JPH02232352A - Formation of combined thermal-sprayed film - Google Patents

Abstract

PURPOSE:To obtain the combined thermal-sprayed film which is improved in corrosion resistance, insulating characteristic, etc., by packing a synthetic resin by an electrochemical technique into the pores of the film formed by thermal spraying on a material to be treated and curing the resin. CONSTITUTION:The film constituted of metals, ceramics and cermet material is formed by thermal spraying on a material to be treated. The material with the thermally sprayed film is immersed in an electrolyte contg. a water soluble resin, such as acrylic resin or polyester resin or a high-polymer material in the form of emulsion. The above-mentioned electrolyte is impregnated into the pores of about 0.1 to 1mum size in the thermally sprayed film and in succession, the material is subjected to an energization treatment with the thermally sprayed film as an electrode. The above-mentioned resin or high-polymer material are insolubilized in the pores of the thermally sprayed film in this way and further, the thermally sprayed film is calcined by heating. As a result, the combined thermally sprayed film which is packed with the cured resin or high-polymer material in the pores and exhibits the characteristics intrinsic to the thermally sprayed film is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for forming a composite thermal spray coating in which the pores of the thermal spray coating are filled with a water-soluble resin or a polymeric substance.

This composite thermal spray coating is advantageously suitable for all products coated with a thermal spray coating, such as electrical resistors, which require corrosion resistance and wear resistance.

[Conventional technology]

In general, the thermal spraying method involves introducing a powder material into a high-temperature environment such as combustion gas or plasma spray, and then melting or softening the material and spraying it onto the object to be treated to form a film. For this reason, it is possible to use various metals, alloys, and ceramics such as carbides, oxides, nitrides, and borides as powder materials, and it occupies an important position as a surface modification technology. There is. However, since thermal sprayed coatings formed in the atmosphere are aggregates of fine particles that have been partially oxidized by oxygen in the air during thermal spraying, the particles do not fuse with each other, and they do not form a metallurgical bond with the object to be treated. It is in a state where it relies on mechanical bonding force. Therefore, the film is always dotted with pores of several percent to several percent, and the film has a disadvantage of relatively low adhesion. Furthermore, if there are many pores, the heat-insulating effect of the sprayed coating of oxide ceramics will be improved, but in a humid environment, the object to be treated will be corroded by moisture that has entered through the pores, significantly shortening the life of the coating. If the adhesion is low, it will easily peel off not only when corrosion occurs, but also when mechanical or thermal shock is applied to the coating, which causes a decrease in the reliability of the thermal spray coating.

As a countermeasure to this problem, there are methods to seal the pores by applying oil, paint, etc. to the surface of the thermal sprayed coating in the air or in a vacuum, and methods to eliminate the pores by heating or applying pressure to the thermal sprayed coating itself. Although many attempts have been made, the reality is that none of them have been sufficiently effective. In particular, pores cannot be eliminated in coatings sprayed with ceramics or thermeft material, which is a mixture of ceramics and metals, even if thermally treated after spraying, which is a major problem. In other words, even if a film is formed using a thermal spray material such as ceramics or cermet, which has excellent properties such as corrosion resistance, heat insulation, heat resistance, abrasion resistance, and electrical insulation resistance, it is free from water, acids, alkalis, and other substances. , MCI and NO. When used in a corrosive gas environment such as, these corrosive components penetrate into the interior through the pores of the film and corrode the base material (object to be treated). As a result, the sprayed coating will be damaged from its fundamentals.
The coating will peel off and will not be able to fully perform its function as a thermal spray coating. Therefore, methods of applying paints or polymeric materials onto the coating surface have been adopted, but conventional methods only block the pore entrances of the coating, and although they can somewhat slow down the infiltration rate of corrosive components, Even if the coating operation is performed in a vacuum, it cannot be a complete countermeasure because it does not prevent the infiltration.

