JP5614538B2 - Method for forming composite plating film - Google Patents

Description

  The present invention relates to a method for forming a composite plating film in which diamond fine particles and fluororesin fine particles are dispersed and co-deposited.

  In general, composite plating is performed by immersing an object to be plated in a state in which insoluble fine particles are uniformly dispersed in a plating bath used in a normal plating process. On the surface of the object to be plated, a metal film is chemically deposited and fine particles are co-deposited in the metal film to form a composite plating film in which the fine particles are dispersed in the metal matrix.

  Fine particles used in such composite plating include oxides (silicon dioxide, alumina, etc.), carbides (silicon carbide, chromium carbide, etc.), fluororesins, nylon, polyethylene, graphite, fluorinated graphite, molybdenum disulfide, boron nitride, etc. Depending on the characteristics of the fine particles, the composite plating film can be provided with functions such as hardness, wear resistance, lubricity, water repellency, and non-adhesiveness.

  For example, Patent Document 1 describes that a surface smoothing layer in which PTFE particles are dispersed in nickel is formed on the surface of a metal substrate, and a fluorine-based film is formed on the surface smoothing layer. The point that water repellency and heat resistance are imparted by the formation of such a film is described.

  In recent years, diamond fine particles have attracted attention as fine particles dispersed in the composite plating film. For example, Patent Documents 2 and 3 exemplify diamond together with PTFE as fine particles used for Ni-P plating.

  Nanodiamond, which is a fine diamond particle, is artificially produced by the impact compression method or the static pressure method, and the form obtained by the production method is different. Different types of nanodiamond such as polycrystal, single crystal, and cluster are known. Yes. Polycrystalline nanodiamond has a spherical structure and is therefore considered a material suitable for a sliding surface between solids.

  The polycrystalline nanodiamond is a sintered body having a primary particle size of 5 to 20 nm, but it is difficult to stably exist as a primary particle, and a large aggregate of about 50 to 7,500 nm It exists. Therefore, such nanodiamond has been used by being dispersed in a liquid when used industrially.

  However, as fine particles to be dispersed, carbon-based materials such as nanodiamonds, fine particles such as fluorine-based resins, ceramics, etc. are used for plating treatment, which is strong in water repellency and hydrophobicity and can be dispersed in a metal plating bath as it is. Therefore, it is very difficult to disperse and eutect the fine particles uniformly in the plating film.

  Conventionally, a method of dispersing fine particles in a plating bath using a surfactant as a dispersion aid has been used. As surfactants used as dispersion aids, there are known cationic surfactants, amphoteric surfactants and nonionic surfactants that exhibit a cationic property corresponding to the pH of the plating bath. Further, as a method not using a surfactant, a method of stirring with a gas in a plating bath in which fine particles are suspended is known.

JP 2007-327135 A Japanese Patent Laid-Open No. 5-171454 JP-A-2005-256170

  The polycrystalline nanodiamond obtained by the impact compression method has primary particles as small as 5 to 20 nm, but the surface of the nanodiamond is fused with non-graphitic, graphite film, etc. It is manufactured and sold as a secondary or tertiary aggregate of 7,500 nm.

  When commercially available nanodiamonds are dispersed in the plating solution, even if a surfactant is added, the particles are likely to aggregate, and the aggregated particles are precipitated, so that it is very difficult to obtain a stable dispersion. There was a problem that nanodiamonds aggregated (segregated) on the surface of the plating film that was plated in a state where nanodiamonds were not stably dispersed.

  In order to deal with such problems, it has been proposed to crush nanodiamond aggregates by an ultrasonic dispersion method, a bead mill dispersion method, or the like. By using such a dispersion method, a dispersion liquid having an average particle diameter of nano-diamonds of 10 nm to several hundreds nm can be obtained. Will occur.

  Moreover, in the conventional composite plating treatment using nanodiamonds, nanodiamonds having an average particle size of several nanometers to several hundred nanometers were dispersed in a plating solution to obtain a composite plating film. Since the concentration of nanodiamond to be dispersed was dilute, the content of nanodiamond co-deposited in the composite plating film was about several percent. Therefore, a composite plating film that sufficiently exhibits the characteristics of nanodiamonds cannot be obtained.

  Accordingly, an object of the present invention is to provide a method for forming a composite plating film in which diamond fine particles and fluororesin fine particles are uniformly dispersed and co-deposited.

