CN112652411B - Nuclear reactor pressure vessel lower seal head with high-durability composite coating structure and preparation method thereof - Google Patents
Nuclear reactor pressure vessel lower seal head with high-durability composite coating structure and preparation method thereof Download PDFInfo
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- CN112652411B CN112652411B CN201910962376.3A CN201910962376A CN112652411B CN 112652411 B CN112652411 B CN 112652411B CN 201910962376 A CN201910962376 A CN 201910962376A CN 112652411 B CN112652411 B CN 112652411B
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- 239000011248 coating agent Substances 0.000 title abstract description 49
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- 238000002360 preparation method Methods 0.000 title abstract description 9
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- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 12
- 239000003963 antioxidant agent Substances 0.000 claims description 10
- 230000003078 antioxidant effect Effects 0.000 claims description 10
- 239000003350 kerosene Substances 0.000 claims description 10
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 9
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- 239000010963 304 stainless steel Substances 0.000 claims description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 6
- 229910000589 SAE 304 stainless steel Inorganic materials 0.000 claims description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- 238000005530 etching Methods 0.000 claims description 6
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- 229910052782 aluminium Inorganic materials 0.000 claims description 5
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
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- 229910000838 Al alloy Inorganic materials 0.000 claims description 3
- 229910000604 Ferrochrome Inorganic materials 0.000 claims description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 3
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- 229910052749 magnesium Inorganic materials 0.000 claims description 3
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Classifications
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C13/00—Pressure vessels; Containment vessels; Containment in general
- G21C13/02—Details
- G21C13/028—Seals, e.g. for pressure vessels or containment vessels
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C21/00—Apparatus or processes specially adapted to the manufacture of reactors or parts thereof
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
The invention discloses a nuclear reactor pressure vessel bottom head and a preparation method thereof. The nuclear reactor pressure vessel bottom head includes: a lower end socket substrate; the oxidation resistant bottom layer is formed on at least part of the surface of the outer wall of the lower head base body; and the porous metal top layer is formed on at least part of the surface of the oxidation resistant bottom layer, which is far away from the outer wall of the lower head base body. The composite coating adopted by the lower seal head of the nuclear reactor pressure vessel can obviously improve the CHF limit value of the outer wall surface of the lower seal head, and lays a foundation for improving the effectiveness of IVR of the high-power reactor.
Description
Technical Field
The invention relates to the technical field of nuclear reactor thermohydraulic power, in particular to a nuclear reactor pressure vessel lower end socket with a high-durability composite coating and a preparation method thereof.
Background
Stagnation in melt pressure vessels (IVR) has found wide application in the nuclear industry in recent years as a key technology for alleviating serious accidents. External cooling of the reactor pressure vessel (ERVC) is an important solution to achieving IVR. When the heat flux density of the lower end enclosure of the pressure vessel is smaller than the critical heat flux density (CHF) of the corresponding position of the outer surface of the pressure vessel, the cooling of the outer wall surface of the pressure vessel can be ensured, and the integrity of the pressure vessel can be maintained. CHF therefore determines the limit of the cooling capacity of the ERVC. The greater the CHF value, the greater the safety margin of the pressure vessel and the greater the feasibility of the IVR-ERVC procedure. The IVR-ERVC strategy has enough safety margin on a medium-and-small-power reactor, but the heat flux density led out from the lower end socket of the pressure vessel of the high-power reactor is increased, so that the CHF limit value is required to be improved to further improve the IVR effectiveness. Numerous studies have shown that the structural properties of the heated surface have a significant impact on CHF, so altering the structural properties of the outer wall surface of the pressure vessel is a viable technique for enhancing CHF. In the process of modifying the surface structure to enhance CHF, it is generally contemplated to process a specific structure on the heating surface or to prepare a porous coating on the heating surface. For example, micro/nano structures, visible groove structures, net groove communicated array holes, raised structures and the like are manufactured on the surface by adopting an advanced processing technology, or cavities and tunnels formed by porous coatings are manufactured on the heating surface by adopting a related coating preparation method, so that the surface structure characteristics are changed, and the boiling heat transfer process is influenced, thereby achieving the purposes of enhancing heat exchange and enhancing CHF.
