Preparation process of dense zirconium boride coating and plasma spraying device

Abstract

The present invention provides a preparation process and plasma spraying device for a dense zirconium boride coating, and relates to the technical field of coating preparation. The preparation process comprises the following steps: preparing a suspension: mixing a dispersion medium, ZrB2 powder, and a mixture rich in 10 B powder, binder and dispersant are mixed evenly to obtain a suspension; wherein, the content of ZrB2 powder is 2-10wt.% of the total weight of ZrB2 powder and dispersion medium, the content of B powder is 1-3wt.% of ZrB2 powder, the content of binder is not higher than 0.5wt.% of ZrB2 powder, and the content of dispersant is not higher than 0.5wt.% of ZrB2 powder; plasma spraying: plasma spraying technology is used to spray the suspension on the surface of the workpiece to be sprayed in an inert atmosphere to obtain a ZrB2 coating. The cost of preparing the ZrB2 coating is low, and the N and O contents in the coating are low. 10 B has a higher abundance and is more effective as an absorber.

Description

Technical Field

[0001] The present invention relates to the technical field of coating preparation, and in particular to a preparation process of a zirconium boride dense coating and a plasma spraying device. Background Art

[0002] Extending the nuclear fuel cycle and improving the efficiency of nuclear fuel use are the main directions for improving the operating performance of commercial nuclear power reactors. Extending the cycle requires increasing the initial nuclear fuel enrichment. Therefore, more absorbent materials are needed to compensate for the excess initial reactivity. After research, ZrB2 has the characteristics of high melting point, high strength, good conductivity and neutron capture. In the reactor, 10 B can adjust the reactivity of the reactor by absorbing thermal neutrons, so it is rich in 10 The ZrB2 coating with B as an absorber can significantly improve the economic efficiency of the reactor; at the same time, the use of 10 When the ZrB2 coating of B is used as an absorber, it is also required to strictly control the N and O content in the coating to ensure its effect.

[0003] However, in the prior art, the cost of preparing ZrB2 coating is high, and the N and O contents in the coating are high. 10 B is less abundant and less effective as an absorber. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation process and plasma spraying device for dense zirconium boride coating, so as to solve the problems of high cost of preparing ZrB2 coating and high N and O content in the coating. 10 The abundance of B is low, and its effect as an absorber is poor.

[0005] To solve the above problems, the present invention provides a process for preparing a dense zirconium boride coating, comprising the following steps:

[0006] Preparation of suspension: Dispersing medium, ZrB2 powder, 10 Mix B powder, binder and dispersant to obtain a suspension;

[0007] The content of ZrB2 powder is 2-10 wt.% of the total weight of ZrB2 powder and dispersion medium, the content of B powder is 1-3 wt.% of ZrB2 powder, the content of binder is not higher than 0.5 wt.% of ZrB2 powder, and the content of dispersant is not higher than 0.5 wt.% of ZrB2 powder.

[0008] Plasma spraying: Plasma spraying technology is used in an inert atmosphere to spray the suspension onto the surface of the workpiece to be sprayed to obtain a ZrB2 coating.

[0009] Optionally, in the step of preparing the suspension, the median particle size D of the ZrB2 powder is 50 ≤3μm, median particle size D of B powder 50 ≤3μm.

[0010] Optionally, in the step of preparing the suspension, the dispersion medium, ZrB2 powder, and 10 The B powder, binder and dispersant of B are weighed and mixed according to their respective contents to form a mixed liquid, and the mixed liquid is ball milled until the particle dispersion effect in the mixed liquid reaches D 90 ≤5μm and D 50 ≤3 μm to obtain the suspension.

[0011] Optionally, the thickness of the ZrB2 coating is 8 to 20 μm.

[0012] Optionally, the preparation process further comprises a step of treating the workpiece to be sprayed: cleaning the workpiece to be sprayed with an organic solvent, sandblasting the cleaned workpiece to be sprayed with 150-220 mesh white corundum, and blowing the surface of the sandblasted workpiece to be sprayed for the plasma spraying step;

[0013] The process conditions for sandblasting are a pressure of 0.1 to 0.3 MPa and a sandblasting distance of 60 to 80 mm; the pressure for air blowing is 0.3 to 0.5 MPa.

[0014] Optionally, in the step of preparing the suspension, deionized water, anhydrous ethanol or a mixture of the two is selected as the dispersion medium;

[0015] And / or, PVA is selected as the binder;

[0016] And / or, ammonium polyacrylate is selected as the dispersant.

