Protective overlayer for ceramics
View Patent ↗A xenotime phosphate protective overlayer ( 22 ) for protecting a ceramic material ( 24 ) from a high temperature, moisture-containing environment. Yttrium phosphate may be used as a protective overlayer to protect an underlying mullite layer to temperatures in excess of 1,500° C. The coating may have porosity of greater than 15% for improved thermal shock protection. To prevent the ingress of oxygen to an underlying ceramic non-oxide material, such as silicon carbide or silicon nitride, an oxygen barrier layer ( 34 ) is disposed between the xenotime phosphate coating and the non-oxide material. Such a protective overlayer may be used for an article having a ceramic matrix composite substrate.
1. An article adapted for use in a combustion environment, the article comprising:
a non-oxide ceramic substrate;
an oxygen barrier layer disposed on the non-oxide ceramic substrate; and
an overlayer of xenotime phosphate compound disposed on the oxygen barrier layer and defining a surface exposed to the combustion environment.
2. The article of claim 1 , wherein the xenotime phosphate compound comprises yttrium phosphate.
3. The article of claim 1 , further comprising:
the non-oxide ceramic substrate comprises one of the group of silicon carbide and silicon nitride; and
the oxygen barrier layer comprises one of the group of mullite, zircon, zirconium phosphate, and yttrium silicate.
4. The article of claim 1 , further comprising the overlayer of xenotime phosphate compound having a porosity of at least 10%.
5. The article of claim 1 , further comprising the overlayer of xenotime phosphate compound having a porosity of at least 15%.
6. The article of claim 1 , wherein the non-oxide ceramic substrate comprises silicon.
7. The article of claim 1 , further comprising the overlayer of xenotime phosphate compound having a thickness of greater than 0.1 mm.
8. An article adapted for use in a combustion environment, the article comprising:
a ceramic matrix composite substrate;
a layer of ceramic oxide insulating material comprising mullite disposed on the substrate; and
a layer of a xenotime phosphate compound disposed on the layer of insulating material and defining a surface exposed to the combustion environment.
9. The article of claim 8 , wherein the xenotime phosphate compound comprises yttrium phosphate.
10. The article of claim 8 , wherein the xenotime phosphate compound comprises yttrium phosphate and the layer of ceramic oxide insulating material comprises mullite.
11. The article of claim 10 , further comprising the layer of yttrium phosphate compound having a thickness of greater than 0.1 mm.
12. The article of claim 8 , further comprising the xenotime phosphate compound comprising a porosity of at least 10%.
13. The article of claim 8 , further comprising the xenotime phosphate compound comprising a porosity of at least 15%.
14. The article of claim 8 , wherein the ceramic oxide insulating material comprises silicon.