Development of High Temperature TiB2-Based Ceramics

Abstract

In view of potentiality of titanium diboride (TiB2) materials for high temperature applications, this paper presents the state of art on the processing, microstructure and properties of TiB2 ceramics. TiB2 ceramics are of interest for applications such as cutting tools, wear resistant parts, armor material and electrode materials in metal smelting because of their excellent combination of properties including high hardness, elastic modulus, better strength to weight ratio, wear resistance, good thermal and electrical conductivity. However, such broader applications of the monolithic TiB2 are inhibited by factors like high sintering temperature and poor toughness. Hence, research efforts are directed towards processing TiB2 at lower sintering temperature as well as to enhance the properties with the use of various metallic and non-metallic sinter-additives. In the above perspective, we review the existing literature in this article. In addition, our recent research results obtained with TiB2-TiSi2 materials are also presented. A review of research results revealed that a combination of room temperature properties, i.e. maximum Vickers hardness of 31 GPa and indentation toughness of 11 MPa m1/2 and flexural strength of 810 MPa is obtainable with optimally sintered TiB2. More importantly, a maximum hardness of 9 GPa (at 900oC) and flexural strength of 471 MPa can be retained upto 1200oC. From the perspective of oxidation resistance, TiB2 samples exhibit parabolic oxidation kinetics below 1000oC as result of the formation of TiO2 (s), and B2O3 (l) and linear oxidation kinetics above 1000oC in the presence of crystalline TiO2 and volatile B2O3.