HIGH-ENTROPY OXIDES FOR THERMAL BARRIER COATING (TBC) TOP COATS

Abstract

A thermal barrier coating (TBC) top coat which is a high entropy oxide (HEO) having a high configurational entropy, contains at least 5 different oxide-forming metallic cations, is a single phase or single crystalline structure, such as tetragonal or cubic over unexpectedly wide temperature ranges up to and beyond top coat operating temperatures of preferably at least 2300° F. The TBC top coats exhibit low thermal conductivity, good sintering resistance, excellent phase stability and good thermal cycling performance. At least five of the different oxide-forming metallic cations include: a) at least one of the transition metals: Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Ni, Cu, or Zn, and/or at least one of the lanthanides La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb. Dy, Ho, Er, Yb, or Lu. One of the at least five different oxide-forming metallic cations may also comprise at least one of the alkaline-earth metals: Be, Mg, Ca, Sr, or Ba.

Claims

1. A thermal barrier coating comprising: a top coat, wherein the top coat is a high entropy oxide (HEO) having a high configurational entropy, the HEO being of the form MxOy, where M represents a group of at least 5 different oxide-forming metallic cations, x represents the number of metal cations (M) or atoms, and y represents the number of oxygen anions (O) or atoms, wherein the HEO maintains phase composition without transformation from room temperature to the operating temperature range of the top coat, and the at least five of the different oxide-forming metallic cations (M) comprise: a) at least one of the transition metals Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Ni, Cu, or Zn, and/or b) at least one of the lanthanides La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Lu.

2. The thermal barrier coating of claim 1 wherein one of the at least five different oxide-forming metallic cations (M) comprise at least one of the alkaline-earth metals Be, Mg, Ca, Sr, or Ba.

3. The thermal barrier coating of claim 1 wherein the at least five of the different oxide-forming metallic cations (M) comprise: a) at least one of the transition metals Y, Ti, Zr, V, Cr, Mo, or W, and/or b) at least one of the lanthanides La, Ce, Pm, Sm, Eu, Gd, Tb, Dy, Er, or Yb.

4. The thermal barrier coating of claim 3 wherein one of the at least five different oxide-forming metallic cations (M) comprise at least one of the alkaline-earth metals Mg, or Ca.

5. The thermal barrier coating of claim 1 wherein the at least five of the different oxide-forming metallic cations (M) comprise Y, Zr, Ca, Gd, La, Yb, Ti, or Ce.

6. The thermal barrier coating of claim 1 comprising at least five different metal oxides from the group: a) Y.sub.2O.sub.3 in an amount of from 5% by weight to 20% by weight, b) ZrO.sub.2 in an amount of from 12% by weight to 55% by weight, c) CaO in an amount of from 0% by weight to 15% by weight, d) Gd.sub.2O.sub.3 in an amount of from 0% by weight to 30% by weight, e) La.sub.2O.sub.3 in an amount of from 0% by weight to 26% by weight, f) Yb.sub.2O.sub.3 in an amount of from 0% by weight to 32% by weight, g) TiO.sub.2 in an amount of from 0% by weight to 10% by weight, or h) CeO.sub.2 in an amount of from 0% by weight to 18% by weight, wherein the percentages of the at least five selected metal oxides add up to at least 97% by weight.

7. The thermal barrier coating of claim 1 comprising at least five different metal oxides from the group: a) Y.sub.2O.sub.3 in an amount of from 8% by weight to 18% by weight, b) ZrO.sub.2 in an amount of from 17% by weight to 52% by weight, c) CaO in an amount of from 0% by weight to 11% by weight, d) Gd.sub.2O.sub.3 in an amount of from 0% by weight to 28% by weight, e) La.sub.2O.sub.3 in an amount of from 0% by weight to 24% by weight, f) Yb.sub.2O.sub.3 in an amount of from 0% by weight to 30% by weight, g) TiO.sub.2 in an amount of from 0% by weight to 7% by weight, or h) CeO.sub.2 in an amount of from 0% by weight to 15% by weight, wherein the percentages of the at least five metal oxides add up to at least 97% by weight.

8. The thermal barrier coating of claim 1 comprising Y.sub.2O.sub.3 in an amount of from 8% by weight to 12% by weight, ZrO.sub.2 in an amount of from 48% by weight to 55% by weight, Yb.sub.2O.sub.3 in an amount of from 14% by weight to 18% by weight, TiO.sub.2 in an amount of from 4% by weight to 8% by weight, and CeO.sub.2 in an amount of from 12% by weight to 17% by weight, said percentages adding up to at least 97% by weight.

