Microstructural evolution and diffusion mechanism of MCrAlY coated nickel-based superalloy turbine blades after serviced for 47,000 h

• Published in: Surface & coatings technology 2024-10, Vol.493, p.131288, Article 131288
• Main Authors: Chen, Yang, Yao, Zhihao, Wang, Jingjing, Dong, Jianxin, Ren, Mo, Peng, Jialin, Yang, Huanyu, Leng, Liuxi
• Format: Article
• Language: English
• Subjects: Element diffusion; In-service turbine blades; Microstructural evolution; Ni-based superalloy; Oxidation
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2024.131288

The large-sized industrial gas turbine blades exhibit non-uniform microstructural degradation in various parts due to ultra-long term service in high-temperature and high-pressure environments. Determination of degradation behavior at critical locations is important for the safety of gas turbine and blades refurbishment program. The microstructure characterization on the surface and interface of MCrAlY coated Ni-based superalloy blades have been studied. The microstructure evolution near the coating/ substrate interface was studied by scanning electron microscope (SEM) and the difference in degradation of the main precipitates at several locations were quantified. Surface oxidation and interfacial diffusion were analyzed through energy dispersive spectrum (EDS) and electron probe microanalyzer (EPMA) to clarify the influence of elemental diffusion on microstructure. The results indicated that regional microstructure evolution influenced by the spatial structural characteristics of the blades. The migration of Ni, Al, Cr, and Co dominated the diffusion mechanism during service, and reconstructed the microstructure of the coating/substrate interface and surface. [Display omitted] •The oxidation behavior on surface and diffusion mechanism of the large-sized 3rd stage gas turbine blades after 47,000 operating hours were characterized by SEM equipped with EDS and EPMA.•The consumption of β in MCrAlY was positively correlated with the degree of γ' degradation after long term service, accompanied by the differential degradation and precipitation of γ'tertiary, σ-(CrxCoy), Cr23C6 occurred.•The oxidation gradient was observed on the cooling channel surface due to the migration of Ni, Al, Cr, and Co, also resulting in a gradient microstructural change of γ' precipitates.