EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Hardmetals (also known as cemented carbides) are a class of composite materials employed for the production of cutting and forming tools as well as wear resistant parts. Standard powder metallurgy often suffers limitations in the manufacturing of shapes required by application-oriented design. As a consequence, there is a great deal of interest for the implementation of AM processes to hardmetals. After many attempts to employ beam-based methods, recently low temperature AM processes, as Binder Jetting (BJ), are finding more and more attention, as they potentially allow to preserve microstructures and hardmetal peculiar properties.
In our work, the selected powder was tungsten carbide with 12 wt.% cobalt (WC-Co). The shaping phase was achieved by BJ via layer-by-layer selective deposition of binder droplets on the powder bed. It was followed by a low temperature curing treatment at 180 °C, to promote the binder polymerization, and a vacuum sintering process performed at 1400 °C. Finally, selected samples were treated via sinter-HIP process at 1400 °C to achieve near-full density.
First, the powder was analysed in terms of size and shape, to determine its suitability for the procedure. Then, the effects of different combinations of printing parameters, layer thickness (50 – 100 μm) and binder saturation (60 – 75 – 90 %), on the packing density of the green bodies were analysed. Finally, the relative density of the sintered components was measured and the porosity shape and size distribution inside the samples was studied by SEM imaging, to assess possible consequences of the deposition procedure. Vickers hardness along the samples cross-section was measured and correlated to the grain size. Finally, the microstructure was analysed, with attention to possible defects as enlarged carbide grains, molten cobalt pools and carbon segregation.