Effects of the Sintering Atmosphere and Ni Content on the Liquid-Phase Sintering of TiB2-Ni

Abstract

The effects of the sintering atmosphere and Ni content on the densification of TiB2-Ni have been investigated. TiB2 powder compacts containing 10, 20, and 30 wt% Ni were liquid-phase sintered at 1500-1700C in vacuum or in flowing Ar. The densification was enhanced as Ni content increased. For a given Ni content, the densification was faster in compacts with larger grain size. These densification behaviors agree well with the prediction of the recently developed pore-filling theory. For samples containing high Ni contents, 80TiB2-20Ni and 70TiB2-30Ni, the densification was faster in vacuum than in Ar. In particular, 70TiB2-30Ni was fully densified at 1700C for 60min in vacuum. The suppressed densification in Ar was due to the entrapped Ar in the isolated pores. On the other hand, for 90TiB2-10Ni, the Ar-sintering resulted in higher densification than did the vacuum-sintering. This result was attributed to the suppression of Ni volatilization by the Ar in the furnace and a retarded isolation of pores due to the limited amount of liquid in the sample. Therefore, vacuum sintering is recommended for the preparation of TiB2-Ni with a high Ni content while Ar sintering is recommended for the preparation of TiB2-Ni with a low Ni content.