Abstract
Aluminide coating is prepared on K438 Ni-based superalloy by pack cementation. The hot corrosion test of as-received and pre-oxidation aluminide coating in Na2SO4 salt are carried out at 1050°C. The coating morphologies, phase composition, and corrosion products are characterized by XRD, SEM, EDS, and TEM. The conclusion is that the pre-oxidation aluminide coating has excellent hot corrosion properties. After hot corrosion, the oxide scale of pre-oxidation aluminide coating is the thinnest and maintains good integrity. However, the oxide scale of as-received aluminide coating fluctuates greatly and there are corrosion cavities. CrS is formed in the alloy immediately below the oxide scale for the two coating systems.
Highlights
Ni-based superalloy has excellent creep resistance, high rupture strength, and corrosion resistance, so it is a perfect material for key components of aeroengines (He et al, 2015; Sun et al, 2015)
The oxide scale formation leads to the mass change and the mass loss caused by oxide scale exfoliation or dissolution are obtained, and the corresponding conclusions are given in the experiment
The NiAl2O4 spinel phase can be found on both coatings, but the peak intensity of NiAl2O4 phase on preoxidation aluminide coating is weaker than on as-received aluminide coating
Summary
Ni-based superalloy has excellent creep resistance, high rupture strength, and corrosion resistance, so it is a perfect material for key components of aeroengines (He et al, 2015; Sun et al, 2015). They must be subjected to high temperature oxidation and hot corrosion by O2 or other corrosive substances, for example, sulfur (Kosieniak et al, 2012; Yang et al, 2020). It is necessary to apply protective coating on the surface of Ni-based superalloy to improve its high temperature properties
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