Environmental barrier coatings for improved temperature capabilities and longevity
View Patent ↗Slurry EBC systems and method for fabricating slurry EBC systems for protecting component substrates and extending the longevity of such components are disclosed. The slurry EBC systems include a bond coat having a temperature capability of up to 1482° C. (2700° F.). Example bond coats include a mullite-based bond coat and a rare earth disilicate-based bond coat.
1. A method of fabricating a slurry environmental barrier coating system comprising:
fabricating a bond coat comprising:
preparing a mixture comprising:
a bond-coat coating material comprising 70 wt %-99 wt % mullite,
a primary sintering aid comprising 0.1 wt % to 30 wt % Si,
at least one secondary sintering aid selected from 0.1 wt % to 20 wt % RE 2 Si 2 O 7 , 0.1 wt % to 20 wt % Yb 2 Si 2 O 7 , 0.1 wt % to 20 wt % YAG (Y 3 Al 5 O 12 ), 0.1 wt % to 20 wt % YbAG (Yb 3 Al 5 O 12 ), 0.1 wt % to 20 wt % A l2 O 3 , and 0.1 wt % to 20 wt % TiO 2 , or any combination of two or more thereof, and
a first solvent;
milling the mixture in a milling media to form a first slurry;
filtering and drying the first slurry to form a powder of the bond-coat coating material, the primary sintering aid, and the at least one secondary sintering aid;
mixing the powder with a solution comprising a second solvent and an organic processing aid and milling the resulting mixture to form a second slurry; and
applying the second slurry to a substrate to form the bond coat layer.
2. The method of claim 1 , wherein the method further comprises:
fabricating a first top coat layer comprising:
preparing a mixture comprising:
a first-top-coat coating material comprising 80 wt %-99 wt % HfSiO 4 ,
a primary sintering aid comprising 1 wt % to 20 wt % Si, and
a first solvent;
milling the mixture in a milling media to form a third slurry;
filtering and drying the third slurry to form a powder of the first-top-coat coating material and the primary sintering aid;
mixing the milled powder with a solution comprising a second solvent and an organic processing aid and milling the resulting mixture to form a fourth slurry; and
applying the fourth slurry to the bond coat layer to form the first top coat layer; and fabricating a second top coat layer comprising:
preparing a mixture comprising:
a second-top-coat coating material comprising 70 wt %-99.9 wt % RE 2 Si 2 O 7 ,
a primary sintering aid comprising 0.1 wt % to 10 wt % mullite, and a solvent;
milling the mixture in a milling media to form a fifth slurry;
filtering and drying the fifth slurry to form a powder of the second-top-coat coating material and the primary sintering aid;
mixing the powder with a solution comprising a second solvent and an organic processing aid and milling the resulting mixture to form a sixth slurry; and
applying the sixth slurry to the first top coat layer to form the second top coat layer.
3. The method of claim 2 , wherein the method further comprises fabricating at least one outer top coat layer comprising an outer-top-coat coating material comprising RE 2 SiO 5 , RE 2 O 3 , or stabilized ZrO 2 and/or stabilized HfO 2 , wherein the at least one outer top coat layer is applied to the second top coat layer.
4. The method of claim 2 , wherein (1) the third slurry of the first top coat layer further comprises a secondary sintering aid selected from 0.1 wt % to 20 wt % mullite, 0.1 wt % to 20 wt % YAG (Y 3 Al 5 O 12 ), 0.1 wt % to 20 wt % YbAG (Yb 3 Al 5 O 12 ), 0.1 wt % to 20 wt % Yb 2 Si 2 O 7 , 0.1 wt % to 20 wt % Y 2 Si 2 O 7 , 0.1 wt % to 20 wt % Al 2 O 3 , and 0.1 wt % to 20 wt % TiO 2 , or any combination of two or more thereof and (2) the fifth slurry of the second top coat layer further comprises 0.1 wt % to 20 wt % YAG (Y 3 Al 5 O 12 ), 0.1 wt % to 20 wt % YbAG (Yb 3 Al 5 O 12 ), 0.1 wt % to 20 wt % Al 2 O 3 , and 0.1 wt % to 20 wt % TiO 2 , or any combination of two or more thereof.
