The effect of atmosphere control on the sintering behavior of $TiB_2$-20wt% Ni cermet was investigated. Sintering was performed at 1600-1800℃ with commercial $TiB_2$ powders produced by carbothermic reaction(FSSS=1.9㎛).
Relative densities as high as 99.5% were achieved by changing the atmosphere from vacuum to Ar at 1500℃ and sintering subsequently at 1700℃. Under the signle atmosphere such as Ar or vacuum, however, densification was restricted and large pores remained.
Microstructural consideration was conducted about these phenomena on the bais of the theory of entrapped inert gas effect. When nondiffusing Ar gas was entrapped in the closed pore, pore elimination did not occur and pore coalescnce was resulted with increased sintering time. But, rapid pore filling was observed when the pore was in the state of vacuum.
The role of WC as a grain growth inhibitor for $TiB_2$ grains and the mechanism of this grain growth inhibition were also investigated.
