METHOD FOR COATING A SURFACE OF A SOLID SUBSTRATE WITH A LAYER COMPRISING A CERAMIC COMPOUND, AND COATED SUBSTRATE THUS OBTAINED

Abstract

A method for coating at least one surface of a solid substrate with at least one layer comprising at least one ceramic compound by a suspension plasma spraying (SPS) technique, in which at least one suspension of solid particles of at least one ceramic compound is injected into a plasma jet, and then the thermal jet that contains the solid particle suspension is sprayed onto the surface of the substrate, by way of which the layer comprising at least one ceramic compound is formed on the surface of the substrate; method characterised in that, in the suspension, at least 90 vol % of the solid particles have a larger dimension (referred to as d.sub.90), such as a diameter, smaller than 15 m, preferably smaller than 10 m, and at least 50 vol % of the solid particles have a larger dimension, such as a diameter (referred to as d.sub.50), no smaller than 1 m. A substrate coated with at least one layer that can be obtained by the method. A part comprising the coated substrate and use of the layer in order to protect a solid substrate against degradations caused by contaminants such as CMAS.

Claims

1-25. (canceled)

26. Method for coating at least one surface of a solid substrate with at least one layer comprising at least one ceramic compound by a Suspension Plasma Spraying (SPS) technique in which at least one suspension of solid particles of at least one ceramic compound is injected in a plasma jet and then the thermal jet containing the suspension of solid particles is sprayed onto the surface of the substrate, whereby the layer comprising at least one ceramic compound is formed on the surface of the substrate; method characterized in that in the suspension, at least 90% by volume of the solid particles have a largest dimension (called d.sub.90), such as a diameter, less than 15 m, preferably less than 10 m, and at least 50% by volume of the solid particles have a largest dimension (called d.sub.50) such as a diameter, greater than or equal to 1 m; method further characterized in that the ceramic compound is selected from compounds known as anti-CMAS compounds, selected from rare earths zirconates of formula RE.sub.2Zr.sub.2O.sub.7, where RE is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Yb, Dy, Ho, Er, Tm, Tb, or Lu, hexa-aluminates, aluminium silicates, yttrium silicates of yttrium or of other rare earths silicates, which silicates may be doped with one or more alkaline earth metal oxides, and mixtures thereof; preferably, the ceramic compound is Gd.sub.2Zr.sub.2O.sub.7.

27. Method according to claim 26, wherein the layer has a lamellar microstructure and a tortuous porous network.

28. Method according to claim 27, wherein the layer comprises at the same time: lamellae resulting from the melting of the solid particles of the suspension, solid particles resulting from the partial melting of the solid particles of the suspension, and unmelted solid particles of the suspension.

29. Method according to claim 26, wherein the layer has a porosity of 5 to 50% by volume, preferably 5 to 20% by volume.

30. Method according to claim 26, wherein the layer has a thickness of 10 m to 1000 m, preferably 10 m to 300 m.

31. Method according to claim 26, wherein the solid substrate consists of a solid support, which is, for example, in the form of a massive support or in the form of a layer, and the layer comprising at least one ceramic compound is deposited directly on at least one surface of said support.

32. Method according to claim 26, wherein the solid substrate consists of a solid support on which there is a single layer or a stack of several layers, and the layer comprising at least one ceramic compound is deposited on at least one surface of said single layer, or on at least one surface of the upper layer of said stack of layers.

33. Method according to claim 31, wherein the support is made of a material selected from materials sensitive to an infiltration and/or an attack by contaminants such as CMAS; in particular the support is made of a material chosen from metals, metal alloys such as superalloys, preferably monocrystalline superalloys, ceramic matrix composites (CMC) such as SiC matrix composites, CSiC mixed matrix composites, and combinations and mixtures of the aforementioned materials.

34. Method according to claim 32, wherein the single layer or said stack of layers on the support forms a monolayer or multilayer thermal protection coating on the support, namely a thermal barrier system, and/or a monolayer or coating for protection against corrosive environments, namely an environmental barrier system.

35. Method according to claim 32, wherein the single layer is selected from bonding layers, and thermal or environmental barrier layers, such as layers, in particular ceramic layers which are thermally insulating layers, and layers, in particular ceramic layers which are anti-oxidation layers, and layers, in particular ceramic layers, which are anti-corrosion layers.

36. Method according to claim 32, wherein the stack of several layers on the support comprises, starting from the support: a bonding layer which covers the support; one or more layers chosen from among thermal barrier layers and environmental barrier layers, such as layers, in particular ceramic layers, which are thermally insulating layers, and layers, in particular ceramic layers, which are anti-oxidation layers, and layers, in particular ceramic layers, which are anti-corrosion layers; or the stack of several layers on the support comprises: several layers chosen from among thermal barrier layers and environmental barrier layers, such as layers, in particular ceramic layers, which are thermally insulating layers, layers, in particular ceramic layers, which are anti-oxidation layers, and layers, in particular ceramic layers, which are anti corrosion layers.

