Investigating the Wear Resistance of Cdiamond–(WC–Co)–ZrO2 Composite Impregnated Crowns in Granite Drilling

The study investigated the wear rate dependences of diamond-impregnated drill bits consisting of composite diamond-containing materials (CDMs): specifically, 25C_diamond–70.5WC–4.5Co and 25C_diamond–68.62WC–4.38Co‒2ZrO₂. These materials were fabricated via spark plasma sintering at temperatures ranging from 20 to 1350°C under a pressure of 30 MPa for 3 min. Testing was conducted under rotational speeds and axial load conditions typical for granite drilling. It was demonstrated that incorporating 2 wt % of ZrO₂ nanopowder into the composition of 25C_diamond–70.5WC–4.5Co resulted in a threefold reduction in wear rate. The highest wear resistance of these diamond-impregnated drill bits was observed at rotational speeds of 250 rpm and axial loads of 900 kg, as well as at 750 rpm and 1250 kg axial load. Comparatively, the enhanced wear resistance of diamond-impregnated drill bits made from 25C_diamond–68.62WC–4.38Co‒2ZrO₂, in contrast to those made from 25C_diamond–70.5WC–4.5Co, can be attributed to factors such as finer grain size, higher relative density, improved strength under compression and bending, increased fracture toughness, and the formation of strong bonding between diamond grains and the hard-alloy matrix. These findings, combined with the fine-grained structure of the hard-alloy matrix and high diamond retention, indicate that these diamond-impregnated drill bits have potential for application in developing new tools with superior operational properties for drilling hard rock formations.