It has been shown that the preparation of a metallic porous coating with interconnected micropores on the outer wall surface of a pressure vessel doubles the CHF value of the pressure vessel surface. However, a single porous metal coating may be difficult to meet the long life requirements of a nuclear reactor for a pressure vessel outer wall coating. The pressure vessel is generally made of low alloy steel with low chromium content, and the outer wall surface of the pressure vessel exposed in the air for a long time is extremely easy to oxidize at the operating temperature (300 ℃). Because the porous coating cannot isolate the contact between the external air and the outer wall of the pressure vessel, a layer of oxide can be formed between the surface of the pressure vessel and the porous coating during long-term operation, and the thickening of the oxide can lead to the peeling of the porous coating in a short time. Therefore, development of a coating structure design capable of remarkably improving the critical heat flux density of the outer wall surface of a pressure vessel and having long service life and a corresponding method for preparing a large-area coating are needed.
In the technical scheme disclosed in the patent CN103903658A, a machining mode is adopted, a groove structure, a net groove communication array hole, a protruding structure and the like are machined on a heating surface, and the surface structure characteristics are changed, so that the CHF value of the heating surface is improved by more than 50%. If the technology is popularized to engineering practice, the safety margin of the passive cooling technology of the nuclear power station can be greatly improved. However, in engineering application, the process difficulty of processing a special surface structure on the surface of a lower end enclosure of a reactor pressure vessel, especially on the surface of a lower end enclosure of a in-service reactor is high, and the mechanical properties after surface treatment with the special structure are required to be further evaluated. On the other hand, the outer wall surface of the pressure vessel exposed to the air for a long period of time is extremely susceptible to oxidation at the operating temperature, and the holes and grooves machined in the outer wall surface of the pressure vessel may be corroded and vanished.
In the technical scheme disclosed in patent CN102303117A, ti powder, al powder and Nb powder are mixed and dried, deposited on a metal substrate at one time, and then subjected to vacuum heat preservation sintering by adopting a three-stage sintering process, so that the TiAl-based alloy porous coating is prepared on the metal substrate. The TiAl-based porous coating prepared by the technology has uniform thickness and pores, is firm, is not easy to fall off, and is suitable for plate-type or tube-type heat exchangers in the fields of chemical industry, petroleum, metallurgy, sea water desalination, high-temperature heat exchange and the like. The method for preparing the porous coating by adopting powder high-temperature sintering or electrodeposition is more suitable for equipment with smaller size, and does not have the capability of preparing the coating on the outer wall surface of the lower end socket of the large-size reactor pressure vessel. On the other hand, the problem of the easy oxidation of the low carbon steel-based surface is not mentioned and considered in this technology.
In view of the above, the existing nuclear reactor pressure vessel bottom head and the surface strengthening technology thereof have yet to be improved.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent. To this end, an object of the present invention is to propose a nuclear reactor pressure vessel bottom head with a highly durable composite coating and a method for its preparation. The composite coating adopted by the lower seal head of the nuclear reactor pressure vessel can obviously improve the CHF limit value of the outer wall surface of the lower seal head, and lays a foundation for improving the effectiveness of IVR of the high-power reactor.
In one aspect of the invention, a nuclear reactor pressure vessel bottom head is provided. According to an embodiment of the invention, the nuclear reactor pressure vessel bottom head comprises: a lower end socket substrate; the oxidation resistant bottom layer is formed on at least part of the surface of the outer wall of the lower head base body; and the porous metal top layer is formed on at least part of the surface of the oxidation resistant bottom layer, which is far away from the outer wall of the lower head base body.
