Multi-environmental barrier coating, processes for coating articles, and their coated articles
A coated article including an article having a surface; an oxidation resistant bond coat layer deposited on the surface, the oxidation resistant bond coat layer comprising a metal silicide phase, a crystalline ceramic phase and an amorphous ceramic phase, wherein the metal silicide phase has an aspect ratio greater than 1:1 but less than 50:1.
1. A coated article, comprising:
an article having a surface; and
an oxidation resistant bond coat layer deposited on the surface, the oxidation resistant bond coat layer comprising a metal silicide phase, a crystalline ceramic phase and an amorphous ceramic phase, wherein the metal silicide phase has an aspect ratio greater than 1:1 but less than 50:1.
2. The coated article as recited in claim 1 , wherein the metal silicide phase and the crystalline ceramic phase each have an aspect ratio greater than 3:1.
3. The coated article as recited in claim 1 , wherein the metal silicide phase and the crystalline ceramic phase each have an aspect ratio greater than 5:1.
4. The coated article as recited in claim 1 , wherein a volume fraction of the metal silicide phase ranges between 20-80 vol. %, a volume fraction of the crystalline ceramic phase is 25-75 vol. %, and a volume fraction of the amorphous ceramic phase ranges between 1-30 vol. %.
5. The coated article as recited in claim 1 , wherein a volume fraction of the metal silicide phase is 60 vol. % MoSi 2 , a volume fraction of the crystalline ceramic phase is 25 vol. % HfSiO 4 , and a volume fraction of the amorphous ceramic phase is 15 vol. % boro-silicate glass where the glass has the composition (Si 0.75 B 0.15 Al 0.05 Na 0.05 )O 2 with porosity less than 10%.
6. The coated article as recited in claim 1 , wherein a volume fraction of the metal silicide phase is 60 vol. % MoSi 2 , a volume fraction of the crystalline ceramic phase is 25 vol. % HfSiO 4 , and 5% HfB 2 ; and a volume fraction of the amorphous ceramic phase is 10 vol. % boro-silicate glass where the glass has the composition (Si 0.75 B 0.15 Al 0.05 Na 0.05 )O 2 with porosity less than 10%.
7. The coated article as recited in claim 1 , further comprising an environmental protective top coat layer disposed upon the oxidation resistant bond coat layer, whereby the oxidation resistant bond coat layer is operable to repair a crack in the environmental protective top coat layer during operation of the coated article.
8. The coated article as recited in claim 1 , wherein the metal silicide phase has an aspect ratio greater than 3:1.
9. The coated article as recited in claim 1 , wherein the metal silicide phase has an aspect ratio greater than 5:1.