The method of providing thermal protection and a metal product with a ceramic coating (options)
The invention relates to the field of metallurgy and can find application in the production of metal products coating, for example, turbine blades of gas turbine engines. The metal work is providing a thermal barrier ceramic coating containing oxides of gadolinium and zirconium. The material may have a structure of fluorite type or pyrochlore. The method includes the operation of applying ceramic primer before the application of the ceramic coating. Primer consisting of zirconium oxide stabilized with yttrium oxide, is between the metal matrix and ceramic coating. Ceramic coating is applied by a method selected from the group consisting of thermal spraying, sputtering and vacuum deposition. Products obtained by this method and the specified coating composition, capable of working in conditions of very high temperatures. 3 C. and 22 C.p. f-crystals, 16 Il, 2 PL.The technical field to which the invention relatesThe present invention relates to providing thermal protection with the use of ceramic coatings that creates a thermal barrier, and the metal parts or products, provided such software is repectfully ceramic material based on the use of gadolinium oxide and zirconium and has a cubic crystal structure.The level of technologyGas turbines are well-used machines for converting the chemical potential energy in the form of fuel into thermal energy and then into mechanical energy used to effect the movement of the aircraft, electric power generation, transmission fluid, etc. At the present time the main direction of further improvement of gas turbines is the use of higher operating temperatures. However, metal materials currently used in gas turbines under conditions approaching the upper limit of their thermal stability. In the hottest areas of modern gas turbines metallic materials are used at temperatures of gas in excess of the melting point of these materials. Materials work under such conditions due to air cooling. However, the use of air cooling reduces the efficiency of the installation.In this regard, held numerous development of coatings that creates a thermal barrier for use of these coatings in a cooled gas turbine equipment of the aircraft. Due to the use of such coating is Yunosti.Coatings of this type are always based on the use of ceramics. Although it was proposed to use mullite, alumina, and so on, the most preferred material is currently zirconium oxide (in the context of this description, the term "zirconium oxide" is used as a General term describing a zirconium compounds with oxygen, including the main form of zirconium dioxide). In order to prevent the formation of monoclinic phase Zirconia should be modified by means of the stabilizer, and typical stabilizers include the oxides of yttrium, calcium, cerium and magnesium.In General, the temperature coefficients of linear expansion (thermal expansion) of metallic materials is higher than that of ceramic materials. As a consequence, one of the problems that must be addressed in the process of successful development of coatings of this type, consists in matching coefficients of thermal expansion of the ceramic material and the metal matrix (substrate), so that when heated, when the matrix will be expanded, there was no cracking of the coating material. Zirconium oxide has a high coefficient of thermal expansion, and this is the main reason for his Developed various methods of coating, creates a thermal barrier, including thermal spraying (plasma, flame and using a high-speed beam oxygen fuel), sputtering and electron-beam physical vapour deposition (HALFOP). Among these methods currently preferred in critical applications is electron-beam physical vapour deposition (HALFOP), because it provides a unique structure of the coating. Ceramic materials, applied in this way, subject to maintaining certain parameters have a columnar microstructure grains, consisting of small columns, separated by gaps, passing through the thickness of the coating. These gaps make it possible for significant thermal expansion of the matrix without cracking and/or peeling of the coating (see, for example, U.S. patent No. 4321311 owned by the applicant of the present invention). According to U.S. patent No. 5073433 and U.S. patent 35705231, also owned by the applicant of the present invention, a similar structure (with discontinuities along the boundaries of the segmentation), but with a larger scale, can be obtained by plasma spraying.The inventionDespite the successes achieved with the use of coatings n is the openings, with improved ability to create a thermal barrier, especially if this ability is defined as normalized to the density of the coating. When designing a gas turbine plant mass is always a critical factor, especially for rotating parts. Ceramic coating that creates a thermal barrier, do not apply to materials, perceiving the load, so that their application increases the weight without increasing the strength. In this regard, there is an increased interest in ceramic material, which creates a thermal barrier with a minimum increase in weight, but with a maximum heat capacity. In addition, there is common interest in long-term service life, stability, efficiency, etc.Accordingly, the main task to be solved by the present invention is directed, is the development of ceramic coatings, providing a more effective thermal protection of metal products, especially designed for use at very high temperatures.Another problem solved by the present invention, is