Study on improvement of oxide layer and properties of plasma sprayed alumina in thermal barrier coatings

Thermal barrier coatings (TBC) have been used to improve the efficiency of turbine engine by providing the capability to sustain significant temperature gradient across the coating. TBC failure occurs easily at the interface between the metallic bondcoat and topcoat. Alumina was proposed as a potential candidate as an interlayer to improve the oxidation resistance of thermal barrier coating due to its low oxygen diffusivity against the harsh environment. The mechanical properties, thermal behaviour and high temperature oxidation resistance of the coatings formed by gas tunnel type plasma spraying were investigated in this study. The results showed that this system exhibits the improvement of mechanical properties of the coating and oxidation resistance. This interlayer is preferred in order to minimize the detrimental effect of phase transformation of gamma-Al2O3 to alpha-Al2O3.