WO2018093146A1 - Method for coating iron-based alloy and product produced thereby having high hardness and low frictional property - Google Patents

Abstract

The present invention relates to a method for coating an iron-based alloy and, more specifically, to a method for forming a chromium-based coating layer on a surface of an iron-based alloy by pack cementation, and a nitrocarburized layer on the chromium-based coating layer by using screen plasma. Therefore, by using pack cementation and screen plasma to form a chromium-based coating layer and a nitrocarburized layer on an iron-based alloy, the present invention can produce a product having high hardness and excellent low frictional properties.

Description

Coating method of iron-based alloy and products having high hardness and low friction characteristics produced thereby

The present invention relates to a method for coating an iron-based alloy and a product having high hardness and low friction characteristics, and more particularly, after forming a chromium-based coating layer by pack cementation on the surface of the iron-based alloy, the chromium-based coating layer is The present invention relates to a coating method of an iron-based alloy for coating an iron-based alloy layer by screen plasma immersion carbonization on a formed iron-based alloy, and a product having high hardness and low friction characteristics.

In general, pack cementation is a kind of chemical vapor deposition (CVD) technique, in which an iron-based alloy and a pack mixture powder are charged into a pack, and then the pack is heated to coat the iron-based alloy. The pack mixture powder is a powder containing a reactive metal such as chromium (Cr), aluminum (Al), silicon (Si), etc., an active agent such as ammonium chloride (NH ₄ Cl), and an inert such as alumina (Al ₂ O ₃ ). to be. When the pack is heated, the reaction metal and the activator react with each other, and the reaction metal, which has become a gaseous state, penetrates into the surface of the iron-based alloy to form a coating layer containing the reaction metal as a main component. The inert agent prevents sintering of the iron-based alloy during coating.

Pack cementation is a coating method that has been used for a long time and has many advantages. Pack cementation is a coating method for forming a coating layer that is simple, economical and has good adhesion. And the iron-based alloy coated by the pack cementation has mechanical properties such as improved hardness, corrosion resistance, wear resistance, oxidation resistance and the like. In addition, a uniform coating layer may be formed on the entire surface of the iron-based alloy having a three-dimensional shape by pack cementation.

Pack cementation may be classified into chromizing, aluminizing, siliconizing, etc. according to the kind of reactive metal. In connection with the above chromizing, Patent No. 10-1384374 (name of the invention: a method for coating a metal sintered part by pack cementation and a pack cementation coated metal sintered part, Patent Document 1) is disclosed. In connection with the aluminizing, US Patent Publication No. 2011-0293365 (name: Cement plant refractory anchor, Patent Document 2) is disclosed. And, in connection with the siliconizing, US Patent No. 5275983 (Pack name of the invention: Pack mixture composition for SiC pack cementation coating of carbonaceous substrates, Patent Document 3) is disclosed.

On the other hand, parts such as bearings and bushings are used in a device that rotates at high speed, and require low friction characteristics as well as high hardness surfaces. However, iron-based alloys have a high hardness surface but have a high friction coefficient to be used as materials for bearings and bushings.

In order to solve this problem, it was intended to reduce the friction coefficient of the iron-based alloy by carbonizing nitrogen and carbon using the plasma method.

However, in the plasma method, an arc occurs directly on the iron-based alloy, which damages the surface of the iron-based alloy, and the internal temperature is not uniform due to a glow generated on the surface of the iron-based alloy. there was.

In order to solve this problem, a screen plasma method is used to penetrate nitrogen atoms and carbon atoms to improve hardness and reduce friction coefficients by forming new carbide and nitride complexes on the surface of iron-based alloys.

Screen plasma immersion carbonization is a method of generating plasma directly on the surface of an iron-based alloy to penetrate nitrogen and carbon. Unlike the conventional plasma method, plasma is generated through a screen separated from the iron-based alloy to infiltrate nitrogen to form an immersion carbonization layer. It is a method of manufacturing.

1 shows a typical screen plasma apparatus. The screen plasma apparatus includes a vacuum chamber 10, a screen 20, a heater 30, a vacuum pump 40, a cathode power supply 50, and a heater power supply 60. Referring to FIG. 1, a general screen plasma precipitated carbonization is described.

First, the vacuum chamber 40 is operated to create a vacuum pressure atmosphere of about 1 × 10 ^-3 Torr in the vacuum chamber 10, and then the cathode power supply unit 50 connected to the screen 20 is operated to operate the screen. The heater 20 is heated and the heater 30 is connected to the heater 30 so that the heater 30 is heated to raise the temperature in the vacuum chamber 10 to the process temperature. At this time, the inner wall of the vacuum chamber 10 shows a positive (+) relative charge, and the screen 20 shows a negative (-) relative charge, so that an electric field is generated between the inner wall of the vacuum chamber 10 and the screen 20. .

Next, nitrogen, hydrocarbon and hydrogen gas are injected into the vacuum chamber 10. At this time, the hydrogen gas is formed in a high temperature and a vacuum atmosphere inside the vacuum chamber 10, and as soon as it is injected into the vacuum chamber 10 receives the energy of the temperature and pressure is plasmaized, hydrogen plasma and hydrocarbon plasma is screened (20) Dense around.

