In situ growth of carbon nanotubes on WC‐Co powder for toughening cemented carbide by different consolidation strategies

Abstract Carbon nanotubes (CNTs), known for high strength and modulus, were used to enhance the toughness of WC‐Co cemented carbide without compromising its hardness. The traditional approach of mixing CNTs into WC‐Co powder failed due to structural damage and poor uniformity of CNTs. This study proposed a novel in situ growth strategy for coating CNTs on WC‐Co powder using fluidized bed chemical vapor deposition. The densification behavior, phase evolution, microstructure, and performance of the CNTs‐coated WC‐Co powder were evaluated under three consolidation processes: laser powder bed fusion (LPBF), vacuum sintering, and spark plasma sintering (SPS). Under densification conditions, preventing the formation of the ƞ phase and preserving the CNTs improved the toughness. Although high densities were achieved during vacuum sintering, CNTs fully dissolved in the Co‐W‐C eutectic liquid phase. In LPBF, CNTs were largely retained, but low density and formation of ƞ phase resulted in the low toughness. Heat treatment at 1400°C eliminated the ƞ phase but caused the dissolution of CNTs. The high densification, absence of the ƞ phase, and retention of CNTs were simultaneously achieved during the solid‐phase sintering process of SPS, making it the most effective densification method for enhancing toughness with CNTs.