CN112647105B - Aluminum alloy surface treatment method - Google Patents
Aluminum alloy surface treatment method Download PDFInfo
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- CN112647105B CN112647105B CN202110058740.0A CN202110058740A CN112647105B CN 112647105 B CN112647105 B CN 112647105B CN 202110058740 A CN202110058740 A CN 202110058740A CN 112647105 B CN112647105 B CN 112647105B
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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
- C25D11/18—After-treatment, e.g. pore-sealing
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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
- C25D11/026—Anodisation with spark discharge
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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
- C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
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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
- C25D11/18—After-treatment, e.g. pore-sealing
- C25D11/24—Chemical after-treatment
- C25D11/246—Chemical after-treatment for sealing layers
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Abstract
The invention provides a hole sealing treatment method for a micro-arc oxidation film of an aluminum alloy, which can effectively seal micropores on the surface of the micro-arc oxidation film, effectively reduce the porosity and roughness of the micro-arc oxidation film by filling alumina, obviously improve the wear resistance and corrosion resistance of the micro-arc oxidation aluminum material, widen the application range of the micro-arc oxidation aluminum material and meet the market demand.
Description
Technical Field
The invention belongs to the technical field of surface treatment of aluminum or aluminum alloy materials, relates to a hole sealing treatment method, and particularly relates to a hole sealing method for an aluminum alloy micro-arc oxidation film.
Technical Field
The micro-arc oxidation technology is a new technology developed on the basis of the hard anodic oxidation technology, and can directly form a ceramic membrane with a series of excellent performances such as high corrosion resistance, high wear resistance, high insulation, thermal shock resistance and the like on the surface of metals such as aluminum, magnesium, titanium, zirconium, niobium and the like in situ growth. The method is widely applied to the industries of aviation, ships, textile, automobiles and the like. But the ceramic film formed on the surface is melted under the action of the electric arc in the micro-arc oxidation process, and a large number of micron-sized micropores are formed under the combined action of gas formed on the surface of the ceramic film. The micropores exist in a large amount in the ceramic membrane, and part of the micropores are connected with the metal matrix, so that liquid can easily pass through the micropores to reach the metal matrix, metal corrosion is caused, and the oxide membrane is cracked and falls off seriously, thereby affecting the performance of the micro-arc oxide membrane. Therefore, the micro-arc oxide film must be subjected to sealing treatment.
At present, the hole sealing method of the micro-arc oxide film is rarely researched, such as sealing holes by adopting methods of sealing holes by boiling water, spraying and curing resin, sealing holes or sealing holes by a sealant of an anodic oxide film. The micro-arc oxidation film has larger aperture, and partial holes penetrate through the whole oxidation film, so that the boiling water hole sealing is difficult to realize the effective hole sealing of the micro-arc oxidation film; the investment of resin spraying, curing and hole sealing equipment is more, and the cost is higher; the anodic oxide film hole sealing agent has more types, corresponding micro-arc oxide film hole sealing tests are not carried out, and the micro-arc oxide film hole sealing quality is seriously influenced.
For example, in the southwest petroleum university of CN201210357957, a normal-temperature micro-arc oxide film hole sealing method adopts a solution prepared from sodium silicate, nickel salt, a solvent and an accelerator as a hole sealing agent, the hole sealing agent is kept stand for at least 2 hours, then the micro-arc oxide film is sealed by soaking at normal temperature, and the hole sealing agent forms an adsorption crystal filler in micropores on the surface of the micro-arc oxide film after hole sealing, so that the hole sealing purpose is achieved. The solvent is deionized water, and the ratio of sodium silicate, nickel salt and accelerant is as follows: 5-15g/L of sodium silicate, 2-8g/L of nickel salt and 0.1-2g/L of accelerator. The sodium silicate is sodium silicate pentahydrate or sodium silicate nonahydrate, the nickel salt is nickel fluoride, nickel acetate or a mixture thereof, and the accelerator is boric acid, thiourea, potassium fluorozirconate or a mixture thereof. The hole sealing agent solution can be operated at normal temperature without heating, the hole sealing effect is good, the operation is simple and easy, the hardness of the ceramic membrane is not influenced, and the corrosion resistance of the ceramic membrane can be improved.
