CN113881995B - Micro-arc oxidation method for interior of cold plate air duct - Google Patents

Micro-arc oxidation method for interior of cold plate air duct Download PDF

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CN113881995B
CN113881995B CN202111281577.0A CN202111281577A CN113881995B CN 113881995 B CN113881995 B CN 113881995B CN 202111281577 A CN202111281577 A CN 202111281577A CN 113881995 B CN113881995 B CN 113881995B
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micro
arc oxidation
cold plate
plate
sliding block
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CN113881995A (en
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方良超
陈奇海
王国超
殷忠义
侯江涛
薛伟锋
杨毅
冯立
王楠
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CETC 38 Research Institute
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/16—Pretreatment, e.g. desmutting
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/18—After-treatment, e.g. pore-sealing
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)

Abstract

The invention discloses a method for micro-arc oxidation inside a cold plate air duct, which relates to the technical field of cold plate surface engineering and comprises the following steps: (1) Cleaning a cold plate to remove oil, and then spraying strippable paint on a non-micro-arc oxidation area; (2) placing the cold plate on a micro-arc oxidation device; and (3) adjusting power supply parameters to perform micro-arc oxidation. The invention has the beneficial effects that: by adopting the micro-arc oxidation tool, the problem of ultra-narrow gap power line shielding is solved, the high uniformity of electric field distribution in the ultra-narrow gap is effectively ensured, the quality uniformity of a micro-arc oxidation film layer can be improved, and the like, so that the micro-arc oxidation quality of a product is ensured to meet application requirements. The micro-arc oxidation film layer prepared by the method has the acid salt spray resistance of at least 192h, and the salt spray corrosion resistance of the micro-arc oxidation film layer is far higher than that of a common micro-arc oxidation film layer for 96 h.

Description

Micro-arc oxidation method for interior of cold plate air duct
Technical Field
The invention relates to the technical field of cold plate surface engineering, in particular to a method for micro-arc oxidation of the interior of a cold plate air duct.
Background
At present, the electronic equipment is used in high-temperature, high-humidity, high-salt, high-mildew and other high-corrosion environments for a long time and faces serious material corrosion problems, and the cold plate is used as a key structural member, so that the corrosion prevention problem of a key air cooling protection area becomes one of bottlenecks which restrict long-term high-reliability use of the product. Compared with the traditional anodic oxide film, the micro-arc oxide film has higher hardness, good performances of corrosion resistance, wear resistance, thermal shock resistance and the like, has better environmental adaptability in severe environment, and is gradually applied to the surfaces of metals such as aluminum alloy and the like. For example, patent publication No. CN101503812A discloses a micro-arc oxidation method, which can perform micro-arc oxidation treatment on a larger part. However, the micro-arc oxidation film of the common part is basically positioned on the outer surface of the common part, the surface area is small, a special tool is not needed in the oxidation process, and the micro-arc oxidation film meeting the requirements can be prepared by a single power supply excitation mode.
In order to ensure the reliable operation of the inner surface of the heat dissipation channel in a strong salt spray environment, the cold plate air channel is required to be provided with a micro-arc oxidation film, so that the corresponding environmental corrosion resistance requirement and high reliability can be met. The area of the cold plate needing micro-arc oxidation treatment has the following characteristics: firstly, the total processing area is large, and the sum of the areas of a plurality of air cooling channels needing micro-arc oxidation treatment exceeds 1m 2 At the moment, the heat generated by the micro-arc oxidation area of the part is large, the distribution of the power line is not uniform, the control on the density of the micro-arc oxidation film layer is extremely unfavorable, and the edge position of the part is easy to ablate. Secondly, the structure needing micro-arc oxidation treatment is a typical ultra-narrow gap, the slit width of the channel is less than 10mm, the distribution of the power lines of micro-arc oxidation in the air duct is fundamentally different from that in a normal state, and the quality of the ceramic coating is greatly influenced along with the problem of uneven distribution of the power lines caused by the linear relation of the distribution of the ultra-narrow gap and the micro-distance electric field in the micro-plasma discharge process.
