Coating system for silicon based substrates

1. An article comprising:

a silicon based substrate;

an oxygen gettering layer;

a layer between the silicon based substrate and the oxygen gettering layer, wherein the layer has an elastic modulus of between 30 and 130 GPa and is selected from the group consisting of alkaline earth alumino silicates, yttrium monosilicate, yttrium disilicate, rare earth mono and disilicates, hafnium silicate, zirconium silicate; oxides of hafnium, zirconium, yttrium, rare earth metals, niobium, titanium, tantalum, silicon, aluminum; silicon nitride; silicon carbide; silicon oxynitrides; silicon oxy carbides; silicon oxycarbonitrides; silicon refractory metal oxides; alumina forming refractory metal alloys; chromia forming refractory metal alloys; and mixtures thereof; and

an environmental barrier coating (EBC) on the oxygen gettering layer.

2. An article according to claim 1 , wherein the oxygen gettering layer is selected from the group consisting of silicon metal, silicon metal alloys, intermetallic silicides, chromia forming metallic alloys, alumina forming metallic alloys, and mixtures thereof.

3. An article according to claim 1 or 2 , wherein the layer has a porosity of about 2 to 50%.

4. An article according to claim 1 or 2 , wherein the layer has a thickness of between 20 and 250 microns.

5. An article according to claim 1 or 2 , wherein the layer and the oxygen gettering layer have a ratio of thickness of complaint layer to gettering layer of about 0.1:1 and 10:1.

6. An article according to claim 5 , wherein the layer has a thickness of between 40 and 125 microns.

7. An article according to claim 6 , wherein the layer has a porosity of about 5 to 25%.

8. An article according to claim 1 , wherein the layer is selected from the group consisting of yttrium oxide, hafnium oxide, rare earth metal oxides, yttrium monosilicate, yttrium disilicate, rare earth mono and disilicates, hafnium silicate, and mixtures thereof.

9. An article according to claim 1 or 2 , wherein the silicon based substrate is selected from the group consisting of monolithic silicon nitride, monolithic silicon carbide, silicon nitride containing composites, silicon carbide containing composites, silicon oxynitrides, silicon carbonitrides, silicon oxycarbides, molybdenum alloys containing silicon, and niobium alloys containing silicon.

10. An article according to claim 1 or 2 , wherein the EBC comprises at least one layer selected from the group consisting of mullite, alkaline earth aluminosilicates, barium strontium aluminosilicate, yttrium silicates, rare earth silicates, hafnium oxide, zirconium oxide, titanium oxide, silicon oxide, yttrium oxide, rare earth metal oxides, tantalum oxide, niobium oxide, aluminum oxide, and mixtures thereof.

11. An article according to claim 10 , wherein the EBC comprises a plurality of layers.

12. The article according to claim 1 or 2 , wherein the layer and oxygen gettering layer are repeated at least once.

13. The article according to claim 1 or 2 , wherein the EBC coating is on substantially all of the oxygen gettering layer.

14. The article according to claim 1 or 2 , wherein the coated silicon based substrate, with the oxygen gettering layer and the layer therebetween that retains at least 70% of its original substrate strength.

15. A method of making the article according to claim 1 or 2 , wherein at least one of the layer, oxygen gettering layer and the EBC is deposited using thermal spraying, chemical vapor deposition, physical vapor deposition, electrophoretic deposition, electrostatic deposition, preceramic polymer pyrolysis, sol-gel, slurry coating, dipping, air-brushing, sputtering, slurry painting or any combination thereof.

16. A method of making the article according to claim 1 , wherein at least one sacrificial pore former is used to control the porosity and thereby modulus of the layer.