An Investigation of a La2(Zr0.2Ti0.2Y0.2Yb0.2Nb0.2)2O7 High Entropy Oxide Coating

Thermal barrier coating (TBC) is applied to protect the hot-section components of a gas turbine engine. In the present work, a La 2 (Zr 0.2 Ti 0.2 Y 0.2 YB 0.2 Nb 0.2 ) 2 O 7 high entropy oxide was designed, fabricated by a solid-phase reaction at 1400 °C, and subjected to an investigation of its properties. The results indicate that the La 2 (Zr 0.2 Ti 0.2 Yb 0.2 Y 0.2 Nb 0.2 ) 2 O 7 high entropy oxide had a pyrochlore structure. During synthesis, a small amount of La 2 TiO 5 was produced. The thermal conductivity of the La 2 (Zr 0.2 Ti 0.2 Yb 0.2 Y 0.2 Nb 0.2 ) 2 O 7 high entropy oxide was approximately 0.8855 W·m -1 ·K -1 at room temperature. The coefficient of thermal expansion of the La 2 (Zr 0.2 Ti 0.2 Yb 0.2 Y 0.2 Nb 0.2 ) 2 O 7 high entropy oxide was approximately 9.374 × 10 −6  K −1 at 1000 °C. To improve the service life of the TBC composed of the La 2 (Zr 0.2 Ti 0.2 Yb 0.2 Y 0.2 Nb 0.2 ) 2 O 7 , a double-layer structural coating composed of La 2 (Zr 0.2 Ti 0.2 Y 0.2 YB 0.2 Nb 0.2 ) 2 O 7 and yttria-stabilized zirconia (YSZ) layers was designed and produced on a NiCoCrAlY alloy by laser cladding. The thermal cycling behavior of the double-layer coating was studied at 1050 °C. The results indicate that a La 2 (Zr 0.2 Ti 0.2 Yb 0.2 Y 0.2 Nb 0.2 ) 2 O 7 single-phase defective-fluorite high entropy oxide was produced after preparation and thermal cycling. The spallation of the double-layer coating composed of La 2 (Zr 0.2 Ti 0.2 Yb 0.2 Y 0.2 Nb 0.2 ) 2 O 7 /YSZ occurred after 70 thermal cycles at 1050 °C. The double-layer coating composed of La 2 (Zr 0.2 Ti 0.2 Yb 0.2 Y 0.2 Nb 0.2 ) 2 O 7 /YSZ can increase the thermal cycling lifetime of TBCs containing high entropy oxides.