TEM study of the evolution of sputtered Ni+CrAlYSiHfN nanocomposite coating with an AlN diffusion barrier at high temperature

• A novel nanocomposite Ni+CrAlYSiHfN/AlN duplex coating was fabricated on superalloy used in the aeroengine.
• The growth of oxides layer on the coating system was studied by TEM.
• The microstructure evolution mechanism of the coating at high temperature was studied.
• The nanocomposite Ni+CrAlYSiHfN coating exhibited good oxidation resistance.

MCrAlY (M denotes Ni and/or Co) coatings are widely used on the turbine blades to protect the aeroengine at high temperature. However, the interdiffusion between coating/substrate and the coefficient of thermal expansion (CTE) mismatch between protective oxides layer/coating are the main factors that limit the service lifetime of MCrAlY coatings. In this work, a Ni+CrAlYSiHfN/AlN nanocomposite duplex coating system was designed to improve the weakness of conventional MCrAlY coatings. The nanocomposite coating system exhibited a low oxidation rate in the 1000 °C isothermal oxidation test and the oxidation rate constant of the coating system was 6.33 ∗ 10− 13 g2 cm− 4 s− 1 at the first 20 h, and then the TGO grew at a low constant of 1.49 ∗ 10− 13 g2 cm− 4 s− 1 until 200 h. Besides, the AlN diffusion barrier effectively inhibited the interdiffusion between coating/substrate. The evolution of coating microstructures and thermal growth oxides (TGO) at high temperature were studied with the aid of transmission electron microscopy.