  The method for forming a composite plating film according to the present invention comprises a method of forming diamond fine particles having an average particle size of 10 nm to 300 nm, fluororesin fine particles having an average particle size of 100 nm to 300 nm and a surfactant into which a hydrophilic polymer or an ionic functional group has been introduced. The composite plating solution added to the plating solution is brought into contact with the substrate surface to form a composite plating film in which diamond fine particles and fluororesin fine particles are uniformly dispersed in a metal matrix. Further, the surfactant is a cationic surfactant, an amphoteric surfactant or a nonionic surfactant that exhibits a cationic property at the pH of the metal plating solution. Further, the amount of the surfactant added in the composite plating solution is 0.5 g / liter to 2 g / liter of the surfactant for dispersing the diamond fine particles and 0.1 g of the surfactant for dispersing the fluororesin fine particles. / Liter to 0.3 g / liter. Furthermore, the metal plating solution contains one or more metal ions selected from the group consisting of nickel ions, cobalt ions, copper ions, gold ions, iron ions, palladium ions, platinum ions, tin ions and rhodium ions. It is characterized by including. Furthermore, the fluororesin fine particles include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyvinylidene fluoride ( PVDF), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and at least one selected from the group consisting of ethylene-tetrafluoroethylene copolymer (ETFE).

  The present invention has the above-described configuration, so that a composite plating solution in which diamond fine particles and fluororesin fine particles are stably dispersed in a metal plating solution is brought into contact with the substrate surface, and the diamond fine particles and fluorine A composite plating film in which resin fine particles are uniformly dispersed in a metal matrix can be formed.

  Thus, the sliding material on which the composite plating film is formed has excellent characteristics such as high wear resistance, low friction, and low attacking property on the mating material. Therefore, the initial familiarity at the start of sliding is improved by the fluororesin fine particles having an average particle diameter of 100 nm to 300 nm, and the problem of sudden seizure can be solved. Further, at the stage of transition to steady-state wear after the familiarization process is finished, wear of the composite plating film is prevented by diamond fine particles having an average particle diameter of 10 nm to 300 nm, and the life of the sliding material can be extended. .

It is the enlarged photograph which image | photographed the dispersion state of the microparticles | fine-particles on the surface of a composite plating film with the electron microscope (SEM). It is explanatory drawing regarding the implementation method of a test. It is a graph which shows the average friction coefficient regarding an Example and a comparative example. It is a graph which shows the wear scar width regarding an Example and a comparative example, and the specific wear amount of the other party material.

  Although there is no restriction | limiting in particular as a metal plating solution used in the formation method of the composite plating film concerning this invention, Nickel ion, cobalt ion, copper ion, gold ion, iron ion, palladium ion, platinum ion, tin ion, and rhodium ion One containing one or two or more metal ions selected from the group consisting of the above can be used, and particularly preferred is a metal plating solution containing nickel ions. Metal ions can be used in the form of water-soluble metal salts such as sulfates and chlorides, and the compounding of metal ions in the composite plating solution is 0.02 mol / liter to 0.2 mol / liter, preferably Is 0.05 mol / liter to 0.1 mol / liter.

  As the diamond fine particles used in the present invention, excellent sliding properties can be obtained when an average particle diameter of 1 nm to 1000 nm, preferably 10 nm to 1000 nm, particularly 10 nm to 300 nm is used. As such diamond fine particles, those of a polycrystalline type, a single crystal type, and a cluster type that are usually available can be used.

  In order to uniformly disperse the diamond fine particles in the metal plating solution, a hydrophilic polymer or an ionic functional group is introduced on the surface of the diamond particle. For example, in the case of a cationic functional group, protons are easily generated in an acidic region. An amino group, a thiol group, a hydroxyl group, a phosphine group and the like which are bonded to each other to form onium. Among these, an amino group that is most likely to form onium is preferable, and an amidine skeleton having two amino groups is more preferable.

  Therefore, the azo radical initiator to be reacted with the diamond fine particles preferably has an amidine skeleton. Amidine may be hydrochloride or cyclic. Specifically, 2,2′-azobis (2-methyl-N-phenylpropionamidine) dihydrochloride, 2,2′-azobis [N- (4-chlorophenyl) -2-methylpropionamidine] dihydrochloride Salt, 2,2′-azobis [N- (4-hydroxyphenyl) -2-methylpropionamidine] dihydrochloride, 2,2′-azobis [2-methyl-N- (phenylmethyl) propionamidine] dihydrochloride Salt, 2,2′-azobis [2-methyl-N- (2-propenyl) propionamidine] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis [N- (2-hydroxyethyl) -2-methylpropionamidine] dihydrochloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane Dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (4,5,6,7-tetrahydro-1H- 1,3-diazepin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2 '-Azobis [2- (5-hydroxy-3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2,2'-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] and the like. These are commercially available and can be easily obtained.

