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<p>Lanthanum zirconate (LZ) ceramic is considered a promising alternative to yttria-stabilized zirconia (YSZ) for thermal barrier coatings (TBCs). However, its intrinsic brittleness and limited wear resistance restrict practical deployment. This study investigates three coating systems: pure LZ (1C), LZ–CeO<sub>2</sub> (2C) and LZ–CeO<sub>2</sub>–graphene (3C) deposited on an Inconel 718 substrate. XRD and Raman spectroscopy confirmed the incorporation of pyrochlore LZ, fluorite CeO<sub>2</sub> and multilayer graphene. Nanoindentation revealed hardness values of 4.48&#xa0;GPa (1C), 3.61&#xa0;GPa (2C) and 3.72&#xa0;GPa (3C), and elastic moduli of 252.03&#xa0;GPa, 176.79&#xa0;GPa and 155.76&#xa0;GPa. Enhanced toughness and strain tolerance were indicated by increased H/E and H<sup>3</sup>/E<sup>2</sup> ratios in 3C, which demonstrated superior resistance to plastic deformation and crack propagation. Scratch testing showed reduced friction coefficients for composite samples (0.151 for 2C and 0.144 for 3C) compared to pure LZ (0.286). SEM and EDX confirmed denser microstructures and uniform elemental dispersion. Porosity showed significant reduction in 2C and a moderate increase in 3C due to graphene incorporation. Air oxidation improved oxidation resistance in composite coatings, with reduced diffusion pathways and stabilized thermally grown oxides. The synergistic effect of CeO<sub>2</sub> and graphene nanosheets enhanced mechanical integrity, toughness and oxidation resistance, establishing LZ–CeO<sub>2</sub>–graphene composites as robust candidates for next-generation TBCs.</p>

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Mechanical Performance of Lanthanum Zirconate–Cerium Oxide–Graphene-Based Nanohybrid Composite Coatings for High-Temperature Thermal Barrier Applications

  • 期刊论文

  • 发表日期：

    2026年6月1日

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  • Sankar Jayaraj,
  • Suresh Kumar Shanmugam,
  • Aminul Islam,
  • Pushpender Singh,
  • Anup Kumar Keshri

摘要

Lanthanum zirconate (LZ) ceramic is considered a promising alternative to yttria-stabilized zirconia (YSZ) for thermal barrier coatings (TBCs). However, its intrinsic brittleness and limited wear resistance restrict practical deployment. This study investigates three coating systems: pure LZ (1C), LZ–CeO2 (2C) and LZ–CeO2–graphene (3C) deposited on an Inconel 718 substrate. XRD and Raman spectroscopy confirmed the incorporation of pyrochlore LZ, fluorite CeO2 and multilayer graphene. Nanoindentation revealed hardness values of 4.48 GPa (1C), 3.61 GPa (2C) and 3.72 GPa (3C), and elastic moduli of 252.03 GPa, 176.79 GPa and 155.76 GPa. Enhanced toughness and strain tolerance were indicated by increased H/E and H3/E2 ratios in 3C, which demonstrated superior resistance to plastic deformation and crack propagation. Scratch testing showed reduced friction coefficients for composite samples (0.151 for 2C and 0.144 for 3C) compared to pure LZ (0.286). SEM and EDX confirmed denser microstructures and uniform elemental dispersion. Porosity showed significant reduction in 2C and a moderate increase in 3C due to graphene incorporation. Air oxidation improved oxidation resistance in composite coatings, with reduced diffusion pathways and stabilized thermally grown oxides. The synergistic effect of CeO2 and graphene nanosheets enhanced mechanical integrity, toughness and oxidation resistance, establishing LZ–CeO2–graphene composites as robust candidates for next-generation TBCs.