Regulation of high-temperature oxidation behavior and crack inhibition mechanism in Haynes 230 alloy fabricated by laser powder bed fusion

With the advancement of additive manufacturing (AM) technology, the oxidation resistance of superalloys became increasingly important. Haynes 230 alloy, which was widely used in extreme environments because of its excellent high-temperature properties, was of considerable interest because of its oxidation behavior. In this study, Haynes 230 alloy samples were fabricated by laser powder bed fusion (LPBF) to investigate the effect of powder size on oxidation behavior and to elucidate the mechanisms underlying crack suppression and oxidation resistance. The results showed that samples fabricated from coarse powders (diameter ≥ 40 μm) exhibited better oxidation resistance than those fabricated from fine powders (diameter ≤ 14 μm). The oxidation process underwent three stages: diffusion-controlled oxide growth, oxide scale spallation, and oxidation dominated by gas-phase reactions. The oxide scale consisted of three distinct layers: an inner Al₂O₃ layer, a middle Cr₂O₃ layer, and an outer TiO₂ layer. Oxide scale spallation was initiated in regions containing microcracks, and its severity increased with increasing microcrack density. Moreover, samples fabricated from coarse powders showed a lower crack density. Grain refinement hindered microcrack propagation and alleviated thermal stress, thereby providing a controllable means of tailoring oxidation resistance. These findings provided a theoretical basis for powder size selection in AM and offered guidance for improving the service performance of superalloys in extreme environments.