For example, CN 201811114851A method for modifying the surface of an aluminum alloy profile by micro-arc oxidation and a surface-modified aluminum alloy profile, the method comprises the following steps: a) pretreatment: the aluminum alloy section is subjected to blowing, ash removal, cleaning, oil removal, water washing and drying to complete pretreatment; b) micro-arc oxidation treatment: placing the aluminum alloy section in electrolyte for micro-arc oxidation, wherein the electrolyte comprises the following components: na2SiO3, Na2B4O7, KOH, glycerol, Na2MoO4 and EDTA-2 Na; taking out after micro-arc oxidation is finished; c) and (3) post-treatment: after the aluminum alloy section is cleaned and dried, hole sealing treatment is carried out on the surface of the micro-arc oxidation film layer by adopting polyvinylidene fluoride resin. The surface modified aluminum alloy section bar obtained by the invention is subjected to hole sealing treatment by using polyvinylidene fluoride resin after micro-arc oxidation treatment, has good hole sealing effect, compact and flat surface, excellent wear resistance, corrosion resistance and electrical insulation performance, and greatly improves the comprehensive performance of the aluminum alloy section bar, the existing defects are that the polyvinylidene fluoride resin is physically adsorbed in micro-arc oxidized holes, the adsorption force is limited, the peeling between a base material and the resin is very easy to occur, the micro-arc oxidized ceramic membrane known by the technical personnel in the field has extremely low porosity which is usually not higher than 10%, under the condition of the low porosity, the hole sealing rate of the polyvinylidene fluoride resin to the micro-arc oxidized ceramic membrane is extremely poor, the wear resistance, the corrosion resistance and the electrical insulation performance of the micro-arc oxidized ceramic membrane are excellent, and the polyvinylidene fluoride resin is not just adhered to the surface of the oxidized membrane and has the property of the polyvinylidene fluoride resin, has no direct relation with hole sealing.
As another example, the sealing treatment method of the micro-arc oxidation ceramic membrane disclosed in CNCN201110288402, firstly, uses acetone to remove dirt and oil on the surface of the micro-arc oxidation sample of the aluminum alloy to be sealed, and then uses distilled water with the temperature of 50-60 ℃ to perform ultrasonic vibration cleaning; then, carrying out vacuum infiltration by adopting organic silicon stock solution and alcohol with the mass concentration of more than 95%; finally, the micro-arc oxidation ceramic membrane sealing treatment method is placed in a heat preservation furnace for heat preservation to complete sealing treatment, and can greatly improve the wear resistance and corrosion resistance of the micro-arc oxidation membrane layer, effectively reduce the contamination of the oxidation membrane layer, improve the electrical insulation performance of the oxidation membrane layer and improve the toughness of the membrane layer.
Disclosure of Invention
Based on the problems in the prior art, the invention provides an aluminum alloy surface treatment method, which is hole sealing treatment of an aluminum alloy micro-arc oxidation ceramic membrane, wherein aluminum sol is filled in a pore channel of the micro-arc oxidation membrane, hole sealing is carried out through superheated steam treatment, so that the corrosion resistance and the wear resistance of the micro-arc oxidation membrane are effectively improved, and the surface roughness is reduced through polishing.
The method for processing the surface of the aluminum alloy is hole sealing processing of the aluminum alloy micro-arc oxidation ceramic membrane, and comprises the following processing steps:
(1) pretreating the surface of the aluminum alloy;
(2) taking the aluminum alloy subjected to surface pretreatment as an anode, and carrying out micro-arc oxidation in electrolyte to form a micro-arc oxidation film on the surface of the aluminum alloy;
(3) removing the porous surface layer on the surface of the micro-arc oxidation film by one-time mechanical polishing;
(4) primary heat treatment;
(5) filling alumina sol in vacuum;
(6) secondary heat treatment;
(7) secondary mechanical polishing;
(8) acid washing and water washing.
Further, the aluminum alloy surface pretreatment comprises sand blasting, water washing, alkali washing, water washing, acid washing and water washing.
Further, sand blasting: the quartz sand with the hardness of 385Hv has the grain diameter of 2-3mm and the air pressure of 0.3-0.5 Mpa.
Further, alkali washing: NaOH 40-50g/L, sodium tartrate 2-4g/L, temperature 40-55oC, the time is 3-5 min.
Further, acid washing: HNO 3250-300 g/L at 25-30oC, the time is 3-5 min.
