Alongside international project partners, a team of scientists from the Fraunhofer Institute for Production Technology (IPT), Aachen, Germany, reports the development of a hybrid variant of laser buildup welding in the recently completed ‘MatLaMeD’ research project, in which wire and powder are processed simultaneously. By adding hard material particles in powder form to the wire material, the team succeeded, for the first time, in selectively adjusting important material properties of the applied layers. The process is reported to be significantly more cost-effective than a pure powder process and offers greater material flexibility than a pure wire process.
To identify the best combinations for different applications, the scientists tested numerous materials. As wire materials for the practical test series, a hot-work tool steel with good structural stability and an easily welded low-alloy steel were selected. As powder materials, the team opted for chromium (Cr) as a carbide-forming and grain-refining element and titanium carbide (TiC) as a hard phase in the test series.
By combining wire and powder, the researchers were able to flexibly adjust the material composition for each application. The addition of the powder material made it possible to selectively change the microstructure of the tool steels and increase the hardness of the applied coatings; even the addition of small amounts of titanium carbide led to hardness increases of up to 30%. The team has stated that the new process is a perfect tool for minimising surface wear and significantly extending the service life of components.
“With the new process, we can now respond quickly and flexibly to different thermal, chemical and mechanical loads, as we can adjust toughness and hardness with pinpoint accuracy,” stated Marius Gipperich, Project Manager.
The positive results of the MatLaMeD project, funded by German Federal Ministry of Education and Research (BMBF), provide the researchers with a basis for further developing the new method to develop other material systems with special properties. The Fraunhofer IPT team are planning to use the hybrid LMD process in various application areas, such as the machining of forming tools or the treatment of friction wear layers of hydraulic components. Currently, testing is focusing on hybrid LMD process in the production of graded coating systems. To do this, the scientists want to, as much as possible, increase the titanium carbide content of the material mixture. Since titanium carbide can cause high residual stresses that can increase susceptibility to cracking during welding, the Aachen research team aim to adjust the TiC content individually layer by layer.