Disclosure of Invention
The invention aims to solve the technical problems that when the cold plate needs to be subjected to micro-arc oxidation treatment, the gap in the air duct is ultra-narrow, the treatment area is large, the quality of a micro-arc oxidation film is easily influenced, and the invention provides the method suitable for micro-arc oxidation in the air duct of the cold plate.
The invention solves the technical problems through the following technical means:
a method for micro-arc oxidation inside a cold plate air duct comprises the following steps:
(1) Cleaning a cold plate to remove oil, and spraying strippable paint on a non-micro-arc oxidation area;
(2) Placing a cold plate on a micro-arc oxidation tool for micro-arc oxidation, wherein the micro-arc oxidation tool comprises an electrolytic cell, a power supply and an auxiliary cathode; the cold plate is immersed in an electrolytic cell filled with electrolyte, the auxiliary cathode penetrates through the air duct of the cold plate, a gap is formed between the periphery of the auxiliary cathode and the side wall of the air duct, the anode of the power supply is electrically connected with the cold plate, and the cathode of the power supply is electrically connected with the auxiliary cathode;
(3) Adjusting power supply parameters: the first stage is as follows: forward triangular wave, voltage 300-500V, frequency 50-100HZ, oxidation time 1-2min; and a second stage: (a) Positive pulse, voltage 300V-500V, frequency 200-500HZ, oxidation time 20-40min, micro-arc oxidation solution temperature 15-25 deg.C; (b) Negative pulse with voltage of 120V-140V, frequency of 100-300HZ, oxidation time of 10-20min and micro-arc oxidation solution temperature of 15-40 ℃;
(4) And (3) after the micro-arc oxidation is finished, removing the strippable paint in the step (2), and cleaning the oxidized cold plate.
Has the advantages that: the invention aims at the ultra-narrow gap configuration characteristic of a cold plate air duct, adopts bipolar multi-wave superposition pulse control, and comprises two processes, in particular to a mixed control mode combining a triangular wave mode at the initial stage of micro plasma discharge and a pulse mode at the second stage.
In the first stage of micro plasma discharge, in a single period, because the triangular wave voltage rises along the parabolic rule, the rising time domain is far higher than the pulse voltage application time domain, and the amplitude voltage is prevented from being instantaneously applied to the solution resistor, so that the impact of the main peak current is effectively relieved. In addition, the loose porous ceramic coating prepared at the initial stage of the surface of the cold plate air channel can introduce compressive stress to offset (or partially offset) tensile stress generated in the micro plasma discharge preparation process of the subsequent coating.
In the second stage of micro-plasma discharge, based on the positive and negative pulse synergistic effect, the plasma eruption in a local area is inhibited, the high temperature and high pressure in the holes of the initial and regrown ceramic coatings are ensured, and the dielectric constant of the electrolyte medium is greatly reduced, so that in a more compact micro-area, the pulse voltage response can be accelerated, the breakdown discharge in the plasma holes is easily formed, and the densification is realized.
By adopting the micro-arc oxidation tool, the problem of ultra-narrow gap power line shielding is solved, the high uniformity of electric field distribution in the ultra-narrow gap is effectively ensured, the quality uniformity of a micro-arc oxidation film layer can be improved, and the like, so that the micro-arc oxidation quality of a product is ensured to meet application requirements.
The micro-arc oxidation film layer prepared by the method has the acid salt spray resistance of at least 192h, and the salt spray corrosion resistance of the micro-arc oxidation film layer is far higher than that of a common micro-arc oxidation film layer for 96 h.
Preferably, the micro-arc oxidation tool further comprises an auxiliary device, wherein the auxiliary device is respectively connected with two ends of the auxiliary cathode and used for fixing the auxiliary cathode, so that gaps are reserved between the periphery of the auxiliary cathode and the side wall of the narrow channel.
