RU2436752C2 - Highly pure powder and coating made from said powder - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: present invention relates to highly pure zirconium oxide powder for applying coatings on substrates meant for use in conditions with cyclic thermal loads, such as blades, guide devices and on the sealing surface of gas-turbine engines. The highly pure zirconium oxide powder, which is stabilised with yttrium or ytterbium, contains from approximately 0 to approximately 2 wt % hafnium oxide, from approximately 6 to approximately 25 wt % yttrium oxide or from approximately 10 to approximately 36 wt % ytterbium oxide, from approximately 0 to approximately 0.15 wt % impurity oxides. The impurity oxides include the following in wt %: 0-0.02 SiO₂, 0-0.005 Al₂O₃, 0-0.01 CaO, 0-0.01 Fe₂O₃, 0-0.005 MgO, 0-0.01 TiO₂. The coatings which form a thermal barrier have multiple vertical microcracks which are uniformly distributed on the entire coating, which increases resistance of the coatings to thermal fatigue. The coatings are applied via thermal spraying with possible subsequent thermal treatment.

EFFECT: longer service life of coated substrates.

15 cl, 7 ex, 9 tbl, 11 dwg

Description

FIELD OF THE INVENTION

The present invention relates to high purity yttrium or ytterbium oxide stabilized zirconia powders, coatings made from yttrium or ytterbium oxide stabilized zirconia powders, and methods for coating substrates intended for use under cyclic thermal loads, where the coatings have a substantially uniform distribution of vertical macrocracks over the entire coating, which improves its resistance to thermal fatigue.

State of the art

Modern gas turbine engines operate at high temperatures in excess of 2000 ° F (1094 ° C), in which hot gases expand in the direction transverse to the rows of turbine blades. An air seal or band segments are adjacent to the turbine blades to minimize gas loss along the end of the blades. It has been found that the use of thermal barrier coatings on gas turbine blades and surfaces such as band segments has several advantages. By using thermal barrier coatings, higher operational efficiencies can be achieved, since less cooling air is needed to maintain the temperature of the blade or bandage. In addition, the service life of the parts increases, since due to the heat-insulating effect that creates the thermal barrier of the coating, the rate of change in the temperature of the metal decreases.

In order to isolate metal parts from the flow of hot gas, zirconium oxide-based coatings that create a thermal barrier are applied to their surface and have low thermal conductivity. Stabilized zirconia was developed and used as a thermal barrier coating for turbine parts and brace elements. Coatings such as zirconia stabilized with CaO, zirconia stabilized with MgO, and zirconia stabilized with yttrium have been tested; best results were obtained for zirconium oxide partially stabilized with yttrium oxide.

U.S. Pat. This patent also describes a method for applying a thermal barrier coating.

In this area, there remains a need for thermal barrier coatings with improved properties intended for use in cyclic thermal loads, for example, on the surface of gas turbine blades, guides, and seals that are exposed to the high-temperature zone of gas turbine engines.

SUMMARY OF THE INVENTION

The present invention relates to high purity yttrium or ytterbium oxide zirconia powders containing from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest is zirconium oxide.

The present invention also relates to thermal spray coatings of a high purity powder stabilized with yttrium or ytterbium zirconia, where a high purity powder stabilized with yttrium or ytterbium oxide of zirconium contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest is zirconium oxide.

The present invention also relates to a thermal barrier coating for substrates containing partially stabilized yttrium or ytterbium oxide zirconia and having a density exceeding 88% of theoretical density, with many vertical macrocracks substantially uniformly distributed throughout the coating, in which the cross section is perpendicular the substrate opens up many vertical macrocracks, extending at least half the thickness of the coating and reaching a length equal to the full thickness of the coating, and which has from about 5 to about 200 vertical macrocracks per linear inch (2-78.7 per cm), measured along a line parallel to the surface of the substrate and lying in a plane perpendicular to the surface of the substrate, where the specified thermal barrier the coating is formed by thermal spraying a coating of a high-purity powder stabilized with yttrium or ytterbium oxides of zirconium oxide, where a high-purity powder stabilized with yttrium or ytterbium oxides of zirconium oxide um from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest is zirconium oxide.

In addition, the present invention relates to a method for producing a thermal barrier coating, comprising

a) thermal precipitation of a high purity yttrium or ytterbium oxide zirconia powder, wherein the powder contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest is zirconium oxide on the substrate to form a monolayer having at least two superimposed grains of powder deposited on the substrate, the temperature of the later deposited grain being higher than the previously deposited grain;

b) cooling and curing the specified monolayer obtained in stage a), after which the specified monolayer acquires a density of at least 88% of the theoretical density and in which, as a result of the shrinkage of the deposited grains, many vertical macrocracks form;

c) repeating steps a) and b) at least once in order to obtain a layer with a full surface coating, in which each monolayer has vertical cracks passing through the grains, and in which many vertical cracks of each monolayer are directed in the same way as vertical cracks of an adjacent monolayer, with the formation of vertical macrocracks with a length of at least half the coating thickness and reaching a full coating thickness in length, where the applied layer is characterized by the presence of at least 5 vertical macrocracks in per linear inch (2 per 1 cm), measured along a line parallel to the surface of the substrate and lying in a plane perpendicular to the surface of the substrate.

The present invention also relates to a thermal spraying method, comprising thermally depositing a high purity yttrium or ytterbium oxide zirconia powder, wherein the powder contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest - zirconium oxide, on the substrate to obtain a coating with vertical segments of cracks distributed essentially over the entire thickness of the coating, characterized by the presence of from about 5 to about 200 cracks per linear inch (2-78.9 per 1 cm ), measured along a line parallel to the coating plane, and the presence of a horizontal crack structure that is sufficient to reduce thermal conductivity to less than 0.012 W / cm at 25 ° C over the coating thickness.

The present invention also relates to a thermal spraying method, comprising thermally depositing a high purity yttrium or ytterbium oxide zirconia powder, wherein the powder contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest - zirconium oxide, on the substrate to obtain a coating with vertical segments of cracks distributed essentially over the entire thickness of the coating, characterized by the presence of from about 5 to about 200 cracks per linear inch (2-78.7 per 1 cm ), measured along a line parallel to the plane of the coating, and having a thickness of from about 5 to about 200 mils (127-5080 microns); and having a final surface layer formed from said high purity zirconia powder stabilized with yttrium or ytterbium oxides up to about 5 mils (127 μm) thick with essentially zero segmentation by vertical cracks.

The present invention further relates to a thermal spraying method comprising the thermal deposition of a high purity yttrium or ytterbium oxide zirconia powder, wherein the powder contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest - zirconium oxide, on the substrate to obtain a coating with vertical segments of cracks distributed essentially over the entire thickness of the coating, characterized by the presence of from about 5 to about 200 cracks per linear inch (2-78.7 per 1 cm ), measured along a line parallel to the plane of the coating, and having a thickness of from about 5 to about 200 mils (127-5080 microns); and having a final surface layer comprising a ceramic frit coating obtained by immersion or spraying a solution of a thickness of up to about 5 mils (127 μm); and high temperature treatment of the surface layer with hot air to bind and fix the surface layer.

The present invention also relates to articles with a thermal barrier coating, the thermal barrier coating comprising a thermal spray coating of a high purity yttrium or ytterbium oxide oxide powder, wherein the powder contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest is zirconium oxide.

The present invention also relates to products with a thermal barrier coating containing zirconia partially stabilized with yttrium or ytterbium oxides, having a density of more than 88% of theoretical, and having many vertical macrocracks substantially uniformly distributed throughout the coating, in which perpendicular to the substrate, the cross section reveals many vertical macrocracks that extend at least half the thickness of the coating and reach a length equal to half the thickness of the coating, and which has from about 5 to about 200 vertical macrocracks per linear inch (2-78.7 per 1 cm), measured along a line parallel to the surface of the substrate and lying in a plane perpendicular to the surface of the substrate, where the thermal barrier coating formed by thermal spraying a coating of a high-purity powder stabilized by yttrium or ytterbium oxide zirconium oxide, where a high-purity powder stabilized by yttrium or ytterbium oxide zirconium oxide contains from about 0 of about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest is zirconium oxide.

Brief Description of the Drawings

1 graphically depicts the deposition efficiency of a new high-purity yttrium oxide stabilized zirconia powder (i.e., a C line or ZrO-300 powder, which corresponds to a solid line) and conventional yttrium oxide stabilized zirconia powder (i.e. a powder D or ZrO-137, which corresponds to the dashed line) in order to obtain coatings on 3/8 inch (9.525 mm) square steel plates.

Figure 2 graphically shows the measured density of coatings obtained at a distance of 1 inch (25.4 mm) from the substrate to the burner on 3/8 inch (9.525 mm) square steel plates for a new high-purity yttrium oxide stabilized zirconia powder (i.e. i.e., C or ZrO-300 powder, which corresponds to the solid line), and for the usual yttrium-stabilized zirconia powder (i.e., D or ZrO-137 powder, to which the dashed line corresponds).

Figure 3 graphically shows the dependence of the density of the vertical segments of the cracks (number of cracks per linear inch (CPI) of the length of the polished coating cross section) on the height of the monolayer for the coating obtained from a new high-purity yttria stabilized zirconia powder (i.e., powder C or ZrO-300) on a disk-shaped substrate with a diameter of 1.0 inch (25.40 mm) (solid line) and for a coating obtained from a conventional yttrium oxide stabilized zirconia powder (i.e., D or ZrO-137 powder ) on a disk-shaped substrate with a diameter of trom 1.0 inch (25.40 mm) (dashed line).

Figure 4 is a phase diagram of a zirconia-rich region of the ZrO ₂ - Y ₂ O _{3 system} . (See Bratton and Lau, Science & Technology of Zirconia, Amer. Ceram. Soc., 1981, p. 226-240).

Figure 5 presents the spectrum of x-ray diffraction analysis using K-alpha radiation of copper for coating from a conventional powder ZrO-137 after it is kept for 100 hours in air at 1400 ° C. The initial strict tetragonal structure was transformed into a 19.4% monoclinic structure.

Figure 6 presents the spectrum of x-ray diffraction analysis using K-alpha radiation of copper for coating of a new high-purity powder ZrO-300 after it was kept for 100 hours in air at 1400 ° C. The initial strict tetragonal structure after 100 hours at 1400 ° C did not change.