[0017] Optionally, in the plasma spraying step, the process parameters of the plasma spraying technology are: spraying power of 80 to 120 kW, feeding rate of 20 to 50 ml / min, and spraying distance of 70 to 90 mm.

[0018] Optionally, in the plasma spraying step, the process chamber is vacuumed until the pressure of the process chamber is less than 10 Pa, and an inert gas is filled into the process chamber until the pressure of the process chamber reaches 100-110 kPa to form the inert atmosphere.

[0019] The present invention also provides a plasma spraying device capable of performing the above-mentioned preparation process. The plasma spraying device includes a process chamber and a vacuum pumping component. The process chamber is provided with an air supply port and an air exhaust port. The air supply port is used to connect to an inert gas source, and the air exhaust port is connected to the suction end of the vacuum pumping component. A carrier and a plasma spray gun are provided in the process chamber.

[0020] Optionally, the plasma spraying device also includes a gas circulation system, which includes a circulating air inlet and a circulating air outlet provided in the process chamber, and the circulating air inlet and the circulating air outlet are connected by a circulating pipeline. The circulating pipeline is located outside the process chamber, and the circulating pipeline is provided with a circulating pump and a dust filter.

[0021] In the preparation process provided by the present invention:

[0022] (1) The ZrB2 coating obtained by suspension plasma spraying technology has a higher density and no loss of raw materials compared to magnetron sputtering technology, thereby reducing the preparation cost.

[0023] (2) Rich in 10 The compensation of B powder can effectively improve the ZrB2 coating with the same thickness. 10 B abundance to ensure the effectiveness of ZrB2 coating when applied to nuclear fuel rods as an absorber.

[0024] (3) The setting of inert atmosphere can effectively reduce the high temperature oxidation of ZrB2 and the degree of B ablation caused by the plasma jet entraining air during the plasma spraying process, thereby reducing the N and O content in the ZrB2 coating and improving 10 B abundance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 A schematic diagram of the process of the plasma spraying device provided by the present invention;

[0027] Figure 2 This is a scanning electron microscope image of a cross section of a ZrB2 coating prepared according to the preparation process of Example 2 of the present invention;

[0028] Figure 3 The XRD pattern of the ZrB2 coating prepared according to the preparation process of Example 2 of the present invention;

[0029] Figure 4 The XRD pattern of the ZrB2 coating prepared according to the preparation process of the comparative example.

[0030] Description of reference numerals:

[0031] 100-process chamber; 110-carrier; 120-plasma spray gun; 130-air supply port; 140-exhaust port; 200-vacuum assembly; 210-vacuum valve; 300-gas circulation system; 310-circulating air inlet; 320-circulating air outlet; 330-circulating pipeline; 340-circulating pump; 350-dust filter; 410-air supply pipeline; 420-feeding pipeline; 500-cooling system; 510-water inlet; 520-water outlet; 600-control cabinet. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0035] This embodiment provides a preparation process for a dense zirconium boride coating, including a suspension preparation step and a plasma spraying step, as follows:

[0036] Preparation of suspension: Dispersing medium, ZrB2 powder, 10B powder, binder and dispersant are mixed evenly to obtain a suspension; wherein the content of ZrB2 powder is 2-10wt.% of the total weight of ZrB2 powder and dispersion medium, the content of B powder is 1-3wt.% of ZrB2 powder, the content of binder is not higher than 0.5wt.% of ZrB2 powder, and the content of dispersant is not higher than 0.5wt.% of ZrB2 powder. ZrB2 powder is used as a raw material for liquid feed, rich in 10 B powder is added to the dispersion medium as a compensation raw material to form 10 The mixed liquid with high B abundance is mixed with binder and dispersant and mixed thoroughly to form a suspension with uniform and stable distribution of solid particles. 10 There is no limitation on the order in which the B powder, the binder and the dispersant are added to the dispersion medium.

[0037] Plasma spraying: A ZrB2 coating is formed by spraying a suspension onto the surface of the workpiece using plasma spraying technology in an inert atmosphere. Both the workpiece and the plasma spray gun are placed in an inert atmosphere with a preset vacuum level. Suspension plasma spraying (SPS) is used to evenly apply the suspension onto the surface of the workpiece, forming the ZrB2 coating.

[0038] Among them, in the preparation process of this application:

[0039] (1) The ZrB2 coating obtained by suspension plasma spraying technology has a higher density and no loss of raw materials compared to magnetron sputtering technology, thereby reducing the preparation cost.

[0040] (2) Rich in 10 The compensation of B powder can effectively improve the ZrB2 coating with the same thickness. 10 B abundance to ensure the effectiveness of ZrB2 coating when applied to nuclear fuel rods as an absorber.

