Improved resistance to high-temperature oxidation in a fine-grained CrMnFeCoNi high-entropy alloy additively manufactured by laser powder bed fusion

초록

The high-temperature oxidation behavior of a fine-grained CrMnFeCoNi high-entropy alloy (HEA) manufactured by laser powder bed fusion (LPBF) was investigated. The LPBF-built HEA exhibited heterogeneous, fine-grained structures with a single phase. In addition, substructures induced by dislocation networks and nanosized oxides were observed within the grains. The fine-grained structure had a positive effect on the resistance to high-temperature oxidation. Oxidation tests were conducted at 900 degrees C, 1000 degrees C, and 1100 degrees C for 24 h, and the L-PBF alloy exhibited significantly lower mass gains compared to its traditionally processed counterpart (THEA). Specifically, the mass gain of the L-PBF alloy were 1.43, 3.50, and 6.47 mg/cm(2) at 900, 1000, and 1100 degrees C, respectively, whereas the THEA sample showed 1.76, 4.45, and 9.09 mg/cm(2). Moreover at 1000 degrees C, the internal oxide scale of the L-PBF alloy (similar to 50 mu m) was approximately 60 % thinner than that of the THEA (similar to 130 mu m). This refined microstructure promoted the formation of a stable and continuous Cr2O3 scale and suppressed the formation of spinel phases, thereby enhancing high-temperature oxidation resistance. By comparing with the oxidation behaviors of HEAs produced by traditional manufacturing processes, we aimed to deepen our understanding of the high-temperature oxidation behavior of HEAs fabricated via the LPBF process. Based on these results, the mechanisms underlying the excellent oxidation resistance of the LPBF-built CrMnFeCoNi HEA are discussed in detail.

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