KR101625004B1 - Post-treatment method for the member including the film - Google Patents

Abstract

The present invention relates to a method for post-treating a member with a film and, more specifically, relates to the method for post-treating the member with a film for fusion reactor facing material. The present invention provides the method for post-treating the member with the film comprising a step of heating a film by applying a high frequency direct current pulse to the film while applying a pressure to a member coated with an electrical conductor film on at least one surface of a substrate, and a direction of applying a pressure having a component in a direction of a normal vector direction of a layer formed with the film.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a post-

The present invention relates to a method for post-treatment of a member having a film formed thereon, and more particularly to a method for post-treatment of a member formed with a coating film for nuclear fusion.

More than 80% of the world's energy consumption now depends on fossil fuels, and this trend is unlikely to change significantly over the next few decades. According to a report by BP (British Petroleum), as of 2009, the total amount of resources that can be mined is about 1.3333 trillion barrels of oil (45.7 years), natural gas 187.5 trillion cubic meters (62.8 years) and coal 822 billion tons (119 years) . In addition, uranium, which accounts for most of the current nuclear power generation, is depleted in about 70 years. Global demand for energy will continue to increase compared to the amount of resources depleted. Especially, demand for energy is expected to surge due to the economic growth of major economies such as China, India and Brazil.

On the other hand, Korea is highly dependent on fossil fuels for power generation and most of the crude oil is imported from the Middle East region. Therefore, it is urgent to secure stable energy supply because crude oil supply is unstable and price fluctuation is widespread due to international situation. In addition, fossil fuels are considered to be the cause of environmental disasters in terms of carbon dioxide emissions. New and renewable energy such as solar / photovoltaic energy, biomass, and wind energy is being actively developed as the need to develop new clean energy sources to replace fossil fuels is being emphasized.

However, new and renewable energy is not enough to meet demand because of low efficiency of energy conversion and instability due to natural conditions. As an alternative to this, fusion energy is attracting attention. Fusion energy uses sea water as a raw material, so there is no fear of depletion of resources and is safer than fission power generation. However, in order to produce high-performance plasma and to produce an output energy amount efficiently, It is necessary to raise the temperature to an ultra-high temperature of 100 million degrees Celsius or more.

In addition, the technology of ultrahigh temperature and ultrahigh material that can withstand high vacuum should be preceded. Among them, tungsten is attracting attention as a material which confronts the plasma in a plasma sealing device called a tokamak. However, tungsten has brittleness at low temperatures, and tungsten has a high density in terms of structural load, so it has a drawback that it must be used with other structural materials.

Korean Patent No. 10-1459051 (October 31, 2014)

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a method for post-treatment of a member having a coated film capable of improving mechanical properties. However, these problems are exemplary and do not limit the scope of the present invention.

According to one aspect of the present invention, there is provided a method for post-treatment of a film-formed member. The method comprising the steps of: applying a high frequency direct current pulse to the film while applying pressure to a member having an electrical conductor coating formed on at least one side of the substrate to heat the coating film; May have a component in the normal vector direction of the coated layer.

The coating may be formed by spraying.

The spraying method may be selected from a gas flame thermal spray method, an arc thermal spray method, a plasma spray method, a detonation thermal spray method, a vacuum plasma spraying method and a high-speed flame spraying method High Velocity Oxy-Fuel Spraying) may be used.

The coating may comprise tungsten.

The heating may include raising the temperature to a temperature of 900 ° C to 1100 ° C.

The heating may include applying a pulse current of up to 4000 A, 20 kHz.

The substrate may be an electrical conductor, and one of the electrodes for applying the high-frequency DC pulse may be arranged to be in contact with the substrate and the other to be applied to the coating.

The heating may include applying a pulse current of at least 50 A / mm 2 to a maximum current density of 250 A / mm 2 to the coating.

According to one embodiment of the present invention as described above, a post-processing method of a member having a film formed to dense the microstructure and capable of improving the mechanical properties of the fusion-bonded face material can be realized. Of course, the scope of the present invention is not limited by these effects.

1 is a schematic view of a post-treatment apparatus used in a post-treatment method of a coated member according to an embodiment of the present invention.
2 is a flowchart schematically showing a post-treatment method of a coated member according to an embodiment of the present invention.
FIGS. 3 to 5 are graphs showing the results of analysis of samples implemented by a method of post-processing a coated member according to some experimental examples and comparative examples of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, Is provided to fully inform the user. Also, for convenience of explanation, the components may be exaggerated or reduced in size.