Figure 7 graphically shows the dependence of the density of the coating of conventional ZrO-137 powder on time at a temperature of from 1200 ° C to 1400 ° C in air. The density after coating (dotted lines with short strokes) was 91.5% of the theoretical. This fraction still decreased at 1300 ° C (solid line) and 1400 ° C (dotted line with long strokes).

On Fig graphically presents the dependence of the density of the coating of the new high-purity powder ZrO-300 from time to time at a temperature of from 1200 ° C to 1400 ° C in air. The density after coating (dashed line) was 92.7% of theoretical. After aging for at least 100 hours at 1400 ° C, this fraction did not change (solid line).

Figure 9 graphically shows the ratio of the fraction of fracturing (horizontal) cracks and the density of vertical crack segments (CPI) for coating from a new high-purity powder ZrO-300 (dashed line) and from ordinary powder ZrO-137 (solid line).

Figure 10 graphically shows the dependence of the proportion of edge cracks after 2000 JETS test cycles on the density of vertical segments from cracks (in CPI) for coating of a new high-purity ZrO-300 powder without additional processing after application. With cracking of more than 15%, the coating was deemed unfit, which at approximately 10 CPI (4 per 1 cm) or more did not occur.

11 graphically shows the dependence of the fraction of edge cracks after 2000 JETS test cycles on the density of the vertical crack segments (in CPI) for the coating of the new high-purity powder ZrO-300 subjected to heat treatment (4 hours / 1975 ° F / vacuum). With cracking of more than 15%, the coating was deemed unfit, which at approximately 5 CPI (2 per 1 cm) or more did not occur.

DETAILED DESCRIPTION OF THE INVENTION

A new morphology of yttrium oxide stabilized zirconia powder has been discovered, which is also applicable to other zirconium oxide powders with other stabilizers in addition to or in addition to yttrium or ytterbium oxides. It was found that new high-purity yttrium or ytterbium oxide stabilized zirconia powders, combined with new conditions for plasma spraying or thermal spraying using a detonation gun, have much higher deposition efficiency, density, acceptable deviation of coating parameters and are suitable for forming the desired crack structure providing resistance to mechanical stress. In a heat shock test at a high temperature, it was found that coatings from new high-purity yttrium or ytterbium oxide stabilized zirconia powders are superior to the known thermal barrier segmented yttrium oxide-stabilized zirconia coatings.

In the context of this document, grain is understood as a separate molten particle of powder falling onto the surface of a substrate, where it is flattened to form a thin plate. Typically, these plates are 5 to 100 microns in diameter and 1 to 5 microns in thickness, generally about 2 microns in thickness.

In the context of this document, a vertical macrocrack is a crack in the coating, which, extended to contact with the surface of the substrate, forms an angle of 30 ° to 0 °, with a straight line extending from the specified point of contact perpendicular to the surface of the substrate. Preferably, the vertical macrocracks form an angle of 10 ° to 0 ° with this perpendicular. In addition to vertical macrocracks, one or more horizontal macrocracks can form in the coating. Preferably, the coating should not have horizontal macrocracks. A horizontal macrocrack is a crack forming, with a plane dividing the crack in half and parallel to the surface of the substrate, an angle of 10 ° to 0 °. Horizontal cracks, if present, should preferably not have a length allowing them to cross more than one vertical macrocrack, as this can weaken the coating and cause it to crack. The length of the vertical macrocrack and the length of the horizontal macrocrack are the distance in a straight line from one end of the crack to the opposite end of the crack. The length of the horizontal crack, if any, should be between about 5 and 25% of the cross section of the coating, considering only those horizontal cracks that come in contact with two or more vertical segmentation cracks.

The coatings of the present invention are thermal barrier coatings with low thermal conductivity inherent to zirconia materials. Porosity and interface within the coating are also obstacles to the heat flux and, therefore, lead to a decrease in effective thermal conductivity. However, in accordance with the present invention, it is expressly provided that such a coating has a high density (low porosity) and, therefore, high erosion resistance and a tendency to form crack segments as a result of the process described herein. It is usually understood that it also has a low horizontal crack density, as this can affect the service life under thermal shock. However, in accordance with the present invention, the density of horizontal cracks can be minimized or maximized, since both structures can be applied. In the case when the effect of thermal shock is not too intense, it is possible to specifically increase the density of horizontal cracks and thus reduce thermal conductivity. This is carried out during the coating process using a plasma torch to create gaps at the usually well-connected interfaces formed by successive passes of the torch.

As indicated above, the present invention relates to high purity yttrium or ytterbium oxide zirconia powders containing from about 0 to about 0.15, preferably from about 0 to about 0.12% by weight. impurity oxides, from about 0 to about 2, preferably from about 0 to about 1.5%, by weight. hafnium oxide, from about 6 to about 25, preferably from about 6 to about 10, more preferably from about 6.5 to about 8% by weight. yttrium oxide or from about 10 to about 36, preferably from about 10 to about 16, more preferably from about 11 to about 14% by weight. ytterbium oxide and the rest is zirconium oxide. Impurity oxides contain from about 0 to about 0.02, preferably from about 0 to about 0.01% by weight. silica, from about 0 to about 0.005, preferably from about 0 to about 0.002%, by weight. alumina, from about 0 to about 0.01, preferably from about 0 to about 0.005%, by weight. calcium oxide, from about 0 to about 0.01, preferably from about 0 to about 0.005%, by weight. iron oxide, from about 0 to about 0.005, preferably from about 0 to about 0.002%, by weight. magnesium oxide and from about 0 to about 0.01, preferably from about 0 to about 0.005%, by weight. titanium dioxide.

High purity yttrium or ytterbium oxide stabilized zirconia powders of the present invention may contain mixtures of two or more yttrium or ytterbium oxide stabilized zirconia powders. For example, a high purity yttrium or ytterbium oxide stabilized zirconia powder of the present invention may contain from about 55 to about 95% vol. a first highly pure zirconium oxide powder partially stabilized with yttrium or ytterbium oxides containing from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 10, preferably from about 6 to about 8%, by weight. yttrium oxide or from about 10 to about 14, preferably from about 10 to about 12%, by weight. ytterbium oxide and the rest is zirconium oxide, and from about 5 to about 45% vol. a second highly pure zirconium oxide powder, fully stabilized with yttrium or ytterbium oxides, containing from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 16 to about 22% weight. yttrium oxide or from about 25 to about 33% weight. ytterbium oxide and the rest is zirconium oxide.

A mixture of high-purity yttrium or ytterbium oxide stabilized zirconia powders may contain a mixture of two or more high-purity yttrium or ytterbium oxide zirconia powders that reduce the thermal conductivity of the composite coating made from them and retain the heat resistance characteristic of a partially stabilized zirconia 6 -10, preferably 6-8% by weight. yttrium oxide. In one of the embodiments of the invention, such mixtures contain from about 20 to about 45% vol. the second highly pure zirconium oxide powder, fully stabilized with yttrium or ytterbium oxides, and from about 55 to about 80% vol. the first highly pure zirconium oxide powder partially stabilized with yttrium or ytterbium oxides.

Coatings in which 6.5-8% by weight is added to zirconium oxide. yttrium oxide, have the desired heat resistance, is believed to be due to the process of thermal improvement at the leading edge of the growing crack, where the tetragonal phase transforms into monoclinic during loading. However, zirconia stabilized with 20% weight. yttrium oxide, called fully stabilized, since it has a cubic structure and does not undergo phase transformation, has a lower thermal conductivity. Typically, heat resistance is more important than low thermal conductivity, therefore, in industry, zirconia stabilized at 7% weight is more often used. yttrium oxide.

According to the present invention, if a material stabilized with a small amount of yttrium oxide in the coating forms a continuous phase and a material stabilized with a large amount of yttrium oxide is isolated in the matrix, it is possible to benefit from the lower thermal conductivity of the material stabilized with a large amount of oxide yttrium, since the heat flux passing through the coating, i.e. all its constituent materials, interfaces and pores, are averaged. If cracks appear in particles with a high content of yttrium oxide under the influence of thermal shock, they affect only this phase and do not pass into the surrounding matrix with a low content of yttrium oxide.

This is achieved by mixing in the right proportion two separate powders and their thermal spraying with the formation of a composite coating. The main component should be a powder with a low content of yttrium oxide, so that it forms a continuous phase, or matrix, of the coating. The level of decrease in thermal conductivity is compensated by an increase in the amount of zirconium oxide with a high content of yttrium oxide, i.e. in accordance with the intended purpose, the ratio of the components is selected. If the effects of thermal shock are not too intense, more of the high yttrium oxide component may be added.

Compound high purity yttrium or ytterbium oxide stabilized zirconia powders are also useful in the context of the present invention, designed to improve abrasive properties. If the coating contains a second component having a higher abrasive ability than zirconium oxide, it is preferable that the particle size of the second component be in any direction at least 2 mils (50.8 μm) and up to 95% of the coating thickness. In this embodiment of the invention, using at least two powders, it is preferred that the fine particles of zirconium oxide adhere to the surface of the larger abrasive particles. Suitable abrasive particles may be alumina, chromium oxide or alloys thereof, incorporated into the powder composition in an amount of from 10 to 40% by weight. the total weight of the powder, preferably from 20 to 30% weight. total weight of the powder composition.

Also included within the scope of the present invention are composite high-purity yttrium or ytterbium oxide stabilized zirconia powders designed to reduce thermal conductivity. An illustrative example of composite powders is a composite high purity yttrium or ytterbium oxide stabilized zirconia powder containing a high purity yttrium or ytterbium oxide stabilized zirconia powder in which about 0 to about 0.15% by weight. constitute impurity oxides, from about 0 to about 2% weight. is hafnium oxide, from about 6 to about 25% weight. - yttrium oxide or from about 10 to about 36% weight. - ytterbium oxide and the rest is zirconium oxide, and which has a nominal average particle size of 20-60 microns, to the surface of which are connected particles of gadolinium oxide with a nominal average size of 0.5-2 microns.

Compound high-purity yttrium or ytterbium oxide stabilized zirconia powders designed to reduce thermal conductivity provide a simple and cost-effective ability to further control the thermal conductivity of the powder. Typically, such a powder may be made by one of the methods described herein, such as a melting and crushing method. An additional component, for example gadolinium oxide, may be added to the molten mixture in the right amount. This operation is usually carried out for large portions, for example 100 pounds or more. If the amount entered is slightly different from the set, the whole portion can go to waste, which represents a significant cost.

