Структурно-фазові перетворення у поверхневих шарах стопів на основі кобальту з карбідом титану після ультразвукового ударного оброблення

Ultrasonic impact treatment (UIT) is used to strengthening and densification of the surface layer of cobalt-based alloys with carbide hardening. The UIT induced structural-phase transformations provide a significant increase in hardness depending on the initial content of the carbide phase in the alloy. The hardening mechanism is due to the subdivision process of the subgrain/grain structure, the refinement of carbide particles, the elimination of porosity in the near-surface region, and concentration changes in the composition. A synergistic effect of carbide hardening and UIT allows achieving the maximum value of Vickers hardness of 16 GPa. Owing to the UIT influence, the 1.5 times increase in hardness of the alloy contained 60 vol.% of TiC can be achieved. In the UIT modified layer, the concentrations of carbon, titanium, and cobalt in the modified layer are revealed to be ∼20 at.%, the concentrations of chromium, iron, and nickel are ∼10 at.%. This chemical composition is characteristic for high-entropy alloys and can be an additional strengthening factor. [ABSTRACT FROM AUTHOR]