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<p>Thermal barrier coatings (TBCs) with low thermal conductivities and high coefficient of thermal expansion (CTE) are needed for the protection against thermal stress and insulation of gas-turbine engines. In the present study, mechanical and thermal characteristics of plasma-sprayed In-situ composite Gd<sub>2</sub>Nb<sub>2</sub>O<sub>7</sub>-GdNbO<sub>4</sub> (CGN) coatings were analysed. The coating has shown the Young’s modulus, hardness and fracture toughness of 139 ± 4.4, 7.1 ± 0.75&#xa0;GPa and as 3.2 ± 0.26&#xa0;MPa-m<sup>0.5</sup>. The developed coatings exhibited very low thermal conductivity (1.7&#xa0;W/m-K at 1200&#xa0;°C) and very high CTE (16.3 × 10<sup>−6</sup>&#xa0;/K at 1000&#xa0;°C), suitable for TBC application. This is attributed to enhanced phonon scattering due to the increased mass-disorder with the formation of Gd<sub>2</sub>Nb<sub>2</sub>O<sub>7</sub> along with GdNbO<sub>4</sub> in the composite coating. Additionally, defects like vacancies, dislocations, incoherent twin boundaries, and formation of Gd<sub>2</sub>Nb<sub>2</sub>O<sub>7</sub> (pyrochlore phase) have also contributed significantly to the very low thermal conductivity and very high thermal expansion coefficient in such composite coatings, strongly advocating their efficacy for future TBCs.</p>

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Thermophysical Properties of Plasma Sprayed In Situ Gd2Nb2O7-GdNbO4 Composite Coatings for Next-Gen Thermal Barrier Coatings

  • 期刊论文

  • 发表日期：

    2026年7月14日

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  • Rahul Kumar,
  • Satish Indupuri,
  • Navneet K. Singh,
  • Anup Kumar Keshri

摘要

Thermal barrier coatings (TBCs) with low thermal conductivities and high coefficient of thermal expansion (CTE) are needed for the protection against thermal stress and insulation of gas-turbine engines. In the present study, mechanical and thermal characteristics of plasma-sprayed In-situ composite Gd2Nb2O7-GdNbO4 (CGN) coatings were analysed. The coating has shown the Young’s modulus, hardness and fracture toughness of 139 ± 4.4, 7.1 ± 0.75 GPa and as 3.2 ± 0.26 MPa-m0.5. The developed coatings exhibited very low thermal conductivity (1.7 W/m-K at 1200 °C) and very high CTE (16.3 × 10−6 /K at 1000 °C), suitable for TBC application. This is attributed to enhanced phonon scattering due to the increased mass-disorder with the formation of Gd2Nb2O7 along with GdNbO4 in the composite coating. Additionally, defects like vacancies, dislocations, incoherent twin boundaries, and formation of Gd2Nb2O7 (pyrochlore phase) have also contributed significantly to the very low thermal conductivity and very high thermal expansion coefficient in such composite coatings, strongly advocating their efficacy for future TBCs.