Processing and properties of TiB2 with MoSi2 sinter-additive: A first report

Abstract

The densification of non-oxide ceramics like titanium boride (TiB 2) has always been a major challenge. The use of metallic binders to obtain a high density in liquid phase-sintered borides is investigated and reported. However, a non-metallic sintering additive needs to be used to obtain dense borides for high-temperature applications. This contribution, for the first time, reports the sintering, microstructure, and properties of TiB 2 materials densified using a MoSi2 sinter-additive. The densification experiments were carried out using a hot-pressing and pressureless sintering route. The binderless densification of monolithic TiB2 to 98% theoretical density with 2-5 μm grain size was achieved by hot pressing at 1800°C for 1 h in vacuum. The addition of 10-20 wt% MoSi2 enables us to achieve 97%-99%ρth in the composites at 1700°C under similar hot-pressing conditions. The densification mechanism is dominated by liquid-phase sintering in the presence of TiSi2. In the pressureless sintering route, a maximum of 90%ρth is achieved after sintering at 1900°C for 2 h in an (Ar+H2) atmosphere. The hot-pressed TiB2-10 wt% MoSi2 composites exhibit high Vickers hardness (∼26-27 GPa) and modest indentation toughness (∼4-5 MPa·m12). © 2005 The American Ceramic Society.