Revolution in aircraft construction: Titanium residues are now being recycled for valuable purposes!

Revolution in aircraft construction: Titanium residues are now being recycled for valuable purposes!

The challenges in the production of titanium components are not only technical, but also ecological. During machining, which includes processes such as milling, turning and grinding, a significant proportion of the titanium raw material is lost as chips. It is estimated that these machining rates can reach up to 90 percent when machining large aircraft components. However, these waste chips, often considered worthless waste, could be put to new, promising use. This is the aim of the Return II research project at Leibniz University Hannover, whose goal is a closed material cycle for titanium components. The project is led by the Institute for Manufacturing Technology and Machine Tools (IFW), in cooperation with four industrial partners. The central concern is to convert the chips resulting from processing into high-quality titanium powder in order to significantly increase both resource and energy efficiency and also to drastically reduce CO2 emissions.

The current process chain shows clear deficits in terms of economic efficiency and resource conservation. Titanium chips are often contaminated by oxidation, cooling lubricant residues and tool particles, which makes recycling much more difficult. However, basic investigations as part of Return II have shown that these contaminations can be reduced through targeted adjustment of the process variables. Innovative processes could be used to produce high-quality solid titanium material from recycled chips, thereby avoiding the traditional, energy-intensive melting process. Instead, the aim is to introduce the chips directly into modern powder production processes such as atomization processes, which could not only reduce energy consumption but also CO2 emissions by up to 80 percent.

Recycling strategy and additive manufacturing

The Return II project has the challenge of developing a recycling strategy for titanium aircraft components and aims to use at least 70 percent recycled material in production. This strategy could save around 87.7 GWh of energy and 42 kilotons of CO2 in Germany. In addition, the transferability of this strategy to other materials is being investigated to achieve additional savings of around 16 GWh. The purity of the titanium material plays a crucial role, especially in aviation, where “Grade 5” quality is usually required. The integrated additive manufacturing method, such as selective laser melting (SLM), is promising. The consortium working on this project is made up of several research institutions and companies, including Leibniz University Hannover and DMG MORI Additive.

Another important player in the fusion of innovative manufacturing methods is Premium AEROTEC. This company has already pioneered the 3D serial production of complex titanium aircraft components. On April 11, 2019, the completion of an industrial process audit by Airbus paved the way for the overall process qualification of additive processes on multilaser systems. This means that expensive in-process samples can now be eliminated, making metallic additive manufacturing more cost-effective and leading to wider application in aviation. Since 2013, those responsible have recognized the possibilities of additive manufacturing and have undertaken intensive research efforts to optimize the process of “laser powder bed melting”.

The path to energy efficiency

The additive processes not only enable new possibilities in lightweight construction, but also the production of bionic structures that further increase efficiency. The close collaboration between interdisciplinary teams was crucial for the successful qualification of the new technology. Before implementation in civil aviation, high standards regarding process reliability, reproducibility and material quality had to be met. Several thousand material samples were tested as part of intensive investigations to ensure the quality and cost-effectiveness of the new processes. With a focus on resource conservation and sustainability, the combination of returning titanium chips into the production cycle and continuously improving additive manufacturing methods could represent a decisive step towards a more environmentally friendly future for the aviation industry.