37. Method according to claim 35, wherein the thermal barrier layers and the environmental barrier layers, such as layers, in particular ceramic layers, which are thermally insulating layers, layers, in particular ceramic layers, which are anti-oxidation layers, and layers, in particular ceramic layers, which are anti-corrosion layers, are layers prepared by a technique chosen from among EB-PVD, APS, SPS, SPPS, sol-gel, PVD, CVD techniques, and the combinations of these techniques.

38. Method according to any one of claim 35, in which the thermal barrier layers are made of a material chosen from zirconium or hafnium oxides, stabilized with yttrium oxide or with other rare earths oxides, aluminium silicates, silicates or other rare earths silicates, wherein these silicates may be doped with alkaline earth metal oxides, and rare earths zirconates, which crystallize in a pyrochlore structure, and combinations and/or mixtures of the aforementioned materials, preferably the thermal barrier layers, are made of yttrium-stabilized zirconia (YSZ); and the environmental barrier layers are made of a material selected from aluminium silicates, optionally doped with alkaline earth elements, rare earth silicates, and combinations and/or mixtures of the aforementioned materials.

39. Method according to claim 35, wherein the bonding layer is made of a material selected from metals, metal alloys such as -NiAl metal alloys, modified or not with Pt, Hf, Zr, Y, Si or combinations of these elements, -Ni--Ni.sub.3Al metal alloys modified or not by Pt, Cr, Hf, Zr, Y, Si or combinations of these elements, MCrAlY alloys where M is Ni, Co, NiCo, Si, SiC, SiO.sub.2, mullite, BSAS, and combinations and/or mixtures of the aforementioned materials.

40. Method according to claim 26, wherein the substrate consists of a support made of a metal alloy such as a superalloy or a Ceramic Matrix Composite (CMC), coated with a metal bonding layer that is itself coated with a layer, such as a ceramic layer selected from the thermal barrier layers and the environmental barrier layers.

41. Method according to claim 26, wherein the substrate consists of a support made of a metal alloy such as a superalloy or consists of a Ceramic Matrix Composite (CMC) coated with a metal bonding layer that is itself coated with a thermal barrier ceramic layer made of yttrine (Y.sub.2O.sub.3)-stabilized zirconia (ZrO.sub.2).

42. Method according to claim 26, wherein the substrate consists of a support made of a metal alloy such as a superalloy or a Ceramic Matrix Composite (CMC), coated with a metal bonding layer that is itself coated with a thermal and/or environmental barrier ceramic layer produced by a technique selected from the APS, EB-PVD, SPS, SPPS, sol-gel, CVD techniques, and combinations of these techniques.

43. Substrate coated with at least one layer obtainable by the method according to claim 26.

44. Substrate according to claim 43, wherein the layer has a lamellar microstructure and a tortuous porous network.

45. Substrate according to claim 43, wherein the layer comprises at the same time: lamellae resulting from the melting of the solid particles of the suspension, solid particles resulting from the partial melting of the solid particles of the suspension, and unmelted solid particles of the suspension.

46. Substrate according to claim 43, wherein the layer has a porosity of 5 to 50% by volume, preferably 5 to 20% by volume.

47. Substrate according to claim 43, wherein the layer has a thickness of 10 m to 1000 preferably 10 m to 300 m.

48. Part comprising the coated substrate according to claim 44.

49. Part according to claim 48 which is a part of a turbine, such as a turbine blade, a distributor, a turbine ring, shroud or a part of a combustion chamber, or a part of a nozzle, or more generally any part subjected to attacks by liquid and/or solid contaminants such as CMAS.

50. Use of the layer obtainable by the method according to claim 26, for protecting a solid substrate against degradation caused by contaminants such as CMAS.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0122] FIG. 1 is a schematic sectional side view which shows a multilayer system whose top layer is an anti-CMAS layer 1 according to the invention, which is obtained by the method according to the invention implementing the SPS technique. with initial particles having a d.sub.90 less than 10 m and a d.sub.50 greater than or equal to 1 m.

[0123] FIG. 2 is a schematic sectional side view which shows in a simplified manner the multilayer system represented in FIG. 1, and the upper layer of which is an anti-CMAS layer 1 according to the invention and that is obtained by the method according to the invention implementing the SPS technique with initial particles having a d.sub.90 less than 15 m, preferably less than 10 m, and a d.sub.50 greater than or equal to 1 m.

[0124] FIG. 3 shows a micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons of a polished section of the sample prepared in example 1, which comprises an anti-CMAS layer 1 obtained by SPS with initial particles having a d.sub.90 less than 10 m and a d.sub.50 greater than or equal to 1 m made on the surface of a porous columnar YSZ layer 6 obtained by SPS.

[0125] The scale shown in FIG. 3 represents 100 m.

