Plasma spraying integral type zirconium boride coating for burnable poison and preparation method of zirconium boride coating

Abstract

The invention provides a zirconium boride coating and a preparation method thereof, one preparation method comprises the following steps: sequentially carrying out particle size grading optimization treatment on zirconium boride powder to obtain the zirconium boride coating with the particle size distribution of D50lt; 10 [mu] m, D97lt; zirconium boride powder with a particle size of 20 [mu] m; the particle size distribution is D50lt; 10 [mu] m, D97lt; carrying out plasma spheroidizing treatment on the zirconium boride powder with the particle size of 20 microns to obtain pretreated powder with the spheroidizing rate of more than 85%; and the pretreated powder is deposited on a base body through low-pressure plasma spraying, and the zirconium boride coating is obtained. According to the method, the zirconium boride powder is subjected to particle size refining and spheroidizing treatment, and a plasma spraying process is adapted, so that the problems that continuous and stable spraying of a thin coating cannot be realized and the spraying thickness uniformity of the thin coating cannot be controlled in an existing plasma spraying technology are solved; the problems that fine-particle-size zirconium boride powder is poor in fluidity in plasma spraying, and the powder cannot enter the center of flame flow to cause incomplete melting are solved. And the application of the plasma spraying process in the aspect of preparing the zirconium boride coating from the integral burnable poison is realized.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear fuel element preparation, and in particular to a plasma sprayed integral zirconium boride coating for combustible poison and a preparation method thereof. Background Art

[0002] ZrB2 materials are widely used in high-temperature structural ceramics due to their high melting point, high hardness, good electrical conductivity, and high-temperature oxidation resistance. Their films are also prominently used in aerospace, solar energy, nuclear energy, and other fields. 10 When B-enriched, it has excellent neutron absorption properties, making ZrB2 films useful in nuclear reactor fuel elements.

[0003] IFBA is the abbreviation of Integral Burnable Poison Assembly, which is an important component of AP1000 nuclear reactor nuclear fuel elements. IFBA pellets are coated with ZrB2 coating evenly on the cylindrical surface of nuclear fuel UO2 by magnetron sputtering to adjust the reactivity of the reactor, thereby improving the utilization rate of nuclear fuel, reducing nuclear power costs, and extending the replacement cycle of nuclear fuel elements.

[0004] There are many existing methods for preparing coatings, such as electron gun evaporation, magnetron sputtering, plasma spraying, electron beam physical vapor deposition (EBPVD), etc. Electron gun evaporation is mainly used for the deposition of thin films, and the thickness is generally less than 100nm; magnetron sputtering can also be used to deposit coatings with a thickness of μm level, but the deposition efficiency is relatively low; EBPVD is mainly used to deposit thermal barrier coatings with special structures; plasma spraying technology uses a plasma arc as a heat source to heat ceramics, alloys, metals and other materials to a molten or semi-molten state, and sprays them at high speed onto the pre-treated workpiece surface to form a coating.

[0005] At present, the zirconium boride coating used for commercial integral burnable poison components is prepared by magnetron sputtering, but this method has low deposition efficiency, long sputtering deposition time, and the effective utilization rate of the target material does not exceed 50%. Moreover, most of the material is deposited in the chamber during magnetron sputtering, and no more than 20% is actually deposited on the substrate to form a coating. In addition, grinding losses during the target processing and molding process cannot be avoided, and the purification process of grinding waste is complicated and the recycling cost is high.

[0006] Therefore, it is urgent to develop new and efficient coating preparation methods. Summary of the invention

[0007] In view of the above problems existing in the prior art, the present invention provides a plasma sprayed integral zirconium boride coating for combustible poisons and a preparation method thereof. By subjecting zirconium boride powder to particle size classification optimization, spheroidization and other treatments, and adapting the plasma spraying process, the prepared zirconium boride coating is uniform and dense, and its adhesion is equivalent to that of a sputtering coating. The specific invention contents are as follows:

[0008] In a first aspect, the present invention provides a method for preparing an integral zirconium boride coating for a combustible poison by plasma spraying, the method comprising the following steps:

[0009] The zirconium boride powder is subjected to particle size classification and optimization treatment in sequence to obtain zirconium boride powder with a particle size distribution of D50<10μm and D97<20μm;

[0010] The zirconium boride powder with a particle size distribution of D50<10 μm and D97<20 μm is subjected to plasma spheroidization treatment to obtain a pre-treated powder with a spheroidization rate greater than 85%;

[0011] The pretreated powder is deposited on a substrate by low-pressure plasma spraying to obtain the zirconium boride coating.