In addition, at the stage of sorting by size, the fused mass can be crushed into a fine powder. Usually this operation is associated with large losses, as larger and smaller particles go to waste. In this embodiment of the present invention, the base material can be manufactured in the usual manner, for example, be zirconia stabilized at 7% by weight. yttrium oxide, with the desired particle size. Larger and smaller particles can be reused in the melting stage of the next batch. Then, a basic powder with the desired particle size, usually with an average size of about 20-60 microns, is mixed with ultrafine particles of gadolinium oxide with the addition of a binder, such as diluted white glue. The powder is dried and shaken a little to separate coalesced large particles. The finely dispersed gadolinium oxide adheres to the surface of large basic particles in about the right amount.

It is possible to calculate how many finely divided gadolinium oxide or a similar component need to be added to the mixture in order to obtain a given composite powder. This is done by measuring the average volume of large bulk particles using a Microtrac particle size analyzer. The same operation is carried out with ultrafine particles of the additive. It is important that the added particles are very small, then they can be uniformly distributed and glued to the large particles in the right proportion. A size of about 0.5-2 microns for fine particles and about 60 microns for large base particles is considered appropriate. In order to find an adequate amount of additives, in each case, such a calculation should be performed. The composite particles are then sprayed using any thermal spraying device in which the entire composition is fused as a result of melting the particles. This method allows to produce both small and large portions; by adding to a given mass of the major coarse particles more or less ultrafine component, any composite composition can be obtained.

The average particle size of the thermal sprayable powders applicable in the context of the present invention is preferably set according to the type of thermal spraying device and the thermal spraying conditions used. The average particle size may be from about 1 to about 150 microns, preferably from about 5 to about 50 microns, more preferably from about 10 to about 45 microns.

The present invention provides high-purity yttrium or ytterbium oxide stabilized zirconia powders from which a thermal spray coating with a density of more than 88% of theoretical can be formed with many vertical macrocracks distributed substantially uniformly throughout the coating, in which the cross section of the coating, perpendicular to the substrate, opens up many vertical macrocracks that extend at least half the thickness of the coating and reach lengths of other full thickness of the coating, and in which there is from about 5 to about 200 (2-78.7 per 1 cm), preferably from about 20 to about 200 (7.9-78.7 per 1 cm), more preferably from about 40 to about 100 vertical macrocracks per linear inch (15.7-39.3 per 1 cm), measured along a line parallel to the surface of the substrate and lying in a plane perpendicular to the surface of the substrate.

Thermally sprayed powders useful in the context of the present invention can be obtained by conventional methods such as agglomeration (spray drying and sintering or sintering and crushing) or casting and crushing. According to the spray drying and sintering method, a suspension is first prepared by mixing a plurality of powdered starting materials and an appropriate dispersion medium. Then, during spray drying, this suspension is granulated, after which the granular powder is sintered to form coherent powder particles. Thermal spraying powder is obtained by sieving and sorting (if the agglomerates are too large, their size is reduced by crushing). The sintering temperature of the granular powder is preferably 1000-1300 ° C.

Thermally sprayed powders according to the present invention can be obtained in another way, including agglomeration, sintering and crushing. During sintering and crushing, a compact is first obtained by mixing a variety of powdery starting materials, which are pressed and then sintered at a temperature of from 1200 to 1400 ° C. Then, by crushing and sorting the resulting sintered compact in accordance with a given particle size distribution, a powder for thermal spraying is obtained.

Thermally sprayed powders according to the present invention can also be obtained by casting (smelting) and crushing, replacing the agglomeration method. In accordance with the melting and crushing method, first, by mixing a plurality of powdery starting materials and subsequent rapid heating, casting and cooling, an ingot is obtained. After that, by crushing this ingot and sorting the particles, a powder is obtained for thermal spraying.

Typically, powders for thermal spraying can be obtained by the following conventional methods:

spray drying and sintering method - the powdered starting materials are mixed to obtain a suspension, which is granulated by spray drying. Then, the agglomerated powder is sintered at a high temperature (at least 1000 ° C) and sieved to separate the particle size distribution necessary for spraying;

sintering and crushing method — the powdered starting materials are sintered at a high temperature in an atmosphere of hydrogen or an inert gas (at a low partial pressure of oxygen), then subjected to mechanical crushing and sieved to separate the particle size distribution necessary for spraying;

casting and crushing method - the powdered starting materials are melted in a crucible, the resulting casting is subjected to mechanical crushing and the particles are sieved; and

compaction method — a powder obtained by any of the above methods (i) to (iii) is heated by a plasma jet or laser and sieved (plasma compaction or laser compaction methods).

The average particle size of the powder of each of the starting materials used in the spray drying method is preferably not less than 0.1 microns, more preferably not less than 0.2 microns, but preferably not more than 10 microns. If the average particle size of the powder of the starting material is too small, costs may increase. If the average particle size of the starting material powder is too large, it may be difficult to achieve an even distribution of the starting material powder.

The individual particles constituting the powder for thermal spraying preferably have sufficient mechanical strength to remain coherent during the thermal spraying process. If their mechanical strength is too low, the powder particles may break down, clogging the nozzle, or accumulate on the inner walls of the thermal spraying device.

The coating process involves the flow of powder through a thermal spraying device, heating the powder and giving it acceleration in the direction of the substrate. Upon collision, the heated particle is deformed, turning into a flake or grain caused by thermal spraying. The overlapping grains comprise the coating structure. The detonation method applicable in the context of the present invention is described in US patent No. 2714563, incorporated herein by reference. Moreover, the method of detonation is described in US patent No. 4519840 and No. 4626476, incorporated herein by reference. US Pat. No. 6,503,290, incorporated herein by reference, describes a method for using oxygen fuel having a high speed that is applicable in the context of the present invention.

As indicated above, the present invention relates to thermal spray coatings, for example, thermal barrier coatings, of a high purity yttrium or ytterbium oxide stabilized zirconia powder, where a high purity yttrium or ytterbium oxide stabilized zirconia powder contains from about 0 to about 0.15% weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest is zirconium oxide. The above described are high-purity yttrium or ytterbium oxide stabilized zirconia powders that are suitable for the production of thermal spray coatings.

Thermally sprayed coatings, for example, creating a thermal barrier to a coating, typically have a density of more than 88% theoretical and a plurality of vertical macrocracks substantially uniformly distributed throughout the coating, in which a cross-section perpendicular to the substrate opens up a plurality of vertical macrocracks that extend at least half the thickness of the coating and reaching a length equal to the total thickness of the coating, preferably a density of 90% to 98% of those retic, and many of these vertical macrocracks, extending at least half the thickness of the coating and reaching a length equal to the total thickness of the coating, which has from about 5 to about 200 vertical macrocracks per linear inch (2-78.7 per 1 cm), preferably from about 20 to about 100 vertical macrocracks per linear inch (7.9-39.3 per 1 cm), more preferably from about 40 to about 60 vertical macrocracks per linear inch (15.7-23.6 per cm), measured along a line parallel to the surface of the substrate ki and lying in a plane perpendicular to the surface of the substrate. The width of the vertical macrocracks is usually less than about 1 mils (25.4 microns). In one embodiment of the invention, the thermal spray coatings may have vertical segmentation cracks that form three-dimensional cells in the thickness of the coating with an average cell width of 0.02 inches (508 μm) in the range of about 0.005 to about 0.2 inches (127 -5080 μm).

Thermally sprayed coatings, for example, creating a thermal barrier to the coating, can have one or more horizontal macrocracks extending parallel to the surface of the substrate inside the coating. Horizontal macrocracks are preferably not in contact with more than one vertical macrocrack. Thermally sprayed coatings may contain horizontal crack segments connecting any two vertical segmentation cracks, the total total length of which, measured in the polished cross section, is less than 10% of the coating width.

In one embodiment, a binder coating may be applied between the substrate and the thermal spray coating, for example, a thermal barrier coating. The bonding coating usually contains an alloy of chromium, aluminum, yttrium with a metal selected from the group consisting of nickel, cobalt and iron. The binder coating is preferably an MCrAlY + X coating applied by plasma spraying methods, or by detonation spraying methods, or by electrodeposition methods, where M is Ni, Co or Fe, or any combination of these three elements, X is the addition of Pt, Ta, Hf, Re or other rare earth metals or fine particles of aluminum oxide - dispersing agent, separately or in combination.

Thermally sprayed coatings, for example, providing a thermal barrier to a coating, of the present invention have several desirable properties, including the following: increased sintering resistance, i.e. at 1200 ° C their density after 4 hours increases by less than 0.5%; the elastic modulus in the coating plane is less than 0.6 MPa and the cohesive strength in the direction of the coating thickness is more than 40 MPa; after 4 hours at 1200 ° C, the elastic modulus in the coating plane is less than 0.9 MPa and the cohesive strength in the direction of the coating thickness is more than 45 MPa; thermal conductivity in the direction along the coating thickness of less than 0.014 W / cm at 25 ° C and less than 0.0135 W / cm at 500 ° C; 4 hours later at 1200 ° C, thermal conductivity in the direction along the coating thickness is less than 0.015 W / cm at 25 ° C and less than 0.014 W / cm at 500 ° C; particle erosion rate during bombardment with pointed alumina particles of 50 μm at an angle of 20 ° at a speed of 200 ft / s (61 m / s) at 25 ° C less than 1 mg per 1 g of erodent; after 4 hours at 1200 ° C, the rate of particle erosion when bombarded with pointed alumina particles of 50 μm at an angle of 20 ° at a speed of 200 ft / s (61 m / s) at 25 ° C is less than 0.5 mg per 1 g of erodent; less than 3% of the monoclinic phase detected by x-ray diffraction methods; after 4 hours at 1200 ° C, less than 3% of the monoclinic phase detected by X-ray diffraction methods.