It is to be understood that throughout the specification, when an element such as a film, region or substrate is referred to as being "on", "connected to", "laminated" or "coupled to" another element, It is to be understood that elements may be directly "on", "connected", "laminated" or "coupled" to another element, or there may be other elements intervening therebetween. On the other hand, when one element is referred to as being "directly on", "directly connected", or "directly coupled" to another element, it is interpreted that there are no other components intervening therebetween do. Like numbers refer to like elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

Although the terms first, second, etc. are used herein to describe various elements, components, regions, layers and / or portions, these members, components, regions, layers and / It is obvious that no. These terms are only used to distinguish one member, component, region, layer or section from another region, layer or section. Thus, a first member, component, region, layer or section described below may refer to a second member, component, region, layer or section without departing from the teachings of the present invention.

Also, relative terms such as "top" or "above" and "under" or "below" can be used herein to describe the relationship of certain elements to other elements as illustrated in the Figures. Relative terms are intended to include different orientations of the device in addition to those depicted in the Figures. For example, in the figures the elements are turned over so that the elements depicted as being on the top surface of the other elements are oriented on the bottom surface of the other elements. Thus, the example "top" may include both "under" and "top" directions depending on the particular orientation of the figure. If the elements are oriented in different directions (rotated 90 degrees with respect to the other direction), the relative descriptions used herein can be interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include singular forms unless the context clearly dictates otherwise. Also, " comprise "and / or" comprising "when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

Hereinafter, embodiments of the present invention will be described with reference to the drawings schematically showing ideal embodiments of the present invention. In the figures, for example, variations in the shape shown may be expected, depending on manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present invention should not be construed as limited to the particular shapes of the regions illustrated herein, but should include, for example, changes in shape resulting from manufacturing.

1 is a schematic view of a post-treatment apparatus used in a post-treatment method of a coated member according to an embodiment of the present invention.

Referring to FIG. 1, a post-treatment apparatus 1000 used in a post-treatment method of a coated member according to an embodiment of the present invention includes a circular specimen 100 sprayed in a mold 110, 210 may be brought into contact with the upper surface and the lower surface of the test piece 100, respectively. The mold 110 has a hole for inserting the test piece 100 into a cylindrical shape with a graphite carbon material and the test piece 100 may have a coating 20 formed on the base material 10. The electrode 210 can be formed to have a size that can be inserted into a hole of the mold 110, for example, a material such as the mold 110, that is, a graphite material. Although the mold 110 and the electrode 210 are shown in a cylindrical shape, they may be formed in different shapes depending on the shape of the test piece 100.

One of the electrodes 210 is brought into contact with the substrate of the base material 10 after the test piece 100 is placed in the mold 110 and the remaining electrode 210 is in contact with the other film 20, A high frequency direct current pulse is applied to the test piece 100 by the power supply 300 under the pressure of the electrode pressing part 200 of the device 900 while applying pressure to the test piece 100 to apply the coating 20 of the test piece 100 It can be heated. For example, the coating film 20 can be heated by applying a pulse current of at least 50 A / mm 2 to a maximum current density of 250 A / mm 2 to the coating film 20.

2 is a flowchart schematically showing a post-treatment method of a coated member according to an embodiment of the present invention.

Referring to FIG. 2, a method of post-treating a coated member according to an embodiment of the present invention includes forming a coating on a substrate using an atmospheric pressure plasma spraying method (S100), applying a high- And applying a pulse to heat the coating (S200).

A more detailed description of the method of post-treatment of the coated member is to use a spraying method on the electrical conductor substrate to produce a member having an electrical conductor coating. The thermal spraying may be performed by, for example, a gas flame thermal spray method, an arc thermal spray method, a plasma thermal spray method, a detonation thermal spray method, a vacuum plasma spraying method, And High Velocity Oxy-Fuel Spraying may be used.

And applying a high frequency direct current pulse to the film while applying pressure to the member having the electric conductor film formed by the above method to heat the film. At this time, the direction in which the pressure is applied may have a component in the normal vector direction of the coated layer. Here, the component in the normal vector direction means a component other than 0, and assuming a horizontal coating layer, the direction of applying the pressure may be a direction perpendicular to the coating layer.

