Enhancing toughness and wear resistance of ultrafine-structured WC-Co coating via ZrO2 incorporation

This study investigates the effects of ZrO 2 addition on the microstructure, mechanical properties, and wear resistance of thermally sprayed WC-Co coatings using in situ synthesized ultrafine WC-12wt.%Co composite powder and yttria-stabilized zirconia (YSZ) powder as raw materials. Microstructural analysis revealed that 3 wt.% ZrO 2 addition effectively suppressed WC grain coarsening during thermal processing and retained a tetragonal ZrO 2 structure in the coatings. The stress-induced phase transformation from tetragonal to monoclinic ZrO 2 triggers crack deflection and bridging mechanisms, which significantly enhance fracture toughness without compromising hardness. Compared to conventional WC-12Co coatings, the 3% ZrO 2 -modified coating exhibits a twofold enhancement in wear resistance under a 90 N load. The toughening mechanism effectively inhibits crack initiation and propagation, shifting the failure mode from catastrophic chunk spalling to progressive mild wear. This work demonstrates that optimizing ZrO 2 content balances hardness and toughness, providing a viable strategy for developing high-performance wear-resistant cermet coatings.