WO2013075202A1 - Method and apparatus for depositing stable crystalline phase coatings of high temperature ceramics - Google Patents
Method and apparatus for depositing stable crystalline phase coatings of high temperature ceramics Download PDFInfo
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- WO2013075202A1 WO2013075202A1 PCT/CA2011/001285 CA2011001285W WO2013075202A1 WO 2013075202 A1 WO2013075202 A1 WO 2013075202A1 CA 2011001285 W CA2011001285 W CA 2011001285W WO 2013075202 A1 WO2013075202 A1 WO 2013075202A1
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
- C04B41/4505—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements characterised by the method of application
- C04B41/4523—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements characterised by the method of application applied from the molten state ; Thermal spraying, e.g. plasma spraying
- C04B41/4527—Plasma spraying
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
- C04B41/81—Coating or impregnation
- C04B41/85—Coating or impregnation with inorganic materials
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
- C23C4/06—Metallic material
- C23C4/067—Metallic material containing free particles of non-metal elements, e.g. carbon, silicon, boron, phosphorus or arsenic
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
- C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
- C23C4/11—Oxides
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
- C23C4/134—Plasma spraying
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
- F01D5/12—Blades
- F01D5/28—Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
- F01D5/284—Selection of ceramic materials
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
- F01D5/12—Blades
- F01D5/28—Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
- F01D5/288—Protective coatings for blades
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- F05D2230/00—Manufacture
- F05D2230/30—Manufacture with deposition of material
- F05D2230/31—Layer deposition
- F05D2230/311—Layer deposition by torch or flame spraying
Definitions
- the present invention relates in general to thermal spray arts, and in particular to techniques for producing stable crystalline phase coatings of such materials as alkaline earth aluminosilicates (e.g., barium-strontium aluminosilicate (BSAS)), rare earth silicates (RESs), and mullites, and in particular to a low cost coating process that is phase pure, without assisted heating of a substrate.
- alkaline earth aluminosilicates e.g., barium-strontium aluminosilicate (BSAS)
- RESs rare earth silicates
- mullites e.g., a low cost coating process that is phase pure, without assisted heating of a substrate.
- Layered refractory oxide coatings offering a suitable thermal-insulation reduce the thermal gradient through the structural component and increase its durability.
- a coating for components formed of Si-based materials (CMCs) must simultaneously fulfill a second role namely environmental protection, like for instance, in the high temperature environments containing water vapour in the hot sections of gas turbines (e.g., blades, vanes and combustion chambers) or in low 0 2 atmospheric pressures at high altitudes for hypersonic aircraft.
- these coatings have been named environmental barrier coatings (EBCs), and they are expected to work at temperatures higher than 1300°C.
- a low permeability for oxidant species is a critical feature for an EBC system so as to inhibit the major degradation mechanism of the Si- based substrate that is formation of silicon hydroxide (Si(OH) 4 ) gas by the reaction of the water vapour originating from the jet fuel combustion with the Si0 2 scale formed on the Si-based substrate [1 , 2, 3, 4, 5].
- Si(OH) 4 silicon hydroxide
- the future hypersonic vehicles flying in low Earth orbit will also employ Si- based materials on its external body structure.
- Si-based materials For this type of application, a silicon monoxide (SiO) scale will tend to be formed on the surface of these Si-based materials due to the low 0 2 atmospheric pressures at high altitudes and the high temperatures caused by the friction with the atmosphere during ascending and re-entry.
- the SiO scale will tend to sublime under these conditions. Therefore, EBCs will be needed to protect the exposed structure of hypersonic aircraft [6].
- Thermal spraying is the state-of-the-art processing method to deposit EBCs on Si-based materials. All ceramics and cermets are not equally easy to apply by thermal spraying. Some are relatively simple: as long as the feedstock reaches a melting temperature during the spraying, and is accelerated to a speed within a given range, it can be deposited reasonably efficiently. Some are more complex in that overheating of the feedstock above a temperature far in excess of the melting point, leads to reactions between the feedstock and ambient gases that lead to impurities in the coating. But a large and growing class of materials that are desired to be thermally sprayed are quite challenging.
- BSAS Barium Strontium AluminoSilicate
- Bai -x SrxAI 2 Si 2 Os Bai -x SrxAI 2 Si 2 Os, 0 ⁇ x ⁇ 1
- AI 6 Si 2 Oi3 aluminosilicate muliite
- alkaline earth aluminosilicates like barium aluminosilicate (SAS) and strontium aluminosilicate (SAS) can also be applied as EBCs.
