A team of researchers at the Fraunhofer Institute for Production Technology IPT in Aachen has developed a hybrid additive manufacturing process that combines wire and powder-based laser metal deposition (LMD). The new process can be used to apply protective coatings made of high-strength tool steel to workpieces and repair surface defects cost-effectively. The tool coatings produced in this way are more wear-resistant, resource- and cost-efficient than those produced using other methods. Following successful test series with tool components, there are plans to use the process for machining hydraulic components.
Additive manufacturing processes such as LMD are used to manufacture or locally optimize components. In LMD, a laser beam is focused on the component surface; at the same time, an additive material - usually in the form of powder or wire - is fed in and melted. LMD is ideal for applying protective coatings to components subject to high stress, repairing damaged areas and changing the geometry of workpieces, even at short notice.
Combination of wire and powder is flexible and cost-effective
In the recently completed "MatLaMeD" research project, a team of scientists from the Fraunhofer IPT and their international project partners have developed a hybrid version of laser cladding 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 specifically adjusting important material properties such as hardness and toughness of the deposited layers. The process is also significantly more cost-effective than a pure powder process and offers greater material flexibility than a pure wire process.
Individual material combinations for different requirements
In order to identify the best material combinations for different applications, the scientists tested numerous materials. As wire materials for the practical test series, they ultimately chose a hot-work tool steel with good structural stability and a low-alloy steel that is easy to weld. As powder materials, they used chromium (Cr) as a carbide forming and grain refining element and titanium carbide (TiC) as a hard phase in the test series.
Hardness increases of up to 30 percent
By combining wire and powder, the researchers were able to flexibly adapt the material composition for each application. The addition of the powder material made it possible to specifically change the microstructure of the tool steels and increase the hardness of the applied layers: even the addition of small amounts of titanium carbide led to increases in hardness of up to 30 percent. "With the new process, we can now react quickly and flexibly to different thermal, chemical and mechanical stresses, as we can adjust toughness and hardness with pinpoint accuracy," says project manager Marius Gipperich. According to the Aachen scientist, the new process is a perfect tool for minimizing surface wear and significantly extending the service life of components.
Test series planned for machining hydraulic components
The positive results of the "MatLaMeD" project provide the researchers with a basis for further developing the new method for developing other material systems with special properties. They are also planning to use the hybrid LMD process in various areas of application, such as the machining of forming tools or the treatment of friction wear layers on hydraulic components.
The researchers are currently testing the possibilities for using the hybrid LMD process in the production of graded coating systems. To do this, they want to increase the titanium carbide content of the material mixture as much as possible. As titanium carbide can cause high residual stresses, which can increase susceptibility to cracking during welding, the Aachen research team would like to individually adjust the TiC content layer by layer.
The "MatLaMeD - Development of new processes for hybrid laser cladding" project was funded as part of the "Innovations for the production, services and work of tomorrow" funding initiative of the Federal Ministry of Education and Research (BMBF).
