KR100753909B1 - Repair method of pitting damage or cracks of metals or alloys by using electrophoretic deposition of nanoparticles - Google Patents

Abstract

A repairing method of pitting or cracks of metals or alloys by using electrophoretic repairing technology is provided to promptly repair pitting due to local damage or corrosion, and enable the repaired structure of the metals or alloys to obtain excellent mechanical strength by continuously forming a compact repaired structure without a gap in a state that the microstructure of a surrounding matrix is not changed. A repairing method of pitting or cracks of metals or alloys by using electrophoretic repairing technology comprises the steps of: preparing nanopowder particles of the same metal or alloy as a metal or alloy having a pitting or crack portion; preparing a colloidal dispersion-stabilized solution by adding the nanopowder particles of the metal or alloy of the step into an organic solvent to which a dispersant is added; immersing the metal or alloy having a pitting or crack portion into the colloidal dispersion-stabilized solution of the step; intensively depositing the nanopowder particles of the metal or alloy with a surface electric charge onto the pitting or crack portion of the metal or alloy to form an uniform layer by applying an electric field to the colloidal dispersion-stabilized solution by an electrophoretic deposition method, thereby concentrating a current density into the pitting or crack portion of the metal or alloy.

Description

Repair method of pitting damage or cracks of metals or alloys by using electrophoretic deposition of nanoparticles}

1 is a schematic diagram showing the aggregation of nano metal colloidal particles by the electrophoretic deposition method.

2 is a diagram showing a change in potential applied according to a change in current density.

3 is a diagram illustrating a change in current density with exposure time.

Figure 4 is a diagram showing the change in current density with the electrophoretic deposition time.

5 and 6 are photographs of the scanning electron microscope showing that the nano-colloidal particles are agglomerated by the electrophoretic deposition of the local damage or corroded site.

The present invention relates to a method for repairing defects or cracks in metals or alloys using electrophoretic repair techniques.

Mechanical parts containing various metals or alloys are corroded or damaged by various natural environmental conditions such as rain and snow, corrosive environment, or operating conditions of the parts used during use, resulting in defects or cracks in the parts. . As defects or cracks occur, the life of the parts is shortened, which shortens the time for replacement of new parts. The shortening of the parts replacement time causes a problem of raising the maintenance and repair costs of the apparatus constituted by the parts. In particular, when operating conditions of components, such as heat exchangers, various condensers, heat transfer tubes of equipment coolers, and various piping, are poor, it is necessary to maintain and repair them at an appropriate time.

Conventionally, the method of repairing the surfaces of heat exchangers, various condensers, heat transfer tubes of various types of equipment coolers, various pipes, and the like generally uses a plating method for coating the entire surface. However, such a plating method is difficult to apply depending on the part by coating the whole part, and it is impossible to apply depending on the part. As an example, the inspection and maintenance of domestic nuclear steam generators is largely self-reliant with domestic technology, but the maintenance technology is almost dependent on foreign countries, which leads to high maintenance cost of power plants, and appropriate inspection and repair time. It has been pointed out that there are various problems such as failure to secure the power supply, increase in the exposure of workers, and the possibility of leakage of radioactive material.

As a repairing method for a component having such defects or cracks, Korean Patent No. 266881 discloses a coating or coating having a desired alloy composition on the surface of a metal or alloy material by wet plating, electroplating or other methods, and then An alloying method using a laser beam on a metal or alloy material surface coated with plating to melt the surface with a beam to form an alloy layer, and a repair method for a damaged material surface are disclosed.

In addition, the Republic of Korea Patent No. 270193 is a method for repairing a defect of a large heat exchanger air flow tube, the step of fixing the explosion-expanded sleeve assembly to the broken heat transfer tube position; Explosion-expanding the explosion-expanding sleeve assembly at the position; Positioning the laser sleeving head in the position after removing the remnant for expansion; A laser welding step of welding a low melting point brazing metal on an outer surface of the sleeve assembly with a heat transfer tube by irradiating a laser beam to the inner surface of the sleeve assembly using the laser sleeving head in a circumferential direction; Disclosed is a sleeve assembly for expansion pipe.

In addition, the Republic of Korea Patent No. 425950, oil storage by producing a double oil storage tank by welding its joints in a state in which a continuous strip (strip) with a constant width to the inner circumferential surface of the oil storage tank is corrosion is progressing A method of repairing an oil storage tank is disclosed to completely repair the tank to prevent oil leakage due to corrosion.

In the present invention, electrophoretic deposition is a technique in which electrophoresis and deposition are combined. The electrophoretic deposition method is a method of combining the direct current and alternating current to control the movement of the charged particles to induce agglomeration of particles on the portion to be deposited, and the prior art is a partial crack using the electrophoretic deposition method It does not describe a method for repairing a part by intensively depositing nano metal colloids on the part.