[0126] FIG. 4 shows a micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons of a polished section of the sample prepared in Example 2, which comprises an anti-CMAS layer 1 obtained by SPS with initial particles. having a d.sub.90 less than 10 m and a d.sub.50 greater than or equal to 1 m, and made on the surface of a porous compact columnar YSZ layer 7 obtained by SPS. The scale shown in FIG. 4 represents 100 m.

[0127] FIG. 5 shows a micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons of a polished section of the sample prepared in Example 3, which comprises an anti-CMAS layer 1 obtained by SPS with initial particles having a d.sub.90 less than 10 m and a d.sub.50 greater than or equal to 1 m, and made on the surface of a columnar YSZ layer 8 obtained by EB-PVD.

[0128] The scale shown in FIG. 5 represents 100 m.

[0129] FIG. 6 shows a micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons of a polished section of the anti-CMAS layer 1 obtained by SPS in Example 3 on the surface of a columnar YSZ layer 8 obtained by EB-PVD.

[0130] The observation is performed after CMAS infiltration.

[0131] The scale shown in FIG. 6 represents 5 m.

[0132] FIG. 7A shows a micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons, and FIG. 7B shows an Energy Dispersive Spectroscopy (EDS) analysis of the silicon of a polished section of the anti-CMAS layer 1 (similar to the layer 13 of FIG. 9A) obtained by SPS in Example 4 at the surface of an YSZ layer 11 obtained by APS. The observation is performed after CMAS infiltration.

[0133] The scale shown in FIGS. 7A and 7B represents 25 m.

[0134] FIG. 8A shows another micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons, and FIG. 8B shows an EDS analysis of the silicon of a polished section of the anti-CMAS layer 1 (similar to layer 13 in FIG. 9A) according to the invention, obtained by SPS in Example 4 at the surface of a YSZ layer 11 obtained by APS.

[0135] The observation is performed in an area with a cracking 12 after CMAS infiltration.

[0136] The scale shown in FIGS. 8A and 8B represents 25 m.

[0137] FIG. 9A shows yet another micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons and an EDS analysis of the silicon of a polished section of an anti-CMAS layer 13 of Gd.sub.2Zr.sub.2O.sub.7 obtained in Example 4, by SPS, with initial particles having a d.sub.90 of 7 m and a d.sub.50 of 3 m. This layer is made on the surface of a YSZ layer 11 obtained by APS.

[0138] The scale shown in FIG. 9A represents 25 m.

[0139] The observation is performed in an area with cracking after CMAS infiltration.

[0140] FIG. 9B shows a micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons (left) and an EDS analysis of the silicon (right) of a polished section of an anti-CMAS layer 14 of Gd.sub.2Zr.sub.2O.sub.7 according to the invention, and obtained in Example 5, by SPS, with initial particles having a diameter of 4.95 m and a d.sub.50 of 1.01 m, on the surface of a YSZ layer 11 obtained by APS.

[0141] The observation is carried out in a zone exhibiting cracking after CMAS infiltration.

[0142] The scale shown in FIG. 9B represents 25 m.

[0143] FIG. 9C shows a micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons and an EDS analysis of the silicon of a polished section of the anti-CMAS layer 15 of Gd.sub.2Zr.sub.2O.sub.7 obtained in Example 6, which does not conform to the invention by SPS, with initial particles having a d.sub.90 of 0.89 m and a d.sub.50 of 0.41 m. This layer is made on the surface of a YSZ layer 11 obtained by APS. The observation is performed in an area with cracking after CMAS infiltration.

[0144] The scale shown in FIG. 9C represents 25 m.

[0145] FIG. 10 shows a diffractogram obtained in X-ray diffraction after CMAS infiltration of the anti-CMAS layer 13 obtained in Example 4.

[0146] FIG. 11 shows a micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons of a polished section of the sample prepared in Example 11. This sample comprises an anti-CMAS layer consisting of Gd.sub.2Zr.sub.2O.sub.7 prepared at the surface of a YSZ layer 8, columnar, obtained by an EB-PVD method. The anti-CMAS layer is prepared in accordance with the invention by an SPS method using a suspension containing initial particles having a d.sub.90 of 13.2 m and a d.sub.50 greater than or equal to 1 m, namely 5.5 m.

[0147] The scale shown in FIG. 11 represents 100 m.

[0148] FIG. 12 shows a micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons of a polished section of the anti-CMAS layer 21 obtained by SPS in example 12 on a self-supporting substrate 11 made of yttria-stabilized zirconia in a phase t and obtained by APS.

[0149] The observation is performed after CMAS infiltration (Example 13).

[0150] The scale shown in FIG. 12 represents 100 m.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

[0151] FIG. 1 shows an embodiment of the method according to the invention, in which the layer according to the invention prepared by the method according to the invention, 1, is deposited on the surface of a system comprising the layers 2, 3, 4, shown in FIG. 1.

[0152] The various layers of the stack 2, 3, 4 may represent, by way of example but not exclusively, the layers of a thermal barrier system applied to superalloy aeronautical parts.