a method that provides reliable thermal protection the temperature.These, and other objectives which will become clear from the further discussion, decided, first of all, thanks to the creation of a method of providing thermal protection of the metal matrix by applying, on at least part of the matrix of the ceramic coating with a cubic crystal structure. The main distinctive feature of the method according to the present invention is the presence in the ceramic coating of the complex oxide of gadolinium and zirconium.The method according to the present invention preferably also includes the operation of applying ceramic primer, which is performed before the application of the ceramic coating, so that the primer consisting of zirconium oxide stabilized with yttrium oxide, is between the metal matrix and ceramic coating. This ceramic coating is preferably applied by a method selected from the group consisting of thermal spraying, sputtering and vacuum deposition.In the framework of the present invention it is also proposed metal matrix obtained by the method according to the present invention, i.e. having on their surface a ceramic coating formed by the oxides of gadolinium and zirconium it the structure of fluorite, while the amount of the coating material with the structure of the pyrochlore type does not exceed 10% of the full volume.The preferred content of gadolinium in the material of the ceramic coating according to the invention lies in the range of 5-60 mole %, with the remaining portion of the coating material is zirconium oxide.Ceramic coating made in accordance with the present invention has a columnar microstructure, and its coefficient of thermal conductivity is less than about 1 W/(mdeg.).According to one of preferred embodiments of the present invention on the outer surface of the metal matrix has an oxide film consisting essentially of aluminum oxide that provides good binding with ceramic coating. In addition to this film, or instead of a metal product according to the invention may contain ceramic primer disposed between the ceramic coating and the metal matrix. Ceramic primer preferably comprises zirconium oxide stabilized with yttrium oxide.Thus, the basic idea of the present invention stems from the discovery that a certain class keramicheskih matrices. Although some of these materials have a crystalline structure of pyrochlore, additional studies have demonstrated that another part of these materials, including gadolinium oxide - zirconium (hereinafter referred to mainly as (Gd, Zr)O2), which has a cubic structure (which is not a pyrochlore-structure), is also very useful for obtaining PSTB.The term "pyrochlore" is used to denote the tantalum ore, occurring in Canada. In a broader sense, this term is used to describe a ceramic structure having the composition of A2B2O7, where component a has a valency of 3+or 2+In can have a valence of 4+or 5+and the sum of the valences of a and b is equal to 7. Oxygen can be partially replaced by sulfur or fluorine. Typical pyrochlore, which appear to be potentially useful as coatings that creates a thermal barrier, are those in which component a is selected from the group consisting of lanthanum, gadolinium, yttrium and mixtures thereof, and selected from the group consisting of zirconium, hafnium, titanium or mixtures thereof. There are many other pyrochlore, which also have potential use as coatings of this type. Area included in this description by reference to it).When developing the present invention it was found that, with a correction for the density, is investigated pyrochlore have a higher heat-shielding properties than the more widely used materials for creating a thermal barrier on the basis of zirconium dioxide. In addition, many of the pyrochlore have such phase relation that the structure of pyrochlore is stored in them up to the melting point. Most of the pyrochlore investigated in connection with the development of the present invention has a melting point above 1550With, often above 2200C. Some of the materials having a cubic crystal structure, but in any case, not the pyrochlore structure, such as gadolinium oxide - zirconium (Gd, Zr)O2also have phase stability, at least until 1650C. in the case of gadolinium oxide - zirconium (Gd, Zr)O2any transition from pyrochlore structure, characteristic of lead zirconate gadolinium, tends to be normal cubic structure, which also has a high phase stability. In addition, all of these materials have good adhesion to aluminum oxide. All these properties is obreteniyu was developed for gas turbine units, it is adapted for use in conditions where the external surface of the ceramic coating will be subjected to heating, and free from coating the surface of the matrix will be cooled, while the ceramic coating will reduce the heat flow. The preferred materials of the matrix products of the present invention are steel, as well as special, titanium and copper alloys. In one embodiment, the product according to the invention is provided with a ceramic coating, which has a porosity of approximately 30-60% by volume.Metal product with a ceramic coating according to the present invention certainly has utility in other applications involving high temperatures, such as, for furnaces and internal combustion engines.List of drawingsEmbodiments of the present invention will be described in more detail below with reference to the accompanying drawings, in which:Fig.1A depicts the crystal structure of pyrochlore;Fig.1B depicts the crystal structure of fluorite, such as fully stabilized zirconium