Hafnon and zircon environmental barrier coatings for silicon-based components
A method for coating a substrate includes spraying a combination of powders. The combination of powders includes: Hf 0.5 Si 0.5 O 2 ; Zr 0.5 Si 0.5 O 2 ; and, optionally, at least one of HfO 2 and ZrO 2 . A molar ratio of said Hf 0.5 Si 0.5 O 2 and HfO 2 combined to said Zr 0.5 Si 0.5 O 2 and ZrO 2 combined is from 2:1 to 4:1. A molar ratio of said Hf 0.5 Si 0.5 O 2 to said HfO 2 is at least 1:3.
1. A method for coating a substrate, the method comprising:
spraying a combination of powders onto the substrate,
wherein the combination of powders comprises:
Hf 0.5 Si 0.5 O 2 ;
Zr 0.5 Si 0.5 O 2 ; and
HfO 2 and, optionally, ZrO 2 ,
wherein:
a molar ratio of said Hf 0.5 Si 0.5 O 2 and HfO 2 combined to said Zr 0.5 Si 0.5 O 2 and ZrO 2 combined is from 2:1 to 4:1; and
a molar ratio of said Hf 0.5 Si 0.5 O 2 to said HfO 2 is at least 1:3.
2. The method of claim 1 wherein:
said molar ratio of said Hf 0.5 Si 0.5 O 2 and HfO 2 combined to said Zr 0.5 Si 0.5 O 2 and ZrO 2 combined is from 7:3 to 3:1.
3. The method of claim 1 wherein:
the combination of powders comprises said HfO 2 at a single cation molarity of 0.10 to 0.45.
4. The method of claim 3 wherein:
the combination of powders further comprises said ZrO 2 at a single cation molarity of 0.050 to 0.150.
5. The method of claim 4 wherein:
a molar ratio of said HfO 2 to said ZrO 2 is at least 2:1.
6. The method of claim 5 wherein:
said molar ratio of said HfO 2 to said ZrO 2 is from 2:1 to 5:1.
7. The method of claim 5 wherein:
said molar ratio of said HfO 2 to said ZrO 2 is higher than a molar ratio of said Hf 0.5 Si 0.5 O 2 to said Zr 0.5 Si 0.5 O 2 .
8. The method of claim 1 wherein:
the combination of powders comprises in single cation mol percent at least 95.0% combined said Hf 0.5 Si 0.5 O 2 , said Zr 0.5 Si 0.5 O 2 , said HfO 2 , and said ZrO 2 , if any.
9. The method of claim 1 wherein:
the combination of powders further comprises CaO, AlO 1.5 , and SiO 2 .
10. The method of claim 1 wherein the spraying is of a layer and the method further comprises at least one of:
applying a bond coat onto the substrate before the spraying; and
applying a further layer atop the layer after the spraying.
11. The method of claim 10 including applying the further layer wherein:
the further layer is an abradable layer applied by air plasma spray.
12. The method of claim 11 including applying the further layer wherein:
the further layer has greater porosity than said layer formed by said spraying said combination of powders.
13. The method of claim 10 wherein:
the bond coat is SiOC-BMAS (Barium magnesium alumino silicate).
14. The method of claim 10 wherein:
the applying of the bond coat is slurry application of SiOC-BMAS.
15. The method of claim 14 wherein:
the applying of the further layer is air plasma spray comprising Hf 0.5 SiO 0.5 O 2 and Zr 0.5 Si 0.5 O 2 .
16. The method of claim 10 wherein:
the applying of the further layer is air plasma spray comprising Hf 0.5 SiO 0.5 O 2 , Zr 0.5 Si 0.5 O 2 , and HfO 2 .
17. The method of claim 16 wherein:
the air plasma spray of the further layer further comprises a polymer fugitive powder, the polymer fugitive powder providing the further layer with a porosity difference over said layer formed by said spraying said combination of powders of 4.0% to 25%.
18. The method of claim 1 wherein:
a molar ratio of said HfO 2 to said ZrO 2 is from 2:1 to 5:1.
19. The method of claim 1 wherein:
the substrate is silicon-based.
20. The method of claim 1 wherein:
the substrate is a CMC (ceramic matrix composite).