Multilayer Gradient Design for Stress Mitigation and Durability Enhancement in Plasma-Sprayed La₂Zr₂O₇/NiCoCrAlY Coatings

Abstract:

This study systematically investigates the microstructure and high-temperature performance of plasma-sprayed La₂Zr₂O₇/NiCoCrAlY (LZO/NAY) thermal barrier coatings (TBCs) with double-layer, three-layer, and five-layer gradient architectures. To address interfacial stress accumulation caused by mismatches in thermal expansion coefficients between ceramic and metallic layers, multilayer compositional gradients were introduced. Microstructural characterization was performed using SEM, EBSD, and TEM, while finite element modeling was used to evaluate thermal insulation and stress distribution. The five-layer gradient coatings exhibited the smoothest compositional transition and most uniform stress distribution, significantly reducing interfacial stress concentration and residual stresses. Thermal shock resistance tests at 1200 °C demonstrated that the five-layer coatings withstood 24 cycles, a marked improvement compared to 18 and 3 cycles for three-layer and double-layer systems, respectively. Isothermal oxidation tests at 1000 °C further showed that gradient coatings maintained superior structural integrity, with thinner thermally grown oxide layers than the conventional system. The findings provide both theoretical and experimental evidence that compositional gradient design markedly enhances the durability and thermal stability of TBCs, offering practical strategies for advanced thermal protection in high-temperature applications.

• Periodical: Key Engineering Materials (Volume 1060)
• Pages: 23-41
• DOI: https://doi.org/10.4028/p-i3ooGd
• Online since: July 2026
• Authors: Tian Liu*, Qian Wang, Heng Nan Ding, Rui Luo
• Keywords: Interfacial Stress, La₂Zr₂O₇/NiCoCrAlY, Multilayer Gradient, Plasma-Sprayed, Thermal Barrier Coatings

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