Further, the micro-arc oxidation comprises 1-2g/L of sodium hydroxide, 8-12g/L of sodium silicate, 3-5ml/L of glycerol and 2-4g/L of disodium ethylene diamine tetraacetate, and the current density is 6-10A/dm2The frequency is 450-500Hz, the duty ratio is 30-40%, the positive-negative pulse ratio is 1:1, the time is 20-40min, and the surface roughness of the obtained micro-arc oxidation film is Ra =2-3 microns.
Further, the mechanical polishing is an artificial diamond grinding wheel, the grinding thickness is 5-8 mu m, the grinding speed of the diamond is 14-16m/s, and the grain size of the diamond on the surface of the grinding wheel is 2-5 microns.
Further, the primary heat treatment is used for treating the thermal stress of the micro-arc oxide film, 2oC/min is raised to 300-oAnd C, keeping the temperature for 1-2 hours in an inert atmosphere, and naturally cooling.
Further, the preparation method of the aluminum sol comprises the following steps: weighing 7-8g of pseudo-boehmite, adding the pseudo-boehmite into 120mL of 100-one mL deionized water in batches under the stirring condition, adding 1-2M nitric acid solution, continuously stirring for 3-4 h at 10%-2~10-4Under the condition of a MPa vacuum pump, filling the alumina sol into the pore canal of the micro-arc oxidation film, and then 50-60 percent of the alumina sol is filled into the pore canal of the micro-arc oxidation filmoC, drying and repeatedly filling for 2-4 times.
Further, the secondary heat treatment is high-temperature steam heat treatment, 115-120-oC, overheating the water vapor.
Further, the secondary mechanical polishing is alpha-Al-containing2O3The polishing solution of (a), the alpha-Al2O3The particle size of the polishing solution is 500-800nm, the polishing time is 3-5min, and the polishing thickness is 3-5 μm.
Further, the acid is washed by nitric acid in 15-17vol.%, HF in 1-1.5vol.%, and the temperature is room temperature for 5-10 min.
The preparation process and the principle of the method for sealing the hole of the aluminum alloy micro-arc oxide film are explained as follows:
(A) pretreatment of the aluminum alloy: regardless of the surface treatment process, cleaning the surface is the primary condition to achieve good results. Since the surface of the component sent to the surface treatment workshop usually has various defects of grinding marks, pits, burrs, scratches and the like, has lubricating oil marks or is covered with abrasive materials and some dirt to different degrees, the effective pretreatment can ensure that the micro-arc oxidation film has good corrosion resistance and has good bonding force with the surface of the substrate.
The pretreatment process adopted by the invention comprises sand blasting, water washing, alkali washing, water washing, acid washing and water washing.
Wherein, sand blasting: the quartz sand with the hardness of 385Hv has the particle size of 2-3mm and the air pressure of 0.3-0.5Mpa, is used for preliminarily removing an obvious oxidation film on the surface of a base material, flattening obvious defects of unevenness of a base plate metal part and improving the surface roughness of a workpiece.
Wherein, alkali washing: NaOH 40-50g/L, sodium tartrate 2-4g/L, temperature 40-55oC, time is 3-5min, and the alkali washing has two purposes: (1) degreasing: removal of grease from metal surfaces mainly by saponification: (C17H35COO)3C3H5+3NaOH→3C17H35COONa+C3H5(OH)3(ii) a (2) Removing the oxide film: al (Al)2O3+2NaOH→2NaAlO2+H2O, reaction of sodium hydroxide with aluminum base inevitably occurs during the removal of oxide film, and in order to avoid reaction of aluminum base with hydrogen hydroxide, it is necessary to strictly control the alkali washing time, and NaAlO known to those skilled in the art2Hydrolysis reactions can obviously occur: NaAlO2+2H2O → Al (OH)3+ NaOH, and therefore to avoid hydrolysis, the addition of sodium tartrate or like complexing agent which may be apparently consistent with NaAlO2Hydrolysis reaction of (3).
Wherein, acid washing: HNO3250-300 g/L at a temperature of 25-30oAnd C, for 3-5min, wherein the acid cleaning aims to remove gray substances on the metal surface, the gray substances can be precipitates after hydrolysis of sodium metaaluminate and can also be copper oxide formed by metals such as Cu in the aluminum alloy, and the gray substances must be removed, otherwise, the influence on subsequent micro-arc oxidation is large, so that the acid cleaning is an indispensable treatment step.
