COATING FOR PROTECTING EBC AND CMC LAYERS AND THERMAL SPRAY COATING METHOD THEREOF

Abstract

A multi-layer coating arrangement includes an environmental barrier coating (EBC) over a substrate; and at least one dense vertically cracked (DVC) coating layer over the EBC. The at least one DVC layer is resistant to erosion, water vapor corrosion and to calcium-magnesium-aluminum-silicate (CMAS).

Claims

1. A multi-layer coating arrangement comprising: an environmental barrier coating (EBC) over a substrate; and at least one dense vertically cracked (DVC) coating layer over the EBC, the at least one DVC layer being resistant to at least one of erosion, water vapor corrosion, and calcium-magnesium-aluminum-silicate (CMAS).

2. The coating of claim 1, wherein the at least one DVC layer is a top layer.

3. The coating of claim 1, further comprising at least one bond coating layer between the EBC and the substrate.

4. The coating of claim 1, wherein the substrate comprises a ceramic matrix composite (CMC).

5. The coating of claim 1, wherein the at least one DVC coating layer comprises RE-stabilized ZrO.sub.2 or RE-stabilized HfO.sub.2.

6. The coating of claim 1, wherein the at least one DVC coating layer comprises RE-stabilized ZrO.sub.2 mixed with a rare earth oxide, or comprises RE-stabilized HfO.sub.2 mixed with a rare earth oxide.

7. The coating of claim 1, wherein the at least one DVC coating layer comprises RE-stabilized ZrO.sub.2 mixed with a rare earth silicate, or comprises RE-stabilized HfO.sub.2 mixed with a rare earth silicate.

8. The coating of claim 1, wherein the at least one DVC coating layer comprises RE-stabilized ZrO.sub.2 mixed with a rare earth aluminate, or comprises RE-stabilized HfO.sub.2 mixed with a rare earth aluminate.

9. The coating of claim 1, wherein the at least one DVC coating layer comprises RE-stabilized ZrO.sub.2 mixed with a rare earth aluminate or silicate, or comprises RE-stabilized HfO.sub.2 mixed with a rare earth aluminate or silicate.

10. The coating of claim 1, wherein the at least one DVC coating layer comprises RE-stabilized ZrO.sub.2 mixed with an alkaline oxide, or comprises RE-stabilized HfO.sub.2 mixed with an alkaline oxide.

11. The coating of claim 1, wherein the at least one DVC coating layer comprises RE-stabilized ZrO.sub.2 mixed with a gadolinium zirconate, or comprises RE-stabilized HfO.sub.2 mixed with a gadolinium zirconate.

12. The coating of claim 1, wherein the at least one DVC coating layer comprises rare earth silicates.

13. The coating of claim 1, wherein the at least one DVC coating layer comprises a mixture of two or more of: RE-stabilized ZrO.sub.2 or RE-stabilized HfO.sub.2; RE-stabilized ZrO.sub.2 mixed with a rare earth oxide, or RE-stabilized HfO.sub.2 mixed with a rare earth oxide; RE-stabilized ZrO.sub.2 mixed with a rare earth silicate, or RE-stabilized HfO.sub.2 mixed with a rare earth silicate; RE-stabilized ZrO.sub.2 mixed with a rare earth aluminate, or RE-stabilized HfO.sub.2 mixed with a rare earth aluminate; RE-stabilized ZrO.sub.2 mixed with a rare earth aluminate or silicate, or RE-stabilized HfO.sub.2 mixed with a rare earth aluminate or silicate; RE-stabilized ZrO.sub.2 mixed with an alkaline oxide, or RE-stabilized HfO.sub.2 mixed with an alkaline oxide; RE-stabilized ZrO.sub.2 mixed with a gadolinium zirconate, or RE-stabilized HfO.sub.2 mixed with a gadolinium zirconate; and Rare earth silicates.

14. The coating of claim 1, wherein the at least one DVC coating layer comprises full thickness vertical cracks.

15.-26. (canceled)

27. A method of forming a coating that is resistant to erosion, water vapor corrosion and to CMAS on a substrate coated with at least one EBC coating layer, the method comprising: plasma spraying a DVC coating material over the at least one EBC coating layer.

28. The method of claim 27, wherein the coating further comprises at least one bond coating layer between the at least one EBC coating layer and the substrate.

29. The method of claim 27, wherein the plasma spraying comprises one of: atmospheric plasma spraying (APS); physical vapor deposition (PS-PVD); and suspension plasma spray (SPS).

