Evaluation of microstructure, nano mechanical and nano scratch properties of thermal barrier coating at elevated temperatures

Thermal barrier coatings (TBCs) are widely employed to protect turbine and aerospace components from extreme thermal environments. In this work, multilayer TBCs consisting of Chromium/Cobalt – Aluminium – Yttrium (CoAlY) bond coats and 8 wt.% Y₂O₃ – ZrO₂ (YSZ) top coats were deposited on Superni-718 substrates by DC/RF magnetron sputtering at substrate temperatures of 100, 150, and 200°C. The influence of deposition temperature on microstructure, Nano-mechanical properties, and scratch resistance was systematically evaluated. X-ray diffraction confirmed the formation of crystalline YSZ phases, while FE-SEM observations revealed dense and uniform columnar morphologies with coating thicknesses in the range of ∼0.96–1.73 µm. Elemental uniformity across the multilayer system was verified by EDS analysis. Nano-indentation results showed a clear dependence on deposition temperature, with hardness values increasing from 4.6 ± 0.3 GPa at 100°C to a maximum of 5.8 ± 0.2 GPa at 150°C, accompanied by an elastic modulus of 99 ± 4 GPa. Nano-scratch and SPM/AFM analyses indicated improved adhesion and reduced damage at 150°C, suggesting this temperature provides an optimal balance between mechanical performance and interfacial stability.