The aim of FANTASIA was to contribute towards winning global leadership for European aeronautics by developing new flexible and near-net-shape additive manufacturing chains and repair techniques using laser metal deposition (LMD) and direct laser forming (DLF) processes. These techniques, in combination with conventional manufacturing processes, provided the possibility to realise a breakthrough in the manufacturing of aero-engine parts. In particular, the following potential could be achieved:
- New design possibilities using the nearly unlimited geometrical freedom of DLF;
- Decrease time efforts in the whole life cycle of a part in the design and/or redesign phase, subsequent manufacturing and the repair phase;
- Savings in production and raw material costs due to reduced time effort and raw material quantity to be used in generative manufacturing;
- Processability of conventional nickel and titanium base alloys as well as upcoming advanced materials like TiAl and Udimet 720.
Three major aero engine and component manufacturers (OEMs), two repair excellence centres as end users, six industrial partners as systems engineering and powder providers together with seven universities and research institutes have joined their multidisciplinary expertise and resources in materials science, laser manufacturing technique and sensorics and in design, manufacturing and repair of aero engine parts in the FANTASIA proposal.
The main project objectives were:
- Development of process layout for LMD to achieve the required characteristics with respect to material, part quality and economy;
- First time development of process layout for DLF to achieve the required characteristics with respect to material, part quality and economy;
- Development of heat treatment cycles before and after laser treatment to get microstructures and thermal stress fields that meet the mechanical properties;
- Determination of static and dynamic mechanical properties of the laser-processed and heat-treated samples together with correlation of these properties with microstructure and stress fields;
- First time workout of acceptance plus a non-destructive test (NDT) inspection criteria for LMD and DLF process (correlations between tolerable defects, microstructure, mechanical properties and process parameters);
- Support of the process development by simulation of temperature, stress fields and microstructure formation to predict process parameters and build-up strategies;
- Development of equipment for LMD and DLF processes:
- processing heads, including powder feeding nozzles and shielding gas units for 3D processing
- process chamber for DLF software
- for Computer Aided Design / Computer Aided Manufacturing (CAD/CAM) integration
- sensors and systems for on-line process control;
- New manufacturing and repair chains by combining conventional (e.g. casting, milling, joining) and laser-based techniques (LMD, DLF).
This will minimise the cost and lead-time due to reduced market response times from manufacturing to design and design to manufacturing. The technology developed will trigger a quantum step in cost reduction for design or re-design, manufacturing and repair of new or existing aero engine parts.
The work was divided into work packages as follows:
In WP1, the test pieces and the additives for LMD and DLF were manufactured. The additives (powder and wire) were characterised.
The aim of WP2 was the FE modelling of LMD and DLF processes to generate input for the process development (WP3). The main focuses were the calculation of the temperature and stress fields, as well as the microstructure formation in dependence of process parameters and part geometry.
In WP3, the process layout for LMD and DLF were developed for different materials and part geometries. A further aspect in WP3 was the development of suitable heat treatment procedures after LMD and DLF processes.
In WP4, hard- and software for both techniques were developed, modified and tested.
For quality assurance and reliable LMD and DLF, process monitoring and on-line process control systems were developed and tested in WP5. The focus of this WP was the development of on-line process control methods.
Simultaneously with the process engineering in WP3, a geometrical and metallurgical examination of the test pieces was carried out in WP6.
In WP 7, test pieces from different materials for mechanical testing were fabricated with the suitable parameters determined in WP3.
To ensure the required and defect-free structure of the processed parts, non-destructive tests (NDT) had to be carried out (WP8).
Based on WPs 2-8, demonstration parts were repaired and manufactured in WP9 using the developed techniques and process chains. This work package included the heat treatment, the final machining, NDT inspection and the mechanical tests.
In WP10, a technical and economical assessment of the results were carried out. An additional essential aspect was working out the acceptance and NDT inspection criteria for LMD and DLF.
The EU-funded Project FANTASIA (Flexible and near-net-shape generative manufacturing chains and repair techniques for complex shaped aero engine parts) has demonstrated how selective laser melting (SLM) can be used to make both super strong and efficient complex-shaped aircraft engine components and repair damaged ones. Tests have shown that the quality of components produced using this method is equally as high (or better) than those manufactured using conventional processes.
Aircraft engine components must be lightweight yet strong enough to tolerate extreme conditions. They need to endure 1 000 rotations every second, withstand heat of up to 2 000°C, and meet stringent safety standards.
With SLM, the part is built one layer at a time, using a metal powder that is applied to the substrate and instantly melted into place with a high-power laser beam, creating a permanent bond with rest of the object.
Tests have also shown that manufacturing cycle times can be reduced by at least 40% using SLM and other laser-based generative methods. This would ultimately mean savings of a maximum of 50% of the material required, and a minimum of 40% of repair costs.
The results have indicated that the SLM approach is not, as yet, appropriate for use with every turbine material but that the team has already noted very good results with Inconel 718, a nickel-based superalloy, and with titanium alloys.
Summary of the results:
- LMD repair chains have been developed and have demonstrated their efficiency to repair large aero engines components:
- Outlet guide vanes made of In 718;
- SX shrouds made of Rene N with regaining the SX structure and minimised distortion.
- SLM manufacturing has also been shown to be of huge interest for the manufacturing of small complex parts:
- Process window and very good mechanical properties for In 718;
- Manufacturing of Inlet Guide Vanes made of Al Si10Mg with high dimensional accuracy and good mechanical properties.
There is still research that needs to be undertaken specifically on materials that are prone to cracking or splitting. The researchers are currently looking into ways of using melting or moulding to re-seal cracks developed by components during use. Engineers are also experimenting with ways to stop the cracking in the first place, such as by varying the laser output power or using beam geometry.
Currently, other areas of focus for the researchers are the effects that construction-platform preheating has on product quality, and the need to improve on the productivity of the method (with a coating thickness of between 30 and 100 micrometers, larger components can take too long to produce).