oxide;Fig.2 illustrates the correlation between the sizes of the ionic components a and b required for FMR is ical matrix;in Fig.3B presents ceramic coating on a metal matrix in the presence of primers;in Fig.3 in an enlarged scale presents an intermediate layer between the coating and the ceramic coating layer according to Fig.3B;in Fig.4 shows a phase diagram of ZrO2La2O3;Fig.5 graphically presents data on thermal conductivity of several ceramic materials;in Fig.6 graphically presents data on the coefficient of thermal expansion for several ceramic materials;in Fig.7 shows the spectrum of x-ray diffraction of the coating of ZrO2-La2O3,in Fig.8 shows the microstructure of gadolinium oxide - zirconium applied by the method of ALTOP;in Fig.9 shows the microstructure of gadolinium oxide - zirconium after heat treatment;in Fig.10 graphically compares thermal conductivity of monolithic samples of gadolinium oxide - Zirconia with cubic structure, and pattern of monolithic Zirconia stabilized with yttria (YSZ);in Fig.11 graphically a comparison between the conductivity of samples of thin layers of gadolinium oxide - zirconium and conventional oxide layer C is s;in Fig.13 shows another variant implementation of the present invention using ceramic primer.Information confirming the possibility of carrying out the invention the coating corresponding to the present invention are intended primarily for the protection of substrates from special alloys from excessively high temperatures. Special alloys are alloys of metals, primarily based on iron, Nickel or cobalt, chromium and aluminum, as well as, typically, titanium and refractory metals, and with useful properties at temperatures over 650C. Thermal protection may be required for other substrates, including steel, copper and titanium alloys. Typical examples of substrate materials are shown in table 1.Regardless of what structure has ceramics (other than the pyrochlore structure, such as a fluorite structure, and/or structure, including the structure of the pyrochlore), a critical factor as for other ceramic coatings that creates a thermal barrier, is the adhesion of the ceramic material to the alloy matrix.From experience of using the known coatings on the basis dioxide nazyvaemoi also overlay coating is a coating of metal, such as MCrAIY. It is also known that a useful method of obtaining primers is a method of diffusion plating to form aluminides (hereinafter this method for the sake of brevity will be referred to as also "diffusion elyuminirovanie"). A common feature of overlay coatings and coatings obtained by the method of diffusion plating, is that they form a surface film or scale aluminum oxide having good adhesion.The range of content components in materials such MCrAIY is 10-25% Cr, 5-15% of Al, 0.1 to 1.0% Y, and the rest Fe, Mi and Co, and a mixture of Ni and Co. May be additives in an amount up to 5% Hf, TA or Re, up to 1% Si, up to 3% Os, Pt, Pd, Rh. Examples of compositions MCrAIY, which can be applied using thermal spray techniques HALFOP, as well as by electrodeposition, are shown in table 2.Alternative primer can be applied by the method of diffusion plating the surface of the matrix. Coatings of this type are well known; for their application may be used a mixture containing a source of aluminum, for example, an alloy or a compound of aluminum, an activator (normally galogensoderjasimi connection, such as NaF), and inertness and heated to 815-1093With simultaneous blowing a carrier gas such as hydrogen. Also known variants of this method that does not involve immersion in the said mixture. It is also known introduction into the coating by diffusion elyuminirovanie, noble metals such as Pt. Rh, Pd and Os. Methods diffusion plating to form aluminides are described, for example, in U.S. patent No. 5514482.You can also use the combination of the overlay coating diffusion elyuminirovanie. The system, which is used in the internal overlay coating of MCrAlY and the outer coating diffusion elyuminirovanie described in U.S. patent No. 4897315 owned by the applicant of the present invention. In U.S. patent No. 4005989, also owned by the applicant of the present invention, shows the reverse combination, namely the internal coating diffusion elyuminirovanie, and the outer overlay surface.A common characteristic of the above primers and their combinations is having on their outer surface layer of aluminum oxide, having high adhesion. Coating to create a thermal barrier according to the present invention are characterized by low solubility in aluminum oxide, n is exactly the quality and with good binding ability of a film of aluminum oxide, having good adhesion to ceramic materials - see belonging to the applicant of the present invention patents USA№4209348, №4719080, №4895201, №5034284, №5262245 and no 5346563 and No. 5538796.To date, all successful ways to deposition of ceramic coatings on special alloys included the formation of the oxide layer (usually aluminum oxide and rarely silicon) between the primer (or matrix) and ceramic coating.Hereinafter the present invention will be described with reference to the accompanying drawings.In Fig.1A shows the crystal structure of pyrochlore. The pyrochlore structure is a complex structure that can be described in various ways, for example, as a derivative structure of fluorite or as a grid of octahedra, connected to each other at their corners, with the interstices filled with ions. Regardless of the form of the description of this structure, it has the chemical formula And2In2O7or, in some cases, A2B2O6and