Effect of Hf/Zr Ratio on Mechanical Properties and High-Temperature Performance of A6Ta2O17 Thermal Barrier Coatings

A series of A 6 Ta 2 O 17 /8YSZ double-ceramic-layer thermal barrier coatings (TBCs) with varying Hf/Zr molar ratios (1:2, 1:1, and 2:1) are fabricated via atmospheric plasma spraying (APS). The effect of the Hf/Zr ratio on the microstructure, mechanical properties, and high-temperature performance of the coatings under both thermal cycling and thermal shock conditions is systematically investigated. As Hf content increases, the nano-hardness decreases markedly from 16.5 to 12.8 GPa, whereas the intrinsic elastic modulus shows a modest increase from 222.8 to 232.8 GPa. Concurrently, the interfacial fracture toughness decreases from 0.96 to 0.62 MPa·m 1/2 . The equimolar H1Z1 coating (Hf/Zr = 1:1) demonstrates the highest thermal cycling resistance (2371 cycles), a performance attributed to a failure mechanism involving multi-channel stress release at the interfaces. Under thermal shock conditions, the H1Z1 coating also exhibits a prolonged thermal shock lifetime of 2180 cycles. In contrast, the Hf-rich composition (Hf/Zr = 2:1) fails catastrophically after only 682 cycles, due to insufficient erosion resistance, marked by pit formation and progressive thinning. These results highlight the equimolar H1Z1 coating as offering an optimal balance of mechanical compatibility and service durability, making it the most promising candidate among the investigated compositions for advanced TBCs applications.