Development of novel creep resistant bond coats for “Environmental Barrier Coatings”

• Applicant: Professorin Dr.-Ing. Kirsten Bobzin
• Subject Area: Coating and Surface Technology ; Joining and Separation Technology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 428973451

The objective of this entire research project is development of new Si-based bond coats by Si3N4 or SiC reinforcement to increase the lifetime of Environmental Barrier Coatings (EBCs) used to protect SiC-based high-temperature composites in modern jet engines. Within the previous project, the spray feedstocks and process for the novel Si-Si3N4 and Si-SiC coatings were successfully developed. The coatings were investigated in terms of coating structure, phase composition and properties such as hardness and fracture toughness. Selected coatings were subjected to oxidation tests. The results show that the Si-Si3N4 coating had lower mass gains compared to the Si reference coating in the cyclic oxidation test and thus represents a potential as a new bond coat. In the present continuing project, the extent to which the Si3N4 reinforcement could improve the creep resistance and the thermal shock behavior of the coating compared to the Si reference coating will be investigated. Furthermore, the correlation of the oxidation behavior at application temperature with the plastic deformation of the coating is investigated and the influence of the Si3N4 reinforcement on it is determined. For this purpose, the specimens are prepared and characterized on the basis of the results achieved so far. Using the thermal shock test rig available at IOT, the samples will be tested and analyzed with respect to the failure mechanisms. The influence of the Si-Si3N4 reinforcement will thus be clarified. In addition, the coatings are exposed under defined loads in the furnace. The mechanisms of effect of the Si-Si3N4 reinforcement on the creep resistance and the oxidation behavior of the coating are determined. The results of these investigations serve as a basis for evaluating the potential of the novel coatings for EBCs.

• DFG Programme: Research Grants