[Problem to be solved by the invention]

The purpose of the present invention is to proactively utilize the above-mentioned characteristics of the porous thermal spray coating, fill the fine pores with synthetic resin using an electrochemical method, and then harden the filled resin to form the thermal spray coating. The purpose is to improve corrosion resistance, insulation resistance, etc., and to bring out the original characteristics of thermal spray coatings. [Means for Solving the Problems] The present inventors have discovered that the size of pores and even cracks in a thermal sprayed coating (a phenomenon that often occurs when ceramic particles are fused and solidified in a ceramic thermal sprayed coating) is approximately 1μ1 to 1B. Focusing on this, we use an electrolytic solution containing a filler to fill the pores, cracks, etc. using electrical energy.
The inventors have discovered that it is possible for the cells to move into the pores (hereinafter collectively referred to as stomata).

That is, in this invention, a coating is formed on an object to be treated by thermal spraying, and then the object to be treated with the sprayed coating is immersed in an electrolytic solution containing a water-soluble resin or a polymer substance in the form of an emulsion, so that the coating is deposited into the pores of the thermal sprayed coating. After impregnating the electrolytic solution, the thermal sprayed coating is subsequently subjected to an electrical current treatment using it as an electrode to make the water-soluble resin or emulsion-form polymer substance insoluble within the pores of the thermal sprayed coating, and then the thermal sprayed coating is heated and baked to close the pores. This is a method for forming a composite thermal sprayed coating, which is characterized by filling with a hardened resin or polymeric substance.

Additionally, thermal spray coatings are composed of metals, ceramics, and cermet materials, and water-soluble resins or emulsion-form polymer substances are either dissolved in water or suspended/dispersed in an emulsion state in an electrolyte. If it is positive, 《 is negatively charged, moves into the pores of the sprayed coating electrode by electrolysis, becomes insoluble, and is strongly solidified by subsequent heating and baking, such as epoxy resin, acrylic resin, polyester resin. Polybutadiene polymers and maleated oil-based polymers are each advantageously suited.

Now, if we use a water-soluble resin to which a parent wood group has been added as a filler for the pores and apply electricity to the sprayed coating as an electrode in an electrolytic solution containing this as a solute, the ionized water-soluble resin will flow into the pores and cracks together with water. Moving. As a result, the resin becomes insoluble due to the electrode reaction described below, and eventually fills the pores and cracks from the inside of the sprayed coating. Next, when the electrolytically treated thermally sprayed coating is heated to 150 to 190°C, hydrophilic groups are released and the resin becomes completely insoluble in water, and at the same time becomes hard.

By the above treatment, all the pores of the sprayed coating into which the electrolytic solution (moisture) can penetrate are filled with resin, and because of the electrolytic reaction, the resin is filled from the inside of the coating. Therefore, (1) Infiltration of corrosive components is avoided, and damage caused by corrosion caused by pores can be completely suppressed.

(2) In other words, the resulting thermal sprayed coating will have corrosion resistance regardless of the sprayed material, so the coating will exhibit the inherent performance of the thermal sprayed material, and the thermal sprayed material should be selected to match the intended use. .

Furthermore, (3) the resin filled in the pores of the film improves the breaking strength of the film itself.

(4) A portion of the resin filled in the pores also comes into contact with the base material (object to be treated) and adheres thereto, thus improving the adhesion of the entire thermal spray coating to the base material.

(5) Since water-soluble resins can be easily colored, thermal sprayed coatings treated according to the present invention exhibit extremely diverse colors, as opposed to conventional monotonous and subdued hues, thus improving their decorative value.

(6) Due to the above-mentioned effects, the life of the thermal spray coating is extended, and its industrial and commercial value is further improved.

Note that the general processing steps of the present invention are as follows.

■ Thermal spray coating formation (surface grinding/polishing as necessary) ■ Washing with water ■ Electrolytic treatment in an electrolytic bath (e.g. 25-30℃ for 30 seconds to 5 minutes) ■ Washing with water ■ Drying (e.g. hot air at 50-60℃) ■ Baking・Drying (for example, in an electric furnace at 150 to 190°C)
30 minutes) [Function] The water-soluble resin used in the present invention includes anionic resins (for example, polyester-based, acrylic-based, polybutadiene-based, etc.).
and cationic types (e.g., epoxy, acrylic, polybutadiene, etc.), and each type is manufactured by the following methods.