Has the advantages that: the auxiliary device is arranged to fix the auxiliary cathode, so that the auxiliary cathode is not in contact with the inner wall of the cold plate air duct, and ablation is avoided in the cold plate maintenance and oxidation process.
Preferably, the width of the gap is 1-5mm.
Preferably, the width of the gap is 1-3mm.
Preferably, the cold plate material is an aluminum alloy.
Preferably, the micro-arc oxidation tool is made of stainless steel.
Preferably, the micro-arc oxidation tool further comprises a bottom plate and a fixing plate, wherein fixing columns are arranged between the bottom plate and the fixing plate, and a space for pressing a cold plate is arranged between the top wall of the bottom plate and the bottom wall of the fixing plate.
Preferably, the fixing plate comprises a first fixing plate and a second fixing plate, and the first fixing plate and the second fixing plate are oppositely arranged.
Preferably, the auxiliary device comprises a first auxiliary device, the first auxiliary device comprises a first positioning plate and a first sliding block, a sliding groove is formed in the first positioning plate along the axial direction of the first positioning plate, the first sliding block is connected with the first positioning plate in a sliding mode through the sliding groove, and one end of the auxiliary cathode is detachably connected with the first sliding block;
the first sliding block is provided with a first threaded hole, a first positioning column is arranged in the first threaded hole and used for fixing the first sliding block on the sliding groove.
Preferably, a first connecting plate is arranged at the end part, close to the auxiliary cathode, of the first sliding block, one end of the first connecting plate is connected with the first sliding block, and the other end of the first connecting plate is detachably connected with the end part of the auxiliary cathode.
Preferably, the auxiliary device further comprises a second auxiliary device, and the first auxiliary device and the second auxiliary device are respectively positioned at two ends of the auxiliary cathode;
the second auxiliary device comprises a second positioning plate and a second sliding block, a sliding groove is formed in the direction of the axis of the second positioning plate, the second sliding block is connected with the sliding groove in a sliding mode, and one end of the auxiliary cathode is detachably connected with the second sliding block;
and a second threaded hole is formed in the second sliding block, a second positioning column is arranged in the second threaded hole and used for fixing the second sliding block on the sliding groove.
Preferably, a second connecting plate is arranged at the end part, close to the auxiliary cathode, of the second sliding block, one end of the second connecting plate is connected with the second sliding block, and the other end of the second connecting plate is detachably connected with the end part of the auxiliary cathode.
Preferably, the washing in step (1) comprises the steps of: heating 3-5% sodium carbonate solution to 60-80 deg.c and HNO 3 (30% strength) + HF (5% strength) solution and finally washed in hot water.
Preferably, the electrolyte in the step (2) comprises 5-10g/L of sodium silicate, 5-10g/L of sodium tungstate, 1-2g/L of potassium hydroxide, 1-2g/L of potassium fluoride and the balance of deionized water.
Preferably, in the step (4), the oxidized cold plate is put into boiling water for boiling and washing for 5-10min, and is washed and cooled in flowing cooling water.
Preferably, after the micro-arc oxidation is finished, the thickness of the micro-arc oxidation film layer formed in the oxidized cold plate air duct is 20-60 μm.
Preferably, the auxiliary cathode is a stainless steel plate.
The invention has the advantages that: aiming at the ultra-narrow gap configuration characteristic of the cold plate, the invention adopts bipolar multi-wave superposition pulse control, and comprises two processes, in particular to a mixed control mode combining a triangular wave mode at the initial stage of micro plasma discharge and a pulse mode at the second stage.
In the first stage of micro plasma discharge, in a single period, because the triangular wave voltage rises along the parabolic rule, the rising time domain is far higher than the pulse voltage application time domain, and the amplitude voltage is prevented from being instantaneously applied to the solution resistor, so that the impact of the main peak current is effectively relieved. In addition, the loose porous ceramic coating prepared at the initial stage of the surface of the cold plate air channel can introduce compressive stress to offset (or partially offset) tensile stress generated in the micro plasma discharge preparation process of the subsequent coating.