Thermally sprayed coatings of the present invention can be further stabilized by heat treatment in vacuum or in air at a temperature of 1000 ° C or higher. As described in more detail in Example 7 below, the threshold CPI value corresponding to excellent thermal shock resistance was reduced from 20 CPI (7.9 per 1 cm) for coatings of conventional ZrO-137 powder to about 5 CPI (2 per 1 cm) for coatings from the new high-purity powder ZrO-300. One of the embodiments of the present invention is the coating of high-purity powder ZrO-300 with a structure with a safe level of CPI and then heat treatment of the coated product.

As indicated above, the present invention relates to thermal barrier coatings designed to protect a substrate, for example, the surfaces of vanes, guides and gas turbine engine seals, where the coatings contain partially stabilized yttrium oxide zirconia, have a density of more than 88% theoretical and have many vertical macrocracks essentially uniformly distributed throughout the coating, in which a transverse, perpendicular to the substrate, the cross section opens up many vertical macrocracks extending at least half the coating thickness, preferably at least 2/3 of the coating thickness and reaching a length equal to the full thickness of the coating, and which has from about 5 to about 200 (2-78, 7 per 1 cm), preferably from about 20 to about 200 vertical macrocracks (7.9-78.7 per 1 cm), more preferably from about 40 to about 100 vertical macrocracks per linear inch (15.7-39.3 per 1 cm), measured along a line parallel to the surface of the substrate and lying in a plane perpendicular to the Nost substrate. The length of the plurality of vertical macrocracks should be at least half the thickness of the coating and reach the full thickness of the coating so that the cracks pass through at least 50 grains of the deposited powder.

In many cases of using a coating, its density should preferably be from 90% to 98% of theoretical, most preferably about 92% of theoretical density. Vertical macrocracks are formed in the coating by plasma coating of the coating powders on the substrate surface in separate monolayers in which the thickness of each monolayer is formed by at least two overlapping grains of the deposited powder (about 0.16 mils (4 μm)) and preferably contains from about three to five grains of the deposited powder (from about 0.24 mils (6 microns) and 0.40 mils (10.2 microns, respectively).

Without being bound by a specific theory, it is believed that the result of the deposition of two or more overlapping grains of powder is that the second and subsequent grains precipitate at a higher temperature than the previous ones. The reason for this is that the first grain of the powder is deposited on a relatively colder substrate, while the second and subsequent grains are deposited on the previous grains, the temperature of which increases more and more. Thus, the deposition of two or more grains as a whole leads to the creation of a temperature gradient, i.e. temperature rises to the top surface. During cooling and curing of the deposited monolayer, the second and subsequent grains shrink more than the previous grains, resulting in the formation of vertical macrocracks intersecting the deposited layer.

When additional overlapping monolayers are deposited on the substrate, vertical macrocracks are formed in each monolayer, which tend to be located in the same way as previously formed macrocracks in previous monolayers. Thus, in essence, several macrocracks are formed that extend essentially over the entire thickness of the coating. Width of vertical macrocracks, i.e. the distance between opposing sides forming a vertical macrocrack is typically less than about 1 mils (25.4 microns), preferably less than ½ mils (12.7 microns).

If the coating density is less than 88% of theoretical, the stress created by the shrinkage of the grains in a monolayer can be amortized or compensated by the porosity of the coating. This effectively prevents the formation of macrocracks over the entire coating, as would be necessary in accordance with the present invention, and prevents the formation of a coating with adequate thermal fatigue resistance. The substantially uniform distribution of vertical macrocracks over the entire coating, necessary in the context of the present invention, can reduce the modulus of elasticity of the coating and, therefore, reduce local stress. As a result, the coating acquires the proper resistance to thermal fatigue, i.e. the ability to function smoothly under cyclic thermal loads.

The density of vertical macrocracks should preferably be 20 or more, most preferably 40 or more vertical macrocracks per linear inch (respectively 7.9 or more, 15.7 or more per 1 cm), measured in the plane of the cross section of the coating along a line parallel to the surface of the substrate . This ensures that there are as many macrocracks in the coating as are sufficient to provide adequate resistance to thermal fatigue. To obtain the desired number of vertical macrocracks in a given coating, the plasma device must have high efficiency and stability throughout the entire coating period. The spray gun must be located at a fixed distance from the substrate, the speed of the burner relative to the substrate must be adjusted so as to ensure that the monolayer applied by the burner at a time is sufficient to overlap the deposited powder grains, for which, for the reasons stated above, the second and subsequent precipitated grains have a higher temperature than grains precipitated previously.

The total coating thickness may vary depending on the purpose of the product. For gas turbine engine parts, the coating thickness can vary from 0.0025 to 0.10 inches (63.5-2540 microns). A preferred zirconia partially stabilized yttrium oxide is a powder containing 6-8% by weight. yttrium oxide and the rest is zirconium oxide, most preferably about 7% by weight. yttrium oxide and the rest is zirconium oxide. The thermal barrier coatings of the present invention are ideally suited for use as a topcoat on a substrate having a metal bonding coating, namely blades, guiding devices, and gas turbine engine seals. A preferred metal bonding coating comprises (i) an alloy of chromium, aluminum, yttrium with a metal selected from the group consisting of nickel, cobalt and iron, or (ii) an alloy of aluminum and nickel. This binder coating may be applied by a conventional plasma spraying method or by any other conventional method. The substrate may be any suitable material, such as an alloy based on nickel, cobalt or iron.

The thermal barrier coatings of the present invention can be further stabilized by heat treatment in vacuum or in air at a temperature of 1000 ° C or higher. As described in more detail in Example 7 below, the threshold CPI value corresponding to excellent thermal shock resistance was reduced from 20 CPI (7.9 per 1 cm) for coatings of conventional ZrO-137 powder to about 5 CPI (2 per 1 cm) for coatings from the new high-purity powder ZrO-300. One of the embodiments of the present invention is the coating of high-purity powder ZrO-300 with a structure with a safe level of CPI and then heat treatment of the coated product.

The thermal barrier coatings of the present invention are highly heat-resistant and suitable for long-term service at high temperatures, under cyclic temperature loads, for example, as applied to parts of aircraft engines, industrial gas turbines, back rolls of steel and glass annealing lines, etc. . Typically, thermal barrier coatings after application have a high density (e.g., about 88% or more of theoretical density), a tetragonal crystallographic structure with no monoclinic phase, and have about 5 to about 200 vertical crack segments extending across the entire thickness of the coating. Thermal barrier coatings are heat resistant even when applied with a thickness of 2 mm or more.

As indicated above, the present invention relates to a method for producing creating a thermal barrier coating, including

a) thermal precipitation of a high purity yttrium or ytterbium oxide zirconia powder, wherein the powder contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest is zirconium oxide on the substrate to form a monolayer having at least two superimposed grains of powder deposited on the substrate, the temperature of the later deposited grain being higher than the previously deposited grain;

b) cooling and curing the specified monolayer obtained in stage a), after which the specified monolayer acquires a density of at least 88% of the theoretical density and in which as a result of the shrinkage of the deposited grains many vertical macrocracks form;

c) repeating steps a) and b) at least once in order to obtain a layer with a full surface coating, in which each monolayer has vertical cracks passing through the grains, and in which many vertical cracks of each monolayer are directed in the same way as vertical cracks in an adjacent monolayer, with the formation of vertical macrocracks with a length of at least half the coating thickness and reaching a length of the full coating thickness, where the applied layer is characterized by the presence of at least 5, preferably necks least 20 vertical macrocracks per linear inch (or 2, preferably 7.9 to 1 cm), measured along a line parallel to the substrate surface and lying in a plane perpendicular to the substrate surface.

The present invention relates to a thermal spraying method, comprising thermally depositing a high purity yttrium or ytterbium oxide zirconia powder, wherein the powder contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest - zirconium oxide, on the substrate to obtain a coating with vertical segments of cracks distributed essentially over the entire thickness of the coating, characterized by the presence of from about 5 to about 200 cracks per linear inch (2-78.7 per 1 cm ), measured along a line parallel to the coating plane, and the presence of a horizontal crack structure, which is sufficient to reduce thermal conductivity to less than 0.012 W / cm at 25 ° C over the entire thickness of the coating.

In the thermal spraying method of the present invention, the number of horizontal cracks can be adjusted to reduce the thermal conductivity of the applied layer. The structure of horizontal cracks caused by thermal spraying of coatings is uniform over the entire thickness of the coating and expressed as the sum of the segments of horizontal cracks along any line parallel to the plane of the coating in a polished cross-section is at least 25% of the coating width; such a structure can be stabilized by optional heat treatment in vacuum or in air at a temperature of 1000 ° C or higher.

The present invention relates to a method of thermal spraying, including thermal deposition of a high-purity yttrium or ytterbium oxide zirconia powder, wherein the powder contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest - zirconium oxide, on the substrate to obtain a coating with vertical segments of cracks distributed essentially over the entire thickness of the coating, characterized by the presence of from about 5 to about 200 cracks per linear inch (2-78.7 per 1 cm ), measured along a line parallel to the plane of the coating, and having a thickness of from about 5 to about 200 mils (127-5080 microns); and having a final surface layer formed from said high purity zirconia powder stabilized with yttrium or ytterbium oxides up to about 5 mils (127 μm) thick with essentially zero segmentation by vertical cracks.

The present invention relates to a method of thermal spraying, including thermal deposition of a high-purity yttrium or ytterbium oxide zirconia powder, wherein the powder contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest - zirconium oxide, on the substrate to obtain a coating with vertical segments of cracks distributed essentially over the entire thickness of the coating, characterized by the presence of from about 5 to about 200 cracks per linear inch (2-78.7 per 1 cm ), measured along a line parallel to the plane of the coating, and having a thickness of from about 5 to about 200 mils (127-5080 microns); and having a final surface layer comprising a ceramic frit coating obtained by immersion or spraying a solution of a thickness of up to about 5 mils (127 μm); and high temperature treatment of the surface layer with hot air to bind and fix the surface layer.

In the above thermal spraying method, a frit layer is applied by non-thermal spraying or by thermal spraying of a powder, which is a mixture of oxides, including silicon oxide, aluminum oxide and oxides of nickel, chromium, magnesium, copper, calcium and iron.

The methods of the present invention can be carried out using a plasma torch operating on a gas mixture of argon-hydrogen or nitrogen-hydrogen, or using a detonation gun or device operating on a gas mixture of oxygen-acetylene or oxygen-acetylene-propylene.