(B) Micro-arc oxidation: in the micro-arc oxidation, because the phenomena of glow discharge, spark discharge and the like can occur on the surface of the oxide film in the implementation process, the micro-arc oxidation is also called as electric spark discharge, so that the phase and the structure of the oxide layer with an amorphous structure are changed and are accompanied by alpha-Al2O3And gamma Al2O3The typical micro-arc oxidation film structure generally comprises a substrate, a transition layer, a low-density hardness layer and a porous surface layer, wherein the porosity of the porous surface layer on the outermost surface is higher and can usually reach 10-15 percent, and gamma-Al2O3The porous layer has a high porosity and thus a low hardness, usually 400-500Hv, and thus the porous layer does not contribute to the high wear resistance or corrosion resistance of the micro-arc oxide film, and therefore needs to be polished and removed, the thickness of the porous layer is about 30 μm, and the micro-arc oxide film contacting the surface layer has a higher porosity and a lower hardness, and thus needs to be polished later.
The second layer is a low-density hardness layer which is a main technical contribution layer of the micro-arc oxidation film and mainly comprises the alpha-Al2O3And a small amount of gamma-Al2O3The thickness of the low-density hardness layer is within the range of 100-300 mu m, the porosity is usually maintained at 2-5%, and the contribution of the low-density hardness layer to the hardness of the micro-arc oxidation film is 1500-2000Hv depending on the electrolysis parameters of the micro-arc oxidation.
The transition layer is closest to the substrate, has a thickness of about 2-5 μm, and is engaged with the substrate, and has a porosity generally higher than that of the low-density hard layer and lower than that of the porous surface layer.
The micro-arc oxidation of the invention comprises 1-2g/L of sodium hydroxide, 8-12g/L of sodium silicate, 3-5ml/L of glycerol, 2-4g/L of disodium ethylene diamine tetraacetate, and the current density6-10A/dm2The frequency is 450-500Hz, the duty ratio is 30-40%, the positive-negative pulse ratio is 1:1, and the time is 20-40 min.
The performance of the micro-arc oxidation film layer is related to the components and the phase structure of the micro-arc oxidation film layer, the components and the phase structure of the film layer are in great relation to the components and the matrix of electrolyte used in the test, wherein 1-2g/L of sodium hydroxide is taken as a basic component, 8-12g/L of sodium silicate is taken as a passivating agent, the passivating agent can promote the formation of a barrier type oxidation film and can more easily passivate the matrix metal, so that the breakdown phenomenon occurs and the micro-arc oxidation starts, wherein glycerol OH-The conductivity of the solution can be improved by the conductive agent, the dispersity of the micro-arc oxidation solution can be improved by the glycerol, the stability of the pH values of the solution and the solution can be improved by the disodium ethylene diamine tetraacetate stabilizer, and the disodium ethylene diamine tetraacetate stabilizer is used for complexing metal ions in the electrolyte.
The current density is 6-10A/dm2: the current density is an important parameter in the micro-arc oxidation process, and has great influence on the structure and the appearance of the micro-arc oxidation film layer. For example, the current density seriously affects the increase of the thickness of the micro-arc oxidation film layer, the thickening speed of the oxidation film and the dense layer thereof is increased with the increase of the current density, but the proportion of the dense layer is gradually reduced, and in the constant current mode, when the current density is higher, the spark discharge intensity is gradually increased but the number of sparks is gradually reduced, so the formed film layer is relatively rough.
The frequency is 450-500 Hz: the low frequency represents that the pulse energy lasts longer in a single period, the time of spark discharge is increased, the growth speed of the film is higher, for example, the higher the frequency is, the larger the number of micropores of the film is, the more uniform the distribution is, and the pore diameter is reduced along with the increase of the frequency.
Duty cycle 30-40%: the increase of the duty ratio can improve the spark discharge energy, so that the porosity of the film layer is improved, and the improvement of the porosity can reduce the strength of the anodic oxide film, for example, the micro-arc sparks are more in quantity under the low duty ratio, and the generated film layer has smaller micropores; at high duty cycles the spark discharge becomes intense and the film is relatively rough.
The time is 20-40 min: the micro-arc oxidation time mainly influences the roughness and the thickness of the micro-arc oxidation film, and the micro-arc oxidation film has long time, thick thickness and obviously improved roughness in a certain time range.