In the second stage of micro-plasma discharge, based on the positive and negative pulse synergistic effect, the plasma eruption in a local area is inhibited, the high temperature and high pressure in the holes of the initial and regrown ceramic coatings are ensured, and the dielectric constant of the electrolyte medium is greatly reduced, so that in a more compact micro-area, the pulse voltage response can be accelerated, the breakdown discharge in the plasma holes is easily formed, and the densification is realized.
By adopting the micro-arc oxidation tool, the problem of ultra-narrow gap power line shielding is solved, the high uniformity of electric field distribution in the ultra-narrow gap is effectively ensured, the quality uniformity of a micro-arc oxidation film layer can be improved, and the like, so that the micro-arc oxidation quality of a product is ensured to meet application requirements.
The micro-arc oxidation film layer prepared by the method has the acid salt spray resistance of at least 192h, and the salt spray corrosion resistance of the micro-arc oxidation film layer is far higher than that of a common micro-arc oxidation film layer for 96 h.
Drawings
FIG. 1 is a schematic structural diagram of a micro-arc oxidation tool in embodiment 1 of the present invention;
FIG. 2 is a schematic perspective view of a cold plate, a bottom plate and a fixing plate in the micro-arc oxidation tool according to embodiment 1 of the present invention;
FIG. 3 is a schematic view of the auxiliary device in embodiment 1 of the present invention;
fig. 4 is a schematic structural diagram of a first auxiliary device in embodiment 1 of the present invention;
FIG. 5 is a schematic structural view of a second auxiliary device in embodiment 1 of the present invention;
in the figure: an electrolytic cell 1; a power supply 2; an auxiliary cathode 3; a base plate 4; a fixed plate 5; a fixing column 6; a metal wire 7; an auxiliary device 8; a first positioning plate 81; a first slider 82; a first connecting plate 83; a first positioning post 84; a second positioning plate 85; a second slider 86; a second connecting plate 87; a second positioning post 88; a limiting block 89; a cold plate 9; an air duct 91.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Test materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
The specific techniques or conditions not specified in the examples can be performed according to the techniques or conditions described in the literature in the field or according to the product specification.
Example 1
The micro-arc oxidation tool adopted by the invention is shown in figures 1-5 and comprises an electrolytic cell 1, a power supply 2, an auxiliary cathode 3, a bottom plate 4, a fixing plate 5 and an auxiliary device 8.
As shown in FIG. 1, an electrolytic cell 1 is filled with an electrolyte, and the shape of the electrolytic cell 1 is set according to actual needs. The whole tool and the cold plate 9 are completely immersed in the electrolyte, and the cold plate 9 is made of aluminum alloy but not limited to aluminum alloy.
As shown in fig. 1 and fig. 2, a space for pressing the cold plate 9 is provided between the top wall of the bottom plate 4 and the bottom wall of the fixing plate 5, and in order to fix the bottom plate 4 and the fixing plate 5, a fixing column 6 is provided between the bottom plate 4 and the fixing plate 5, and the fixing column 6 is a bolt or a screw in this embodiment. The top plate and the fixing plate 5 are used for fixing the cold plate 9, when in use, the cold plate 9 is firstly placed on the top wall of the bottom plate 4, then the fixing plate 5 is placed on the top wall of the cold plate 9, then bolts or screws are arranged, and the cold plate 9 is fixed between the bottom plate 4 and the fixing plate 5 through the bolts or screws. The number of the bottom plates 4 is set according to actual needs, and is 1 in the embodiment.
In this embodiment, the auxiliary cathode 3 is a stainless steel plate, the stainless steel plate penetrates through the air duct 91 of the cold plate 9, the size of the stainless steel plate is set according to the width of the air cooling channel of the cold plate 9, the number of the stainless steel plates is set according to the number of the channels of the cold plate 9, and the vertical distance between the periphery of the stainless steel plate and the side wall of the air duct 91 is 1-5mm.
