Mechanical and chemical damage mechanisms of brazed high temperature alloys for the optimization of a novel sealing liner structure

• Applicants: Professor Dr.-Ing. Hans-Jörg Bauer; Professor Dr.-Ing. Uwe Glatzel; Professor Dr. Jan Torgersen
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins ; Synthesis and Properties of Functional Materials
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 567342900

The efficiency of aircraft engines and stationary gas turbines is significantly influenced by clearance losses. To minimize these clearances, turbomachinery often employs labyrinth seals with abradable liners. During operation, contact between the rotor and the abradable liner occurs due to thermal expansion or dynamic loads, leading to a phenomenon known as rubbing process. The overarching goal of the project is to investigate the damage behavior of brazed nickel-based alloys during rubbing and optimize the abradable liner structure aerodynamically and tribologically. The collaborative research from the three involved universities focuses on the manufacturing and examination of rhombic abradable liners with variations in parameters such as cell sizes, braze filler alloys, and cell angles. The tribology and aerodynamics of these novel abradable liners are experimentally characterized. In addition to the conventional nickel-based braze BNi-5, a new braze filler alloy (Mn35Fe5Co20Ni20Cu20) is also under investigation. The high-temperature properties of brazed samples are analyzed through oxidation tests and high-temperature tensile tests. The wettability of the braze filler alloys is determined using high-temperature contact angle measurements. The findings, combined with microstructural analyses of the brazed samples, are utilized to optimize the brazing process for the employed materials and the novel abradable liners. The experimental investigations are complemented by simulations, including the transfer of microstructure-based simulations to the failure analysis of notched, thin-walled components. A multiscale approach in the sheet plane is applied to enable a more precise evaluation of the failure behavior. Furthermore, an already developed microstructure-based damage model for quasi-brittle materials is extended to adequately capture ductile damage processes (optimized brazing process). The results of these studies aim to establish a comprehensive understanding of damage behavior and aerodynamic properties. The objective is to make effective improvements to the abradable liners while simultaneously expanding scientific knowledge in this field. The integration of machine learning facilitates innovative optimization of the abradable coatings (e.g., structural integrity and aerodynamic efficiency) considering various criteria.

• DFG Programme: Research Grants