Researchers have developed a hybrid additive manufacturing process that combines wire-based and powder-based laser material deposition (LMD), also known as cladding.
The new process is significantly more cost-effective than a pure powder process while offering greater material flexibility than a pure wire process.
In LMD, a laser beam is focused on the component surface while a filler material – usually a powder or wire – is fed and melted. LMD is well suited for applying protective coatings to heavily stressed components, repairing damaged areas and changing the geometry of workpieces.
Fraunhofer IPT scientists, together with the partners of the recently completed ‘MatLaMed’ project, have developed a hybrid LMD process in which wire and powder are processed simultaneously. The partners say that the tool coatings produced using the new process are more wear-resistant, resource-efficient and cost-efficient than those produced by other methods. They plan to use the process in a variety of application areas, such as the machining of forming tools or the treatment of friction wear layers of hydraulic components.
By combining wire and powder, the researchers are able to flexibly adjust the material composition – and thus the applied coating properties – with each application of the new process.
‘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,’ explained project manager Marius Gipperich.
In developing the new process, the scientists tested numerous materials. For the wire, these included a hot-work tool steel with good structural stability and a low-alloy steel that can be welded well. For the powder, chromium was used as a carbide-forming and grain-refining element, while titanium carbide was used as a hard phase. Even the addition of small amounts of titanium carbide led to coating hardness increases of up to 30 per cent.
The positive project results have provided the researchers with a basis to further develop the hybrid LMD process and imbue other material systems with special properties. Currently they are testing the possibilities for using the new 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. Since titanium carbide can cause high residual stresses that can increase susceptibility to cracking during welding, the researchers would like to adjust the titanium carbide content individually layer by layer.