the pyrochlore with such a structure is called defective. Presented on Fig.1A pyrochlore corresponds to the lanthanum lead zirconate formulas And2In2About7. In Fig.1B shows a cubic fluorite structure (i.e., n is the fluorite structure corresponds to the structure of the oxide of gadolinium - zirconium. When comparing Fig.1A and 1B are visible both similarities and differences of the pictured structures. Both figures represent the view of the crystal axis <100>. Visually, the pyrochlore structure is less regular than the structure of fluorite.In the pyrochlore components a and b may have different valence, provided that these valence in an amount equal to 7 (in the case of A2In2O7) or 6 (in the case of A2In2O6). Although all connections-pyrochlore included in this description are of the formula A2B2O7or a2In2O6not all compounds with formulas (including gadolinium oxide - zirconium, which will be described later) are pyrochlore. The pyrochlore structure is formed only when a certain ratio of the ionic radii of a and B. This relationship is illustrated in Fig.2, which summarizes the combinations of ionic radii a and b, which give the cubic pyrochlore structure. When creating the present invention discovered that the boundaries of this chart is quite uncertain, and it seems that the titanate lanthanum (La2Ti2O7) has a stable cubic pyrochlore structure. Known pirkle rumichaca materials with cubic pyrochlore structure.As shown in Fig.2, the formation of the desired cubic pyrochlore structure is defined relative ionic radii of the components a and B. for Example, Fig.2 one can see that as Gd2Ti2O7and Y2Zr2O7will have a cubic pyrochlore structure. In General, compounds of formula (GdxYy)(TiaZrb)O7where x+y=2 and a+b=2, will also have a cubic pyrochlore structure. Further, compounds having neobichnuyu structure, such as Ln2Zr2O7this structure with a certain probability can be given partial substitution aimed at bringing the average ionic radii in the region of the cubic pyrochlore structure shown in Fig.2, for example, the substitution of Nd for Ln and/or Ti to Zr.The gadolinium oxide - zirconium is a weak driver of the pyrochlore structure. It corresponds to the region R in Fig.2 bounded by dashed lines, however, the ionic radii of gadolinium and zirconium are relatively large, i.e., lie close to the edge of the region R. Recent studies have shown that the oxides of gadolinium and zirconium prepared in such proportions and at such temperature that, as expected, lead to the structure of pyrochlore, detect which of klarov, corresponding to the formula a2In2O7preferred is the use of gadolinium, lanthanum or yttrium as component a and hafnium, titanium or zirconium as a component of the Century. lanthanum lead zirconate shows a low thermal conductivity, but may cause difficulties when applying the method HALFOP as lanthanum and zirconium are significantly different saturated vapor pressure, which complicates the deposition from the vapor phase. As already mentioned, was studied only patterns of type a2In2About7and had not made any attempts to use known pyrochlore, in which part of oxygen is substituted by fluorine or sulfur. However, it appears that there is no reason to exclude from the scope of the present invention compositions corresponding to such substitution. Not rated structures And2In2O6and AB2About6but they seem to be potentially useful for obtaining coatings that creates a thermal barrier. With regard to structures other than pyrochlore, gadolinium and zirconium have close values of saturated vapor pressure, which facilitates the deposition from the vapor.The elements Ti, Zr, Hf is characterized by complete solubility in one another in the solid penalogical way Gd, La, Y have a high solubility in the solid phase (pair Gd-La is characterized by complete solubility). Therefore, any combination of Gd+La+Y, which does not generate the second phase, can be used as component A. the Recommended alloys components a and b must meet the criteria shown in Fig.2, and to have the pyrochlore structure.The low thermal conductivity of the oxides of the pyrochlore can be explained by the influence of the crystalline and chemical effects. thermal conductivity of solid dielectrics at elevated temperatures is determined by the scattering of phonons, lattice defects and other phonons. The oxides of the pyrochlore find many properties associated with materials having low heat conductivity. The pyrochlore-structure characterized by a high concentration of defects. Experimentally it was found that, by increasing the difference between the atomic masses of the constituent components of the connection, the conductivity of the connection has a tendency to decrease. Although the structure of pyrochlore and fluorite are closely related, the introduction, with a high concentration of atoms with relatively high atomic weight of lanthanum, gadolinium and yttrium) in the crystal structure of fluorite is a tool sliderevent compounds of zirconium oxide. It should be noted that, in relation to the establishment of thermal barrier, the advantages achieved by reducing thermal conductivity resulting from the use of elements with high atomic mass, should outweigh the disadvantages associated with increasing density.As one of the factors contributing to the reduction of thermal conductivity, called also the increasing complexity of the crystallographic structure. As can be seen from a comparison of Fig.1A and 1B, the structure of pyrochlore detects a greater degree of complexity than the structure of fluorite. The cubic