9. The thermal barrier coating of claim 8 further comprising at least one additional metal oxide in an amount up to 2% by weight, said weight percentages adding up to at least 99% by weight.

10. The thermal barrier coating of claim 8 further comprising HfO.sub.2 in an amount up to 2% by weight, said weight percentages adding up to at least 99% by weight.

11. The thermal barrier coating of claim 1 comprising: three metal oxides which are Y.sub.2O.sub.3 in an amount of from 13% by weight to 19% by weight, ZrO.sub.2 in an amount of from 14% by weight to 25% by weight, and Gd.sub.2O.sub.3 in an amount of from 20% by weight to 30% by weight, and any two of the metal oxides which are Yb.sub.2O.sub.3 in an amount of from 23% by weight to 32% by weight, La.sub.2O.sub.3 in an amount of from 18% by weight to 25% by weight, or CaO in an amount of from 6% by weight to 12% by weight, the percentages of the five metal oxides adding up to at least 97% by weight.

12. The thermal barrier coating of claim 1, wherein the configurational entropy of the oxide is at least 1.5R per mole, where R is the gas constant J.Math.K−1.Math.mol−1.

13. The thermal barrier coating of claim 1, wherein the five or more different oxide-forming metallic cations are present in compositions between 5 and 35 atomic %.

14. The thermal barrier coating of claim 1, wherein M represents at least one member of Group II of the Periodic Table.

15. The thermal barrier coating of claim 1, wherein M represents at least one from the group consisting of at least two lanthanides and at least two transition metals.

16. (canceled)

17. The thermal barrier coating of claim 1, further comprising a thermal barrier coating bond coat.

18. The thermal barrier coating of claim 1, wherein the HEO is a single phase or single crystalline structure from room temperature up to at least 2,000° F.

19. The thermal barrier coating of claim 1, wherein the HEO is a single phase or single crystalline structure which is cubic from room temperature up to at least 2,000° F.

20. The thermal barrier coating of claim 1, wherein the HEO is a single phase or single crystalline structure from 1800° F. to 2600° F.

21. The thermal barrier coating of claim 1, wherein the HEO is a single phase or single crystalline structure which is tetragonal from room temperature up to at least 2000° F.

22. The thermal barrier coating of claim 1, wherein the HEO is a single phase or single crystalline structure from room temperature up to the melting point of the HEO.

23. The thermal barrier coating of claim 1, wherein the HEO does not undergo phase transformation to a different crystalline structure for at least 700° F. up to the melting point of the HEO.

24. A thermal barrier coating material comprising: a high entropy oxide (HEO) having a high configurational entropy, the HEO being of the form MxOy, where M represents a group of at least 5 different oxide-forming metallic cations, x represents the number of metal cations (M) or atoms, and y represents the number of oxygen anions (O) or atoms, wherein the HEO is a single phase across the operating temperature range from room temperature to 2,000° F., and at least five of the different oxide-forming metallic cations (M) comprise: a) at least one of the transition metals Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Ni, Cu, or Zn, and/or b) at least one of the lanthanides La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Lu.

25. The thermal barrier coating material of claim 24 wherein one of the at least five different oxide-forming metallic cations (M) comprise at least one of the alkaline-earth metals Be, Mg, Ca, Sr, or Ba.

26. The thermal barrier coating material of claim 24 wherein the at least five of the different oxide-forming metallic cations (M) comprise Y, Zr, Ca, Gd, La, Yb, Ti, or Ce.

27. The thermal barrier coating material of claim 24 comprising at least five different metal oxides which are from the group: a) Y2O.sub.3 in an amount of from 5% by weight to 20% by weight, b) ZrO.sub.2 in an amount of from 12% by weight to 55% by weight, c) CaO in an amount of from 0% by weight to 15% by weight, d) Gd.sub.2O.sub.3 in an amount of from 0% by weight to 30% by weight, e) La.sub.2O.sub.3 in an amount of from 0% by weight to 26% by weight, f) Yb.sub.2O.sub.3 in an amount of from 0% by weight to 32% by weight, g) TiO.sub.2 in an amount of from 0% by weight to 10% by weight, or h) CeO.sub.2 in an amount of from 0% by weight to 18% by weight, wherein the percentages of the at least five of the metal oxides add up to at least 97% by weight.