[0153] Advantageously, the layer 2 may be made of a material chosen from the materials of thermal barrier systems and/or environmental barrier systems such as, for example, zirconia (ZrO.sub.2) and/or yttrine (Y.sub.2O.sub.3) allowing a stabilization of the phase t, and all other suitable materials, as well as combinations and/or mixtures of these materials.

[0154] In addition, advantageously, the layer 2 may be produced by a deposition method, technique, chosen from among the EB-PVD, APS, SPS, SPPS, sol-gel and CVD methods, and all the other methods capable of producing this layer, as well as combinations of these methods.

[0155] Advantageously, the layer 2 has a microstructure that is characteristic of the deposition method, technique used. This layer may, for example, non-exclusively present a columnar microstructure, a columnar and porous microstructure, a compact and porous columnar microstructure, a homogeneous microstructructure, a homogeneous and porous microstructructure, a dense microstructure, a dense and vertically cracked microstructructure, a porous and vertically cracked microstructructure.

[0156] According to a first embodiment, the layer 1 according to the invention may be applied to a layer 2 having a porous columnar microstructure obtained by SPS (layer 6 in FIG. 3).

[0157] According to a second embodiment, the layer 1 according to the invention may be applied to a layer 2 having a porous compact columnar microstructure obtained by SPS (layer 7 in FIG. 4).

[0158] According to a third embodiment, the layer 1 according to the invention may be applied to a layer 2 having a columnar microstructure obtained by EB-PVD (layer 8 in FIG. 5).

[0159] Advantageously, the layer 2 may have a function of a thermal barrier and/or an environmental barrier. This layer also allows, but not exclusively, the guarantee of good performances in terms of lifetime and thermal insulation or protection against oxidation and humid corrosion.

[0160] Advantageously, the layer 3 serves as a bonding layer.

[0161] The layer 3 may be made of a material chosen from metals, metal alloys such as -NiAl metal alloys (modified or not modified by Pt, Hf, Zr, Y, Si or combinations of these elements), aluminides of -Ni--Ni.sub.3Al alloy (modified or otherwise by Pt, Cr, Hf, Zr, Y, Si or combinations of these elements), the alloys MCrAlY (where M=Ni, Co, NiCo), the Si, SiC, SiO.sub.2, mullite, BSAS, and all other suitable materials, as well as combinations and/or mixtures of these materials.

[0162] Advantageously, the layer 3 may comprise an oxide layer obtained by oxidation of the elements of the layer 3, as described above. For example, but not exclusively, the layer 3 may be an alumino-forming layer, i.e. the oxidation of the layer 3 may advantageously produce an -alumina layer.

[0163] Advantageously, the layer 4 is part of a part or of an element of a part made of a material chosen from metal alloys, such as metal superalloys, ceramic matrix composites (CMC), and combinations and/or mixtures of these materials. The material of the layer 4 may in particular be chosen from AM1, Rene, and CMSX-4 superalloys.

[0164] In FIG. 2, the layer 1, and the system comprising the layers 2, 3, 4, shown in FIG. 1 are simplified to two elements, namely: [0165] an anti-CMAS layer 1 according to the invention obtained by the method according to the invention implementing the SPS technique with particles of the injected suspension having a d.sub.90 of less than 10 m and a d.sub.50 greater than or equal to 1 m; [0166] a layer 5 which may exactly describe the system of the layers 2, 3, 4 of FIG. 1, or one or more layers of the system of the layers 2, 3, 4 of FIG. 1, or one or more combinations of layers of the system of layers 2, 3, 4 of FIG. 1. This system is coated with an anti-CMAS layer 1 obtained by SPS with injected particles having a d.sub.90 less than 15 m, preferably less than 10 m, and a d.sub.50 greater than or equal to 1 m.

[0167] Thus, advantageously, the layer 1 according to the invention may be applied to the surface of a layer 5. This layer 5 may include in an independent and/or combined way layers 2, 3, 4.

[0168] Advantageously, the layers 2 and 3 and/or the layer 5 allow, but not exclusively, the provision of a thermal and/or environmental barrier function. They also allow, but not exclusively, the guarantee of good performance in terms of service lifetime and thermal insulation or protection against oxidation and humid corrosion. Advantageously, the addition of the layer 1 according to the invention does not degrade the performance of the systems, described in FIGS. 1 and 2, on which it is applied.

[0169] Advantageously, the microstructure of the layer 1 has a homogeneous and/or cracked morphology, but not exclusively, whether it is carried out on the layer 2 or the layer 5, and whatever the microstructure and/or the composition of the layer 2 or layer 5.

[0170] Advantageously, the layer 1 according to the invention reacts with CMAS at high temperature, more precisely at a temperature above the melting temperature of CMAS, to form a reactive zone 9 (FIG. 6) beyond which CMAS penetration within layer 1 is stopped and/or limited.

[0171] Finally, the solidified CMAS 10 are thus observed on the surface of the coating (see examples, FIG. 6).

