The effect of atmosphere on the densification of $TiB_2$-Ni cermet has been investigated. $TiB_2$-Ni cermet compacts containing 10-30wt% Ni were sintered at 1500-1700℃ for various times in vacuum or in Ar.
In vacuum, the relative density of $TiB_2$-10wt% Ni sintered at 1700℃ for 60 min was limited to 95.6%. However, full densification was achieved with 30wt% Ni, although Ni volatilization was significant. From Relative sintered density- vs. average grain size trajectories, it was found that, for any compact, the densification was promoted by grain growth. It appears therefore that the densification was induced by grain growth, as predicted by the pore filling theory.
In Ar, full densification was not achieved due to the entrapped gas in pores, irrespective of Ni content in samples. With increasing the Ni content, pores were isolated at lower temperature, and therefore internal Ar gas pressure in isolated pores became higher at the sintering temperature, suppressing the densification. Consequently, higher Ni content does not appear to be effective for the densification of $TiB_2$-Ni cermet in Ar.
