Oxidation performance of nano-scale multilayer coatings on γ-TiAl

There is a major drive to introduce γ-TiAl into gas turbine engines in order to reduce weight. However, this will require the development of coatings that protect against oxidation at high temperature, but do not adversely affect the mechanical properties. This work reports the high temperature degradation mechanisms of a nanoscale CrAlYN/CrN multilayer coating deposited on γ-TiAl(8Nb) by a combined high power impulse magnetron sputtering / unbalanced magnetron sputtering. Detailed TEM/STEM of FIB prepared specimens from isothermal static oxidation tests at 850°C for up to 1030 hours is presented. The evolution of the complex oxide structure and the implications for future coating development is discussed.