- RESs have also been studied and considered as potential candidates for EBC applications, including but not limiting: Y 2 Si0 5 , Er 2 Si0 2 , Yb 2 Si0 5i Lu 2 Si0 5 and Yb 2 Si 2 0 7 [7 ⁇ .
- BSAS and muliite are state-of-the-art materials thermal sprayed to produce EBCs.
- Thermal spraying is a group of processes wherein a feedstock material (usually in a powder, but also in the form of a wire or rod, or sometimes a precursor solution or suspension) is injected into a plume (typically a plasma or a combustion flame) of a thermal spray torch, where the feedstock is heated and propelled as a jet of individual molten or semi-molten particles, toward a substrate surface.
- the at least semimolten particles flatten and form think lamellae (splats) that conform and adhere to the irregular substrate/previous deposition, and/or to one another.
- the splats cool down very rapidly (10 5 -10 7 °C/s) and resolidify, generally before the arrival of the next splat, resulting in a distinctive lamellar structure.
- the atoms of the molten particles may not have enough time and/or energy (nucleation kinetics) to achieve their most desired stable crystalline form. It is very common for thermal sprayed coatings to include multiple crystalline, metastable and/or amorphic zones.
- the desire for pure Celsian (monoclinic) phase of BSAS is well known.
- the metastable Hexacelsian (hexagonal) phase is stable only within the temperature range of ⁇ 1600-1760°C, whereas, the Celsian phase is stable from room temperature up to ⁇ 1600°C.
- the coefficients of thermal expansion (CTEs) of the Hexacelsian phase ( ⁇ 8 x 10 '6 °C ⁇ 1 ), the Celsian phase ( ⁇ 5 x 10 " ⁇ "C "1 ), and a typical Si-based substrate (SiC, or S13 4) used in high temperature applications, is ⁇ 4-5 x 10 "6 °C 1 , attest to the compatibility of the Celsian phase with the substrate.
- mullite is known to form a mixture of amorphous and crystalline phases during regular thermal spray deposition, i.e., when the substrate temperature is kept below ⁇ 500°C. Mullite crystallizes at ⁇ 1000°C, leading to the cracking and failure of the coating (when operating at T ⁇ 1000°C) due to the lack of plasticity of this material. Therefore, it is known in the art to spray mullite in an oven at ⁇ 1000°C ([13][14]) which does provide highly crystalline mullite coatings, that exhibit excellent performance as intermediate layers in EBCs.
- US patent application 20 1 /0033630 to Naik et al. teaches deposition of BSAS on a mullite interlayer with the substrate at a temperature of less than 150°C when the BSAS is first deposited.
- This application teaches that the temperature of the substrate during deposition may be less than 200"C, i.e., (15-200°C or 20-150°C), presumably with forced cooling.
- the power of the torch, plasma gas flow rates, plasma constituents (especially the concentration of 2), and the stand-off between the plume is nowhere disclosed. As a result, it is impossible to reproduce, verify or compare coatings according to this invention.
- All air plasma spray (APS) torches are not created equal.
- a typical conventional plasma spray torch would be expected to have a power of 20-60 kW, and use Ar/Hi as plasma gases at total gas flow rates in the order of ⁇ 20-80 standard litres per minute (slpm).
- Other possible combination of plasma gases for these types of equipment operating at these ranges of power and total gas flow are Ar/N 2 , Ar/He, N2/H2, Nj/He, and on a lesser scale, a tertiary combination of thereof.
- a high enthalpy APS torch for thermal spray processing while generally providing the same mechanism, is typically designed for ⁇ 60- 50 kW power, -100-400 slpm total plasma gas flow delivery, and typically uses a tertiary plasma gas combination that includes N2.
- mullite is a lower crystallization temperature material than BSAS and other RESs, as the prior art all teaches low temperature amorphous thermal spray deposition, it follows that all of the problems with mullite will be as great or greater for BSAS. More recently, a paper to Harder et al. entitled Chemical and Mechanical Consequences of Environmental Barrier Coating Exposure to Calcium-Magnesium-Aluminosilicate J. Am. Ceram. Soc. 94 [S1] S178-S185 (2011), teaches: "In room-temperature plasma-sprayed systems, BSAS is deposited as an amorphous phase and crystallizes in the metastable Hexacelsian phase (hexagonal) when heated.
