Harnessing nanolaminate coatings for high temperature applications

• Applicants: Dr. Nadine Laska; Professor Jochen M. Schneider, Ph.D.
• Subject Area: Coating and Surface Technology ; Synthesis and Properties of Functional Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512808854

Nanolaminate coatings based on MAX or MAB phases (where M is an early transition metal, A is an A-group element, X is carbon or nitrogen, and B is boron) combine unique ceramic and metallic material properties, providing significant potential for applications in high temperature environments. Within the project the manufacturing of the alumina forming MAX and MAB (with M = Cr or Ti and A = Al) nanolaminate coatings deposited by various PVD techniques will be validated and their performance at high temperature under dry and wet atmospheres will be elucidated. For the first time, three different PVD techniques available at the partnering institutions in Poland and Germany will be compared, including High Power Pulsed Magnetron Sputtering, DC and reactive magnetron sputtering and Closed Hollow Cathode PVD. The possibility to compare and combine these techniques enables a unique opportunity to understand the influence of various deposition parameters on the performance of the nanolaminate coatings. The coatings will be applied on intermetallic TiAl and ceramic SiC. The project will focus on the development of a protective thermally grown oxide layer composed of alumina and its evolution during long-term high temperature exposures. A promising lifetime improvement is expected for TiAl alloys due to stabilization of the alumina layer by the replenishing effect provided by the Al-rich substrate, thereby preventing the degradation of the MAX/MAB phase coatings due to Al-depletion by inward diffusion into the substrate material. Moreover, the well-known deterioration of the mechanical properties of TiAl by protective, but brittle coatings could be prevented by the deposition of ductile MAX or MAB phase based nanolaminates. In case of the silicon carbide, the necessity for protection against water vapor corrosion is mandatory. The state-of-the art environmental barrier coating systems are based on rare earth silicates with up to 4 different layers. For this reason, their potential replacement by single layered and alumina forming MAX or MAB phase-based coatings is evaluated, providing a sustainable raw material usage. Special attention will be paid to the adhesion of the nanolaminates during high temperature exposure as well as the interface design between coatings and the inert ceramic SiC. Interdiffusion processes between the nanolaminates and SiC will be evaluated by experiments and thermodynamic simulations using CALPHAD methods. Moreover, the optional implementation of a CTE-matched, Al-rich interlayer will be investigated based on these calculations, where AlN is predestined due to a CTE between SiC and MAX or MAB-phases. Finally, long-term cyclic oxidation tests and isothermal exposures in water vapor atmospheres of the different nanolaminate coated TiAl and SiC substrate materials will be performed. The mechanical behavior of the coated and uncoated TiAl alloy will be evaluated by tensile, fatigue and creep tests in high temperature environments.

• DFG Programme: Research Grants
• International Connection: Poland
• Partner Organisation: Narodowe Centrum Nauki (NCN)
• Cooperation Partners: Bugoslaw Mendala, Ph.D.; Dr. Radoslaw Swadzba