High-temperature oxidation performance of additively manufactured Inconel 625 superalloy

The high-temperature oxidation behavior of bulk-wall Inconel 625 produced by wire-based directed energy deposition (DED) was systematically investigated for as-deposited and solution heat-treated samples at 900 °C and 1100 °C for up to 100 h. Oxidation was strongly temperature-dependent, with a continuous and compact Cr 2 O 3 layer forming at 900 °C, whereas partial breakdown of the chromia scale at 1100 °C led to coarse Ni-rich oxide particles. Cross-sectional analyses revealed a multilayered oxide structure with an outer Cr 2 O 3 layer and an inner Nb 2 O 5 -rich transition zone, resulting from selective oxidation and diffusion processes. Solution heat treatment homogenized the microstructure by dissolving interdendritic Nb and Crrich secondary phases, moderately enhancing oxidation resistance at elevated temperatures. Density functional theory simulations confirmed preferential O adsorption on Nb- and Cr-rich sites, consistent with the experimentally identified Cr 2 O 3 and Nb 2 O 5 phases. This combined experimental and computational study elucidates the role of microstructural homogeneity and element-specific diffusion in controlling oxidation mechanisms in wire-based EDE-fabricated Inconel 625.