Effect of TiC content on the carbide particle growth of NbC-Ni cemented carbide

The current study reports the influence of TiC addition on carbide particle growth of NbC-Ni cemented carbides. Microstructural analysis after liquid phase sintering in vacuum at 1420 degrees C for 40 min showed a decrease in NbC grain size as TiC content increased, associate to a change in NbC carbide morphology from rounded to equiaxed. Chemical composition from EDS analysis revealed a mixed carbide (Nb,Ti)C formation, with a gradient of Ti in carbide region for samples with TiC above 15%. Dictra (R) simulations of spherical particles immersed in Ni matrix evidenced a retardation in carbide dissolution and a decrease in the volume dissolved as TiC is added. It was also noted that liquid phase composition for 140 min showed less Nb in liquid phase available for reprecipitation during cooling process, promoting carbide particle growth inhibition. Ti profiles from Dictra (R) and carbide composition from EDS suggest a thin Ti rich layer formation in carbide/binder interface, which can be related to the carbide particle growth inhibition mechanism. TiC addition promote an increase in hardness and toughness values, and the highest values for both properties was found for 7%TiC-NbC-12%Ni composition (mass percent).