According to the nuclear reactor pressure vessel bottom head provided by the embodiment of the invention, the outer wall surface of the bottom head is provided with the composite coating structure comprising the oxidation resistant bottom layer and the porous metal top layer, wherein the oxidation resistant bottom layer has excellent oxidation resistance, can isolate external air from contacting with the surface of the pressure vessel bottom head after passing through the porous metal top layer, and prevents coating peeling caused by excessive growth of interface oxides, so that the bottom head can be ensured not to reduce the porosity of the porous metal top layer due to internal oxidation of the composite coating in the use process, and the durability of the coating is enhanced; the porous metal top layer can obviously increase the contact area between the outer wall surface of the lower end enclosure of the pressure vessel and cooling water, and the mutually communicated pores are favorable for escaping generated water vapor, so that the obstruction of a vapor film to the heat transfer between the cooling water and the surface of the pressure vessel is avoided, the boiling heat exchange of the outer wall surface of the lower end enclosure of the pressure vessel is enhanced, and the critical heat flow density is improved. Therefore, the composite coating adopted by the lower seal head of the nuclear reactor pressure vessel can obviously improve the CHF limit value of the outer wall surface of the lower seal head, and lays a foundation for improving the effectiveness of IVR of the high-power reactor.
In addition, the nuclear reactor pressure vessel bottom head according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, the bottom head substrate is formed from at least one selected from SA508 steel, SA533 steel.
In some embodiments of the invention, the oxidation resistant underlayer is formed of an oxidation resistant alloy material.
In some embodiments of the present invention, the oxidation resistant alloy material comprises at least one selected from the group consisting of FeCr-based stainless steel materials, niCr-based alloys, coNiCr-based alloys.
In some embodiments of the invention, the porous metal top layer is formed from at least one selected from the group consisting of 304 stainless steel, 310 stainless steel, 316 stainless steel.
In some embodiments of the invention, the thickness of the oxidation resistant underlayer is 80 to 150 μm.
In some embodiments of the invention, the porous metal top layer has a thickness of 250-350 μm.
In another aspect of the invention, a method of making a nuclear reactor pressure vessel bottom head of the above-described embodiments is provided. According to an embodiment of the invention, the method comprises: the method comprises the steps of (1) preprocessing the outer wall of a lower end socket substrate; (2) Spraying an antioxidant alloy material on at least part of the surface of the outer wall of the lower head matrix to form an antioxidant bottom layer; (3) Mixing a metal pore-forming agent with a top layer alloy material, and spraying at least part of the surface of the antioxidation bottom layer, which is far away from the outer wall of the bottom head substrate, with the obtained mixed material to form a metal top layer; and (4) removing the metal pore-forming agent in the metal top layer to form a porous metal top layer, thereby obtaining the nuclear reactor pressure vessel bottom head. Therefore, the method can prepare the composite coating structure comprising the antioxidation bottom layer and the porous metal top layer on the outer wall surface of the lower seal head of the nuclear reactor pressure vessel in a large area, and the preparation process can not generate thermal influence on the base material and can not degrade the mechanical properties of the base material. In addition, the method has the advantages of low production cost and high production efficiency.
In addition, the method for preparing a nuclear reactor pressure vessel bottom head according to the above-described embodiments of the present invention may further have the following additional technical features:
in some embodiments of the invention, the oxidation resistant underlayer is formed by a kerosene fuel supersonic flame spraying process, the process parameters of which include: the flow rate of kerosene is 20-25L/h, the flow rate of oxygen is 1800-1900 slm, the powder feeding rate is 60-70 g/min, the scanning speed of a spray gun is 900-1100 mm/s, and the spraying times are 4-8 times.
In some embodiments of the invention, the mass ratio of the metal pore former to the top layer alloy material is (3-5): 5-7.
In some embodiments of the invention, the oxidation resistant alloy material has an average particle size of 15 to 45 μm.
In some embodiments of the invention, the top layer alloy material has an average particle size of 30 to 50 μm.
In some embodiments of the invention, the metal pore former comprises at least one selected from the group consisting of aluminum, aluminum alloys, magnesium, and magnesium alloys.
