Part comprising a substrate and an environmental barrier
A part includes a substrate, having, adjacent to a surface of the substrate, at least a portion that is made from a material that contains silicon, and an environmental barrier formed on the surface of the substrate, the environmental barrier including at least a first layer including a rare earth disilicate of formula RE a 2 Si 2 O 7 present at a molar content lying in the range 70% to 99.9%, where RE a is a rare earth element; and at least one rare earth oxide of formula RE b 2 O 3 present at a molar content lying in the range 0.1% to 30%, where RE b is a rare earth element different from RE a .
1. A part comprising a substrate, having, adjacent to a surface of the substrate, at least a portion that is made from a material that contains silicon, and an environmental barrier formed on the surface of the substrate, the environmental barrier comprising at least a first layer comprising:
a rare earth disilicate of formula RE a 2 Si 2 O 7 present at a molar content lying in the range 85% to 95%, where RE a is a rare earth element, wherein RE a is selected from yttrium Y and ytterbium Yb; and
at least one rare earth oxide of formula RE b 2 O 3 present at a molar content lying in the range 5% to 15%, where RE b is a rare earth element different from RE a , wherein RE b is selected from terbium Tb, erbium Er, dysprosium Dy and lutetium Lu,
wherein the environmental barrier further comprises a second layer present on the first layer, the second layer comprising at least:
one rare earth monosilicate of formula RE c 2 SiO 5 , where RE c is a rare earth element at a molar content lying in the range 85% to 99.9%; and
at least one rare earth oxide of formula RE d 2 O 3 present at a molar content lying in the range 0.1% to 15%, where RE d is a rare earth element different from RE c .
2. A part according to claim 1 , wherein RE d is selected from terbium Tb, erbium Er, dysprosium Dy, gadolinium Gd, europium Eu, lutetium Lu, samarium Sm, yttrium Y, and ytterbium Yb.
3. A part according to claim 2 , wherein RE d is selected from terbium Tb, erbium Er, and dysprosium Dy.
4. A part according to claim 1 , wherein the rare earth monosilicate of formula RE c 2 SiO 5 is present in the second layer at a molar content lying in the range 85% to 95%, and wherein said at least one rare earth oxide of formula RE d 2 O 3 is present in the second layer at a molar content lying in the range 5% to 15%.
5. A part according to claim 1 , wherein RE c is selected from yttrium Y and ytterbium Yb.
6. A part according to claim 1 , wherein RE a is yttrium Y, RE c is ytterbium Yb, and RE d is selected from terbium Tb, erbium Er, and dysprosium Dy.
7. A part according to claim 1 , wherein the environmental barrier further comprises a third layer present between the first layer and the second layer, the third layer comprising:
the rare earth disilicate of formula RE a 2 Si 2 O 7 at a molar content equal to A·Ta, where Ta is the molar content of RE a 2 Si 2 O 7 in the first layer;
said at least one rare earth oxide of formula RE b 2 O 3 at a molar content equal to A·Tb, where Tb is the molar content of RE b 2 O 3 in the first layer; and
the rare earth monosilicate of formula RE c 2 SiO 5 at a molar content equal to (1−A)·Tc, where Tc is the molar content of RE c 2 SiO 5 in the second layer;
where A designates a weighting coefficient that is strictly greater than 0 and strictly less than 1.
8. A method of fabricating a part according to claim 1 , comprising forming the first layer of the environmental barrier on the surface of the substrate.
9. A method of using a part according to claim 1 , comprising using said part at a temperature higher than or equal to 800° C. in a medium that is oxidizing and wet.
10. A part according to claim 7 , wherein the molar content of RE d 2 O 3 in the second layer is less than the molar content of RE b 2 O 3 in the first layer.
11. A part according to claim 1 , wherein RP is yttrium Y.
12. A part according to claim 1 , wherein the at least one rare earth oxide of formula RE b 2 O 3 is present at a molar content lying in the range 5% to 10%.
13. A part comprising a substrate, having, adjacent to a surface of the substrate, at least a portion that is made from a material that contains silicon, and an environmental barrier formed on the surface of the substrate, the environmental barrier comprising at least a first layer comprising:
a rare earth disilicate of formula RE a 2 Si 2 O 7 present at a molar content lying in the range 85% to 95%, where RP is a rare earth element, wherein RE a is selected from yttrium Y and ytterbium Yb; and
at least one rare earth oxide of formula RE b 2 O 3 present at a molar content lying in the range 5% to 15%, where RE b is a rare earth element different from RE a , wherein RE b is erbium Er.
14. A part according to claim 13 , wherein RE a is yttrium Y.