Effect of yttrium oxide addition on the microstructure and mechanical properties of WC–ni composites fabricated from recycled WC and Ni

WC-Co composites are widely used in cutting tools but are expensive and harmful due to Co in the composites. Alternatives, such as WC-Ni composites have inferior mechanical properties, as a result, WC-Co composites are used in most cutting tools. This study investigated whether adding yttrium oxide (Y₂O₃) to WC-Ni composites, fabricated from recycled tungsten carbide (WC) and Ni, improved their mechanical properties. Changes in the composites’ microstructure and mechanical properties depended on the amount of Y₂O₃ added. Y₂O₃ reacted with WC during sintering, promoting the formation of W and reducing the proportion of C in the composite. The added Y₂O₃ accelerated the dissolution of W in the Ni matrix, and increased the fractions of the eta phase and solid solution phase. Ni is strengthened by the dissolution of W in Ni, thereby supplementing the low toughness of the eta phase and ultimately yielding WC–Ni with improved hardness and fracture toughness (H_V: max. 15.4 GPa, K_IC: max. 13.4 MPa∙m^1/2) compared to WC–Ni without Y₂O₃ (H_V: 13.5 GPa, K_IC: 12.7 MPa∙m^1/2). The method for improving the properties of WC–Ni composites by the addition of Y₂O₃ has a high possibility of commercialization because it does not necessitate process changes.