Oxidation Behavior of Aluminide Coatings on Cobalt-Based Superalloys by a Vapor Phase Aluminizing Process

• Published in: Materials 2024-12, Vol.17 (23), p.5897
• Main Authors: Ma, Kuo, Xie, Cheng, Li, Yidi, Yang, Biaobiao, Jin, Yuanyuan, Wang, Hui, Zeng, Ziming, Li, Yunping, Ye, Xianjue
• Format: Article
• Language: English
• Subjects: Alloys; Aluminides; Aluminizing; Aluminum oxide; Chemical vapor deposition; Coal; Coatings; Cobalt; Cobalt base alloys; Diffusion coating; Diffusion layers; Diffusion rate; Experiments; Gas turbine engines; Heat resistant alloys; Nickel base alloys; Oxidation; Oxidation rate; Oxidation-reduction reaction; Rate constants; Spectrum analysis; Superalloys; Temperature; Vapor phases
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma17235897

In this work, the oxidation behavior of an aluminide coating at 900, 1000, and 1100 °C was investigated. The aluminide coating was prepared on a cobalt-based superalloy using a vapor phase aluminizing process, which is composed of a β-(Co,Ni)Al phase outer layer and a Cr-rich phase diffusion layer. The experimental results showed that the oxidation of the coating at 900-1100 °C all obey the parabolic law. The oxidation rate constants of the coating were between 2.19 × 10 and 47.56 × 10 mg ·cm ·s . The coating produced metastable θ-Al O at 900 °C and stable α-Al O at 1000 and 1100 °C. As the oxidation temperature increases, the formation of Al O is promoted, consuming large amount of Al in the coating, resulting in the transformation from β-(Co,Ni)Al phase to α-(Co,Ni,Cr) phase. And the decrease in the β phase in the coating led to the dissolution of the diffusion layer.