WO2015147162A1 - アルミニウム部材の表面被覆方法及び表面被覆アルミニウム部材並びに内燃機関用ピストン - Google Patents
アルミニウム部材の表面被覆方法及び表面被覆アルミニウム部材並びに内燃機関用ピストン Download PDFInfo
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- WO2015147162A1 WO2015147162A1 PCT/JP2015/059364 JP2015059364W WO2015147162A1 WO 2015147162 A1 WO2015147162 A1 WO 2015147162A1 JP 2015059364 W JP2015059364 W JP 2015059364W WO 2015147162 A1 WO2015147162 A1 WO 2015147162A1
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- anodic oxide
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- oxide film
- anodized
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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
- C25D11/12—Anodising more than once, e.g. in different baths
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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
- C25D11/024—Anodisation under pulsed or modulated current or potential
-
- 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
- C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
-
- 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
- C25D11/10—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing organic acids
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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
-
- 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
- C25D11/20—Electrolytic after-treatment
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
Definitions
- the present invention relates to a method for coating a surface of an aluminum member, a surface-coated aluminum member, and a piston for an internal combustion engine.
- an aluminum member a member made of aluminum or an aluminum alloy
- a member made of aluminum or an aluminum alloy has been required to have heat insulation.
- an aluminum member when such an aluminum member is used for a part that forms a combustion chamber of an engine of an internal combustion engine or a part of a piston for an internal combustion engine (hereinafter also referred to as a part of the combustion chamber), the thermal efficiency in the combustion chamber
- it is required to improve the heat insulation by forming a film on the member.
- heat insulation is provided in the vicinity of the spark plug by forming an anodized film as a heat shield film on the bottom surface of the cylinder head made of an aluminum member of the combustion chamber, and the heat shield film as the distance from the spark plug increases.
- knocking which is abnormal combustion, is suppressed by gradually reducing the film thickness of (Patent Document 1).
- an anodized film is formed as a thermal barrier film on at least a part of the wall surface made of the aluminum member of the combustion chamber, and the heat insulation performance of at least a part of the thermal barrier film in the region on the intake valve side is determined on the exhaust valve side. It is known to make it higher than the thermal barrier film of the wall surface in the region (Patent Document 2).
- a heat shield is provided in the entire combustion chamber, such as a piston of an internal combustion engine, heat is generally generated in the combustion chamber, making it difficult for heat to escape. In particular, knocking is likely to occur at high loads. In order to suppress such knocking, it is necessary to achieve both heat insulation and soaking so as to make the wall surface temperature uniform quickly.
- an object of the present invention is to provide a surface covering method for an aluminum member, a surface covering aluminum member, and a piston for an internal combustion engine that are provided with both high heat insulation and high temperature uniformity.
- One aspect of the surface-coated aluminum member according to the present invention includes at least a first film on the surface of the aluminum member and a second film having a higher thermal conductivity than the first film on the surface of the first film.
- one aspect of the surface coating method for an aluminum member according to the present invention is a method of forming a second anodized film by applying AC / DC superposition electrolysis to the aluminum member, and applying direct current electrolysis to the aluminum member.
- the first anodic oxide film and the second anodic oxide film are formed on the surface of the second anodic oxide film by using a predetermined film forming method. Forming a film having a higher thermal conductivity than the above.
- an aluminum member surface coating method, a surface-coated aluminum member, and a piston for an internal combustion engine that have both high heat insulation properties and high heat uniformity.
- FIG. 1 is a cross-sectional view schematically showing a surface-coated aluminum member with respect to the surface-coating method and surface-coated aluminum member for an aluminum member according to the present invention.
- FIG. 2 is a configuration diagram schematically showing an anodizing apparatus used for forming a first film for a surface coating method, a surface coated aluminum member, and a piston for an internal combustion engine according to the present invention. is there.
- FIG. 3 is a schematic flowchart for explaining a method of forming the first film and the second film in the method of covering the surface of the aluminum member according to the present invention.
- FIG. 4 is a cross-sectional photograph of a test piece of a test example with respect to the surface covering method of the aluminum member, the surface covering aluminum member, and the piston for the internal combustion engine.
- FIG. 1 is a schematic cross-sectional view showing a surface-coated aluminum member of the present embodiment.
- the surface-coated aluminum member includes an aluminum member 1, a first film 2, and a second film 3.
- the aluminum member 1 contains silicon as an impurity and / or additive
- the silicon 5 is included in the first film 2.
- the surface-coated aluminum member is preferably applied to a part of the combustion chamber. In this case, in addition to the high heat insulation and high heat uniformity required for the combustion chamber, a plurality of performances such as corrosion resistance, impact resistance, durability, water repellency, and oil repellency can be imparted.
- the surface of the aluminum member 1 is covered with a first film 2 and a second film 3.
- the aluminum member 1 include aluminum, aluminum alloys containing alloy components such as silicon and copper, or aluminum alloys containing them, aluminum cast materials, aluminum die cast materials (ADC), and the like. Also includes processed products processed into parts. More specifically, the aluminum alloy is AC material such as AC4, AC8, AC8A, AC9, ADC material such as ADC10 to ADC14, A1000 to A7000, and the like.
- heat insulation required for a part of the combustion chamber means the performance and / or function of insulating heat from the combustion part of the internal combustion engine to the outside and / or from the outside to the combustion part. is doing.
- the aluminum member 1 may contain impurities and / or additives.
- the impurities and / or additives include silicon (Si), copper (Cu), magnesium (Mg), zinc (Zn), iron (Fe), tin (Sn), manganese (Mn), nickel (Ni), Examples include titanium (Ti).
- These impurities and / or additives are preferably 8% by mass or more and 30% by mass or less with respect to the aluminum member. Since the aluminum member 1 contains an impurity element other than aluminum, and the anodic oxide film is difficult to grow around the impurity element, the first film 2 that is the anodic oxide film has microscopic pores (gap). Is easily formed.
- silicon 5 added to improve the castability, wear resistance, and the like of the aluminum member 1 is illustrated as an impurity.
- the first film 2 is provided on the surface of the aluminum member 1 and includes a first anodized film 2a and a second anodized film 2b.
- the first film 2 provides the aluminum member 1 with a plurality of functions such as high heat insulation, corrosion resistance, impact resistance, durability, water repellency, and oil repellency.
- coat 2 is comprised so that it may function as a heat insulation film
- the first anodic oxide film 2a is a porous film provided on the surface of the aluminum member 1 by applying direct current electrolysis.
- the first anodized film 2a has a regular orientation by a direct current electrolysis method. For this reason, the first anodic oxide film 2a has more pores (first pores) than the second anodic oxide film 2b, and is configured to have a higher porosity.
- the first pores are also formed by the presence of silicon 5 or the like.
- the first anodic oxide film 2a has a higher heat insulating property than the second anodic oxide film 2b because the thermal conductivity of the air in the first pores existing in large numbers therein is low. Further, since the first anodic oxide film 2 a has corrosion resistance, it is possible to prevent a substance that causes corrosion of the aluminum member 1 from reaching the aluminum member 1.