(C) Removing the porous surface layer on the surface of the micro-arc oxidation film by one-time mechanical polishing: the artificial diamond grinding wheel is 5-8 mu m in grinding and polishing thickness, the grinding speed of the diamond is 14-16m/s, and the particle size of the diamond on the surface of the grinding wheel is 2-5 mu m, as mentioned above, the hardness of the porous layer on the surface layer of the micro-arc oxidation film is low, the porosity is high, and therefore the micro-arc oxidation film needs to be ground and removed, so that the hardness and the wear resistance of the micro-arc oxidation film are further improved Corrosion resistance, and reduced surface roughness, and therefore, a polishing process is required, which removes the porous layer to a thickness of 2 to 5 μm.
(D) Primary heat treatment: 2oC/min is raised to 300-oC, keeping the temperature for 1-2 hours in an inert atmosphere, and naturally cooling, wherein the main purpose of the heat treatment is to remove thermal stress, and a person skilled in the art knows that the surface layer of the micro-arc oxidation film consists of large particles with the diameter of dozens of micrometers and a large number of small particles with the diameter of several micrometers, a discharge air hole with the size of several micrometers is remained in each large particle, the micro-arc oxidation film is similar to the shape of a crater, liquid gasification can occur near the crater pore channel in the micro-arc oxidation process, a high-temperature area is formed, the micro-arc oxidation film can have obvious thermal stress, the polishing temperature is higher in the polishing process, the bonding force between the anodic oxidation film and a base material can be reduced due to the local heat, and the stress needs to be removed through heat treatment.
(E) And (3) vacuum filling of the aluminum sol, wherein the preparation method of the aluminum sol comprises the following steps: weighing 7-8g of pseudo-boehmite, adding the pseudo-boehmite into 120mL of 100-one mL deionized water in batches under the stirring condition, adding 1-2M nitric acid solution, continuously stirring for 3-4 h at 10%-2~10- 4Under the condition of a MPa vacuum pump, filling the alumina sol into the pore canal of the micro-arc oxidation film, and then 50-60 percent of the alumina sol is filled into the pore canal of the micro-arc oxidation filmoC, drying and repeatedly filling for 2-4 times. Under the auxiliary condition of vacuum suction, the alumina sol enters a pore channel of the micro-arc oxidation film, and then is dehydrated through drying and heating treatment to form amorphous alumina, wherein the amorphous alumina is mainly used as a main source for subsequent filling and sealing holes and a key component of the invention.
(F) Secondary heat treatment: high temperature steam heat treatment, 115-120-oC, overheating the water vapor. As described above, the pore channels of the micro-arc oxidation film are filled with amorphous alumina, the amorphous oxidation is changed from alumina sol to alumina in the drying process and can obviously shrink, similar to the way of filling organic silicon in the micro-arc oxidation pore channels in CNCN201110288402, once drying occurs, the silicon oxide and the micro-arc oxidation pore channels are inevitably separated, and the hole sealing effect can not be achieved actually2O3H2O (AlOOH), the reaction of which is: al (Al)2O3+nH2O→Al2O3+nH2O, similar to the sealing of an anodic oxide film, there is a technical problem in that, since the micro-arc oxide film is directly sealed by steam without using a sealing means similar to the micro-arc oxide film, it is required to explain that the anodic oxide film has uniform pores and very small pore diameter, generally not higher than 100nm, and alumina is synthesized with hydrated alumina of boehmite type by simple hydrothermal process due to density of hydrated alumina (3014 kg/m)3) Specific alumina (3420 kg/m)3) The volume of the micro-arc oxidation film is increased by about 30 percent, and the pores of the oxidation film can be completely blocked, but the pore diameter of the micro-arc oxidized alumina pore canal is micron-sized, and the hydrothermal hole sealing can not be realized only by the alumina of the oxidation film, so that the invention needs to fill amorphous alumina in the pore canal of the micro-arc oxidation film, and then the hole sealing of the micro-arc oxidation film is realized through the expansion effect.