[0012] Optionally, the particle size classification optimization process is ball milling or air flow milling.

[0013] Optionally, the fluidity index of the pretreated powder is greater than 25S / 50g.

[0014] Optionally, the working gas pressure of the low-pressure plasma spraying is 100-800 mbar, the movement speed of the spray gun is 500-700 mm / s, and the number of spraying passes is 6-8 times.

[0015] In a second aspect, the present invention provides another method for preparing an integral zirconium boride coating for a burnable poison by plasma spraying, the method comprising the following steps:

[0016] The zirconium boride powder is subjected to particle size classification optimization treatment to obtain zirconium boride powder with a particle size distribution of D50<3μm and D97<7μm;

[0017] Spray granulation is performed on the zirconium boride powder with a particle size distribution of D50<3 μm and D97<7 μm to obtain a pretreated powder with a particle size of 10-50 μm;

[0018] The pretreated powder is deposited on a substrate by low-pressure plasma spraying to obtain the zirconium boride coating.

[0019] Optionally, the particle size classification optimization process is ball milling or air flow milling.

[0020] Optionally, the particle size of the pretreated powder is 10-50 μm.

[0021] Optionally, the fluidity index of the pretreated powder is greater than 15S / 50g.

[0022] Optionally, the working gas pressure of the low-pressure plasma spraying is 100-800 mbar, the movement speed of the spray gun is 500-700 mm / s, and the number of spraying passes is 6-8 times.

[0023] In a third aspect, the present invention provides another method for preparing an integral zirconium boride coating for a burnable poison by plasma spraying, the method comprising the following steps:

[0024] The zirconium boride powder is subjected to particle size classification optimization treatment to obtain a zirconium boride powder with a particle size distribution of D50 < 3 μm and D97 < 7 μm;

[0025] Dispersing the zirconium boride powder with a particle size distribution of D50<3 μm and D97<7 μm into a dispersion medium containing polyvinyl alcohol or ammonium polyacrylate to obtain a zirconium boride powder suspension;

[0026] The zirconium boride coating is obtained by depositing the zirconium boride powder suspension liquid on the substrate using a suspension plasma spraying method.

[0027] Optionally, the particle size classification optimization process may be ball milling or air flow milling technology.

[0028] Optionally, the dispersion medium is deionized water or anhydrous ethanol; and the solid content of the zirconium boride powder suspension is 5-30%.

[0029] Optionally, the spraying power of the suspension plasma spraying method is 60-120KW.

[0030] In a fourth aspect, the present invention provides a monolithic zirconium boride coating for combustible poisons obtained by the preparation method described in any one of the first to third aspects, wherein the thickness of the zirconium boride coating is 5-20 μm; the relative density of the zirconium boride coating is 80% to 99%; 10 The abundance of B is between 10wt% and 99.9wt%.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) The present invention provides a plasma sprayed integral type combustible poison zirconium boride coating and a preparation method thereof. By refining the particle size of zirconium boride powder and spheroidizing it, and adapting it to the plasma spraying process, the existing plasma spraying technology is unable to achieve continuous and stable spraying of thin coatings, and the control of the uniformity of the spraying thickness of thin coatings; the problem that fine-particle zirconium boride powder has poor fluidity in plasma spraying and the powder cannot enter the center of the flame flow, resulting in incomplete melting is solved. The application of plasma spraying technology in the preparation of zirconium boride coatings for integral type combustible poisons is realized.