- the first anodic oxide film 2a provides high heat insulation and corrosion resistance to the aluminum member 1, and also provides high heat insulation performance and corrosion resistance performance in cooperation with the second anodic oxide film 2b. ing.
- the second anodic oxide film 2b is a porous film provided on the surface of the aluminum member 1 by applying AC / DC superposition electrolysis.
- the second anodic oxide film 2b has a plurality of pores (second pores). The second pores are also formed by the presence of silicon 5 or the like.
- the second anodic oxide film 2b has denseness due to random orientation by an AC / DC superposition electrolysis method. That is, the second anodized film 2 b is an anodized film having no orientation grown in a random direction with respect to the surface of the aluminum member 1. For this reason, the second anodic oxide film 2b has higher corrosion resistance than the first anodic oxide film 2a, and prevents substances that cause corrosion of the aluminum member 1, such as water, from reaching the aluminum member 1. it can.
- the second pores are oriented in a random direction, it is possible to prevent the substance water that causes corrosion from entering into many pores at a time under pressure in one direction.
- “Dense” means that the porosity of the second anodic oxide film 2b is smaller than that of the first anodic oxide film 2a.
- the second anodized film 2b improves the heat insulation of the first anodized film 2a by covering the first anodized film 2a like a lid without blocking the first pores of the first anodized film 2a. That is, the second anodic oxide film 2b imparts high corrosion resistance to the aluminum member 1 and improves the heat insulation of the first anodic oxide film 2a.
- the second anodic oxide film 2b has a high density and hardness and a small surface roughness. Note that “the surface roughness is small” means that the surface of the second anodic oxide film 2b has better smoothness than the first anodic oxide film 2a.
- Good smoothness of the second anodic oxide film 2b affects the smoothness of the second film 3 formed on the surface thereof, and the surface smoothness of the second film 3 can be improved. Furthermore, since the second anodic oxide coating 2b has nano-level second pores, an anchor effect is exerted on the close contact portion (connection portion) between the first coating 2 and the second coating 3. Can be granted. Thereby, the adhesiveness of the 1st membrane
- the film thickness, porosity, and hardness of the first anodic oxide film 2a and the second anodic oxide film 2b vary depending on the type, temperature, or electrolysis conditions of the electrolyte used for film formation. For this reason, AC / DC superposition electrolysis and direct current electrolysis can be processed at different electrolytes or temperatures depending on the purpose.
- the first anodic oxide film 2a and the second anodic oxide film 2b are preferably formed in the same anodizing treatment bath, and more preferably formed under substantially the same temperature conditions.
- the connecting portion (boundary portion) between the first anodic oxide coating 2a and the second anodic oxide coating 2b. ) Can be formed continuously. Thereby, the connection part of the 1st anodic oxide film 2a and the 2nd anodic oxide film 2b becomes integral and firm. As a result, it is possible to prevent the first pores of the first anodic oxide film 2a from being blocked by a sealing process described later, and to prevent a decrease in heat insulation. In addition, it is possible to prevent the occurrence of poor adhesion or peeling between the anodized films.
- sulfuric acid H 2 SO 4
- oxalic acid H 2 C 2 O 4
- phosphoric acid H 3 PO 4
- an acidic bath such as chromic acid (H 2 CrO 4 ), or a basic bath such as sodium hydroxide (NaOH), sodium phosphate (Na 3 PO 4 ), or sodium fluoride (NaF).
- an acidic bath such as chromic acid (H 2 CrO 4 )
- a basic bath such as sodium hydroxide (NaOH), sodium phosphate (Na 3 PO 4 ), or sodium fluoride (NaF).
- coat 2 on the surface is not limited when a specific anodizing bath is used, a sulfuric acid is preferable from a practical viewpoint.
- the porosity of the first anodic oxide film 2a can be easily increased depending on the electrolysis conditions. For this reason, the heat insulation of the 1st anodic oxide film 2a can be improved.
- the film thickness of the first film 2 is not particularly limited. More specifically, the film thickness of the first film 2 is preferably 3 ⁇ m or more and 300 ⁇ m or less from the viewpoint of practicality. The film thickness of this film can be set to a required film thickness depending on the application.
- the pores of the first film 2 can be pores sealed by a sealing treatment, if necessary.
- the sealing treatment include boiling water and high-temperature hydrating sealing treatment using an aqueous solution in which a metal salt is added to boiling water, and low-temperature sealing treatment using a strongly basic aqueous solution. It is not limited to the hole processing method.
- the sealing process is performed on the aluminum member 1 provided with the first coating 2, the first pores and the second pores are sealed by a product (not shown) caused by the sealing treatment liquid.
- One anodized film and a second anodized film can be obtained. Thereby, corrosion resistance can be improved, maintaining the heat insulation of a surface covering aluminum member.
- the first film 2 since the first film 2 includes the first anodic oxide film 2a and the second anodic oxide film 2b, it is sufficiently high without performing the rust prevention treatment such as the sealing treatment described above. It has heat resistance and corrosion resistance. For this reason, the first film 2 can be subjected to the sealing treatment, the cleaning treatment, the repair treatment, the coating treatment, etc. depending on the application or purpose, but the sealing treatment may be omitted. it can.
- the necessity of performing the sealing process can be selected as appropriate according to the required function. In this case, the number of manufacturing steps can be reduced, and a surface-coated aluminum member with reduced manufacturing costs can be obtained.
- the second film 3 has a higher thermal conductivity than the first film 2 and is formed on the surface of the first film 2.
- coat 3 is comprised on the surface of the 1st membrane
- the second film 3 has a heat conductivity relatively higher than that of the first film 2, so that the heat transfer by heat radiation (radiation) is higher than that of the surface-coated aluminum member coated only with the first film 2. Can be suppressed.
- the surface-coated aluminum member when heat is applied to a predetermined portion of the surface of the surface-coated aluminum member to which the first film 2 and the second film 3 are applied (hereinafter also referred to as heat input), the surface-coated aluminum
- the temperature distribution of the second film 3 located on the surface of the member can be made uniform quickly. As a result, good thermal uniformity can be imparted to the surface-coated aluminum member.
- the second film 3 Since the second film 3 is formed on the second anodic oxide film 2b having high smoothness, the second film 3 has a small surface area. Thereby, the 2nd membrane
- the high smoothness of the surface of the second coating 3 suppresses the adhesion of fuel and the adhesion and / or adhesion of unburned matter such as soot. Can do.
- the second film 3 is in close contact with the first film 2 by providing an anchor effect by the nano-level pores of the upper layer of the first film 2 (second anodic oxide film 2b). Thereby, the adhesion between the second film 3 and the first film 2 becomes stronger, and peeling of both films can be prevented.