The auxiliary device 8 comprises a first auxiliary device, the first auxiliary device comprises a first positioning plate 81, a first sliding block 82 and a first connecting plate 83, a sliding groove is formed in the first positioning plate 81 along the axis direction of the first positioning plate, the sliding groove (not shown) is a dovetail groove, the first sliding block 82 is in sliding connection with the first positioning plate 81 through the sliding groove, one end of the first connecting plate 83 is fixedly connected with one end of the first sliding block 82 in the prior art, and the other end of the first connecting plate 83 is detachably connected with one end of the stainless steel plate through a screw or a bolt.
As shown in fig. 3 and 4, a first threaded hole is formed in the first sliding block 82, a first positioning column 84 is disposed in the first threaded hole, in this embodiment, the first positioning column 84 is a screw, and when the first sliding block 82 slides to a proper position, the relative position between the first sliding block 82 and the first positioning plate 81 is fixed through the screw. The number of the first sliders 82, the first positioning posts 84, and the first connecting plates 83 is set according to the number of the auxiliary cathodes 3.
The auxiliary device also comprises a second auxiliary device, and the second auxiliary device and the first auxiliary device are respectively positioned at two ends of the auxiliary cathode 3; the second auxiliary device comprises a second positioning plate 85, a second sliding block 86 and a second connecting plate 87, wherein a sliding groove is formed in the second positioning plate 85 along the axis direction of the second positioning plate, the sliding groove is a dovetail groove, the second sliding block 86 is in sliding connection with the second positioning plate 85 through the sliding groove, one end of the second connecting plate 87 is fixedly connected with one end of the second sliding block 86, the fixed connection mode is the prior art, and the other end of the second connecting plate 87 is detachably connected with the other end of the stainless steel plate through a screw or a bolt.
As shown in fig. 3 and 5, a second threaded hole is formed in the second slider 86, a second positioning post 88 is disposed in the second threaded hole, in this embodiment, the second positioning post 88 is a screw, and when the second slider 86 slides to a proper position, the relative position between the second slider 86 and the second positioning plate 85 is fixed by the screw. The number of the second sliding blocks 86, the second positioning columns 88 and the second connecting plates 87 is set according to the number of the auxiliary cathodes 3.
In order to further limit the movement of the cold plate 9, the top wall of the first positioning plate 81 is also fixedly provided with a limit block 89, and the specific position of the limit block 89 is set according to actual needs.
The power supply 2 is a micro-arc oxidation power supply 2, the cathode of the micro-arc oxidation power supply 2 is connected with the auxiliary cathode 3 through a metal wire 7, the anode of the micro-arc oxidation power supply 2 is connected with a conductive part on the cold plate 9 through a conducting wire, wherein the conductive part can be a screw on the cold plate 9.
And the resistance meter is adopted to measure the resistance between the part and the tool, and when the resistance value is M omega level, the auxiliary cathode 3 is not in contact with the inner wall of the air duct 91 of the cold plate 9, so that no ablation is caused in the process of maintaining and oxidizing the cold plate 9. The whole tool and the cold plate 9 are completely immersed in the electrolyte.
The working principle is as follows: when the cold plate fixing device is used, the cold plate 9 is firstly placed on the top wall of the base plate 4, then the fixing plate 5 is placed on the top wall of the cold plate 9, then bolts or screws are installed, and the cold plate 9 is fixed between the base plate 4 and the fixing plate 5 through the bolts or screws.
One end of the auxiliary cathode 3 is fixed on the first connecting plate 83 through a bolt, the position of the first sliding block 82 relative to the first positioning plate 81 is adjusted according to the position of the cold plate 9 air channel 91, the position of the second sliding block 86 relative to the second positioning plate 85 is adjusted, then one end of the auxiliary cathode 3 is inserted into the cold plate 9 air channel 91, a gap is left between the side wall of the auxiliary cathode 3 and the cold plate 9 air channel 91, and then the other end of the auxiliary cathode 3 is fixed through the second connecting plate 87.
