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 °C for 2 h has a multi-layered structure with an outer layer composed of Cr and Ni 3 Cr 2 , a middle layer composed of Ni 3 Cr 2 and Al 13 Co 4 , and an inner layer composed of Ni 3 Al. 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 °C for 1 00 h, a dense Cr 2 O 3 ·Al 2 O 3 scale forms on the obtained coating, which effectively protects the DZ125 alloy from oxidation by preventing the inward diffusion of oxygen.