In other words, a carboxyl group (COOH) is introduced into the resin used as an anionic resin during electrolysis, and this is neutralized with an amine (-NHZ) or caustic potash (KOH) to form a salt, and then a hydroxyl group (-oH) is introduced into the resin. The ability to be dispersed in water-soluble or emulsion-like form is imparted by introducing

On the other hand, an amino group (-NH.) is introduced into the cationic resin, which is neutralized with an organic acid (oxalic acid) to form a salt, thereby making it water-soluble.

If the pH of the former aqueous solution is 8.0 to 9.5, it is weakly alkaline;
The pH of the latter resin is preferably 6.0 to 6.7 and is preferably used as a substantially neutral solution.

Further, when electrolyzing using an anionic resin, the object to be treated with the sprayed coating is used as an anode, while in the case of a cationic resin, the object to be treated is used as a cathode to conduct current.

Next, the pore sealing mechanism in the electrolytically sprayed coating will be described in detail.

As described above, the anion type water-soluble resin in the electrolyte is negatively charged, and the cation type is positively charged.

Regarding the former, when a porous sprayed coating is immersed in an electrolytic solution as an anode and a voltage is applied, the negatively charged resin moves to the sprayed coating on the anode. Here, the following reaction occurs.

■ At the anode, the pH decreases due to water electrolysis,
Along with this, the water-soluble resin becomes insoluble and adheres to the anode.

■ Polymerization of water-soluble resin occurs due to the action of electrical energy, which means that the resin becomes insoluble due to polymerization.
Adheres to the anode.

■ Water inside the membrane is discharged from the resin membrane that adheres at the initial stage of electrolysis due to the reactions of ■ and ■ above through electroosmosis and electrodialysis, promoting gelation reaction and reducing the adhesion of the resin to the anode. and the resin becomes stronger.

The above reaction occurs preferentially within the pores of the sprayed coating, and then extends throughout the coating, resulting in the pores being completely filled with resin. After solving il, pull this up,
After removing the moisture, the coating is dried with hot air and the adhering resin is fired in an electric furnace, so that the pores in the sprayed coating are completely sealed with the water-insoluble resin.

FIG. 1 schematically shows the state in which the pores of a porous thermal spray coating are electrochemically filled with a water-soluble resin according to the method of the present invention described above.

In the figure, 1 is a base material (object to be treated), 2 is a sprayed particle, 3 is a crack in the sprayed particle, and 4 is a resin.

Since thermal sprayed coatings are porous, simply by immersing them in an electrolytic solution containing a water-soluble resin, the electrolytic solution will penetrate into the pores of the coating. However, the water-soluble resin flows out of the pores together with the electrolytic solution that has entered the pores, and sealing of the pores cannot be achieved by simply pulling up the pores after dipping.

As mentioned above, by applying electricity to the porous sprayed coating as an electrode, the water-soluble resin becomes insoluble within the pores, which reaches the outside of the pores over time, and eventually covers the entire area of the sprayed coating. Only then will the pores be completely filled with resin. On the other hand, in conventional methods of applying synthetic resins and paints, they cannot penetrate into minute pores due to their viscosity and surface tension, so they simply block the entrances of the pores. Second
The figure shows this state. As the air in the pores expands and contracts due to temperature changes in the usage environment, the coating film is torn and moisture can easily enter. Therefore, the impregnation method of the present invention is Its lifespan is much shorter than that of an aged film. Note that 5 in the figure is a pore.

〔Example〕

After impregnating the pores of the sprayed coating formed under the conditions shown below with an epoxy-based water-soluble resin according to the method of the present invention,
The performance of the sprayed coating obtained by baking at 180° C. for 30 minutes was evaluated by conducting a corrosion test, an impact test, and measuring changes in the electrical resistance of the coating. The evaluation results are shown in Table 1.

Note l. Test base material: Structural steel plate (JIS 5541) width 50
x Length 100 x Thickness 5n 2. Test thermal spray material: Lower layer (undercoat) material Ni
-AI (20wt%) Upper layer (top coat) material AIzQi, AI201-TiOZ (2wt%) Cr
zO,,, Zr02IZrS+043. Thermal spray coating thickness:
Lower layer: 150 μm Upper layer: 150 μm However, samples with only lower N thermal spraying and upper layer thermal spraying were also used.

