SiCf/SiCN-based Ceramic Matrix Composites (CMCs) are promising structural materials for the hot-sections of next-generation gas turbines and airplane propulsion systems. Due to their excellent high-temperature properties, an increase in combustion temperatures can be achieved, resulting in improved efficiency and reduced emissions. However, during cyclic operation crack formation and in-depth diffusion of O2- and H2O-containing combustion gas, may result in accelerated oxidation and degradation of the CMC. An improved material design with a boron-containing additive can promote self-healing of the ceramic matrix by the formation of a borosilicate melt filling the cracks. Thereby, inward diffusion of oxidizing combustion gas species can be slowed down resulting in an improved oxidation resistance of the CMC.
In this work, a self-consistent CALPHAD-type dataset for the multi-component system Zr-Si-B-C-N-O-H was developed. Heterogeneous reactions between the ZrB2 additive and the SiCf/SiCN composite were modeled as well as the interaction with a O2/H2O-containing combustion atmosphere. Calculations were validated by performing high-temperature annealing experiments with a model-system consisting of a precursor-derived SiCN-ceramic filled with a ZrB2-additive. Additionally, oxidation tests were performed in prototypic combustion atmospheres.