Long-term stability and performance of nanostructured thermal barrier coatings deposited by magnetron sputtering on superalloys: A review

Nanostructured thermal barrier coatings (TBCs) enhance thermal insulation in advanced gas turbines, enabling higher operating temperatures and increased power output. These coatings support the deposition of high-quality thin films, even on substrates with intricate geometries. This process ensures precise film composition and structure control, improving the coating's performance and longevity. In this review paper, the effect of nanostructuring on TBC performance is thoroughly reviewed and discussed in terms of microstructural transformations, phase stability, degradation mechanisms, thermal conductivity, and interface stability when subjected to working conditions. A significant challenge in TBC durability is oxidation-induced weight gain with an associated increase in failure mechanisms’ occurrence rates, which affects long-term performance. Comparative kinetic studies indicate that the coating of nanostructured yttria stabilized zirconia compared to the micron-sized coatings shows much lower weight gain. The superior oxidation resistance and reduced mass accumulation of nanostructured YSZ coatings are demonstrated by their lower parabolic rate constant (K_p) of 3.36 × 10⁻⁷ mg² cm⁻⁴ s⁻¹, compared to 6.23 × 10⁻⁷ mg² cm⁻⁴ s⁻¹ for micrometer-sized coatings. Additionally, increasing the nanostructure loading to approximately 8% unmelted nanoparticle matrix content enhances thermal cycling life, thereby extending the longevity of TBCs. This paper reviews the development of nanostructured TBC design and achievements and challenges for extreme high-temperature gas turbine applications.