Kinetics of self-healing of a main crack in WC-Co hard alloy

The paper studies the kinetics of self-healing of a main crack in tungsten carbide-cobalt (WC-8 mass % Co). The self-healing in WC-Co hard alloy occurs through the liquid-phase recovery with cobalt and partially dissolved tungsten carbide acting as healing agents. Over an eight-hour holding near the sintering temperature, the total crack length was reduced by 30 %. The maximum crack width capable to self-healing through the liquid-phase recovery was approximately 50 μm. One-hour healing led to filling of the crack zone with cobalt. Further self-healing resulted in the growth of individual grains into binder in the healed zone. Six-hour isothermal holding near the sintering temperature resulted in elimination of the differences in the microstructure between the healed area and the base material, however, a significant cobalt depletion and the formation of brittle η-phase (Co3W3C or Co6W6C) indicating a decrease in the carbon content made further self-healing processes impossible. As self-healing mechanism is limited by healing agent content in WC-Co alloys, large damages elimination requires the use of external healing agents. For the practical solution of the extensive defects recovery, it was proposed to use hetero-healing methods, for example, isothermal holding in a carburized atmosphere and the use of infiltrates based on WC-Co mixtures with cobalt excess.

1. Government research assignment for ISPMS SB RAS - FWRW-2026-0002