In some embodiments of the invention, the metal pore former has an average particle size of 30 to 60 μm.
In some embodiments of the invention, the metallic top layer is formed by a cold spray process, the process parameters of which include: the gas temperature is 450-550 ℃, the main gas pressure is 3.0-4.0 MPa, the powder feeding speed is 45-55 g/min, the moving speed of the spray gun is 150-250 mm/s, and the spraying distance is 15-25 mm.
In some embodiments of the present invention, an etching medium is contacted with the metal top layer to remove the metal pore former.
In some embodiments of the invention, the etching medium is at least one selected from the group consisting of aqueous sodium hydroxide solution, hydrochloric acid, and acetic acid.
In some embodiments of the invention, the contacting is accomplished at 25-35 ℃ for 45-75 minutes.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic flow diagram of a method of preparing a nuclear reactor pressure vessel bottom head in accordance with one embodiment of the invention;
FIG. 2 is a cross-sectional view of a composite coating on the outer wall surface of the bottom head of a nuclear reactor pressure vessel prepared in example 1;
FIG. 3 is a cross-sectional profile view of the pore structure in the porous metal top layer in the composite coating on the outer wall surface of the bottom head of the nuclear reactor pressure vessel prepared in example 1.
Detailed Description
Embodiments of the present invention are described in detail below. The following examples are illustrative only and are not to be construed as limiting the invention. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.
In one aspect of the invention, a nuclear reactor pressure vessel bottom head is provided. According to an embodiment of the invention, the nuclear reactor pressure vessel bottom head comprises: a lower end socket substrate; the oxidation resistant bottom layer is formed on at least part of the surface of the outer wall of the lower head base body; and the porous metal top layer is formed on at least part of the surface of the oxidation resistant bottom layer, which is far away from the outer wall of the lower head base body.
According to the nuclear reactor pressure vessel bottom head provided by the embodiment of the invention, the outer wall surface of the bottom head is provided with the composite coating structure comprising the oxidation resistant bottom layer and the porous metal top layer, wherein the oxidation resistant bottom layer has excellent oxidation resistance, can isolate external air from contacting with the surface of the pressure vessel bottom head after passing through the porous metal top layer, and prevents coating peeling caused by excessive growth of interface oxides, so that the bottom head can be ensured not to reduce the porosity of the porous metal top layer due to internal oxidation of the composite coating in the use process, and the durability of the coating is enhanced; the porous metal top layer can obviously increase the contact area between the outer wall surface of the lower end enclosure of the pressure vessel and cooling water, and the mutually communicated pores are favorable for escaping generated water vapor, so that the obstruction of a vapor film to the heat transfer between the cooling water and the surface of the pressure vessel is avoided, the boiling heat exchange of the outer wall surface of the lower end enclosure of the pressure vessel is enhanced, and the critical heat flow density is improved. Therefore, the composite coating adopted by the lower seal head of the nuclear reactor pressure vessel can obviously improve the CHF limit value of the outer wall surface of the lower seal head, and lays a foundation for improving the effectiveness of IVR of the high-power reactor.
A nuclear reactor pressure vessel bottom head in accordance with an embodiment of the present invention is described in further detail below.
The specific material of the bottom head base according to the embodiment of the present invention is not particularly limited, and may be any bottom head base commonly used in the art, and may be formed of at least one of low carbon steel for a pressure vessel selected from SA508 steel and SA533 steel, for example. That is, the composite coating provided by the invention has no special limitation on the specific material of the bottom head matrix, and can be used for reinforcing the bottom head matrix of the conventional nuclear reactor pressure vessel so as to improve the critical heat flow density and durability of the bottom head matrix.