- Heating the substrate to 1200°C during the plasma-spray process is sufficient to deposit BSAS in the Hexacelsian phase.
- This Hexacelsian phase then undergoes a phase transformation at temperatures over 1200°C into the stable Celsian phase (monoclinic). This transformation is accompanied by a 0.5% volume reduction and drastically changes the elastic modulus and coefficient of thermal expansion (CTE) of the topcoat." Harder et ai.
- a faster and iower cost solution for producing coatings of a stable crystalline phase are in demand for coating ceramics for high temperature application, such as EBCs, especially for alkaline earth aluminosilicates (e.g., BSAS), RESs, and mullite.
- EBCs especially for alkaline earth aluminosilicates (e.g., BSAS), RESs, and mullite.
- BSAS alkaline earth aluminosilicates
- RESs alkaline earth aluminosilicates
- mullite e.g., mullite
- Applicant has found, contrary to what has been established in the prior art, that by 1 ) employing a high enthalpy APS torch, 2) using a fairly short stand-off distance, and 3) applying the coating in at least 3 passes, as-sprayed coatings of BSAS, mullite, and the like, can be deposited without assisted heating or cooling, and without heat treatment, to produce coatings with levels of a high-temperature stable crystalline phase that are higher than that possible in accordance with the prior art.
- a method of producing a high temperature coating on a ceramic substrate comprising: operating a high enthalpy plasma spray torch and supplying the torch with a feedstock powder comprising a high temperature ceramic with a melting point above 1600X, forming undesirable solid phases when rapidly cooled below about 900°C; and spraying the ceramic substrate with the torch in at least 3 passes to deposit the coating; wherein a stand off distance is maintained during the deposition such that a width of a bead produced from a single spray pass on the substrate at ⁇ 800°C is less than 70% of a diameter of a plume of the torch at the stand off, Doing so, the coating contains iess undesirable solid phase without requiring assisted heating, forced cooling or subsequent heat treatment.
- the substrate surface temperature centred on the plume during deposition preferably exceeds 1000°C because of the proximity of the torch, and the absence of assisted heating or forced cooling.
- Spraying the ceramic substrate with the torch in at least 3 passes may comprise moving a surface of the substrate to be coated in a direction perpendicular to the spray jet at a speed of 0.1-5 m/s.
- the stand-off distance may be chosen where the width of a single spray bead on a substrate at ⁇ 800°C is 20-70%, more preferably 35-65%, more preferably 40-60% of the diameter of the plasma plume at the same stand-off distance, and the width of a single spray bead on a on substrate at ⁇ 800°C may be from -0.5 cm to ⁇ 2.5 cm, and the plume diameter is from ⁇ 1 cm to -5 cm.
- Operating the high enthalpy torch may comprise supplying: electrical power of 60-200 kW, more preferably 80-150 kW, more preferably 110-140 kW; and plasma gas with a total flow rate of 100-500 slpm, more preferably 150-400 slpm; more preferably 250-310 slpm.
- the plasma gas may include N 2 , such as 10-90% N 2 and may consist of 10-80% Ar, 5-40% H 2 , and/or He, and 30-80% N 2 ; or 10-25% H 2 , 25-45% Ar and 45-50% N 2 .
- the feedstock powder may consist of 80% or more, or consist essentially of the high temperature ceramic with a melting point above 1600° ⁇ , such as a high temperature ceramic having a preferred phase preferentially formed only at a temperature above 900°C such as at temperatures between 900-2000 e C, or 900-1600°C.
- the method may be applied to an alkaline earth aluminosilicate, or rare earth silicate, or mullite, as well as an alumina and a titania.
- an alkaline earth aluminosilicate, or rare earth silicate, or mullite as well as an alumina and a titania.
- deposition annealing of BSAS and mullite have been demonstrated.
- a system for thermal spraying to produce a high temperature coating on a ceramic substrate comprises; a high enthalpy air plasma spray torch; a feed supply containing a feedstock powder comprising a high temperature ceramic that has a melting point above 1600°C, the feed supply operably coupled to the torch; a plasma gas supply operably coupled to the torch; an electrical power supply operably coupled to the torch; a ceramic substrate; and a support for controlling a stand-off distance between the ceramic substrate and torch, while permitting a spray jet of the torch to scan across a surface of the substrate to be coated.