In addition, the method can be used for producing a composite materialAl, known to the person skilled in the art2O3+nH2O→Al2O3+nH2In the O hole sealing process, 105 is adoptedoWhen C steam is used for thermal hole sealing, n is approximately equal to 1, the general temperature is high, the smaller the n value is, the lower the hydration degree is, and the stronger the hardness and the corrosion resistance are, the superheated steam adopted by the invention is 115-one-wall-120oC。
(G) Secondary mechanical polishing: as described above, sealing is effective by the filling-heat treatment, but during the filling process, part of the alumina sol adheres to the micro-arc oxide film surface instead of filling the pores, and after the subsequent treatment, the surface-adhered alumina does not have sealing effect, but forms an oxide layer having very poor adhesion to the micro-arc oxide film, which must be removed from each other, and is secondarily mechanically polished to contain α -Al2O3The polishing solution of (a), the alpha-Al2O3The grain size of the polishing solution is 500-800nm, the polishing time is 3-5min, the polishing thickness is 3-5 μm, the roughness of the metal surface is improved, and the market hand feeling requirement is met, in addition, the small-grain alumina is adopted, on the premise that impurities are not introduced on the surface of the micro-arc oxidation film, the small-grain alumina which is partially crushed in the polishing solution is expected to be further plugged into the pore canal or the gap with the porosity of below 1 percent.
(H) Acid washing and water washing: nitric acid 15-17vol.%, HF 1-1.5vol.%, room temperature, 5-10min, etching to remove particulate alumina that is not removed by partial polishing.
The scheme of the invention has the following beneficial effects:
(1) the micro-arc oxidation film is treated by filling-expanding hole sealing, so that the surface density of the micro-arc oxidation film is effectively improved, and the surface micro-arc oxidation porosity is reduced.
(2) By adopting the method for treating the micro-arc oxidation film, the hardness and the corrosion resistance of the micro-arc oxidation film are effectively improved, and the roughness is reduced.
Detailed Description
Example 1
The method is hole sealing treatment of the aluminum alloy micro-arc oxidation ceramic membrane, and comprises the following treatment steps:
(1) and (4) pretreating the surface of the aluminum alloy.
Sand blasting: the quartz sand with the hardness of 385Hv has the grain diameter of 2mm, and the air pressure is 0.3 Mpa.
Alkali washing: NaOH 40g/L, sodium tartrate 2g/L, temperature 40oC, time 3 min.
Acid washing: HNO3250g/L, temperature 25oC, time 3 min.
(2) The aluminum alloy subjected to surface pretreatment is used as an anode, and micro-arc oxidation is carried out in electrolyte to form a micro-arc oxidation film on the surface of the aluminum alloy: micro-arc oxidation parameters: 1g/L sodium hydroxide, 8g/L sodium silicate, 3ml/L glycerol, 2g/L disodium ethylene diamine tetraacetate and current density of 6A/dm2The frequency is 450Hz, the duty ratio is 30 percent, the positive-negative pulse ratio is 1:1, and the time is 20 min.
(3) Removing the porous surface layer on the surface of the micro-arc oxidation film by one-time mechanical polishing: the mechanical polishing is an artificial diamond grinding wheel, the grinding speed of the diamond is 14m/s, and the grain diameter of the diamond on the surface of the grinding wheel is 2 microns.
(4) Primary heat treatment: 2oC/min is increased to 300oAnd C, keeping the temperature for 1 hour under the inert atmosphere, and naturally cooling.
(5) Vacuum filling of aluminum sol: weighing 7g of pseudoboehmite, adding into 100mL of deionized water in batches under the stirring condition, adding 1M nitric acid solution, continuously stirring for 3 h, and stirring at 10%-2Under the condition of a MPa vacuum pump, filling the alumina sol into the pore channel of the micro-arc oxidation film, and then 50 percent of the alumina sol is filled into the pore channeloC, drying for 36h, and repeatedly filling for 3 times.
(6) Secondary heat treatment: high temperature steam Heat treatment, 115oC, overheating water vapor for 10 min;
(7) secondary mechanical polishing: secondary mechanical polishing to contain alpha-Al2O3The polishing solution of (a), the alpha-Al2O3The grain diameter of the polishing solution is 500nm, and the polishing time is 3 min;
(8) acid washing, water washing, wherein the acid washing is nitric acid 15vol.%, HF 1vol.%, room temperature and 5 min.
Example 2
The method is hole sealing treatment of the aluminum alloy micro-arc oxidation ceramic membrane, and comprises the following treatment steps:
(1) and (4) pretreating the surface of the aluminum alloy.