[0033] (2) The preparation method provided by the present invention overcomes the technical difficulty of controlling the thickness and uniformity of the coating when preparing a thin coating with a thickness of about 10 μm by the plasma spraying method. 10 Under the condition of constant B line density, the number of spraying passes is reasonably designed to control the thickness of the zirconium boride thin coating between 5μm and 20μm, which reduces the 10 B abundance, and 10 The cost of B raw materials is greatly reduced as the abundance decreases. Therefore, the cost of IFBA coating can be further reduced. And the prepared zirconium boride thin coating 10 The B abundance meets the application requirements, the coating is uniform and dense, and the adhesion is comparable to that of sputtered coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 A flow chart of a method for preparing a zirconium boride coating provided in an embodiment of the present invention is shown;

[0036] Figure 2 A flow chart of another method for preparing a zirconium boride coating provided by an embodiment of the present invention is shown;

[0037] Figure 3 A flow chart of another method for preparing a zirconium boride coating provided by an embodiment of the present invention is shown;

[0038] Figure 4 The particle size distribution of zirconium boride powder after the particle size classification optimization treatment provided in Example 1 of the present invention is shown;

[0039] Figure 5 The morphology of the pretreated powder provided in Example 1 of the present invention is shown;

[0040] Figure 6The morphology of the plasma sprayed zirconium boride coating provided in Example 1 of the present invention is shown;

[0041] Figure 7 The cross-sectional morphology of the plasma sprayed zirconium boride coating provided in Example 1 of the present invention is shown;

[0042] Figure 8 The figure shows the particle size distribution of zirconium boride powder after the particle size classification optimization treatment provided in Example 2 of the present invention;

[0043] Fig. 9 The morphology of the pretreated powder provided in Example 2 of the present invention is shown;

[0044] Fig.10 The figure shows the dispersion of zirconium boride powder in PVA after the particle size classification optimization treatment provided in Example 3 of the present invention;

[0045] Fig.11 The cross-sectional morphology of the suspension plasma sprayed zirconium boride coating provided in Example 3 of the present invention is shown;

[0046] Fig.12 The morphology of the plasma sprayed zirconium boride coating provided in Comparative Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0047] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0048] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the prior art can be used. The reagents and other instruments used without specifying the manufacturer are all conventional reagent products that can be purchased commercially.

[0049] Before describing in detail the preparation method and application of the zirconium boride coating provided by the present invention, it is necessary to describe the related technologies as follows:

[0050] Compared with magnetron sputtering, plasma spraying has the following advantages for preparing zirconium boride coating:

[0051] (1) The plasma spraying method directly uses ZrB2 powder as the starting material, without the need for hot pressing and sintering to prepare the target material. The process flow from material to coating is significantly shortened.

[0052] (2) Plasma spraying has high efficiency, dense coating, high bonding strength, high effective utilization rate of coating powder, and easy recycling, which can significantly reduce the manufacturing cost of combustible poison IFBA coating.

[0053] (3) The thickness of the coating can be adjusted according to the design requirements of the fuel element. The efficiency of increasing the thickness by magnetron sputtering is too low, while plasma spraying is easy to achieve. 10 Under the condition of constant B line density, the coating thickness can be increased 10 The abundance of B decreased significantly, while 10 The cost of B raw materials decreases greatly as the abundance decreases.

[0054] However, the particle size D50 of the spray powder used in traditional plasma spraying is generally between 30 and 40 μm, and the thickness of the prepared coating reaches or exceeds 50 μm. When preparing a thin coating with a thickness of about 10 μm, it is difficult to control the thickness and uniformity of the coating.

[0055] Low-pressure plasma spraying combines the characteristics of traditional plasma spraying technology that mainly forms coatings by solidification and vapor deposition technology that deposits thin films in a gas / solid manner. This technology is suitable for spraying ultra-high melting point easily oxidized metals, borides, and carbides, and for the preparation of fast thin coatings. The coating is thin and has high uniformity, but it places high process adaptability requirements on the spray powder. When the powder particle size is fine, the fluidity is poor, and the powder is difficult to enter the center of the flame flow, resulting in poor melting properties. In addition, the unstable powder feeding makes it difficult to spray continuously.