  In order to produce an aqueous dispersion in which diamond fine particles having ionic functional groups introduced therein are dispersed, the diamond fine particles are reacted with an azo radical initiator in an aqueous solvent. What is necessary is just to mix a diamond fine particle and an azo radical initiator in an aqueous solvent, and to start radical reaction by heating or light irradiation. In the case of heating, it is sufficient to heat to 50 ° C. or more, preferably 65 to 75 ° C., and the reaction is completed in several tens of hours. The rate of reaction depends on the amount of the azo radical initiator, and it is preferable to use an azo initiator in an amount of 0.1 to 5 times the weight of the diamond fine particles. If the amount of the azo initiator exceeds 5 times, the amount of organic matter introduced into the diamond fine particles will not increase, and if it is less than 0.1 times the amount of organic matter introduced into the diamond fine particles is small and the dispersibility becomes insufficient. .

  The aqueous solvent is water or a mixture of water and a water-soluble solvent, and usually water may be used. When the azo radical initiator to be used does not dissolve in water, a water-soluble solvent can be appropriately mixed and used. Examples of the water-soluble solvent include alcohols such as methanol and ethanol, aliphatic polyols such as ethylene glycol, glycerin and low molecular weight polyethylene glycol, nitriles such as acetonitrile, N, N-dimethylformamide, N, N-dimethylacetamide. Amides such as N-methyl-2-pyrrolidone, sulfur-containing solvents such as dimethyl sulfoxide, dimethyl sulfone and sulfolane, and phosphorus-containing solvents such as hexamethylphosphoric triamide.

  The concentration of the diamond fine particles during the reaction is preferably 1 to 20% by weight, more preferably 5 to 10% by weight. When the concentration is higher than 20% by weight, the diamond fine particles aggregate, and the reaction between the aggregated diamond fine particles and the azo radical initiator becomes insufficient, making it difficult to introduce an ionic functional group. If it is less than 1% by weight, the concentration of diamond fine particles in the composite plating solution is lowered and the amount of diamond fine particles in the composite plating film is reduced.

  The aqueous dispersion of diamond fine particles obtained by the above method can be added to the metal plating solution as it is, but a treatment such as separation and washing is performed to remove unreacted azo radical initiators and excess salts. Preferably it is done. As the separation method, methods such as filtration and centrifugation are used. As the filter medium, a membrane filter of about 0.1 μm is preferable because of little separation loss. In the case of washing, demineralized water is usually used, but a water-soluble organic solvent may be appropriately mixed so that the remaining organic substances such as the azo radical initiator can be easily removed. Moreover, in order to adjust pH, various salts can also be dissolved and used.

  In order to suppress reaggregation of diamond fine particles in the aqueous dispersion, it is preferable to adjust the aqueous dispersion to a pH in the range of 3 to 8. In the case of a strong acid or base liquid, the charge on the surface of the diamond fine particles is neutralized by a counter ion, and dispersion stability due to charge repulsion is inhibited. Examples of the pH adjuster include monohydrogen phosphate, dihydrogen phosphate, hydrogen carbonate, carbonate, hydroxide, and the like, and alkali metal salts, alkaline earth metal salts, ammonium salts, and the like are used. You can also.

  In addition, by using a hydrophilic polymer as a functional group to be introduced on the surface of the diamond fine particles, the steric repulsion force due to the polymer chain on the surface of the fine particles can be increased, and the diamond fine particles can be stably dispersed.

In this case, both ends of the azo radical initiator can be converted from a hydroxyl group to a Cl (chlorine) end, and then a polymer chain can be imparted to the resulting compound. For example, a polyethylene glycol (PEG) residue, a polydimethylsiloxane (PDMS) residue, etc. are mentioned. The conversion from a hydroxyl group to a Cl terminal can be widely applied to known reaction conditions for acid chloride reaction. The subsequent reaction with the polymer is a general dehydrochlorination reaction, and it is usually advantageous to carry out the reaction in the presence of a basic compound. Here, as the PEG residue, specifically,
_{- (CH 2 CH 2 O)} n - (n is about 4 or more, preferably about 10 or more integer)
Is mentioned. PDMS residues include
_{- [Si (CH 3) 2} -O] m - (m is about 3 or more, preferably 40 or more integer)
(See JP 2006-219591 A).