pyrochlore structure similar to the cubic fluorite structure, but it is the displacement of a large number of oxygen atoms (and the absence of one atom of eight). Coating that creates a thermal barrier, typically applied by thermal spraying, such as plasma spraying in air (NVD), at low pressure (PNND), using high-speed beam oxygen fuel (WPCT). Alternative methods are electron-beam physical vapour deposition (HALFOP) and electron-beam sputtering. The preferred method is HALFOP, however, each of these processes has its own special advantages with respect to con the in-pyrochlore to create a thermal barrier. As already mentioned, the method HALFOP has advantages with regard to this task, because it allows you to create a structure suitable for use in extreme temperatures, i.e. desirable to use a coating of the hot zone components of the turbine. Methods of thermal spraying have an advantage when applying coatings on components of complex shape and, therefore, seem to be the best with regard to such components as the combustion chamber.Fig.3A, 3B and 3C illustrate variants of the coatings in accordance with one variant of the present invention. In Fig.3A shows the product with the matrix 10 from a special alloy on the outer surface 21 which has a layer of the outer cover 20 of the pyrochlore. As applied to gas turbines the second side of the matrix 10 from a special alloy will be cooled by the cooling air flow (not illustrated), while the outer (front) surface 21 with a deposited pyrochlore will be exposed to high temperatures. Can also be provided by the channels passing from the back to the outer surface, allowing cooling air to flow from the rear to the outer surface. The cooling hole is the second surface, allow you to create a cooling film in a layer of cold air, which separates the outer surface from the hot gases and helps to reduce heat flow. A significant decrease of the heat flow from the front (outer) surface 21 to the cooling surface 11 is provided with a layer 20. As mentioned above, the pyrochlore can be applied by various methods, and the macrostructure layer of pyrochlore is largely a function of the method of its application. The base variant of the present invention (see Fig.3A) corresponds exactly to the pyrochlore layer, which is associated with the matrix and reduces the heat flow in the presence of a temperature gradient.In Fig.3B shows a preferred variant of the invention, providing a primer (bonding surface) 15 between the matrix 10 and layer 20 of pyrochlore. Primer 15 improves grip and provides antioxidant protection matrix. In Fig.3 on an enlarged scale showing the intermediate layer 16 between the primer layer 15 and 20 pyrochlore. This intermediate layer has an oxide film 22, mainly consisting of aluminum oxide, it is assumed that it provides a good grip of pyrochlore.It is known that with regard to the coatings n is the natural enemy on the primer, can be achieved by sputtering of aluminum oxide on the primer, and the use of separately deposited layer (film) of aluminum oxide (instead of the oxide layer formed by thermal) also corresponds to one of the embodiments of the present invention.In another embodiment of the invention on an exposed surface of the coating, which creates a thermal barrier, may be applied to another ceramic layer. The purpose of this additional layer may consist in reducing the diffusion of oxygen, providing resistance to erosion and abrasion, or in securing the coefficient of thermal radiation, or the achievement of any combination of these characteristics.Example 1Discusses the use of oxide pyrochlore, corresponding to the compound of La2Zr2O7(lanthanum lead zirconate), applied by the method of ELTOP, as a coating that creates a thermal barrier. The advantages of using such coatings La2Zr2O7compared with stabilized zirconium oxide (YSZ) are related to thermal conductivity, thermal expansion, density, phase stability and lower cost. In Fig.4 shows the phase diagram L (when the content of La2O335 molar %) stable up to the melting point, i.e., up to about 2300C.In Fig.5 shows the data on the temperature dependence of thermal conductivity of La2Zr2O7in comparison with zirconium oxide having a cubic structure. At temperatures typical for use coatings that creates a thermal barrier, pyrochlore shows thermal conductivity, which is 50% lower than the corresponding values for stabilized zirconium oxide. The tightness of pyrochlore is approximately the same as that of the stabilized Zirconia (about 6 g/cm3), so that after the correction parameters, taking into account the mass of the gain in thermal conductivity is about 50%. Taking into account the difference between the vapour pressure of the coating components, the preferred method of application of La2Zr2O7it seems plasma spraying.This merit consisting in 50% reduction of thermal conductivity, reduces the thickness of the coating is about 50% while providing the same thermal protection. The reduction of weight of coating on a typical turbine blade by 50% will reduce the force with which the blade acts on the shank in typical operating conditions, 680 kg, which will lead opacki. If you keep the same coating thickness and use the same stream of cooling air, the temperature of the matrix will be reduced by approximately 55With that will provide an increase of the fatigue durability of the matrix during creep. The same coating thickness with decreasing flow of air will increase the efficiency of the apparatus. You can also receive a combination of the above mentioned advantages, for example a (small) reduction