Fraunhofer ILT project investigates L-PBF of tungsten carbide-cobalt

October 17, 2019

Fraunhofer ILT and RWTH Aachen University to investigate how L-PBF AM can process tungsten carbide-cobalt in new research project
Preheating the machining plane with the NIR is said to significantly reduce stresses in the L-PBF additively manufactured component (Courtesy Fraunhofer ILT)

The Fraunhofer Institute for Laser Technology (ILT), Aachen, Germany, has launched a research project in collaboration with scientists from the Institute for Materials Applications in Mechanical Engineering (IWM) and the Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University to investigate how Laser Powder Bed Fusion (L-PBF) can be used to process tungsten carbide-cobalt (WC-Co).

The research project, titled ‘Additive Manufacturing of Machining Tools out of WC-Co – AM of WC-Co’, aims to enable the metal Additive Manufacturing of cutting tools with longer tool lifespans, achievable by the incorporation of complex cooling geometries into the tool’s design, at strengths comparable to cutting tools produced using conventional processes. 

Fraunhofer ILT explained that, traditionally, cutting tools made of WC-Co could only be manufactured using complex sintering processes. Since these materials are so strong, and traditional sinter-based technologies only offer restricted geometric freedom, cutting tools have only been able to be shaped to a limited extent. This has made introducing complex cooling structures into the tools costly or simply impossible.

Additive Manufacturing processes offer a high degree of design freedom and near-net shape production, and enables complex cooling structures to be generated within the cutting tool. L-PBF is particularly suitable for this purpose. In turbine construction, significantly higher operating temperatures have already been achieved through the use of additively manufactured parts.

As Fraunhofer ILT explained, a major challenge in the L-PBF process is temperature distribution in the additively manufactured workpiece, due to the fact that the metal powder is melted in the laser spot and then quickly cools down. Conventional systems have a heated base plate to slow down the cooling process, but this is not sufficient for refractory materials and large components. Uneven temperature distribution can cause tension or even cracks to occur in the component.

The team at Fraunhofer ILT has been working on this issue for some years and, in cooperation with the company adphos Innovative Technologies GmbH, reports that it has developed a system in which a near-infrared (NIR) emitter heats the component from above. With an output of up to 12 kW, the emitter can achieve temperatures of up to 800°C in the component. In the ‘AM of WC-Co’ project, this technology is to be used to process tungsten carbide-cobalt.

For this purpose, the partners will investigate the complete process route from powder materials to the AM process, up to post-processing and testing. The scientists will qualify those materials and processes that can be used to replace conventional sintering processes.

The research project is funded by the Otto von Guericke e.V. working group of industrial research associations. It is expected to span thirty months and began on October 1, 2019. Fraunhofer ILT will present the research project at Formnext 2019, Frankfurt, Germany, from November 19–22.

www.ilt.fraunhofer.de

www.rwth-aachen.de

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