Crystallization behavior of air-plasma-sprayed ytterbium-silicate-based environmental barrier coatings

Stresses in Ytterbium Silicate Multilayer Environmental Barrier Coatings

The internal stresses of plasma-sprayed multilayer ytterbium disilicate environmental barrier coatings were measured using microfocused high-energy X-rays in a transmission geometry. Stresses were measured for as-sprayed and ex-situ heat-treated ytterbium disilicate topcoats at room temperature and during in-situ heating and cooling experiments. In-situ loading experiments were also performed o...

Failure analysis of suspension plasma sprayed thermal barrier coatings

Structure, composition, and defect control during plasma spray deposition of ytterbium silicate coatings

Environmental barrier coatings (EBCs) are needed to protect SiC structures exposed to high temperatures in water vapor-rich environments. Recent studies of a tri-layer EBC system consisting of a silicon layer attached to the SiC, a mullite diffusion barrier and a lowsteam volatility ytterbium silicate topcoat have shown some promise for use at temperatures up to 1316 C. However, the performance...

Plasma spray deposition of tri-layer environmental barrier coatings

n air plasma spray process has been used to deposit tri-layer environmental barrier coatings consisting of a silicon bond coat, a mullite interiffusion barrier, and a Yb2SiO5 top coat on SiC substrates. Solidified droplets in as-deposited Yb2SiO5 and mullite layers were discovered to be epleted in silicon. This led to the formation of an Yb2SiO5 + Yb2O3 two-phase top coat and 2:1 mullite (2Al2O...

Monitoring Delamination of Plasma-Sprayed Thermal Barrier Coatings by Reflectance-Enhanced Luminescence

Highly scattering plasma-sprayed thermal barrier coatings (TBCs) present a challenge for optical diagnostic methods to monitor TBC delamination because scattering attenuates light transmitted through the TBC and usually degrades contrast between attached and delaminated regions of the TBC. This paper presents a new approach where reflectance-enhanced luminescence from a luminescent sublayer inc...