Self-healing of defects in ceramic composites ZrB2–SiC–TaB2 with dual composite structure

The paper presents the results of the study of self-healing of ceramic composite materials of ZrB2-SiC-TaB2 system with the structural architecture – «composite in composite», which is formed according to the principle of two-phase composite inclusions in two-phase composite matrix, and homogeneous distribution of components. It is shown that self-healing of surface defects occurs as a result of interaction of composite components with air oxygen, which provides filling of formed defects by products of oxidation reaction. It is revealed that the structure «composite in composite » allows to extend the temperature range of self-healing and increase the oxidation resistance of the studied ceramics. Dual composites with 10 and 20 vol% of composite inclusions and a composite with homogeneous distribution of components are characterized by self-healing at a lower temperature than composites with a higher content of composite inclusions, which is due to the lower oxidation resistance of the composite matrix based on ZrB2. On the surface of the composite with 20 vol% of inclusions, the defect is completely healed at 1400 ℃, which is the lowest temperature for all the composites investigated. The dual composites with 30, 40 and 50 vol% inclusions have higher oxidation resistance compared to the composites with lower volume inclusion content, which is due to the localization of TaB2, which has a higher oxidation activation energy. The mass gain of composites with the volume content of inclusions more than 20 % is significantly lower than that of composites with lower inclusion content at all investigated annealing temperatures in air.