Corrosion behaviors of Lu4Hf3O12 thermal/environmental barrier coatings to molten CMAS attack at 1300-1500 °C

Rare-earth hafnates are considered as promising thermal/environmental barrier coatings (T/EBCs) materials due to their excellent high-temperature properties. The attack of CaO-Al2O3-MgO-SiO2 (CMAS) has been identified as one of the key factors affecting the lifetime of the T/EBCs top layer, but the response to CMAS corrosion of rareearth hafnates is still understudied. In this work, the CMAS corrosion behaviors and mechanism of plasmasprayed Lu4Hf3O12 coatings were investigated at 1300, 1400, and 1500 degrees C. The results indicated that Lu4Hf3O12 possessed excellent CMAS resistance, while the temperature can significantly influence the corrosion behavior of the coating. At 1300 degrees C, Lu4Hf3O12 reacted with CMAS to form apatite, fluorite and garnet products, the slow reaction rate between Lu4Hf3O12 and CMAS led to a reaction layer of only 24 mu m after 25 h. As the corrosion temperature elevated, garnet showed redissolution after prolonged reaction time, and cuspidine product was generated with increasing corrosion depth. The generation of cuspidine at 1400 and 1500 degrees C effectively depleted all the components of the CMAS melt, which limited its penetration into the coating.