Study on ductile/brittle removal transition during grinding of WC–HEA cemented carbide

High-entropy cemented carbide (tungsten carbide–high-entropy alloy [WC–HEA]), as a novel class of ultrahard materials developed in recent years, exhibits exceptional mechanical properties including high strength, hardness, and wear resistance. However, the fundamental mechanisms governing its surface formation during grinding processes remain poorly understood. This study systematically investigates the ductile–brittle transition behavior through progressive-depth single-grit scratch experiments combined with theoretical modeling. Experimental characterization of scratch forces, surface morphology evolution, and three-dimensional morphology was conducted under strictly controlled conditions. A predictive model for critical cutting depth was developed based on the Griffith energy balance criterion and indentation fracture mechanics theory. The scratching experiment results reveal three distinct material removal regimes: (1) Ductile-dominated removal (scratching depth <0.802 µm) producing defect-free surfaces. (2) Transition regime (0.802–2.53 µm) characterized by intermittent crack initiation (first macrocrack observed at 0.802 µm). (3) Brittle fracture-dominated removal (>2.53 µm) exhibiting severe surface damage. Cross-sectional scanning electron microscopy (SEM) analysis confirmed the absence of lattice defects in ductile removal mode processing, while brittle removal mode showed intergranular cracking along WC/HEA interfaces. The experimental transition thresholds show <15% deviation from theoretical predictions, validating the proposed model. This work establishes a theoretical framework for achieving damage-free machining of WC–HEA composites, with critical implications for high-quality surface processing in precision manufacturing applications.