High-sulfur coal ash hot corrosion behavior of AlxCrFeNi(3-x) eutectic high-entropy alloys with different FCC/B2 phase ratio

Al x CrFeNi (3-x) (x=0.75, 0.8, 0.85, and 0.9) eutectic high-entropy alloys with different FCC/B2 phase ratios were prepared by vacuum arc melting, and their hot corrosion behavior was investigated in a simulated high-sulfur coal-ash environment at 850℃. All alloys exhibited dual-phase FCC + B2 microstructures, in which the FCC phase was enriched in Cr and Fe, whereas the B2 phase was enriched in Al and Ni. With increasing Al content, the B2 phase volume ratio increased from 20.48% to 66.39%. Compared to conventional heat-resistant steels (316H, HR3C, and S30432), all alloys exhibited superior hot corrosion resistance under same condition. After 150 h of corrosion, Al 0.75 showed a slight mass loss of -1.72 mg/cm 2 , whereas Al 0.8 , Al 0.85 , and Al 0.9 exhibited mass gains of 3.13, 2.34, and 1.41 mg/cm², respectively. The high fraction of B2 phase within the Al 0.9 alloy provided a sufficient Al reservoir for the formation of a continuous and compact Al 2 O 3 outer scale, which effectively suppressed internal oxidation and sulfidation.