  In addition, diamond fine particles are surface treated under dry conditions with an amino group-containing silane coupling agent or amino group-containing silicone oil to introduce amino groups on the surface, and Michael addition of methyl acrylate is added to the introduced amino groups. It is also possible to form a polyamine dendrimer on the surface of the diamond fine particles by repeating the reaction and terminal amination with diamine by repeating under dry conditions (see JP 2001-106940 A).

  Even if the diamond fine particles introduced with the hydrophilic polymer or ionic functional group described above are added to the metal plating solution as they are, they are affected by the strong ionic strength of electrolyte ions such as nickel ions in the metal plating solution. The electrostatic repulsive force acting between the fine particles is canceled out, causing aggregation and precipitation.

  Therefore, it is preferable to add a surfactant as a dispersant in order to suppress such aggregation and precipitation of the diamond fine particles and stably disperse the diamond fine particles in the metal plating solution. Examples of the surfactant to be added include cationic and amphoteric surfactants or nonionic surfactants that are cationic at the pH of the plating bath used.

  The surfactant used as the dispersant is preferably a homopolymer or copolymer surfactant having a molecular weight of 30,000 to 200,000. When the molecular weight is larger than 200,000, it causes cross-linking between diamond fine particles, and acts as an aggregating agent rather than a dispersing agent. On the other hand, if the molecular weight is smaller than 30,000, desorption from the diamond fine particles is likely to occur even if the adsorption rate is high, and the effect as a dispersing agent becomes small.

  For example, in the case of a cationic surfactant, alkylbenzene sulfonate, dialkyldimethylammonium salt, and the like may be selected as appropriate depending on the ionic functional group introduced on the surface of the diamond fine particles. As an alkyl group used here, it is a C1-C6 integer, such as methyl, ethyl, propyl, butyl, pentyl, hexyl.

  In the case of diamond fine particles into which a hydrophilic polymer has been introduced, it is preferable to use a nonionic surfactant. For example, in the case of PEG, polyethylene glycol mono-4-octylphenyl ether and alkylphenol surfactants can be used.

    Examples of the fluororesin fine particles used in the present invention include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and polyvinylidene. Fluoride (PVDF), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and ethylene-tetrafluoroethylene copolymer (ETFE) are exemplified, and fine particles made of PTFE are particularly preferable. When the fluororesin particles having an average particle diameter of 100 to 1000 nm, particularly an average particle diameter of 100 nm to 300 nm are used, excellent sliding characteristics can be obtained.

  Fluororesin represented by PTFE is strong in water repellency and hydrophobicity and cannot be dispersed in the metal plating solution as it is, so it is difficult to uniformly disperse the fluororesin fine particles in the plating film. is there. Therefore, it is made to disperse | distribute in a metal plating solution by using surfactant as a dispersing agent.

  Examples of the dispersing agent for dispersing the fluororesin fine particles such as PTFE in the metal plating solution include a cationic surfactant, an amphoteric surfactant or a nonionic surfactant exhibiting a cationic property at the pH of the metal plating solution used. Can be mentioned.

  For example, perfluoropolyether having a carboxyl or sulfone end group salified with an alkali or alkaline earth metal or an anionic fluorinated surfactant having a perfluorocarbon structure, a cationic fluorinated surfactant such as perfluoroalkyl 4 Examples include quaternary ammonium salts, long chain (C8 to C18) alkyltrimethylammonium salts, and dimethylalkyllaurylbetaines. Furthermore, nonionic surfactants such as perfluoroalkyl polyoxyethylene ethanol and polyoxyethylene nonylphenyl ether may be added within a range not impairing the effects of the present invention, and may be mixed and used.

  When electroless composite plating is performed, it is necessary to pay attention to various problems caused by the added surfactant. For example, it is necessary to pay attention to problems such as striped unevenness, unplated portions, and eutectoid unevenness in the obtained composite plating film. In order to avoid such adverse effects due to the surfactant, the amount of the surfactant to be added is adjusted. However, if the amount added is excessively suppressed, the dispersion stability of the fine particles is reduced, and aggregation / precipitation occurs. When the amount is excessive, there arises a problem that a sufficient eutectoid amount of fine particles cannot be obtained. And the external appearance of the formed plating film will be in the rough state, and a favorable external appearance will not be obtained.

