Effects of alloyed aluminum and titanium on the oxidation behavior of INCONEL 740 superalloy

• Compositional effect on water vapor oxidation of INCONEL 740 has been investigated.
• Addition of Al up to 2.4 wt.% at low Ti contents exhibited the lowest mass gain.
• Aluminum oxidation was observed, especially at high angle Ni boundaries.
• High Ti contents lead to internal titanium nitride and oxide formation.
• Dominant surface oxide was Cr2O3, varying in grain size, thickness, and cavity size.

An attempt has been made to improve the oxidation resistance of the INCONEL 740 nickel-base superalloy by altering its composition. The effects of aluminum and titanium were studied in particular. Electron microscopy was utilized to characterize and quantify the oxides. The addition of aluminum up to 2.4 wt.% at low titanium contents provides the lowest mass gain. Aluminum internal and grain boundary oxidation, especially at nickel high-angle boundaries, was observed. The surface oxide consists of predominantly Cr2O3. The oxide thickness and defect density increase with the increasing titanium content.

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