Solid-state repair of tungsten components using fully recycled W nano-micro powders derived from WC-co hard-metal scrap

Tungsten components are widely used in extreme high-temperature and high-load environments; however, their repair remains challenging due to tungsten's exceptionally high melting point and poor weldability. In this study, a recycling-based solid-state repair strategy is proposed using tungsten nano–micro powders fully derived from WC–Co hard-metal scrap. Recovered WO₃ was obtained through oxidation and hydrometallurgical purification, followed by hydrogen reduction and inductively coupled thermal plasma processing to produce tungsten nanoparticles and spherical micro-powders. Quantitative impurity analysis using ICP-OES and LECO measurements confirmed that metallic and interstitial impurities were effectively reduced to ppm-level concentrations during processing, ensuring high chemical purity of the recycled powders. A three-layer filler architecture consisting of nanoparticle / nano–micro blended / nanoparticle layers was designed to enhance interfacial activation and densification during spark plasma sintering (SPS). Repairing was performed at 1250 °C and 1850 °C to clarify the effects of temperature and geometric constraints on densification behavior. At 1250 °C, non-uniform densification occurred due to preferential current flow and pressure shielding inside groove-type defects. In contrast, SPS at 1850 °C resulted in fully dense joints with continuous grain structures across the filler–substrate interface, as confirmed by EBSD analysis and uniform micro-hardness distributions. These results demonstrate that high-purity recycled tungsten nano–micro powders combined with high-temperature SPS provide an effective and resource-efficient route for solid-state repair of refractory tungsten components, offering a sustainable alternative to conventional replacement-based practices. • A recycling-based solid-state repair route for tungsten components is proposed. • Tungsten nano- and micro-powders were fully recycled from WC–Co hard-metal scrap. • A three-layer filler architecture enhanced interfacial activation and densification. • High-temperature SPS enabled fully dense joints with continuous grain structures. • The approach provides a sustainable alternative to replacement of tungsten components.