4. Thermal spraying method: Atmospheric plasma spraying method 5. Processing method for the film after thermal spraying: The pores of the film were filled by processing using an epoxy resin according to the method and process of the present invention described above. The processing conditions in this case are as follows.

Electrolyte composition: Water-soluble epoxy resin 30 g Water 900 yet Ethyl alcohol 100 ml Electrolytic conditions: Using a 200μ DC power supply, the thermal spray coating was used as a cathode and stainless steel was used as an anode, and the electrolyte was heated for 5 minutes at 27°C. The power was turned on.

At this time, the surface of the sprayed coating was also coated with a resin, and its thickness was 10 μm on average.

6. Processing method of comparative example: An epoxy resin layer was formed on the same thermal sprayed coating by a coating method in the air to a thickness of 10 μm.

7. Coating evaluation method (11 Salt spray test) Based on the salt spray test method of JIS Z 2371 (1976), the test was conducted for 500 hours continuously, and after standing for 24 hours, iron rust on the surface of the sprayed coating (from the base steel plate Evaluation was made based on the area where rust occurred.

(2) Wet-dry alternation test: Heated in an electric furnace at 120°C for 1 hour, then allowed to cool to 80°C.
After reaching this temperature, one cycle consisted of immersing the sample in tap water at 20°C for 1 hour, and evaluation was made based on the area of rust generated on the surface of the sprayed coating after 30 cycles.

(3) Impact test Using the test piece after the salt spray test, drop a steel ball weighing 500 g' from a height of 1 m onto the sprayed coating surface, and observe the occurrence of cracks in the coating each time the steel ball is dropped. Evaluated by.

(4) Electrical resistance test Using the test piece after the dry-wet alternating test,
After standing for a period of time, the electrical resistance value of the film was measured and evaluated by comparing it with the resistance value before the dry-wet alternation test.

Table 1 (1) The salt spray and wet/dry alternating tests were evaluated as follows based on the area of iron rust generated on the test piece.

○: No mackerel occurrence Δ: mackerel occurrence 1 to 5% ×: mackerel occurrence 5% or more (2) The impact test was evaluated by the number of impacts at which cracks occurred in the film.

O: No cracking occurred even after 10 impacts △: Cracking occurred after 5 to 9 impacts ×: Cracking occurred after less than 5 impacts Evaluation was based on the difference in values.

O: Change value 100 times or less △: Change value 1000 times or less It can be seen that it completely prevents tap water from entering the interior and completely suppresses corrosion of the base metal. This tendency was observed in the metal-only (Nll) and AIzOt-only (affected 2) specimens, which also withstood the impact of falling steel balls, showed strong adhesion, and showed little change in the electrical resistance value of the film. Excellent performance was confirmed.

On the other hand, in the comparative example in which the epoxy resin was applied in the atmosphere, iron rust was noticeable due to the infiltration of salt water and tap water. In addition, the adhesion of the sprayed coating to the base metal decreased due to the occurrence of rust, and the coating easily cracked when the steel ball fell. In the electrical resistance test as well, the film abrasion resistance value decreased significantly, and in all test pieces, the resistance value decreased to more than iooo times the resistance value before the test. This is thought to be due to the influence of moisture (salt) that has entered the pores.

Application I Thermal sprayed coatings formed using non-oxide ceramic ceramics and cermet, which is a mixture of non-oxide ceramics and metals, were investigated. The processing method, performance evaluation method, comparative example, etc. of the present invention are as follows. Test base material: Same as Example 1 2. Test thermal spray material: Lower layer (undercoat) material Ni
-AI (20) Upper N (top coat) material WC-Co (12), WC-Cr (20) -Ni (7
), Cr, C. , Cr,C,-Cr(20)-Ni(
7), WTiC-Ni (10) (All numbers in parentheses indicate wt%)3. Thermal spray coating thickness: Lower layer: 150 μm: Upper layer: 150 μm However, a coating with only the upper layer sprayed without the lower layer sprayed was also tested.

4. Thermal spraying method: Atmospheric plasma spraying method 5, treatment method of coating after thermal spraying and treatment method of comparative example: same as Example 16. Evaluation method: Table 2, which is the same as Example 1, shows the above test results.

