Relationship between the mechanical properties and structure of a suspension plasma-sprayed thermal barrier coating with columnar microstructure

• Published in: Surface & coatings technology 2022-06, Vol.439, p.128430, Article 128430
• Main Authors: Yamazaki, Yasuhiro, Morikawa, Masahiro, Hamaguchi, Tatsuya, Habu, Yoichiro, Ohide, Yuhei, Takagi, Kaito
• Format: Article
• Language: English
• Subjects: Bend tests; Cantilever members; Columnar microstructure; Columnar structure; Elastic anisotropy; Finite element method; Mechanical properties; Microstructure; Modulus of elasticity; Plasma spraying; Shear strength; Shear tests; Single column; Sintering (powder metallurgy); Spark plasma sintering; Suspension plasma spraying; Thermal aging; Thermal barrier coating; Thermal barrier coatings; Young's modulus
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2022.128430

To investigate the mechanical properties of a suspension plasma-sprayed (SPS) thermal barrier coating (TBC) with a unique cauliflower-like columnar structure, shear and cantilever bending tests were conducted on its single submillimeter-sized columns. In the shear test, the fracture of the single columns occurred at the porous layer near the top-coating/bond-coating interface. Compared with conventional atmospheric plasma-sprayed (APS) TBCs having a lamellar microstructure, the cantilever bending test revealed a significantly low Young's modulus along the out-of-plane direction and strong anisotropy in the elastic modulus of the SPS TBC. The shear strength and out-of-plane Young's modulus of the single columns increased due to the sintering resulting from thermal aging; however, the increasing ratio of the shear strength was higher than that of the Young's modulus. Both experimental and finite element analysis results indicated that the mechanical properties of the SPS TBC, as well as their variation with thermal aging, are dominated by those of the porous layer within the single column undergoing sintering. Moreover, the experimental results suggested that SPS TBCs having a cauliflower-like columnar microstructure have superior durability to thermal cycles compared with APS TBCs. •The out-of-plane Young's modulus and shear strength of the single columns of a suspension plasma sprayed thermal barrier coating (SPS TBC) were evaluated.•The influence of thermal aging on the mechanical properties were discussed.•The out-of-plane Young's modulus of the tested SPS TBC is significantly lower than that of conventional atmospheric plasma sprayed TBC.•The Young's modulus and shear strength of the tested SPS TBCs increase after thermal aging due to the sintering in their porous layers.•The superior thermal cycling resistance and sintering properties of the tested SPS TBC are related to its unique columnar microstructure, which consists of dense and porous layers.