Sinterability and Mechanical Properties of TiB₂ without Additives

Abstract

A commercial TiB₂ powder with the grain size of 2μm was milled by an attriter and the powder having the average grain size of 0.9μm and the oxygen content of 3.4 mass% was obtained. Sinterability of the powder without additives and mechanical properties of hotisostatically pressed compacts were investigated. The density of fired compacts improved with rising firing temperature. However, compacts with densities approaching 100% were difficult to obtain by pressureless firing. Abnormal grain growth with cracks and residual pores occurred in the compact fired at 2000°C and its density was 92%. A compact having 99.5% density could be obtained by firing at 1800°C and sequential hot isostatic pressing with encapsulation at 1700°C. Fracture toughness, 3-point bending strength and Vickers hardness of the hot-isostatically pressed compact were 3.3 MPa·m^1/2, 420MPa and 2500, respectively.