  Even when the above-mentioned diamond fine particles and fluororesin fine particles are dispersed in the metal plating solution, it is necessary to pay attention to the addition amount of the surfactant. Therefore, the addition amount of the surfactant in the composite plating solution is 0.5 g / liter to 2 g / liter of the surfactant for dispersing the diamond fine particles, and 0.1 g / surfactant for dispersing the fluororesin fine particles. It is preferable to set it as liter-0.3 g / liter. By setting the addition amount of the surfactant in this way, the diamond fine particles and the fluororesin fine particles can be kept in a stable dispersed state at the same time, and both fine particles can be uniformly distributed in the composite plating film formed in the composite plating process. Can be dispersed and co-deposited.

  The composite plating solution used in the present invention contains metal ions, water-insoluble fine particles, a complexing agent, and a reducing agent as essential components in addition to the above surfactant.

  Complexing agents include carboxylic acids such as citric acid, malic acid, EDTA, malonic acid, phthalic acid, maleic acid, glutaric acid, lactic acid, succinic acid, adipic acid, acetic acid, and their water-soluble salts, oxycarboxylic acids, and the like. These water-soluble salts can be used alone or in combination. The total compounding amount of the complexing agent is preferably 0.05 mol / liter to 2 mol / liter, particularly preferably 0.1 mol / liter to 1.1 mol / liter.

  As the reducing agent, hypophosphite such as sodium hypophosphite is used, and the amount of the reducing agent in the composite plating solution is not particularly limited, but is usually 0.05 mol / It is preferable to set it to liter-0.5 mol / liter, especially 0.15 mol / liter-0.3 mol / liter.

  The blending amount of diamond fine particles and fluororesin fine particles in the composite plating solution is 100 g / liter or less in total concentration, more preferably 0.1 g / liter to 100 g / liter, and further preferably 0.1 g / liter to 20 g / liter. Preferably there is.

  The pH of the composite plating solution of the present invention is preferably weakly acidic, specifically, pH 4 to pH 6, preferably pH 4.2 to pH 5.5, more preferably pH 4.5 to pH 5.2. preferable. For pH adjustment, an acid such as sulfuric acid or hydrochloric acid or an alkali such as sodium hydroxide can be added.

  The method for forming a composite plating film according to the present invention is preferably performed by electroless plating treatment, and the object to be plated, which is a base material, is immersed in a plating bath storing the composite plating solution, and the composite plating is applied to the object to be plated. What is necessary is just to perform an electroless-plating process by making a liquid contact.

  Specifically, the object to be plated is immersed in a composite plating solution in which diamond fine particles and PTFE fine particles are uniformly dispersed, and the bath temperature is preferably set to 70 ° C. to 95 ° C., more preferably 80 ° C. to 90 ° C. If necessary, the composite plating solution is agitated or rocked to form a composite plating film in which diamond particles and PTFE particles are uniformly dispersed and co-deposited in the metal matrix. To do.

  The material to be plated is not limited, and any material can be used as long as it can be electrolessly plated. Examples thereof include metal materials, plastic materials whose surfaces are made conductive, ceramic materials, and the like. .

  Moreover, although the film thickness of a composite plating film is suitably selected according to the use purpose etc. of a plating product, it should just normally be 1 micrometer-30 micrometers, and it is good to set the deposition rate of a film to 5 micrometer / hour-20 micrometers / hour.

  The composite plating film formed on the sliding material preferably has a high wear resistance if it contains 0.1 volume% to 15 volume% diamond fine particles and 1 volume% to 30 volume% fluororesin particles. It has excellent properties such as low friction and low attack on the mating material.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

<Example 1>
The composite plating solution shown below was prepared, and the steel plate and the stainless plate were subjected to electroless composite plating treatment.
[Liquid composition (basic bath composition)]
Nickel sulfate heptahydrate 0.07 mol / liter Sodium hypophosphite monohydrate 0.22 mol / liter Malic acid 0.10 mol / liter Malonic acid 0.30 mol / liter Adipic acid 0.85 mol / Liter stabilizer Trace amount poly (diallyldimethylammonium chloride) 1g / liter (dispersant for grafted diamond fine particles)
Perfluoroalkyl quaternary ammonium iodide 150 mg / liter (PTFE dispersant)
Grafted diamond fine particles (average particle size 50 nm) 2.0 g / liter (SCM Fine Diamond manufactured by Sumiishi Materials)
PTFE fine particles (average particle size 200 nm) 0.2 g / liter (MP1100 manufactured by DuPont)
[Plating conditions]
Composite plating solution pH = 4.9
Bath temperature: 90 ° C
Stirring: Slow plating time: 60 minutes