in coating weight plus a (small) reduction in air flow.In Fig.6 shows the temperature dependence of the average values of thermal expansion coefficients of La2Zr2O7and Zirconia stabilized cubic structure. You can see that thermal expansion characteristics of the coatings to create a thermal barrier of La2Zr2O7and cubic modification of zirconium dioxide are close to each other. This means that in thermal cycle La2Zr2O7will behave similarly to the Zirconia.Example 2On the matrix by electron beam physical vapour deposition (HALFOP) in a chamber with controlled atmosphere suffered lanthanum lead zirconate. The matrix was mnia coating was carried out at a pressure of 3.210-4Torr when the supply air stream with a flow rate of 50 cm3/C. Oxygen was introduced in order to provide the stoichiometry of pyrochlore oxygen (see U.S. patent No. 5087477 owned by the applicant of the present invention). The temperature of the matrix during coating was about 1005With, and distance from the matrix to the original source material - 13,34 see the Source of the ceramic material to obtain the pyrochlore evaporated by an electron beam with the parameters of 0.8 and 10 kV. The original oxide served as the material powder La2Zr2O7. The coating has been found favorable columnar structure, typical coatings of cubic modification of zirconium dioxide done to create a thermal barrier method HALFOP. Cover with such a structure characterized by the absence of stress and the best wear resistance compared to coatings applied by plasma spraying.In Fig.7 shows the spectrum of the diffraction of x-rays to the coating surface. Peaks of diffraction were attributed to the crystal structure of pyrochlore, which confirms the formation of this structure in the coating to create a thermal barrier.Yes the which can enter a number (up to 8-10% by volume) of the same substance with the structure of pyrochlore, also has low thermal conductivity. In accordance with another variant of the present invention, the gadolinium oxide - zirconium preferably contains up to 100% by volume of material with a cubic crystal structure of fluorite, with the possible inclusion of a quantity of material with the structure of pyrochlore. This structure in this description is called "the fluorite structure", to distinguish it from the above "cubic pyrochlore structure". The fluorite structure corresponds to the structure shown in Fig.1B. Not excluded the use of material other patterns.In Fig.8 shows the microstructure of a sample of gadolinium oxide - zirconium (Gd, Zr)O2applied by the method of ELTOP the matrix 22 of aluminum oxide. Ceramic coating 24 has a columnar grain structure. Zirconium component coverage did not include pure zirconium oxide, and contained about 2% by weight of yttrium in the form of 7YSZ, so in Fig.10 material denoted as (Gd, Y, Zr)O2.In Fig.9 shows the microstructure of a material similar to those shown in Fig.8, but after heat treatment at about 1370With over 125 hours. The sample is a matrix of aluminum oxide with pocrisy corresponds to the zone, in which the materials of the matrix and the coating was diffundiruet each other in the heat treatment process. The erosion tests showed that the coatings formed by gadolinium oxide - zirconium with the fluorite structure, have an acceptable resistance to erosion. In addition, further tests showed that gadolinium oxide - zirconium quite resistant to sintering.Tests also demonstrated that the composition has a stable structure in different zones of the surface coating, which confirms that the oxides of gadolinium and zirconium have similar values of saturated vapor pressure. This means that the gadolinium oxide - zirconium and, in particular, its modification corresponding to the lead zirconate gadolinium Gd2Zr2O7can quite easily be applied using conventional methods such as the normal procedure HALFOP, which uses only the evaporated material is a target representing the ingot corresponding alloy, and other above methods of application PSTB.Several samples of monolithic gadolinium oxide - zirconium with the fluorite structure, as well as zirconium oxide stabilized with yttrium oxide (YSZ), were tested in the range of temperature thermal conductivity of solid oxide gadolinium - zirconium is about 1.1 to 1.4 W/(mdeg.). This is about half of the measured values of this ratio for YSZ. The test material contained about 2% by weight of yttrium (in the form of 7YSZ), instead of pure zirconium oxide. It is expected that the material consisted only of Zirconia and gadolinium, its thermal conductivity is close to the samples described in Fig.10.It is evident from Fig.11 shows that the coating consisting of thin layers of gadolinium oxide-zirconium, find the same tendency towards YSZ, and the corresponding monolithic material, i.e., coefficient of thermal conductivity is lower than 1.5 W/(mdeg.). More specifically, the coating of the oxide of gadolinium - zirconium have a coefficient of thermal conductivity of about 1.0 W/(mdeg.) in the temperature range from room temperature up to at least 1260C. As follows from Fig.11, the coating containing an oxide of gadolinium zirconium and applied by the method of ELTOP demonstrate coefficients of thermal conductivity, approximately 50% smaller than 7YSZ applied by the method of HALFOP. It is also significant that the reduction of thermal conductivity of gadolinium oxide - zirconium by otnosheniya way and adjusted to the density of thermal conductivity of gadolinium oxide-zirconium approximately 50% less than 7YSZ.In Fig.12 shows a partial phase diagram