- the second film 3 may be a material having a higher thermal conductivity than the first film 2. More specifically, as the second film 3, nickel (Ni), silver (Ag), copper (Cu), aluminum nitride (AlN), silicon carbide (SiC), tungsten (W), molybdenum (Mo), etc. Or a composite of these. Examples of the composite include a composite plating layer containing aluminum nitride powder in a nickel plating layer. In addition, there are three types of heat transfer: “heat conduction”, “convection”, and “radiation (radiation)”, and the radiant heat is transmitted to the coating that reflects radiation in this second coating. Insulation by preventing can be expected.
- the thermal conductivity of the second film 3 is higher than that of the first film 2, it can function as a thermal diffusion film of the surface-coated aluminum member. More specifically, the thermal conductivity of the second coating 3 is preferably 50 W / (m ⁇ K) or more, and more preferably 100 W / (m ⁇ K) or more. Within the above range, good heat transfer can be obtained. If the thermal conductivity of the second coating 3 is less than 50 W / (m ⁇ K), the expected effect may not be obtained.
- FIG. 2 is a configuration diagram showing an outline of the anodizing apparatus 10 used in the first film forming process, the first anodic oxide film forming process and / or the second anodic oxide film forming process.
- the anodizing apparatus 10 includes an electrolytic bath 11 that contains an anodizing solution, an anode 12 and a pair of cathodes 13 that are immersed in the anodizing solution, a conductive wire 14, and a power source 15. It has.
- the pair of cathodes 13 are disposed so as to face each other in the electrolytic bath 11 with the anode 12 as the center.
- the anode 12 and the pair of cathodes 13 are connected to a power source 15 through a conductive wire 14.
- the anodizing apparatus 10 is configured to apply DC electrolysis and AC / DC superposition electrolysis by a power source 15 via an anode 12, a pair of cathodes 13 and a conductive wire 14.
- the anodizing apparatus 10 includes a stirring means (not shown) that can stir the anodizing solution.
- a stirring means (not shown) that can stir the anodizing solution.
- each of a pair of cathode 13 is comprised so that the surface area of 20 times or more of the surface area of the aluminum member 1 used as the anode 12 may be immersed in an anodizing process liquid.
- the first film 2 having a uniform film thickness can be obtained.
- the aluminum member 1 is arrange
- a film 2b is formed.
- the material of the cathode 13 should just be a material which functions as the cathode 13, and a carbon plate, an aluminum plate, a stainless steel plate etc. other than titanium can be used.
- FIG. 3 is a schematic flow diagram for explaining a method of forming the first film 2 and the second film 3 with respect to the surface covering method of the aluminum member.
- the second film 3 is formed by the second film formation step (S 2 ).
- a first coating step (S 1) after forming a second anodic oxide film 2b by the first anodic oxide film formation step (S 11), a second anodic oxide film formation step the (S 12) to form a first anodic oxide film 2a.
- coat 3 is formed by a 2nd membrane
- the second anodic oxide film 2 b is formed by applying AC / DC superposition electrolysis to the aluminum member 1. That is, the first anodic oxide film forming step is performed by an AC / DC superposition method in which an AC current is superimposed on a DC current (hereinafter also referred to as AC / DC superposition electrolysis method).
- the second anodic oxide film 2b is formed in the vicinity of the surface mainly including the surface of the aluminum member 1.
- the second anodic oxide film 2b is a porous film provided in the vicinity of the surface of the aluminum member by applying AC / DC superposition electrolysis, and has a plurality of pores (second pores).
- the second anodic oxide film 2b has a dense property due to random orientation. Therefore, it is possible to make it difficult for a substance that causes corrosion to pass through to the aluminum member, so that the corrosion resistance is high, the hardness is high, and the surface roughness is small (the surface is smooth). “Dense” means that the porosity of the second anodic oxide film 2b is smaller than that of the first anodic oxide film 2a.
- the second anodic oxide film 2b formed in the first anodic oxide film forming step (S 11 ) covers the first anodic oxide film 2a as a lid having a denseness without blocking the first pores. Thereby, the heat insulation of the 1st membrane
- the frequency of the high-frequency current in the first anodic oxide film forming step (S 11 ) is preferably 5 kHz to 20 kHz, and more preferably 10 kHz to 20 kHz.
- the positive electrode voltage is preferably 12 V or more and 70 V or less, and the negative electrode voltage is preferably ⁇ 10 V or more and 0 V or less. If it is in the said range, the uniformity of film thickness can be improved and the 2nd anodic oxide film 2b with few variations by a part of soaking
- the energization time is not particularly limited, and can be implemented in a practical time.
- First anodic oxide film 2a is formed (hereinafter also referred to as direct current electrolysis).
- the second anodic oxide film 2 b is formed in the vicinity of the surface of the aluminum member 1. That is, the first anodic oxide film 2 a is formed between the second anodic oxide film 2 b and the aluminum member 1. Since the first anodic oxide film 2a has orientation, it has more pores (first pores) than the second anodic oxide film 2b. That is, the first anodic oxide film 2a is coarse and the second anodic oxide film 2b is dense in terms of pore size, number and / or distribution. The first pores are also formed by the presence of silicon 5 or the like.
- the first anodic oxide film 2a also has corrosion resistance due to aluminum oxide, and can prevent a substance that causes corrosion from reaching the aluminum member 1.
- the first anodic oxide film 2a can provide corrosion resistance to the aluminum member 1 and can provide highly reliable heat insulation by a synergistic effect with the second anodic oxide film 2b.
- the first anodized film forming step (S 11 ) and the second anodized film forming step (S 12 ) can be carried out with different anodizing treatment liquids or temperatures depending on the purpose, but the same It is preferable to carry out with an anodizing liquid, and it is more preferable to carry out at the same temperature.
- the first anodic oxide film 2a and the second anodic oxide film 2b are substantially equal, the first anodic oxide film 2a and the second anodic oxide film 2b are continuously formed. be able to. Thereby, the connection part of the 1st anodic oxide film 2a by direct current electrolysis and the 2nd anodic oxide film 2b by AC / DC superposition electrolysis becomes integral and firm.
- the sealing treatment described later eliminates the possibility of blocking the pores of the anodic oxide film by direct current electrolysis, and prevents a decrease in heat insulation.
- heat insulation and corrosion resistance can be provided to the anodized film 2.
- anodizing solution examples include an acid bath such as sulfuric acid (H 2 SO 4 ), oxalic acid (H 2 C 2 O 4 ), phosphoric acid (H 3 PO 4 ), chromic acid (H 2 CrO 4 ), water, and the like. Any of basic baths such as sodium oxide (NaOH), sodium phosphate (Na 3 PO 4 ), and sodium fluoride (NaF) may be used.
- the aluminum member 1 that generates the first film 2 to be subjected to the sealing treatment described later on the surface is not limited when a specific anodizing bath is used, but sulfuric acid is preferable from a practical viewpoint.