Nitrogen gas has a relatively high ionization energy than hydrogen gas, and thus, plasma is not smoothed. However, the plasma plasma hydrogenated already collides with the nitrogen gas and serves to smoothly generate the nitrogen plasma.

The nitrogen and hydrocarbon plasmas penetrate into the iron-based alloy 2 located at the center of the vacuum chamber 10, and the iron-based alloy is carbonized.

Screen plasma immersion carbonization using the screen plasma apparatus as described above has a problem of heating the vacuum chamber by using a heater, which is an additional device, to increase the temperature of the vacuum chamber to the process temperature. In addition, when the iron-based alloy is exposed to air, the iron-based oxide film is naturally formed on the surface, which causes the iron-based oxide film to inhibit the nitriding carbonization process, and there is a problem that the iron-based oxide film is removed by lowering the magnetic conductivity of the iron-based alloy.

In addition, the conventional screen plasma apparatus applies a high-current power source and applies a cathodic, so that a high-density input process of the penetrating element is not possible due to the reaction of nitrogen and hydrocarbon gas in the glow, thereby accelerating the particle accelerator. B. There was a problem in that a high voltage is applied to the device to form an immersion layer on the iron-based alloy.

Therefore, there is a demand for technology development of an iron-based alloy coating method that can control the iron-based oxide film while increasing the hardness of the iron-based alloy and lowering the friction coefficient, and does not require an additional heating process.

[Preceding technical literature]

[Patent patent]

(Patent Document 1) Republic of Korea Patent No. 10-1384374

(Patent Document 2) United States Patent Publication No. 2011-0293365

(Patent Document 3) US Patent No. 5275983

The technical problem to be achieved by the present invention is to control a strong oxide film, such as Cr ₂ O ₃ is naturally formed in a stainless steel material that can be removed only by processing outside the conventional pickling operation, while a very small amount without a separate external heater in the heating process It is to provide an iron-based alloy coating method using a heating process using a glow (glow) formed on the screen by the amount of gas input and power. Specifically, it aims to provide a new alloy coating on the outermost surface of the coating layer using nitrogen and carbon in atomic units, and to provide a product having high hardness and low friction characteristics manufactured by the above method.

The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

In order to achieve the above object, an embodiment of the present invention is to form a chromium-based coating layer on the surface of the iron-based alloy using the pack cementation, and to form an impregnated carbonization layer using a screen plasma on the chromium-based coating layer It provides an iron-based alloy coating method comprising the step of.

In an embodiment of the present invention, the iron-based alloy may be an iron-based alloy coating method characterized in that it comprises a bearing steel or stainless steel.

In an embodiment of the present invention, the chromium-based coating layer is characterized in that it contains chromium (Cr), chromium (Cr) and iron (Fe) or chromium (Cr), iron (Fe) and vanadium (V) Alloy coating method.

In an embodiment of the present invention, the step of forming a chromium-based coating layer on the surface of the iron-based alloy using the pack cementation, the step of injecting the iron-based alloy and the pack mixture in a pack (pack), charging the pack into a vacuum chamber And a chromium-based coating layer forming step of forming a chromium-based coating layer on the iron-based alloy while heating is maintained in the charging step, a heating step of heating the pack charged in the vacuum chamber, and the heating step, wherein the pack mixture is formed of chromium. It may be an iron-based alloy coating method comprising a powder, an active agent and an inert agent.

In an embodiment of the present invention, the chromium-based powder of the pack mixture is chromium (Cr) powder, chromium (Cr) powder and iron (Fe) powder or chromium (Cr) powder, iron (Fe) powder and vanadium (V) It may be an iron-based alloy coating method characterized in that it comprises a powder.

In an embodiment of the present invention, the pack mixture is characterized in that it comprises 10.5 wt% to 52.9 wt% of the chromium-based powder, 0.1 wt% to 3 wt% of the active agent and 47 wt% to 89.4 wt% of the inert agent. It may be an iron-based alloy coating method.

In an embodiment of the present invention, the step of forming the nitriding carbide layer using the screen plasma on the chromium-based coating layer, charging the iron-based alloy coated with the chromium-based coating layer in a vacuum chamber and covers the iron-based alloy with a double screen The ion cleaning step of reducing the chromium-based oxide film present on the iron-based alloy by injecting a first hydrogen gas into the vacuum chamber, a process current is applied to the dual screen and the second hydrogen gas, nitrogen in the vacuum chamber Generating a mixed plasma by injecting a gas and a hydrocarbon gas; and coating the mixed plasma on a chromium-based coating layer formed on the surface of the iron-based alloy to form an impregnated carbonized layer. have.

In an embodiment of the present invention, the ion cleaning step includes applying a first current to the dual screen to heat the vacuum chamber, injecting first hydrogen into the vacuum chamber, and applying the second screen to the dual screen. Generating a hydrogen plasma around the dual screen by applying a current; and reducing and removing the chromium-based oxide film present on the iron-based alloy.

In an embodiment of the present invention, the first current may be 3 A to 5 A and the second current may be iron-based alloy coating method, characterized in that 5 A to 15 A.

In an embodiment of the present invention, the chromium-based oxide film is characterized in that it contains chromium (Cr), chromium (Cr) and iron (Fe) or chromium (Cr), iron (Fe) and vanadium (V) Alloy coating method.