And the resistance meter is adopted to measure the resistance between the part and the tool, and when the resistance value is M omega level, the auxiliary cathode 3 is not in contact with the inner wall of the ventilation channel of the part, so that no ablation is caused in the maintenance and oxidation process of the cold plate 9. All parts on the whole tool are made of stainless steel, and the tool can be repeatedly used. The auxiliary cathode 3 and the cold plate 9 are respectively connected to the micro-arc oxidation power supply 2.
Example 2
A certain aluminum alloy cold plate part is provided with 33 sawtooth-shaped grooves with the length of 10mm, the width of 5mm and the depth of 200mm, which belongs to the preparation of a typical large-area ultra-narrow gap micro-arc oxidation film layer, and a uniform and stable oxidation film layer is difficult to prepare by adopting the traditional micro-arc oxidation process. The micro-arc oxidation tool in the embodiment 1 is adopted for micro-arc oxidation, and the method specifically comprises the following steps:
(1) Cleaning of
Heating 3% sodium carbonate solution to 60 deg.C, and adding HNO 3 (30 mass%) + HF (5 mass%) solution, finally washed in hot water and dried in an oven for standby. Carefully checking whether water stains exist on the welding surface of the part, and if so, cleaning the part by using alcohol or acetone.
(2) Local protection
And spraying strippable paint on the non-micro-arc oxidation area, and curing at room temperature.
(3) Preparing an electrolyte
The electrolyte solution comprises the following components: 8g/L of sodium silicate, 7g/L of sodium tungstate, 1/L of potassium hydroxide, 2g/L of potassium fluoride and the balance of deionized water.
(4) The cold plates in example 1 and this example were assembled, and the entire tool and cold plate were completely immersed in the electrolyte.
(5) Adjusting power supply 2 parameters
The first stage is as follows: forward triangular wave, voltage 400V, frequency 80HZ and oxidation time 2min;
and a second stage: (a) Positive pulse, voltage 400V, frequency 500HZ, oxidation time 30min, and micro-arc oxidation solution temperature 20 ℃; (b) Negative pulse, voltage 130V, frequency 150HZ, oxidation time 10min and micro-arc oxidation solution temperature 30 ℃.
(6) Removing strippable paint
Removing the part surface protective paint after micro-arc oxidation
(7) Cleaning of
And putting the oxidized cold plate into boiling water for boiling and washing for 50-10 minutes, flushing in flowing cooling water, and cooling.
Film property detection
(1) And selecting a plurality of sampling points, and detecting the thickness of the micro-arc oxidation film layer by using an eddy current thickness gauge, wherein the thickness of the film layer is within 20-60 mu m.
(2) And (3) adopting an adhesive tape with the peel strength of 2N/cm-4N/cm, tightly adhering the adhesive tape to the middle area of the film layer to ensure that the adhesive tape and the surface of the adhesive film form 90 degrees, slowly (about 5 mm/s) pulling the adhesive tape away from the surface, repeatedly pulling off for three times, and detecting that the film layer does not fall off, which indicates that the bonding force of the film layer is good enough.
(3) The acidic salt spray test was carried out according to GJB150.9A part 11 salt spray test of laboratory environmental test methods for military installations. The salt spray adopts 5 + -1% NaCl solution (ph 3.5 + -0.5), the word cycle period is 48h (24 h continuous spray and 24h drying), the visual inspection is carried out after 192h, the appearance is uniform, and the corrosion phenomena such as pulverization, shedding, pitting corrosion and the like are avoided.
Example 3
This embodiment is different from embodiment 2 in that:
(1) The electrolyte comprises 5g/L of sodium silicate, 5g/L of sodium tungstate, 1g/L of potassium hydroxide, 1g/L of potassium fluoride and the balance of deionized water.