28. The thermal barrier coating material of claim 24 comprising Y.sub.2O.sub.3 in an amount of from 8% by weight to 12% by weight, ZrO.sub.2 in an amount of from 48% by weight to 55% by weight, Yb2O.sub.3 in an amount of from 14% by weight to 18% by weight, TiO.sub.2 in an amount of from 4% by weight to 8% by weight, and CeO.sub.2 in an amount of from 12% by weight to 17% by weight, said percentages adding up to at least 97% by weight.

29. The thermal barrier coating material of claim 24 which is at least one of a powder, a wire, a bar, an ingot and a rod.

30. (canceled)

31. A coated substrate comprising a substrate and a thermal barrier coating of claim 17 wherein the top coat of the thermal barrier coating is bonded by the thermal barrier coating bond coat to the substrate.

32. A method for reducing delamination of a top coat from a substrate comprising bonding a thermal barrier coating of claim 17 to a substrate wherein the top coat of the thermal barrier coating is bonded by the thermal barrier coating bond coat to the substrate.

33. The thermal barrier coating material of claim 24, which is agglomerated and sintered.

34. The thermal barrier coating material of claim 33 which is in powdered form.

35. A method for making a thermal barrier coating comprising agglomerating and sintering a thermal barrier coating material of claim 24 to obtain a sintered agglomerate, and forming the sintered agglomerate into a powder for thermal spraying.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The present invention is further illustrated by the accompanying drawings wherein:

[0056] FIG. 1 schematically illustrates a coated substrate having a thermal barrier coating (TBC) system which includes a top coat, such as a thermal barrier coating (TBC) bonded to the bond coat or coating in accordance with the present invention.

[0057] FIG. 2 shows the morphology (SEM micrograph) for the HEO agglomerated and sintered powder of Sample HEO 1.

[0058] FIG. 3 shows the cross section (SEM micrograph) for the HEO agglomerated and sintered powder of Sample HEO 1.

[0059] FIG. 4 shows the cross section microstructure (SEM micrograph) for the HEO thermal barrier coating, TBC top coat, of Sample HEO 1.

[0060] FIG. 5 shows the morphology (SEM micrograph) for the HEO agglomerated and sintered powder of Sample HEO 2.

[0061] FIG. 6 shows the cross section (SEM micrograph) for the HEO agglomerated and sintered powder of Sample HEO 2.

[0062] FIG. 7 shows the cross section microstructure (SEM micrograph) for the HEO thermal barrier coating, TBC top coat, of Sample HEO 2.

[0063] FIG. 8 shows the morphology (SEM micrograph) for the HEO agglomerated and sintered powder of Sample HEO 3.

[0064] FIG. 9 shows the cross section (SEM micrograph) for the HEO agglomerated and sintered powder of Sample HEO 3.

[0065] FIG. 10 shows the cross section microstructure (SEM micrograph) for the HEO agglomerated and sintered thermal barrier coating, TBC top coat, of Sample HEO 3.

[0066] FIG. 11 shows the morphology (SEM micrograph) for the HEO agglomerated and sintered powder of Sample HEO 4.

[0067] FIG. 12 shows the cross section (SEM micrograph) for the HEO agglomerated and sintered powder of Sample HEO 4.

[0068] FIG. 13 shows the cross section microstructure (SEM micrograph) for the HEO agglomerated and sintered thermal barrier coating, TBC top coat, of Sample HEO 4.

[0069] FIG. 14 shows the experimental XRD pattern for Sample HEO 4.

DETAILED DESCRIPTION OF THE INVENTION

[0070] The present invention provides a top coat, such as a thermal barrier coating (TBC) for a thermal barrier coating system which includes the top coat and at least one bond coat for bonding to a substrate, such as a superalloy employed in high temperature gas turbine engine components. There could also be multiple top coat layers on top of the at least one bond coat layer. The present invention also provides a thermal barrier coating material or top coat material for making the top coat or thermal barrier coating. The TBC top coats exhibit low thermal conductivity, good sintering resistance, excellent phase stability and good thermal cycling performance. The top coats are high entropy oxides which exhibit a single phase or single crystalline structure, such as tetragonal or cubic for prolonged periods over an unexpectedly wide temperature range which may be from room temperature to the operating temperature of top coats for turbine blades in jet engines. The high entropy oxide top coats of the present invention which exhibit a single phase throughout the heat cycling do not delaminate from a thermal bond coating or substrate at high operating temperatures due to substantial volume changes caused by a change in crystal structure or phase change and thermal internal stresses. Low coating weight and low coating density are achieved while providing low heat conductivity and maintaining single phase crystalline structures such as cubic or tetragonal, over prolonged times and unexpectedly wide temperature ranges up to and beyond top coat operating temperatures, which may be at least 1800° F., for example 2,000° F. or higher, preferably at least 2300° F., or up to the melting point of the TBC top coat. In embodiments of the invention, more than one phase or crystalline structure may be present in the top coat or thermal barrier coating provided it does not adversely result in substantial volume changes caused by a change in crystal structure so as to cause delamination. While only a single phase or crystalline structure is most preferred, i.e. a phase volume of 100% (as measured for example, by X-Ray Diffraction), in embodiments of the invention where two or more phases or crystalline structures are present, the primary phase volume fraction may, for example, be at least 80%, preferably at least 90%, more preferably at least 98%.

