WE CLAIM
1. An article, comprising:
a silicon-containing region;
at least one outer layer overlying a surface of the silicon-containing region; and
a constituent layer on the surface of the silicon-containing region and between and contacting the silicon-containing region and the at least one outer layer, the constituent layer being formed by constituents of the silicon-containing region and being susceptible to creep within an operating environment of the article, wherein the silicon-containing region defines a pluarality of channels and a plurality of ridges that interlock within the plurality of channels formed in the at least one outer layer to physically interlock the at least one outer layer with the silicon-containing region through the constituent layer.
2. The article according to claim 1, wherein the ridges have a height of from about 10 to about 250 µm.
3. The article according to claim 2, wherein the ridges have a height of from about 50 to about 200 µm.
4. The article according to claim 3, wherein the ridges have a height of from about 75 to about 125 µm.
5. The article according to claim 2, wherein the ridges have a wavelength of from about 20 to about 10,000 µm.
6. The article according to claim 5, wherein the ridges have a wavelength of from about 50 to about 2,000 µm

7. The article according to claim 6, wherein the ridges have a wavelength of from about 250 to about 1,000 µm.
8. The article according to claim 5, wherein the ridges have a ratio of a span of each ridge to the wavelength of the ridges to of about 0.1 to about 0.9.
9. The article according to claim 1, wherein the silicon-containing region is a bondcoat overlying a substrate of the article, and the bondcoat is formed of a material containing elemental silicon; silicon with one or more additional metal, intermetallic and/or ceramic phases; and/or one or more silicon alloys or compounds.
10. The article according to claim 9, wherein the bondcoat consists essentially of elemental silicon.
11. The article according to claim 9, wherein the bondcoat consists essentially of silicon with one or more additional ceramic phases chosen from the group consisting of silicon carbide and silicon nitride.
12. The article according to claim 1, wherein the at least one outer layer contains silicates.
13. The article according to claim 12, wherein the silicates comprise rare earth silicates and/or aluminosilicates.
14. The article according to claim 13, wherein the aluminosilicates comprise mullite and/or an alkaline earth aluminoslicate.
15. The article according to claim 14, wherein the alkaline earth aluminosilicate comprises BSAS.

16. The article according to claim 1, wherein the silicon-containing region is a substrate of the article and contains silicon carbide, silicon nitride, a silicide and/or silicon as a reinforcement phase and/or a matrix phase.
17. The article according to claim 16, wherein the substrate is a ceramic matrix composite material containing silicon carbide as a reinforcement phase and/or a matrix phase.
18. The article according to claim 16, wherein the silicide is a refractory metal silicide or a transition metal silicide.
19. The article according to claim 1, wherein the constituent layer comprises amorphous silica or crystalline silica or mixtures thereof.
20. The article according to claim 1, wherein the article is a rotating component of a turbine engine and the ridges extend in a direction substantially perpendicular to a shear load applied to the article during rotation of the article.