Optimizing deposition temperature for NiCoCrAlYTaHf/ Y2O3-ZrO2 dual-layer coatings synthesized by DC magnetron sputtering

Nanostructured dual-layer thermal barrier coatings (TBCs) are essential for improving the service life and efficiency of high-temperature components in gas turbines and aerospace applications. In this study, a dual-layer TBC comprising a NiCoCrAlYTaHf metallic bond coat and an 8 wt.% yttria-stabilized zirconia (Y 2 O 3 –ZrO 2 ) ceramic top coat was synthesized on Superni-718 substrates using direct current (DC) magnetron sputtering at substrate temperatures of 100 °C, 200 °C, and 300 °C. Field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDS) showed progressive densification, improved columnar grain structure, and stronger interfacial bonding with increasing deposition temperature. X-ray diffraction confirmed the presence of tetragonal zirconia and γ-Ni phases, with crystallite size increasing from 6.4–11.4 nm at 100 °C to 17–31 nm at 200 °C and 16–29 nm at 300 °C as deposition temperature increased. Nanoindentation analysis revealed the highest hardness of 11.25 ± 0.18 GPa at 300 °C, while the elastic modulus values ranged from 166.7 GPa to 173.7 GPa across all deposition temperatures, indicating stable elastic behaviour. Quantitative surface profilometry demonstrated lower roughness at elevated temperatures. These results indicate that DC magnetron sputtering enables precise control over coating structure and mechanical performance, with higher deposition temperatures producing coatings that exhibit enhanced density, mechanical strength, and thermal durability, making them suitable for advanced thermal applications.