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

Abstract

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.