In an embodiment of the present invention, the process current may be an iron-based alloy coating method, characterized in that 20 to 30 A.

In an embodiment of the present invention, the content ratio of the nitrogen gas to hydrogen gas may be an iron-based alloy coating method, characterized in that 1: 3 to 4: 1.

In an embodiment of the present invention, the hydrocarbon gas may be an iron-based alloy coating method, characterized in that the CH ₄ or C ₂ H ₂ and 1 sccm to 10 sccm gas amount is pulse-injected by repeating the injection section and the stop section. have.

In order to achieve the above object, another embodiment of the present invention provides a product having a high hardness and low friction characteristics produced by the iron-based alloy coating method.

In an embodiment of the present invention, the hardness of the product may be a product having high hardness and low friction characteristics, characterized in that 1450 HV to 2400 HV.

In an embodiment of the present invention, the friction coefficient of the product may be a product having a high hardness and low friction characteristics, characterized in that 0.3 to 0.4.

According to the present invention having the configuration as described above, it is possible to produce an impregnated carbonized layer using a screen plasma on the iron-based alloy chromation by pack cementation.

In addition, according to the present invention, by using the screen in a double structure in the screen plasma, glow discharge can be formed around the screen at a high density, so that the inside of the vacuum chamber can be sufficiently raised to the process temperature without a heater.

In addition, according to the present invention, the precipitated carbonization process may not be inhibited by removing the chromium-based oxide film present on the iron-based alloy using the ion cleaning process in the screen plasma process.

In addition, according to the present invention, the product manufactured by the iron-based alloy coating method has a hardness value of 1450 HV or more hardness, it may have a characteristic that the friction coefficient can be lowered to 0.4 or less.

The effects of the present invention are not limited to the above-described effects, but should be understood to include all the effects deduced from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a cross-sectional view showing a conventional screen plasma apparatus.

2 is a cross-sectional view showing a screen plasma apparatus according to an embodiment of the present invention.

3 is a perspective view of a dual screen according to an embodiment of the present invention.

FIG. 4 is a graph showing X-ray diffraction patterns of SUJ2 having a chromium-based coating layer and a precipitated carbonization layer according to an embodiment of the present invention.

FIG. 5 is a graph showing X-ray diffraction patterns of SUJ2 having a chromium-based coating layer and a carburized layer according to an embodiment of the present invention.

FIG. 6 is a graph showing X-ray diffraction patterns of SUS316 having a chromium-based coating layer and a precipitated carbonization layer according to an embodiment of the present invention.

7 is a graph illustrating X-ray diffraction patterns of SUS316 having a chromium-based coating layer and a carburized layer according to an embodiment of the present invention.

8 is an image showing a cross-sectional shape of Preparation Example 1 (SUJ2-Cr-SPNC) according to an embodiment of the present invention.

9 is a graph showing the element content according to the depth of Preparation Example 1 (SUJ2-Cr-SPNC) according to an embodiment of the present invention.

10 is an image showing a cross-sectional shape of Preparation Example 2 (SUJ2-Cr-Fe-SPNC) according to an embodiment of the present invention.

11 is a graph showing the element content according to the depth of Preparation Example 2 (SUJ2-Cr-Fe-SPNC) according to an embodiment of the present invention.

12 is an image showing a cross-sectional shape of Preparation Example 3 (SUJ2-Cr-Fe-V-SPNC) according to an embodiment of the present invention.

13 is a graph showing the element content according to the depth of Preparation Example 3 (SUJ2-Cr-Fe-V-SPNC) according to an embodiment of the present invention.

14 is an image showing a cross-sectional shape of Comparative Example 1 (SUJ2-Cr-SPC) according to an embodiment of the present invention.

15 is a graph showing the element content according to the depth of Comparative Example 1 (SUJ2-Cr-SPC) according to an embodiment of the present invention.

16 is an image showing a cross-sectional shape of Comparative Example 4 (SUJ2-Cr-Fe-SPC) according to an embodiment of the present invention.

17 is a graph showing the element content according to the depth of Comparative Example 4 (SUJ2-Cr-Fe-SPC) according to an embodiment of the present invention.

18 is an image showing a cross-sectional shape of Comparative Example 5 (SUJ2-Cr-Fe-V-SPC) according to an embodiment of the present invention.

19 is a graph showing the element content according to the depth of Comparative Example 5 (SUJ2-Cr-Fe-V-SPC) according to an embodiment of the present invention.

20 is an image showing a cross-sectional shape of Preparation Example 4 (SUS316-Cr-SPNC) according to an embodiment of the present invention.

21 is a graph showing the element content according to the depth of Preparation Example 4 (SUS316-Cr-SPNC) according to an embodiment of the present invention.

22 is an image showing a cross-sectional shape of Preparation Example 5 (SUS316-Cr-Fe-SPNC) according to an embodiment of the present invention.

23 is a graph showing the element content according to the depth of Preparation Example 5 (SUS316-Cr-Fe-SPNC) according to an embodiment of the present invention.

24 is an image showing a cross-sectional shape of Preparation Example 6 (SUS316-Cr-Fe-V-SPNC) according to an embodiment of the present invention.