- the stand-off distance is chosen so that the width of a single bead on a substrate at ⁇ 800°C is less than 70% of a diameter of a plume of the torch.
- the support and torch are preferably operable so that a localized temperature of the substrate surface within the plasma plume spot during deposition exceeds 1000°C because of the proximity of the torch, and because of an absence of assisted heating or forced cooling.
- the support permitting scanning may comprises a computer numerical controlled subsystem for spraying the ceramic substrate with the torch in at least 3 passes by moving a surface of the substrate to be coated in a direction perpendicular to the spray jet at a speed of 0.1-5 m/s.
- the stand-off distance is preferably where the width of a single bead on a on substrate at ⁇ 800°C is 20-70%, more preferably 35-65%, more preferably 40-60% of the diameter of the plume at the stand off, and the width of the bead at ⁇ 800°C may be from -0.5 cm to -2.5 cm, and the plume diameter at the stand of may be from ⁇ 1 cm to ⁇ 5 cm.
- the electrical supply applies a power of 60-200 kW, more preferably 80-150 kW, more preferably 110-140 kW.
- the plasma gas supply supplies a total plasma gas flow at 100-500 sipm, more preferably 50-400 sipm, more preferably 250-310 sipm.
- the plasma gas includes N 2 , for example, consisting of 10-90% N 2 .
- the plasma gas may consist of 10-80% Ar, 5-40% H 2 , and/or He, and 30-80% N 2 ; or 10-25% H 2 , 25-45% Ar and 45-50% N 2 .
- the feedstock powder may consist of 80% or more of, or substantially consist of an alkaline earth aluminosilicate or rare earth silicate, such as BSAS, or mullite.
- a method of producing a high temperature coating on a ceramic substrate comprising operating a high enthalpy air plasma spray torch and supplying the torch with a feedstock powder comprising a high temperature ceramic with a melting point above 1600°C, that forms undesirable solid phases when rapidly cooled be!ow about 900°C, wherein a cumulative deviation from the following norms is less than 20%:
- 47.5 ⁇ 2.5%, [[H 2 ]
- 17.5 ⁇ 7.5%,
- 35 ⁇ 10%,
- 280 ⁇ 30 sipm,
- 110 ⁇ 23 kW,
- 8 ⁇ 2 cm, where [N 2 ], [H 2 ], and [Ar] are respectively the percentages of N 2 , H 2 , and Ar in the plasma plume, TGF is the total gas flow, P is the torch power, and D is the stand off distance measured in cm.
- the cumulative deviation may be less than 10%, more preferably less than 5% or 1 %.
- Operating the torch may comprise spraying the ceramic substrate with at least 3 passes, by relative movement of a surface of the substrate to be coated perpendicular to the spray jet at a speed of 0.1-5 m/s.
- the feedstock powder may consist of 80% or more, or substantially consist of a ceramic with a melting point above 1600°C, such as a ceramic that preferentially forms a preferred phase only at a temperature above 900°C, such as at temperatures between 900-2000°C, or 900-1600°C.
- F!Gs. 1a,b are schematic illustrations of a high enthalpy air plasma spray apparatus showing a typical suitable stand-off distance for thermal spraying in accordance with the prior art, and an embodiment of the invention, respectively;
- FIG. 2 is a graph of X-ray diffraction (XRD) spectra of high enthalpy, and conventionally sprayed muliite coatings deposited on a ceramic substrate;
- XRD X-ray diffraction
- FIG. 3 schematically illustrates differential thermal analysis (DTA) of the muliite coatings of FIG. 2;
- FIG. 4 is a scanning electron micrograph (SEM) image of BSAS powder particles for use as a feedstock in plasma spraying;
- FIG. 5 is a scanning electron micrograph (SEM) image of a cross-section of a barrier system, including a silicon (Si) bond coat, a muliite interlayer and a BSAS top coat sprayed in accordance with an embodiment of the present invention
- FIG. 6 is a panel showing cross-sectional SEM image of the barrier system after high temperature exposure in water vapour environment, a high magnification image of the bond coat/substrate interface, and an unprotected substrate subjected to the same;
- FIG. 7 plots X-ray diffraction spectra of BSAS powder, the as sprayed coating, and the coating after exposure to the heat treatment
- FIG. 8 is an SEM top view image of a BSAS spray bead showing the importance of multiple passes of the spray torch;
- FIG. 9 is an XRD spectrum of the bead shown in FIG. 8, confirming presence of an amorphous phase in the BSAS coating when only applied in a single pass;
- FIG. 10 is an image of the temperature profile of a SiC-based CMC substrate surface immediately after being heated by the air plasma spray torch for 5 seconds.