As is clear from these results, it can be seen that the thermal sprayed coating treated according to the present invention has excellent performance.

Table 2? The first running ratio treated body (base material) is aluminum, and this is subjected to the treatment of the present invention in an electrolytic solution containing a maleated oil-based polymer that becomes an emulsion in the electrolytic solution to form a composite thermal sprayed coating. The obtained film was then investigated. The thermal spraying materials and evaluation test methods are as follows. In this example as well, an atmospheric thermal spray coating was used as a comparative example, and a maleated oil-based polymeric material was applied to the surface to a thickness of 10 μm. I used the one I made. The results of each evaluation are shown in Table 3.

Note 1. Test base material: Aluminum plate (JIS AIIOO
) Width 50 x Length 100 x Thickness 5l ■ 2. Test thermal spray material: Lower layer (undercoat) material Nt
-Cr (20wt%) Upper layer (Totsubu coat) material Aha3, AI■0.3-TiO■ (5ilIL%)
, CrzOs, ZrOz, ZrSi043. Thermal spray coating thickness: Lower layer i50 μm 2 Upper layer 150 μm The evaluation criteria for O and x in the table are in accordance with Table 1.

However, only lower layer thermal spraying and upper layer thermal spraying I also tried some things.

4. Thermal spray method Two-atmospheric plasma spray method 5. Film treatment method: Polyurethane water-soluble resin is treated by electrolytic method Electrolyte composition: Water-soluble polyester 40 g water
900 Ethyl alcohol
100 nti Electrolysis conditions: Using a 200V DC power supply, the sprayed coating was used as an anode, stainless steel was used as an anode, and electricity was applied for 5 minutes in an electrolytic solution at 27°C.

6. Film evaluation method (1) Salt spray test: Same as Example 1 (2) Impact test: Same as Example 1 (3) Electrical resistance test: The test piece after the salt spray test was immersed in tap water for 5 hours. After salt was eluted, the sample was pulled up and dried at 50°C for 3 hours, and its electrical resistance was measured and compared with the value before the test (salt spray test).

(4) Sand abrasion test: Using the test piece after the salt water test, 1 kg of alundum with a grain size of 100 to 300 μm was dropped from a height of 1 m through a steel pipe with a diameter of 25 mm onto the test piece held at an angle of 30”. This operation was repeated 20 times and the state of the film on the Alundum falling part was observed.

Table 3 fl+ The salt spray test was evaluated as follows based on the area of white rust and film blistering that occurred on the test piece. ○: No complaints Δ: Rust and blistering 1-5%×
: Occurrence of cracking and blistering of 5% or more (2) The impact test was evaluated by the number of impacts at which cracks occurred in the film.

○: No cracking occurs even after 10 impacts △: Cracking occurs after 5 to 9 impacts ×: Cracking occurs after less than 5 impacts (3) Electrical resistance test is evaluated by the difference in film resistance before and after the test. did.

O: Change value within 1/100 △: Change value 1/1000
(4) The sand abrasion test was evaluated from the difference in weight of the test piece before and after the test.

○: Change value within 1/1000 △: Change value 1/100
Range of 0 to 1/100 As can be seen from Table 3, since aluminum was used as the object to be treated in this example, the occurrence of red iron rust as in Example 12 was not observed, but white rust of aluminum was observed. Occur. In addition, since hydrogen gas is generated when white rust occurs, a so-called blistering phenomenon was observed in the maleated oil polymer film of the comparative example, and salt water easily penetrates into the interior through this part, destroying the entire thermal sprayed film. The process is recognized.

Therefore, when such a coating breakdown phenomenon occurs, various test properties such as collision, electrical resistance, and sand abrasion deteriorate, and the thermal spray coating cannot exhibit its original performance.

On the other hand, the coating treated according to the present invention completely fills the pores of the coating, so it is effective in preventing the infiltration of salt water and preventing the performance deterioration of the coating due to the corrosive action of salt water. Admitted.

A treatment according to the present invention was carried out using a water-soluble resin and a polymer material different from those in Examples 1 to 3 described above, and the effects thereof were investigated.

As a comparative example, the surface of the thermally sprayed coating was coated with a synthetic resin of the same quality by a coating method, as in the conventional case. The test items and evaluation method of test results are as follows.

