Microstructure and hot corrosion behavior of Al-Ce-Y coatings on DZ125 nickel-based alloy prepared by pack cementation process

Abstract

In order to improve the hot corrosion resistance of DZ125 alloy, Ce-Y modified aluminum coatings were prepared on DZ125 alloy by pack cementation process at 950 °C for 2 h. The microstructure, phase constitution and formation mechanism of the coatings were investigated. The hot corrosion behaviors of DZ125 alloy and the coatings in molten salt environment of 25%K₂SO₄+75%Na₂SO₄ (mass fraction) at 900 °C were studied. Results show that the obtained Al-Ce-Y coatings were mainly composed of Al₃Ni₂, Al₃Ni and Cr₇Ni₃, with a thickness of about 120 μm. After hot corrosion test, DZ125 alloy suffered catastrophic hot corrosion and serious internal oxidation and internal sulfidation arose. Two layers of corrosion products formed on surfaces of DZ125 alloy, including the outer layer consisting of Cr₂O₃ and NiCr₂O₄, and the inner layer of Al₂O₃, Ni₃S₂ and Ni-base solid solution. After being coated with Al-Ce-Y coating, the hot corrosion resistance of DZ125 alloy is improved notably, due to the formation of a dense scale mainly consisting of Al-rich Al₂O₃ in the coating layer.

Keywords

DZ125 alloy / Ce-Y modified aluminum coating / structure / hot corrosion

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