Abstract
Yb2Si2O7/Si environmental barrier coatings (EBCs) were produced by air plasma spray (APS) and low-pressure plasma spray (LPPS) processes. The phase composition, microstructure, and bonding strength of APS and LPPS EBCs were investigated. Thermal cycling tests were performed in air and in steam atmosphere respectively at 1316 °C for both APS and LPPS EBCs. There is no coating failure in air atmosphere for both APS and LPPS EBCs after 900 cycles. In contrast, APS EBCs have an average life of 576 cycles in a steam cycling test in 90% H2O + 10% air at 1316 °C while LPPS EBCs survived 1000 cycles without failure. The superior durability of the LPPS EBCs compared to APS EBCs in the same steam cycling environment is attributed to the significantly reduced thermally grown oxide (TGO) growth rate because of the denser and crack-free microstructure, higher bonding strength, and reduced coefficient of thermal expansion (CTE) mismatch (less Yb2SiO5 phase) in the LPPS Yb2Si2O7/Si EBCs.
Highlights
There is always a continuous demand for higher operating temperatures for gas turbine engines in order to improve fuel efficiency and engine thrust
Thermal cycling behaviors were tested in air and in steam atmosphere at 1316 ◦C for both air plasma spray (APS) and low-pressure plasma spray (LPPS) environmental barrier coatings (EBCs)
APS EBCs have an average life of 576 cycles in a steam cycling test in 90% H2O + 10% air at 1316 ◦C while LPPS EBCs survived 1000 cycles without failure
Summary
There is always a continuous demand for higher operating temperatures for gas turbine engines in order to improve fuel efficiency and engine thrust. For LPPS EBCs, a thin and dense SiO2 TGO layer is observed for all samples at various numbers of cycles (Figure 9).
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