That is, for example, a specimen can be formed by using atmospheric plasma plasma of tungsten powder on a graphite substrate using helium and hydrogen as a plasma induction gas. The substrate may be a graphite base material. After putting the specimen into a mold, the electrode material is engaged, and the electrode material is mounted in the discharge plasma sintering apparatus, and then the pressure can be increased to about 2 kN to 3 kN.

At this time, any one of the electrodes for applying the high-frequency DC pulse is contacted with the graphite substrate and the other is brought into contact with the tungsten film so that a pulse current of 4000 A and 20 kHz at maximum is applied to the tungsten film, Temperature can be raised. After reaching the set temperature, the furnace can be cooled after maintaining the set temperature for a predetermined time.

Hereinafter, an experimental example to which the technical idea described above is applied will be described in order to facilitate understanding of the present invention. It should be understood, however, that the following examples are for the purpose of promoting understanding of the present invention and are not intended to limit the scope of the present invention.

FIGS. 3 to 5 are graphs showing surface microstructure and hardness analysis results of samples implemented by a method of post-treatment of a coated member according to some experimental examples and comparative examples of the present invention.

3 to 5, Samples 1 to 8 are comparative examples of the present invention, and Samples 9 to 14 are experimental examples of the present invention. In all cases, a specimen with a thickness of about 200 μm was formed on a graphite base material by an atmospheric pressure plasma spraying method.

Specifically, Sample 1 was subjected to an optical microscope, a scanning electron microscope and a hardness test in order to obtain basic information on a reference specimen after the atmospheric plasma spraying of the tungsten powder on the graphite base material and without post-treatment. Sample 2 was a vacuum heat treated sample maintained at a vacuum degree of 10 ^-4 torr at about 900 ° C for about 1 hour. Samples 3 to 8 were prepared by applying a pressure of 2 kN and 3 kN at 900 ° C., 1000 ° C. and 1100 ° C., respectively, to the specimens in the vapor deposition direction, and each temperature was maintained for about 10 minutes. The specimen was subjected to a pressurized heat treatment at an elevation rate of about 100 ° C / min in an argon (Ar) gas atmosphere of about 1 atm.

On the other hand, in Samples 9 to 14, a high frequency pulse direct current was applied to the sample to generate resistance heat in the specimen, and the temperature was raised to heat treatment. A discharge plasma sintering apparatus was used to create an environment in which a pulse current could flow through the specimen, and a pressure of about 2 kN and a pressure of about 3 kN was applied to the specimen at a pressure of about 2 kN, respectively. At this time, the final temperatures of the specimens were about 900 ° C., about 1000 ° C., and about 1100 ° C., respectively, and they were kept at the final temperature for about 10 minutes, followed by cooling.

FIG. 3 is a microstructure analysis result obtained by analyzing the surface of each sample by an optical microscope, and FIG. 4 is a microstructure analysis result obtained by analyzing the surface of each sample by a scanning electron microscope. Referring to FIGS. 3 and 4, among the characteristics of the thermal spray coating, the spaces between the lumps due to the sequential accumulation of the powdery molten masses in the base material are confirmed by the sprayed gas, which is called a splat boundary.

Since the flat boundaries deteriorate the overall physical properties of the tungsten coating, efforts are made to eliminate the flatness through heat treatment. The splat boundary can be observed through an optical microscope, but can also be confirmed clearly by a scanning electron microscope. In the sputter boundary, the rate at which the melting point is transferred to the inside due to the rapid temperature difference between the base material and the molten tungsten splat is smaller than the growth rate of the crystal grains. Therefore, it can be confirmed that the crystal growth direction is determined and the crystal structure inside one splat forms a columnar structure. The solidification proceeds at a rapid and rapid rate due to the contact with the substrate, so that the crystals having the first orientation do not have enough time to grow.

In addition, we compared the microstructure of sample 1 on the side of the flat boundaries. Qualitatively comparing the ratio of the sputter boundary, which is an empty space between spatters, sample 2, which was vacuum heat-treated at about 900 ° C for 1 hour, showed a microstructure similar to that of sample 1. In the case of Samples 3 to 8 and other Samples 9 to 14 after the application of the pulse DC by the pressurization heat treatment performed in another post-treatment method, first, the optical observations revealed that the area observed with the flat boundary was considerably reduced .

