From scrap to product: the effect of recycled tungsten carbide and alumina content on the mechanical properties of oxide-carbide duplex ceramic composite

With the depletion of critical raw materials (CRMs), such as tungsten (W) and cobalt (Co), the sustainable recycling of tungsten carbide-cobalt (WC-Co) hard metal scraps has become essential. This study explores a sustainable recycling method for WC-Co scraps to produce duplex ceramic composites intended for dry machining. WC-Co scrap (6% Co) was mechanically crushed, sieved to under 1 mm, leached by H2SO4, and then ball-milled to obtain fine WC powder with a particle size of ~1 μm. To study the effect of using recycled powder and to trace the effect of alumina content, two compositions were synthesized via spark plasma sintering (SPS) at constant pressure and holding time at temperatures ranging from 1500 °C to 1600 °C. Composites containing 46% alumina and 12% ZrO2 were combined with either recycled or commercial WC (42% by volume), and a third composite with high-alumina content (72% Al2O3, 2% ZrO2, and 26% WC) was also prepared. Microstructural analysis via a scanning electron microscope (SEM) and an energy dispersive spectrometer (EDS) showed minimal impurity in the recycled powder and material integrity. Density measurements using the Archimedes method, along with mechanical testing, were conducted to evaluate the mechanical properties. Composites produced from recycled WC exhibit mechanical properties comparable to those of commercial composites, with minimal degradation. This recycling approach offers a safe, environmentally friendly and sustainable solution, minimizing health risks (compared to other recycling methods), while effectively preserving critical materials for high-performance, wear-resistant applications in machining.