[0041] (3) The setting of inert atmosphere can effectively reduce the high temperature oxidation of ZrB2 and the degree of B ablation caused by the plasma jet entraining air during the plasma spraying process, thereby reducing the N and O content in the ZrB2 coating and improving 10 B abundance.

[0042] Therefore, under the premise of not changing the basic process principle of SPS, high density, low N, O content, high 10 The ZrB2 coating has a high B abundance. Specifically, the ZrB2 coating has a porosity of ≤5%, a N element content of ≤0.16 wt.%, an O element content of ≤1.1 wt.%, and a B element content of 15-20 wt.%. The coating is particularly suitable for use as an absorber on the surface of nuclear fuel rods.

[0043] Specifically, in the step of preparing the suspension, deionized water, anhydrous ethanol or a mixture of the two can be selected as the dispersion medium; PVA (Polyvinyl alcohol) can be selected as the binder; and ammonium polyacrylate can be selected as the dispersant.

[0044] Specifically, in this example, in the step of preparing the suspension, the median particle size D of the ZrB2 powder is 50 ≤3μm, median particle size D of B powder 50 ≤3μm. Selecting ZrB2 powder and B powder of this particle size as raw materials to prepare the suspension can ensure that the ZrB2 powder and B powder are fully melted during the plasma high-temperature jet process, effectively reducing microscopic defects such as "splashing" microcracks and unmelted particles formed when using large-sized powders to prepare the coating, thereby further improving the density of the ZrB2 coating.

[0045] In the step of preparing the suspension in this embodiment, the following method can be used to mix the materials uniformly: the dispersion medium, ZrB2 powder, 10 The B powder, binder and dispersant of B are weighed and mixed according to their respective contents to form a mixed liquid. The mixed liquid is added to a ball mill for ball milling until the particle dispersion effect in the mixed liquid reaches D 90 ≤5μm and D 50 ≤3μm, thus obtaining the desired suspension. Ball milling the mixed liquid not only fully disturbs the various materials in the mixed liquid for a fully uniform mixing, but also grinds and crushes the solid materials, making the particle size of ZrB2 powder and B powder smaller and more evenly distributed, effectively reducing the presence of large-sized particles, thereby further ensuring the density and uniformity of the ZrB2 coating obtained by plasma spraying.

[0046] Specifically, the solid phase particle size in the mixed liquid can be tested by a laser particle size analyzer.

[0047] Specifically, in this embodiment, the thickness of the ZrB2 coating is 8 to 20 μm. 10 The effect of B enrichment and changing the thickness of ZrB2 coating is similar. 10 Under the condition of constant B line density, compared with the ZrB2 coating with a thickness of 4 to 6 μm, when the ZrB2 coating thickness increases to about 10 μm, 10 The abundance of B can be increased by 40-50%. The present invention prepares a ZrB2 coating with a thickness of 8 to 20 μm. 10 On the basis of B abundance, the preparation cost of ZrB2 coating can be significantly reduced, which has significant economic benefits.

[0048] Optionally, in this embodiment, the preparation process further includes a step of treating the workpiece to be sprayed: cleaning the workpiece to be sprayed with an organic solvent, sandblasting the cleaned workpiece to be sprayed with 150-220 mesh white corundum, and blowing the surface of the sandblasted workpiece to be sprayed for use in the plasma spraying step; wherein the process conditions for the sandblasting treatment are a pressure of 0.1-0.3 MPa and a sandblasting distance of 60-80 mm; and the pressure of the air blowing treatment is 0.3-0.5 MPa. Specifically, the workpiece to be sprayed can be cleaned with an organic solvent such as anhydrous ethanol or acetone to remove contamination such as oil from the surface of the workpiece to be sprayed; then, the surface of the workpiece to be sprayed is sandblasted, and an air gun is used to remove residual sand particles adhering to the surface of the workpiece to be sprayed after the sandblasting treatment, thereby improving the surface roughness of the workpiece to be sprayed and correspondingly improving the firmness of the sprayed coating adhered to the workpiece surface.

[0049] Specifically, in the plasma spraying step in this embodiment, the process parameters of the plasma spraying technology are: spraying power of 80 to 120 kW, feeding rate of 20 to 50 ml / min, and spraying distance of 70 to 90 mm.

[0050] In this embodiment, in the plasma spraying step, the required inert atmosphere can be obtained by the following operations: vacuuming the process chamber until the pressure of the process chamber is less than 10 Pa, filling the process chamber with inert gas until the pressure of the process chamber reaches 100-110 kPa, thereby forming the required inert atmosphere.

