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

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 degrees 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 degrees 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 mu m. 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.