[0071] The TBC top coats using a bond coat to bond to a substrate such as a superalloy exhibit unexpectedly high thermal cyclic fatigue resistance.

[0072] The TBC top coat, and TBC material for making the top coat is a high entropy oxide (HEO) having a high configurational entropy. In aspects of the present invention, the single phase may be retained without transformation to another phase or crystalline structure from room temperature to the operating temperature of top coats for turbine components. The HEO is of the form M.sub.xO.sub.y, where M represents a group of at least 5 different oxide-forming metallic cations, x represents the number of metal cations (M) or atoms, and y represents the number of oxygen anions (O) or atoms.

[0073] In embodiments of the invention, the TBC top coat and the TBC material used to make the top coat, and the HEO is a single phase or single crystalline structure for an unexpectedly wide temperature range wherein the HEO does not undergo phase transformation to a different crystalline structure, for example, for a temperature range of at least 700° F., preferably at least 1,000° F., most preferably for at least 1,500° F. prior to or up to the top coat maximum operating temperature or the melting point of the HEO. For example, in aspects of the present invention, if the maximum operating temperature in a turbine engine component is 2,000° F., then the HEO may have a single phase or single crystalline structure from 1,300° F. to 2,000° F., preferably from 1,000° F. to 2,000° F., most preferably from 500° F. to 2,000° F., or more preferably from room temperature to 2000° F. or higher, preferably to at least 2300° F., such as to an HEO melting point of 2400° F. In aspects of the invention, the HEO may be a single phase or single crystalline structure over or throughout an 800° F. temperature range extending from 1800° F. to 2,600° F., or extending from 1,300° F. to 2,100° F. The wider the temperature range without a phase change, the better, because, for example, the number of phases changes would be fewer as the top coat cycles up to and back down from the turbine operating temperature, or as the operating temperature fluctuates, thereby helping to reduce thermal expansion and contraction and thermal stresses.

[0074] In preferred aspects of the invention, the TBC top coat, TBC coating material, and the HEO may have only a single phase or single crystalline structure which is only, for example, cubic or tetragonal from room temperature up to at least 1800° F., preferably up to at least 2,000° F., more preferably, up to at least 2300° F., for example from room temperature up to the melting point of the HEO. In embodiments of the invention, the HEOs have a melting point of at least 1,150° C. (2,102° F.), preferably at least 1,300° C. (2,372° F.), more preferably at least 1,315° C. (2,399° F.).

[0075] In embodiments of the invention the inherent thermal conductivity at 25° C. of the HEO topcoat or coating may be less than 1.5 (W/m-K) preferably less than 1.2 (W/m-K), and more preferably less than 0.9 W/m-K. In embodiments of the invention, the HEO coating may have a density lower than the theoretical density (i.e. may contain porosity) thus reducing the thermal conductivity of the HEO topcoat coating to less than 1.3 (W/m-K) preferably less than 1.0 (W/m-K) and more preferably less than 0.8 (W/m-K). This is demonstrated in Table 2.

[0076] In embodiments of the invention the TBC top coat or coating Archimedes density may be less than 7 g/cm.sup.3, for example from 5 g/cm.sup.3, to 6.5 g/cm.sup.3, preferably less than 6.3 g/cm.sup.3, for example from 5.25 g/cm.sup.3 to 6.25 g/cm.sup.3, more preferably less than 6.0, for example 5.30 g/cm.sup.3 to 5.90 g/cm.sup.3.