- the temperature of the anodizing solution may be any temperature at which the first anodized film 2a and the second anodized film 2b can be formed. More specifically, the temperature of the anodizing solution is preferably 5.0 ° C. or higher and 30 ° C. or lower, and more preferably 5.0 ° C. or higher and 20 ° C. or lower. Within the above range, for example, the first anodic oxide film 2a and the second anodic oxide film 2b having a predetermined hardness while requiring no film formation for cooling to about 0 ° C. such as a hard film method. Both of these can be formed by anodizing treatment. Moreover, the continuity of the connection part of the 1st anodic oxide film 2a and the 2nd anodic oxide film 2b can be improved, and the integral and strong 1st film
- a second film 3 (having a higher thermal conductivity than the first film 2 is formed on the first film 2 by using a predetermined film forming method.
- the film forming method may be a film forming method having desired characteristics. Examples of the film forming method include plating methods such as electroplating and chemical plating, spraying methods, brush coating, screen printing and other coating methods, CVD (Chemical Vapor Deposition), vacuum deposition methods, sputtering methods, ion plating, and the like. PVD (Physical Vapor Deposition) can be used.
- the film thickness of the second film 3 may be set so as to obtain desired characteristics, and is not particularly limited.
- Examples of the second film 3 formed in the second film forming step (S 2 ) include a film made of a component such as nickel, silver, copper, aluminum nitride, silicon carbide, tungsten, molybdenum, or a composite thereof. It is done.
- Examples of the composite film include a composite plating layer containing aluminum nitride powder in a nickel plating layer.
- a general sealing process can be performed between the second film forming step (S 2 ) and the first film forming step (S 1 ).
- the sealing treatment include a strongly basic sealing bath, boiling water sealing, nickel salt sealing, and the like, but are not limited to a specific sealing treatment.
- the pores of the first film 2 are permeated into the sealing liquid by adhering the sealing liquid to the surface of the first film 2.
- the sealing liquid enters the pores of the first coating 2 and forms a compound in the pores.
- the sealing liquid mainly penetrates into the second pores of the second anodic oxide film 2b to form a compound. Thereby, the heat insulation of the 1st membrane
- the sealing treatment step may be performed by applying or spraying the treatment liquid onto the object having the first film 2 or immersing the object in the treatment liquid and holding it in the air, followed by washing and drying.
- the sealing treatment method by coating or spraying can partially seal. For this reason, when processing a large component, the large tank for immersing a large component on processing can be made unnecessary.
- the second anodic oxide film 2b serves as a lid for the first anodic oxide film 2a and covers the first pores without blocking them.
- the second pores are sealed while preventing the many first pores from being sealed, thereby preventing the heat insulating property of the first anodic oxide film 2a from being deteriorated. be able to.
- the connection part of the 1st anodic oxide film 2a and the 2nd anodic oxide film 2b is integrally formed firmly. Therefore, the sealing treatment can improve the corrosion resistance and prevent the heat insulation and the reliability of the first coating 2 from being lowered.
- the first coating 2 is passed through the first film forming step (S 1), even without an antirust treatment such as the sealing treatment, has a sufficiently high heat resistance and corrosion resistance. For this reason, the sealing process among post-processes such as a sealing process, a cleaning process, a repair process, and a coating process can be omitted. Whether or not the sealing process is necessary can be appropriately selected according to the required function. When the sealing process is not performed, the number of steps can be reduced, and the manufacturing cost can be reduced.
- the first film 2 having an effect as a heat insulating film is employed on the aluminum member 1, and relative to the first film 2.
- a second film 3 having an effect as a heat diffusion film having a high thermal conductivity is provided on the first film 2.
- the first film 2 has a two-layer structure composed of an upper layer and a lower layer, and a second anodic oxide film 2b formed by an AC / DC superposition electrolysis method is adopted as the upper layer, and a first anodic oxide film formed by a direct current electrolysis method as the lower layer. 2a is adopted. Since the aluminum member 1 contains an impurity element other than aluminum, and an anodic oxide film hardly grows around the impurity element, microscopic pores (gap) are easily formed. If the pores are present on the surface as open pores, the heat insulating property is lowered, so that the pores need to be closed.
- the dense second anodic oxide film 2b having a low porosity is formed on the rough first anodic oxide film 2a having a high porosity, the first having high heat insulation is provided.
- the first anodic oxide film 2a can be covered with the second anodic oxide film 2b having high corrosion resistance without blocking the nano-level and micro-level pores in the anodic oxide film 2a. As a result, it is possible to obtain a surface-coated aluminum member having both high heat insulating properties and high corrosion resistance.
- the second anodic oxide film 2b having good smoothness is employed as the upper layer of the first film 2. Therefore, by forming the second film 3 on the smooth surface of the second anodic oxide film 2b, the surface of the second film 3 also becomes smooth. As a result, the surface area of the second coating 3 can be reduced and the heat insulating property of the surface-coated aluminum member can be improved.
- the second anodic oxide film 2b having nano-level pores is employed as the upper layer of the first film 2.
- the anchor effect by the 2nd anodic oxide film 2b can be provided with respect to the adhesiveness of the 1st film
- FIG. it is possible to improve the adhesion between the first film 2 and the second film 3 and prevent the bonding with the aluminum member 1 and the peeling with respect to the adhesion.
- a step of forming the first anodized film 2a, and a second anodized film The method of performing the process of forming the film 2b in the same treatment bath is employed.
- the components of the first anodic oxide film 2a and the second anodic oxide film 2b are made substantially equal, and the first anodic oxide film 2a and the second anodic oxide film 2b are continuously formed. it can.
- the connection part of the 1st anodic oxide film 2a and the 2nd anodic oxide film 2b can be strengthened integrally. As a result, poor adhesion and / or peeling between the two anodized films can be prevented.
- Patent Document 1 the flame spreads concentrically from the spark plug in the combustion chamber. For this reason, even if the heat insulation performance of the wall surface is gradually reduced as the distance from the spark plug increases, it is difficult to make the wall surface temperature uniform quickly. Therefore, there is a problem that knocking at a position on the way away from the spark plug, particularly knocking in a region on the intake valve side where knocking is likely to occur cannot be sufficiently suppressed.
- Patent Document 1 after forming a thermal barrier film with an anodized film on the front surface of the bottom surface of the cylinder head, a masking process is performed only on the anodized film in a region away from the spark plug, and an area corresponding to the spark plug is formed.
- a masking process is performed only on the anodized film in a region away from the spark plug, and an area corresponding to the spark plug is formed.
- a thermal barrier film having a low thermal conductivity and a low heat capacity is provided on the top surface of the piston. Since heat is easily escaped by the heat shielding film and the temperature does not easily rise, a heat retaining material having a high volume specific heat is provided in a part of the heat shielding film. However, when a heat retaining material having a high body specific heat is provided, there is a problem that swing characteristics, that is, characteristics in which the film temperature follows the gas temperature in the combustion chamber cannot be obtained while having heat insulation performance.