According to an embodiment of the present invention, the above-mentioned oxidation-resistant underlayer is formed of an oxidation-resistant alloy material. Specifically, the oxidation resistant alloy material includes at least one selected from FeCr-based stainless steel materials (e.g., 304 stainless steel, 310 stainless steel, 316 stainless steel, etc.), niCr-based alloys (e.g., niCr20CuMo, niCr20TiAl, etc.), coNiCr-based alloys (e.g., niCoCrAlY, coNiCrA WBSi, etc.). The alloy material has excellent oxidation resistance under the atmospheric condition of 200-350 ℃, can effectively isolate external air from contacting with the surface of the lower seal head of the pressure vessel after passing through the porous metal top layer, prevents the coating from peeling caused by excessive growth of interface oxides, further can ensure that the porosity of the porous metal top layer is not reduced due to internal oxidation of the composite coating in the use process of the lower seal head, and enhances the durability of the coating.
According to an embodiment of the present invention, the porous metal top layer may be formed of at least one selected from 304 stainless steel, 310 stainless steel, 316 stainless steel, and the like. The porous metal top layer formed by the metal material can obviously increase the contact area between the outer wall surface of the lower end enclosure of the pressure vessel and cooling water, and the mutually communicated pores are favorable for escaping generated water vapor, so that the blockage of a vapor film on the heat transfer between the cooling water and the surface of the pressure vessel is avoided, the boiling heat exchange of the outer wall surface of the lower end enclosure of the pressure vessel is enhanced, and the critical heat flow density is improved.
According to an embodiment of the present invention, the thickness of the above-mentioned oxidation-resistant primer layer may be 80 to 150 μm, for example 80 μm, 100 μm, 120 μm, 150 μm, etc. By controlling the thickness of the oxidation-resistant bottom layer within the above range, the ability of the oxidation-resistant bottom layer to feel outside air can be further improved, thereby further improving the durability of the composite coating as a whole.
According to embodiments of the present invention, the thickness of the porous metal top layer may be 250-350 μm, such as 250 μm, 270 μm, 300 μm, 320 μm, 350 μm, etc. By controlling the thickness of the porous metal top layer in the above range, the contact area between the porous metal top layer and the cooling water can be further increased, thereby further increasing the critical heat flux density of the material.
In another aspect of the invention, a method of making a nuclear reactor pressure vessel bottom head of the above-described embodiments is provided. According to an embodiment of the invention, the method comprises: the method comprises the steps of (1) preprocessing the outer wall of a lower end socket substrate; (2) Spraying an antioxidant alloy material on at least part of the surface of the outer wall of the lower seal head matrix to form an antioxidant bottom layer; (3) Mixing a metal pore-forming agent with the top layer alloy material, and spraying at least part of the surface of the antioxidation bottom layer far away from the outer wall of the bottom head matrix by using the obtained mixed material to form a metal top layer; and (4) removing the metal pore-forming agent in the metal top layer to form a porous metal top layer, thereby obtaining the nuclear reactor pressure vessel bottom head. Therefore, the method can prepare the composite coating structure comprising the antioxidation bottom layer and the porous metal top layer on the outer wall surface of the lower seal head of the nuclear reactor pressure vessel in a large area, and the preparation process can not generate thermal influence on the base material and can not degrade the mechanical properties of the base material. In addition, the method has the advantages of low production cost and high production efficiency.
A method of manufacturing a nuclear reactor pressure vessel according to an embodiment of the present invention is described in further detail below. Referring to fig. 1, according to an embodiment of the present invention, the method includes:
s100: substrate pretreatment
In the step, the outer wall of the lower end socket substrate is pretreated. According to a specific example of the invention, the surface of the metal substrate on the outer wall of the lower seal head base body can be roughened by adopting a sand blasting method, and then the surface of the substrate is cleaned by adopting compressed air. Therefore, the roughness of the metal base material on the outer wall of the bottom head base body can be effectively improved, and the binding force between the metal base material and the antioxidation bottom layer material is effectively improved.