[0051] This embodiment also provides a plasma spraying device capable of performing the above-mentioned preparation process, such as Figure 1 As shown, the plasma spraying device includes a process chamber 100 and a vacuum pumping component 200. The process chamber 100 is provided with an air supply port 130 and an air exhaust port 140. The air supply port 130 is used to connect to an inert gas source, and the air exhaust port 140 is connected to the suction end of the vacuum pumping component 200. A carrier 110 and a plasma spray gun 120 are provided in the process chamber 100.

[0052] During use, the workpiece to be sprayed after sandblasting is mounted on the carrier 110, the air supply port 130 is connected to the inert gas source through the air supply line 410, and the plasma spray gun 120 is connected to the configured suspension through the feed line 420; then the process chamber 100 is closed, the vacuum pumping component 200 is turned on to pump the process chamber 100 to a pressure less than 10Pa, the inert gas source is turned on to fill the process chamber 100 with inert gas as a protective gas through the air supply port 130, and at the same time, the opening of the vacuum valve 210 at the front end of the vacuum pumping component 200 is adjusted to dynamically adjust the pressure in the process chamber 100 so that the internal pressure is maintained at 100-110kPa, thereby forming the required inert atmosphere.

[0053] Then, the plasma spray gun 120 is turned on and the process parameters of the plasma spraying are set as needed, specifically: spraying power 80-120kW, feeding rate 20-50ml / min, spraying distance 70-90mm; thereby obtaining high density, low N, O content, high 10 The ZrB2 coating has a high B abundance. Specifically, the ZrB2 coating has a porosity of ≤5%, a N element content of ≤0.16 wt.%, an O element content of ≤1.1 wt.%, and a B element content of 15 to 20 wt.%.

[0054] Specifically, the carrier 110 can be a rotatable turntable, and the bearing surface of the carrier 110 is provided with a plurality of workstations for clamping the workpiece to be sprayed along its circumference; when in use, the plasma spray gun 120 is set toward the carrier 110, and the carrier 110 is rotated to spray different workpieces to be sprayed, thereby improving production efficiency.

[0055] In this embodiment, Figure 1 As shown, the plasma spraying device can also be provided with a gas circulation system 300, which includes a circulating air inlet 310 and a circulating air outlet 320 provided in the process chamber 100, and the circulating air inlet 310 and the circulating air outlet 320 are connected by a circulating pipeline 330, which is located outside the process chamber 100 and is provided with a circulating pump 340 and a dust filter 350. When setting up the gas circulation system 300, after the inert gas is filled into the process chamber 100 through the inert gas source to obtain the required inert atmosphere, the inert gas source can be turned off to stop the gas supply; during the spraying process, the circulation pump 340 can be turned on, and the circulation pump 340 drives the dust-carrying air flow in the process chamber 100 to enter the circulation pipeline 330 through the circulation outlet 320, and then flows back to the process chamber 100 through the circulation pipeline 330 and the circulation inlet 310 after being filtered by the dust filter 350. In this way, on the basis of ensuring a clean inert atmosphere in the process chamber 100, the protective gas in the process chamber 100 is recycled, reducing the gas consumption caused by the need for the inert gas source to continuously deliver the protective gas during the spraying process, and correspondingly further reducing the production cost.

[0056] In this embodiment, the plasma spraying apparatus may further include a cooling system 500 for cooling the process chamber 100. During the process, the cooling system 500 is used to cool the process chamber 100 to provide a suitable operating temperature for the plasma spray gun 120, the workpiece to be sprayed, and the carrier 110, thereby extending the service life of various components of the plasma spraying apparatus and further reducing production costs.

[0057] Specifically, if Figure 1As shown, the cooling system 500 can be in the form of water cooling, specifically including a water cooling channel arranged inside the cavity wall of the process chamber 100 or attached to the inner wall or outer wall of the cavity wall, the water inlet end 510 of the water cooling channel is connected to the water cooling source through a water cooling pipe, and the water cooling source continuously supplies cooling water to the water cooling channel to achieve continuous cooling treatment of the process chamber 100; or the water inlet end 510 and the water outlet end 520 of the water cooling channel are connected through a water cooling pipe, and the water cooling pipe is equipped with a driving pump and a cooling component, and the driving pump can drive the water cooling pipe and the water cooling channel to form a circulation flow of cooling water in the circulation channel, wherein the cooling water will be cooled in the process of flowing through the cooling component, and the process of flowing through the water cooling channel can absorb heat and cool the process chamber 100, thereby realizing the recycling of cooling water.

