Investigation on the Lifespan of a Copper-Based High-Entropy Rare-Earth Zirconate (La0.2Gd0.2Er0.2Y0.2Yb0.2)2(Zr0.75Ce0.25)2O7 Coating

Copper is valued in ultra-high-temperature cooling equipment for its excellent thermal conductivity, but its low melting point limits service life under extreme conditions. Thermal barrier coating (TBC) technology provides heat isolation and erosion resistance. However, existing TBCs cannot meet ultra-high temperature (>1200 °C) protection requirements for copper substrates. The poor heat resistance of copper also imposes stringent challenges on TBC fabrication and longevity, making compatible TBC development critically important. This study employed a prepared by lab high-entropy rare-earth zirconate, (La 0.2 Gd 0.2 Er 0.2 Y 0.2 Yb 0.2 ) 2 (Zr 0.75 Ce 0.25 ) 2 O 7 (LGEYYZCO), as the coating material. Two coating configurations were prepared via spray granulation and atmospheric plasma spraying on copper, with yttria-stabilized zirconia (YSZ) coatings fabricated for comparison. The phase composition, microstructure, bonding strength, microhardness, wear resistance, and thermal cycling performance were comprehensively evaluated. Results showed the LGEYYZCO coating possessed a denser structure than YSZ. Coating density proved critical for lifespan on copper substrates; higher density improved overall properties by hindering oxygen infiltration, reducing substrate oxidation, and extending thermal cycling life. A double-layer system with an LGEYYZCO top coat and YSZ interlayer performed best. This study provides theoretical and practical guidance for protecting copper-based high-temperature equipment, offering potential for extended service life and sustainable industrial application.