JPH0369987B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a masking method for applying a coating of a different material to the surface of a metal product (hereinafter referred to as the base material) by vapor deposition to protect areas where the coating is not desired when modifying the surface of the base material. It is. The method of coating the surface of metal products with metal carbides, nitrides, borides, pure metals, etc. by vapor deposition to functionally modify the surface of the base material is well known. Base materials for various purposes such as improving wear resistance, preventing galling, improving heat resistance, improving weather resistance and chemical resistance, adding conductivity to the surface, and creating reflective or anti-reflective films on the surface. Because it can easily modify the surface of
It is widely used in the production of drawing dies, mechanical parts, automobile parts, integrated circuits and transistors, storage batteries, decorations, etc. Vapor deposition is a process called Chemical Vapor Deposition (hereinafter abbreviated as CVD).
and Physical Vapor Deposition
(hereinafter abbreviated as PVD). CVD is a method of coating the surface of a substrate with a substance that matches the required properties by vapor deposition through a chemical reaction.An example of titanium carbide coating is a method that uses gaseous titanium tetrachloride (TiCI ₄ ) and methane. ,
A mixed gas of any hydrocarbon such as ethane and hydrogen is placed into a retort heated to 900-1200°C containing the base material to be deposited, and by contacting it for several hours, a reaction based on the following formula occurs and titanium carbide is deposited. is coated on the surface of the base material with a thickness of several μm to 15 μm. CH ₄ →C+2H ₂ TiCl ₄ +C+2H ₂ →TiC+4HCl or TiCl ₄ +2Fe+C→TiC+2FeCl _2In titanium carbide coating, when using a base material containing carbon, such as steel, the carbon in the steel also contributes to the formation of titanium carbide. Therefore, a better coating of titanium carbide can be obtained from steel with a higher carbon content. Examples of steel materials that normally contain 0.8% or more of carbon include high-speed tool steel (SKH), carbon tool steel (SK), and alloy tool steel (SKD), which are suitable materials for applying titanium carbide coatings. However, mechanical and structural carbon steel, stainless steel,
Titanium carbide coatings can also be applied to many base materials, including other steels such as stellite, other metals, and ceramics such as alumina.
In addition to the above-mentioned titanium carbide, substances that can be coated on the substrate by CVD include carbides such as chromium carbide, niobium carbide, silicon carbide, boron carbide, zirconium carbide, tungsten carbide, titanium nitride, boron nitride, tantalum nitride, etc. Nitride, carbonitride such as titanium carbonitride, silicide such as zirconium silicide, molybdenum silicide, tungsten silicide etc., silicon boride, titanium boride, zirconium boride, chromium boride Such as borides, alumina, beryllia, zirconia, chromium oxide, uranium oxide, etc.
Many are known, including oxides such as silicon oxide and iron oxide, metals such as silicon, tungsten, niobium, molybdenum, chromium, nickel, and tantalum, and heat-resistant alloys such as pyrolitic carbon. Used for layer coatings. On the other hand, PVD is further classified into vacuum evaporation method, sputtering method, ion plating method, plasma method, etc., but the process is 10 ^-6 ~
The material to be deposited, such as metal, is melted and evaporated in a vacuum of 10 ^-2 Torr using methods such as electron beam, radio frequency, Cranstar method, and plasma. For example, in the case of titanium carbide PVD, the evaporated titanium atoms and carbonization of acetylene, etc. By introducing hydrogen gas, titanium carbide is produced by the following reaction and coating is applied. 2Ti(g)＋C ₂ H ₂ (g) → 2TiC(s)＋H ₂ (g) The deposition temperature is 250 to 500℃, which is lower than that of CVD, and the coating is done by vapor deposition with almost the same type of material as CVD. It is possible to do so. Vapor deposition has the advantage of improving the various properties described above by coating the surface of the base material by vapor deposition as described above, but it is also used in machines, structural parts, plastic molds, punching punches, etc.