[0058] In addition to cooling the process chamber 100, the cooling system 500 can also simultaneously cool the circulating gas in the circulation pipeline 330 of the gas circulation system 300 to improve the cooling effect of the gas environment in the process chamber 100; of course, in addition to using the cooling system 500 to cool the circulating gas, a cooling component can also be directly integrated into the circulation pump 340, and the circulating gas flowing through the circulation pump 340 can be cooled by the cooling component.

[0059] Specifically, if Figure 1 As shown, a control cabinet 600 can be provided, in which the control module is communicatively connected to the plasma spray gun 120, the vacuum pumping component 200, the gas circulation system 300, the cooling system 500 and the inert gas source. By operating the control panel of the control cabinet 600, process control of the above components and systems can be achieved, including sequence control of the vacuum pumping component 200 and the inert gas source, pressure control in the process chamber 100, liquid supply control of the suspension, flow control of the protective gas, setting of process parameters for plasma spraying, etc.

[0060] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0061] Example 1

[0062] Step 1: Suspension preparation:

[0063] ① Using deionized water as the dispersion medium, the median particle size D 50 The ZrB2 powder with a diameter of 2.5 μm was used as the raw material of the liquid. According to the single preparation requirements, the ZrB2 powder was weighed and a certain amount of deionized water was added to prepare the liquid with a solid content of 2.0 wt.%. Relative to the mass of the ZrB2 powder, 0.1 wt.% of PVA was added as a binder, 0.1 wt.% of ammonium polyacrylate was added as a dispersant, and 1 wt.% of a rich 10 B powder is used as a compensating raw material to obtain a mixed liquid, wherein the mixed liquid is rich in 10The median particle size D of B powder 50 2.8μm;

[0064] ② Add the prepared mixed liquid into the ball milling equipment for ball milling and dispersion, and use a laser particle size analyzer to test the particle size of the solid particles in the mixed liquid. 90 4.2μm, D 50 The particle size is 2.5 μm, forming a ZrB2 suspension with good dispersion effect.

[0065] Step 2: Preparation of workpiece to be sprayed and adjustment of controlled atmosphere:

[0066] ① Use anhydrous ethanol to clean the workpiece to be sprayed; then use 150-220 mesh white corundum to sandblast the cleaned workpiece to be sprayed, wherein the sandblasting process conditions are a pressure of 0.1MPa and a sandblasting distance of 80mm; then use an air gun to blow air on the surface of the workpiece to remove residual sand particles adhered to the surface of the workpiece during the sandblasting process, wherein the blowing pressure is 0.3MPa;

[0067] ② Clamp the workpiece to be sprayed after sandblasting on the carrier inside the process chamber;

[0068] ③ Turn on the vacuum pumping assembly to vacuum the process chamber. When the pressure in the process chamber is less than 8.8 Pa, fill the process chamber with argon as a protective gas, turn on the circulation pump and adjust the opening of the vacuum valve on the front side of the vacuum pumping assembly to make the pressure in the process chamber reach and maintain it at 100-110 kPa;

[0069] Step 3: Plasma spraying:

[0070] ① Turn on the plasma spray gun to spray the suspension onto the surface of the workpiece to be sprayed, thereby obtaining a ZrB2 coating. The spraying process parameters are set as follows: spraying power of 120 kW, feed rate of 50 ml / min, and spraying distance of 70 mm.

[0071] Relevant tests were performed on the ZrB2 coating prepared in Example 1. The porosity of the ZrB2 coating was 5.0%, the coating thickness was 15 μm, the N element content in the coating was 0.16 wt.%, the O element content was 1.1 wt.%, and the B element content was 15 wt.%.

[0072] Example 2

[0073] Step 1: Suspension preparation:

[0074] ① Using deionized water as the dispersion medium, the median particle size D 50The ZrB2 powder with a diameter of 2.2 μm was used as the raw material for the liquid. According to the single preparation requirements, the ZrB2 powder was weighed and a certain amount of deionized water was added to prepare the liquid with a solid content of 10.0 wt.%. Relative to the mass of the ZrB2 powder, 0.48 wt.% of PVA was added as a binder, 0.48 wt.% of ammonium polyacrylate was added as a dispersant, and 2 wt.% of a rich 10 B powder is used as a compensating raw material to obtain a mixed liquid, wherein the mixed liquid is rich in 10 The median particle size D of B powder 50 2.3μm;

[0075] ② Add the prepared mixed liquid into the ball milling equipment for ball milling and dispersion, and use a laser particle size analyzer to test the particle size of the solid particles in the mixed liquid. 90 4.8μm, D 50 The particle size is 2.2 μm, forming a ZrB2 suspension with good dispersion effect.