[0172] Advantageously, zone 9 is composed of reaction products between CMAS and layer 1 including, but not exclusively, apatite and/or anorthite and/or zirconia and/or other reaction products phases and/or combinations and/or mixtures of these phases.

[0173] For example, no CMAS infiltration within the layer 1 deposited on a layer 11 obtained by APS is observed after a CMAS infiltration test beyond the reaction zone 9 (FIGS. 7A and 7B). Advantageously, the layer 11 obtained by APS is included in the description of the layer 2 described in FIG. 1.

[0174] Similarly, no CMAS infiltration within layer 1 deposited on a layer 11 is obtained by APS after a CMAS infiltration test beyond reaction zone 9 (FIGS. 8A and 8B). The crack 12 observed within layer 1 deposited on a layer 11 obtained by APS, is rapidly clogged by reaction products similar to those composing zone 9 (FIGS. 8A and 8B). Advantageously, the layer 11 obtained by APS is included in the description of the layer 2 described in FIG. 1.

[0175] It should be noted that, when a layer 1 according to the invention is produced by the method according to the invention, it is possible before coating the substrate (including layers 2 to 4 of FIG. 1 and/or layer 5 of FIG. 2) by the layer 1, to prepare and/or clean the surface to be coated in order to eliminate residues and/or contaminants (inorganic and/or organic) which would be prone to prevent the deposition and/or to degrade the adhesion and/or to affect the microstructure. The surface preparation may be the formation of a surface roughness by sanding, the oxidation of the substrate to generate a thin oxide layer and/or a combination of these preparation methods.

[0176] The invention will now be described with reference to the following examples, given by way of illustration but not limitation.

[0177] To prepare the anti-CMAS layers, suspensions of ceramic particles in ethanol are first prepared by placing ceramic particles in suspension in ethanol to obtain suspensions having a ceramic concentration of 12% by mass.

[0178] The suspensions thus prepared are then injected into a blown arc plasma using an assembly consisting of:

[0179] an Oerlikon-Metco F4-VB and/or Oerlikon-Metco Triplex Direct Current Pro200 plasma torch; [0180] a robotic device on which the torch is placed and which allows its movement; [0181] a device for fixing the surface to be coated at a defined distance from the torch. The combination of the movement authorized by this device and that of the preceding device makes it possible to coat the surface of a sample; [0182] a suspension injection device.

[0183] In Examples 1, 2, 3, and 4, the layer is made with an Oerlikon-Metco Triplex Pro200 torch, with a distance of 70 mm between the torch outlet and the substrate, using a plasma-forming gas mixture consisting of 80% by volume of argon and 20% by volume of helium.

[0184] In Example 5, the layer is made with an Oerlikon-Metco Triplex Pro200 torch, with a distance of 60 mm between the torch outlet and the substrate, using a plasma-forming gas mixture consisting of 80% by volume of argon and 20% by volume of helium.

[0185] In Example 6, the layer is made with an Oerlikon-Metco type F4-VB torch, with a distance of 50 mm between the torch outlet and the substrate, using a plasma-forming gas mixture consisting of 62% by volume of argon and 38% by volume of helium.

EXAMPLES

Example 1

[0186] In this example, an anti-CMAS layer according to the invention is prepared by the method according to the invention (see FIG. 3).

[0187] The anti-CMAS layer 1, consisting of Gd.sub.2Zr.sub.2O.sub.7, is prepared on the surface of a porous, columnar YSZ layer 6, obtained by an SPS method. The anti-CMAS layer is prepared by an SPS method using a suspension containing initial particles having a d.sub.90 of less than 10 m, namely a d.sub.90 of 7 m, and a d.sub.50 greater than or equal to 1 m, namely 3 m.

[0188] The thus prepared sample constituted by the anti-CMAS layer on the substrate falls within the scope of the system shown in FIGS. 1 and 2.

[0189] FIG. 3 shows a Scanning Electron Microscope (SEM) micrograph using backscattered electrons of a polished section of the sample prepared in this example.

Example 2

[0190] In this example, an anti-CMAS layer according to the invention is prepared by the method according to the invention.

[0191] The anti-CMAS layer 1 consisting of Gd.sub.2Zr.sub.2O.sub.7 is prepared on the surface of a columnar, compact, porous YSZ layer 7 obtained by an SPS method. The anti-CMAS layer is prepared by an SPS method using a suspension containing initial particles having a d.sub.90 of less than 10 m, namely a d.sub.90 of 7 m, and a d.sub.50 greater than or equal to 1 m, namely 3 m.

[0192] The thus prepared sample constituted by the anti-CMAS layer on the substrate falls within the scope of the system shown in FIGS. 1 and 2.

[0193] FIG. 4 shows a Scanning Electron Microscope (SEM) micrograph using backscattered electrons of a polished section of the sample prepared in this example.

Example 3

[0194] In this example, an anti-CMAS layer according to the invention is prepared by the method according to the invention.