An object of the present invention is to quickly repair pitting due to local damage or corrosion occurring on the surface of a metal or alloy material, and to maintain a dense repair structure continuously without gaps without changing the microstructure of the surrounding base material. The present invention provides a method for repairing defects or cracks in metals or alloys by using electrophoretic repair technology, in which a repair structure can obtain excellent mechanical strength.

In order to achieve the above object, the present invention comprises the steps of (a) preparing nanopowder particles of the same metal or alloy as the metal or alloy having a defect or cracking site; (b) adding the nanopowder particles of the metal or alloy of step (a) to an organic solvent to which a dispersant is added to prepare a colloidal dispersion stabilized solution; (c) immersing the metal or alloy having the defect or crack site in the colloidal dispersion stabilized solution of step (b); And (d) applying an electric field by electrophoretic deposition to the colloidal dispersion stabilized solution to concentrate a current density on a defect or cracked portion of the metal or alloy, thereby exerting a surface charge on the defect or cracked portion of the metal or alloy. It provides a method for repairing defects or cracks of a metal or alloy using an electrophoretic repair technique comprising the step of concentrated deposition of nano powder particles of a metal or alloy to form a uniform layer.

Hereinafter, the present invention will be described in detail.

The present invention includes methods for repairing defects or cracks in metals or alloys using electrophoretic repair techniques.

In the present invention, the electrophoretic repair technique disperses a metal or alloy powder having a particle size controlled by nanotechnology in an appropriate dispersion medium, and applies electric potential to the surface of the colloidal metal or alloy particles having a surface charge. As a method of repairing cracks or defects on the surface of structural components using electrophoresis by electrohydrodynamic flow, as shown in FIG. Alternatively, it is possible to repair and repair the selective coating and / or repair of the crack by concentrating the current density in the crack.

The step (a) according to the present invention is a step of preparing nanopowder particles of the same metal or alloy as the metal or alloy having a defect or crack site.

Nano powder particles of the metal or alloy of step (a) may be prepared by levitation-gas condensation. Flotation evaporation condensation is a technique well known in the art, for example, by heating and evaporating raw materials through high frequency induction heating to produce a powder, and condensing the powder again with an inert gas, such as nitrogen or argon, to form a nanopowder. It refers to a technique for producing, but is not limited thereto.

As the metal or alloy, all metal ions or alloys thereof may be used. For example, metals such as Ni, Zn, Fe, W, Sn, or alloys thereof, or alloys based thereon may be used. It is not limited. In this case, the nano powder particles of the metal or alloy may be prepared in the size of 10 nm to 40 nm range. This is because the dispersion into the colloidal solution in the above range can be facilitated, and the formation of aggregates by the electric field can easily facilitate the repair of defects or cracks.

The size of the nano colloid prepared using the nano powder particles of the metal or alloy may be prepared in the range of 10 ~ 100 nm. When the prepared nano colloid size is less than 10 nm, the ability of the nano metal colloid to aggregate due to a current density generated by a given electric field at a local damage or corrosion site may be degraded. It can exhibit the property to settle easily by its own weight within.

Step (b) according to the present invention is a step of preparing a colloidal dispersion stabilized solution by adding the nano powder particles of the metal or alloy of step (a) to an organic solvent to which a dispersant is added.

The organic solvent may be a C ₁ ~ C ₅ alcohol, the dispersing agent polyvinylpyrrolidone, polyacrylamide, polyacrylonitrile, polyethyleneimine, polyglycine, polyacrylic acid, polymethacrylic acid, poly (3 Hydroxybutyric acid), poly-L-leucine, poly-L-methionine, poly-L-proline, poly-L-serine, poly-L-tyrosine, poly (vinylbenzenesulfonic acid), poly (vinylsulfonic acid), etc. May be used, but is not limited thereto.

When the nanopowder particles are Ni, the dispersant is polyvinylpyrrolidone, and the organic solvent may be a C ₁ ~ C ₅ lower alcohol and the like.

In addition, the step (c) according to the present invention is a step of immersing the metal or alloy having the defect or crack site in the colloidal dispersion stabilized solution of the step (b).

The colloidal dispersion stabilized solution immersed in the metal or alloy having the defect or crack site may be used as an electrolyte solution to allow the electric field to flow well in the next step (d).

In addition, the step (d) according to the present invention is a defect or crack of the metal or alloy by focusing the current density on the defect or crack of the metal or alloy by applying an electric field by electrophoretic deposition to the colloidal dispersion stabilized solution Concentrating deposition of the nano-particle particles of the metal or alloy having a surface charge on the site to form a uniform layer.