[0076] Step 2: Preparation of workpiece to be sprayed and adjustment of controlled atmosphere:

[0077] ① Use anhydrous ethanol to clean the workpiece to be sprayed; then use 150-220 mesh white corundum to sandblast the cleaned workpiece to be sprayed, wherein the sandblasting process conditions are a pressure of 0.3MPa and a sandblasting distance of 60mm; then use an air gun to blow air on the surface of the workpiece to remove residual sand particles adhered to the surface of the workpiece during the sandblasting process, wherein the blowing pressure is 0.3MPa;

[0078] ② Clamp the workpiece to be sprayed after sandblasting on the carrier inside the process chamber;

[0079] ③ Turn on the vacuum pumping assembly to vacuum the process chamber. When the pressure in the process chamber is less than 9.2 Pa, fill the process chamber with argon as a protective gas, turn on the circulation pump and adjust the opening of the vacuum valve on the front side of the vacuum pumping assembly to make the pressure in the process chamber reach and maintain it at 100-110 kPa;

[0080] Step 3: Plasma spraying:

[0081] ① Turn on the plasma spray gun to spray the suspension onto the surface of the workpiece to be sprayed, thereby obtaining a ZrB2 coating. The spraying process parameters are set as follows: spraying power of 80 kW, feed rate of 20 ml / min, and spraying distance of 90 mm.

[0082] Relevant tests were performed on the ZrB2 coating prepared in Example 2. The porosity of the ZrB2 coating was 4.5%, the coating thickness was 20 μm, the N element content in the coating was 0.09 wt.%, the O element content was 0.93 wt.%, and the B element content was 20 wt.%.

[0083] Figure 2 This is a cross-sectional scanning electron microscope image of the ZrB2 coating prepared according to the preparation process of Example 2 of the present invention, showing an accuracy of 50 μm; Figure 2 It can be seen that the ZrB2 coating on the upper layer has higher density. Figure 3 This is the XRD pattern of the ZrB2 coating prepared according to the preparation process of Example 2 of the present invention; the XRD pattern has only a weak ZrO2 diffraction peak, indicating that the degree of B ablation is low, which effectively reduces the N content and O content in the ZrB2 coating.

[0084] Example 3

[0085] Step 1: Suspension preparation:

[0086] ① Using deionized water as the dispersion medium, the median particle size D 50 The ZrB2 powder with a diameter of 3.0 μm was used as the raw material of the liquid. According to the single preparation requirements, the ZrB2 powder was weighed and a certain amount of deionized water was added to prepare the liquid with a solid content of 5.0 wt.%. Relative to the mass of the ZrB2 powder, 0.28 wt.% of PVA was added as a binder, 0.28 wt.% of ammonium polyacrylate was added as a dispersant, and 2.5 wt.% of a rich 10 B powder is used as a compensating raw material to obtain a mixed liquid, wherein the mixed liquid is rich in 10 The median particle size D of B powder 50 2.5μm;

[0087] ② Add the prepared mixed liquid into the ball milling equipment for ball milling and dispersion, and use a laser particle size analyzer to test the particle size of the solid particles in the mixed liquid. 90 4.6μm, D 50 The particle size is 2.8 μm, forming a ZrB2 suspension with good dispersion effect.

[0088] Step 2: Preparation of workpiece to be sprayed and adjustment of controlled atmosphere:

[0089] ① Use anhydrous ethanol to clean the workpiece to be sprayed; then use 150-220 mesh white corundum to sandblast the cleaned workpiece to be sprayed, wherein the sandblasting process conditions are a pressure of 0.2MPa and a sandblasting distance of 70mm; then use an air gun to blow air on the surface of the workpiece to remove residual sand particles adhered to the surface of the workpiece during the sandblasting process, wherein the blowing pressure is 0.4MPa;

[0090] ② Clamp the workpiece to be sprayed after sandblasting on the carrier inside the process chamber;

[0091] ③ Turn on the vacuum pumping assembly to vacuum the process chamber. When the pressure in the process chamber is less than 8.8 Pa, fill the process chamber with argon as a protective gas, turn on the circulation pump and adjust the opening of the vacuum valve on the front side of the vacuum pumping assembly to make the pressure in the process chamber reach and maintain it at 100-110 kPa;

[0092] Step 3: Plasma spraying:

[0093] ① Turn on the plasma spray gun to spray the suspension onto the surface of the workpiece to be sprayed, thereby obtaining a ZrB2 coating. The spraying process parameters are set as follows: spraying power of 100 kW, feed rate of 30 ml / min, and spraying distance of 80 mm.

