Abstract
Thermomechanical and thermochemical stability of hafnon (HfSiO4) was evaluated for application as an environmental barrier coating (EBC) candidate for SiC/SiC CMCs. High-temperature X-ray diffraction (XRD) analysis showed that hafnon has an excellent coefficient of thermal expansion (CTE) match with SiC as well as minimal CTE anisotropy, which supports hafnon as an EBC candidate. Alternatively, high-velocity water vapor testing at 1,200-1,400°C showed large amounts of silica depletion from chemical reaction at all velocities and excessive material erosion at steam velocities greater than 190 m/s. HfSiO4 is therefore not suitable as an EBC for turbine applications due to insufficient thermochemical stability in water vapor-containing combustion environments.
| Original language | English |
|---|---|
| Pages (from-to) | 3593-3602 |
| Number of pages | 10 |
| Journal | Journal of the American Ceramic Society |
| Volume | 104 |
| Issue number | 7 |
| DOIs | |
| State | Published - Jul 2021 |
| Externally published | Yes |
Funding
This research was supported by the Office of Naval Research, Award N000141712280, program manager Dr. David Shifler. The authors would like to acknowledge Dr. Bryan Harder (NASA, Glenn Research Center) for supplying the HfSiO4 powder and the Nanoscale Materials Characterization Facility at the University of Virginia for supporting the characterization equipment.
Keywords
- environmental barrier coatings
- hafnium silicate
- silicates
- thermal expansion
- volatilization