[0077] In embodiments of the invention, the oxide ceramic, or HEO intended to be used as a thermally insulating material or thermal barrier coating, may have an overall combined atomic composition of which can be expressed as M.sub.xO.sub.y where M represents a group of at least 5 different oxide-forming metallic cations and where the configurational entropy S.sub.CONFIG of the oxide is 1.5R per mole or greater, where R is the gas constant 8.314 J.Math.K.sup.−1.Math.mol.sup.−1; this definition using the value of S.sub.CONFIG being a commonly-accepted definition of a high-entropy material. The metal cations “M” and oxygen anions “O” may be distributed on one or more crystal sub-lattices. In aspects of the present invention, the TBC top coat may have a configurational entropy S.sub.config of the oxide which is below 1.5R per mole, for example 1.0 R per mole or greater, or 1.3R per mole or greater provided the heat conductivity is low and the metal oxide maintains phase composition for an unexpectedly wide temperature range, as discussed above, wherein the metal oxide does not undergo phase transformation and the primary phase volume fraction maintains, for example, at least 80%, preferably at least 90%, more preferably at least 98% and the melting point is above the operating temperature of the coating as described above.

[0078] M.sub.1O.sub.y is standard metallurgical shorthand. For example, the carbide (Cr,Mo,W,Fe).sub.23C.sub.6 is commonly referred to as M.sub.23C.sub.6. and in the same way M.sub.xO.sub.y may be used to describe the oxide (Zr,Ce,Y,Yb,Gd,Dy).sub.xO.sub.y where “M” represents 5 or more oxide-forming metals.

[0079] In embodiments of the present inventions, these metals “M” may preferably be selected from the group of non-toxic and non-radioactive oxide-forming metals, such as: Transition Metals: [0080] Sc, Y [0081] Ti, Zr, Hf [0082] V, Nb, Ta [0083] Cr, Mo, W [0084] Mn, Re [0085] Fe, Ru, Co, Ni, Cu, Zn, and

[0086] Lanthanides:

[0087] La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu.

[0088] In some embodiments of the invention at least one alkaline-earth metal may preferably be selected, such as [0089] Be, Mg, Ca, Sr, Ba

[0090] In embodiments of the invention, the following metals are more preferred for use in HEO TBCs:

[0091] Transition Metals: [0092] Y [0093] Ti, Zr, Hf, V [0094] Cr, Mo, W

[0095] Lanthanides: [0096] La, Ce, Pm, Sm [0097] Eu, Gd [0098] Tb [0099] Dy, Er, Yb

[0100] In some embodiments of the invention at least one alkaline-earth metal is more preferably selected, such as [0101] Mg, Ca

[0102] In embodiments of the invention, at least one, preferably at least two of the transition metals, and/or at least one, preferably at least two of the lanthanides may be employed in the at least five of the different oxide-forming metallic cations (M).

[0103] While hafnium (Hf) has a very high melting point, in embodiments of the invention, it may be eliminated or used in low amounts, for example less than 2.0% by weight, preferably less than 1% by weight. Although higher amounts of hafnium may be employed, for example up to 15% by weight or more, high contents of hafnium are not necessarily required, thereby allowing lowering of the coating weight and density, while providing low heat conductivity and maintaining single phase crystalline structures such as cubic or tetragonal, over prolonged periods of time for unexpectedly wide temperature ranges up to and beyond top coat operating temperatures.

[0104] Still further, the metal cations “M” and oxygen anions “O” may be distributed on one or more crystal sub-lattices. This means that the oxide, such as the exemplary oxide (Zr,Ce,Y,Yb,Gd,Dy).sub.xO.sub.y, may be physically manifested as one combined oxide structure of as-yet-unknown crystallography (Zr,Ce,Y,Yb,Gd,Dy).sub.xO.sub.y, or it may partition itself into 2 (or more) more-commonly-known crystal lattices e.g. (Y,Yb,Gd,Dy).sub.2O.sub.3 and (Zr,Ce)O.sub.2. Accordingly, in the latter case this would imply 2 atoms from the group (Y,Yb,Gd,Dy) for every 3 oxygen atoms, and 1 atom from the group Zr,Ce for every 2 oxygen atoms, within the overall composition. With intimate mixing of these oxide lattices it may not necessarily be able to detect separate phases in the HEO structure when examined by scanning electron microscopy.

[0105] In aspects of the present invention, known high entropy oxides, such as those of the above-discussed and listed references incorporated by reference herein in their entireties, may be employed as a top coat provided they are primarily single phase, or single crystal structure such as tetragonal or cubic, provided the heat conductivity is low and the metal oxide maintains phase composition for an unexpectedly wide temperature range, as discussed above, and the melting point is above the operating temperature of the coating as described above. Most preferably, the HEO should not undergo significant transformation or alter phase fraction from room temperature to the operating temperature or melting point of the top coat, as described above.