- Patent Document 2 if the fuel adheres unevenly to the top surface of the piston, heat is taken away by the heat of vaporization, resulting in a problem that the temperature distribution on the top surface of the piston becomes uneven. Further, for example, in Patent Document 2, when an anodic oxide film is employed as the heat shielding film, an iron-manganese alloy is used as the heat retaining material, and therefore, there is a possibility that peeling with respect to bonding or adhesion to the aluminum member may occur.
- the surface-coated aluminum member of the present embodiment when the surface-coated aluminum member of the present embodiment is applied to a part of the combustion chamber, the surface of the surface-coated aluminum member to which the first coating 2 and the second coating 3 are applied (that is, the first coating 2).
- the temperature distribution of the second film 3 can be made uniform quickly. That is, while the combustion chamber is burning, the first film 2 under the second film 3 of the surface-coated aluminum member has a heat insulating effect.
- coat 2 is low, the specific heat is not zero.
- the knocking resistance of the combustion chamber can be improved.
- the heat around the spark plug passes through the second film 3 of the surface-coated aluminum member having a high thermal conductivity, and around the low temperature intake valve. It is transmitted to the wall. That is, heat can be quickly transferred to the part far from the spark plug as a whole. Since the temperature around the intake valve where the temperature is relatively low can be increased, the wall surface temperature inside the combustion chamber can be made uniform quickly. Further, even when the fuel adheres unevenly to the piston top surface and the temperature distribution becomes non-uniform, the temperature distribution becomes uniform due to the presence of the first coating 2, so that the exhaust heat is likely to heat up. The combustion chamber including the periphery of the valve is uniformly cooled by the heat of vaporization. As a result, knocking that is abnormal combustion can be suppressed. Further, since the surface covering / BR> A ruminium member has high heat insulating properties and good responsiveness to the wall surface temperature during combustion, good swing characteristics can be obtained.
- the second film 3 of the surface-coated aluminum member has good thermal uniformity. For this reason, it is not necessary to change the film thickness or the surface roughness of the anodic oxide film to be the first film 2 even when the portion that receives heat while the combustion chamber is burning is fixed. For example, as the distance from the spark plug increases or away from the spark plug, the thickness of the anodized film is reduced to reduce heat insulation, or the surface roughness of the anodized film is increased to increase thermal diffusivity (uniformity). There is no need to increase thermal properties. Therefore, it is unnecessary to use special masking, jigs, etc., and the anodized film (first film 2) can be formed by a simple method. As a result, the number of manufacturing processes and management items can be reduced.
- the surface of the second coating 3 of the surface-coated aluminum member is made smooth, it suppresses adhesion of fuel or sticking or adhesion of unburned material such as soot during combustion of the internal combustion engine. Can do.
- connection portion between the first anodic oxide film 2a and the second anodic oxide film 2b in the first film 2 of the surface-coated aluminum member can be integrated and strengthened. For this reason, when the internal combustion engine is burned, the first coating 2 excellent in impact resistance, explosion pressure resistance, or repeated stress of thermal expansion and thermal contraction can be obtained. Therefore, a highly reliable and durable surface-coated aluminum member can be obtained.
- the first film 2 having the two-layer structure including the first anodic oxide film 2a and the second anodic oxide film 2b is illustrated, but the present invention is not limited to this.
- a dense second anodized film randomly oriented is formed on the uppermost layer of the first film by AC / DC superposition and at least one of the lower layers is formed.
- a sparse first anodic oxide film having orientation is formed on the above layers by direct current electrolysis, and the second film of the present embodiment may be formed thereon as a thermal diffusion layer.
- the uppermost anodic oxide film layer is the Nth anodic oxide film layer corresponding to the second anodic oxide film in this embodiment (N is a natural number of 3 or more), and the aluminum member is used.
- N is a natural number of 3 or more
- the aluminum member is used.
- a film is formed.
- the last film What is necessary is just to form a 2nd membrane
- an anodic oxide film with improved strength, heat insulation and corrosion resistance can be obtained as compared with the above-described embodiment.
- the use of the aluminum member as a part of the combustion chamber is exemplified, but the present invention is not limited to this.
- the aluminum member include outboard motor parts such as an outboard motor oil pan, a gear case, and a propeller.
- An outboard motor is a wearable marine propulsion system that comes into contact with seawater and sea breeze, and therefore, components constituting the outboard motor are required to have high corrosion resistance.
- the oil pan stores engine oil and also has a function of cooling engine oil with traveling wind, and needs to be in direct contact with seawater and sea breeze. For this reason, high corrosion resistance is required. Since the anodized film formed on the aluminum member of the present invention has sufficient corrosion resistance, it can also be used as an outboard motor component.
- Test Example 1 As the aluminum member, an aluminum alloy (AC8A) was used as a test piece. AC8A was anodized by direct current electrolysis to form an anodized film having a thickness of 11 to 21 ⁇ m. The anodizing treatment was performed in a sulfuric acid bath at 20 ° C. and a concentration of 200 g / L for 20 minutes at a current density of 1.5 A / dm 2 . The obtained test piece having only the first anodic oxide film by direct current electrolysis was used as the test piece of Test Example 1.
- AC8A was used as the aluminum member.
- AC8A was anodized by an AC / DC superposition electrolysis method to form a 16-18 ⁇ m anodic oxide film.
- the anodizing treatment was performed in a sulfuric acid bath at 20 ° C. and a concentration of 200 g / L with a high-frequency current frequency of 10 kHz and a positive electrode 25 V, a negative electrode ⁇ 2 V, and 10 minutes.
- the test piece having only the second anodic oxide film obtained by the AC / DC superposition electrolysis method was used as the test piece of Test Example 2.
- AC8A was used as the aluminum member.
- AC8A was anodized by an AC / DC superposition electrolysis method to form a film.
- the anodizing treatment was performed in a sulfuric acid bath at 20 ° C. and a concentration of 200 g / L with a high-frequency current frequency of 10 kHz and a positive electrode of 25 V and a negative electrode of ⁇ 2 V for 7 minutes.
- the film was formed by anodizing by direct current electrolysis.
- the anodizing treatment was performed in a sulfuric acid bath at 20 ° C. and a concentration of 200 g / L with a current density of 1.5 A / dm 2 for 10 minutes.
- the film thickness was 17-22 ⁇ m.
- a test piece having only the first film composed of the first anodic oxide film by the direct current electrolysis method and the second anodic oxide film by the AC / DC superposition electrolysis method obtained by the above method was used as a test piece of Test Example 3.
- AC8A was used as the aluminum member.
- AC8A was anodized by an AC / DC superposition electrolysis method to form a film.
- the anodizing treatment was carried out in a sulfuric acid bath at 20 ° C. and a concentration of 200 g / L with a high-frequency current frequency of 10 kHz and a positive electrode 25 V, a negative electrode ⁇ 2 V for 2 minutes.
- the film was formed by anodizing by direct current electrolysis.
- the anodizing treatment was performed in a sulfuric acid bath at 20 ° C. and a concentration of 200 g / L for 35 minutes with a current density of 2 A / dm 2 .