The present invention relates to thermal barrier coating products, wherein the thermal barrier coating comprises a thermal spray coating of a high purity yttrium or ytterbium oxide stabilized zirconia powder, where a high purity yttrium or ytterbium oxide stabilized zirconia powder contains from about 0 to about 0.15% weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest is zirconium oxide.

The present invention relates to products with a thermal barrier coating containing zirconium oxide, partially stabilized with yttrium or ytterbium oxides, having a density of more than 88% theoretical and having many vertical macrocracks substantially uniformly distributed over the entire coating, in which the cross section is perpendicular to the substrate opens up many vertical macrocracks extending at least half the thickness of the coating and reaching a length equal to the full thickness along covering, and which has from about 5 to about 200 (2-78.7 per 1 cm), preferably from about 20 to about 200 (7.9-78.7 per 1 cm), more preferably from about 40 to about 100 vertical macrocracks per linear inch (15.7-39.3 per 1 cm), measured along a line parallel to the surface of the substrate and lying in a plane perpendicular to the surface of the substrate, where the thermal barrier coating is formed by thermal spray coating of a high-purity powder stabilized with yttrium oxides or ytterbium zirconium oxide where you the high-purity zirconium oxide stabilized yttrium or ytterbium oxide powder contains from about 0 to about 0.15% by weight. impurity oxides, from about 0 to about 2% weight. hafnium oxide, from about 6 to about 25% weight. yttrium oxide or from about 10 to about 36% weight. ytterbium oxide and the rest is zirconium oxide.

Thermally sprayed coatings of articles of the present invention can be further stabilized by heat treatment in a vacuum or in air at a temperature of 1000 ° C. or higher. As described in more detail in Example 7 below, the threshold CPI value corresponding to excellent thermal shock resistance was reduced from 20 CPI (7.9 per 1 cm) for coatings of conventional ZrO-137 powder to about 5 CPI (2 per 1 cm) for coatings from the new high-purity powder ZrO-300. One of the embodiments of the present invention is the coating of high-purity powder ZrO-300 with a structure with a safe level of CPI and then heat treatment of the coated product.

Examples of products that can be coated in accordance with the present invention include turbine blades or guides made of an alloy based on nickel or cobalt, which are first coated with a metal binder, and then a layer of said thermal barrier coating, when this creates a thermal barrier coating has a thickness of from about 5 to about 25 mils (127-635 μm) and the structure of the vertical segments of the cracks, characterized by the presence of from about 5 to about 200 tre tire per linear inch (2-78.7 per 1 cm), measured in a polished cross-section in a direction parallel to the surface of the coating, taking into account those cracks whose length is at least half the thickness of the coating.

Other products include turbine engine combustion chambers made of nickel or cobalt-based alloy, which are first coated with a metal binder, and then a layer of said thermal barrier coating, the thermal barrier coating being about 5 to about 200 mils thick. (127-5080 μm) and the structure of the vertical segments of the cracks, characterized by the presence of from about 5 to about 200 cracks per linear inch (2-78.7 per 1 cm), measured in a polished cross section in the direction parallel to the surface of the coating, taking into account those cracks whose length is at least half the thickness of the coating.

Other products include air seal segments or a turbine engine air seal ring made of nickel or cobalt-based alloy, on which a metal bonding coating is applied, and then a layer of said thermal barrier coating, wherein the thermal barrier coating has a thickness of about 5 to about 150 mils (127-3175 μm) and the structure of the vertical segments of the cracks, characterized by the presence of from about 5 to about 200 cracks per linear inch (2-78.7 per 1 cm), measuring my in the polished cross section in a direction parallel to the coating surface, given the crack length which is at least half the thickness of the coating.

Other products include turbine or compressor blades made of nickel or cobalt-based alloy that are first coated with a metal binder and then coated with a thermal barrier coating layer, the thermal barrier coating being about 5 to about 45 mils thick (127-1143 μm) and the structure of the vertical segments of the cracks, characterized by the presence of from about 5 to about 200 cracks per linear inch (2-78.7 per 1 cm), measured in a polished cross section in the direction -parallel surface coating, considering the fracture length which is at least half the thickness of the coating.

Other products include cylinders or transport rolls of steel and glass annealing lines, which are first coated with a metal bonding coating, and then a layer of said thermal barrier coating, the thermal barrier coating being about 5 to about 45 mils thick (127-1143 μm) and the structure of the vertical segments of the cracks, characterized by the presence of from about 5 to about 200 cracks per linear inch (2-78.7 per 1 cm), measured in a polished cross-section in a direction parallel to the surface along rytiya, considering the fracture length which is at least half the thickness of the coating.

Although preferred embodiments of the present invention have been described, it should be understood that in high purity yttrium or ytterbium oxide stabilized zirconia powders, coatings made from yttrium or ytterbium oxide stabilized zirconia powders and coating methods for use in substrates under cyclic thermal loads, various modifications can be made without departing from the spirit and scope of the present invention.

Example 1

Table A below shows the composition of a typical yttrium oxide stabilized zirconia powder (i.e., powder B) and a high purity yttrium oxide stabilized zirconia powder (i.e., powder A). Data on the composition of the usual powder obtained by melting and crushing are taken from its technical description and represent the maximum allowable values, while the analysis of a real batch usually gives values of 10-50% of the maximum. The composition of the new high-purity powder was obtained as a result of the analysis of five real batches, while for any batch only the maximum values are given. It is understood that in zirconia stabilized with yttrium oxide, yttrium oxide is from 6.5 to 8% by weight. and stabilizes the tetragonal phase in the structure of the material. The role of hafnium oxide is unknown, but it is usually present in an amount of about 1.5% by weight. From table A it can be seen that powder A is significantly purer than powder B, in terms of the content of undesirable impurities - aluminum oxide, silicon oxide, iron oxide, titanium oxide and magnesium oxide.

Table a The composition of the powders (% wt.) Powder B Powder A Zirconium oxide Rest Rest Yttrium oxide 6.5-8 6.5-8 Hafnium oxide 2.5 2.0 Aluminium oxide 0.7 0.001 Silica 1,5 0.011 Iron oxide 0.5 0.004 Titanium oxide 0.5 0.009 Magnesium oxide 0.3 0.002

The morphology / structure of the powder is an important characteristic of the high purity yttrium oxide stabilized zirconia powders of the present invention. The true density of the powder was determined by stereopyknometry. In accordance with this method, the volume of the container is accurately determined by measuring the volume of the gas filling it, a known mass of powder is added, and the volume of the container with the powder is determined. Based on this, the volume of the powder is calculated, and dividing the mass of the powder sample by its volume, the true density of the powder is obtained. Table B shows the results of determining the true density of powder B and powder A.

Table B True Powder Density Powder B Powder A 5.92 6.00 g / cm ³ 98 99 Percentage of Theoretical Density

The theoretical density given in Table B was calculated for the specific yttrium oxide content of the powder. The theoretical density was 6.05 g / cm ³ . The density of both powder A and powder B was very close to theoretical, which indicates a low internal porosity. Powder A was as dense as powder B, but small pores were found in the center of many particles on the polished section, the walls of which were thick and dense.

In addition, powder A had a finer composition compared to powder B. The method of measuring the particle size distribution of the powder is the Microtrac method, according to which a laser is used to determine the average diameter of individual particles in the stream along the detector. The tabulation of the results obtained using a laser for thousands and millions of particles makes it possible to more accurately determine the distribution of particle sizes than sieving, with a finer gradation of sizes. Using this method, it was determined that the average particle size of powder B is between 34 and 38 microns. Using the same method, it was determined that the average particle size of powder A is from 26 to 34 microns. This range of particle sizes provides better melting of the powder in the thermal spraying device.

It is believed that, due to its high purity, excellent morphology / structure, and finer particle size distribution, powder A has improved thermal spray properties, as described below.

Example 2

In this example, a plasma torch of the Praxair 1108 model was used, although it is possible to select the conditions for applying the desired coatings with other torches, for example, the Praxair detonation gun or the Praxair super-detonation gun, in which case the particle speed and temperature are even higher. In a Praxair 1108 plasma torch, plasma is created in an argon and hydrogen stream under the influence of an electric arc discharge between the electrode and the anode. The powder is transported by another argon stream and introduced above the arc discharge along the stream in order to use the full passage along the arc zone. You can change the parameters of these flows and electric current to determine their effect on the deposition rate of the coating.

Table C presents the composition of the powders used in this example for coating. Powder C is significantly cleaner than powder D, in terms of the content of undesirable impurities - aluminum oxide, silicon oxide, iron oxide, titanium oxide and magnesium oxide.

Table C The composition of the powders (% wt.) Powder D Powder C Zirconium oxide Rest Rest Yttrium oxide 6.93 7.41 Hafnium oxide 1,5 1,6 Aluminium oxide 0.2 0.001 Silica 0.1 0.008 Iron oxide 0.1 0.003 Titanium oxide 0.2 0.005 Magnesium oxide 0.2 0.002 Calcium oxide 0.1 0.003 All other oxides 0.3 0.1

The following parameters were used during deposition in the form of coatings of powder C and powder D: total gas flow rate of 220 cubic feet / hour (6.23 m ³ / h) (it consisted of 90 cubic feet / hour (2.549 m ³ / h) of argon in the burner, 90 cubic feet / hour (2.549 m ³ / h) of carrier gas powder (argon) and 40 cubic feet / hour (1.133 m ³ / h) auxiliary hydrogen), 500 cubic feet / hour (14, 16 m ³ / h) of coaxial shielding gas (argon), an arc discharge current of 170 A (i.e., approximately 80 V at approximately 13.6 kW). Comparison of powder D and powder C was made on the basis of the same initial conditions.

Figure 1 shows the deposition efficiency of these powders at a distance of 1 inch (25.4 mm) from the substrate to the burner on 3/8 inch (9.525 mm) square steel plates in both cases. For powder C (solid line in FIG. 1), the efficiency was noticeably higher than for powder D (dashed line in FIG. 1). Part of this improvement is due to a slightly smaller particle size of powder C, however, in part, this is probably due to the morphology / structure of powder C.

Figure 2 shows the measured density of coatings deposited at a distance of 1 inch (25.4 mm) from the substrate to the burner on 3/8 inch square steel plates (9.525 mm), in both cases for powder C (solid line) and powder D (dashed line) - with the initial parameters of the flow and current of the burner. For powder C, the density at the same powder feed rate was at least 1-2% higher. In addition, with an increase in the feed rate, it did not crumble as fast as the powder D. Such properties are believed to be explained by an improvement in the melting parameters and, possibly, because the powder C remains longer melted due to the smaller particle size and greater purity, respectively .

