Possibility of obtaining heat-resistant structures in zro2-based ceramics

Today, additive technologies are becoming widespread, and metallurgy is leading in this direction. However, the use of such technologies creates new requirements for ceramic materials used in ferrous metallurgy. Particular attention is paid to the ability of the material to withstand sudden heating to high temperatures and subsequent rapid cooling. The authors considered the possibility of obtaining heat-resistant ceramics from a powder system based on ZrO2 with a controlled structure of particles and pore space for the wide use in contact with melts of steels and alloys. In the production of ceramics, the main tasks were to create a pore structure that prevents the propagation of cracks and the formation of a main crack, as well as the formation of a fine-crystalline structure that reduces the rate of crack propagation. Bushings made of ceramics of the zirconium dioxide-magnesium oxide system, which are optimal in their parameters for use as nozzles and pipes through which the metal melt passes during spraying and obtaining powders during the implementation of additive technologies, have been investigated. In the course of the experiment, bushings with different values of open porosity were made by cold isostatic pressing (CIP). As a criterion for heat resistance, the number of heat cycles was chosen, which the material can withstand without destruction when the workpiece is cooled in running water after heating in a furnace (thermal shock). Thermal shock tests showed that the bushings with open porosity in the range of 8–10 % turned out to be the most heat-resistant: the bushings withstood 11–12 thermal cycles (1200°C, water) without destruction. The microstructure of workpieces with different values of open porosity is investigated, the features of the morphology of particles and pores in the sintered structure are shown, and the evolution of the phase composition of the sintered ceramics is established. © 2020, Ore and Metals Publishing house. All rights reserved.