Recession resistant ceramic matrix composites and environmental barrier coatings
The disclosure relates generally to recession resistant gas turbine engine articles that comprise a silicon containing substrate, and related coatings and methods. The present disclosure is directed, inter alia, to an engine article comprising a silicon substrate which is coated with a chemically stable porous oxide layer. The present disclosure also relates to articles comprising a substrate and a bond coat on top comprising a two phase layer of interconnected silicon and interconnected oxide, followed by a layer of silicon. The present disclosure further relates to a recession resistant article comprising an oxide in a silicon containing substrate, such that components of the silicon containing substrate is interconnected with oxides dispersed in the substrate and form the bulk of the recession resistant silicon containing article.
1. A recession resistant gas turbine component, comprising:
a SiC—SiC ceramic matrix composite substrate;
an intermediate layer disposed on and in contact with the substrate, the intermediate layer comprising a patterned array of a rare earth oxide, spaces in the patterned array being filled by a first silicon-containing compound or a first two-phase mixture of the rare earth oxide and the first silicon-containing compound; and
a porous layer disposed on and in contact with the intermediate layer, the porous layer comprising a second two-phase mixture of a second silicon-containing compound and an oxide comprising one or more rare earth silicates and alkaline earth aluminosilicates.
2. The article of claim 1 , wherein the porosity of the porous layer is about 5% to about 50%.
3. The article of claim 2 , wherein the porosity of the porous layer is graded.
4. The article of claim 3 , wherein the graded porous layer has an inner layer and an outer layer, the inner layer is chemically stable with silicon oxide and the outer layer has a higher stability in a water vapor environment than the inner layer.
5. The article of claim 4 , wherein the inner layer is a Rare Earth Disilicate (RE 2 Si 2 O 7 ) and the outer layer is a Rare Earth Monosilicate (RE 2 SiO 5 ), wherein RE is an element chosen from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or a combination thereof.
6. The article of claim 2 , wherein the porous layer has a coefficient of thermal expansion of about 5 ppm per degree C.
7. The article of claim 1 , wherein the porous layer comprises hafnium oxide and/or barium strontium aluminosilicate.
8. The article of claim 1 , wherein the porous layer is from about 1 mil to about 50 mils thick.
9. The article of claim 1 , wherein the article is a combustor article, a turbine blade, a shroud segment, a nozzle, a heat shield, or a vane.
10. The article of claim 1 , wherein the first two phase mixture is a mixture of silicon or silicon carbide and a Rare Earth Disilicate.
11. The article of claim 1 , wherein the first two phase mixture is a mixture of silicon nitride and a Rare Earth Monosilicate.
12. The article of claim 1 , wherein the patterned array is in the form of a vertical array, a lattice array, or a parallel array, wherein
in the vertical array, the rare earth oxide and the silicon-containing compound or the first two phase mixture are vertical arrays roughly normal to the surface of the substrate,
in the lattice arrays, the rare earth oxide and the silicon-containing compound or the first two phase mixture are in the form of a lattice or grid relative to the surface of the substrate,
in the parallel arrays, the rare earth oxide and the silicon-containing compound or the first two phase mixture are parallel to each other relative to the surface of the substrate.
13. The article of claim 1 , further comprising:
an environmental barrier coating disposed on and in contact with the porous layer, wherein the environmental barrier coating is from about 2 mils to about 50 mils thick.
14. The article of claim 1 , wherein the porous layer has a tortuosity of between 2 to 4.
15. The article of claim 1 , wherein the second two phase mixture is 5% to 50% by volume of the second silicon-containing compound and 50% to 95% of the oxide comprising one or more rare earth silicates and alkaline earth aluminosilicates.
16. The article of claim 1 , wherein the oxide comprising one or more rare earth silicates and alkaline earth aluminosilicates comprises interconnected oxides.