Kinetics of Shrinkage, Structurization, and the Mechanical Characteristics of Zirconium Boride Sintered in the Presence of Activating Additives

Abstract

Compaction kinetics, structurization, and mechanical characteristics of ceramics based on zirconium boride during the combined addition of sintering activating carbon additives, tungsten boride, and zirconium and tungsten silicides into the system are investigated. It is shown that the efficient additives for ZrB2 ceramics are tungsten silicide and boride, which allow not only reducing the sintering temperature and activating the ceramic compaction, but also provide the maximum strength of the samples. The shrinkage of activator-free ZrB2 occurs in the restructuring of boride that sinters with the formation of an azimuth texture. It is established that these processes do not occur in the ceramics sintered with activators. When such processes are developing, the sintering occurs under the conditions of intensive grain-boundary phase interactions. The mechanical characteristics are studied mainly by the indentation method with the determination of a certain number of ceramic strength characteristics. The differences in the characteristics of ceramics produced by hot pressing in vacuum and by hot pressing in the CO–CO2 atmosphere are studied. It is established that the grain-boundary strength of forming materials and their defective state show the greatest differences. The data obtained allow optimizing the production, composition, and structure of ceramics to ensure the necessary mechanical characteristics (compressive strength, tensile strength, bending strength, hardness, and fracture toughness).