[0094] The ZrB2 coating prepared in Example 3 was subjected to relevant tests. The porosity of the ZrB2 coating was 4.3%, the coating thickness was 10 μm, the N element content in the coating was 0.12 wt.%, the O element content was 0.9 wt.%, and the B element content was 17 wt.%.

[0095] Example 4

[0096] Step 1: Suspension preparation:

[0097] ① Deionized water and anhydrous ethanol were mixed in a mass ratio of 1:1 as the dispersion medium, and the median particle size D 50 The ZrB2 powder with a diameter of 2.8 μm was used as the raw material for the liquid. According to the single preparation requirements, the ZrB2 powder was weighed and a certain amount of deionized water was added to prepare the liquid with a solid content of 3.0 wt.%. Relative to the mass of the ZrB2 powder, 0.15 wt.% of PVA was added as a binder, 0.15 wt.% of ammonium polyacrylate was added as a dispersant, and 1.5 wt.% of a rich 10 B powder is used as a compensating raw material to obtain a mixed liquid, wherein the mixed liquid is rich in 10 The median particle size D of B powder 50 2.6μm;

[0098] ② Add the prepared mixed liquid into the ball milling equipment for ball milling and dispersion, and use a laser particle size analyzer to test the particle size of the solid particles in the mixed liquid. 90 3.8μm, D 50 The particle size is 2.6 μm, forming a ZrB2 suspension with good dispersion effect.

[0099] Step 2: Preparation of workpiece to be sprayed and adjustment of controlled atmosphere:

[0100] ① Use anhydrous ethanol to clean the workpiece to be sprayed; then use 150-220 mesh white corundum to sandblast the cleaned workpiece to be sprayed, wherein the sandblasting process conditions are a pressure of 0.3MPa and a sandblasting distance of 60mm; then use an air gun to blow air on the surface of the workpiece to remove residual sand particles adhered to the surface of the workpiece during the sandblasting process, wherein the blowing pressure is 0.3MPa;

[0101] ② Clamp the workpiece to be sprayed after sandblasting on the carrier inside the process chamber;

[0102] ③ Turn on the vacuum pumping assembly to vacuum the process chamber. When the pressure in the process chamber is less than 8.8 Pa, fill the process chamber with argon as a protective gas, turn on the circulation pump and adjust the opening of the vacuum valve on the front side of the vacuum pumping assembly to make the pressure in the process chamber reach and maintain it at 100-110 kPa;

[0103] Step 3: Plasma spraying:

[0104] ① Turn on the plasma spray gun to spray the suspension onto the surface of the workpiece to be sprayed, thereby obtaining a ZrB2 coating. The spraying process parameters are set as follows: spraying power of 110 kW, feed rate of 25 ml / min, and spraying distance of 75 mm.

[0105] The ZrB2 coating prepared in Example 4 was subjected to relevant tests. The porosity of the ZrB2 coating was 4.2%, the coating thickness was 8 μm, the N content in the coating was 0.13 wt.%, the O content was 0.92 wt.%, and the B content was 16 wt.%.

[0106] Example 5

[0107] Step 1: Suspension preparation:

[0108] ① Using anhydrous ethanol as the dispersion medium, the median particle size D 50 The ZrB2 powder with a diameter of 2.7 μm was used as the raw material of the liquid. According to the single preparation requirements, the ZrB2 powder was weighed and a certain amount of deionized water was added to prepare the liquid with a solid content of 8.0 wt.%. Relative to the mass of the ZrB2 powder, 0.32 wt.% of PVA was added as a binder, 0.32 wt.% of ammonium polyacrylate was added as a dispersant, and 3 wt.% of a rich 10 B powder is used as a compensating raw material to obtain a mixed liquid, wherein the mixed liquid is rich in 10 The median particle size D of B powder 50 2.4μm;

[0109] ② Add the prepared mixed liquid into the ball milling equipment for ball milling and dispersion, and use a laser particle size analyzer to test the particle size of the solid particles in the mixed liquid. 90 3.9μm, D 50 The particle size is 2.0 μm, forming a ZrB2 suspension with good dispersion effect.

