Interplay of the phase and the chemical composition of the powder feedstock on the properties of porous 8YSZ thermal barrier coatings

• Published in: Journal of the European Ceramic Society Vol. 41; no. 6; pp. 3706 - 3716
• Main Authors: Sharma, Atin, Witz, Gregoire, Howell, Philip C., Hitchman, Neil
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2021
• Subjects: Chemical composition; Phase transformation; Powder feedstock; Thermal barrier coatings; Yttria stabilized zirconia ceramic; Thermal barrier coatings; Phase transformation; Chemical composition; Powder feedstock; Yttria stabilized zirconia ceramic
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2020.10.062

•No clear correlation observed between the chemical / phase composition of the 8YSZ powder feedstock, and the resulting coating properties.•Powder chemical composition has a stronger influence on coating sintering kinetics than that of powder phase purity.•TBC microstructure plays the most dominant role in defining coating properties and performance regardless of the feedstock characteristics. Some chemical impurities enhance sintering kinetics of ceramic Thermal Barrier Coatings (TBCs) which can cause their premature failure during operation in gas turbine engine by causing reduction in coating’s strain compliance as well as faster bond-coat oxidation due to increased thermal conductivity. Certain chemical impurities are also believed to suppress resistance to tetragonal to monoclinic phase transformation in 8YSZ, which can also be an important factor regarding TBC’s performance. Most of the impurities and some of the monoclinic phase present in the powder feedstocks can survive into the as-sprayed coating. Therefore, there is a general trend towards OEMs requiring the lowest amounts of chemical impurities and the lowest amounts of monoclinic phase in the powder feedstocks. This paper presents a comprehensive investigation aimed at understanding the role and the relative importance of the chemical and phase purities of the powder feedstock for the properties and performance of thick 8YSZ TBCs.