25 is a graph showing the element content according to the depth of Preparation Example 6 (SUS316-Cr-Fe-V-SPNC) according to an embodiment of the present invention.

Figure 26 is an image showing the cross-sectional shape of Comparative Example 6 (SUS316-Cr-SPC) according to an embodiment of the present invention.

27 is a graph showing the element content according to the depth of Comparative Example 6 (SUS316-Cr-SPC) according to an embodiment of the present invention.

28 is an image showing a cross-sectional shape of Comparative Example 7 (SUS316-Cr-Fe-SPC) according to an embodiment of the present invention.

29 is a graph showing the element content according to the depth of Comparative Example 7 (SUS316-Cr-Fe-SPC) according to an embodiment of the present invention.

30 is an image showing a cross-sectional shape of Comparative Example 8 (SUS316-Cr-Fe-V-SPC) according to an embodiment of the present invention.

31 is a graph showing the element content according to the depth of Comparative Example 8 (SUS316-Cr-Fe-V-SPC) according to an embodiment of the present invention.

32 is a graph measuring the coefficient of friction of Preparation Example 1 (SUJ2-Cr-SPNC) according to an embodiment of the present invention.

33 is a graph measuring the coefficient of friction of Preparation Example 2 (SUJ2-Cr-Fe-SPNC) according to an embodiment of the present invention.

34 is a graph illustrating a friction coefficient of Preparation Example 3 (SUJ2-Cr-Fe-V-SPNC) according to an embodiment of the present invention.

35 is a graph illustrating a friction coefficient of Comparative Example 1 (SUJ2-Cr-SPC) according to an embodiment of the present invention.

36 is a graph illustrating a friction coefficient of Comparative Example 4 (SUJ2-Cr-Fe-SPC) according to an embodiment of the present invention.

37 is a graph illustrating a friction coefficient of Comparative Example 5 (SUJ2-Cr-Fe-V-SPC) according to an embodiment of the present invention.

38 is a graph illustrating a friction coefficient of Comparative Example 2 (SUJ2-SPNC) according to an embodiment of the present invention.

39 is a graph illustrating a friction coefficient of Comparative Example 3 (SUJ2-SPC) according to an embodiment of the present invention.

40 is a graph measuring the coefficient of friction of Preparation Example 4 (SUS316-Cr-SPNC) according to an embodiment of the present invention.

41 is a graph measuring the coefficient of friction of Preparation Example 5 (SUS316-Cr-Fe-SPNC) according to an embodiment of the present invention.

42 is a graph illustrating a friction coefficient of Preparation Example 6 (SUS316-Cr-Fe-V-SPNC) according to an embodiment of the present invention.

43 is a graph illustrating a coefficient of friction of Comparative Example 6 (SUS316-Cr-SPC) according to an embodiment of the present invention.

44 is a graph illustrating a friction coefficient of Comparative Example 7 (SUS316-Cr-Fe-SPC) according to an embodiment of the present invention.

45 is a graph illustrating a friction coefficient of Comparative Example 8 (SUS316-Cr-Fe-V-SPC) according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of the invention. When a first component is expressed as being "connected (connected, contacted, coupled)" to a second component, it is said that the first component is "directly connected" to the second component or a third component. Means that it can be "indirectly connected" through. Singular expressions include plural expressions unless the context clearly indicates otherwise. Also, the terms "comprise" or "have" mean that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features, It does not mean that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is excluded.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms “comprise” or “have” are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, the iron-based alloy coating method will be described.

In an embodiment of the present invention, the iron-based alloy coating method is to form a chromium-based coating layer on the surface of the iron-based alloy using the pack cementation, and forming a nitriding carbonized layer using a screen plasma on the chromium-based coating layer It may include.

First, a chromium-based coating layer is formed on the iron-based alloy surface by using pack cementation.

In an embodiment of the present invention, the method for forming a chromium-based coating layer on the surface of the iron-based alloy using the pack cementation, the step of injecting the iron-based alloy and the pack mixture in the pack (pack), charging the pack in a vacuum chamber It may include a charging step, a heating step of heating the pack charged in the vacuum chamber, and a chromium-based coating layer forming step of forming a chromium-based coating layer on the iron alloy while the heating is maintained in the heating step.

In order to form a chromium-based coating layer on the surface of the iron-based alloy by pack cementation, the iron-based alloy and the pack mixture are first introduced into a pack.

Pack cementation is a method of manufacturing a coating layer in which a metal part to be processed is put into a pack mixture and heated at a high temperature for a predetermined time to form a surface layer on the metal part, and at the same time obtain a diffusion coating layer on the surface layer of the metal part.

Pack cementation of the present invention can be used as a method for forming a chromium-based coating layer on the surface of the iron-based alloy.

In an embodiment of the present invention, the iron-based alloy may include, but is not limited to, bearing steel or stainless steel.

The bearing steel is a high carbon chromium special steel, and the stainless steel is an alloy steel containing nickel and chromium to supplement the corrosion resistance of iron.

For example, the iron-based alloy of the present invention may be SUJ2 bearing steel or SUS316 stainless steel.

In an embodiment of the present invention, the pack mixture may include a chromium-based powder, an active agent and an inert agent.