[0056] In order to realize the preparation of thin coatings with a thickness of 5 to 20 μm by low-pressure plasma spraying and further reduce the cost of IFBA coatings, the present invention improves the morphology, particle size distribution and fluidity of zirconium boride powder through a variety of pretreatment processes, and develops an adaptive plasma spraying process to achieve the control of coating microstructure and uniformity. A zirconium boride coating that meets the use requirements of IFBA is obtained. The specific implementation content is as follows:

[0057] In a first aspect, the present invention provides a method for preparing an integral zirconium boride coating for a burnable poison by plasma spraying. Figure 1 The flowchart of the preparation method of the zirconium boride coating provided by the embodiment of the present invention is shown as follows: Figure 1 As shown, the method includes:

[0058] S11, performing particle size classification optimization treatment on the zirconium boride powder to obtain a zirconium boride powder with a particle size distribution of D50<10μm and D97<20μm;

[0059] S12, performing plasma spheroidization treatment on the zirconium boride powder having a particle size distribution of D50<10 μm and D97<20 μm to obtain a pretreated powder;

[0060] S13, depositing the pretreated powder on a substrate by low-pressure plasma spraying to obtain the zirconium boride coating.

[0061] In specific implementation, the preparation method of the zirconium boride powder in this embodiment includes but is not limited to a self-propagating method, a carbon thermal reduction method, a sol-gel method, etc., and the carbon thermal reduction method is preferred. Since the particle size of the zirconium boride powder synthesized by the conventional process is too large and the uniformity is poor, it cannot be directly used for the preparation of zirconium boride plasma spraying of thin coatings. Therefore, the present invention first optimizes the particle size classification of the initial zirconium boride powder to obtain a zirconium boride powder (a zirconium boride powder with a particle size distribution of D50<10μm and D97<20μm) whose particle size meets the requirements for the preparation of thin coatings. However, due to the poor fluidity of the fine-grained powder, the zirconium boride powder cannot completely enter the center of the flame flow for melting, thereby affecting the powder feeding stability, and thus the continuous spraying of the fine-grained zirconium boride powder cannot be achieved. Therefore, the present invention further performs plasma spheroidization treatment on the zirconium boride powder after particle size classification optimization treatment (zirconium boride powder with particle size distribution of D50<10μm, D97<20μm) to obtain pretreated powder, so as to improve the fluidity of fine-particle zirconium boride powder.

[0062] In some embodiments, the particle size optimization and classification process can be performed by ball milling or air flow milling technology; the particle size and distribution can be tested by a laser particle size analyzer, and the fluidity index can be tested by a Hall flow meter.

[0063] In some embodiments, in order to ensure continuous spraying of fine-grained zirconium boride powder, the pretreated powder obtained by plasma spheroidization treatment needs to have a fluidity index greater than 25S / 50g and a spheroidization rate greater than 85%, so that the pretreated powder can be evenly deposited on the substrate to form a 5-20 μm zirconium boride coating under the conditions of a low-pressure plasma spraying working pressure of 100-800 mbar, a spray gun moving speed of 500-700 mm / s, and a spraying number of 6-8 times.

[0064] In the specific implementation, the preferred low-pressure plasma spraying process parameters are: working gas pressure is 400 mbar, spray gun moving speed is 700 mm / s, and spraying variable is 8 times.

[0065] The embodiment of the present invention improves the particle size distribution, morphology, and fluidity of zirconium boride powder by particle size refinement and spheroidization treatment, and develops an adaptive plasma spraying process to achieve control of the microstructure and uniformity of the coating. The problem of poor fluidity of fine-grained zirconium boride powder in plasma spraying and incomplete melting caused by the inability of the powder to enter the center of the flame flow is solved. Finally, a zirconium boride coating that meets the requirements of IFBA is prepared, realizing the application of plasma spraying technology in the preparation of zirconium boride coatings for integral combustible poisons.

[0066] In a second aspect, the present invention provides another method for preparing an integral zirconium boride coating for a burnable poison by plasma spraying. Figure 2 A flow chart of another method for preparing a zirconium boride coating provided by an embodiment of the present invention is shown. Figure 2 As shown, the method includes:

[0067] S21, performing particle size optimization and classification treatment on the zirconium boride powder to obtain a zirconium boride powder with a particle size distribution of D50<3μm and D97<7μm;

[0068] S22, spray granulating the zirconium boride powder with a particle size distribution of D50<3 μm and D97<7 μm to obtain a pretreated powder;

[0069] S23, depositing the pretreated powder on a substrate by low-pressure plasma spraying to obtain the zirconium boride coating.

