Optimizing the High‐Temperature Oxidation Resistance of a Ni‐Based Superalloy Between 900°C and 1100°C: The Pivotal Role of Hf Alloying

ABSTRACT The effects and oxidation resistance mechanism of Hf‐alloying on the oxidation behavior in a Ni‐based alloy are investigated by oxidation tests between 900°C and 1100°C and scanning electron microscope characterization. The results indicate that Hf‐alloying can prompt the formation of HfO 2 and facilitate the formation of Nb 2 O 5 around the Cr 2 O 3 precipitated on grain boundaries. Moreover, the compactness of the outer oxide layer of Cr 2 O 3 is improved to a certain extent, which restrains the amount of oxygen available to react with Al in the metal substrate. Therefore, the depth of the inner oxide layer and the size of the internal Al 2 O 3 oxides are reduced following Hf alloying. Finally, the oxidation resistance of the Ni‐based superalloy is enhanced through Hf‐alloying.