S200: forming an oxidation-resistant bottom layer
In the step, an antioxidant alloy material is utilized to spray and form an antioxidant bottom layer on at least part of the surface of the outer wall of the lower end socket substrate. According to the embodiment of the invention, the oxidation resistant alloy material can be provided in the form of powder and is formed on at least part of the surface of the outer wall of the bottom head base body by a cold spraying or thermal spraying (preferably thermal spraying) method, and the cold spraying or thermal spraying method is suitable for preparing the oxidation resistant bottom layer in a large area and has strong operability.
According to an embodiment of the present invention, the above-mentioned oxidation-resistant alloy material may have a particle diameter of 15 to 45 μm, for example, 15 μm, 20 μm, 30 μm, 35 μm, 45 μm, etc. Thus, the compactness of the coating formed by the antioxidant alloy material can be further improved.
According to an embodiment of the present invention, the above-mentioned oxidation-resistant underlayer is formed by a kerosene fuel supersonic flame spraying (HVOF) process, the process parameters of which include: the flow rate of kerosene is 20-25L/h (such as 20L/h, 22L/h, 24L/h, 25L/h, etc.), the flow rate of oxygen is 1800-1900 slm (such as 1800slm, 1850slm, 1900slm, etc.), the powder feeding rate is 60-70 g/min (such as 60g/min, 65g/min, 70g/min, etc.), the scanning speed of a spray gun is 900-1100 mm/s (such as 900mm/s, 1000mm/s, 1100mm/s, etc.), and the number of spraying passes is 4-8 (such as 4 times, 5 times, 6 times, 8 times, etc.). The antioxidation bottom layer formed by adopting the condition spraying has high density and porosity not higher than 0.5 percent.
S300: forming a metal top layer
In the step, a metal pore-forming agent is mixed with a top layer alloy material, and the obtained mixed material is sprayed on at least part of the surface of the oxidation resistant bottom layer far away from the outer wall of the bottom head matrix to form a metal top layer. According to the embodiment of the invention, the metal pore-forming agent and the alloy material can be provided in the form of powder and formed on at least part of the surface of the oxidation-resistant bottom layer by a cold spraying or thermal spraying (preferably cold spraying) method, and the cold spraying or thermal spraying method is suitable for preparing the metal top layer in a large area and has strong operability.
The specific kind of the metal pore former is not particularly limited according to the embodiment of the present invention, and a corrosion-prone metal pore-forming material commonly used in the art, such as pure aluminum, aluminum alloy, pure magnesium, magnesium alloy, etc., may be used. The average particle diameter of the metal pore-forming agent may be 30 to 60. Mu.m, for example, 30. Mu.m, 35. Mu.m, 50. Mu.m, 60. Mu.m, etc. Thus, a porous metal top layer of suitable porosity can be obtained by removing the metal pore former after the metal top layer has been formed.
According to an embodiment of the invention, the above-mentioned top layer alloy material has an average particle size of 30 to 50 μm, for example 30 μm, 35 μm, 40 μm, 50 μm, etc. Therefore, the mixing effect between the top layer alloy material and the metal pore-forming agent can be further improved, and the porous metal top layer with proper porosity is further facilitated to be obtained.
According to the embodiment of the invention, the mass ratio of the metal pore-forming agent to the top layer alloy material is (3-5) (5-7). Specifically, the mass parts of the metal pore-forming agent can be 3, 4, 5 and the like, and the weight parts of the top layer alloy material can be 5, 6, 7 and the like. Thereby, it may be further advantageous to obtain a porous metal top layer of suitable porosity.
According to an embodiment of the present invention, the metal top layer may be formed by a cold spray process, and the process parameters of the cold spray process include: the gas temperature is 450-550 ℃ (such as 450 ℃, 500 ℃, 550 ℃, and the like), the main gas pressure is 3.0-4.0 MPa (such as 3.0MPa, 3.5MPa, 4.0MPa, and the like), the powder feeding speed is 45-55 g/min (such as 45g/min, 50g/min, 55g/min, and the like), the moving speed of the spray gun is 150-250 mm/s (such as 150mm/s, 200mm/s, 250mm/s, and the like), and the spraying distance is 15-25 mm (such as 15mm, 20mm, 25mm, and the like). The metal top layer formed by adopting the spraying under the condition has proper porosity, is favorable for escaping water vapor generated in use, strengthens boiling heat exchange of the outer wall surface of the lower end enclosure of the pressure vessel and improves critical heat flow density.
