Plasma sprayed Yb4Hf3O12 thermal barrier coatings with excellent thermophysical properties and robust CMAS corrosion resistance

Abstract

Here we reported atmospheric plasma sprayed Yb4Hf3O12 as a novel thermal barrier coating (TBC) and its comprehensive properties including phase composition, high-temperature stability, thermal expansion coefficient (TEC) and thermal conductivity were characterized. XRD and Raman results co-verify as-sprayed Yb4Hf3O12 coating is composed of disordered fluorite structure, and would return to its original δ structure during 1300 °C exposure. The linear relationship between thermal expansion rate and temperature indicates the fluorite→δ phase transformation accompanies no significant volumetric effect and thus might not pose detriment to coating durability. The Yb4Hf3O12 coating also combines many attractive characteristics, from high TEC (near 10.3 × 10−6 K−1, 200-1500 °C) and thermal insulation capability (0.95–1.12 W/m·K, room temperature-1000 °C) to thermal stability, and sintering resistance. We also comparatively studied the infiltration behaviour of natural volcanic ash and synthetic sandy CMAS within coating at 1250 °C. Robust corrosion resistance of Yb4Hf3O12 coating are demonstrated, especially against volcanic ash. These preliminary results suggest that Yb4Hf3O12 might be a lone ceramic topcoat and capable of operating well beyond the limits of traditional yttria stabilized zirconia (YSZ).