(2) The power supply parameters were as follows: the first stage is as follows: a forward triangular wave. Voltage 320V, frequency 85HZ and oxidation time 1min; and a second stage: (a) Positive pulse, voltage 410V, frequency 220HZ, oxidation time 20min, and micro-arc oxidation solution temperature 18C; (b) Negative pulse, voltage 126V, frequency 160HZ, oxidation time 15min, and micro-arc oxidation solution temperature 20C.
The same cold plate parts as those in example 2 were subjected to differential arc oxidation in an electrolyte ratio by using the differential arc oxidation tool in example 1, and after treatment, the oxide film layer of the cold plate was subjected to an acid salt spray test according to GJB1509A, and after 192 hours, the cold plate was visually inspected, and had a uniform appearance and no corrosion phenomena such as chalking, falling off, pitting, and the like.
Example 4
This embodiment is different from embodiment 2 in that:
(1) The electrolyte comprises 10g/L of sodium silicate, 10g/L of sodium tungstate, 2g/L of potassium hydroxide, 2g/L of potassium fluoride and the balance of deionized water.
(2) The power supply parameters were as follows: the first stage is forward triangular wave. Voltage is 500V, frequency is 50HZ, and oxidation time is 2min; and a second stage: (a) Positive pulse, voltage 500V, frequency 450HZ, oxidation time 38min, and micro-arc oxidation solution temperature 20C; (b) Negative pulse, voltage 132V, frequency 230HZ, oxidation time 20min, micro-arc oxidation solution temperature 235C.
By adopting the micro-arc oxidation tool in the embodiment 1, the same cold plate parts as those in the embodiment 2 are placed in the electrolyte for micro-arc oxidation, after treatment, an acid salt spray test is carried out on an oxide film layer of the cold plate according to GJB150.9A, and after 192h, visual inspection is carried out, so that the appearance is uniform, and the corrosion phenomena such as pulverization, falling, pitting and the like are avoided.
Comparative example 1
The micro-arc oxidation tool in the embodiment 1 is adopted to prepare the electrolyte which is the same as that in the embodiment 2, the adopted cold plate part is the same as that in the embodiment 2, the only difference is that the control is directly realized in a positive and negative pulse mode, the control is not realized in a positive triangular wave mode, and the parameters of the power supply 2 are as follows: (a) Positive pulse, voltage 400V, frequency 500HZ, oxidation time 30min, and micro-arc oxidation solution temperature 20 ℃; (b) Negative pulse, voltage 130V, frequency 150HZ, oxidation time 10min, and micro-arc oxidation solution temperature 30 ℃.
And after micro-arc oxidation, testing the corrosion resistance of the oxide film layer. The acid salt spray test was performed according to GJB150.9A part 11 salt spray test of military hardware laboratory environmental test methods. Salt spray with 5 + -1% NaCl solution (ph 3.5 + -0.5), cycle period of word 48h (24 h continuous spray and 24h dry), after 24h, larger area corrosion was found. The index is much lower than in example 1. The reason is that the phenomenon that amplitude voltage is applied to the solution resistance instantly occurs, the impact of peak current is caused, the local current is hit and is the local point discharge of plasma, and the microstructure of the micro-film layer is further deteriorated.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (9)

1. A method for micro-arc oxidation inside a cold plate air duct is characterized in that: the method comprises the following steps:
(1) Cleaning a cold plate to remove oil, and then spraying strippable paint on a non-micro-arc oxidation area;
(2) Placing a cold plate on a micro-arc oxidation tool for micro-arc oxidation, wherein the micro-arc oxidation tool comprises an electrolytic cell, a power supply and an auxiliary cathode; the cold plate is immersed in an electrolytic cell filled with electrolyte, the auxiliary cathode penetrates through the air duct of the cold plate, a gap is formed between the periphery of the auxiliary cathode and the side wall of the air duct, the anode of the power supply is electrically connected with the cold plate, and the cathode of the power supply is electrically connected with the auxiliary cathode; the micro-arc oxidation tool further comprises auxiliary devices, wherein the auxiliary devices are respectively connected with two ends of the auxiliary cathode and used for fixing the auxiliary cathode, so that gaps are reserved between the periphery of the auxiliary cathode and the side wall of the narrow channel;
(3) Adjusting power supply parameters: the first stage is as follows: forward triangular wave, voltage 300-500V, frequency 50-100HZ, oxidation time 1-2min; and a second stage: (a) Positive pulse, voltage 300V-500V, frequency 200-500HZ, oxidation time 20-40min, micro-arc oxidation solution temperature 15-25 deg.C; (b) Negative pulse with voltage of 120V-140V, frequency of 100-300HZ, oxidation time of 10-20min and micro-arc oxidation solution temperature of 15-40 ℃;
(4) And (3) after the micro-arc oxidation is finished, removing the strippable paint in the step (2), and cleaning the oxidized cold plate.
