Tailoring hardness–toughness balance in cemented carbides via ternary Ni-based (Ni, Co, W) and (Ni, Cu, W) binders

Cemented carbides with balanced hardness and fracture toughness were developed using ternary nickel-based binders (Ni-Co-W and Ni-Cu-W). The shear modulus was identified as the dominant parameter governing solid-solution strengthening in nickel alloys. The addition of Co significantly increases the shear modulus, whereas the addition of Cu decreases it. As a result, the alloy hardness increased with increasing Co content but decreased with increasing Cu content, indicating strengthening by Co and softening by Cu. These intrinsic alloy characteristics directly affect the mechanical performance of cemented carbides. The composites with Co-based binders exhibited increased hardness with increasing Co content, whereas those with Cu-based binders showed reduced hardness and enhanced fracture toughness with increasing Cu content. However, excessive Cu promotes tungsten segregation and WC formation, leading to secondary hardening. Accordingly, the Co-containing binders continuously hardened the cemented carbides, whereas the Cu-containing binders caused initial softening, followed by rehardening. The optimized compositions achieved hardness values of 15.3–19.0 GPa and fracture toughness values of 8.9–12.2 MPa·m^1/2, surpassing those of conventional WC–Co grades. These results demonstrate that strategic solute selection in Ni-based ternary binders enables simultaneous enhancement of the hardness and toughness of advanced wear-resistant materials.