Application of a Ni-based filler metal repair coating by thermal spraying for high pressure turbines - A hybrid coating, brazing and aluminizing process

摘要

Components in aircraft engines and gas turbines are exposed to extreme conditions in order to increase performance and efficiency of the overall engines, hence there is an increasing need for cost-effective and time-efficient repair strategies. In this contribution, an approach to the repair of nickel-based turbine blades is presented. A hybrid brazing process involves the application of a repair coating, containing a nickel-based filler material, a NiCoCrAlY and an aluminum layer by thermal spraying. The coated turbine blade is subjected to a heat treatment and a combined brazing/aluminizing process is carried out. This significantly shortens the conventional repair brazing process of turbine blades and yields superior results. The microstructure, which results from the combined brazing and aluminizing process, is characterized and the relevant diffusion processes in the coating system are illustrated. The properties of the coating and the ramifications with respect to actual applications will be discussed.