- the film thickness was 60 to 80 ⁇ m.
- Ni plating was applied to form a second film serving as a heat diffusion film on the first film.
- An aluminum alloy was placed on the cathode, and electroplating was performed by applying current at a current density of 20 A / dm 2 for 2 minutes under the conditions of a plating bath having a pH of 4.0 and a temperature of 65 ° C.
- a mixed solution of nickel sulfate 500 g / L, boric acid 45 g / L, saccharin soda 3.2 g / L, and 50% phosphorous acid 1.5 g / L was used.
- SUS304 which is an insoluble electrode, was used.
- a nickel-phosphorus (Ni-P) plating film was formed on the surface of the aluminum alloy by electrolytic plating. The obtained test piece having the first film and the second film was used as the test piece of Test Example 4.
- AC8A was used as the aluminum member.
- AC8A was subjected to an anodic oxidation treatment by an AC / DC superposition electrolytic method to form a second anodic oxide film.
- the anodizing treatment was performed in a sulfuric acid bath at 20 ° C. and a concentration of 200 g / L with a high-frequency current frequency of 10 kHz and a positive electrode 25 V, a negative electrode ⁇ 2 V for 2 minutes. Thereafter, the first anodic oxide film was formed by anodic oxidation by a direct current electrolysis method.
- the anodic oxidation treatment was performed in a sulfuric acid bath at 20 ° C.
- test piece having a first film composed of a first anodic oxide film by a direct current electrolysis method and a second anodic oxide film by an AC / DC superposition electrolysis method was obtained.
- sputtering was performed on the test piece in order to form a second film serving as a thermal diffusion film on the first film.
- the sputtering process is performed by using DC magnetron sputtering and introducing a discharge gas Ar (5 to 10 sccm) under the conditions of DC discharge with a gas pressure of 0.5 to 20 Pa and a power of 50 W. As a result, a molybdenum film was formed.
- the obtained test piece was used as the test piece of Test Example 5.
- AC8A was used as the aluminum member.
- AC8A was subjected to an anodic oxidation treatment by an AC / DC superposition electrolytic method to form a second anodic oxide film.
- the anodizing treatment was performed in a sulfuric acid bath at 20 ° C. and a concentration of 200 g / L with a high-frequency current frequency of 10 kHz and a positive electrode 25 V, a negative electrode ⁇ 2 V for 2 minutes. Thereafter, the first anodic oxide film was formed by anodic oxidation by a direct current electrolysis method.
- the anodic oxidation treatment was performed in a sulfuric acid bath at 20 ° C.
- test piece having a first film composed of a first anodic oxide film by a direct current electrolysis method and a second anodic oxide film by an AC / DC superposition electrolysis method was obtained.
- test piece was used as a test piece of Test Example 6.
- AC8A was used as the aluminum member.
- AC8A was subjected to an anodic oxidation treatment by an AC / DC superposition electrolytic method to form a second anodic oxide film.
- the anodizing treatment was performed in a sulfuric acid bath at 20 ° C. and a concentration of 200 g / L with a high-frequency current frequency of 10 kHz and a positive electrode 25 V, a negative electrode ⁇ 2 V for 2 minutes. Thereafter, the first anodic oxide film was formed by anodic oxidation by a direct current electrolysis method.
- the anodizing treatment was performed in a sulfuric acid bath at 20 ° C.
- test piece having a first film composed of a six-layer film in which a first anodized film by a direct current electrolysis method and a second anodized film by an AC / DC superposition electrolysis method were alternately laminated was obtained.
- test piece was used as a test piece of Test Example 7.
- the surface roughness (Ra) was measured with a surface roughness meter.
- Table 1 shows the density, hardness, and surface roughness values of the test pieces of Test Examples 1 to 7. Since the test pieces of Test Examples 3 to 7 were provided with two anodic oxide films having different hardnesses, the hardness was not measured.
- Test Example 2 had lower surface roughness and higher density than Test Example 1. From this result, the anodized film formed by AC / DC superposition electrolysis has higher water repellency, oil repellency and impact resistance than the anodized film formed by direct current electrolysis, and contributes to the improvement of heat insulation. I understood. Moreover, it turned out that the anodic oxide film formed by direct current electrolysis has higher heat insulation than the anodic oxide film formed by AC / DC superposition electrolysis.
- the test piece of Test Example 3 had a lower surface roughness and a higher density than Test Example 1. From this result, the two-layered anodic oxide film having the AC / DC superposed electrolytic anodic oxide layer as the upper layer and the DC electrolytic anodic oxide layer as the lower layer is higher in water repellency than the anodic oxide film of the single-layer DC electrolytic anodic oxide layer, It was found to have oil repellency and impact resistance. It was also found that the two-layered anodic oxide film has both high heat insulation and impact resistance. These functions, when applied to an internal combustion engine with a two-layered anodic oxide coating, exhibit high impact resistance that can withstand actual use, and are effective in reducing deposits before and after combustion and improving corrosion resistance. I understood it.
- test Example 4 When comparing Test Example 1 and Test Example 4, the test piece of Test Example 4 had lower surface roughness and higher density than Test Example 1. From this result, the test example 4 having the first film and the nickel-phosphorous plating film as the second film has higher water repellency and repellent properties than the test example 1 having only the anodic oxide film of the DC electrolytic anodized layer. It was found to have oil resistance and impact resistance. In addition, it was found that Test Example 4 including the first film and the nickel-phosphorus plating film as the second film achieves both high heat insulation and high impact resistance. These functions exhibit high impact resistance that can withstand actual use when a surface-coated aluminum member having a first coating and a nickel-phosphorous plating coating as a second coating is applied to a part of the combustion chamber. It has been found that it is effective in reducing deposits before and after combustion and improving corrosion resistance.
- test Example 5 When comparing Test Example 1 and Test Example 5, the test piece of Test Example 5 had lower surface roughness and higher density than Test Example 1. From this result, the test example 5 having the first film and the molybdenum film as the second film has higher water repellency, oil repellency, resistance to resistance than test example 1 having only the anodized film of the DC electrolytic anodized layer. It was found to have impact properties. Moreover, it turned out that the test example 5 provided with a molybdenum film
- test Example 6 When comparing Test Example 1 and Test Example 6, the test piece of Test Example 6 had lower surface roughness and higher density than Test Example 1. From this result, the water repellency, oil repellency, and resistance of test example 6 including the first film and the silver film as the second film are higher than those of test example 1 including only the anodized film of the DC electrolytic anodized layer. It was found to have impact properties. Moreover, it turned out that the test example 6 provided with a silver film as a 1st membrane
- test Example 7 When comparing Test Example 1 and Test Example 7, the test piece of Test Example 7 had lower surface roughness and higher density than Test Example 1. From this result, the test example 7 having the first film and the silver film as the second film is higher in water repellency, oil repellency and resistance than the test example 1 having only the anodic oxide film of the DC electrolytic anodized layer. It was found to have impact properties. Moreover, it turned out that the test example 7 provided with a silver film as a 1st film
- FIG. 4 shows a cross-sectional photograph obtained by photographing the film cross section of Test Example 6.