When vapor deposition is performed on a drawing die or the like, there are various problems as described below when coating the entire surface of the die. The following are just a few examples of the drawbacks that arise when the entire surface of a machine or structural component is coated by vapor deposition. For example, tools and parts that have a threaded part for attachment, such as a threaded punch, do not originally require coating with titanium carbide, but an appropriate masking method has not been developed. Conventionally, the entire surface including the threaded part had to be coated, and the coating reduced the dimensional accuracy of the threaded part. Furthermore, when coating the inner surface of a drawing die or the like to improve its wear resistance, the outer surface, which does not require coating, is also coated at the same time for the same reason. However, the outer surface often needs to be precisely finished by grinding for fitting, but if the outer surface is coated with titanium carbide, it may be necessary to grind it with an expensive diamond grindstone or grind it with hard titanium carbide. The layer had to be ground by spraying carborundum, etc., which required an expensive grindstone and a great deal of labor. When coating a base material by vapor deposition,
As a method to avoid coating parts that you do not want to apply as described above, when there are many base materials with simple shapes, for example, when coating gears, multiple gears are overlapped and vapor deposition is performed only on the tooth parts. However, since the base material generally has a plurality of shapes, such a method could not be applied. In view of the current situation, the present inventors have conducted intensive studies on masking methods for coating by vapor deposition, which are simple and easy to work with, and have identified a specific inorganic compound that can form a cured film. The present invention has been completed based on the discovery that a composition consisting of inorganic aggregates is extremely effective as a masking agent for coating by vapor deposition on the surface of metal products. That is, the present invention applies a composition consisting of a specific inorganic compound and a specific inorganic aggregate that forms a cured film to the parts of the base material that are not desired to be vapor-deposited to form a film, and then vapor-deposit the film onto the base material. The present invention relates to a masking method in vapor deposition, which is characterized by applying vapor deposition, and relates to a method in which vapor deposition is applied only to areas that require vapor deposition. The composition comprising a specific inorganic compound and a specific inorganic aggregate related to the present invention is used as a masking agent, but it can be applied easily without the need for complicated work or complicated processing, that is, like a paint. It exhibits its excellent masking ability by simply applying it to the required areas and curing it, completely preventing the coating from being deposited on areas other than the desired areas, and allowing it to be deposited only on the areas that require it. has. In addition, the masking agent film after the coating is completed can be easily removed by quenching or light hitting after coating, which is a feature in that the masking agent is easy to remove and has excellent workability. Examples of the inorganic compound constituting the masking agent in the present invention include water-soluble or water-dispersible silicates, phosphates, silica sol, and alumina sol that form a cured film. Specific examples of these include water-soluble alkali metal silicates such as lithium silicate, sodium silicate, potassium silicate, colloidal silica,
These include water-dispersible silica sol, alumina sol, such as colloidal alumina, and water-soluble phosphates, such as aluminum phosphate, magnesium phosphate, and calcium phosphate. The above-mentioned inorganic compound according to the present invention is in a liquid state before curing, but after being applied to a substrate, it hardens to form a film on the surface of the substrate by water evaporation or chemical reaction, and has the property of adhering to the substrate. The inorganic compounds used as constituent components of the masking agent in the present invention include two or more of these compounds alone.
A mixture of more than one type of compound may be used, and metal oxides such as zinc oxide or metals such as aluminum hydroxide may be used in order to appropriately adjust the activity of the compound and obtain a coating with high adhesion and few pinholes. A prepolymer is formed by partially reacting a compound such as a hydroxide, a fluoride such as calcium fluoride, or sodium silicofluoride, a borate, or a phosphate with one or more of the above-mentioned inorganic compounds. A so-called modified compound may also be used. In the present invention, a specific inorganic aggregate is used as a constituent component of the masking agent together with a specific water-soluble or water-dispersible inorganic compound that forms the cured film, thereby achieving excellent effects. . As the inorganic aggregate, alumina or silica is used alone or in combination in the present invention. The shape is not necessarily limited, and various shapes such as spherical, needle-like, fibrous, scale-like, and block-like shapes can be used. Further, it is desirable that the inorganic aggregate has no or low reactivity with the inorganic compound. This is because when highly reactive aggregates are used, they react with inorganic compounds at the same time as they are mixed, creating difficulties in coating work and causing problems such as hardening when stored as a single solution as a masking agent. This is because there are things. However, a method of mixing a highly reactive aggregate with an inorganic compound immediately before applying it to a base material (such as the so-called one-liquid, one-powder mixing type) may also be effective in some cases. Although the particle size and particle size distribution of the inorganic aggregate are not particularly limited, it is preferable to use one in the range of 0.001 μm to 1 mm.
