Processing and Properties of TiB₂ with MoSi₂ Sinter‐additive: A First Report

Abstract

The densification of non‐oxide ceramics like titanium boride (TiB2) 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 TiB2 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·m1/2).

Understanding Influence of MoSi2 Addition (5 Weight Percent) on Tribological Properties of TiB2

“…Correlation of Eq. [4] and the smaller size of the debris particles observed after fretting at the higher load implicates that probably lower adhesive forces exist between the interfaces under such conditions. This may be a direct consequence of the formation of the protective tribolayers on both flat as well as steel ball (Figures 6(c) and (d)), which further accounts for the observed diminution of COF and specific wear rate under higher load.…”

“…More details on the starting powders, processing, and material characterizations of the investigated TiB 2 -based ceramics are described elsewhere. [4,12,13] The sinter densities (as pct q th ) and mechanical properties of all TiB 2 -based ceramics used in the present investigation are presented in Table I.…”

“…[1,[4][5][6][7][8][9][10][11][12][13] We have reported the development of MoSi 2 -reinforced TiB 2 -based ceramics, possessing near theoretical density and superior combination of mechanical properties, via hotpressing route. [4,12,13] Superior mechanical properties, in combination with the thermal and chemical properties, [1] can potentially lead to better tribological properties of TiB 2 -based ceramics. Tribological behavior of composites is a complex phenomenon in the sense that, in addition to bulk and matrix properties, it is influenced by the physical, chemical, mechanical properties, amount, and distribution of the reinforcement phases.…”

“…[1][2][3][4] Due to these characteristics, TiB 2 -based materials are considered potentially viable for a wide range of technological applications, such as armor materials, wear components, cutting tools, electrodischarge machining (EDM) electrodes, aero-applications, conductive coatings, and cathode materials for Hall-Heroult cell. [1,2] However, challenges involved in sintering monolithic TiB 2 to near theoretical density, in addition to their poor fracture toughness (~4 to 5 MPa m 1/2 ), appear to limit the commercial applications of such materials.…”

Pressureless sintering of chromium diboride using spark plasma sintering facility

“…Diboride-based ceramics can be categorized under difficult to sinter materials as it possesses high melting points and strong covalent bonding [8][9][10][11][12][13]. In recent past, SPS has been extensively used to study the densification behaviour of diboride based ceramics, due to its fast heating rates and short holding time coupled with application of high mechanical pressures [4,9,11,14].…”