It was found that when moving to a greater than 1 inch (25.4 mm) distance to the burner, the deposition efficiency of powder C remained higher than powder D, which probably also indicates that it remains molten longer. The coating density at an increased distance to the burner was also higher than for powder D.

Example 3

An assessment was made of various parameters of the gas flow in the burner and power supply. In accordance with the conditions of the experiment developed for this experiment, the total gas flow ranged from 176 to 264 cubic feet / hour (5-7.48 m ³ / h), and the arc discharge current from 160 to 190 A (i.e., the power varied from 11.7 to 14.8 kW). It was found that reducing the total gas flow to 176 cubic feet / hour (5 m ³ / h) at 14.3 kW corresponds to the highest deposition efficiency, which is 10% higher than that shown in FIG. 1 for powder C. It is believed that under these conditions powder fractions with a higher melting point are involved, since particles passing through the arc zone are slightly inhibited and the enthalpy spent on melting increases. Perhaps everything is not so simple, since the condition of the highest power or enthalpy is not sufficient to obtain the highest deposition efficiency. A multivariate correlation analysis of the results of the experiment to determine the deposition efficiency showed an unexpected increase in efficiency with an increase in the burner current and a decrease with an increase in the total gas flow, however, the mutual influence of these two variables is also possible.

The effect of the deposition rate, the distance from the burner to the substrate and the velocity of the surface of the substrate relative to the burner on the formation of vertical cracks in the coating was evaluated. These variables were rationalized as a combined quantity called the monolayer height. The height of the monolayer is the instantaneous thickness of the coating deposited when the substrate moves under the burner nozzle. It combines the volume of material fed to the substrate (deposition rate) and the area over which this material is deposited, determined by the distance to the burner and the speed of movement of the substrate. It also depends on the spray angle of the stream exiting the nozzle, determined by the burner model and the total gas flow rate used in the experiment. The height of the monolayer is expressed in units of thickness, such as mils or microns.

It is believed that the residual stress of the coating is an extension in the plane of the coating and that this stress increases with the height of the monolayer. Figure 3 shows the dependence of the density of the vertical segments of the cracks (the number of cracks per linear inch (CPI) of the length of the polished coating cross section) on the height of the monolayer. For a coating of powder D deposited on a substrate in the form of a disk with a diameter of 1.0 inch (25.40 mm) (dashed line in Fig. 3), a linear dependence of crack formation on the height of the monolayer was found, but only after exceeding the threshold value of the height of the monolayer in approximately 0.12 mil (3.05 microns). For cases when the instantaneous coating thickness exceeds this value, the crack density increases in proportion to the height of the monolayer.

However, for a powder coating C deposited on a disk-shaped substrate with a diameter of 1.0 inch (25.40 mm) (solid line in FIG. 3), cracking begins at a completely different threshold value for the monolayer height, about 0.22 mils (5 , 59 μm). After that, the linear dependence on the height of the monolayer has approximately the same angle as before. Such a much higher threshold value for the height of the monolayer can be associated with the properties of the powder C. It is believed that a much higher degree of purity of the powder is the reason for the higher fracture resistance inherent in the coating. This may be due to the higher density of coatings obtained from powder C, however, higher fracture resistance can occur even at the same density as coatings of powder D.

It is believed that coatings of powder C with a higher density have increased erosion resistance. If thermal barrier coatings of this material are used, for example, in aircraft gas turbine engines, where they are usually exposed to dust from the runway and dust flying in the air, it is important that the coating has high erosion resistance.

Example 4

The impact of heat treatment of various coatings was evaluated. One of the effects considered was the transformation of the tetragonal crystal structure of the coating into a monoclinic one. For a coating of zirconia stabilized with 7% weight. yttrium oxide (YSZ), the equilibrium structure should be monoclinic and cubic, which is reflected in the equilibrium phase diagram shown in Fig.4. However, during plasma spraying by rapidly curing the completely molten yttrium oxide stabilized zirconia grains, a nonequilibrium tetragonal structure was obtained. In order to allow reverse transformation into an equilibrium structure, separation into equilibrium phases with a low content of yttrium oxide and a high content of yttrium oxide as a result of high-temperature chemical diffusion, as shown in Fig. 4, is necessary. See Bratton and Lau, Science & Technology of Zirconia, Amer. Ceram. Soc., 1981, p. 226-240. The phase with a low content of yttrium oxide can then transform at about 1000-1200 ° C from high temperature tetragonal to low temperature monoclinic. In fact, such a transformation is undesirable, since the replacement of the tetragonal phase with the monoclinic phase during cooling of the ceramics can lead to an increase in volume by about 4% and, as a result, to the appearance of a large internal stress causing cracking.

In a material with such a high melting point as zirconium oxide, diffusion occurs very slowly, therefore, despite what should have been in accordance with the equilibrium phase diagram, the nonequilibrium tetragonal phase is preserved. As the engines improve in the direction of increasing the operating temperature, it is clear that in conventional YSZ coatings, partial transformation into the monoclinic phase can begin.

This effect of heat treatment was studied on a matrix of temperature and exposure times in air, as shown in Table E. The samples were separate test samples of a coating of a high-purity yttrium oxide stabilized zirconia powder (i.e. ZrO-300), and a conventional yttrium oxide stabilized zirconia powder coating (i.e., ZrO-137). Table D shows the typical compositions of the powders used for the manufacture of coatings. Three to four samples of each coating were heat treated with the same load, and density measurements were also taken to study the effect of sintering, which is described in detail in Example 5 below. The flat samples were squares with a side of about 0.38 inches (9.65 mm) 25 mils (0.635 mm) thick. Coatings were applied to these samples in the same manner as described in Example 3 above.

Table D The composition of the powders (% wt.) ZrO-137 ZrO-300 Zirconium oxide Rest Rest Yttrium oxide 7.39 7.58 Hafnium oxide 1,5 1,6 Aluminium oxide 0.2 0.001 Silica 0.1 0.008 Iron oxide 0.1 0.003 Titanium oxide 0.2 0.005 Magnesium oxide 0.2 0.002 Calcium oxide 0.1 0.003 All other oxides 0.3 0.1

As a result of X-ray diffraction analysis, a monoclinic phase was detected with peaks at 28 and 31.3 ° “2-theta” for copper radiation, while the peak of the tetragonal phase corresponds to approximately 30 °. Figure 5 presents the spectrum of x-ray diffraction analysis using K-alpha radiation of copper for coating from a conventional ZrO-137 powder after it is kept for 100 hours in air at 1400 ° C. The initial strict tetragonal structure was transformed into a 19.4% monoclinic structure. Figure 6 presents the spectrum of x-ray diffraction analysis using K-alpha radiation of copper for coating from a new high-purity powder ZrO-300 after it was kept for 100 hours in air at 1400 ° C. The initial strict tetragonal structure after 100 hours at 1400 ° C did not change.

The ratio of peak heights of 28 ° to the sum of peak heights of 28 and 30 ° was used to estimate the fraction of the monoclinic phase. This method of the "first monoclinic peak" was debugged by calibration on known mixtures of pure zirconium oxide with a monoclinic structure and powders with a tetragonal structure. Table E shows the results of thermal effects on a conventional coating of ZrO-137 powder and on coatings of a new high-purity ZrO-300 powder. In conventional coatings of ZrO-137 powder, the transformation into the monoclinic phase began at 1200 ° C. At 1400 ° C, the transformation proceeded much faster; its speed increased over time. At the same time and temperature values in the coating of the new high-purity ZrO-300 powder, no transformation occurred. Thus, it is clear that impurities in the ceramic material act as transformation nuclei, or they accelerate the diffusion of yttrium oxide and facilitate the attainment of an equilibrium state.

Table E The share of the monoclinic phase in the coatings
(method of the first monoclinic peak) Coating of Impact ZrO-137 powder ZrO-300 powder Immediately after application 0 0 100 hours at 1200 ° C 0.72 0 100 hours at 1300 ° C 1.01 0 24 hours at 1400 ° C 1,04 0 75 hours at 1400 ° C 11.34 0 100 hours at 1400 ° C 19.42 0

Example 5

The sintering of coatings from the new high-purity powder ZrO-300 of Example 4 at 1200 ° C was investigated. The results show that after 24 hours at a temperature of 1200 ° C, the density increases by less than 0.4%.

Another set of coating samples was made from a high purity yttrium oxide stabilized zirconia powder (i.e. ZrO-300), which was heated from 1200 to 1400 ° C in air for 100 hours. Coatings were applied to the samples in the same manner as in Example 3 above. For comparison, a set of coating samples was prepared from a conventional yttrium oxide stabilized zirconia powder (i.e., ZrO-137). Table F shows the typical compositions of the powders used for the manufacture of coatings.

Table F The composition of the powders (% wt.) ZrO-137 ZrO-300 Zirconium oxide Rest Rest Yttrium oxide 7.39 7.58 Hafnium oxide 1,5 1,6 Aluminium oxide 0.2 0.001 Silica 0.1 0.008 Iron oxide 0.1 0.003 Titanium oxide 0.2 0.005 Magnesium oxide 0.2 0.002 Calcium oxide 0.1 0.003 All other oxides 0.3 0.1

Density measurements for these samples were carried out by the immersion method in accordance with ASTM B-328, the results obtained, expressed as a percentage of the theoretical density (i.e., dense material without pores), are presented in Table G. All coatings were applied to the same cage an internal diameter of 11 inches (279.4 mm) and carefully removed to obtain separate samples.