[0070] In specific implementation, the preparation method of the zirconium boride powder in this embodiment includes but is not limited to a self-propagating method, a carbon thermal reduction method, a sol-gel method, etc., preferably a carbon thermal reduction method. Because the initial zirconium boride powder has a large particle size and poor uniformity, it cannot be directly used for plasma spraying preparation of a thin zirconium boride coating. The present invention first optimizes the particle size classification of the initial zirconium boride powder to obtain a zirconium boride powder (a zirconium boride powder with a particle size distribution of D50<3μm and D97<7μm) with a particle size that meets the requirements for thin coating preparation. However, due to the poor fluidity of the fine-particle size powder, the zirconium boride powder cannot completely enter the center of the flame flow for melting, thereby affecting the powder feeding stability, and thus cannot achieve continuous spraying of the fine-particle size zirconium boride powder. Therefore, the present invention further sprays the zirconium boride powder (a zirconium boride powder with a particle size distribution of D50<3μm and D97<7μm) after the particle size classification optimization treatment to obtain a pretreated powder to improve the fluidity of the fine-particle size zirconium boride powder.

[0071] In some embodiments, the particle size optimization and classification process can be performed by ball milling or air flow milling technology; the particle size and distribution can be tested by a laser particle size analyzer, and the fluidity index can be tested by a Hall flow meter.

[0072] In some embodiments, in order to ensure continuous spraying of fine-particle zirconium boride powder, the pretreated powder obtained by spray granulation needs to have a fluidity index greater than 15S / 50g and a particle size of 10-50 μm, so that the pretreated powder can be evenly deposited on the substrate to form a 5-20 μm zirconium boride coating under the conditions of a low-pressure plasma spraying working pressure of 100-800 mbar, a spray gun moving speed of 500-700 mm / s, and a spraying number of 6-8 times.

[0073] In the specific implementation, the preferred low-pressure plasma spraying process parameters are: working gas pressure is 400 mbar, spray gun moving speed is 700 mm / s, and spraying variable is 6 times.

[0074] The embodiment of the present invention improves the particle size distribution, morphology, and fluidity of the zirconium boride powder by particle size refinement and granulation treatment, and develops an adaptive plasma spraying process to achieve control of the microstructure and uniformity of the coating. The problem of poor fluidity of fine-grained zirconium boride powder in plasma spraying and incomplete melting caused by the inability of the powder to enter the center of the flame flow is solved. Finally, a zirconium boride coating that meets the use requirements of IFBA is prepared, realizing the application of plasma spraying technology in the preparation of zirconium boride coatings with integral combustible poisons.

[0075] In a third aspect, the present invention provides another method for preparing an integral zirconium boride coating for a burnable poison by plasma spraying. Figure 3 A flow chart of another method for preparing a zirconium boride coating provided by an embodiment of the present invention is shown. Figure 3 As shown, the method includes:

[0076] S31, performing particle size optimization and classification treatment on the zirconium boride powder to obtain a zirconium boride powder with a particle size distribution of D50<3μm and D97<7μm;

[0077] S32, dispersing the zirconium boride powder with a particle size distribution of D50<3 μm and D97<7 μm into a dispersion medium containing polyvinyl alcohol or ammonium polyacrylate to obtain a zirconium boride powder suspension;

[0078] S33, using a suspension plasma spraying method to deposit the zirconium boride powder suspension liquid on the substrate to obtain the zirconium boride coating.

