Formation Mechanism of a Y-modified Cr-Al Coating Co-deposited on DZ125 Alloy and Its High-temperature Oxidation Resistance

Y-modified Cr-Al coatings were co-deposited on DZ125 alloy by a pack cementation process, and the microstructures, constituent phases, and formation mechanisms of the obtained coatings were studied. The oxidation resistance of the coatings was also investigated. The experimental results show that the coating prepared by co-depositing Cr-Al-Y at 1 050 degrees C for 2 h has a multi-layered structure with an outer layer composed of Cr and Ni3Cr2, a middle layer composed of Ni3Cr2 and Al13Co4, and an inner layer composed of Ni3Al. The co-deposited Y is mainly present in the outer and middle layers of the coating. The coating formation process follows a sequential deposition mechanism in which Al is deposited during the initial stage, followed by Cr deposition. After oxidation at 1 100 degrees C for 1 00 h, a dense Cr2O3 center dot Al2O3 scale forms on the obtained coating, which effectively protects the DZ125 alloy from oxidation by preventing the inward diffusion of oxygen.