Effect of VC addition on the microstructure and properties of TiC steel-bonded carbides fabricated by two-step sintering

The effect of VC addition on microstructure, mechanical properties and high-temperature oxidation behavior of the TiC steel-bonded carbides, fabricated by two-step sintering, were examined by SEM, EDS, and XRD. The results show that an appropriate amount of VC enables the TiC steel-bonded carbide to further refine the hard phase particles while maintaining high density. When the VC addition amount is not higher than 0.8 wt%, the hard phase particles are gradually refined with the increase of VC content. The added VC is mainly distributed in the rim phase around the hard phase particles, which inhibits the dissolution and precipitation of TiC and thus refines the grains. When the VC addition amount reaches 1.2 wt%, the excess VC raises the possibility of particle agglomeration or segregation, which will coarsen the rim phase and degrade the mechanical properties. Overall, TiC steel-bonded carbides with 0.8 wt% VC possesses superior comprehensive mechanical properties. Moreover, when TiC steel-bonded carbides are oxidized at a constant temperature of 750 degrees C, their high-temperature oxidation behavior follows a parabolic law. The oxidation rate is mainly controlled by the surface chemical reaction rate in the early stage and the oxygen ion diffusion rate in the later stage.