Thermal cycling performances of multilayered yttria‐stabilized zirconia/gadolinium zirconate thermal barrier coatings

Abstract

Gadolinium zirconate (Gd2Zr2O7, GZO) as an advanced thermal barrier coating (TBC) material, has lower thermal conductivity, better phase stability, sintering resistance, and calcium‐magnesium‐alumino‐silicates (CMAS) attack resistance than yttria‐stabilized zirconia (YSZ, 6‐8 wt%) at temperatures above 1200°C. However, the drawbacks of GZO, such as the low fracture toughness and the formation of deleterious interphases with thermally grown alumina have to be considered for the application as TBC. Using atmospheric plasma spraying (APS) and suspension plasma spraying (SPS), double‐layered YSZ/GZO TBCs, and triple‐layered YSZ/GZO TBCs were manufactured. In thermal cycling tests, both multilayered TBCs showed a significant longer lifetime than conventional single‐layered APS YSZ TBCs. The failure mechanism of TBCs in thermal cycling test was investigated. In addition, the CMAS attack resistance of both TBCs was also investigated in a modified burner rig facility. The triple‐layered TBCs had an extremely long lifetime under CMAS attack. The failure mechanism of TBCs under CMAS attack and the CMAS infiltration mechanism were investigated and discussed.

Review of the coatings used for brake discs regarding their wear resistance and environmental effect

“…75 SPS is a cost-effective coating method and flexible in terms of coating microstructure. 78 High velocity oxygen fuel (HVOF) spraying is a technique in which flame (combustion) energy is used for melting of the coating material, and high combustion chamber pressure and a converging-diverging expansion nozzle is used to accelerate melted particles with high velocities toward the substrate. 45,79 Coatings applied by the HVOF method have higher hardness and density compared to other coating methods.…”

Coatings with Columnar Microstructures for Thermal Barrier Applications

“…In addition to their excellent burner rig performance, optimized multilayered systems also show an improved resistance against calcium, magnesium, aluminum, and silicon oxide (CMAS) attack, which is a severe issue, especially for aeroengines (e.g., in the form of volcanic ash). [49]…”

“…In Figure , an SEM micrograph of a double layer coating after burner rig test is shown, indicating that failure occurs very late after rather complete β‐phase depletion of the bond coat. In addition to their excellent burner rig performance, optimized multilayered systems also show an improved resistance against calcium, magnesium, aluminum, and silicon oxide (CMAS) attack, which is a severe issue, especially for aeroengines (e.g., in the form of volcanic ash) …”

“…SEM micrograph of a GZO/YSZ double layer after test in burner rig with rather complete β‐phase depletion of the bond coat. Reproduced with permission . Copyright 2019, Wiley.…”

Laser thermal gradient testing of air plasma sprayed multilayered, multi‐material thermal barrier coatings

“…There have been some studies published recently that overview some of aspects of TBC performance in thermal gradients such as durability. [41][42][43][44][45] However, the subtleties such as microstructural changes of TBCs due to sintering in the presence of a cyclic gradient have not fully been realized through experimental methods and detailed characterization. Tan et al in 2010, through the use of a gradient sintering model and an embedded thermocouple within a TBC, utilized high-temperature cycling at the laser rig at NASA to study the effective change in thermal conductivity over prolonged exposure in a thermal gradient.…”