- FIG. 4 shows a second anodic oxide film in which the layer on the paper surface is formed by AC / DC superposition electrolysis from the broken line in the first film, and the layer below the paper surface from the broken line in the first film is formed by direct current electrolysis.
- the first anodic oxide film is shown, and the main pores in the first film are shown using arrows.
- the produced test piece is formed with a first film, an anodic oxidation layer subjected to AC / DC superposition electrolytic treatment on the upper layer, and an anodic oxidation layer subjected to direct current electrolysis treatment on the lower layer.
- the anodic oxide layer under the direct current electrolytic treatment of the first film it was difficult to form the film due to the presence of silicon, and the portions where the film was not formed were pores.
- the film subjected to the direct current electrolytic treatment under the first film micro-level pores existed, and in the film subjected to the AC / DC overlapping electrolytic process in the upper layer of the first film, no pores existed. In addition, no micro-level pores were observed around the silicon in the film, and it was confirmed that the film tightly covered the silicon periphery.
- the thermal conductivity of the anodized film of Test Example 1 was 0.42 W / (m ⁇ K).
- the thermal conductivity of the second film of Test Example 4 is 76 W / (m ⁇ K), and the thermal conductivity of the second film of Test Example 5 is 128 W / (m ⁇ K).
- the thermal conductivity of the second film of Test Example 6 is 155 W / (m ⁇ K), and the thermal conductivity of the second film of Test Example 5 is 157 W / (M ⁇ K).
- the nickel-phosphorous plating film showed higher thermal conductivity than the anodized film, and the second film made of nickel-phosphorous plating had a temperature distribution in the combustion chamber as a heat diffusion layer. It was found that the effect of homogenizing was exhibited. Also in Test Example 5, the molybdenum film exhibits higher thermal conductivity than the anodic oxide film, and the second film made of the molybdenum film exhibits the effect of making the temperature distribution in the combustion chamber uniform as a heat diffusion layer. I found out that Furthermore, in Test Example 6 and Test Example 7, the silver film exhibits higher thermal conductivity than the anodized film, and the second film made of the silver film makes the temperature distribution in the combustion chamber uniform as a heat diffusion layer. It was found that the effect to do.
- the surface covering method and the surface covering aluminum member of the aluminum member and the piston for an internal combustion engine provided with both high heat insulation and high heat uniformity according to the present invention, the high heat insulation and high heat uniformity, and You can make them compatible.
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Abstract
Description
本発明に係る表面被覆アルミニウム部材の一実施の形態について、添付図面を参照してさらに詳細に説明する。図1は、本実施の形態の表面被覆アルミニウム部材を示す概略的な断面図である。図1に示すように、表面被覆アルミニウム部材は、アルミニウム部材1と、第一の皮膜2と、第二の皮膜3と、を備えている。なお、アルミニウム部材1が不純物及び/又は添加物としてシリコンを含む場合、シリコン5が第一の皮膜2により内包されている。表面被覆アルミニウム部材は、燃焼室の一部に適用されることが好ましい。この場合、燃焼室に要求される高い断熱性と高い均熱性に加えて、耐食性、耐衝撃性、耐久性、撥水性、撥油性等の複数の性能を付与することができる。
以上の構成を備える陽極酸化皮膜について、その作動形態を説明することにより、アルミニウム部材の表面被覆方法の一実施の形態について添付図面を参照してさらに詳細に説明する。
本実施の形態によれば、表面被覆アルミニウム部材の皮膜として、アルミニウム部材1の上に断熱膜としての効果を有する第一の皮膜2を採用し、且つ、第一の皮膜2に対して相対的に熱伝導率が高い熱拡散膜としての効果を有する第二の皮膜3を第一の皮膜2の上に設けている。これにより、第一の皮膜2の断熱膜の効果により、表面被覆アルミニウム部材に、単層の陽極酸化皮膜のみの構造よりも高い断熱性を付与することができる。また、第一の皮膜2より第二の皮膜3の熱伝導率が相対的に高いため、第一の皮膜2のみの場合と比べて、対流、伝熱及び放射(輻射)の熱移動の三原則における放射を抑制することができる。これにより、熱拡散膜としての第二の皮膜3の効果により、表面被覆アルミニウム部材に、単層の陽極酸化皮膜のみの構造よりも高い均熱性を付与することができる。その結果、断熱性と均熱性とを両立した表面被覆アルミニウム部材を得ることができる。