for gadolinium and zirconium. The gadolinium oxide - zirconium structure by type of fluorite has a phase stability at least up to about 1650C. As shown by the dotted lines around the area marked "R"), oxides of gadolinium and zirconium can form the pyrochlore structure; however, the ability to form such a structure is manifested not very much. Accordingly, it is assumed that even in the zone (P) in the phase diagram, in which it is expected the formation of lead zirconate gadolinium Gd2Zr2O7with the structure of pyrochlore, the material will likely be at least partially to have a more regular structure of fluorite. As follows from Fig.12, although the gadolinium oxide - zirconium with the structure of the pyrochlore type can exist in a wide range of compositions and is stable up to about 982With, any transition will lead to the fluorite structure, which, as already noted, is stable at much higher temperatures. Test samples show that the structure of the material was mainly the fluorite structure. This result is consistent with the definition of the zone of pyrochlore in Fig.12, indicated by the dotted lines.Although preferred within the present invention represented by a composition based on zirconium oxide, containing approximately 5-60 mol.% oxide of gadolinium, we do not exclude the use of other compositions. While the oxides of zirconium or gadolinium can be partially substituted for yttrium oxide at a concentration of up to about 25 mol.%, preferably no more than about 20 mol.%.As already mentioned, it has been experimentally established and has become generally accepted that increasing the difference between the atomic masses of the components of the connection, the conductivity of this compound shows a tendency to decrease. In this regard, one might expect that the gadolinium oxide - Zirconia has a lower thermal conductivity than YSZ, since the difference between the atomic masses Gd (about 157) and Zr (approximately 91) is greater than Y (89) and Zr. However, the degree of reduction of thermal conductivity, which constitutes about 50%, it is simply amazing.Mentioned that, according to conventional wisdom, the more complex the crystal structure of the material, similar to the structure of pyrochlore, shown in Fig.1A, is associated with reduced teploprocessy structure which is quite simple - compared with the pyrochlore Gb2Zr2O7- has low thermal conductivity. thermal conductivity of gadolinium oxide - zirconium is comparable to the conductivity of pyrochlore La2Zr2O7, both named material demonstrate the conductivity, which is approximately twice smaller than usually used YSZ. It is assumed that the reduction in thermal conductivity due to the addition of gadolinium oxide, which provides a large difference in atomic masses (relative to zirconium), as well as a large number of vacancies.Described embodiments of the present invention include the use of coatings in the form of a single essentially homogeneous layer. However, the coatings according to the invention can be applied as part of a system containing multiple discrete layers, similar to that described in U.S. patent No. 5687679 owned by the applicant of the present invention and are incorporated in this description by reference thereto.It was also discovered that a thin layer of ceramics such as YSZ, the aluminium oxide layer before applying the PSTB, ensures adequate layer with high adhesion, i.e. ceramic primer for applied over this layer PSTB.And uminia) 15 and the ceramic coating 20, creating a thermal barrier (PSTB). Between the metal layer and PSTB applied layer 17 ceramic primer. This first coat should be thick enough to provide a reliable capping layer of aluminum oxide. However, if ceramic primer is applied on the rotating part, such as a turbine blade, this layer should not have a thickness greater than necessary to perform its functions, since this additional layer increases the mass of the part and makes a significant contribution to the force on the shank, created by a shovel.In one test layer ceramic primer consisted of 7YSZ applied by the method of HALFOP, and had a thickness of about of 0.013 cm, although its thickness may be several times more. It is assumed that a satisfactory ceramic binder coating (primer) of YSZ can be applied and the method of spraying. Microscopic examination of samples having a layer of YSZ showed that the grain boundaries between YSZ and applied to it a layer of PSTB is epitaxial growth. In addition, the YSZ layer gives some resistance in the event of any defects PSTB.While the present invention primarily is intended for espaiiola, having the desired porosity, as isolation (see, for example, U.S. patent No. 4936745, which belongs to the applicant of the present invention and is incorporated in this description by reference thereto). As an example, the inclusion of gadolinium oxide - zirconium polymer material with subsequent application of thermal spraying and thermal treatment, leading to the formation of pores in ceramics. In such applications, the porosity of the coating is preferably 30-60% by volume.Although the present invention has been illustrated and described in detail in the examples of the preferred options for professionals in this field will be clear that, without going beyond the boundaries of the ideas and scope of the invention, in the form and details of the invention, it is possible to make various changes, additions and deletions.