In an embodiment of the present invention, the chromium-based powder of the pack mixture is chromium (Cr) powder, chromium (Cr) powder and iron (Fe) powder or chromium (Cr) powder, iron (Fe) powder and vanadium (V) It may include a powder, but is not limited thereto.

In general, since chromium metal exhibits excellent hardness, corrosion resistance, and lubricity, the chromium-based powder of the present invention is a reactant used when preparing a chromium-based coating layer, and may improve hardness, corrosion resistance, and lubricity of an iron-based alloy. It can be effective.

In addition, the active agent in the present invention may contribute to the formation of the chromium-based coating layer while reacting with the chromium powder to form a chromium-based coating layer, it may include a halogenated compound salt. Specifically, the halogenated compound salt may include potassium tetrafluoroborate (KBF ₄ ), ammonium chloride (NH ₄ Cl), fluoroammonium (NH ₄ F), fluorine sodium (NaF) or sodium chloride (NaCl), It is not limited to this.

For example, the active agent of the present invention may be potassium tetrafluoroborate (KBF ₄ ).

In addition, the inert agent of the present invention can prevent the sintering of the iron-based alloy in the process of forming the chromium-based coating layer. Specifically, the inert agent may include, but is not limited to, aluminum oxide (Al ₂ O ₃ ), silica (SiO ₂ ), silicon carbide (SiC) or chromium oxide (Cr ₂ O ₃ ). .

For example, the inert agent of the present invention may be aluminum oxide (Al ₂ O ₃ ).

In an embodiment of the present invention, the pack mixture may include 10.5 wt% to 52.9 wt% of the chromium-based powder, 0.1 wt% to 3 wt% of the active agent, and 47 wt% to 89.4 wt% of the inert agent, but It is not limited.

Here, the content of the chromium-based powder may include 10.5 wt% to 52.9 wt% of the total content of the pack mixture. When the content of the chromium-based powder is less than 10.5 wt%, the chromium-based coating layer may be formed too thin or the hardness value of the chromium-based coating layer may not reach the target value, which is not preferable. On the other hand, when the content of the chromium-based powder is more than 52.9 wt%, the chromium-based powder is agglomerated with the inert agent, and unnecessary substances are added to the surface of the iron-based alloy, which may cause excessive pores in the iron-based alloy, which is not preferable.

For example, the content of chromium metal powder of the present invention may be 30 wt%.

In addition, the content of the active agent may include 0.1 wt% to 3 wt% of the total content of the pack mixture. When the content of the activator is less than 0.1 wt% or more than 3 wt%, considering the content of the chromium-based powder described above, a non-uniform chromium-based coating layer is formed or staining occurs inside the chromium-based coating layer, so that the mechanical properties of the chromium-based coating layer The problem of deterioration may arise, which is undesirable.

For example, the content of the active agent of the present invention may be 1 wt%.

In addition, the content of the inert agent may include 47 wt% to 89.4 wt% of the total content of the pack mixture. If the content of the inert agent is less than 47 wt%, the penetration and diffusion of chromium, which will form the chromium-based coating layer, may not be achieved. If the content of the inert agent is more than 89.4 wt%, the formation of the chromium-based coating layer may be delayed. The mechanical properties of the chromium-based coating layer may be less than the target value is not preferable.

For example, the content of the inert agent of the present invention may be 69 wt%.

Next, after charging the pack in a vacuum chamber, the pack loaded in the vacuum chamber is heated.

Next, a chromium-based coating layer is formed on the iron-based alloy while the heating process is maintained.

In the present invention, the chromium-based coating layer may be formed of a chromium-based halogen compound gas by reacting chromium-based powder of the components constituting the pack mixture with the activator while the heating temperature is maintained, wherein the chromium-based halogen gas is the surface of the iron-based alloy Adsorbed on, it may be formed while penetrating and diffusing into the iron-based alloy.

In the present invention, the chromium-based coating layer is formed on the surface of the iron-based alloy by using pack cementation, and then an impregnated carbonization layer is formed on the chromium-based coating layer by using a screen plasma.

2 is a cross-sectional view showing a screen plasma apparatus according to an embodiment of the present invention. The screen plasma apparatus includes a vacuum chamber 10, a double screen 70, a vacuum pump 40, and a cathode power supply 50. With reference to FIG. 2, screen plasma immersion carbonization of the present invention is described.

In an embodiment of the present invention, the method of forming an immersion carbonization layer using the screen plasma on the chromium-based coating layer is charged with the iron-based alloy (2) coated with the chromium-based coating layer in the vacuum chamber 10 and the iron-based alloy Covering (2) with a double screen 70, an ion cleaning step of reducing the chromium-based oxide film present on the iron-based alloy 2 by injecting a first hydrogen gas into the vacuum chamber 10, the double Applying a process current to the screen 70, injecting a second hydrogen gas, nitrogen gas and hydrocarbon gas into the vacuum chamber 10 to generate a mixed plasma and the mixed plasma is formed on the surface of the iron-based alloy (2) It may include the step of coating on the chromium-based coating layer to form a precipitated carbonization layer.