[0106] In accordance with the present invention, in embodiments the thermal barrier coating may include a top coat, wherein the top coat is a high entropy oxide (HEO) having a high configurational entropy, the HEO being of the form M.sub.xO.sub.y, where M represents a group of at least 5 different oxide-forming metallic cations, x represents the number of metal cations (M) or atoms, and y represents the number of oxygen anions (0) or atoms, the HEO is a single phase across the operating temperature range of the top coat, and at least five of the different oxide-forming metallic cations (M) may comprise: [0107] a) at least one of the alkaline-earth metals or Group II of the Periodic Table, Be, Mg, Ca, Sr, or Ba, and/or [0108] b) at least one of the transition metals Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Ni, Cu, or Zn, and/or [0109] c) at least one of the lanthanides La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Lu.

[0110] In preferred embodiments of the thermal barrier coating the at least five of the different oxide-forming metallic cations (M) may comprise: [0111] a) at least one of the transition metals Y, Ti, Zr, V, Cr, Mo, or W, and/or [0112] b) at least one of the lanthanides La, Ce, Pm, Sm, Eu, Gd, Tb, Dy, Er, or Yb, and [0113] c) in some embodiments at least one alkaline-earth metal: Mg, or Ca.
More preferably, the at least five of the different oxide-forming metallic cations (M) of the thermal barrier coating comprise at least five of Y, Zr, Ca, Gd, La, Yb, Ti, or Ce.

[0114] In aspects of the present invention the thermal barrier coating and the thermal barrier coating material or top coat material may comprise at least five different metal oxides which are: [0115] a) Y.sub.2O.sub.3 in an amount of from 5% by weight to 20% by weight, preferably from 8% by weight to 18% by weight, [0116] b) ZrO.sub.2 in an amount of from 12% by weight to 55% by weight, preferably from 17% by weight to 52% by weight, [0117] c) CaO in an amount of from 0% by weight to 15% by weight, preferably from 0% by weight to 11% by weight, [0118] d) Gd.sub.2O.sub.3 in an amount of from 0% by weight to 30% by weight, preferably from 0% by weight to 28% by weight, [0119] e) La.sub.2O.sub.3 in an amount of from 0% by weight to 26% by weight, preferably from 0% by weight to 24% by weight, [0120] f) Yb.sub.2O.sub.3 in an amount of from 0% by weight to 32% by weight, preferably from 0% by weight to 30% by weight, [0121] g) TiO.sub.2 in an amount of from 0% by weight to 10% by weight, preferably from 0% by weight to 7% by weight, or [0122] h) CeO.sub.2 in an amount of from 0% by weight to 18% by weight, preferably from 0% by weight to 15% by weight,
the percentages of a) to h) adding up to 100% by weight. In embodiments, the thermal barrier coating and the thermal barrier coating material or top coat material may further include at least one additional metal oxide, such as HfO.sub.2, SiO.sub.2, MgO, or Al.sub.2O.sub.3, as melting point adjusters, stabilizers, dopants, or impurities, in an amount up to 3% by weight, for example, up to 2% by weight or less than or equal to 1% by weight, the weight percentages of all of the oxides adding up to 100% by weight. In embodiments of the invention, the percentages of the five metal oxides may add up to at least 97% by weight, for example at least 99% by weight, and the additional metal oxide or oxides may be present in an amount of up to 3% by weight, or up to 1% by weight.

[0123] In more preferred embodiments, the thermal barrier coating and the thermal barrier coating material or top coat material may comprise at least five different metal oxides which include: Y.sub.2O.sub.3 in an amount of from 8% by weight to 12% by weight, ZrO.sub.2 in an amount of from 48% by weight to 55% by weight, Yb.sub.2O.sub.3 in an amount of from 14% by weight to 18% by weight, TiO.sub.2 in an amount of from 4% by weight to 8% by weight, and CeO.sub.2 in an amount of from 12% by weight to 17% by weight, said percentages adding up to 100% by weight. Hafnium, and additional other metal oxides may optionally be included in an amount up to 2% by weight, for example, less than or equal to 1% by weight, the weight percentages of all of the oxides adding up to 100% by weight.

