Fatigue of a SiC/SiC ceramic composite with an ytterbium‐disilicate environmental barrier coating at elevated temperature*

Abstract

Tension‐tension fatigue performance of a SiC/SiC composite with an ytterbium‐disilicate environmental barrier coating (EBC) was investigated at 1200°C in air and steam. The composite is reinforced with Hi‐Nicalon™ SiC fibers and has a melt‐infiltrated matrix processed by chemical vapor infiltration of SiC with subsequent infiltration with SiC particulate slurry and molten silicon. The EBC consists of a Si bond coat and an Yb2Si2O7 top coat applied via air plasma spraying. Tensile properties were evaluated at 1200°C. Tension‐tension fatigue was examined for maximum stresses of 110‐140 MPa. To assess the efficacy of EBC, experimental results obtained for the coated composite are compared to those for a control uncoated composite. Surface grit‐blasting inherent in the EBC application process degrades tensile strength of the composite. However, the EBC effectively protects the composite from oxidation embrittlement during cyclic loading in air or steam. Fatigue runout set to 200 000 cycles (55.6 hours at a frequency of 1.0 Hz) was achieved at 110 MPa in air and steam. Retained properties of pre‐fatigued specimens were characterized. Composite microstructure, along with damage and failure mechanisms were investigated. Damage and failure of the composite are attributed to the growth of cracks originating from numerous processing defects in the composite interior.

To drill or not to drill? Creep of an oxide‐oxide composite with diamond‐drilled effusion holes at elevated temperature

“…The largest deviation from the nominal test temperature was ±1°C in air and ±2°C in steam. A detailed description of the experimental set‐up is given elsewhere 34,41–43 . All tests were conducted at 1200°C.…”

“…A detailed description of the experimental set-up is given elsewhere. 34,[41][42][43] All tests were conducted at 1200 • C. In all tests, a specimen was heated to test temperature at 1 • C/s and held at that temperature for additional 45 min prior to testing.…”

The Effect of High-Temperature Water Vapour on Degradation and Failure of Hot Section Components of Gas Turbine Engines

“…Ruggles-Wrenn et al [69] studied the fatigue behaviour of the ytterbium disilicate environmental barrier coating on a SiC/SiC ceramic composite at elevated temperatures. The tension-tension fatigue property of the EBC-containing composite was examined in both air and steam at 1200 • C. It was observed that in the air, the EBC system shows a lower fatigue limit and a shorter cyclic life than the uncoated CMC.…”

High-Temperature Solid Particle Erosion of Environmental and Thermal Barrier Coatings

“…In addition to water-vapor-induced oxidation and recession, EBCs need to be resilient against thermal and thermo-mechanical stress/strain [11][12][13][14][15][16], calcium-magnesiumaluminosilicate (CMAS) deposits [17][18][19][20][21][22], foreign object damage (FOD) [23,24], and solid particle erosion (SPE) [25][26][27]. While many of the aforementioned degradation modes have been investigated, there is still a gap in the characterization and fundamental understanding of the SPE behavior of EBCs.…”