More preferably, the aggregate has a weight average particle size in the range of 0.1 .mu.m to 100 .mu.m, whereby good results can be obtained. However, in the case of fibrous or acicular aggregate, even if the length exceeds this range, it can be used without any problem. It is most preferable for the particle size distribution to follow the Andreazen close-packed particle size curve, but good results can be obtained when q in the Andreazen close-packed particle size formula is in the range of 0.2 to 1. The mixing ratio of the inorganic compound and the aggregate is preferably 1 to 10,000 parts by weight, more preferably 10 to 1,000 parts by weight, per 100 parts of the aggregate. If the blending ratio of the inorganic compound is smaller than this range, the masking agent will not become slurry-like or base-like, which will inhibit wetting of the substrate during application. On the other hand, if it is too large, the effect of the aggregate cannot be expected, and when applied as a masking agent, foaming, pinholes, cracks, etc. occur, and complete prevention of vapor deposition cannot be expected. In addition to these, anti-settling agents, surfactants, pigments, inorganic fibers, viscosity modifiers, solvents, curing agents, etc. can be mixed in the masking agent of the present invention in appropriate combinations as required. The masking agent used in the present invention can take various forms, but forms such as slurry, suspension, and paste are generally preferred because they are suitable for coating work. Their viscosity varies depending on the application method, but their viscosity can be measured using a rotational viscometer at 25℃.
Approximately 50 to 500,000 cps is good, but in the case of application by spraying, etc., a low viscosity one is better, and in the case of brush painting, dipping, etc., a slightly higher viscosity one is better in terms of application workability. "Aron Ceramic" (registered trademark), which is commercially available from Toagosei Chemical Industry Co., Ltd., can be applied as an inorganic adhesive as a masking agent from the specific inorganic compound and inorganic aggregate used in the method of the present invention. I can do it. It is most effective for the thermal expansion (linear expansion coefficient) of the masking agent after curing to have a relative relationship with the linear expansion coefficient of the base material for good masking effects and removal of the masking agent after completion of coating by vapor deposition. ,
The difference in average linear expansion coefficient between the base material and the masking agent at 25 to 1000°C is within the range of (0.1 to 10) x 10 ^-6 cm/cm°C, more preferably (0.5 to 5) x 10 ^-6 cm/cm°C. It is desirable to enter. The coefficient of linear expansion of the masking agent can be changed or adjusted by appropriately selecting the type and amount of inorganic aggregate used. Next, the method of the present invention will be explained in detail. By coating the base material by vapor deposition, the above-mentioned masking agent is uniformly applied to the areas where the problem occurs using a brush, spatula, spray, or various coaters. If oil, rust, rust preventive agent, dust, etc. are attached to the base material, the adhesion of the masking agent will be reduced, so it is desirable to perform simple siding or degreasing in advance. Subsequently, curing conditions are set so that the masking agent forms a good coating film, and the masking agent is cured. Curing conditions vary depending on the type of inorganic compound and whether or not a curing agent is used, but heating is generally performed at room temperature or below 300°C, preferably at a temperature of 150°C or 300°C for 1 to 2 hours. A method in which the substrate is placed in a retort for vapor deposition after most of the solvent components such as water in the masking agent are removed is convenient for maintaining the degree of vacuum in the retort. In either method, rapid heating of the masking agent will cause foaming of the coating film and the generation of hoids due to the evaporation of solvent components such as water in the masking agent, reducing the masking ability, so the temperature should be gradually raised and the coating applied. It is desirable to cure the film. The masking agent of the present invention enables partial vapor deposition prevention during vapor deposition simply and at low cost. The present invention expands the effective application of vapor deposition and greatly improves the functionality, performance, and reliability of machines, structural elements, various tools, molds, and the like. The present invention will be further explained below with reference to Examples. Example 1 Alloy tool steel A sample of a round bar (10 mm × 100 mm ^L ) of steel D11 class (SKD11) was steam-cleaned with trichlorethylene, and then washed with Aron Ceramic HT (manufactured by Toagosei Kagaku Kogyo Co., Ltd., main component: silica). System inorganic compound/modified water-soluble silicate, solid content 73wt%, viscosity at 25℃ 100000cps, average coefficient of linear expansion from 25 to 600℃ 13×10 ^-6
1/2 of the sample was coated by dipping into a medium (cm/cm°C). Leave at room temperature for about 10 minutes, then at 80℃ for 60 minutes, then
A masking agent paint was obtained by heating at 150°C for 60 minutes.
