehensive knowledge on mechanisms that control the desired properties. Microstructure will be characterized by using state-of-the-art SEM and TEM microscopes. EDS will be used for micro elemental analyses, EBSD for texture and phase analyses and ECCI (Electron Channelling Contrast Imaging) for the dislocation structure characterization. Static and dynamic mechanical testing will be performed to obtain information on the hardness, yield strength, tensile strength, elongation, impact toughness, fatigue and creep. Corrosion resistance will be studied by means of electrochemical and long-term immersion tests. X-ray photoelectron spectroscopy (XPS) will be used for qualitative and quantitative chemical analysis to obtain the information on oxidation state of each analysed element. The micro-scale focused ion beam (FIB) ring-core milling technique will be employed for the measurement of local residual strain and stress distributions. This novel concept of Hybrid AM technology has the ambition to form necessary basic know-how for the development of high-added value metallic products suitable for aerospace applications.