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MMTech Report Summary

Project ID: 633776
Funded under: H2020-EU.3.4.

Periodic Reporting for period 1 - MMTech (New aerospace advanced cost effective materials and rapid manufacturingtechnologies)

Reporting period: 2015-05-01 to 2016-10-31

Summary of the context and overall objectives of the project

Gamma Titanium Aluminides, γ-TiAl, are promising materials for aerospace applications because they perform well at the high temperatures found in engines and are lighter than the nickel alloys currently in use. They have a number of attractive properties, including high-temperature strength, good resistance to oxidisation and corrosion as well as low density. However, they are also expensive, with low ductility, low fracture toughness and are inherently brittle. The various alloys are expensive and are hard to obtain, so machining complex components from a large block of material is unattractive. Making parts using near-net techniques such a rapid manufacture (RM) uses less material, but has its own problems. Powder is expensive and properties can vary across suppliers and even between batches, meaning that parameters need to be set for each new build. Near net parts also need machining, but because γ-TiAl is brittle at low temperatures, it is extremely hard to finish-machine the components without producing cracks. MMTECH will develop methods of creating stable, consistent powder batches and investigate adaptive manufacturing techniques which can automatically vary deposition and machining parameters based on information gained during manufacture. It will look into softening the material with lasers to reduce cracking. γ-TiAl has the potential to save cost and time across the whole aircraft lifecycle, including design, production, maintenance, overhaul, repair and retrofit.
MMTech will focus on sustainable introduction of γ-TiAl into aerospace applications to:
♣ Reduce the production cost of γ-TiAl parts by 45% by reducing waste and scrap
♣ Reduce production time of γ-TiAl by 55% by reducing scrap
♣ Reduce maintenance costs by 8% through the use of -TiAl
♣ Target component weight savings of 20-50% through the use of γ-TiAl
♣ Reduce raw material use over the life of the component by 20%
♣ Extend component service life by 15%
These goals will be achieved by meeting a number of technology challenges to make it more cost effective:
♣ The production of powders with stable physical properties
♣ The reduction of rapid manufacturing costs
♣ The improvement of machining processes
♣ The development of multi-scale models of the manufacturing process chain

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

A number of case studies have been chosen to ensure industrial relevance. These are a turbine blade and two parts of an electric vehicle range extender - the turbocharger and the manifold and pipes. Data for the current manufacturing methods and performance of these parts has been collected which will form a baseline with which to compare the MMTECH results.

Mechanical alloying is being used to create powders with stable properties; this is being developed in tandem with a quality management procedure. This will lead to an effective production route for the powder and process output will be maximised. In the first period, the material variants to be used in the project and the powder production steps were defined, the process was set up and post-processing equipment and raw materials were selected. The first two material variants were produced, characterized and delivered for testing, with a further batch being sent later. Improvements in powder production yield were achieved by refining the manufacturing process. Two powder recycling strategies were tested, with positive results and a yield of over 70% was achieved. The best source of low-cost, high-quality input material was determined bearing in mind the sensitivity of the γ-TiAl powders to the input. Cold uni-axial pressings were done to provide material of the right chemical composition for machining trials.

Rapid manufacturing challenges include producing dense builds with no cracking and the development of robust parameters. Work done includes the specification of a number of test parts (blocks for microstructural and mechanical testing, larger samples for machining and a part composed of features extracted from the case studies), the characterisation of the new powders and initial test builds. A powder deposition head with higher laser powder has also been developed.

For finish machining, information on the powder and part-properties from the previous steps and novel machine tool set-ups will be required. Different combinations of machine tool features, cutting tools, cutting conditions and lubrication methods were investigated to allow right-first-time machining of the parts. In this period, the machinability requirements of the end-users were determined. The problems which may be encountered when machining γ-TiAl were identified, and the most appropriate machine tool, sub-systems and accessories chosen. These include high-pressure cooling, laser-assisted machining, virtual milling, collision detection and automatic inspection cycles which are being developed in the project. Reliability and maintenance analysis for the chosen machine is underway. Initial cutting trials were carried out using commercially available γ-TiAl to form a benchmark. These showed good tool-life, but the surface integrity was not of sufficient quality for aerospace applications.

Advanced multi-scale modelling techniques are being developed to support the optimisation of the process chain. The entire manufacturing processes is being modelled at a number of scales, and the models linked to create an overall systems model. This can be used to support the optimisation of part quality and to predict material deformation behaviour and microstructure under difference manufacturing conditions. To date, the additive manufacturing machine has been analysed along with the possible physical phenomena which take place during process. The process chain has been defined, along with all the inputs and outputs, and phase field and crystal plasticity finite element models have been created to predict the microstructure of γ-TiAl AM parts. The 2D laser-assisted process has also been modelled.

A self-adaptive and intelligent machining process is being developed for finish-machining of the part and will include strategies such as high speed machining, laser assisted machining, novel mechatronic devices and advanced solutions for vibration compensation. The adaptive controller has been defined and a chatter detection algorithm selected. Simulations have been carried out, which will be verified in the next period. Low and high frequency damping strategies have been investigated. A number of tool coatings have been investigated, along with polymeric concretes which can be used to passively damp machine tools. A tuned mass damper is also being developed.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

MMTech will focus on sustainable introduction of γ-TiAl into aerospace applications to:
o Reduce the production cost of γ-TiAl parts by 45%
o Reduce production time of γ-TiAl by 55%
o Reduce maintenance costs by 8%
o Target component weight savings of 20-50% using γ-TiAl
o Reduce raw material use over the life of the component by 20%
o Extend component service life by 15%

It is too early in the project for any impacts to have been reached. The work in this period has focussed on determining applications for γTiAl and on benchmarking existing manufacturing methods for these applications. The powder manufacturing route of gamma-TiAl alloy by mechanical alloying has been defined and its optimization is in progress, addressing specific powder properties suitable for AM processes.

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