Effect of carbon and titanium carbide on sintering behaviour of zirconium diboride

Systematic sintering studies on the ZrB2 powder were carried out with the addition of carbon (C) in the range of 0 < x < 10 (x = wt.%) and (titanium carbide) TiC in the range of 0 < y < 30 (y = wt.%). Zirconium diboride powder made by different routes showed similar sintering behaviour and amongst all the powders, the SHS made powder exhibited most homogeneous morphology. The addition of C facilitate densification in the range of 0 < x < 4 and hinders densification for 4 < x < 10, whereas, the addition of TiC above 5 wt.% was found to be detrimental for the sintering of ZrB2. The addition of C also found to inhibit the grain size and fine grained ZrB2–C composite could be obtained with high densification. The increased densification with the C addition was due to removal of oxygen impurities on the ZrB2 powder surfaces that prevented the commonly observed exaggerated grain growth through evaporation condensation of oxide phases during sintering of boride ceramics. At higher percentages of C addition, the densification rates decreased due to increased volume fraction of second phase that acted as diffusion barrier.