5. The method of claim 2 , wherein the second solvent for any layer is an alcohol selected from ethanol, methanol, ethyl alcohol, or a combination thereof.
6. The method of either claim 1 or 2 , wherein the organic processing aid comprises:
a dispersant selected from polyethyleneimine (PEI), polyacrylic acid (PAA), ammonium polyacrylate, or a combination thereof and a binder selected from polyvinylbutyral (PVB) and polyvinylpyrollidone (PVP).
7. The method of claim 2 , wherein application of any of the layers is done by dipping, spinning, spin-dipping, painting, or spraying.
8. The method of claim 2 , wherein each of the bond coat layer, the first top coat layer, and the second top coat layer are further processed by drying, binder burn-out, and sintering.
9. The method of claim 8 , wherein the further processing is done after each layer is applied.
10. The method of claim 1 , wherein the at least one secondary sintering aid is 0.1 wt % to 20 wt % Yb 2 Si 2 O 7 .
11. A method of fabricating a slurry environmental barrier coating system comprising:
fabricating a bond coat comprising:
preparing a mixture comprising:
a bond-coat coating material comprising 70 wt %-99 wt % RE 2 Si 2 O 7 , a primary sintering aid comprising 1 wt % to 30 wt % Si,
at least one secondary sintering aid selected from 0.1 to 20 wt % mullite, 0.1 wt % to 20 wt % YAG (Y 3 Al 5 O 12 ), 0.1 wt % to 20 wt % YbAG (Yb 3 Al 5 O 12 ), 0.1 wt % to 20 wt % Al 2 O 3 , and 0.1 wt % to 20 wt % TiO 2 , or any combination of two or more thereof, and
a first solvent;
milling the mixture in a milling media to form a first slurry;
filtering and drying the first slurry to form a powder of the bond-coat coating material and the primary sintering aid;
mixing the powder with a solution comprising a second solvent and an organic processing aid and milling the resulting mixture to form a second slurry; and
applying the second slurry to a substrate to form the bond coat layer.
12. The method of claim 11 , wherein the method further comprises:
fabricating a top coat layer comprising:
preparing a mixture comprising:
a top-coat coating material comprising 70 wt %-99.9 wt % RE 2 Si 2 O 7 ,
a primary sintering aid comprising 0.1 wt % to 10 wt % mullite, and
a first solvent;
milling the mixture in a milling media to form a third slurry;
filtering and drying the third slurry to form a powder of the top-coat coating material and the primary sintering aid;
mixing the milled powder with a solution comprising a second solvent and an organic processing aid and milling the resulting mixture to form a fourth slurry; and
applying the fourth slurry to the bond coat layer to form the top coat layer.
13. The method of claim 12 , wherein the method further comprises fabricating at least one outer top coat layer comprising an outer-top-coat coating material comprising RE 2 SiO 5 , RE 2 O 3 , or stabilized ZrO 2 and/or stabilized HfO 2 , wherein the at least one outer top coat layer is applied to the top coat layer.
14. The method of claim 12 , wherein the third slurry of the top coat layer further comprises 0.1 wt % to 20 wt % YAG (Y 3 Al 5 O 12 ), 0.1 wt % to 20 wt % YbAG (Yb 3 Al 5 O 12 ), 0.1 wt % to 20 wt % Al 2 O 3 , and 0.1 wt % to 20 wt % TiO 2 , or any combination of two or more thereof.
15. The method of either claim 11 or 12 , wherein the organic processing aid for any layer comprises:
a dispersant selected from polyethyleneimine (PEI), polyacrylic acid (PAA), ammonium polyacrylate, or a combination thereof and a binder selected from polyvinylbutyral (PVB) and polyvinylpyrollidone (PVP).
16. The method of claim 12 , wherein application of any of the layers is done by dipping, spinning, spin-dipping, painting, or spraying.
17. The method of claim 12 wherein the bond coat layer and the top coat layer are further processed by drying, binder burn-out, and sintering.
18. The method of claim 12 , wherein the second solvent for any layer is an alcohol selected from ethanol, methanol, ethyl alcohol, or a combination thereof.