High-temperature oxidation behavior of a single-crystal high-entropy superalloy strengthened by dense intermetallic nanoparticles

作者：Xiao, Weicheng; Ju, Jiang; Liu, Shaofei; Xiao, Bo; Zhou, Yinghao; Kai, Ji-jung; Zhao, Yilu; Yang, Tao^*

来源：Science China-Materials, 2023, 66(11): 4239-4250.

DOI：10.1007/s40843-023-2604-3

• high-entropy superalloy
• high-temperature oxidation
• FIB-TEM
• oxide scale
• oxidation diffusion

The oxidation behavior of a newly developed single-crystal L1(2)-strengthened Co-rich high-entropy superalloy, Co41Ni35Al11.5Ta2.5Cr4Ti6 (at%), was investigated systematically in air at 800, 900, and 1000 degrees C. The results reveal that this alloy demonstrates excellent oxidation resistance from 800 to 1000 degrees C. At 800 degrees C, a bilayer oxide scale was formed, consisting of a TiO2/Al2O3 mixture layer and a Cr2O3 layer. The continuous but non-dense Cr2O3 layer could not effectively inhibit internal oxidation and internal nitridation. Complex hierarchical-structure oxide scale formed at 900 and 1000 degrees C, mainly composed of spinels, Cr2O3, TiTaO4, and Al2O3. Surprisingly, an anomalous improvement in oxidation resistance was found in a temperature range from 900 to 1000 degrees C. Specifically, the formation of a more complex and continuous five-layer oxide scale at 1000 degrees C, particularly the bottom compact Al2O3 layer, endows the alloy with exceptional resistance to oxidation at 1000 degrees C.