[0079] In specific implementation, the preparation method of the zirconium boride powder in this embodiment includes but is not limited to a self-propagating method, a carbon thermal reduction method, a sol-gel method, etc., preferably a carbon thermal reduction method. Because the initial zirconium boride powder has a large particle size and poor uniformity, it cannot be directly used for the plasma spraying preparation of a thin zirconium boride coating. The present invention first optimizes the particle size classification of the initial zirconium boride powder to obtain a zirconium boride powder (a zirconium boride powder with a particle size distribution of D50<3μm and D97<7μm) whose particle size meets the requirements for the preparation of a thin coating. However, due to the poor fluidity of the fine-grained powder, when the zirconium boride coating is prepared by plasma spraying, the fine-grained zirconium boride powder cannot completely enter the center of the flame flow for melting, thereby affecting the powder feeding stability, and thus the continuous spraying of the fine-grained zirconium boride powder cannot be achieved. Therefore, the present invention further prepares the zirconium boride powder with a particle size distribution of D50<3μm and D97<7μm into a zirconium boride powder suspension, and increases the fluidity of the fine-grained zirconium boride powder by converting the solid phase into the liquid phase. Since the zirconium boride powder is uniformly present in the suspension, when it is deposited on the substrate by the suspension plasma spraying method, the solvent in the suspension evaporates due to heat, and the zirconium boride powder is uniformly deposited on the substrate. Among them, the dispersant can be polyvinyl alcohol (PVA217) or ammonium polyacrylate, and the dispersion medium can be deionized water or anhydrous ethanol; using PVA217 as a dispersant can obtain a better suspension dispersion effect.

[0080] In some embodiments, the particle size optimization and classification process can be performed by ball milling or air flow milling.

[0081] In some embodiments, the mass proportion of zirconium boride powder with a particle size distribution of D50<3μm and D97<7μm in the suspension is 5-30%, and the suspension plasma spraying condition of 60-120KW is adapted to obtain a uniform and dense zirconium boride coating.

[0082] In a specific implementation, the mass proportion of zirconium boride powder with a particle size distribution of D50<3 μm and D97<7 μm in the suspension is preferably 10%, and the plasma spraying power of the suspension is preferably 90 KW.

[0083] The embodiment of the present invention improves the particle size distribution and fluidity of the zirconium boride powder by combining particle size refinement treatment with suspension preparation, adopts a method, and develops an adapted suspension plasma spraying process to achieve control of the microstructure and uniformity of the coating. The problem of poor fluidity of fine-grained zirconium boride powder in plasma spraying and incomplete melting caused by the inability of the powder to enter the center of the flame flow is solved. Finally, a zirconium boride coating that meets the use requirements of IFBA is prepared, realizing the application of plasma spraying technology in the preparation of zirconium boride coatings with integral combustible poisons.

[0084] In a fourth aspect, the present invention provides a monolithic zirconium boride coating for combustible poisons obtained by the preparation method described in any one of the first to third aspects, wherein the thickness of the zirconium boride coating is 5-20 μm; the relative density of the zirconium boride coating is 80% to 99%; 10 The abundance of B is between 10wt% and 99.9wt%.

[0085] In specific implementation, the zirconium boride coating obtained by the above preparation method has good solubility, the substrate is completely covered, the relative density of the zirconium boride coating is between 80% and 99%, the thickness is 5-20 μm, and the distribution is uniform. The adhesion of the coating tested by the thermal shock method combined with the tape adhesion method does not exceed 0.0002g, and the adhesion is good.

[0086] In specific implementation, the preparation method provided by the present invention is used for the preparation of integral burnable poison component coating. Experiments have shown that the burnable poison coating has almost no quality loss after undergoing at least 6 room temperature to 600°C thermal shock tests and passing the tape peeling test. 10 B abundance, 10 B line density and adhesion meet the application requirements. Compared with the currently commercial magnetron sputtering preparation 10 Compared with the B-enriched ZrB2 coating, the coating can be 10 B enrichment achieves the same function and therefore has a significant cost advantage.

[0087] In order to enable those skilled in the art to more clearly understand the present application, a zirconium boride coating and a preparation method and application thereof described in the present application are now described in detail through the following examples.

[0088] The present invention adopts a carbon thermal reduction method to prepare zirconium boride powder, using graphite C powder, boric acid H3BO3, and zirconium oxide ZrO2 powder as raw materials, and mixing them evenly according to a certain mass ratio of C (16-20wt%), H3BO3 (45-50wt%), and ZrO2 (33-35wt%), and then reacting and synthesizing them at high temperature in a carbon tube furnace.