  As a test piece, carbon steel (SK105) was used which was formed into an elongated cylindrical pin shape having a diameter of 8 mm and a length of 25 mm, and the tip surface to be contacted was formed into a curved shape having a curvature radius of 18 mm. On the surface of the tip portion including the tip surface of the test piece, a metal film (film thickness: 10 μm) made of Ni—P is formed as an intermediate layer B in advance by electroless plating, and the above-described composite is formed on the metal film. Plating treatment was performed with a plating solution to form a composite plating film (film thickness 10 μm) in which diamond fine particles and PTFE fine particles were uniformly dispersed and co-deposited. In this case, the composite plating film formed by the plating treatment had a diamond fine particle content of about 5% by volume and a PTFE fine particle content of about 5% by volume.

  The enlarged photograph which image | photographed the dispersed state of the microparticles | fine-particles on the surface of the formed composite plating film with the scanning electron microscope (SEM) is shown in FIG. In the enlarged photograph, large black circles are PTFE fine particles, and small black circles are diamond fine particles. Looking at the distribution of these fine particles, it can be seen that they are uniformly dispersed and eutectoid.

<Example 2>
In Example 1, 0.1 g of PTFE fine particles were added to 1 g of diamond fine particles. In Example 2, 0.05 g of PTFE fine particles were added to 1 g of diamond fine particles, and composite plating was performed in the same manner as in Example 1. A film was formed.

<Comparative example>
What prepared the following four types of films on the front end surface of the base material having the same shape as the above-described test piece was prepared.
(Comparative Example 1)
Hard chromium film (film thickness 10μm) formed by electrolytic plating
(Comparative Example 2)
Ni-P metal film (film thickness 10μm) formed by electroless plating
(Comparative Example 3)
Of the above-described plating solution composition, a composite plating film in which only diamond fine particles formed by electroless plating using a composite plating solution to which PTFE fine particles are not added is uniformly dispersed (film thickness: 10 μm)
(Comparative Example 4)
Of the above-described plating solution composition, a composite plating film (thickness 10 μm) in which only PTFE fine particles formed by electroless plating using a composite plating solution to which diamond fine particles are not added is uniformly dispersed

<Reciprocating friction and wear test>
The sliding characteristics of the formed composite plating film were evaluated by a reciprocating frictional wear test. A reciprocating friction and wear tester (RFT-070 manufactured by Tapy Engineering Co., Ltd.) was used for the test.

  FIG. 2 is an explanatory diagram relating to a test execution method. The tip of the pin-shaped test piece 2 is brought into contact with the upper surface of the plate-like test stand 1 (material: gray cast iron (FC250)), and the test piece 2 is held vertically with respect to the test stand 1. Then, in a state where the test load L is applied to the test piece 2, the test table 1 is reciprocated linearly in the direction along the upper surface (arrow direction) to perform the test. Lubricating oil is always supplied from the nozzle 3 to the contact portion of the tip of the test piece 2 with the test table 1. Multipurpose general-purpose lubricating oil tetra oil 2 (manufactured by Showa Shell Sekiyu KK) for machine tools was used as the lubricating oil.

In the test, a running-in operation (starting reciprocating motion at a rotational speed of 200 rpm (sliding speed of 0.3 m / s) in a state where a test load of 19.6 N was applied to the test piece before starting the test) was repeated 400 times ( After about 2 minutes, the test was started under the following conditions.
Load 98N
Sliding speed 1m / s
Stroke 50mm
Number of reciprocations 36,000 times Sliding distance 3.6 km (Number of reciprocations: 36,000 times)
Atmosphere Oil lubrication (Tetra oil 2,2.1 mm ² / s, 40 ° C)
Mating material FC250 (Ra = 0.02μm or less)
Room temperature 22 ℃ ~ 23 ℃

  The frictional force applied to the test piece is detected by a load cell arranged at the test piece mounting portion, amplified by a dynamic strain meter, and stored in a PC (personal computer) via an AD converter. The coefficient of friction was a value obtained by dividing the friction force by the test load.

