Advanced X-ray and neutron experiments at Paul Scherrer Institute PSI and Deutsches Elektronen-Synchrotron DESY have shed light on how microstructures form in additively manufactured materials for future fusion reactors. The research reveals how, during 3D-printing, unwanted phases arise at the interfaces between different metals – and how these can be influenced by the printing process. The findings are important for understanding how stresses can develop in components and optimising their design.
Additive manufacturing is considered a promising technology for producing components for future fusion reactors. Metal 3D-printing makes it possible to create complex structures, for example breeding blankets or divertors – key components of a fusion power plant. These materials must withstand extreme conditions: high temperatures, strong mechanical stresses and intense radiation. Crucial to their ability to do so is the material microstructure, which develops during the printing process.
Interfaces between tungsten and steel in focus
For 3D-printed components, tungsten is one of the metals particularly well suited to parts exposed to the hot plasma of nuclear fusion reactors. Steels serve as structural materials.
Researchers from Paul Scherrer Institute PSI and Deutsches Elektronen-Synchrotron DESY investigated samples made of tungsten in combination with a special stainless steel with a characteristic microstructure. The samples were produced using a metal 3D-printing technique known as laser powder bed fusion. In this technique, metal powder is melted layer by layer using a laser and then rapidly solidified, gradually creating a 3D structure.
At the interface between the two materials, complex microstructures can form during the printing process and influence the properties of the components. Using high-resolution X-ray techniques, the team could investigate the crystal structure and distribution of chemical elements within these interface regions to micrometre resolution.
The measurements revealed that an unwanted intermetallic phase made of iron and tungsten forms at the interface. Such phases are detrimental for mechanical stability and potentially also for irradiation resistance of components. The unwanted phase could, they showed, be significantly reduced by adjusting the printing process.
Read more on the PSI website
Image: Material scientist Malgorzata Makowska at the microXAS beamline of the Swiss Light Source SLS
Credit: © Paul Scherrer Institute/Mahir Dzambegovic