Sand blasting: the quartz sand with the hardness of 385Hv has the grain diameter of 2.5mm, and the air pressure is 0.4 Mpa.
Alkali washing: NaOH 45g/L, sodium tartrate 3g/L, temperature 47oC, time 4 min.
Acid washing: HNO 3275 g/L, temperature 27.5oC, time 4 min.
(2) The aluminum alloy subjected to surface pretreatment is used as an anode, and micro-arc oxidation is carried out in electrolyte to form a micro-arc oxidation film on the surface of the aluminum alloy: micro-arc oxidation parameters: 1.5g/L sodium hydroxide, 10g/L sodium silicate, 4ml/L glycerol, 3g/L disodium ethylene diamine tetraacetate and current density of 8A/dm2The frequency is 475Hz, the duty ratio is 35%, the positive-negative pulse ratio is 1:1, and the time is 30 min.
(3) Removing the porous surface layer on the surface of the micro-arc oxidation film by one-time mechanical polishing: the mechanical polishing is an artificial diamond grinding wheel, the grinding speed of the diamond is 15m/s, and the grain diameter of the diamond on the surface of the grinding wheel is 3.5 microns.
(4) Primary heat treatment: 2oC/min is increased to 310oAnd C, keeping the temperature for 1.5h under the inert atmosphere, and naturally cooling.
(5) Vacuum filling of aluminum sol: weighing 7.5g of pseudoboehmite, adding into 110mL of deionized water in batches under the stirring condition, adding 1.5M nitric acid solution, continuously stirring for 3.5h, and stirring at 10%-4Under the condition of a MPa vacuum pump, filling the alumina sol into the pore canal of the micro-arc oxidation film, and then 55 percent of the alumina sol is filled into the pore canal of the micro-arc oxidation filmoC, drying for 42h, and repeatedly filling for 3 times.
(6) Secondary heat treatment: high temperature steam Heat treatment, 120oC, overheating water vapor for 13 min;
(7) secondary mechanical polishing: secondary mechanical polishing to contain alpha-Al2O3The polishing solution of (a), the alpha-Al2O3The grain diameter of the polishing solution is 700nm, and the polishing time is 4 min;
(8) acid washing, water washing, wherein the acid washing is nitric acid 16vol.%, HF 1.25vol.%, and room temperature is 7.5 min.
Example 3
The method is hole sealing treatment of the aluminum alloy micro-arc oxidation ceramic membrane, and comprises the following treatment steps:
(1) and (4) pretreating the surface of the aluminum alloy.
Sand blasting: the quartz sand with the hardness of 385Hv has the grain diameter of 3mm, and the air pressure is 0.5 Mpa.
Alkali washing: NaOH50g/L, sodium tartrate 4g/L, temperature 55oC, time 5 min.
Acid washing: HNO 3300 g/L, temperature 30oC, time 5 min.
(2) The aluminum alloy subjected to surface pretreatment is used as an anode, and micro-arc oxidation is carried out in electrolyte to form a micro-arc oxidation film on the surface of the aluminum alloy: micro-arc oxidation parameters: 2g/L of sodium hydroxide, 12g/L of sodium silicate, 5ml/L of glycerol, 4g/L of disodium ethylene diamine tetraacetate and current density of 10A/dm2The frequency is 500Hz, the duty ratio is 40%, the positive-negative pulse ratio is 1:1, and the time is 40 min.
(3) Removing the porous surface layer on the surface of the micro-arc oxidation film by one-time mechanical polishing: the mechanical polishing is carried out by using an artificial diamond grinding wheel, the grinding speed of the diamond is 16m/s, and the grain diameter of the diamond on the surface of the grinding wheel is 5 microns.
(4) Primary heat treatment: ,2oC/min is increased to 320oAnd C, keeping the temperature for 2 hours in an inert atmosphere, and naturally cooling.
(5) Vacuum filling of aluminum sol: weighing 8g of pseudoboehmite, adding the pseudoboehmite into 120mL of deionized water in batches under the stirring condition, adding 2M nitric acid solution, continuously stirring for 4 h, and stirring at 10%-4Under the condition of a MPa vacuum pump, filling the alumina sol into the pore canal of the micro-arc oxidation film, and then 60 percent of the alumina sol is filled into the pore canal of the micro-arc oxidation filmoC, drying for 48h, and repeatedly filling for 2 times.