30.-31. (canceled)

32. The coating of claim 1, wherein no CTE-mitigating layer is present between the DVC layer and the EBC.

33. The coating of claim 1, wherein no porous vertically cracked (PVC) intermediate layer is present between the DVC layer and the EBC.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings are included to provide further understanding of the invention and are incorporated in and constitute a part of this specification. The accompanying drawings illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the figures:

[0046] FIG. 1 schematically shows a multi-layer coating in accordance with example embodiments;

[0047] FIG. 2 shows a scanning electron microscope SEM) cross-section of an applied multi-layer coating in accordance with example embodiments;

[0048] FIG. 3 shows a cross-section of an applied multi-layer coating subjected to testing viewed via scanning electron microscope (SEM), in accordance with example embodiments;

[0049] FIG. 4 describes the coating system used in the coating layer of FIG. 3;

[0050] FIG. 5 shows the parameters used to spray the coating system of FIG. 4; and

[0051] FIG. 6 shows a cross-section of the applied multi-layer coating illustrated in FIG. 3 after the application of a 900 plus cycle test, in accordance with example embodiments.

DETAILED DESCRIPTION

[0052] Through one or more of its various aspects, embodiments and/or specific features or sub-components of the present disclosure, are intended to bring out one or more of the advantages as specifically described above and noted below.

[0053] FIG. 1 schematically shows a multi-layer coating in accordance with example embodiments. FIG. 1 schematically illustrates a multi-layer coating arrangement arranged 101/102 on a substrate 104 such as, e.g., a CMC substrate 104. As illustrated in FIG. 1, the multi-layer coating arrangement 101/102 includes one or more top coating layers 101 that are or include one or more strain-tolerant DVC coatings. In example embodiments, the one or more top coating layers 101 are provided on an underlying combination of an EBC layer 102 and a CMC substrate 104. The one or more top coating layers 101 may include one or more DVC layers 101, and may be composed of ZrO.sub.2 or HfO.sub.2 stabilized with a rare earth oxide (RE.sub.2O.sub.3) mixed with a CMAS-resistant chemical composition. In example embodiments, the one or more top coating layers 101 may provide erosion and water vapor corrosion resistance. In further example embodiments, one of the one or more top coating layers 101 is deposited directly on the EBC layer 102. In other example embodiments, the one or more DVC layers 101 has a sufficient strain-tolerant microstructure that can tolerate large amount of expansion and/or contraction during thermal cycling.

[0054] In example embodiments, the one or more top coating layers 101 may be composed of RE-stabilized ZrO.sub.2 or RE-stabilized HfO.sub.2 mixed with CMAS-resistant chemistry to improve the erosion- and CMAS-resistance of the EBC/CMC 102/104 combination.

[0055] Example embodiments of the one or more top coating layers 101, with the DVC being erosion, water vapor corrosion-, and CMAS-resistant, include the following (with exemplary rare earth oxides including Yttrium Oxide, Lanthanum Oxide, Cerium Oxide, Praseodymium Oxide, Neodymium Oxide, Samarium Oxide, Europium Oxide, Gadolinium Oxide, Terbium Oxide, Dysprosium Oxide, Holmium Oxide, Erbium Oxide, Ytterbium Oxide, Lutetium Oxide, Scandium Oxide, Thulium Oxide):

[0056] RE-stabilized ZrO.sub.2 or RE-stabilized HfO.sub.2; or

[0057] RE-stabilized ZrO.sub.2 or RE-stabilized HfO.sub.2 mixture with Rare earth oxides; or

[0058] RE-stabilized ZrO.sub.2 or RE-stabilized HfO.sub.2 mixture with Rare earth Silicate; or

[0059] RE-stabilized ZrO.sub.2 or RE-stabilized HfO.sub.2 mixture with Rare earth Aluminate; or

[0060] RE-stabilized ZrO.sub.2 or RE-stabilized HfO.sub.2 mixture with Rare earth Aluminate Silicate; or

[0061] RE-stabilized ZrO.sub.2 or RE-stabilized HfO.sub.2 mixture with alkaline oxides; or

[0062] RE-stabilized ZrO.sub.2 or RE-stabilized HfO.sub.2 mixture with Gadolinium Zirconate; or

[0063] Rare earth silicates; or

[0064] Any combination of the above.

[0065] In example embodiments, the one or more RE-stabilized may have a CTE of 10×10.sup.−6/° C., as well as a thickness of between 2 mils and 40 mils. The one or more RE-stabilized may be applied by atmospheric plasma spraying (APS), plasma spray physical vapor deposition (PS-PVD), or suspension plasma spray (SPS).

[0066] In example embodiments, the EBC layer 102 may include one or more EBC layer(s) or coating 102, and may have a CTE of 3.5-7×10.sup.−6/° C., as well as a thickness of between 1 mil and 40 mils. This EBC layer 102 may be applied by a plurality of methods such as, e.g., atmospheric plasma spraying (APS), plasma spray physical vapor deposition (PS-PVD), or suspension plasma spray (SPS).