- the apparatus includes a hopper 13 connected to the torch by a feed supply 12.
- the hopper 13 contains a high temperature ceramic powder 1 , composed of a ceramic that melts above -1600*0, that is delivered to the torch 10 by the feed supply 12 in a manner known in the art.
- the ceramic used in accordance with the present invention tends to form amorphous, metastable, or otherwise undesirable phases if rapidly cooled below a temperature of about 900°C, and the invention mitigates the formation of the undesirable phases.
- the ceramic may be an alkaline earth aluminosilicate (e.g., BSAS), RES, mul!ite, or an alumina or titania (doped or pure).
- a plasma gas supply 15 (partially shown) is coupled to the torch 10 to supply plasma gas.
- the plasma gas comprises a mix of plasma gasses that together provide 1 ) sufficient thermal conductivity to the ceramic particles, 2) sufficient enthalpy to heat the ceramic particles to a desired temperature, for example, above 2000°C, and 3) a low enough threshold for ionization to readily initiate plasma formation and low enough enthalpy to avoid melting the electrodes of the torch 10.
- 1 )-3) may be ensured by providing: sufficient concentrations of H 2 (e.g., 5-40%, more preferably 10- 25%), N 2 (e.g., 30-80%, more preferably 45-50%), and Ar plasma gas (e.g., 10-80%, more preferably 25-45%), respectively, although other plasma gasses (e.g., He) could be added or substituted to some degree.
- the torch 10 includes an electrical power supply 19 (in partial view) for ionizing the gas to form the plasma, which defines a plume 16, which is typically relatively stable in shape and size during constant supply conditions.
- the particles of the ceramic powder 14, entrained in the plume 16, melt, at least at their surface, and are accelerated by the plume 16, to be ejected as a spray jet 17.
- the parameters of the spray jet 17 (velocity distribution, diameter, temperature distribution, size distribution, etc.) are not as uniform as the envelope of the plume 16, which can typically be maintained in a steady state, and keep a constant shape.
- the spray jet 17 Is rapidly cooling, and gradually decelerating in flight, until it strikes a coating surface of a substrate 18.
- Substrate 18 is formed of a ceramic, such as a Si-based ceramic matrix composite (including SiC, and Si 3 N 4 ).
- the substrate 18 is positioned a relatively short stand off distance D from the torch 10. This obviates the need for assisted heating.
- the stand off distance D is chosen so that the diameter of the plume 16 at D is appreciably larger than the main core of spray jet 7, which forms the individual spray beads.
- the substrate 18 is typically supported by a sample holder 8 in a manner that permits the spray jet 7 to scan across the coating surface, either by motion of the torch 10 or of the sample holder 8 (i.e., the motion normal to the direction of spraying, such as shown by arrow 11).
- the bead width is a sensitive parameter, and may vary widely with changes in the spray jet conditions and deposition conditions.
- the stand off where the bead has a certain width may reliably be determined by providing stable feed conditions, and spraying the substrate while holding a temperature of the substrate constant, such as at 800°C. This not to be understood as a requirement for the substrate to be at 800°C during coating deposition, but merely as one possible manner of reliably determining a bead width as a function of stand off.
- Coating deposition in accordance with the present invention is provided without assisted heating or cooling, and without post spray heat treatment or annealing.
- the invention comprises operating the high enthalpy air plasma spray torch 10 with the ceramic powder 14 to produce a coating on substrate 18 using a set of deposition conditions that substantially conform with the following norms:
- 47.5 ⁇ 2.5%,
- 35 ⁇ 10%,
- 280 ⁇ 30 slpm,
- 110 ⁇ 23 kW,
- 8 + 2 cm
- [N 2 ], [H 2 ], and [Ar] are respectively the percentages of N 2 , H 2l and Ar in the plasma plume, TGF is the total gas flow, P is the torch power, and D is the stand off distance measured in cm.
- pre-heating of the surface of the substrate using the torch can be employed.
- the typical pre-heating temperatures are above ⁇ 500"C, more preferably -800-1000°C.