[0124] In other preferred embodiments, the thermal barrier coating and the thermal barrier coating material or top coat material may comprise at least five different metal oxides which include:

[0125] three metal oxides which are [0126] Y.sub.2O.sub.3 in an amount of from 13% by weight to 19% by weight, [0127] ZrO.sub.2 in an amount of from 14% by weight to 25% by weight, and [0128] Gd.sub.2O.sub.3 in an amount of from 20% by weight to 30% by weight, and [0129] any two of the metal oxides which are [0130] Yb.sub.2O.sub.3 in an amount of from 23% by weight to 32% by weight, [0131] La.sub.2O.sub.3 in an amount of from 18% by weight to 25% by weight, or [0132] CaO in an amount of from 6% by weight to 12% by weight,
the percentages of the five metal oxides adding up to at least 97% by weight and preferably between 98% and 100% by weight.

[0133] In embodiments of the invention, the TBC top coat material or HEO may be manufactured in powder form or bulk form, such as wire, bar, rod or ingot form. The TBC top coat material powder may be a homogeneous mixture of separate powders of each of the components of the TBC top coat material. The TBC top coat material powder may also be composed of particles, each of which contain all or some of the components of the bond coating material. For example, a bulk form of all the components of the TBC top coat material or HEO may be ground to obtain a powder. The particle size of the TBC top coat material may depend upon the coating method employed. Conventional particle size distributions conventionally employed with a given coating method may be used with the TBC top coat materials or HEOs of the present invention.

[0134] The bond coating material may be any conventional or known bond coat material such as those used for the coating of gas turbine engine parts, such as known MCrAlY bonding layers for bonding a TBC top coat to a substrate, such as a superalloy. By way of example, M may represent Ni, Co, Fe or their combinations. To increase the performance of a bond coat, Hf, Re and Pt and various other rare earth elements may often be added in advanced bond coats. Non-limiting examples of the bond coat material which may be employed include those disclosed in U.S. Pat. No. 4,117,179 to Jackson et al, U.S. Pat. No. 5,141,821 to Lugscheider, and U.S. Pat. No. 4,275,124 to McComas et al, the disclosures of which are each herein incorporated by reference in their entireties.

[0135] The substrate may be any known or conventional material or article in need of a top coat or barrier coating (TBC). Non-limiting examples of the substrate include alloys, or superalloys used in the manufacture of gas turbine engine parts, such as Hastelloy® X, as disclosed in U.S. Pat. No. 4,124,737 to Wolfa et al, the disclosure of which is herein incorporated by reference in its entirety. Hastelloy®X, as disclosed by Wolfa et al, has a nominal composition of 22.0 wt. % chromium; 9.0 wt. % molybdenum, 18.5 wt. % iron; 1.5 wt. % cobalt; 0.6 wt. % tungsten, 1.0 wt % silicon, 1.0 wt. % manganese, 0.1 wt. % carbon, and the balance nickel. Other non-limiting examples of known and conventional substrates which may be coated with the TBC top coat of the present invention include steel, stainless steel, other iron-base alloys with low alloying content, chromium and chromium base alloys, and the refractory metal and refractory metal base alloys. Non-limiting examples of superalloy substrates which may be coated with the TBC top coat of the present invention are known carbide reinforced superalloys, such as nickel-base and cobalt-base superalloys, directionally solidified nickel-base and cobalt-base superalloys including eutectic alloys, as well as refractory alloys, etc. as disclosed in U.S. Pat. No. 4,117,179, the disclosure of which is hereby incorporated by reference in its entirety. Non-limiting examples of substrates or articles which may be coated with the TBC top coat of the present invention include components used in the hot sections of gas turbines and various jet engine components.

[0136] In another aspect of the invention, as schematically illustrated in FIG. 1, a thermal barrier coating (TBC) system 1 includes a top coat 2 and the bond coat or bond coating 3, with the top coat 2, such as a TBC, being bonded to the bond coat or bond coating 3 at the top coat/bond coat interface 5. A coated substrate 10 comprises a substrate 15 and the thermal barrier coating system 1 bonded to the substrate 15 by the bond coat or coating 3 at the substrate/bond coat interface 20. The thermal barrier coating system 1 may be produced from the thermal spray powder. The thermal barrier coating system 1 is bonded to a substrate 15, such as a superalloy or gas engine turbine component, by the bond coat or bond coating 3, which is between the top coat 2 and the substrate 15.

[0137] In embodiments of the invention, multiple bond coats or bond coatings 3 and multiple top coats 2 may be employed, with each top coat 2 being on top of a bond coat 3 in alternating fashion, to provide a plurality of TBC systems 1, stacked and bonded one on another, with the bottommost bond coat 3 bonded to the substrate 15.

