Fabrication of ultrafine-grained ZrC–Co cemented carbides with superior sliding-wear resistance from micrometre starting powders

Abstract

An ultrahard ZrC–Co cemented carbide was fabricated by high-energy ball-milling (HEBM) of micrometric starting powders and spark plasma sintering (SPS), whose ultrafine-grained microstructure makes it comparatively more sliding-wear resistant. First, it is shown that prolonged HEBM activates mechanically the ZrC+Co powder mixture, enhancing markedly its SPS densifiability (notable reduction of the SPS temperature attributable to the lowered eutectic temperature and speeded kinetics of solution-reprecipitation). The combination of refined particle sizes and enhanced sinterability yields ultrafine-grained ZrC–Co cemented carbides with ultrahigh hardness (~18 GPa) and sufficient fracture toughness (~6 MPa·m1/2). And second, it is shown that dry wear of the ZrC–Co cemented carbides is, regardless of the microstructure, mild (10−7 mm3/(N·m)) and occurs essentially by plasticity-dominated abrasion, but also that their microstructural refinement makes them comparatively much more wear resistant and therefore attractive for tribological applications.