[0067] In example embodiments, one or more bond coating layers 103 may be provided between the EBC layer 102 and the CMC substrate 104. In other example embodiments, the one or more bond coating layers 103 may be or include Si, Silicide, Si—HfO.sub.2, and/or Si-RE, and may have a CTE of 3.5-6×10.sup.−6/° C., as well as a thickness of between 0 mils (no bond coating layer) and 10 mils. The one or more bond coating layers 103 may be applied via a plurality of methods such as, e.g., atmospheric plasma spraying (APS), plasma spray physical vapor deposition (PVD), or suspension plasma spray (SPS).

[0068] In example embodiments, the CMC substrate 104 may have a CTE of ˜4.5-5.5×10.sup.−6/° C., as well as a thickness of greater than 40 mils. The CMC substrate may be or include SiC or Si.sub.3N.sub.4.

[0069] In example embodiments, the porosity of the one or more top coating layers 101 may be less than 5%, and the cracks may extend either partially through the thickness of the top coating layers 101, i.e., less than 50% of the thickness, or about 50% of the thickness of the thickness of the top coating layers 101, and may extend through an entire thickness of the top coating layers 101. In other example embodiments, the cracks may be substantially vertical cracks and may range in density between 20 and 200 cracks per inch.

EXAMPLES

[0070] FIG. 2 shows a scanning electron microscope (SEM) cross-section of an applied multi-layer coating in accordance with example embodiments. In FIG. 2, the topcoat DVC layer also includes a thermal barrier coating (TBC), and is deposited directly onto the dense EBC. FIG. 2 illustrates the cracks that extend vertically form the outside surface of the DVC inwards.

[0071] FIG. 3 shows a scanning electron microscope (SEM) cross-section of an applied multi-layer coating that was subjected to testing, in accordance with example embodiments. In FIG. 3, the top DVC layer 301 includes vertically oriented cracks 302, and is coated on the EBC 303. In example embodiments, the EBC 303 is coated on a substrate 304 such as, e.g., a CMC.

[0072] FIG. 4 describes the coating system used in the coating layer of FIG. 3. In FIG. 4, the substrate is SiC and has a thickness of about 2 mm, a bond coat is present and is a Si layer with a thickness of about 200 μm, the EBC layer is Yb.sub.2Si.sub.2O.sub.7 with a thickness of about 160 μm, and the DVC is Gd.sub.2Zr.sub.2O.sub.7 with a thickness of about 200 μm. In example embodiments, the process used to form the above coatings is an Ar/H.sub.2 plasma gas.

[0073] FIG. 5 describes the atmospheric plasma spraying (APS) parameters used to spray the coating system of FIG. 4. In example embodiments, the APS parameters for the bond coat layer include a gun current of 450 amps, a voltage of 90 volts, a gun power of 44 kW, an Argon flow of 75 nlpm (normal liter per minute), a hydrogen flow of 5 nlpm, and a powder feed rate of 20 g/min. In example embodiments, the APS parameters for the EBC layer include a gun current of 500 amps, a voltage of 91 volts, a gun power of 46 kW, an Argon flow of 70 nlpm, a hydrogen flow of 5 nlpm, and a powder feed rate of 20 g/min. In example embodiments, the APS parameters for the deposition of the DVC layer include a gun current of 500 amps, a voltage of 91 volts, a gun power of 46 kW, an Argon flow of 70 nlpm, a hydrogen flow of 5 nlpm, and a powder feed rate of 30 g/min.

[0074] FIG. 6 illustrates the coating of FIG. 3 after having undergone a 900-plus cycle test, and illustrates the coating microstructure having a separation between the DVC top layer 601 and the EBC 602 at interface 603 after 900 cycles at a temperature of 1316° C. The furnace cycle test (FCT) protocol used is as follows: the samples are heated up from room temperature to 1316° C. in 10 minutes, maintained at this 1316° C. temperature for 40 minutes, and then cooled to room temperature in 10 minutes. After 900 cycles, the coating did not exhibit spall. However, the cross section illustrated in FIG. 6 shows that the topcoat (DVC) started to delaminate but did not spall. As such, the sample underwent 900 cycles or more without exhibiting spall.

[0075] The following patent and publications includes references that are incorporated herein in their entirety by reference: U.S. Pat. Nos. 8,197,950; 5,073,433; US 2014/0178632; U.S. Pat. Nos. 5,830,586; 6,703,137; 6,177,200; 7,875,370; US 2012/0034491; U.S. Pat. Nos. 9,023,486; US 2016/0348226; U.S. Pat. Nos. 6,296,941; 6,284,325; 6,387,456; 6,733,908; 7,740,960; US 2010/0158680; U.S. Pat. No. 7,910,172; US 2016/0215631; US 2016/0017749; US 2014/0272197; US 2014/0065438; US 2014/0272197; and US 2013/0344319.

[0076] Further, at least because the invention is disclosed herein in a manner that enables one to make and use the same, by virtue of the disclosure of particular exemplary embodiments, such as for simplicity or efficiency, for example, the invention may be practiced in the absence of any additional element or additional structure that is not specifically disclosed herein.

[0077] 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.