High Temperature Oxidation and Surface Microstructure Evolution of Nickel-Based Superalloy GH3039 via Aluminized Embedding

This study investigates the effect of an aluminized coating on the oxidation resistance of GH3039 superalloy. A powder embedding technique at 900°C with 60 wt % aluminum was employed to prepare the coating. The phase composition and surface morphology of oxidation products were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Untreated and aluminized samples were subjected to oxidation at 800, 900, and 1000°C for 100 h. Post-treatment, the GH3039 alloy exhibited a uniformly distributed aluminized layer about 90 μm thick. This layer comprised three distinct sub-layers: a top layer with Ni2Al3 and minor NiAl3 phases, a middle layer of mainly Ni2Al3, and a β-NiAl phase-rich bottom layer. Oxide weight measurements indicated an initial rapid increase followed by a significant reduction at high temperatures, primarily due to Cr2O3 volatilization into gaseous CrO3. Oxidation curves for the aluminized samples showed reduced and stable weight gain patterns, adhering mostly to the parabolic law with no further increase at advanced stages. The untreated samples presented a porous oxide film with complex components including Cr2O3, NiCr2O4, TiO2, which adversely affected their oxidation resistance. In contrast, the aluminized samples predominantly displayed an Al2O3 film that transitioned from flaky θ-Al2O3 to a compact α-Al2O3 structure at increased temperatures, thereby significantly enhancing the alloy’s resistance against high-temperature oxidation.