[0138] In an additional aspect of the invention, a method is provided for reducing delamination of a top coat from a substrate by bonding the TBC top coat having a single phase or single crystalline structure, such as a tetragonal or cubic crystalline structure to the substrate with a bond coat or coating.

[0139] The TBC top coat, or HEO, and the bond coat or bond coating or bonding layer, may be deposited, applied, or laminated on the substrate using conventional thermal spray processes, such as air plasma spray, suspension plasma, high velocity oxy-fuel spray (HVOF), low pressure plasma spray (LPPS), vacuum plasma spray (VPS), chemical vapor deposition (CVD), plasma physical vapor deposition (PS-PVD), physical vapor deposition (PVD) which includes vacuum deposition methods, such as sputtering and evaporation, and conventional flame spray processes, such as combustion wire spray, and combustion powder spray, electric arc wire spray, powder flame spray, and electron beam physical vapor deposition (EBPVD). Conventional and known coating layer thicknesses may be employed for the bond coat or coating, and the top coat or TBC or HEO.

[0140] In embodiments of the invention, a thermal barrier coating material or the HEO material may be manufactured by agglomerating and sintering a thermal barrier coating material to obtain a sintered agglomerate, and forming the sintered agglomerate into a powder for thermal spraying using known techniques and processes. Agglomerating and sintering is a specifically novel way to manufacture HEOs. The process is advantageous because it: 1) reduces the diffusion pathways, and 2) is more amenable to industrial production. The reduction of the diffusion pathways is very advantageous as homogenizing high temperature materials into a single phase can be expensive and time consuming when compared with other processes. In embodiments of the invention, a thermal barrier coating may be manufactured by agglomerating and sintering a thermal barrier coating material to obtain a sintered agglomerate, and forming the sintered agglomerate into a powder for thermal spraying using known process parameters and techniques.

[0141] The present invention is further illustrated by the following non-limiting examples where all parts, percentages, proportions, and ratios are by weight, all temperatures are in ° C., and all pressures are atmospheric unless otherwise indicated.

EXAMPLES

[0142] The compositions of four HEO TBC top coat materials (as powders), of the present invention used to make HEO TBC top coats of the present invention for a coated substrate are shown in Table 1.

[0143] The Table 1 compositions of the samples tested, and the results of the testing are:

TABLE-US-00001 TABLE 1 Compositions of the HEO TBC Top Coat Materials Used To Make HEO TBC Top Coats For A Coated Substrate ZrO.sub.2 Y.sub.2O.sub.3 Gd.sub.2O.sub.3 Yb.sub.2O.sub.3 La.sub.2O.sub.3 CaO CeO.sub.2 TiO.sub.2 Traces Sample wt % wt % wt % wt % wt % wt % wt % wt % wt % HEO 1 23.4 16.0 26.0 23.5 10.5 0.6 HEO 2 18.3 17.0 27.1 29.4 7.9 0.3 HEO 3 16.4 14.9 23.3 25.3 20.0 0.1 HEO 4 51.9 9.9 17.1 14.6 6.0 0.5

[0144] For the TBC top coat materials (HEOs): the coating density, relative density, coating phase, and thermal conductivity measured at 25° C., are shown in Table 2.

[0145] The Table 2 results of the properties for the samples tested are:

TABLE-US-00002 TABLE 2 Properties of the HEO TBC Top Coats Units Property Measurement HEO 1 HEO 2 HEO 3 HEO 4 Archimedes Density g/cm.sup.3 5.36 5.72 6.23 5.87 Relative Density % 91.8  92.3  92.7  93.1  Primary Phase Fraction from XRD (Vol %) Vol % 65% 87% >98% >99% Thermal conductivity at 25° C. W/m-K 1.22 1.30 1.21 0.77

[0146] The powder morphology (SEM micrograph), powder cross section (SEM micrograph), and coating microstructure (SEM micrograph) for the HEO agglomerated and sintered thermal barrier coatings of samples HEO 1, HEO 2, HEO 3 and HEO 4 are shown in FIGS. 2-13. An example of the X-Ray diffraction pattern of one of the HEO compounds, HEO 4, is shown in FIG. 14.

[0147] Further, at least because the invention is disclosed herein in a manner that enables one to make and use it, by virtue of the disclosure of particular exemplary embodiments, such as for simplicity or efficiency, for example, the invention can be practiced in the absence of any step, additional element or additional structure that is not specifically disclosed herein.

[0148] It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.