First, the iron-based alloy (2) coated with a chromium-based coating layer is charged into the vacuum chamber 10 and the iron-based alloy (2) is covered with a double screen 70, and then the vacuum pump 40 is operated to operate the vacuum chamber ( 10) The atmosphere inside is formed at a vacuum level of 1 × 10 ^-3 Torr to 1 × 10 ^-1 Torr. At this time, the inner wall of the vacuum chamber 10 shows a positive (+) relative charge, and the double screen 70 shows a negative (-) relative charge, so that an electric field is formed between the inner wall of the vacuum chamber 10 and the double screen 70. Is generated.

If the vacuum degree of the vacuum chamber 10 is less than 1 × 10 ⁻¹ Torr, it is not preferable that impurities in the vacuum chamber 10 are not sufficiently removed, and impurities are sufficiently formed even if a vacuum atmosphere is formed within 1 × 10 ⁻³ Torr. Since it can be removed, creating a vacuum atmosphere above 1 × 10 ⁻³ Torr is undesirable because it is unnecessary in the process.

In the embodiment of the present invention, after loading the iron-based alloy (2) coated with the chromium-based coating layer in the pack cementation in the vacuum chamber 10, the iron-based alloy (2) is covered with a double screen (70).

3 is a perspective view of a dual screen 70 according to an embodiment of the present invention.

Referring to FIG. 3, the dual screen 70 is a screen used in a screen plasma process, and includes an outer cylinder 71 and an inner cylinder 72, and has a cylindrical structure with an open bottom.

In an embodiment of the present invention, the dual screen 70 may serve as an electrode for generating glow discharge in the vacuum chamber 10.

Next, a first hydrogen gas is injected into the vacuum chamber 10 to reduce the chromium-based oxide film present on the iron-based alloy 2, which is called ion cleaning.

In the ion cleaning method, applying the first current to the dual screen 70 to heat the vacuum chamber 10, injecting the first hydrogen into the vacuum chamber 10, the dual screen 70 ) To generate a hydrogen plasma around the double screen 70 and to reduce and remove the chromium-based oxide film present on the iron-based alloy 2).

First, when the first current is applied to the dual screen 70, the internal temperature of the vacuum chamber 10 is raised to 100 ° C.

In an embodiment of the present invention, when the vacuum chamber 10 is preheated to 100 ° C. by applying a first current, the vacuum chamber 10 is cooled from low to high temperature by using a high density glow generated between the screens. When the temperature change occurs, it is possible to prevent cracking due to thermal expansion, and oxygen and moisture may be discharged while burning the carbon inside the vacuum chamber 10.

In an embodiment of the present invention, the first current is 3 A to 5 A. The first current is applied to the dual screen 70 so that the intensity of the first current for heating the internal temperature of the vacuum chamber 10 to 100 ° C is preferably 3 A to 5 A.

For example, the first current may be 5 A.

Next, first hydrogen is injected into the vacuum chamber 10.

The first hydrogen of the present invention may be a gas source for generating a hydrogen plasma.

Next, a second current is applied to the dual screen 70 to generate a hydrogen plasma around the dual screen 20.

In the embodiment of the present invention, when a second current is applied to the dual screen 70, a glow discharge is generated between the outer cylinder 71 and the inner cylinder 72 of the dual screen 70, thereby generating the hydrogen plasma. May be collected in the space S existing between the outer cylinder 71 and the inner cylinder 72 of the dual screen 70. Accordingly, the density of the hydrogen plasma can be formed at a higher density than a single screen plasma apparatus. Therefore, the heating process may be performed to increase the temperature of the vacuum chamber 10 to the process temperature by using a glow formed on the screen with a very small amount of gas input and power without a separate external heater.

For example, the hydrogen plasma may comprise hydrogen plasma species including H _α , H _β or H _γ .

In an embodiment of the present invention, the second current is 5 A to 15 A. The second current may be applied to the dual screen 70 to heat the internal temperature of the vacuum chamber 10 to 250 ° C., and the intensity of the second current that may generate hydrogen plasma is preferably 5 A to 15 A.

For example, the first current may be 15 A.

In an embodiment of the present invention, the hydrogen plasma may be located in the center of the vacuum chamber by the force of the vacuum pump.

Next, the chromium oxide film present on the iron-based alloy 2 is reduced and removed.

In the present invention, the iron-based alloy 2 coated with a chromium-based coating layer by pack cementation may have a chromium-based oxide film formed on a surface thereof when contacted with external air before being charged into the vacuum chamber 10.

The chromium-based oxide film may be a cause of inhibiting the nitriding carbonization process, the corrosion resistance of the iron-based alloy may be improved, but there is a disadvantage in reducing the magnetic conductivity. Therefore, in the present invention, the hydrogen plasma located at the center of the vacuum chamber 10 may react with the chromium oxide film to reduce and remove the chromium oxide film.

In an embodiment of the present invention, the chromium-based oxide film may include chromium (Cr), chromium (Cr) and iron (Fe) or chromium (Cr), iron (Fe) and vanadium (V), but is not limited thereto. It is not intended to be.

Next, the ion cleaning process of the present invention, a process current is applied to the double screen 70, the second hydrogen gas, nitrogen gas and hydrocarbon gas is injected into the vacuum chamber 10 to generate a mixed plasma.

For example, the mixed plasma may be nitrogen plasma, hydrogen plasma and hydrocarbon plasma.

In an embodiment of the present invention, the process current may be 20 A to 30 A. Process current may be applied to the dual screen 70 to heat the internal temperature of the vacuum chamber 10 to 450 ℃ to 550 ℃ to generate the intensity of the process current is preferably 20 A to 30 A. .