The film thickness of the masking agent after curing was approximately 100 μm. Thereafter, the sample was coated with titanium carbide by CVD. The gas used was titanium tetrachloride, hydrogen, and methane at 1000℃ for 5 hours to obtain a titanium carbide coating thickness of 6μm.
CVD treatment was performed. A part of the sample was cut out using a diamond grindstone, and the surface of the SKD11 sample with and without masking agent was observed using a scanning electron microscope. A titanium carbide coating layer of about 6 μm was formed on the surface of the sample in the area where no masking agent was applied, and no titanium carbide coating layer was observed in the area where the masking agent was applied. The micro-Vickers hardness of the sample surface was Hv2600 for the titanium carbide coated part, whereas the masking agent coated part was Hv298, and the masking effect was obvious. Examples 2 to 3 Round bars (10 mm × 100 mm ^L ) of cemented carbide (K10) and carbon tool steel (SK3) were degreased with 1,1,1,-trichloroethane and used as samples. As a masking agent, Aron Ceramic C (manufactured by Toagosei Kagaku Kogyo Co., Ltd., main components: silica-based inorganic compound/modified water-soluble silicate,
Solid content 71wt%, viscosity 70000cps at 25℃, 25
~600°C with an average linear expansion coefficient of 13×10 ^-6 cm/cm°C) was applied with a brush to 1/2 of the sample. After leaving it at room temperature for 30 minutes,
The coating was heated to 150°C at a heating rate of 100°C/hr, and further heated at 150°C for 1 hour to cure the coating film.
The film thickness of the masking agent after curing was 20 to 300 μm. Titanium carbide was deposited under the same conditions as in Example 1, and electron microscopic observation was performed in the same manner. K10
In the case of , a titanium carbide coating layer of approximately 10 μm thickness was observed in the vapor deposited area, and the surface hardness was Hv2900 in terms of microvits, whereas in the masking agent applied area, no titanium carbide coating layer was observed and the surface hardness was Hv1600. It was hot. Even in the case of SK3, a titanium carbide coating layer of approximately 24 μm was observed in the vapor deposited area, and the surface hardness was
Hv3800 is extremely high, whereas no titanium carbide coating layer is observed in the masking agent applied area.
The surface hardness was Hv210, and the masking effect was significant. Examples 4 to 7 Carbon tool steel (SK3) round bar (10mm × 100mm ^L )
was degreased with 1,1,1-trichloroethane and used as a sample, and a masking agent coating film was formed on a part of the sample using various masking agents shown in Table 1. After vapor deposition of titanium carbide by CVD in the same manner as in Example 1, the microvickers hardness of the vapor deposited area and the masking agent applied area are shown in Table 1.
Masking effects are observed for all masking agents.

[Table] *1 Example of composite salt of sodium and potassium 8-9 Round bar of alloy tool steel (SKD11) and chromium-molybdenum steel (SCM45) (10 mm × 100-150 mm ^L )
After degreasing with trichlorethylene, Aronceramic HT was applied to a part of the sample in the same manner as in Example 1 and cured by heating. The titanium nitride coating was formed using ion plating, a type of PVD method.
(Processing conditions: 300°C for 1 hour) On the part of SKD11 to which no masking agent was applied, a titanium nitride coating layer of approximately 1.4 μm was observed on the surface, and the surface hardness was Hv331.
In the area where the masking agent of SKD11 was applied, no coating layer was observed on the surface, and the hardness was Hv307.
It was hot. In the part of SCM415 where the masking agent was not applied, a coating layer of titanium nitride of approximately 1.2 μm can be seen on the surface, and the surface hardness is Hv216, whereas in the part where the masking agent was applied, no coating layer was observed on the surface. The hardness was Hv207. In the case of PVD, the titanium nitride coating layer is extremely thin, so although there is no significant difference in microvitkers hardness, there are clear differences in wear resistance, corrosion resistance, and decorativeness, and even in the case of PVD, there is no masking effect. Remarkable.

Claims (1)

[Claims] 1. Select from water-soluble or water-dispersible silicates, phosphates, silica sol, or alumina sol that forms a hardened film on areas where you do not want to coat the surface of metal products by vapor deposition. 1. A masking method in vapor deposition, which comprises applying a composition consisting of one or more inorganic compounds and an inorganic aggregate of alumina or silica to form a film, and then vapor-depositing the film on the surface.