Claims1. Metal article comprising a metal matrix (10), the surface of which has a ceramic coating (20) with a cubic crystal structure, wherein the ceramic coating comprises oxides of gadolinium and zirconium.2. The product under item 1, characterized in that the ceramic coating (20) is to the Eesa fact, that ceramic coating (20) contains not more than 10% by volume of the material having the crystal structure of pyrochlore.4. Product according to any one of paragraphs.1-3, characterized in that the ceramic coating (20) comprises about 5-60 mol.% oxide of gadolinium and the rest of zirconium oxide.5. Product according to any one of paragraphs.1-4, characterized in that thermal conductivity of the ceramic coating (20) is less than about 1 W/(mhail).6. Product according to any one of paragraphs.1-5, characterized in that the ceramic coating (20) has a columnar microstructure.7. Product according to any one of paragraphs.1-6, characterized in that on the outer surface of the metal matrix (10) has an oxide film (22) consisting essentially of aluminum oxide, with ceramic coating (20) is connected with an oxide film.8. Product according to any one of paragraphs.1-6, characterized in that it further comprises a ceramic primer (17) disposed between the ceramic coating (20) and metal matrix (10).9. The product under item 8, characterized in that the ceramic primer (17) consists of zirconium oxide stabilized with yttrium oxide.10. Product according to any one of paragraphs.1-9, characterized in that the metal matrix (10) will any of paragraphs.1-10, characterized in that the specified product with a coating adapted for use in conditions where the external surface (21) of the ceramic coating (20) is subjected to heating, and free from coating surface (11) of the matrix (10) will be cooled, while the ceramic coating will reduce the heat flow.12. Product according to any one of paragraphs.1-11, characterized in that the ceramic coating has a porosity of approximately 30-60% by volume.13. Metal article comprising a metal matrix (10), which on the surface has a layer of aluminium oxide that forms the floor (15), and ceramic coating (20) with a cubic crystal structure associated with the specified coating, forming aluminum oxide, characterized in that the ceramic coating is formed by oxides of gadolinium and zirconium.14. The article on p. 13, characterized in that the coating (15), forming aluminum oxide, contains the overlay coating.15. The article on p. 13, characterized in that the coating (15) forming the aluminum oxide is a coating applied by the method of diffusion plating to form aluminides.16. Product according to any one of paragraphs.13-15, characterized in that the ceramic coating is p. 16, characterized in that the ceramic coating (20) contains not more than 10% by volume of the material having the crystal structure of pyrochlore.18. Product according to any one of paragraphs.13-17, characterized in that the metal matrix (10) is selected from the group consisting of steels, special alloys, titanium alloys and copper alloys.19. Product according to any one of paragraphs.13-18, characterized in that the specified product with a coating adapted for use in conditions where the external surface (21) of the ceramic coating (20) is subjected to heating, and free from coating surface (11) of the matrix (10) will be cooled, while the ceramic coating will reduce the heat flow.20. Product according to any one of paragraphs.13-19, characterized in that the ceramic coating has a porosity of approximately 30-60% by volume.21. Product according to any one of paragraphs.13-20, characterized in that the ceramic coating (20) comprises about 5-60 mol.% oxide of gadolinium and the rest of zirconium oxide.22. Product according to any one of paragraphs.13-21, wherein the coefficient of thermal conductivity of the ceramic coating (20) is less than about 1 W/(mdeg.).23. Method of providing thermal protection of the metal matrix (10), Vallicelli structure, characterized in that the ceramic coating consists of oxide of gadolinium and zirconium.24. The method according to p. 23, characterized in that it further includes the operation of applying ceramic primer (15), performed before the application of the ceramic coating (20), and the primer consisting of zirconium oxide stabilized with yttrium oxide, is between the metal matrix (10) and ceramic coating (20).25. The method according to p. 23 or 24, characterized in that the ceramic coating (20) is applied by a method selected from the group consisting of thermal spraying, sputtering and vacuum deposition.
FIELD: metal science; protection of materials against external and corrosive attacks.
SUBSTANCE: proposed method for producing diamond-like films designed for encapsulating solar photocells to protect them against chemical, radiation, and mechanical damage includes variation of ion kinetic energy, plasma discharge current, and spatial density distribution of plasma incorporating C+, H+, N+, and Ar+ ions by acting upon ion current from radial source with electric field built up by stop-down, neutralizing, and accelerating electrodes. Spatial plasma distribution is checked for uniformity by measuring plasma current density on solar photocell surface whose temperature is maintained not to exceed 80 oC. In the process substrate holder makes complex axial movement in three directions within vacuum chamber. Diamond-like films produced in the process on solar photocell surface area over 110 cm2 are noted for uniformity, difference in their optical parameters variable within desired range is not over 5%.
EFFECT: enhanced adhesive property, microhardness, and resistance of films to corrosive attacks.
5 cl, 12 dwg, 2 tbl