- a carrier gas Ar at 9 slpm was used to feed the mullite powder in a conventional manner, delivering the powder at a rate of approximately 4 g/min.
- the high enthalpy torch spray parameters were as follows: torch plume gasses were: N 2 45%, Ar 45%, and H 2 10%, total gas flow 280 slpm, power -120 kW, and a stand off distance was 6 cm.
- the diameter of the torch nozzle was 0.5" (1.27 cm).
- the plume had a length greater than 6 cm.
- the substrate was SiC Hexaloy SATM (Saint- Gobain, Niagara Falls, NY, USA). Pre-heating of the substrate with the torch was not employed in this specific case.
- the temperature was raised at a rate of 10°C/min up to 1200°C in an N 2 atmosphere.
- the results of DTA are shown in FIG. 3.
- A shows a strong peak of the conventional APS sprayed coating, whereas B shows no peak at 989° for the high enthalpy APS sprayed coating.
- This powder was fed to a high enthalpy APS torch. The coating was applied overtop of an interlayer of mullite (deposited as described above). The powder feed was assisted by a carrier gas (Ar at 9 slpm) at a powder feed rate of ⁇ 4 g/min.
- Table 1 lists spray parameters used to produce BSAS coatings and mullite coatings with the Axial III APS torch (torch nozzle diameter: 0.5" (1.27 cm)).
- the first three rows are better suited to BSAS deposition, and the last two sets are better suited to mullite deposition.
- the density of BSAS coating produced with the deposition conditions according to bottom two rows were found to be too dense, precluding the easy formation of vertical cracks, and the deposition conditions according to the first 3 rows produce mullite with lower density than is desired.
- Many other thermal spray conditions could be varied that would have an expected effect on the thermal spray conditions resulting in similar coatings, as is well known in the art, and thus features such as feedstock characteristics (e.g. morphology and porosity), feedstock particle size distribution, and feedstock powder feed rate, inter alia can have some impact on the optimal settings.
- the BSAS powder was sprayed using a high-enthalpy APS torch (Axial III, Northwest Mettech, North Vancouver, BC, Canada).
- the coating deposition occurs via a scan pattern of the APS torch on the substrate surface, which sprays successive layers.
- the temperature of the surface of the coating was monitored with a pyrometer, which is placed behind the APS torch. It is important to point out that the pyrometer measures the temperature aimed over a specific point (target) on the coating surface, i.e., the overall surface coating temperate and the substrate temperature are not measured.
- the maximum measured coating surface temperature at the target of the pyrometer was at least ⁇ 1000°C when the high-enthalpy torch was operated at— 113-118 kW, and at least 800°C when operated at -87 kW both at a stand off distance of 6 cm.
- the coating surface temperature is challenging to measure, due to the fact that this event occurs when the high energetic plasma plume and spray jet is over the specific pyrometer target. Thus there is a spatial and/or temporal lag between when the surface is maximally heated and when the temperature is measured. Therefore, the real maximum coating (or substrate) surface temperature is higher than measured via a pyrometer or infra-red camera.
- FIG. 5 is a SEM image showing an as-sprayed barrier system on the SiC substrate, the barrier system having the Si bond coat, the mu!lite interlayer and a BSAS top coat deposited on a SiC Hexoloy SATM substrate.
- the microstructure in FIG. 5 shows that the Si bond coat appears as a dense and crack-free layer showing good adhesion to the substrate (i.e., no gaps or spallation). Likewise good adhesion is shown between the interfaces of the Si bond coat, the mul!ite interlayer and the near-crack free BSAS top coat.
- FIG. 6 includes an image of the same barrier system, showing the effects of heat treatment at 1300 Q C for 500 h in a water vapour environment (left).
- An enlargement of the SiC substrate/bond coat interface (bottom right) shows no appreciable difference before and after the heat treatment.
- An image of an unprotected SiC Hexoloy SATM substrate after the same type of heat treatment is shown at the top right.
- FIG. 7 shows X-ray diffraction (XRD) spectra of BSAS powder (Amperit 870.084, H. C. Starck, Newton, MA, USA), the as-sprayed coating, and the coating after exposure to a high temperature, aggressive heat treatment. Both which substantially consist of the Celsian monoclinic phase as identified based on the JCPDF #38-145 .