[0195] The anti-CMAS layer 1 consisting of Gd.sub.2Zr.sub.2O.sub.7 is prepared on the surface of a YSZ columnar layer 8 that is obtained by an EB-PVD method. The anti-CMAS layer is prepared by an SPS method using a suspension containing initial particles having a d.sub.90 of less than 10 m, namely a d.sub.90 of 7 m, and a d.sub.50 greater than or equal to 1 m, namely 3 m.

[0196] The thus prepared sample constituted by the anti-CMAS layer on the substrate falls within the scope of the system shown in FIGS. 1 and 2.

[0197] FIG. 5 shows a Scanning Electron Microscope (SEM) micrograph using backscattered electrons of a polished section of the sample prepared in this example.

Example 4

[0198] In this example, an anti-CMAS layer according to the invention is prepared by the method according to the invention (see FIG. 9A after infiltration by CMAS).

[0199] The anti-CMAS layer 13 consisting of Gd.sub.2Zr.sub.2O.sub.7 is obtained by SPS using a suspension containing particles of Gd.sub.2Zr.sub.2O.sub.7 having a d.sub.90 of 7 m and a d.sub.50 of 3 m. The layer is made on a self-supported substrate 11 made of yttria-stabilized zirconia stabilized in a phase t and obtained by APS.

Example 5

[0200] In this example, an anti-CMAS layer according to the invention is prepared by the method according to the invention (see FIG. 9B after infiltration by CMAS).

[0201] The anti-CMAS layer 14 consisting of Gd.sub.2Zr.sub.2O.sub.2 is obtained by SPS using a suspension containing Gd.sub.2Zr.sub.2O.sub.2 particles having a d.sub.90 of 4.95 m and a d.sub.50 of 1.01 m. The layer is made on a self-supporting substrate 11 of yttria-stabilized zirconia stabilized in a phase t and obtained by APS.

Example 6 (Comparative)

[0202] In this example, an anti-CMAS layer not according to the invention is prepared by a method which is not in accordance with the invention (see FIG. 9C after infiltration by CMAS).

[0203] The anti-CMAS layer 15 consisting of Gd.sub.2Zr.sub.2O.sub.2 is obtained by SPS using a suspension not according to the invention, containing particles of Gd.sub.2Zr.sub.2O.sub.2 having a d.sub.90 of 0.89 m and a d.sub.50 of 0.41 m. The layer is made on a self-supported substrate 11 made of zirconia stabilized in a phase t and obtained by APS.

[0204] In Examples 7 to 10 below, CMAS infiltration tests are carried out on the samples prepared in Examples 3 to 6.

[0205] In each of Examples 7 to 10, the CMAS (23.5% CaO15.0% Al.sub.2O.sub.361.5% SiO.sub.20% MgO (in weight %)) is deposited on the surface of each of the samples (30 mg/cm.sup.2). The sample is heated at 1250 C. for 1 hour.

[0206] At the end of the tests, each of the anti-CMAS layers has reacted and shows a drop of solidified CMAS on the surface of the sample.

[0207] At the end of the tests, a Scanning Electron Microscope (SEM) observation using backscattered electrons of a polished section of each of the samples was carried out.

[0208] For most samples, an Energy Dispersive Spectroscopy (EDS) analysis of the silicon of a polished section of the sample was also carried out.

Example 7

[0209] In this example, a CMAS infiltration test was carried out according to the protocol described above, on the sample prepared in Example 3, and the sample was observed after infiltration.

[0210] FIG. 6 shows a Scanning Electron Microscope (SEM) micrograph using backscattered electrons of a polished section of the anti-CMAS layer 1 obtained by SPS in Example 3 at the surface of a columnar YSZ layer 8 obtained by EB-PVD.

[0211] The observation made after infiltration by the CMAS reveals on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 1.

Example 8

[0212] In this example, a CMAS infiltration test is carried out according to the protocol described above, on the sample prepared in Example 4, and the sample is observed after infiltration of CMAS.

[0213] FIG. 7A shows a micrograph taken with Scanning Electron Microscope (SEM) using backscattered electrons, and FIG. 7B shows an Energy Dispersive Spectroscopy (EDS) analysis of silicon of a polished section of the anti-CMAS layer 1 (13) obtained by SPS in Example 4 on, at, the surface of a YSZ layer 11 obtained by APS.

[0214] The observation is made here in an uncracked area, without cracks, in which there was no infiltration.

[0215] The observation made after infiltration of CMAS reveals on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 1. The lighter zone on the EDS shot corresponds to either the solidified CMAS 10 or the reaction zone 9.

[0216] FIG. 8A shows another micrograph done with a Scanning Electron Microscope (SEM) using backscattered electrons, and FIG. 8B shows another EDS analysis of silicon of a polished section of the anti-CMAS layer 1 obtained by SPS in the Example 4 on the surface of a YSZ layer 11 obtained by APS.

[0217] The observation is made here in a zone having a crack 12 after CMAS infiltration and shows on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 1 (13). The lighter zone on the EDS shot corresponds either to the solidified CMAS 10 or to the reaction zone 9, or to the degree of penetration within the crack of the CMAS or of the reaction products between the CMAS and the layer 1.

