Abstract
In previous work, a thermal spray multilayer system consisting of ZrO2 and an MCrAlY top coat showed promising results regarding oxidation behavior of the γ-TiAl substrates tested, which encouraged further research activities. Diffusion of substrate material was successfully inhibited by a ceramic ZrO2 coating. A building up of a dense and stable oxide layer could be achieved by additional application of an MCrAlY top coat, leading to improved oxidation resistance and thus showing feasibility. In this work the main focus for development was put on enhancing adhesion and lowering residual stresses of the coatings in order to allow long term and cyclic testing without delamination taking place. Being a very brittle material, Gamma Titanium Aluminides require special surface treatment to enable roughening which is crucial for a strong mechanical bond between substrate and coating. Alternatives to conventional grit blasting as a standard preparation method were investigated. These were micro-abrasive blasting and blasting at elevated temperature (≈300-550 °C) to allow a more ductile behavior. The paper will highlight the implications by means of these measures and will also show the present development status of the multilayer system.
