Slurry-based methods for forming a bond coat and articles formed by the methods
Methods for forming a sintered bond coat ( 64 ) on a silicon-based substrate ( 14 ) and articles ( 50 ) formed by the methods are disclosed. The methods include applying a bond coat slurry on the silicon-based substrate ( 14 ), drying the bond coat slurry on the silicon-based substrate to form a dried bond coat ( 44 ), and sintering the dried bond coat ( 44 ) in an oxidizing atmosphere to form a sintered bond coat ( 64 ) on the silicon-based substrate ( 14 ). The bond coat slurry includes a bond coat patching material in a bond coat fluid carrier. The articles ( 50 ) include a silicon-based substrate ( 14 ), a sintered bond coat ( 64 ) formed on the silicon-based substrate ( 14 ), and a sintered environmental barrier coating (EBC) ( 66 ) formed on the sintered bond coat ( 64 ). The sintered bond coat ( 64 ) includes a silicon-based phase and an oxide of the silicon-based phase.
1 . A method comprising:
applying a bond coat slurry on a silicon-based substrate, wherein the bond coat slurry comprises:
a bond coat patching material in a bond coat fluid carrier, wherein the bond coat patching material comprises a silicon-based powder,
a bond coat binder, and
a bond coat sintering aid, wherein the bond coat sintering aid is boron;
wherein the silicon-based powder comprises a plurality of small particles with a median particle size less than 1 micron, a plurality of medium particles with median particle size in a range from 1 micron to 6 microns, and a plurality of large particles with median particle size greater than 6 microns, and wherein the plurality of small particles is present in an amount in a range from about 60 volume % to about 80 volume %, the plurality of medium particles is present in an amount in a range from about 10 volume % to about 30 volume %, and the plurality of large particles is present in an amount in a range from about 10 volume % to about 30 volume % of the volume of the silicon-based powder;
drying the bond coat slurry on the silicon-based substrate to form a dried bond coat; and
sintering the silicon-based powder in the dried bond coat in an oxidizing atmosphere to form a sintered bond coat on the silicon-based substrate, wherein the sintered bond coat comprises a silicon-based phase and an oxide of the silicon-based phase, and the silicon-based phase comprises silicon, a silicon alloy, a metal silicide, or a combination thereof, wherein the oxide of the silicon-based phase in the sintered bond coat is present in an amount in a range of 25 volume % to 55 volume %.
2 . The method of claim 1 , wherein the silicon-based powder comprises silicon, a silicon alloy, a metal silicide or a combination thereof.
3 . The method of claim 1 , wherein the bond coat slurry comprises the bond coat patching material in an amount from about 25 volume % to about 70 volume % of the bond coat slurry.
4 . The method of claim 1 , wherein the bond coat patching material comprises the bond coat binder in an amount from about 2.5 weight % to about 8 weight % of the bond coat patching material.
5 . The method of claim 1 , wherein the bond coat patching material comprises the bond coat sintering aid in an amount from about 0.5 weight % to about 4.5 weight % of the bond coat patching material.
6 . The method of claim 1 , wherein the silicon-based substrate comprises a silicon carbide-based ceramic matrix composite.
7 . The method of claim 1 , wherein the sintering of the dried bond coat comprises heat-treating the dried bond coat at a temperature between about 1000° C. and about 1400° C.
8 . The method of claim 1 , wherein the oxidizing atmosphere comprises air or a combustion gas.
9 . The method of claim 1 , wherein the sintering of the dried bond coat is carried out during operation of a component comprising the silicon-based substrate.
10 . The method of claim 1 , further comprising:
applying an environmental barrier coating (EBC) slurry on the dried bond coat, wherein the EBC slurry comprises an EBC patching material in an EBC fluid carrier, wherein the EBC patching material comprises an EBC powder and an EBC binder;
drying the EBC slurry on the dried bond coat to form a dried EBC; and
sintering the dried bond coat and the dried EBC in the oxidizing atmosphere to form the sintered bond coat on the silicon-based substrate and a sintered EBC on the sintered bond coat.
11 . The method of claim 10 , wherein the EBC powder comprises at least one of a rare earth monosilicate or a rare earth disilicate.
12 . The method of claim 10 , wherein the EBC powder has a particle size that is less than 1 micron.
13 . The method of claim 10 , wherein the EBC patching material further comprises an EBC sintering aid having a particle size that is less than 100 nanometers.
14 . The method of claim 1 , wherein the bond coat binder comprises a silicon-based resin material.
15 . The method of claim 1 , wherein the bond coat sintering aid has a particle size that is less than 1 micron.
16 . The method of claim 1 , wherein the bond coat sintering aid has a particle size that is less than 100 nanometers.
17 . A method comprising:
applying a bond coat slurry on a silicon-based substrate, wherein the bond coat slurry comprises:
a bond coat patching material in a bond coat fluid carrier, wherein the bond coat patching material comprises a silicon-based powder,
a bond coat binder, and
a bond coat sintering aid,
wherein the silicon-based powder comprises a plurality of small particles with a median particle size less than 100 nanometers, a plurality of medium particles with median particle size in a range from 1 micron to 6 microns, and a plurality of large particles with median particle size greater than 6 microns, wherein the plurality of small particles is present in an amount in a range from about 60 volume % to about 80 volume %, the plurality of medium particles is present in an amount in a range from about 10 volume % to about 30 volume %, and the plurality of large particles is present in an amount in a range from about 10 volume % to about 30 volume % of the volume of the silicon-based powder;
drying the bond coat slurry on the silicon-based substrate to form a dried bond coat; and
sintering the silicon-based powder in the dried bond coat in an oxidizing atmosphere to form a sintered bond coat on the silicon-based substrate, wherein the sintered bond coat comprises a silicon-based phase and an oxide of the silicon-based phase, and the silicon-based phase comprises silicon, a silicon alloy, a metal silicide, or a combination thereof, wherein the oxide of the silicon-based phase in the sintered bond coat is present in an amount in a range of 25 volume % to 55 volume %.