A TEM Study of the Microstructure of Plasma-Sprayed YSZ Near Inter-splat Interfaces

Abstract

The splat interface bonding state which changes heat transfer conditions and thus the cooling rate during splat cooling may influence the interface microstructure. In this paper, YSZ coating was deposited by atmospheric plasma spraying with substrate cooling during deposition. Subsequent characterization was implemented using high resolution transmission electron microscopy to examine the local microstructures near the interfaces at the bonded and unbonded zones. Selected area diffraction analyses of the splats across both the bonded interface and unbonded interface revealed that all bulk splats present a metastable tetragonal structure. Results showed that the size of columnar grains within a splat was significantly influenced by the interface bonding. At the unbonded region in the splat, large columnar grains form which can be attributed to poor thermal contact of melt to the underlying splat surface before its solidification. At the bonded zones, the splat presents a much fine columnar grain structure, which is attributed to good thermal contact of the melt to the underlying splat before solidification. Moreover, it is evident that the bonded interface region presents a distinct microstructure feature from the fine columnar grains suggesting the crystal defect of high density of dislocations at the interface.

Hot corrosion behaviors of as-sprayed and laser-remelted YSZ thermal barrier coatings at 950 °C

“…The porosity of as-sprayed TBC is mostly 12.42%. The top ceramic layer has a lamellar structure, which attributes to the accumulating flattened splats during the plasma spray treatment [19]. Sobhanverdi et al reported that the sprayed process has effect on the porosity of the TBCs.…”

Microstructural characterization of plasma sprayed Ln2Zr2O7 thermal barrier coatings by electron microscopy methods

“…Literature data related to those types of investigations is relatively poor in comparison to conventional analysis with LM/SEM/XRD methods (Chmiela, Sozańska, & Moskal, ; Fujiyama, Nakaseko, Kato, & Kimachi, ; Schulz & Braue, ; Zheng, Luo, & Li, ) and (Burns, Subramanian, Kempshall, & Sohn, ; Chen, Gao, Tao, Liua, & Luo, ; Drexler et al, ; Hu, Guo, Tomimatsu, Ikuhara, & Kagawa, ; Kempshalla et al, ; Levi, Sommer, Terry, Catanoiu, & Ruhle, ; Murphy, More, & Lance, ; Poza, Gomez‐Garcıa, & Munez, ; Swadźba et al, ; Xu, Yu, Moub, Zhang, & Tao, ; Yang, Luo, Yang, Li, & Li, ), respectively.…”