(6) Secondary heat treatment: high temperature steam Heat treatment, 120oC, overheating water vapor for 15 min;
(7) secondary mechanical polishing: secondary mechanical polishing to contain alpha-Al2O3The polishing solution of (a), the alpha-Al2O3The grain diameter of the polishing solution is 800nm, and the polishing time is 5 min;
(8) acid washing, water washing, wherein the acid washing is 17vol.% of nitric acid, 1.5vol.% of HF, room temperature and 10 min.
The hardness range of the hole sealing micro-arc oxidation aluminum material obtained by the treatment of the invention is 2250-.
Although the present invention has been described above by way of examples of preferred embodiments, the present invention is not limited to the specific embodiments, and can be modified as appropriate within the scope of the present invention.
Claims (8)
1. The method for processing the surface of the aluminum alloy is hole sealing processing of the aluminum alloy micro-arc oxidation ceramic membrane, and is characterized by comprising the following processing steps:
(1) pretreating the surface of the aluminum alloy;
(2) taking the aluminum alloy subjected to surface pretreatment as an anode, and carrying out micro-arc oxidation in electrolyte to form a micro-arc oxidation film on the surface of the aluminum alloy;
(3) removing the porous surface layer on the surface of the micro-arc oxidation film by one-time mechanical polishing;
(4) primary heat treatment;
(5) vacuum filling of aluminum sol, weighing 7-8g of pseudo-boehmite, adding into 120mL of deionized water of 100-0 mL in batches under the stirring condition, adding 1-2M nitric acid solution, continuously stirring for 3-4 h, and keeping the temperature at 10 DEG-2~10-4Filling the alumina sol into a pore channel of the micro-arc oxidation film under the condition of an MPa vacuum pump, then drying at 50-60 ℃ for 36-48h, and repeatedly filling for 2-4 times;
(6) secondary heat treatment, wherein the secondary heat treatment is high-temperature steam heat treatment, and the superheated steam at the temperature of 115-120 ℃ lasts for 10-15 min;
(7) secondary mechanical polishing;
(8) acid washing and water washing.
2. The method for treating the surface of the aluminum alloy according to claim 1, wherein the aluminum alloy surface pretreatment comprises sand blasting, water washing, alkali washing, water washing, acid washing and water washing.
3. The surface treatment method of an aluminum alloy according to claim 2, wherein the blasting: the quartz sand with the hardness of 385HV has the grain diameter of 2-3mm and the air pressure of 0.3-0.5Mpa;
alkali washing: NaOH 40-50g/L, sodium tartrate 2-4g/L, temperature 40-55 deg.C, time 3-5 min;
acid washing: HNO3250-300g/L, 25-30 ℃ and 3-5 min.
4. The method of claim 1, wherein the micro-arc oxidation comprises 1-2g/L NaOH, 8-12g/L sodium silicate, 3-5ml/L glycerin and 2-4g/L EDTA disodium, and the current density is 6-10A/dm2The frequency is 450-500Hz, the duty ratio is 30-40%, the positive-negative pulse ratio is 1:1, the time is 20-40min, and the surface roughness of the obtained micro-arc oxidation film is Ra =2-3 microns.
5. The surface treatment method of an aluminum alloy according to claim 1, wherein the mechanical polishing is a synthetic diamond wheel, the grinding thickness is 5 to 8 μm, the grinding speed of diamond is 14 to 16m/s, and the grain size of diamond on the surface of the wheel is 2 to 5 μm.
6. The surface treatment method of an aluminum alloy according to claim 1, wherein the primary heat treatment: raising the temperature to 300 ℃ and 320 ℃ at the speed of 2 ℃/min, keeping the temperature for 1-2h under the inert atmosphere, and naturally cooling.
7. The surface treatment method for aluminum alloy according to claim 1, wherein the secondary mechanical polishing is a polishing containing α -Al2O3The polishing solution of (a), the alpha-Al2O3The particle size of the polishing solution is 500-800nm, the polishing time is 3-5min, and the polishing thickness is 3-5 μm.
8. The surface treatment method of an aluminum alloy according to claim 1, wherein the pickling is performed with nitric acid 15 to 17vol.%, HF 1 to 1.5vol.%, room temperature, 5 to 10 min.
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