[0218] FIG. 9A shows yet another micrograph taken with a Scanning Electron Microscope (SEM) using backscattered electrons (left) and an EDS analysis of silicon (right) of a polished section of an anti-CMAS layer 13 of Gd.sub.2Zr.sub.2O.sub.7 obtained in Example 4, by SPS, with initial particles having a d.sub.90 of 7 m and a d.sub.50 of 3 m. This layer is made on the surface of a YSZ layer 11 obtained by APS.

[0219] The observation is carried out in a zone having a crack after CMAS infiltration and reveals on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 13. The lighter zone on the EDS shot corresponds either to the solidified CMAS 10 or to the reaction zone 9, or to the degree of penetration within the crack of the CMAS, or of the reaction products between the CMAS and the layer 13.

[0220] FIG. 10 shows a diffractogram obtained by X-ray diffraction after CMAS infiltration of the anti-CMAS layer 13. The analysis shows the presence of the initial material Gd.sub.2Zr.sub.2O.sub.7, of an apatite phase Ca.sub.2Gd.sub.8(SiO.sub.4).sub.6O.sub.2, of an anorthite phase CaAl.sub.2(SiO.sub.4).sub.2 and of zirconia.

Example 9

[0221] In this example, a CMAS infiltration test is carried out according to the protocol described above, on the sample prepared in Example 5, and the sample is observed after infiltration.

[0222] FIG. 9B shows a micrograph taken with a Scanning Electron Microscope (SEM) using backscattered electrons (left) and a silicon EDS analysis (right) of a polished section of an anti-CMAS layer 14 of Gd.sub.2Zr.sub.2O.sub.7 obtained in Example 5, by SPS with initial particles having a diameter of 4.95 m and a d.sub.50 of 1.01 m.

[0223] This layer is made on the surface of a YSZ layer 11 obtained by APS. The observation is carried out in a zone having cracking after CMAS infiltration and shows on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 14. The lighter zone on the EDS shot corresponds either to the solidified CMAS 10 or to the reaction zone 9, or to the degree of penetration within the crack of CMAS, or of the reaction products between the CMAS and the layer 14.

Example 10 (Comparative)

[0224] In this example, a CMAS infiltration test is carried out according to the protocol described above, on the sample not according to the invention prepared in Example 6, and the sample is observed after infiltration.

[0225] FIG. 9C shows a micrograph taken with a Scanning Electron Microscope (SEM) using backscattered electrons (left) and a silicon EDS (right) analysis of a polished section of the anti-CMAS layer 15 of Gd.sub.2Zr.sub.2O.sub.7 obtained in Example 6, by SPS, with initial particles having a d.sub.90 of 0.89 m and a d.sub.50 of 0.41 m. This layer is made on the surface of a YSZ layer 11 obtained by APS. The observation is carried out in a zone having a crack after CMAS infiltration and shows on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 15. The lighter zone on the EDS shot corresponds either to the solidified CMAS 10 or to the reaction zone 9, or to the degree of penetration within the cracking of the CMAS, or of the reaction products between the CMAS and the layer 15.

Conclusion of Examples 1 to 10

[0226] Between the CMAS and the anti-CMAS layer, a reactive zone 9 composed of blocking phases is observed (FIG. 6, 7A, 7B, 8A, 8B, 9A, 9B, 9C).

[0227] The visualization of the CMAS and the reactive zone is also illustrated by the EDS shots shown in FIGS. 9A, 9B and 9C.

[0228] The phases present analyzed by X-ray diffraction comprise the initial material Gd.sub.2Zr.sub.2O.sub.7, an apatite phase Ca.sub.2Gd.sub.8(SiO.sub.4).sub.6O.sub.2, an anorthite phase CaAl.sub.2(SiO.sub.4).sub.2 and zirconia (FIG. 10).

[0229] Whether it is through the porosity of the coating or cracks, the reactive zone 9 as well as the CMAS penetration within the anti-CMAS layer becomes more significant and more severe as the particle sizes decrease.

[0230] In particular, the layer 15 of Example 6 (FIG. 9C), which does not conform to the invention, has a much larger, much more severe infiltration, than the layers 13 and 14 according to the invention (FIGS. 9A and 9B).

[0231] The size of the particles of anti-CMAS material injected into the plasma jet generates a difference in the morphology of the porosity. In fact, the smaller particles offer, in particular, the liquid CMAS a greater number of entry points, and more numerous and direct propagation paths in the thickness of the layer. Thus, in Example 6, not in accordance with the invention, small particles are used in the suspension, and there is then an infiltration of the coating by the CMAS in the thickness of the coating.

[0232] The kinetics of penetration within the coating is in competition with the kinetics of reaction allowing the formation of effective blocking phases.

