Structure characterization of the oxide film on FGH96 superalloy powders with various oxidation degrees

The structure of the oxide film on FGH96 alloy powders significantly influence mechanical properties of superalloys. In this study, FGH96 alloy powders with various oxygen contents were investigated by HRTEM and 3DAP techniques to elucidate the structure evolution of the oxide film. EDS analysis reveals the presence of two distinct components in the oxide film of the alloy powders: Amorphous oxide layer covering the γ matrix and amorphous oxide particles above the carbide. The alloying elements within the oxide layer emerges a laminated distribution, followed by Ni, Co, Cr, Al/Ti, which is attributed to the decreasing oxygen equilibrium pressure as oxygen diffuses from the surface into the γ matrix. On the other hand, Ti enrichment was observed in the oxide particles caused by the oxidation and decomposition of the carbide phase. Comparative analysis of the oxide film with oxygen contents of 140 ppm, 280 ppm, and 340 ppm shows similar elements distributions, while the thickness of the oxide film varies approximately at 9 nm, 14 nm, and 30 nm, respectively. These findings provide valuable insights into the structure of FGH96 alloy powders.