In the present invention, when the second hydrogen gas and the hydrocarbon gas are injected into the vacuum chamber 10, the second hydrogen gas and the hydrocarbon gas are formed in the vacuum chamber 10 in a high temperature and a vacuum atmosphere, so that the vacuum chamber 10 As soon as it is injected, it is plasmaized by the energy of temperature and pressure, and the hydrogen plasma and hydrocarbon plasma are concentrated around the double screen 70.

The hydrocarbon gas may include CH ₄ or C ₂ H ₂ , and the amount of 1 sccm to 10 sccm gas may be pulse-injected by repeating the injection section and the stop section.

In the embodiment of the present invention, the ionization rate of the hydrocarbon gas can be increased by pulse injection of the hydrocarbon gas, and the diffusion layer of carbon and nitrogen can be formed deeper than the same time zone.

For example, the hydrogen plasma may include hydrogen plasma species including H _α , H _β, or H _γ , and the hydrocarbon gas may be pulse injected by repeating a section in which the gas is injected for 2 seconds and stopped for 5 seconds.

In the present invention, the nitrogen gas has a relatively high ionization energy than the hydrogen gas, so that the plasma is not smoothed. However, the plasma plasma hydrogenated already collides with the nitrogen gas to smoothly generate the nitrogen plasma. The hydrogen plasma may improve the fluidity of the nitrogen plasma.

For example, the nitrogen plasma of the present invention may include nitrogen species including N ⁺ , N, N ₂ ⁺ or NH ₃ .

In an embodiment of the present invention, the content ratio of nitrogen gas to hydrogen gas may be 1: 3 to 4: 1. More preferably, when the iron-based alloy is a bearing steel, the content ratio of nitrogen gas to hydrogen gas is 1: 3 to 1: 2, and in the case of stainless steel, the content ratio of nitrogen gas to hydrogen gas is 1: 1 to 4: 1. desirable.

In the case of the bearing steel, since it is more difficult to diffuse nitrogen into the base material than the stainless steel, it is preferable to induce nitrogen diffusion by increasing the content of hydrogen gas to improve the fluidity of the nitrogen plasma. Therefore, a content ratio of nitrogen gas to hydrogen gas of 1: 3 to 1: 2 in which the content of hydrogen is higher than the content of nitrogen is preferable. In addition, in the case of the stainless steel, it is an iron-based alloy that is advantageous to contain nitrogen, the content of nitrogen gas to hydrogen gas of 1: 1 to 4: 1 where the content of nitrogen is higher than the content of hydrogen in order to perform nitrogen diffusion more densely Rain is preferred.

Finally, the mixed plasma is coated on the chromium-based coating layer formed on the surface of the iron-based alloy (2) to form an precipitated carbonization layer.

In the embodiment of the present invention, the nitrogen plasma and hydrocarbon plasma are located in the center of the vacuum chamber 10 under the influence of the vacuum pump 40, the nitrogen plasma and hydrocarbon plasma is sucked gas by the vacuum pump 40 In order to penetrate the iron-based alloy (2) coated with the chromium-based coating layer located in the center of the vacuum chamber 10 in the direction of the impregnated carbonization layer may be formed on the surface of the iron-based alloy (2).

Hereinafter, a product having high hardness and low friction characteristics coated by the iron-based coating method will be described.

In an embodiment of the present invention, the hardness of the product may be 1450 HV to 2400 HV.

Conventional iron-based alloy hardness of about 800 HV, the present invention can increase the hardness of the iron-based alloy using a pack cementation and screen plasma process. Therefore, the hardness of the product based on the iron-based alloy prepared in the above process may be 1450 HV to 2400 HV.

In an embodiment of the present invention, the friction coefficient of the product may be 0.3 to 0.4.

The present invention can reduce the coefficient of friction of the iron-based alloy using a pack cementation and screen plasma process. Therefore, the coefficient of friction of the product based on the iron-based alloy prepared in the above process may be 0.3 to 0.4.

Hereinafter, the preparation examples and experimental examples of the present invention. However, these preparation examples and experimental examples are intended to explain the configuration and effects of the present invention in more detail, and the scope of the present invention is not limited thereto.

[Production Example 1]

After forming a chromium ( Cr ) coating layer on the bearing steel (SUJ2) iron -based alloy, manufacturing a ferrous alloy (SUJ2-Cr-SPNC) coated with a screen plasma nitro-carburizing (SPNC) layer on the coating layer

1-1. Preparation of Chrome Coating Layer Using Pack Cementation

After preparing SUJ2 as an iron base material, a pack mixture including 30 wt% chromium powder, 1 wt% potassium tetrafluoroborate and 69 wt% aluminum oxide was prepared. Next, SUJ2 and the pack mixture were put into a pack, the pack was charged into a vacuum chamber, and the inside of the vacuum chamber was evacuated to a vacuum of 1 Torr. Next, purging was performed by supplying argon gas three times in the vacuum chamber, and lowering the flow rate of the supplied argon gas to maintain the inside of the vacuum chamber at 1 atmosphere. Next, the chromium coating layer was manufactured by maintaining the temperature inside the vacuum chamber at 950 ° C. for 10 hours.