S400: removal of metal pore formers
In the step, the metal pore-forming agent in the metal top layer is removed to form a porous metal top layer, and a nuclear reactor pressure vessel bottom head product is obtained.
According to an embodiment of the invention, a porous metal top layer may be obtained by bringing an etching medium into contact with the metal top layer in order to remove the metal pore former.
The specific type of the etching medium is not particularly limited as long as the metal pore-forming agent in the metal top layer can be removed without affecting other materials, and for example, an alkaline solution or an acidic solution can be used. According to a specific example of the present invention, the alkaline solution may be, for example, an aqueous NaOH solution of 1 to 5mol/L or the like, and the acidic solution may be, for example, hydrochloric acid, acetic acid or the like.
According to an embodiment of the present invention, the above-mentioned contacting may be performed at 25 to 35℃for 45 to 75 minutes. Specifically, the contact temperature may be 25℃and 30℃and 35℃and the contact time may be 45min, 60min, 75min, etc. Therefore, the metal pore-forming agent in the metal top layer can be effectively removed, and the porous metal top layer is obtained. In addition, electrochemical acceleration (i.e. applying voltage by taking the metal top layer as the anode) can be assisted in the contact process so as to accelerate the speed of removing the metal pore-forming agent.
In addition, it should be noted that all the features and advantages described above for the "nuclear reactor pressure vessel bottom head" are equally applicable to the above-mentioned "method for preparing a nuclear reactor pressure vessel bottom head", and will not be described in detail herein.
In addition, the invention also provides a method for forming the antioxidation bottom layer and the porous metal top layer on the surface of the metal base material. The metal substrate, the oxidation-resistant bottom layer, the porous metal top layer and the forming method thereof are as described above, and are not described in detail herein.
The invention will now be described with reference to specific examples, which are intended to be illustrative only and not limiting in any way.
Example 1
The method comprises the steps of adopting an SA508 steel as a base material of a bottom head matrix of a nuclear reactor pressure vessel which is just manufactured, firstly adopting a sand blasting method to roughen the surface of the SA508 steel base material, and then adopting compressed air to clean the surface of the base material.
The NiCoCrAlY powder with the grain diameter of 15-45 mu m is used as a bottom coating material, and a kerosene fuel supersonic flame spraying (HVOF) technology is adopted to prepare a high-density antioxidation bottom layer on the SA508 steel surface. The specific process parameters are as follows: the flow rate of kerosene is 22.4L/h, the flow rate of oxygen is 1831slm, the powder feeding rate is 65g/min, the scanning speed of a spray gun is 1000mm/s, and the spraying times are 6 times. The porosity of the obtained coating was only 0.5% and the thickness was 120. Mu.m.
Pure aluminum powder with the grain diameter of 30-60 mu m is used as pore-forming agent powder, and 304 stainless steel powder with the grain diameter of 30-50 mu m is used as top coating material. And fully and mechanically mixing the two powders according to the volume ratio of 4:6, and preparing the metal top layer by adopting cold spraying by taking the mixed powder as a spraying raw material. The specific process parameters are as follows: the gas temperature is 500 ℃, the main gas pressure is 3.5MPa, the powder feeding speed is 50g/min, the moving speed of the spray gun is 200mm/s, and the spraying distance is 20mm. The deposition yields a dual component top coating of pure aluminum and 304 stainless steel having a thickness of about 300 microns.