- the as-sprayed coating basically exhibits the same crystalline structure, i.e., the diffraction peaks overlap those of the powder. No evident amorphous hump is observed. Therefore, this as sprayed coating appears to be highly crystalline, exhibiting predominantly the celsian phase. After heat treatment at 1300°C for 500 h, substantially the same XRD pattern is produced.
- the exclusivity of the Celsian phase in the as-sprayed coating can be explained by positing that the real maximum coating surface temperature at the plasma jet spot was higher than 1200°C.
- the region under the spot is subjected to an intense heat provided by the plume, providing for annealing in real time of the coating during its deposition.
- FIG. S is a scanning electron micrograph showing in plan view, a single bead of BSAS sprayed at -120 kW (SiC Hexoloy SATM substrate surface pre-heated with the torch at ⁇ 8Q0°C). Arrows point to inclusions that were partially molten in deposition. About half of the surface of the bead is covered by such semi-molten regions. This considerable amount of semi-molten particles will likely influence the energy necessary to nucleate Celsian from amorphous and metastable Hexacelsian (Harder and Faber [8]) during the concurrent annealing and deposition performed by the high enthalpy APS torch.
- FIG. 9 is a XRD spectrum of the single BSAS bead of FIG. 8 and the XRD spectrum of a BSAS coating ( ⁇ 180 pm thick / SiC substrate surface pre-heated with the torch at ⁇ 700°C) sprayed at -85 kW (maximum coating temperature ⁇ 800 e C), using the same APS torch, plasma gas composition and spray distance (6 cm).
- the XRD spectrum shows that in spite being deposited at similar surface temperature conditions, the bead exhibits a significant amount of amorphous phase, characterized by the amorphous hump between the angles of 20 s and 40°. On the contrary, the coating exhibits a highly crystalline Celsian phase.
- the BSAS in at least 3 and preferably in at least 5 passes to perform annealing in real time.
- the higher power levels and total gas flows, in addition to the high enthalpy N 2 gas, provided by the high enthalpy APS torch create the conditions for annealing the sample in real time during spraying, thereby inducing the formation of the celsian phase in as-sprayed coatings, without the necessity of a holding time and/or post-spray annealing.
- This annealing in real time is carried out throughout the successive deposit of spray beads, layers and torch passes over the substrate surface, because one single pass forming a single bead does not promote the formation of a highly crystalline celsian phase.
- the semi-molten BSAS celsian particles embedded in the as-sprayed coating acted as seeds for the nucleation of the Celsian phase transformation from the amorphous and metastable hexacelsian, upon annealing.
- Harder and Faber concluded that the energy necessary to transform APS BSAS coatings will be heavily influenced by the semi-molten particles [8], i.e., the higher the amount of semi-molten BSAS Celsian particles embedded in the coating microstructure, the lower the amount of energy required to nucleate the amorphous/Hexacelsian BSAS into stable crystalline Celsian.
- the IR camera used can measure temperatures from 200°C to 1600°C.
- the measured temperature increases abruptly to values higher than 1600°C (i.e., the limit of the equipment).
- the temperature is not registered for -1.5 s, until it cools down to 1600°C and below. Therefore, during a continuous deposition when multiple torch scans are employed to build the coating on the substrate surface, using the conditions described in this invention, the coating surface temperature levels under the plasma plume spot likely reach values higher than 1600°C.
- the thermodynamic conditions required to induce the amorphous/Hexacelsian phase transformation to stable crystalline Celsian seem to occur.
