Y₂SiO₅environmental barrier coatings for niobium silicide based materials

Lifetime of environmental/thermal barrier coatings deposited on a niobium silicide composite with boron containing M7Si6‐based bond coat

“…The yttrium silicate layer revealed micro‐porosity. These fine pores, which were not observed in the Y 2 SiO 5 coating after deposition and vacuum annealing, were probably associated with phase transformations during the high temperature exposure . EDS analysis of the thermally cycled sample indicated diffusion of titanium from the substrate/bond coat area into the yttrium silicate layer: a titanium concentration of approximately 1.0 at% was determined in the Y 2 SiO 5 layer after 1000 cycles at 1100 °C.…”

“…However, to be used as a component in a double‐layer E/TBC system, the long‐term stability of magnetron sputtered yttrium silicate layers has to be studied in more detail. Porosity observed in the Y 2 SiO 5 coating might be associated with a decomposition process . Furthermore, Gd and Zr were detected in the yttrium silicate layer, indicating a reaction with the GZO topcoat.…”

“…). When exposed to rapidly flowing water vapour, the magnetron sputtered yttrium silicate layer provided protection to MASC samples with boron containing bond coat at 1100 and 1200 °C, reducing the oxide growth rate and exhibiting a better behaviour than mullite tested under the same conditions . Therefore, the combination of GZO and Y 2 SiO 5 appears a promising E/TBC to be applied in the combustion environment of turbine engines.…”

“…Thereafter, the samples were annealed in vacuum at 1100 °C for 3 h to transform the amorphous as‐sputtered layer into a crystalline coating with Y 2 SiO 5 being the predominant phase. More detailed information on the manufacturing process can be found elsewhere . The annealed samples were subsequently coated with an additional ∼150 μm thick EB‐PVD GZO topcoat on one side.…”

“…These EBCs were produced by atmospheric plasma spraying , low‐pressure plasma spraying and dip‐coating followed by sintering . Recently, 15–20 μm thick Y 2 SiO 5 manufactured by magnetron sputtering were deposited on ceramic matrix composites as well as on Nb/Nb 5 Si 3 ‐based composite for environmental protection .…”