The electric field can be used to maintain 100 to 1,500 seconds under 10 to 120 V / cm. When the electric field is less than 10 V cm ^-1 , it is difficult to cause the nano metal colloid to have a sufficient current density at the damage or corrosion site, so that it is difficult to induce agglomeration of the nano metal or alloy colloid, and when it exceeds 120 V cm ^-1 , Compared to the electric field, the aggregation of the nano metal or alloy colloid no longer increases.

For example, the electrophoretic deposition method uses a Ni or Ni-based alloy having defects or cracks as a working electrode, a platinum electrode as a counter electrode, and a colloidal dispersion solution in which Ni nano powder particles are dispersed as an electrolyte. Can be.

Electrophoretic deposition of defects or cracks in the metal or alloy may be caused by lyosphere distortion. The dissolution sphere distortion phenomenon is that van der Waals forces prevail as the polarity of the bilayer material composed of van der Waals forces or osmotic components is reduced, thereby causing the particles to aggregate by the polarity induced between the particles. It is a phenomenon.

The present invention may further comprise the step of heat treatment after forming the uniform layer. Through such heat treatment, the mechanical strength can be further improved.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples. However, the following examples are merely to illustrate the present invention, but the content of the present invention is not limited by the following examples.

< Example  1 ~ 2> Nickel Using Electrophoretic Vapor Deposition Metal plate  repair

To prepare the nano nickel colloid, 0.01% to 1% by weight of dispersant polyvinyl pyrrolidone and 0.01% to 1% by weight of nickel powder particles were dissolved in 1 L of ethanol, and the mixture was ultrasonically mixed for 3 hours. Nano nickel colloidal solution was prepared. The nano nickel colloid was measured with a zeta potential with a 90 plus particle size analyzer (Brookhaven Instruments, USA).

The nano nickel colloid was used as the electrolyte solution, and a nickel metal plate and a platinum plate that were locally damaged or corroded to the surface each having a size of 1 cm ² were immersed in the electrolyte solution. The nickel metal plate locally damaged or corroded to the surface connected the negative electrode and the platinum plate to the positive electrode.

For electrophoretic deposition on the nickel metal plate immersed in the nano nickel colloid, a PE 1649 DC power supply (PE 1649 DC power supply, Philips, Belgium) was used for 120 and 1200 seconds for a constant electric field of 20 V cm ^-1 , respectively. Specimens were processed.

< Example  Repair of Nickel Metal Plate Using Electrophoretic Vapor Deposition

In the embodiment, the specimen was applied in the same manner as in Example 1, except that a constant electric field of 100 V cm ⁻¹ was applied to the nickel metal plate immersed in the nickel dispersion solution, and the reaction was performed for 90 and 180 seconds, respectively. Treated.

< Experimental Example  1> Electrochemistry for Pit Defect Formation Polarization  Experiment

The change of current density with the potential applied for the formation of electrochemical fit defects on the surface of the pure nickel metal plate was observed. In this way, as the applied potential is increased in the positive (+) direction, a thick oxide film is formed on the surface of the Ni specimen due to a repassivation reaction. As the oxide film is continuously cracked as it is continuously increased to a higher potential than this, pits having various sizes and shapes are formed.

Using a nickel metal plate, potentiostat / Galvanostat (EG & G Model 263A), the injection rate is 0.5 mV s ⁻¹ , and the damaged specimen is immersed in 0.1 M sodium chloride solution used as an electrolyte solution. The potential was added in the range of -0.5 to 1.5 V (vs Ag / AgCl) to measure the current density according to the potential. The results are shown in FIG.

As shown in FIG. 2, it can be expected that stable formation and growth of a stable fit will occur above a fitting voltage of about 0.5 V (vs. Ag / AgCl). Therefore, in the present experimental example, a fit was prepared by applying a potential of 0.9 V (vs. Ag / AgCl) to a nickel metal specimen for 60 seconds.

Experimental Example 2 Measurement of Surface Current Density Change According to Pit Defect Formation

A nickel metal plate specimen was immersed in a 0.1 M sodium chloride solution with a potential of 0.9 V (vs Ag / AgCl) for 60 seconds to prepare a nickel plate specimen having a damaged surface. The change was measured and the results are shown in FIG. 3.

As shown in Figure 3 the formation process of the pit is the minimum time required for the formation of the _{pit ,} t _{pit , form} It can be seen that it is largely divided into the passivation step in which the current decreases rapidly and the formation and growth phase of the pits in which the current rapidly increases. The sharp decrease in current in the first stage is due to the formation of an oxide film due to the repassivation process on the exposed surface of the specimen, as described above, and the increase in current in the second stage results in a stable fit as the oxide film breaks. And because it grows.

< Experimental Example  3> Electrophoresis Current value  Change measurement

In order to measure the change in current density during electrophoresis of the damaged nickel metal plate, the following experiment was conducted.

The change in current value during electrophoresis of the nickel metal plate was measured using a 2010 multimeter (2010 multimeter, Kelthley, USA). The results are shown in FIG.

