Solid Particle Erosion Performance and Damage Mechanism of AlTiN Coating

Aircraft, when operating in a sandy environment, can experience severe solid particle erosion damage to gas turbine engine components, such as compressor rotor blades, vanes, and impeller blisks/wheels, due to sand particle ingestion into the engine. Material removal from these components as the result of erosion not only leads to significant aerodynamic losses, but also results in their structural weakening. Applying erosion-resistant coatings on airfoil surfaces has been proven effective in extending the serviceable life of engine components. In this study, cathodic arc evaporated AlTiN was explored for its potential as an erosion-resistant coating for the compressor blades and helicopter impellers applications. AlTiN coating, along with baseline TiN coating, was subjected to gas jet sand erosion testing under different particle impingement angles and velocities. The erosion rates of the AlTiN coating were found to be much lower than those of the TiN coating in the entire range of the tested conditions. While the TiN coating mainly suffered from severe brittle erosion damage through coating chipping, the AlTiN coating exhibited only mild erosion damage through microcutting by sand particles. To include the aerodynamic effect on airfoil erosion in the consideration, dynamic wind tunnel sand erosion testing was also performed on AlTiN- and TiN-coated propeller blades. The results of these tests also confirmed superior erosion resistance of the AlTiN coating over that of the TiN coating.