[0110] Step 2: Preparation of workpiece to be sprayed and adjustment of controlled atmosphere:

[0111] ① Use anhydrous ethanol to clean the workpiece to be sprayed; then use 150-220 mesh white corundum to sandblast the cleaned workpiece to be sprayed, wherein the sandblasting process conditions are a pressure of 0.2MPa and a sandblasting distance of 80mm; then use an air gun to blow air on the surface of the workpiece to remove residual sand particles adhered to the surface of the workpiece during the sandblasting process, wherein the blowing pressure is 0.3MPa;

[0112] ② Clamp the workpiece to be sprayed after sandblasting on the carrier inside the process chamber;

[0113] ③ Turn on the vacuum pumping assembly to vacuum the process chamber. When the pressure in the process chamber is less than 8.8 Pa, fill the process chamber with argon as a protective gas, turn on the circulation pump and adjust the opening of the vacuum valve on the front side of the vacuum pumping assembly to make the pressure in the process chamber reach and maintain it at 100-110 kPa;

[0114] Step 3: Plasma spraying:

[0115] ① Turn on the plasma spray gun to spray the suspension onto the surface of the workpiece to be sprayed, thereby obtaining a ZrB2 coating. The spraying process parameters are set as follows: spraying power of 90 kW, feed rate of 40 ml / min, and spraying distance of 85 mm.

[0116] The ZrB2 coating prepared in Example 5 was subjected to relevant tests. The porosity of the ZrB2 coating was 3.8%, the coating thickness was 12 μm, the N element content in the coating was 0.15 wt.%, the O element content was 0.97 wt.%, and the B element content was 18 wt.%.

[0117] Comparative Example

[0118] In the comparative example, the controlled atmosphere adjustment in step 2 of Example 2 was replaced with the atmospheric environment, and the process parameters of the remaining step 1, suspension preparation, step 2, workpiece treatment to be sprayed, and step 3, plasma spraying were the same as those in Example 2.

[0119] The ZrB2 coating prepared according to the comparative example had a porosity of 4.3%, a coating thickness of 13 μm, a N content of 1.06 wt.%, an O content of 8.7 wt.%, and a B content of 12 wt.%. Compared with the ZrB2 coating prepared in Example 2, the ZrB2 coating prepared in the comparative example had significantly increased N and O contents, and a slightly decreased B content.

[0120] Figure 4 This is the XRD pattern of the ZrB2 coating prepared according to the preparation process of the comparative example; there is an obvious ZrO2 diffraction peak in the pattern, indicating that B ablation is obvious, resulting in excessive N and O contents in the ZrB2 coating.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for preparing a dense zirconium boride coating, characterized in that: The following steps are involved: Preparation of suspension: Dispersing medium, ZrB2 powder, 10 B powder, a binder and a dispersant are uniformly mixed to obtain a suspension; wherein deionized water, anhydrous ethanol or a mixture of the two is selected as the dispersion medium, PVA is selected as the binder, and ammonium polyacrylate is selected as the dispersant; The content of ZrB2 powder is 2-10 wt.% of the total weight of ZrB2 powder and dispersion medium, the content of B powder is 1-3 wt.% of ZrB2 powder, the content of binder is not higher than 0.5 wt.% of ZrB2 powder, and the content of dispersant is not higher than 0.5 wt.% of ZrB2 powder. Plasma spraying: In an inert atmosphere, a suspension is sprayed onto the surface of the workpiece to be sprayed using plasma spraying technology to obtain a ZrB2 coating with a thickness of 8 to 20 μm. The process chamber is evacuated until the pressure of the process chamber is less than 10 Pa, and an inert gas is filled into the process chamber until the pressure of the process chamber reaches 100 to 110 kPa to form the inert atmosphere. The process parameters of the plasma spraying technology are: spraying power of 80 to 120 kW, feed rate of 20 to 50 ml / min, and spraying distance of 70 to 90 mm.

2. The preparation process according to claim 1, characterized in that In the step of preparing the suspension, the median particle size D of the ZrB2 powder 50 ≤3μm, median particle size D of B powder 50 ≤3μm.

3. The preparation process according to claim 1, characterized in that In the step of preparing the suspension, the dispersion medium, ZrB2 powder, and 10 The B powder, binder and dispersant of B are weighed and mixed according to their respective contents to form a mixed liquid, and the mixed liquid is ball milled until the particle dispersion effect in the mixed liquid reaches D 90 ≤5μm and D 50 ≤3 μm to obtain the suspension.

4. The preparation process according to claim 1, characterized in that The preparation process also includes a step of treating the workpiece to be sprayed: using an organic solvent to clean the workpiece to be sprayed, sandblasting the cleaned workpiece to be sprayed with 150-220 mesh white corundum, and blowing the surface of the sandblasted workpiece to be sprayed for the plasma spraying step; The process conditions for sandblasting are a pressure of 0.1 to 0.3 MPa and a sandblasting distance of 60 to 80 mm; the pressure for air blowing is 0.3 to 0.5 MPa.

Images