On the other hand, referring to Samples 3 to 8 and Samples 9 to 14 shown in FIG. 3, when the same treatment is performed after the pressurizing heat treatment, the higher the temperature, the harder the pressure in the same temperature condition, The spacing between the splats decreases. In addition, when the microstructures of the post-treatment method in which the temperature and the pressure are the same are increased by the simple pressurization heat treatment and the pulse direct current, the flat boundary is removed from the microstructure after the pulse direct current application Can be confirmed.

The results of the image analysis by the optical microscope as described above can be confirmed by the scanning electron microscope analysis results shown in FIG. 4, and it can be confirmed that the heating process by directly applying high frequency pulse DC to the specimen is effective for reducing the space of the flat boundary.

On the other hand, in most of the specimens subjected to the post-treatment, preferential orientation is not generated in the tungsten film compared to the sample 1, or the crystal distribution does not change. It seems that the temperature range between about 900 ° C and 1100 ° C is not high enough to cause recrystallization or recovery of the tungsten material. It is generally known that the recrystallization of the metal material is located between 1/3 and 1/2 of the melting point temperature and the recrystallization temperature of tungsten is located within the temperature range of about 1300 to 1500 ° C. Thus, It can be seen that no remarkable change in crystal distribution was observed in the electron backscattering diffraction analysis.

In addition, when using the discharge plasma sintering method for sintering a powder sample, it is more effective than the general sintering method or hot pressing because localized necking due to the heating of the jets is caused on the fine contact surfaces between the powder grains, It has been reported that densification of the material occurs with time.

In this experiment, the tungsten film of the specimen consists of the accumulation form of splat, so that the splat can be regarded as a kind of powder grains. In this case, in the process of flowing the high-frequency pulse current, the pressure and the direct current are applied, and a local temperature concentration region occurs due to the joule heating at a small contact area between the sputter and the spatter, It can be deduced that the microstructure of the film is more dense.

5 is a graph summarizing the hardness measurement results of the respective samples. Referring to FIG. 5, the plasma facing material is subjected to continuous plasma particles and heat irradiation, which increases the probability of corrosion and shortens material life. There are various mechanical properties that can be evaluated as resistance to plasma particle irradiation, such as toughness, ductility, hardness, and long life.

However, in this experiment, the experiment was conducted with the goal of hardness standard of ITER and DEMO recommendations. The hardness load of the recommendation should be about 300N under HV30, but it is about 200um high enough to durably deposit the tungsten film by the currently optimized atmospheric plasma spraying method. Therefore, in this experiment, we try to compare all types of samples with a maximum load of about 0.5 N in consideration of the indentation size.

The measured hardness is 122 HV (standard deviation 27). The hardness of the tungsten block, which is not a sprayed tungsten film, can be changed depending on the block manufacturing method and the tungsten powder used as the raw material. However, the hardness of the block made of the raw powder of the reference tungsten film is about 502HV and the tungsten film The hardness is about one fourth of the bulk block.

The reason why the atmospheric plasma sprayed tungsten film has lower hardness than the tungsten bulk material is the influence of the splat boundary. From the viewpoint of microstructure, it was shown that the scattering of the scattering boundary decreased the compactibility due to a considerable amount of bubbles and cracks so that the overall mechanical properties of the coating could be adversely affected.

Hardness values of Sample 1 were compared with those of various post-treatment conditions. Microindentation test was performed on the cross section of the specimen after grinding with a gap of about 100 μm or more for each specimen. The results are as follows. The average hardnesses of the tungsten coatings of Sample 1 and Sample 2 were 134.66 HV and 134.97 HV, respectively, and the standard deviations thereof were 13.68 HV and 9.95 HV.

Sample 1 subjected to post-treatment, Sample 2 subjected to vacuum heat treatment at about 900 ° C for 1 hour, and Sample 1 to 2 having a pressure of about 2 kN and 3 kN in the direction of vapor deposition of the specimen at temperature conditions of about 900 ° C, 1000 ° C, and 1100 ° C, The hardness of the tungsten film for Sample 8 is shown in Fig. 5 (a).

