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High Temperature Oxidation Resistance of Off-Stoichiometric (Ni39.6Co29.3Cr10Al15.8Ta3.3Nb2)98.5B1.5 Chemically Complex Intermetallic Alloy
Off-stoichiometric boron-doped chemically complex intermetallic alloys (CCIMAs) have recently emerged as a new avenue for overcoming the low temperature brittleness of ordered superlattices. However, their behavior at high temperatures remains unexplored. In this study, a novel (Ni39.6Co29.3Cr10Al15.8Ta3.3Nb2)98.5B1.5 CCIMA was prepared and its oxidation resistance over a wide temperature range (500 °C–950 °C) was studied. The sample exhibited a dual-phase microstructure consisting of ordered L12 grains and a disordered Cr-rich BCC phase at the grain boundaries. The CCIMA sample demonstrated outstanding oxidation resistance at 500 °C, 750 °C, and 950 °C, showing no signs of pest oxidation and exhibiting low mass gain rates of 8.05 × 10-5 mg2 cm-4 h-1, 8.97 × 10-5 mg2 cm-4 h-1 and 5.39 × 10-4 mg2 cm-4 h-1, respectively. At temperatures above 700 °C, Al2O3 and CrTaO4 oxide layers formed on the surface, significantly hindering further oxidation of the sample. This study demonstrates how chemical composition can be exploited to synergistically develop protective oxide layers on the surface of CCIMAs.