Fraunhofer Institute for Production Technology IPTResearch project "ISEGRIM"
Additive repair technology for long-lasting fusion reactors
The economic future of fusion energy depends largely on the lifespan of the plasma-facing components (PFCs). These tungsten components are exposed to extreme thermal and mechanical stresses that lead to material erosion and structural damage. Replacement is costly and laborious.
In the research project “ISEGRIM – Identifying damage caused by erosion in the generator and regeneration of the material using LMD-w,” the project partners are developing a repair process that significantly extends the service life of the PFCs and thus improves the economic efficiency of fusion reactors. The new process is based on laser metal deposition with wire (LMD-w).
Optimized process overcomes challenges in processing tungsten wire
A key challenge in LMD-w is the wavy surface profile that results from the adjacent weld beads. To create a smooth, even layer with minimal roughness, the partners will develop an optimized cladding strategy that meets the required specifications for geometry and roughness – ideally without additional post-processing. At the same time, the process should ensure that the applied material is defect-free to prevent rapid material fatigue.
Processing tungsten wire presents particular challenges: The material has the highest melting point of all metals – about 2000 °C above that of steel – as well as a high brittle-ductile transition temperature. Due to its temperature resistance and low sputter rates, it is ideal for PFCs, but difficult to process additively.
In order to overcome these challenges, the partners will adapt the laser system to the properties of tungsten. Various laser systems and optical configurations are being tested. Coaxial wire feeding, for example, allows for direction-independent processing and increases process flexibility.
Process and plant engineering for tungsten cladding
Fraunhofer IPT is leading the FOWA (tungsten cladding manufacturing research) subproject. Previous investigations show that the laser-based processing of tungsten places specific demands on the system technology. Therefore, Fraunhofer IPT is analyzing the processes experimentally and optimizing the system configuration.
One central research topic is operating the LMD-w process under vacuum conditions. Oxidation is prevented and different temperature gradients occur compared to atmospheric conditions. The flexible vacuum system maps the real process independently of the actual ambient conditions in a fusion reactor. In subsequent use, a reactor vacuum can be maintained and complex protective gas control can be avoided.
The core of the project is the development of a specialized processing unit with an integrated vacuum unit, optimized optics and advanced sensor systems. This enables precise process control and reproducible, high-quality additive manufacturing.
Repair process will be demonstrated, plant concept will be analyzed
At the end of the project, there will be an optimized process for the high-quality and reproducible additive repair of PFCs. The process will be demonstrated and evaluated in terms of its industrial applicability and sustainability.
In addition, a system concept is to be developed that can be integrated into a fusion power plant. Taking into account current developments, the project partners will analyze and evaluate various technologies to implement the system concept and the process.
Funding
The ISEGRIM project is funded by the German Federal Ministry of Education and Research (BMBF).
Funding reference: 13F1006E
Project management agency: VDI Technologiezentrum GmbH
Project partners
- BCT Steuerungs- und DV-Systeme GmbH, Dortmund (Coordination)
- Forschungszentrum Jülich GmbH, Jülich
- Fraunhofer Institute for Production Technology IPT, Aachen
- LaVa-X GmbH, Herzogenrath
- Precitec GmbH & Co. KG, Gaggenau
- ALOtec Dresden GmbH, Kesselsdorf