Note 1. Test base material: Structural steel plate (5541) width 50 x length 10
0 x thickness 5l 2. Test thermal spray material: Lower layer (undercoat) material Ni
-Cr (20wt%) Upper layer (tonob coat) material AIzOi. ZrS+l:L 3. Thermal spray coating thickness: Lower layer 1.50 Atm Upper layer 150
μm 4. Thermal spray method Two-atmospheric plasma spray method 5. Synthetic resin used as solute: acrylic resin, polybutadiene polymer, polyester resin6. Film treatment: Same as Example 1, the thickness of the synthetic resin and polymer on the film surface was 10μI11) 7. Comparative Example: The above synthetic resin and polymer were coated to a thickness of 10 μffl by a coating method.Test items and evaluation criteria: Same as Example 1. Table 4 shows the test results. As is clear from these results, the acrylic resin treated according to the present invention. Thermal sprayed coatings impregnated with polybutadiene polymer and polyester resin showed excellent performance in various tests. On the other hand, the Comparative Example exhibited severe iron rust, was weak against impact, and was found to have extremely poor performance as a thermal spray coating, such as a significant decrease in the electrical abrasion resistance of the coating.

As is clear from the results of Examples 1 to 4 shown in Table 1, the evaluation criteria for ○ and )
It has the advantage that it can be applied to any film that has pores, regardless of the size of the film, and is not affected by the material of the base material of the object to be treated. In addition, the water-soluble resin used in the present invention and the polymer dispersed in the electrolyte in the form of an emulsion,
It is clear that the material is not limited to the synthetic resins and polymers of this example as long as it moves to the electrode by applying a direct current voltage, and we are confident that the range of application is extremely wide.

〔Effect of the invention〕

According to this invention, by electrochemically filling the pores of a thermally sprayed coating with a water-soluble resin or a polymeric substance, and then firing and solidifying this, 1.
It can prevent corrosion damage to the base material caused by corrosive components,
■A portion of the resin filled in the pores strongly adheres to the base material, improving the adhesion of the sprayed coating.■Additionally, a portion of the resin also exerts functions such as reinforcing the mutual bonding force of the sprayed particles. It is possible.

Therefore, it is possible to provide a coating that does not impair the chemical (corrosion resistance), mechanical (impact resistance, wear resistance, etc.) and electrical (insulation) properties of the thermal sprayed material itself, and significantly extends its life. be able to.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a thermal sprayed coating treated according to the present invention, and FIG. 2 is a sectional view of a thermal sprayed coating subjected to a conventional coating method. 1... Object to be treated (base material), 2... Thermal spray particles, 3...
- Cracks in thermal spray particles, 4... resin, 5... pores.

Claims (1)

[Claims] 1. A coating is formed on the object to be treated by thermal spraying, and then the object to be treated with the sprayed coating is immersed in an electrolytic solution containing a water-soluble resin or a polymeric substance in the form of an emulsion to remove the thermal sprayed coating. After impregnating the electrolyte into the pores, the thermal sprayed coating is subsequently subjected to an electrical current treatment using the electrode as an electrode to make the water-soluble resin or emulsion-form polymeric substance insoluble within the pores of the thermal sprayed coating.
A method for forming a composite thermal sprayed coating, characterized in that the thermal sprayed coating is then heated and baked to fill the pores with a hardened resin or polymeric substance. 2. The method for forming a composite thermal sprayed coating according to claim 1, wherein the thermal sprayed coating is composed of metal, ceramic, and cermet materials. 3. A water-soluble resin or emulsion-form polymer substance is dissolved in water or becomes an emulsion and suspended/dispersed in an electrolytic solution to be positively or negatively charged, and the pores of the sprayed coating electrode are charged by electrolysis. 2. The method for forming a composite thermal sprayed coating according to claim 1, wherein the composite thermal sprayed coating is made insoluble by moving into the interior, and is strongly solidified by subsequent heating and baking. 4. Water-soluble resins or emulsion-form polymer substances include epoxy resins, acrylic resins, polyester resins,
4. The method for forming a composite thermal spray coating according to claim 3, comprising at least one of a polyptadiene polymer and a maleated oil-based polymer.