Titanium aluminide alloys for airplane components yield massive weight reduction Increasing global interconnectedness means more people and cargo are taking to the airways. Light-weight alloys and manufacturing technology will help make air transport greener, reducing fuel consumption and emissions. Industrial Technologies © AML (Sheffield) Ltd In 2016 alone, aviation contributed 3.6 % of EU-28 greenhouse gas emissions and the number of flights is expected to increase by 42 % from 2017 to 2040. Decreasing airplane weight is an important way to enhance efficiency and decrease environmental impact. The EU-funded MMTech project set out to reduce the cost and enhance the performance of low-weight gamma titanium aluminide (γ-TiAl) aerospace components to enhance uptake. Setting the bar high According to project deputy coordinator Dr Rosemary Gault, “Our key objectives were to reduce the cost and time required to produce γ-TiAl components by 45 %, to reduce maintenance costs of aerospace components by 8 %, to extend their service life by 15 %, to halve their weight and to reduce the amount of raw material use by 20 %.” γ-TiAl alloys are lighter weight and more resistant to corrosion than their conventional nickel counterparts and perform well at high temperatures and pressures. However, their extreme brittleness at room temperatures has made manufacturing challenging. MMTech was determined to find a solution. Overcoming barriers to achieve a wealth of benefits MMTech developed innovative low-cost powders to be used in additive manufacturing (AM) processes. However, although low-cost high-energy ball-milled (HEBM) powders had been shown to work on powder bed machines, they led to parts with increased porosity and cracks on the blown powder machine used in the project. “We had identified the risks at the start of the project and had good mitigation plans in place. When one of the technologies did not deliver as planned, the other partners all rallied round and put in a lot of additional effort and research to help us reach our goals,” Gault recalls. MMTech boosted machining research, carrying out work on different AM machines and supporting it with multi-scale models of the process chain. This led to the definition of a new machine architecture built to reliably deposit the new material. In addition, researchers improved machining processes with the use of active and passive damping during machining and the development of bespoke milling tool geometries and best parameters (cutting speeds and feeds, tool coatings, lubrications strategies) for machining. Delivering results Technologies were demonstrated in a generic aerospace blade, an automotive exhaust flange and a turbine impellor (used to decrease the pressure and flow of fluid) for an electric aircraft range extender. In all three cases studies, γ-TiAl reduced component weight by around 45 %, certain to have important impact on fuel consumption. Boeing has indicated that saving 1 % of fuel on a Boeing 737-800 would reduce annual fuel consumption by 100 metric tonnes, resulting in a 318.7 tonne decrease in CO2 emissions alone as well as significant decreases in other pollutant emissions. As Gault explains, “Equally importantly, using gamma titanium reduced part cost and production time by 45 % and 10 %, respectively, for the blade and around 80 % and 64 %, respectively, for laser-cut automotive exhaust flanges. MMTECH has demonstrated our partners’ cost-effective ways of making aerospace components from advanced materials, halving their weight and reducing C02 emissions.” That is good news for the aerospace industry and for the environment. Keywords MMTech, cost, weight, emissions, gamma titanium aluminide (γ-TiAl), aerospace, fuel consumption, additive manufacturing (AM), machining, blade, cost-effective, automotive exhaust flanges