  For the average friction coefficient, average the average value of the friction coefficient of 20 times (about 2 seconds) before and after the time when the number of reciprocations reached 1,000 times from the start of sliding (about 3 minutes after the start of sliding). The friction coefficient was used.

  For the wear evaluation of the pin-shaped test piece, the maximum width in the direction perpendicular to the sliding direction of the wear mark formed in the sliding direction of the wear surface of the test piece is measured using a laser microscope (VK8700 manufactured by Keyence Corporation). The measured value was defined as the wear scar width (unit: mm).

For the amount of wear of the mating material (in this example, a plate-shaped test stand), the cross-sectional shape of the wear scar was measured at five locations at right angles to the sliding direction using a two-dimensional stylus type roughness meter, and then sliding was performed in advance. A wear cross-sectional area was obtained by fitting the surface shape measured on the previous virgin surface, and a value obtained by multiplying the average value of the wear cross-sectional areas at five locations and the stroke length of the reciprocating motion was calculated as the wear amount. The calculated wear amount was divided by the test load and the sliding distance to calculate the specific wear amount of the counterpart material (unit: × 10 ⁻⁸ mm ³ / Nm).

  FIG. 3 is a graph showing the average friction coefficient regarding the example and the comparative example, and FIG. 4 is a graph showing the wear scar width and the specific wear amount of the counterpart material regarding the example and the comparative example.

  Compared with the comparative example, in the example, the average friction coefficient is lowered, and it can be seen that by uniformly dispersing and eutecting the diamond fine particles and PTFE fine particles, the friction becomes low in the initial familiarization process in the sliding operation. Therefore, the familiar operation at the start of sliding of the sliding material is improved, and the occurrence of sudden seizure or the like can be suppressed.

  Further, since the specific wear amount of the counterpart material is significantly reduced in the embodiment as compared with the comparative example, the low attacking property against the counterpart material is greatly improved, and the wear scar width is also comparative example 1 (hard chromium). Film) and Comparative Example 2 (Ni-P film), and the wear resistance is also improved. Therefore, when the sliding material shifts from the familiar operation to the wear stage, the wear of the composite plating film and the counterpart material can be reduced, and the life of the sliding material can be extended.

  The method of forming a composite plating film of the present invention can efficiently form a composite plating film on a very wide range of objects. For example, driving parts for precision equipment such as various sliding members of automobiles, cameras, watches, etc. It can be applied to a wide range of applications such as metal molds, metal masks in special printing technology, general household appliances such as irons, and special industrial blades and tools.

1 Test stand 2 Test piece 3 Nozzle

Claims (7)

  The surface of the substrate is a composite plating solution in which a hydrophilic polymer or ionic functional group-introduced diamond fine particles having an average particle size of 10 nm to 300 nm, fluororesin fine particles having an average particle size of 100 nm to 300 nm, and a surfactant are added to the metal plating solution. And forming a composite plating film in which diamond fine particles and fluororesin fine particles are uniformly dispersed in a metal matrix.   The formation method according to claim 1, wherein the surfactant is a cationic surfactant, an amphoteric surfactant or a nonionic surfactant that exhibits a cationic property at a pH of the metal plating solution.   The addition amount of the surfactant in the composite plating solution is such that the surfactant for dispersing the diamond fine particles is 0.5 g / liter to 2 g / liter and the surfactant for dispersing the fluororesin fine particles is 0. The forming method according to claim 1, wherein the forming method is 1 g / liter to 0.3 g / liter.   The metal plating solution contains one or more metal ions selected from the group consisting of nickel ions, cobalt ions, copper ions, gold ions, iron ions, palladium ions, platinum ions, tin ions and rhodium ions. The formation method according to any one of claims 1 to 3.   The fluororesin fine particles include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and polyvinylidene fluoride (PVDF). And at least one selected from the group consisting of ethylene-chlorotrifluoroethylene copolymer (ECTFE), and ethylene-tetrafluoroethylene copolymer (ETFE). The forming method described in 1.   A sliding material comprising a composite plating film formed by the forming method according to claim 1.   The sliding material according to claim 6, wherein the composite plating film contains 0.1% by volume to 15% by volume of the diamond fine particles and 1% by volume to 30% by volume of the fluororesin fine particles.