Effect of Co-alloying Ti and V on microstructure, mechanical and tribological properties of (Wx,Tiy,V1-x-y)C-Co alloys: A combined theoretical and experimental study

In this study, the effects of co-alloying Ti and V on cemented carbide alloys were investigated. Theoretically, the effects of co-alloying Ti and V on structural stability were studied from the perspective of energy stability criteria and elastic stability criteria. The results show that the face-centered-cubic (FCC) structure (W-x,Ti-y,V1-x-y)C carbides are stable in two domains, one is the WC-poor domain (the concentration of WC is less than 25 at.%), and the other is WC-rich domain (the concentration of WC ranges from 61.5 at.% to 75 at.%). The calculated hardness of FCC structure (W-x,Ti-y,V1-x-y)C carbide has a maximum of about 27 GPa. As for the hexagonal-close-packed (HCP) structure (W-x,Ti-y,V1-x-y)C carbides, they are stable in WC-rich domain (the concentration of WC is greater than 75 at.%). The calculated hardness of HCP structure (W-x,Ti-y,V1-x-y)C carbide has a maximum of about 37.2 GPa. Experimentally, the HCP structure (W-x,Ti-y,V1-x-y)C-8wt.%Co alloy was prepared by mechanical alloying and hot pressing sintering as the HCP structure (W-x,Ti-y,V1-x-y) C carbide has higher hardness. The results show that, as the concentration of co-alloying Ti and V increases, the hardness of the (W-x,Ti-y,V1-x-y)C-8 wt.%Co alloy increases, but the fracture toughness of the (W-x,Ti-y,V1-x-y)C-8 wt.% Co alloy decreases. The effect of co-alloying Ti and Von the hardness can be attributed to the solid solution strengthening and grain refinement strengthening. The achieved hardness of the (W-x,Ti-y,V1-x-y)C-8 wt.% Co alloy is higher than that of the conventional binary cemented carbide alloys. The tribological properties studies show that co-alloying Ti and V can effectively improve the wear resistance of (W-x,Ti-y,V1-x-y)C-8 wt.% Co alloys. The main wear mechanism can be attributed to the adhesive wear. (C) 2019 Elsevier B.V. All rights reserved.