2. The method of claim 1, wherein the micro arc oxidation inside the cold plate air duct is performed by: the width of the gap is 1-5mm.
3. The method of claim 1, wherein the micro arc oxidation inside the cold plate air duct is performed by: the micro-arc oxidation tool further comprises a bottom plate and a fixing plate, wherein a fixing column is arranged between the bottom plate and the fixing plate, and a space for pressing the cold plate is arranged between the top wall of the bottom plate and the bottom wall of the fixing plate.
4. The method of claim 1, wherein the micro arc oxidation inside the cold plate air duct is performed by: the auxiliary device comprises a first auxiliary device, the first auxiliary device comprises a first positioning plate and a first sliding block, a sliding groove is formed in the axial direction of the first positioning plate, the first sliding block is connected with the first positioning plate in a sliding mode through the sliding groove, and one end of the auxiliary cathode is detachably connected with the first sliding block;
the first sliding block is provided with a first threaded hole, a first positioning column is arranged in the first threaded hole and used for fixing the first sliding block on the sliding groove.
5. The method according to claim 4, wherein the micro arc oxidation inside the cold plate air duct is performed by: the end part of the first sliding block, which is close to the auxiliary cathode, is provided with a first connecting plate, one end of the first connecting plate is connected with the first sliding block, and the other end of the first connecting plate is detachably connected with the end part of the auxiliary cathode.
6. The method according to claim 4, wherein the micro arc oxidation inside the cold plate air duct is performed by: the auxiliary device also comprises a second auxiliary device, and the first auxiliary device and the second auxiliary device are respectively positioned at two ends of the auxiliary cathode;
the second auxiliary device comprises a second positioning plate and a second sliding block, a sliding groove is formed in the direction of the axis of the second positioning plate, the second sliding block is connected with the sliding groove in a sliding mode, and one end of the auxiliary cathode is detachably connected with the second sliding block;
and a second threaded hole is formed in the second sliding block, a second positioning column is arranged in the second threaded hole and used for fixing the second sliding block on the sliding groove.
7. The method of claim 6, wherein the micro arc oxidation inside the cold plate air duct is performed by: the end part of the second sliding block, which is close to the auxiliary cathode, is provided with a second connecting plate, one end of the second connecting plate is connected with the second sliding block, and the other end of the second connecting plate is detachably connected with the end part of the auxiliary cathode.
8. The method of claim 1, wherein the micro arc oxidation inside the cold plate air duct is performed by: the cleaning in the step (1) comprises the following steps: heating 3-5% sodium carbonate solution to 60-80 deg.c and adding HNO in 30 wt% concentration 3 + 5% by mass HF solution and finally rinsing in hot water.
9. The method of claim 1, wherein the micro arc oxidation inside the cold plate air duct is performed by: the electrolyte in the step (2) comprises 5-10g/L of sodium silicate, 5-10g/L of sodium tungstate, 1-2g/L of potassium hydroxide, 1-2g/L of potassium fluoride and the balance of deionized water.
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