And (3) taking NaOH aqueous solution with the concentration of 3mol/L as a corrosion medium, and removing the pore-forming aluminum particles in the double-component top-layer coating under the parameter condition that the temperature is 30 ℃ and the time is 60 min. Finally, a composite coating with a double-layer structure is obtained, wherein the porosity of the porous metal top layer is 38%, the porosity of the NICoCrAlY bottom layer is only 0.5% (shown in figure 2), and the pore size is about 10-35 mu m (shown in figure 3). The bond strength of the coating was tested according to ASTM C633 standard and the test results indicated that the bond strength of the coating reached 35MPa. The related thermal test results show that the coating can improve the CHF of the surface of the substrate by more than 50 percent.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (11)
1. A nuclear reactor pressure vessel bottom head, comprising:
a lower end socket substrate;
the oxidation resistant bottom layer is formed on at least part of the surface of the outer wall of the lower head base body; the antioxidation bottom layer is formed by an antioxidation alloy material; the thickness of the antioxidation bottom layer is 80-150 mu m; the antioxidation bottom layer is formed by kerosene fuel supersonic flame spraying treatment;
and the porous metal top layer is formed on at least part of the surface of the oxidation resistant bottom layer, which is far away from the outer wall of the lower head base body.
2. The nuclear reactor pressure vessel bottom head of claim 1, wherein the bottom head substrate is formed from at least one selected from the group consisting of SA508 steel and SA533 steel.
3. The nuclear reactor pressure vessel bottom head of claim 1, wherein the oxidation resistant alloy material comprises at least one selected from the group consisting of FeCr-based stainless steel materials, niCr-based alloys, coNiCr-based alloys.
4. The nuclear reactor pressure vessel bottom head of claim 1, wherein the porous metal top layer is formed from at least one selected from the group consisting of 304 stainless steel, 310 stainless steel, 316 stainless steel.
5. The nuclear reactor pressure vessel bottom head of claim 1, wherein the porous metal top layer has a thickness of 250-350 μm.
6. A method of making a nuclear reactor pressure vessel bottom head of any one of claims 1-5, comprising:
(1) Pretreating the outer wall of the lower end socket substrate;
(2) Spraying an antioxidant alloy material on at least part of the surface of the outer wall of the lower head matrix to form an antioxidant bottom layer;
(3) Mixing a metal pore-forming agent with a top layer alloy material, and spraying at least part of the surface of the antioxidation bottom layer, which is far away from the outer wall of the bottom head substrate, with the obtained mixed material to form a metal top layer;
(4) And removing the metal pore-forming agent in the metal top layer to form a porous metal top layer, so as to obtain the nuclear reactor pressure vessel lower head.
7. The method of claim 6, wherein the oxidation resistant underlayer is formed by a kerosene fuel supersonic flame spraying process, process parameters of the kerosene fuel supersonic flame spraying process comprising: the flow rate of kerosene is 20-25L/h, the flow rate of oxygen is 1800-1900 slm, the powder feeding rate is 60-70 g/min, the scanning speed of a spray gun is 900-1100 mm/s, and the spraying times are 4-8 times.
8. The method of claim 6, wherein the mass ratio of the metal pore former to the top layer alloy material is (3-5): (5-7);
and/or the average grain diameter of the antioxidant alloy material is 15-45 mu m;
and/or the top layer alloy material has an average particle size of 30-50 μm;
and/or the metal pore former comprises at least one selected from aluminum, aluminum alloy, magnesium, and magnesium alloy;
and/or the average particle diameter of the metal pore-forming agent is 30-60 μm.
9. The method of claim 6, wherein the metallic top layer is formed by a cold spray process, and wherein the process parameters of the cold spray process include: the gas temperature is 450-550 ℃, the main gas pressure is 3.0-4.0 MPa, the powder feeding speed is 45-55 g/min, the moving speed of the spray gun is 150-250 mm/s, and the spraying distance is 15-25 mm.
10. The method of claim 6, wherein an etching medium is contacted with the metal top layer to remove the metal pore former.
11. The method of claim 10, wherein the etching medium is at least one selected from the group consisting of aqueous sodium hydroxide, hydrochloric acid, and acetic acid;
and/or, the contacting is carried out at 25-35 ℃ for 45-75 min.
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