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<p>At the beginning of the 21st century, the classical yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) reached their maximum operating temperature (1200°C). A further increase in the operating temperature and associated gain in the efficiency of gas turbine engines became possible through the complex stabilization of ZrO<sub>2</sub>; the use of other compounds (oxides with fluorite (La<sub>2</sub>Ce<sub>2</sub>O<sub>7</sub>), pyrochlore (La<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub>, La<sub>2</sub>Hf<sub>2</sub>O<sub>7</sub>), magnetoplumbite (LaMgAl<sub>11</sub>O<sub>19</sub>), perovskite (SrZO<sub>3</sub>), and other structures); and the design of functionally graded and two-layer TBCs. In the latter case, the bottom layer is mainly YSZ, whose coefficient of thermal expansion (CTE) matches that of the bound coat. Various materials with low thermal conductivity are proposed as the topcoat (an overview of the efforts focusing on the development of La<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub> (LZ<sub>2</sub>)/YSZ TBCs is presented in the first paper of the series). Two-layer LZ<sub>2</sub>/YSZ TBCs can be successfully produced by all available application methods: atmospheric plasma spraying (APS), electron-beam physical vapor deposition (EB-PVD), spark plasma sintering (SPS), etc. The LZ<sub>2</sub> and YSZ phases exhibit good chemical compatibility even after sintering at 1400°C for 24 h. The mismatch in the CTEs of the layers remains a serious problem. The LZ<sub>2</sub>/YSZ coatings demonstrate better thermal shock resistance compared to nanostructured and conventional YSZ TBCs. To produce high-quality two-layer coatings with the LZ<sub>2</sub> topcoat, APS parameters should be lowered to avoid lanthanum losses. Reducing the elastic modulus of two-layer TBCs is useful for decreasing the crack propagation tendency. The LZ<sub>2</sub> phase reduces the oxygen permeability of the ceramic coat in two-layer TBCs, thus preventing the bond coat oxidation and the rapid growth of thermally grown oxides. The twolayer LZ<sub>2</sub>/YSZ TBCs show higher resistance to hot corrosion caused by Ca–Mg–Al silicates (CMAS) and V<sub>2</sub>O<sub>5</sub>+Na<sub>2</sub>SO<sub>4</sub> compared to their single-layer counterparts. The doping of LZ<sub>2</sub> with CeO<sub>2</sub> increases the CTE of two-layer APS coatings, improving their efficiency. The overview of two-layer La<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub>(LZ<sub>2</sub>)/YSZ TBCs confirms their advantages over single-layer ones, because each layer contributes to improving the properties and mitigating the weaknesses of the coatings, ultimately enabling higher operating temperatures and longer service lives of power equipment.</p>

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Multilayer Coatings as a New Stage in the Development of Modern Highly Effective Thermal Barrier Coatings I. Two-Layer La2Zr2O7 (LZ2)/YSZ Thermal Barrier Coatings

  • 期刊论文

  • 发表日期：

    2025年5月1日

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  • S. M. Lakiza,
  • M. I. Hrechaniuk,
  • A. O. Makudera,
  • I. O. Marek,
  • O. K. Ruban,
  • V. P. Red’ko,
  • V. B. Shmybelskii,
  • O. V. Dudnik

摘要

At the beginning of the 21st century, the classical yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) reached their maximum operating temperature (1200°C). A further increase in the operating temperature and associated gain in the efficiency of gas turbine engines became possible through the complex stabilization of ZrO2; the use of other compounds (oxides with fluorite (La2Ce2O7), pyrochlore (La2Zr2O7, La2Hf2O7), magnetoplumbite (LaMgAl11O19), perovskite (SrZO3), and other structures); and the design of functionally graded and two-layer TBCs. In the latter case, the bottom layer is mainly YSZ, whose coefficient of thermal expansion (CTE) matches that of the bound coat. Various materials with low thermal conductivity are proposed as the topcoat (an overview of the efforts focusing on the development of La2Zr2O7 (LZ2)/YSZ TBCs is presented in the first paper of the series). Two-layer LZ2/YSZ TBCs can be successfully produced by all available application methods: atmospheric plasma spraying (APS), electron-beam physical vapor deposition (EB-PVD), spark plasma sintering (SPS), etc. The LZ2 and YSZ phases exhibit good chemical compatibility even after sintering at 1400°C for 24 h. The mismatch in the CTEs of the layers remains a serious problem. The LZ2/YSZ coatings demonstrate better thermal shock resistance compared to nanostructured and conventional YSZ TBCs. To produce high-quality two-layer coatings with the LZ2 topcoat, APS parameters should be lowered to avoid lanthanum losses. Reducing the elastic modulus of two-layer TBCs is useful for decreasing the crack propagation tendency. The LZ2 phase reduces the oxygen permeability of the ceramic coat in two-layer TBCs, thus preventing the bond coat oxidation and the rapid growth of thermally grown oxides. The twolayer LZ2/YSZ TBCs show higher resistance to hot corrosion caused by Ca–Mg–Al silicates (CMAS) and V2O5+Na2SO4 compared to their single-layer counterparts. The doping of LZ2 with CeO2 increases the CTE of two-layer APS coatings, improving their efficiency. The overview of two-layer La2Zr2O7(LZ2)/YSZ TBCs confirms their advantages over single-layer ones, because each layer contributes to improving the properties and mitigating the weaknesses of the coatings, ultimately enabling higher operating temperatures and longer service lives of power equipment.