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Abstract
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CA2856756A CA2856756A1 (en) | 2011-11-25 | 2011-11-25 | Method and apparatus for depositing stable crystalline phase coatings of high temperature ceramics |
US14/360,487 US20140329021A1 (en) | 2011-11-25 | 2011-11-25 | Method and Apparatus for Depositing Stable Crystalline Phase Coatings of High Temperature Ceramics |
GB1409226.6A GB2510540A (en) | 2011-11-25 | 2011-11-25 | Method and apparatus for depositing stable crystalline phase coatings of high temperature ceramics |
PCT/CA2011/001285 WO2013075202A1 (en) | 2011-11-25 | 2011-11-25 | Method and apparatus for depositing stable crystalline phase coatings of high temperature ceramics |
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Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
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US20160133826A1 (en) * | 2014-11-06 | 2016-05-12 | Agency For Science, Technology & Research | Method of making lead-free ceramic coating |
US9410868B2 (en) | 2014-05-30 | 2016-08-09 | General Electric Company | Methods for producing strain sensors on turbine components |
US9546928B2 (en) | 2014-05-30 | 2017-01-17 | General Electric Company | Methods for producing strain sensors on turbine components |
US10415964B2 (en) | 2014-05-30 | 2019-09-17 | General Electric Company | Methods for producing passive strain indicator on turbine components |
US10557372B2 (en) | 2015-12-17 | 2020-02-11 | General Electric Company | Systems and methods for assessing strain of components in turbomachines |
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EP3199507A1 (en) | 2016-01-29 | 2017-08-02 | Rolls-Royce Corporation | Plasma spray physical vapor deposition deposited multilayer, multi-microstructure environmental barrier coating |
CN114592164B (en) * | 2022-01-20 | 2024-03-08 | 华东理工大学 | DVC thermal barrier coating and preparation method and application thereof |
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CA2073153C (en) * | 1991-07-09 | 1994-04-05 | Zbigniew Zurecki | Wear resistant titanium nitride coating and methods of application |
US5707694A (en) * | 1996-05-31 | 1998-01-13 | Caterpillar Inc. | Process for reducing oxygen content in thermally sprayed metal coatings |
US6468648B1 (en) * | 1997-11-12 | 2002-10-22 | United Technologies Corporation | Plasma sprayed mullite coatings on silicon based ceramic materials |
US6787195B2 (en) * | 2003-02-03 | 2004-09-07 | General Electric Company | Method of depositing a coating on Si-based ceramic composites |
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US6129954A (en) * | 1998-12-22 | 2000-10-10 | General Electric Company | Method for thermally spraying crack-free mullite coatings on ceramic-based substrates |
US6576861B2 (en) * | 2000-07-25 | 2003-06-10 | The Research Foundation Of State University Of New York | Method and apparatus for fine feature spray deposition |
JP4645030B2 (en) * | 2003-12-18 | 2011-03-09 | 株式会社日立製作所 | Heat resistant member with thermal barrier coating |
US20050238807A1 (en) * | 2004-04-27 | 2005-10-27 | Applied Materials, Inc. | Refurbishment of a coated chamber component |
EP2563743A1 (en) * | 2010-04-30 | 2013-03-06 | Rolls-Royce Corporation | Durable environmental barrier coatings for ceramic substrates |
-
2011
- 2011-11-25 US US14/360,487 patent/US20140329021A1/en not_active Abandoned
- 2011-11-25 GB GB1409226.6A patent/GB2510540A/en not_active Withdrawn
- 2011-11-25 CA CA2856756A patent/CA2856756A1/en not_active Abandoned
- 2011-11-25 WO PCT/CA2011/001285 patent/WO2013075202A1/en active Application Filing
Patent Citations (4)
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CA2073153C (en) * | 1991-07-09 | 1994-04-05 | Zbigniew Zurecki | Wear resistant titanium nitride coating and methods of application |
US5707694A (en) * | 1996-05-31 | 1998-01-13 | Caterpillar Inc. | Process for reducing oxygen content in thermally sprayed metal coatings |
US6468648B1 (en) * | 1997-11-12 | 2002-10-22 | United Technologies Corporation | Plasma sprayed mullite coatings on silicon based ceramic materials |
US6787195B2 (en) * | 2003-02-03 | 2004-09-07 | General Electric Company | Method of depositing a coating on Si-based ceramic composites |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
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US9410868B2 (en) | 2014-05-30 | 2016-08-09 | General Electric Company | Methods for producing strain sensors on turbine components |
US9546928B2 (en) | 2014-05-30 | 2017-01-17 | General Electric Company | Methods for producing strain sensors on turbine components |
US10415964B2 (en) | 2014-05-30 | 2019-09-17 | General Electric Company | Methods for producing passive strain indicator on turbine components |
US20160133826A1 (en) * | 2014-11-06 | 2016-05-12 | Agency For Science, Technology & Research | Method of making lead-free ceramic coating |
US10557372B2 (en) | 2015-12-17 | 2020-02-11 | General Electric Company | Systems and methods for assessing strain of components in turbomachines |
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US20140329021A1 (en) | 2014-11-06 |
GB2510540A (en) | 2014-08-06 |
GB201409226D0 (en) | 2014-07-09 |
CA2856756A1 (en) | 2013-05-30 |
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