Table g Density of coating after sintering in air
(as a percentage of theoretical density) Coating of Impact ZrO-137 powder ZrO-300 powder Immediately after application 91.49 92.69 24 hours at 1200 ° C 91.68 93.12 100 hours at 1200 ° C 91.70 93.07 1 hour at 1300 ° C 92.02 93.23 24 hours at 1300 ° C 89.50 93.28 100 hours at 1300 ° C 85.73 93.51 1 hour at 1400 ° C 89.52 93.03 24 hours at 1400 ° C 82.12 93.43 100 hours at 1400 ° C 80.33 93.34

As can be seen from the results obtained, the sintering of a coating of ordinary ZrO-137 powder was limited to a temperature of about 1200 ° C, after which a noticeable change in density was not noted. In fact, as the temperature increased from 1300 to 1400 ° C, the density of the coating of ordinary ZrO-137 powder decreased over time. Bearing in mind that a monoclinic phase was detected in the sintered coating of ZrO-137 powder and that the monoclinic phase is characterized by a lower density of the crystal structure, it was concluded that this is the reason for the decrease in density. It was found that this effect is negligible. In the worst case, 100 hours at 1400 ° C, when the monoclinic phase fraction was 19.42%, the density from 80.33% under the influence of monoclinic compensation changed only to 80.97%, as can be seen from table G.

Samples sintered at 1400 ° C were fixed and polished in order to study the changes. It was found that in a conventional coating of ZrO-137 powder, a decrease in density was real, i.e. small pores that were in the coating structure immediately after application, under the influence of a temperature of 1400 ° C, became coarser and more rounded over time. It is very important that after 100 hours the vertical segmentation cracks disappeared.

The sintering process did not significantly affect the density of the coating of the new high-purity powder ZrO-300. The density measurement results are graphically presented in FIGS. 7 and 8, which compare the properties of coatings of conventional ZrO-137 powder and the new high-purity ZrO-300 powder. Figure 7 graphically shows the dependence of the density of the coating of conventional ZrO-137 powder on time at a temperature of from 1200 ° C to 1400 ° C in air. The coating density after application (dotted with short strokes) was 91.5% of the theoretical. This fraction still decreased at 1300 ° C (solid line) and 1400 ° C (dotted line with long strokes). On Fig graphically presents the dependence of the density of the coating of the new high-purity powder ZrO-300 from time to time at a temperature of from 1200 ° C to 1400 ° C in air. The coating density after application (dashed line) was 92.7% of theoretical. After aging for at least 100 hours at 1400 ° C (solid line), this fraction did not change.

Samples of the ZrO-300 powder coating sintered at 1400 ° C were also fixed and polished. The porosity of these samples only slightly changed over time. Most importantly, up to 100 hours of vertical segmentation cracks have not substantially changed.

Example 6

US Pat. No. 5,073,433 describes thermally sprayed coatings, the introduction of which vertical segments of cracks can be controlled. This can be easily seen on the polished cross section of the coating. Segmentation cracks typically extend vertically through the entire thickness of the coating, although some are shorter than the total thickness of the coating. As described in US patent No. 5073433, only those vertical cracks were taken into account, the length of which exceeded half the thickness of the coating. When creating a coating of YSZ with a density of crack segments exceeding 20 cracks per linear inch (CPI) (7.9 per cm), measured along a line parallel to the substrate, such a coating had noticeably greater heat resistance. The same vertical segmentation cracks can be controllably introduced into the coatings of the present invention from high purity ZrO-300 powder.

The polished section microstructure also has another characteristic of interest, namely horizontal cracks. They are parallel to the coating plane and the coating layers applied during thermal spraying in several passes. Horizontal cracks, usually short ones, can be insulated in the coating or take the form of branches connecting vertical segmentation cracks. It is believed that such horizontal cracks can initiate the initiation of long separation cracks that increase in length under cyclic thermal loads, which is, in the worst case, the cause of cleavage of the YSZ coating layer.

A set of coating samples was prepared from a high purity yttrium oxide stabilized zirconia powder (i.e. ZrO-300) and a regular yttrium oxide stabilized zirconia powder (i.e. ZrO-137). Coatings were applied in the same manner as in Example 4 above. Table H shows the characteristic compositions of the powders used for the manufacture of coatings.

Table H The composition of the powders (% wt.) ZrO-137 ZrO-300 Zirconium oxide Rest Rest Yttrium oxide 7.39 7.58 Hafnium oxide 1,5 1,6 Aluminium oxide 0.2 0.001 Silica 0.1 0.008 Iron oxide 0.1 0.003 Titanium oxide 0.2 0.005 Magnesium oxide 0.2 0.002 Calcium oxide 0.1 0.003 All other oxides 0.3 0.1

For these coatings, the extent of horizontal cracks was measured. The length of any horizontal crack in contact with two accounted for vertical segmentation cracks was measured. In the context of the present invention, such cracks are called “breaking”. The sum of the lengths of all cracks qualified as “breaking”, divided by the total estimated coating width, represents the “breaking percentage”, i.e. a fraction of the width of the coating. For coatings made from the new high-purity ZrO-300 powder, the fracture percentage = 0.086 × CPI + 0.54. For coatings made from conventional ZrO-137 powder, break rate = 0.17 × CPI + 0.067. It was found that with an increase in the density of vertical segmentation cracks (CPI), the fracture percentage (% Bk) also increases. Figure 9 presents a graph obtained by studying vertical and horizontal cracking cracks in a number of coatings in which a different number of vertical cracks (CPI) was specially created. The relationship between horizontal and vertical cracks turned out to be linear; for him, the equation connecting these variables can be obtained using the least squares method.

When working with the new high-purity ZrO-300 powder, aimed at the manufacture of coatings with segmentation cracks, unexpected results were obtained regarding horizontal breaking cracks. In the coating of the new high-purity ZrO-300 powder (dashed line in Fig. 9) with the same CPI (vertical cracks) there were about half as many cracking cracks as in the coating of ordinary ZrO-137 powder (solid line in Fig. 9) . It is believed that the coating of the new high-purity ZrO-300 powder has a higher internal cohesive strength.

Example 7

It has been found that having vertical segmentation cracking coatings described in US Pat. No. 5,074,433 can be used as thermal barrier coatings in many cases, from gas turbine engine parts to rolling mill rolls. Most often, thermal barrier coatings made of YSZ are applied to the outer side of the metal substrate facing a high-temperature medium, as a result of which, due to the heat-insulating properties of the coating, the temperature of the substrate decreases. Therefore, a temperature gradient exists in the coating creating the thermal barrier, the temperature is high on the open surface of the YSZ coating, and the temperature is lower on the coating side facing the substrate. In addition, the temperature effect can be cyclic when the entire part is subjected to alternately heating to high temperature and cooling, for example, in a gas turbine engine when starting and stopping.

Laboratory experiments were conducted to simulate the temperature gradient and cyclic conditions of such coating applications. In the context of this document, Jet Engine Thermal Simulation experiments are called “JETS Tests”. These tests are needed for experimental coatings to determine if they are suitable for the intended application. In laboratory tests, samples were used, which were a flat disk with a diameter of 1 inch (25.4 mm), a thickness of about 1/8 inch (3.2 mm), made, as a rule, of superalloy. A metal binder coating was applied to the substrate by thermal spraying (for example, CoNiCrAlY binder coating), after which a YSZ thermal barrier coating was applied. Coatings with different YSZ layer thicknesses and with different crack segment structure (CPI) were tested. Coated disks were placed opposite the nozzle of the burner operating on an oxygen / propylene mixture, as a result of which the YSZ surface was heated to 1400 ° C (2550 ° F) in 20 s; each experiment also used a standard reference sample.

Fifteen additional disks were installed in a drum cage, which, after heating for another 20 s, was turned into a position in which cooling was carried out by an intense air stream. Then, the drum was rotated two more times to the position in which the cooling by ambient air was carried out, after which the heating-cooling cycle was repeated first. Typically, each sample went through 2,000 such cycles, after which the polished edge of the disk circumference was examined for signs of breaking cracks. For measurements, a 30-fold increase was used, any segments of cracks were measured and summed, and then expressed as a fraction of the circumference of the disk. Quite arbitrarily, a value of 15% of the marginal cracks was chosen as the threshold for samples that did not pass the JETS test. It is highly likely that a coating that has passed the JETS test will perform well in real conditions.

Coating samples were prepared from a high-purity yttrium oxide stabilized zirconia powder (i.e., ZrO-300), and, for comparison, a conventional yttrium oxide stabilized zirconia powder (i.e., ZrO-137). Coatings were applied to discs in the same manner as described in Example 4 above. Coatings from the new high-purity ZrO-300 powder were applied with a thickness of 25 mils (± 2 mils) (635 ± 50.8 μm) on a metal binder coating. The metal binder coating was CoNiCrAlY 8 mils thick (203.2 μm). The height of the monolayer was changed in order to study its effect on segmentation. Used for comparison, a coating of conventional ZrO-137 powder was applied with a thickness of 45 mils (1143 μm). Table I shows the characteristic compositions of the powders used for the manufacture of coatings.

Table I The composition of the powders (% wt.) ZrO-137 ZrO-300 Zirconium oxide Rest Rest Yttrium oxide 7.39 7.58 Hafnium oxide 1,5 1,6 Aluminium oxide 0.2 0.001 Silica 0.1 0.008 Iron oxide 0.1 0.003 Titanium oxide 0.2 0.005 Magnesium oxide 0.2 0.002 Calcium oxide 0.1 0.003 All other oxides 0.3 0.1

Using the JETS test for a coating of a new high-purity ZrO-300 powder and used for comparison of a coating of a conventional ZrO-137 powder, it was found that the performance of the coatings of a new high-purity ZrO-300 powder is better than coatings of a conventional ZrO-137 powder. Figure 10 shows the dependence of the fraction of edge cracks after 2000 JETS test cycles on the density of vertical segmentation cracks (in CPI) for these coatings. Coatings in which there were no segmentation cracks easily cracked and did not pass the tests. However, those coating samples from the new high-purity ZrO-300 powder, in which the number of cracks exceeded 10 CPI (4 per cm), passed the test. For coatings of conventional ZrO-137 powder, this threshold was about 20 CPI (7.9 per 1 cm).

Another important discovery of the present invention relates to the heat treatment of ZrO-300 powder coatings before the JETS test. The heat treatment consisted of heating in vacuum at a step of 25 ° C per minute to 1080 ° C (1975 ° F), holding for 4 hours and cooling in vacuum at a step of 25 ° C per minute. Figure 11 presents the test results of JETS samples subjected to heat treatment. The CPI of the coatings was measured before heat treatment using the method described above using the appropriate discs and polished cross section. The performance of heat-treated coatings of high-purity powder turned out to be better than that of samples without treatment. The threshold CPI value, corresponding to excellent thermal shock resistance, was even below 10 CPI (4 per 1 cm). Thus, one of the conclusions of the present invention is the coating of highly pure ZrO-300 powder with a structure with a safe CPI level and then heat treatment of the coated product. This heat treatment is one of many changes leading to a better result.