Considering the dimensions of each sample, the forces of 2 kN and 3 kN are 25.47 MPa and 38.21 MPa, respectively, when converted to pressure. It can be seen that the higher the heat treatment temperature and the higher the applied pressure, the higher the hardness. Hardness corresponding to the pressures 25.47 MPa and 38.21 MPa when the heat treatment holding temperature is 900 ° C is 167.83 and 167.87, respectively, and standard deviations are 30.74 HV and 22.02 HV. At a holding temperature of 1000 占 폚, hardness per pressure is 259.26HV, 276.15HV, standard deviation is 46.25HV, 54.32HV. At 1100 ° C, the hardness per pressure is 282.02HV and 286.95HV per pressure, and the standard deviations are 59.32HV and 66.22HV, respectively. Although the range of standard deviation overlaps for each treatment condition, it can be seen that the increase of temperature and pressure is related to the increase of hardness from the tendency of average value.

In addition, the sample 1 subjected to the post-treatment, the sample 2 subjected to the vacuum heat treatment at about 900 ° C for 1 hour, and the sample 2 at about 900 ° C, 1000 ° C and 1100 ° C were subjected to a pressure of about 2 kN and 3 kN 5 (b) shows the hardness of the tungsten film for the samples 9 to 14 to which the high-frequency DC pulse was applied.

As in the case of the above pressurized heat treatment, the higher the heat treatment temperature and the higher the applied pressure, the higher the hardness becomes. The hardness values measured at the holding temperature of about 900 ° C, 25.47 MPa and 38.21 MPa are 212.12 HV and 247.35 HV, respectively, with standard deviations of 56.75 HV and 32.02 HV. When the holding temperature is 1000 ° C, the average hardness is 340.25 HV and 358.52 HV, respectively, and the standard deviation is 41.80 HV and 56.52 HV. Finally, at 1100 ℃, the mean hardness of each is 363.16HV, 363.11HV, and each standard deviation is 46.90HV and 23.87HV.

In the case of the same temperature, the same pressure and the same holding time condition in the high-frequency pulse direct current applying method using the post-pressurizing heat treatment and the discharge plasma sintering apparatus, when the high frequency pulse direct current is flowed, It can be seen that the hardness of the tungsten film is greatly improved as compared with the treatment. In this case, the hardness of the tungsten bulk material was measured at about 501 HV when the hardness was 0.5 N, which is the same as the tungsten film test. Post-treatment of direct pulsed direct current to the specimen will result in a tungsten film hardness greater than 70 percent of the bulk hardness.

By slowing down the rate of surface erosion due to fusion of various plasma particles, it is possible to increase the number of reinforcement cycles of tungsten film which should be repetitively reinforced, and to reduce the generation rate per hour of tungsten byproducts which can act as impurities in reaction plasma You can expect to be there.

Of course, it is an example that the coating member implemented by the post-treatment method of the film-formed member according to the embodiment of the present invention is applied to the fusion-bonded face material, and the technical idea of the present invention is not limited to the kind of the example material But is not limited thereto. Therefore, the above-mentioned film member is applicable to all of the film members used in a high corrosive environment because the film member is excellent in corrosion resistance and hardness besides the use of the fusion member as a fusion member.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

10: base metal
20: Coating
100: The Psalms
110: mold
200: electrode pressing portion
210: electrode
900: Discharge plasma sintering apparatus
1000: Post-processing device

Claims (8)

Applying a high frequency direct current pulse to the coating while applying pressure to a member having an electrical conductor coating formed on at least one side of the substrate to heat the coating;
Lt; / RTI >
The direction of applying the pressure has a component in the normal vector direction of the layer on which the film is formed,
Wherein the substrate comprises graphite,
Wherein the coating comprises tungsten,
In the heating step, the high frequency pulse current has a maximum of 4000 A, 20 kHz, a current density of 50 A / mm 2 to a maximum of 250 A /
In the heating step, the pressure is in the range of 20 MPa to 40 MPa,
Wherein the heating step raises the temperature to a temperature of 900 占 폚 to 1100 占 폚. The method according to claim 1,
Wherein the coating is formed by spraying.
A method of post-treatment of a film-formed member. 3. The method of claim 2,
The spraying method may be selected from a gas flame thermal spray method, an arc thermal spray method, a plasma spray method, a detonation thermal spray method, a vacuum plasma spraying method and a high-speed flame spraying method High Velocity Oxy-Fuel Spraying)
A method of post-treatment of a film-formed member. delete delete delete The method according to claim 1,
Wherein one of the electrodes for applying the high-frequency DC pulse is in contact with the substrate and the other is applied to the coating,
A method of post-treatment of a film-formed member. delete

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