[0233] In the layers prepared by the method according to the invention, the reaction kinetics of CMAS with the material of the layers is faster than the kinetics of infiltration, i.e. penetration, of the CMAS in the porosity of the layers. In fact, the layers according to the invention, because they are prepared with suspensions which have a large particle size, therefore have a high tortuosity, which slows down the kinetics of infiltration, i.e. penetration, of the CMAS. The kinetics of CMAS penetration into the layers prepared by the method according to the invention is far less rapid than the reaction kinetics of CMAS with the material of the layers which allows the formation of effective blocking phases.

[0234] The kinetics of penetration of the anti-CMAS layer by CMAS at high temperature is slowed down for initial particles having sizes according to the invention. In this case, the anti-CMAS layer makes it possible as a result of the high tortuosity generated, to form the blocking phase and/or the blocking phases at the surface and/or at a shallow depth within the anti-CMAS layer.

[0235] The lowest degree of infiltration, at the cracks or at the uncracked zones, is observed for the layer 13 of Example 4 according to the invention.

Example 11

[0236] In this example, an anti-CMAS layer according to the invention is prepared by the method according to the invention. The anti-CMAS layer 21 consisting of Gd.sub.2Zr.sub.2O.sub.7 is prepared on the surface of a columnar YSZ layer 8, obtained by an EB-PVD method.

[0237] The anti-CMAS layer is prepared by an SPS method using a suspension containing initial particles having a d.sub.90 of 13.2 m and a d.sub.50 greater than or equal to 1 m, namely 5.5 m.

[0238] The YSZ layer 8 is the same as the YSZ layer 8 of Example 3 but the layer 21 has a different particle size.

[0239] The thus prepared sample constituted by the anti-CMAS layer on the substrate falls within the scope of the system shown in FIGS. 1 and 2.

[0240] FIG. 11 shows a micrograph taken with a Scanning Electron Microscope (SEM) using backscattered electrons of a polished section of the sample prepared in this example.

Example 12

[0241] In this example, an anti-CMAS layer according to the invention is prepared by the method according to the invention (see FIG. 12 after infiltration by CMAS). The anti-CMAS layer 21 consisting of Gd.sub.2Zr.sub.2O.sub.7 is obtained by SPS using a suspension containing Gd.sub.2Zr.sub.2O.sub.7 particles having a d.sub.90 of 13.2 m and a d.sub.50 of 5.5 m. The layer is made on a self-supported substrate 11 made of yttria-stabilized zirconia stabilized in a phase t and obtained by APS.

Example 13

[0242] In this example, a CMAS infiltration test is carried out according to the protocol described above, on the sample prepared in Example 12, and the sample is observed after infiltration.

[0243] FIG. 12 shows a micrograph taken with a Scanning Electron Microscope (SEM) using backscattered electrons of a polished section of the anti-CMAS layer 21 obtained by SPS.

[0244] The observation is performed after infiltration by the CMAS, and reveals on the surface the solidified CMAS 10 and a reaction zone 9 comprising the reaction products between the CMAS and the layer 21.

REFERENCES

[0245] [1] A. Feuerstein, J. Knapp, T. Taylor, A. Ashary, A. Bolcavage, N. Hitchman, Technical and economical aspects of current thermal barrier coating systems for gas turbine engines by thermal spray and EBPVD: a review, Journal of Thermal Spray Technology, 17, 2008, 199-213. [0246] [2] N. Curry, K. Van Every, T. Snyder, N. Markocsan, Thermal conductivity analysis and lifetime testing of suspension plasma-sprayed thermal barrier coatings, Coatings, 4, 2014, pp 630-650. [0247] [3] E. H. Jordan, L. Xie, M. Gell, N. P. Padture, B. Cetegen, A. Ozturk, J. Roth, T. D. Xiao, P. E. C. Bryant, Superior thermal barrier coatings using solution precursor plasma spray, Journal of Thermal Spray Technology, 13, 2004, pp 57-65. [0248] [4] Z. Tang, H. Kim, I. Yaroslayski, G. Masindo, Z. Celler, D. Ellsworth, Novel thermal barrier coatings produced by axial suspension plasma spray, Proceeding of International Thermal Spray Conference and Exposition (ITSC), Hamburg, Germany, 2011. [0249] [5] K. N. Lee, US-2009/0184280-A1. [0250] [6] K. W. Schlichting, M. J. Maloney, D. A. Litton, M. Freling, J. G. Smeggil, D. B.

[0251] Snow, US-2010/0196605-A1. [0252] [7] B. Nagaraj, T. L. Few, T. P. McCaffrey, B. P. L'Heureux, US-2011/0151219-A1. [0253] [8] A. Meyer, H. Kassner, R. Vassen, D. Stoever, J. L Marques-Lopez, US-2011/0244216-A1. [0254] [9] B. T. Hazel, D. A. Litton, M. J. Maloney, US-2013/0260132-A1. [0255] [10] C. W. Strock, M. Maloney, D. A. Litton, B. J. Zimmerman, B. T. Hazel, US-2014/0065408-A1.