なお、前述した実施の形態では、第1の陽極酸化皮膜2a及び第2の陽極酸化皮膜2bとからなる二層構造を有する第一の皮膜2を例示したが、本発明はこれに限定されない。例えば、三層構造を有する陽極酸化皮膜である場合も、第一の皮膜の最上層にランダム配向した密な第2の陽極酸化皮膜を交直重畳電解により形成し、その下層のうちの少なくとも1つ以上の層に配向性を有する疎な第1の陽極酸化皮膜を直流電解により形成し、更にその上に熱拡散層として本実施の形態の第二の皮膜を形成すればよい。より方法的には、最上層の陽極皮膜層を本実施の形態における第2の陽極酸化皮膜に相当する第Nの陽極酸化皮膜層とし(Nは、3以上の自然数)、アルミニウム部材に対して最初に皮膜を形成する。その後、機能及び用途において、異なる皮膜を形成した後、第Nの陽極皮膜層の下層側に、本実施の形態における第1の陽極酸化皮膜に相当する陽極酸化皮膜を形成した後、最後の皮膜形成工程として第二の皮膜を形成すればよい。この場合は、前述した実施の形態よりも、強度、断熱性及び耐食性を向上させた陽極酸化皮膜を得ることができる。
アルミニウム部材として、アルミニウム合金(AC8A)を試験片として用いた。AC8Aに対して、直流電解法により陽極酸化を行い、11~21μmの陽極酸化皮膜を形成した。陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、電流密度を1.5A/dm2とし、20分間処理を行なった。得られた直流電解法による第1の陽極酸化皮膜のみを有する試験片を試験例1の試験片とした。
アルミニウム部材としてAC8Aを使用した。AC8Aに対して、交直重畳電解法により陽極酸化を行い、16~18μmの陽極酸化皮膜を形成した。陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、高周波電流の周波数を10kHzとし、正極25V、負極-2V、10分間処理を行なった。得られた交直重畳電解法による第2の陽極酸化皮膜のみを有する試験片を、試験例2の試験片とした。
アルミニウム部材としてAC8Aを使用した。AC8Aに対して、交直重畳電解法により陽極酸化処理し皮膜を形成した。陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、高周波電流の周波数を10kHzとし、正極25V、負極-2V、7分間処理を行なった。その後、直流電解法により陽極酸化処理し皮膜を形成した。陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、電流密度を1.5A/dm2とし、10分間処理を行なった。膜厚は17~22μmであった。前記方法により得られた直流電解法による第1の陽極酸化皮膜と交直重畳電解法による第2の陽極酸化皮膜とからなる第一の皮膜のみを有する試験片を、試験例3の試験片とした。
アルミニウム部材としてAC8Aを使用した。AC8Aに対して、交直重畳電解法により陽極酸化処理し皮膜を形成した。前記陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、高周波電流の周波数を10kHzとし、正極25V、負極-2V、2分間で処理を行なった。その後、直流電解法により陽極酸化処理し皮膜を形成した。陽極酸化処理は、20℃、濃度200g/Lの硫酸浴中で、電流密度を2A/dm2として、35分間処理を行なった。膜厚は60~80μmであった。前記方法により、直流電解法による第1の陽極酸化皮膜と交直重畳電解法による第2の陽極酸化皮膜とからなる第一の皮膜を有する試験片を得た。
アルミニウム部材としてAC8Aを使用した。AC8Aに対して、交直重畳電解法により陽極酸化処理して第2の陽極酸化皮膜を形成した。陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、高周波電流の周波数を10kHzとし、正極25V、負極-2V、2分間処理を行なった。その後、直流電解法により陽極酸化処理して第1の陽極酸化皮膜を形成した。陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、電流密度を2A/dm2とし、35分間処理を行なった。前記方法により、直流電解法による第1の陽極酸化皮膜と交直重畳電解法による第2の陽極酸化皮膜とからなる第一の皮膜を有する試験片を得た。
アルミニウム部材としてAC8Aを使用した。AC8Aに対して、交直重畳電解法により陽極酸化処理して第2の陽極酸化皮膜を形成した。陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、高周波電流の周波数を10kHzとし、正極25V、負極-2V、2分間処理を行なった。その後、直流電解法により陽極酸化処理して第1の陽極酸化皮膜を形成した。陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、電流密度を2A/dm2とし、35分間処理を行なった。前記方法により、直流電解法による第1の陽極酸化皮膜と交直重畳電解法による第2の陽極酸化皮膜とからなる第一の皮膜を有する試験片を得た。
アルミニウム部材としてAC8Aを使用した。AC8Aに対して、交直重畳電解法により陽極酸化処理して第2の陽極酸化皮膜を形成した。陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、高周波電流の周波数を10kHzとし、正極25V、負極-2V、2分間処理を行なった。その後、直流電解法により陽極酸化処理して第1の陽極酸化皮膜を形成した。陽極酸化処理は20℃、濃度200g/Lの硫酸浴中で、電流密度を2A/dm2とし、10分間処理を行なった。その後さらに上記交直重畳電解法と直流電解法を2回繰返し、計6回の陽極酸化処理を行った。前記方法により、直流電解法による第1の陽極酸化皮膜と交直重畳電解法による第2の陽極酸化皮膜が交互に積層された6層の皮膜からなる第一の皮膜を有する試験片を得た。
試験例1~7の試験片各々に対して、密度(g/cm3)、硬度(Hv)及び表面粗さ(Ra)を測定及び算出し、その値を検討した。空隙率に関する密度(g/cm3)の測定は、アルミニウム合金の密度を予め重さと体積により測定した後、皮膜を形成した試験片重量とアルミニウム合金の厚さ分の重量との差から陽極酸化皮膜の重量を算出し、陽極酸化皮膜の厚さと面積から密度を計算した。なお、密度が高いとは空隙率が低いことを示す。硬度(Hv)はビッカース硬度計により測定した。また、表面粗さ(Ra)は表面粗さ計により測定した。試験例1~7の試験片の密度、硬度、表面粗さの値を表1に示す。
なお、試験例3~7の試験片は、硬さの異なる2つの陽極酸化皮膜を備えているため、硬度は測定しなかった。
試験例1及び4~7の各試験片に対して、薄膜熱物性測定装置を用いて熱伝導率(W/(m・K))を評価した。なお、第一の皮膜である陽極酸化皮膜の熱伝導率は、最も値が低い試験例1の熱伝導率を用い、この値と、電解めっき、スパッタリング処理、塗布により形成した第二の皮膜の熱伝導率とを比較した。測定結果を表2に示す。
Claims (10)
- アルミニウム部材の表面に第一の皮膜と、
前記第一の皮膜の表面に前記第一の皮膜よりも熱伝導率が高い第二の皮膜と、を少なくとも備える表面被覆アルミニウム部材。 - 前記第一の皮膜が陽極酸化皮膜である請求項1に記載の表面被覆アルミニウム部材。
- 前記第一の皮膜が、少なくとも空隙率の異なる二種類の陽極酸化皮膜からなる請求項1又は2に記載の表面被覆アルミニウム部材。
- 前記第一の皮膜が、前記アルミニウム部材側の空隙率が高い第1の陽極酸化皮膜と前記第二の皮膜側の空隙率が低い第2の陽極酸化皮膜とからなる二種類の陽極酸化皮膜である請求項1~3のいずれか一項に記載の表面被覆アルミニウム部材。
- 前記第1の陽極酸化皮膜が直流電解を印加して得られる陽極酸化皮膜であり、前記第2の陽極酸化皮膜が交直重畳電解を印加して得られる陽極酸化皮膜である請求項4に記載の表面被覆アルミニウム部材。
- 請求項1~5のいずれか一項に記載の表面被覆アルミニウム部材を備え、
前記表面被覆アルミニウム部材を内燃機関のエンジンの燃焼室を形成する部品又は内燃機関用ピストンの一部に適用している内燃機関用ピストン。 - アルミニウム部材に交直重畳電解を印加することにより、第2の陽極酸化皮膜を形成する工程と、
前記アルミニウム部材に直流電解を印加することにより、第1の陽極酸化皮膜を形成する工程と、
前記第2の陽極酸化皮膜の表面に、所定の成膜法を用いて、前記第1の陽極酸化皮膜及び前記第2の陽極酸化皮膜よりも熱伝導率が高い皮膜を形成する工程と、
を備えるアルミニウム部材の表面被覆方法。 - 前記アルミニウム部材の表面に前記第1の陽極酸化皮膜を形成し、前記第1の陽極酸化皮膜の表面に前記第2の陽極酸化皮膜を形成する請求項7に記載のアルミニウム部材の表面被覆方法。
- 前記第1の陽極酸化皮膜を形成する工程と前記第2の陽極酸化皮膜を形成する工程とを、同一の処理浴を用いて行う請求項7又は8に記載のアルミニウム部材の表面被覆方法。
- 前記第1の陽極酸化皮膜を形成する工程と前記第2の陽極酸化皮膜を形成する工程の後に、前記工程を繰り返す工程を更に備え、
前記繰り返す工程の後に、前記熱伝導率が高い被膜を形成する工程を行う請求項7~9の何れか一項に記載のアルミニウム部材の表面被覆方法。
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