As shown in FIG. 4, it was found that as the electrophoretic deposition time increased, the current density of localized damage or corrosion sites increased. It can be seen that the aggregation of the nano nickel colloid is strong in the local damage or corrosion site.

< Experimental Example  4> Scanning electron microscope

In order to determine the degree of deposition of nano nickel colloid according to the electrophoresis time, the following experiment was conducted.

Morphological changes of the nickel metal plates of Examples 1 to 4 were observed using a scanning electron microscopy (SEM, XL 30 SEFG), and the results are shown in FIGS. 5 and 6.

As shown in Figures 5 and 6, the local 120 seconds, damage or nickel metal plate with a corrosion area under nano nickel colloid is present, the electric field for 1200 seconds 20 V ㎝ ^- respectively 90 and Examples 1 and 2 were added to ^1, 180 a second electric field for a 100 V ㎝ ^- for the embodiment was added to ^1, examples 3 and 4 was confirmed that the nano nickel colloidal intensively deposited on the pit defect portion of the nickel metal plate, in particular, an electric field for 1200 seconds, 20 V ㎝ ^In the case of Example 2 added to ^-1 , it was confirmed that a very smooth repair surface texture was formed at the local damage or corrosion site.

In view of this, the nano nickel colloid increases the density of the current at the local damage or corrosion site as an electric field is applied, which causes the nano nickel colloid to be concentrated to repair the nickel metal plate.

Repair method according to the present invention has a faster process time than the conventional repair method, can be performed at a low temperature does not affect the microstructure of the surrounding base material, forming a continuous, dense bond repaired tissue excellent mechanical strength There is an advantage that can be obtained, it is expected that it can be usefully applied to repair techniques of various metals or alloys having various defects or cracks.

Claims (11)

(a) preparing nanopowder particles of the same metal or alloy as the metal or alloy having the defect or crack site; (b) adding the nanopowder particles of the metal or alloy of step (a) to an organic solvent to which a dispersant is added to prepare a colloidal dispersion stabilized solution; (c) immersing the metal or alloy having the defect or crack site in the colloidal dispersion stabilized solution of step (b); And (d) applying the electric field by electrophoretic deposition to the colloidal dispersion stabilized solution and concentrating the current density on the defect or cracked portion of the metal or alloy, thereby causing a surface charge on the defect or cracked portion of the metal or alloy. Or depositing nanopowder particles of an alloy to form a uniform layer. Metal or alloy defect or crack repair method using an electrophoretic repair technology comprising a. The method of claim 1, wherein the nano-particle particles of the metal or alloy of step (a) is produced by a levitation-gas condensation (levitation-gas condensation) characterized in that the defect of the metal or alloy using an electrophoretic repair technique or Crack repair method. 3. The method of claim 1, wherein the nanopowder particles of the metal or alloy have a size in a range of 10 nm to 40 nm. The electrophoretic repair technique of claim 1, wherein the metal or alloy includes Ni, Zn, Fe, W, or Sn, or an alloy thereof or an alloy based thereon. Method for repairing defects or cracks in metals or alloys using The method of claim 1, wherein the organic solvent of step (b) is one or more selected from the C ₁ ~ C ₅ alcohol, the defect or crack repair method of a metal or alloy using an electrophoretic repair technique. The method of claim 1, wherein the dispersing agent of step (b) is polyvinyl pyrrolidone, polyacrylamide, polyacrylonitrile, polyethyleneimine, polyglycine, polyacrylic acid, polymethacrylic acid, poly (3-hydroxybutyric acid ), Poly-L-leucine, poly-L-methionine, poly-L-proline, poly-L-serine, poly-L-tyrosine, poly (vinylbenzenesulfonic acid) and poly (vinylsulfonic acid) Method for repairing defects or cracks in metals or alloys using electrophoretic repair technology, characterized in that it is selected. The dispersant according to any one of claims 1 or 4 to 6, wherein the dispersing agent is polyvinyl pyrrolidone and the organic solvent is C ₁ to C when the nano metal powder of step (b) is Ni. Method for repairing defects or cracks in metals or alloys using electrophoretic repair technology, characterized in that the lower alcohol of ₅ . 8. The method of claim 7, wherein the electric field of step (d) is maintained at 10 to 120 V / cm for 100 to 1,500 seconds. The method of claim 7, wherein the electrophoretic deposition of step (d) uses Ni or Ni-based alloys having defects or cracks as working electrodes, platinum electrodes as counter electrodes, and Ni nano powders as electrolytes. Method for repairing defects or cracks in metals or alloys using an electrophoretic repair technique, characterized in that using a colloidal dispersion solution in which particles are dispersed. delete The method of claim 1, further comprising the step of heat treatment after forming a homogeneous layer in the step (d).

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