Although preferred embodiments of the present invention are described herein, it should be understood that in high purity yttrium or ytterbium oxide stabilized zirconia powders, coatings made from yttrium or ytterbium oxide stabilized zirconia powders and coating methods for substrates intended for operation under cyclic thermal loads, various modifications can be made that do not go beyond the essence and scope of this invention.

Claims (15)

1. High purity yttrium or ytterbium oxide stabilized zirconia powder containing from about 0 to about 0.15 wt.% Impurity oxides, from about 0 to about 2 wt.% Hafnium oxide, from about 6 to about 25 wt.% Oxide yttrium or from about 10 to about 36 wt.% ytterbium oxide and the rest is zirconia, in which impurity oxides include from about 0 to about 0.02 wt.% silicon dioxide, from about 0 to about 0.005 wt.% alumina, from about 0 to about 0.01 wt.% calcium oxide, from about 0 to about 0.01 wt.% iron (III) oxide, from about 0 to about 0.005 wt.% magnesium oxide and from about 0 to about 0.01 wt.% titanium dioxide. 2. The high purity yttrium or ytterbium oxide stabilized zirconia powder according to claim 1, wherein the particle size is from about 1 to about 150 microns. 3. The high purity yttrium or ytterbium oxide stabilized zirconia oxide powder according to claim 1, comprising a mixture of two or more high purity yttrium or ytterbium oxide zirconia powder. 4. The high-purity yttrium or ytterbium oxide stabilized zirconia oxide powder according to claim 1, containing from about 55 to about 95 vol% of the first high-purity zirconium oxide powder partially stabilized by yttrium or ytterbium oxides, containing from about 0 to about 0.15 wt.% impurity oxides, from about 0 to about 2 wt.% hafnium oxide, from about 6 to about 8 wt.% yttrium oxide or from about 10 to about 14 wt.% ytterbium oxide and the rest is zirconium oxide, and from about 5 to about 45 vol.% Second high purity powder zirconium oxide fully stabilized with yttrium or ytterbium oxides containing from about 0 to about 0.15 wt.% impurity oxides, from about 0 to about 2 wt.% hafnium oxide, from about 16 to about 22 wt.% yttrium oxide or from about 25 to about 33 wt.% ytterbium oxide and the rest is zirconium oxide. 5. The composite high-purity powder of zirconium oxide stabilized by yttrium or ytterbium oxides, containing the high-purity powder of zirconium oxide stabilized by yttrium or ytterbium oxides according to claim 1, which has a nominal average particle size of 20-60 μm, to the surface of which gadolinium oxide particles are bonded with nominal average size of 0.5-2 microns. 6. The thermal spray coating of a high-purity yttrium or ytterbium oxide stabilized zirconia powder according to claim 1 for application to a substrate. 7. The thermal spray coating of claim 6, having a density of more than 88% of theoretical density and a plurality of vertical macrocracks substantially uniformly distributed throughout the coating, in which a cross section perpendicular to the substrate opens up a plurality of vertical macrocracks extending at least half the thickness of the coating and reaching a length equal to the total thickness of the coating, and which has from about 5 to about 200 vertical macrocracks per linear inch (2-78.7 per cm), measured about a line parallel to the surface of the substrate and lying in a plane perpendicular to the surface of the substrate. 8. The thermal spray coating of claim 6, wherein there is at least about 20 vertical macrocracks per linear inch (7.9 per cm), measured along a line parallel to the surface of the substrate and lying in a plane perpendicular to the surface of the substrate, and one or more horizontal macrocracks extending in the coating parallel to the surface of the substrate. 9. The thermal spray coating according to claim 6, wherein a binder coating is applied between the substrate and the thermal spray coating, comprising (i) an alloy of chromium, aluminum, yttrium with a metal selected from the group consisting of nickel, cobalt and iron, ( ii) an alloy of aluminum and nickel; or (iii) a coating of MCrAlY + X, applied by plasma spraying, by detonation spraying, or by electrodeposition, where M is Ni, Co or Fe, or any combination of these three elements, X is the addition of Pt, Ta, Hf , Re or other rare earth nyh metal particles or fine alumina - dispersing agent, alone or in combination. 10. The thermal spray coating of claim 6, stabilized by heat treatment in a vacuum or in air at a temperature of 1000 ° C or higher. 11. A method of obtaining a thermal barrier coating, comprising
a) thermal deposition of a high-purity yttrium or ytterbium oxide zirconia powder according to claim 1 on a substrate to form a monolayer having at least two superimposed grains of powder deposited on the substrate, the temperature of the later deposited grain being higher than the previously deposited grain;
b) cooling and curing the specified monolayer obtained in stage a), after which the specified monolayer acquires a density of at least 88% of the theoretical density, and in which as a result of the shrinkage of the deposited grains many vertical macrocracks form;
c) repeating steps a) and b) at least once in order to obtain a layer with a full coating, in which each monolayer has vertical cracks passing through the grains, and in which many vertical cracks of each monolayer are directed in the same way vertical cracks of an adjacent monolayer, with the formation of vertical macrocracks at least half the thickness of the coating and reaching the full thickness of the coating in length, and the applied layer is characterized by the presence of at least 5 vertical macrocracks on the line th inch (2 cm) as measured along a line parallel to the substrate surface and lying in a plane perpendicular to the substrate surface. 12. The method of thermal spraying, including thermal deposition of a high-purity powder of zirconium oxide stabilized with yttrium or ytterbium oxides, according to claim 1 on a substrate with the formation of a coating with vertical segments of cracks passing essentially through the entire thickness of the coating, which has from about 5 up to 200 cracks per linear inch (2-78.7 per cm), measured along a line parallel to the coating plane, and the structure of the horizontal cracks of which is sufficient to reduce thermal conductivity to less than 0.012 W / cm at 25 ° C across the coating thickness where the structure of horizontal cracks is uniform across the thickness of the coating and, expressed as the sum of the segments of horizontal cracks along any line parallel to the plane of the coating in a polished cross section, is at least 25% of the width of the coating; such a structure can be stabilized by optional heat treatment in vacuum or in air at a temperature of 1000 ° C or higher. 13. The method of thermal spraying, including thermal deposition of a high-purity powder of zirconium oxide stabilized with yttrium or ytterbium oxides, according to claim 1 on a substrate with the formation of a coating with vertical segments of cracks passing essentially through the entire thickness of the coating, which has from about 5 up to about 200 cracks per linear inch (2-78.7 per cm), measured along a line parallel to the plane of the coating, having a thickness of from about 5 to about 200 mils (127-5080 μm) and having (i) a final surface layer formed and the specified high-purity yttrium or ytterbium oxide zirconia powder up to 5 mils (127 μm) thick with essentially zero segmentation by vertical cracks or (ii) a final surface layer containing a ceramic frit coating obtained by immersion or spraying a solution of up to approximately 5 mils (127 μm); and high temperature treatment of the surface layer with hot air to bind and fix the surface layer. 14. Product with a thermal barrier coating containing zirconia partially stabilized with yttrium oxide or ytterbium oxide and having a density of more than 88% of theoretical density and many vertical macrocracks substantially uniformly distributed throughout the coating, in which a cross section perpendicular to the substrate , opens up many vertical macrocracks, extending at least half the thickness of the coating and reaching a length equal to the full thickness of the coating, and having about 5 to about 200 vertical macrocracks per linear inch (2-78.7 per cm), measured along a line parallel to the surface of the substrate and lying in a plane perpendicular to the surface of the substrate, where the thermal barrier coating is a thermal spray coating of high purity powder zirconium oxide stabilized with yttrium or ytterbium oxides according to claim 1. 15. The product of claim 14, comprising (i) a turbine blade or guide made of an alloy based on nickel or cobalt, on which a metal bonding coating is first applied, and then a layer of said coating creating a thermal barrier, the thickness of the thermal barrier coating is from about 5 to about 25 mils (127-635 microns), the structure of the vertical segments of the cracks contains from about 20 to about 100 cracks per linear inch (7.9-39.3 per cm), measured in a polished cross section in the direction couple the partial plane of the coating, taking into account cracks whose length is at least half the thickness of the coating, (ii) a turbine engine combustion chamber made of an alloy based on nickel or cobalt, on which a metal bonding coating is first applied, and then a layer of the specified thermal barrier coating, the thickness of the thermal barrier coating is from about 5 to about 200 mils (127-5080 microns), the structure of the vertical segments of the cracks contains from about 5 to about 200 cracks per linear an inch (2-78.7 per cm) measured in a polished cross-section in a direction parallel to the plane of the coating, taking into account cracks whose length is at least half the thickness of the coating, (iii) segments of the air seal or ring of the turbine air seal an engine made of an alloy based on nickel or cobalt, on which a metal bonding coating is first applied, and then a layer of said thermal barrier coating, the thickness of the thermal barrier coating is from about Roughly 5 to about 150 mils (127-3810 μm), the structure of the vertical crack segments contains from about 20 to about 100 cracks per linear inch (7.9-39.3 per cm), measured in a polished cross section in a direction parallel to the coating plane, taking into account those cracks whose length is at least half the coating thickness, (iv) a turbine or compressor blade made of an alloy based on nickel or cobalt, on which a metal bonding coating is first applied, and then a layer of the specified thermal bar coating coating, the thickness of the thermal barrier coating is from about 5 to about 45 mils (127-1143 μm), the structure of the vertical segments of the cracks contains from about 20 to about 100 cracks per linear inch (7.9-39.3 per cm) measured in a polished cross-section in a direction parallel to the plane of the coating, taking into account cracks whose length is at least half the thickness of the coating, or (v) a cylinder or a transport roll of steel and glass annealing lines, on which a metal binder is first coated e, and then a layer of said thermal barrier coating, the thickness of the thermal barrier coating is from about 5 to about 45 mils (127-1143 μm), the structure of the vertical segments from the cracks contains from about 20 to about 100 cracks per linear inch (7, 9-39.3 per cm), measured in a polished cross-section in a direction parallel to the plane of the coating, taking into account those cracks whose length is at least half the thickness of the coating.

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