[0089] Example 1

[0090] ZrO2 powder, natural abundance H3BO3 powder and C powder (ZrO2 / HBO3 / C=35 / 49 / 18wt%) were weighed and mixed evenly according to the component ratio, and then dehydrated and ball-milled at a synthesis temperature of 1900°C and a reaction time of 3h. The prepared powder was subjected to air flow crushing to obtain zirconium boride powder, which was further subjected to plasma spheroidization to obtain pretreated powder. Figure 4 The particle size distribution of zirconium boride powder after the particle size classification optimization treatment provided in Example 1 of the present invention is shown as follows: Figure 4As shown, the particle size distribution of the zirconium boride powder obtained by air flow milling in this embodiment is D50=8.8μm, D97=17.79μm. Figure 5 The morphology of the pretreated powder provided in Example 1 of the present invention is shown in FIG. Figure 5 The SEM image shows that the spheroidization rate of the pre-treated powder obtained by plasma spheroidization treatment is 92%. The pre-treated powder is deposited on the CeO2 ceramic substrate by low-pressure plasma spraying, with a working gas pressure of 400mbar and a spray gun movement speed of 700mm / s. Figure 6 The morphology of the plasma sprayed zirconium boride coating provided in Example 1 of the present invention is shown. Figure 7 The cross-sectional morphology of the plasma sprayed zirconium boride coating provided in Example 1 of the present invention is shown. The coating thickness is 7 to 10 μm. The adhesion of the coating is tested by the thermal shock method combined with the tape adhesion method. The result is 0.0002 g, which means good adhesion. The zirconium boride coating 10 The boron abundance is 18.25wt%, and the relative density of the zirconium boride coating is above 85%.

[0091] Example 2

[0092] According to the component ratio, ZrO2 powder, natural abundance H3BO3 powder, and C powder (ZrO2 / HBO3 / C=35 / 49 / 18wt%) are weighed and mixed evenly, and zirconium boride powder is synthesized by carbon thermal reduction. The prepared powder is crushed by air flow to obtain fine powder, and the fine powder is spray granulated, and the additive is polyvinyl alcohol; after degumming and pre-sintering treatment at 1600℃, pre-treated powder with a particle size of 10-50μm is obtained, and low-pressure plasma spraying is used for deposition of the pre-treated powder on the CeO2 ceramic substrate. The working pressure is 400mbar, the movement speed of the spray gun is 700mm / s, and 6 sprayings are applied to obtain the zirconium boride coating. The coating thickness is about 10-12um. The coating adhesion is tested by thermal shock method combined with tape adhesion method, and the result is 0.0001g, which has good adhesion and the zirconium boride coating 10 The B abundance is 18.25wt%; the relative density of the zirconium boride coating is above 85%. The morphology and cross-sectional morphology of the zirconium boride coating are consistent with those in Example 1 and will not be repeated here.

[0093] Figure 8 The particle size distribution of zirconium boride powder after the particle size classification optimization treatment provided in Example 2 of the present invention is shown. Figure 8 As shown, the particle size and distribution are D50=2.836 μm, D97=5.6 μm.

[0094] Fig. 9 The morphology of the pretreated powder provided in Example 2 of the present invention is shown as a hollow spheroidized shape.

[0095] Example 3

[0096] According to the component ratio, ZrO2 powder, natural abundance H3BO3 powder, and C powder (ZrO2 / HBO3 / C=35 / 49 / 18wt%) were weighed and mixed evenly, and zirconium boride powder was synthesized by carbon thermal reduction. The prepared powder was pulverized by air flow to obtain fine powder with D50=2.836μm, D97=5.6μm, and the particle size and distribution were as follows: Figure 8 As shown. The fine particle size powder is used to prepare the suspension. Fig.10 The dispersion of zirconium boride powder in PVA after the particle size classification optimization treatment provided in Example 3 of the present invention is shown as follows: Fig.10 As shown, PVA is used as a dispersant, and the solid content after dispersion is 10wt%. Under a mixed carrier gas of nitrogen, hydrogen, and argon as the main component, the spraying power is 90KW to prepare a zirconium boride coating with a coating thickness of 15-18um. The coating adhesion is tested by the thermal shock method combined with the tape adhesion method, and the result is 0g, which means the adhesion is good. 10 B abundance is 18.25wt%, Fig.11 FIG. 4 shows a cross-sectional morphology of a suspension plasma sprayed zirconium boride coating provided in Example 3 of the present invention, as shown in FIG. Fig.11 As shown, the density is greater than 90%.

