Hybrid Additive Manufacturing Process Improves Coatings

A team at the Fraunhofer Institute for Production Technology (IPT) has introduced an additive manufacturing (AM) process that combines wire-based and powder-based laser cladding. According to the team, the hybrid process produces protective tool coatings that are more wear-resistant, resource-efficient, and cost-efficient than those produced via conventional laser cladding methods. The hybrid process is also more flexible than a purely wire-based approach to cladding.

Laser cladding produces 3D structures through laser metal deposition (LMD); during LMD, the surface of the workpiece is heated with a laser beam while a filler material in the form of powder or wire is fed into the melting pool area. When the filler melts, it builds a coating on the surface. Structures can be built layer by layer directly on the surface of the piece. LMD is an effective way to apply protective coatings, repair damaged components, or change the geometry of a workpiece.

In IPT’s hybrid approach, wire and powder materials are processed simultaneously during LMD. The scientists found that by adding hard material particles in powder form to the wire material, they could adjust important material properties in the coatings, such as hardness and toughness, for the first time using LMD.

To identify optimal material combinations for different applications, the scientists tested various materials. For wire materials, they selected a hot-work tool steel with high structural stability and a low-alloy steel with good weldability. For powder materials, they chose chromium as the carbide-forming and grain-refining element, and titanium carbide (TiC) as the hard phase.

From the combination of powder and wire, the scientists were able to tailor the composition of the material for each application. They selectively changed the microstructure of the tool steels and increased the hardness of the applied coatings by adding powder. The addition of even small amounts of TiC led to increases in hardness of up to 30%.

Tool coatings produced via a hybrid AM process, developed by a team at Fraunhofer IPT, are more wear-resistant, resource-efficient, and cost-efficient than those produced by other methods. Courtesy of Fraunhofer IPT.

“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,” project manager Marius Gipperich said. According to Gipperich, the new hybrid process is ideal for minimizing surface wear and extending the service life of components. It is more cost-effective than a pure powder process, and it offers greater material flexibility than a pure wire process.

The scientists plan to apply their method to the development of other material systems with special properties. They also plan to use the hybrid process for applications such as the machining of forming tools, as well as the treatment of friction wear layers of hydraulic components.

Currently, the IPT team is testing the use of the hybrid process in the production of graded coating systems. As part of the testing, the team plans to increase the TiC content of the material mixture as much as possible. Since TiC can cause high residual stresses that can increase susceptibility to cracking during welding, the team plans to adjust the TiC content on an individual layer-by-layer basis.