[0097] Comparative Example 1

[0098] According to the component distribution ratio, ZrO2 powder, H3BO3 powder and C powder (ZrO2 / HBO3 / C=35 / 49 / 18wt%) were weighed and mixed evenly, and then dehydrated and ball-milled. The synthesis temperature was 1900°C and the reaction time was 5h. The prepared powder was crushed by air flow method to obtain fine powder with D50=3.477um and D97=7.532um. The fine powder was used as spray powder to deposit a coating on the ZrO2 ceramic substrate by plasma spraying. Fig.12 The morphology of the plasma sprayed zirconium boride coating provided in Comparative Example 1 of the present invention is shown. Fig.12 As shown, the coating surface microstructure is formed by the accumulation of spherical particles, and the melting effect is poor.

[0099] The above is a detailed introduction to the plasma sprayed integral combustible poison zirconium boride coating and its preparation method provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for preparing an integral zirconium boride coating for combustible poisons by plasma spraying, characterized in that: The method comprises: The zirconium boride powder is subjected to particle size classification and optimization treatment in sequence to obtain zirconium boride powder with a particle size distribution of D50<10μm and D97<20μm; The zirconium boride powder with a particle size distribution of D50<10 μm and D97<20 μm is subjected to plasma spheroidization treatment to obtain a pre-treated powder with a spheroidization rate greater than 85%; The pretreated powder is deposited on a substrate by low-pressure plasma spraying to obtain the zirconium boride coating.

2. The preparation method according to claim 1, characterized in that: The particle size classification optimization treatment is ball milling or air flow milling; the fluidity index of the pretreated powder is greater than 25S / 50g.

3. The preparation method according to claim 1, characterized in that: The working gas pressure of the low-pressure plasma spraying is 100-800 mbar, the moving speed of the spray gun is 500-700 mm / s, and the number of spraying passes is 6-8 times.

4. A method for preparing an integral zirconium boride coating for combustible poisons by plasma spraying, characterized in that: The method comprises: The zirconium boride powder is subjected to particle size classification optimization treatment to obtain zirconium boride powder with a particle size distribution of D50<3μm and D97<7μm; Spray granulation is performed on the zirconium boride powder with a particle size distribution of D50<3 μm and D97<7 μm to obtain a pretreated powder with a particle size of 10-50 μm; The pretreated powder is deposited on a substrate by low-pressure plasma spraying to obtain the zirconium boride coating.

5. The preparation method according to claim 4, characterized in that: The particle size classification optimization process is ball milling or air flow milling; The fluidity index of the pretreated powder is greater than 15S / 50g.

6. The preparation method according to claim 4, characterized in that: The working gas pressure of the low-pressure plasma spraying is 100-800 mbar, the moving speed of the spray gun is 500-700 mm / s, and the number of spraying passes is 6-8 times.

7. A method for preparing an integral zirconium boride coating for combustible poisons by plasma spraying, characterized in that: The method comprises: The zirconium boride powder is subjected to particle size classification optimization treatment to obtain zirconium boride powder with a particle size distribution of D50<3μm and D97<7μm; Dispersing the zirconium boride powder with a particle size distribution of D50<3 μm and D97<7 μm into a dispersion medium containing polyvinyl alcohol or ammonium polyacrylate to obtain a zirconium boride powder suspension; The zirconium boride coating is obtained by depositing the zirconium boride powder suspension liquid on the substrate using a suspension plasma spraying method.

8. The preparation method according to claim 7, characterized in that: The particle size classification optimization process can be ball milling or air flow milling technology; the dispersion medium is deionized water or anhydrous ethanol.

9. The preparation method according to claim 7, characterized in that: The solid content of the zirconium boride powder suspension is 5-30%; The spraying power of the suspension plasma spraying method is 60-120KW.

10. An integral zirconium boride coating for burnable poisons, characterized in that: The zirconium boride coating is obtained by the preparation method described in any one of claims 1-3, 4-6, 7-9 above; The thickness of the zirconium boride coating is 5-20 μm; the relative density of the zirconium boride coating is 80% to 99%; 10 The abundance of B is between 10wt% and 99.9wt%.

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