1-2. Manufacture of nitriding carbide layer on SUJ2 with chromium coating layer using screen plasma

After charging the SUJ2 having the chromium coating layer prepared in a vacuum chamber, the charged SUJ2 is covered with a double screen, and the degree of vacuum in the vacuum chamber is maintained at a level of 5 × 10 ⁻³ Torr for 30 minutes. Thereafter, 500 sccm of the first hydrogen gas is added to the vacuum chamber to maintain the vacuum at 0.1 Torr. Next, a current of 5 A is applied to the screen and a high density glow generated between the screens is used to preheat the vacuum chamber to prevent cracking due to thermal expansion when a temperature change occurs from low to high temperatures. Next, a current of 15 A is applied for 30 minutes to raise the temperature inside the vacuum chamber to 250 ° C. 20 A current was continuously applied to the chamber to raise the temperature inside the vacuum chamber to 450 ° C., and then 250 sccm of nitrogen gas and 350 sccm of second hydrogen gas were added for 1 hour while the same current was applied. Hydrocarbon gas was injected for 2 hours after the injection of 5 sccm for 2 seconds and then pulsed at intervals of 5 seconds to prepare an impregnated carbonized layer on SUJ2 having a chromium coating layer.

[Production Example 2]

After forming a chromium-iron ( Cr- Fe) coating layer on the bearing steel ferroalloy, an iron-based alloy (SUJ2-Cr-Fe-SPNC) coated with a carbonization layer on the coating layer was manufactured.

Except for using chromium and iron powder instead of chromium powder in Preparation Example 1 was prepared in the carbonized layer on the SUJ2 chromium-iron coating layer prepared.

[Production Example 3]

After forming a chromium-iron-vanadium ( Cr- Fe-V) coating layer on the bearing steel ferroalloy, an iron- based alloy (SUJ2-Cr-Fe-V-SPNC) coated with a carbonization layer on the coating layer was manufactured.

Except for using chromium, iron and vanadium powder instead of the chromium powder in Preparation Example 1 was prepared in the carbonized layer on the SUJ2 chromium-iron-vanadium coating layer prepared.

[Production Example 4]

After the chromium coating layer is formed on the stainless steel (SUS316) iron alloy, an iron alloy (SUS316-Cr-SPNC) coated with a carbonization layer on the coating layer is manufactured.

Except for using a stainless steel instead of the bearing steel in Preparation Example 1 was prepared in the carbonized layer on the SUS316 chromium coating layer prepared by the same conditions.

Production Example 5

After the chromium-iron coating layer was formed on the stainless steel iron alloy, an iron-based alloy (SUS316-Cr-Fe-SPNC) coated with a carbonization layer on the coating layer was manufactured.

Except for using the stainless steel instead of the bearing steel in Preparation Example 1, and chromium and iron powder instead of chromium powder was carried out under the same conditions to prepare a immersion carbonized layer on SUS316 chromium-iron coating layer prepared.

[Manufacture example 6]

After the chromium-iron-vanadium coating layer was formed on the stainless steel iron alloy, an iron- based alloy (SUS316-Cr-Fe-V-SPNC) coated with a carbonization layer on the coating layer was manufactured.

Except for using the stainless steel instead of the bearing steel in Preparation Example 1, chromium, iron and vanadium powder was carried out under the same conditions except that the chromium-iron-vanadium coating layer prepared in the SUS316 to produce a carbonized carbon layer It was.

Comparative Example 1

After the formation of the chromium coating layer on an iron-based alloy bearing steel, carburizing screen on the coating layer (SPNC, Screen Plasma Carburizing) layer is an iron-based alloy (SUJ2-Cr-SPC) coating prepared

A carburized layer was prepared in SUJ2 in which a chromium coating layer was prepared under the same conditions except that nitrogen gas was not used and the hydrocarbon gas was continuously injected in Preparation Example 1.

Comparative Example 2

Manufacture of ferrous alloy (SUJ2-SPNC) coated with a hardened carbide layer on bearing steel ferrous alloy

Except not performing the pack cementation in Preparation Example 1 was carried out under the same conditions to prepare a carbonized carbon layer in SUJ2.

Comparative Example 3

Manufacturing ferroalloy (SUJ2-SPC) coated with carburized layer on bearing steel ferroalloy

The carburized layer was prepared in SUJ2 under the same conditions except that the pack cementation was not performed in Preparation Example 1, and the nitrogen gas was not used when the screen plasma was used and the hydrocarbon gas was continuously injected.

[Comparative Example 4]

After forming a chromium-iron coating layer on the bearing steel iron alloy, the iron-based alloy (SUJ2-Cr-Fe-SPC) manufactured by coating a carburizing layer on the coating layer

The carburized layer was prepared in SUJ2 in which the chromium-iron coating layer was prepared under the same conditions except that nitrogen gas was not used and the hydrocarbon gas was continuously injected in Preparation Example 2.

[Comparative Example 5]

After forming a chromium-iron-vanadium coating layer on the bearing steel iron alloy, the iron- based alloy (SUJ2-Cr-Fe-V-SPC) having a carburized layer coated on the coating layer was manufactured.

In Example 3, a carburized layer was prepared in SUJ2 in which a chromium-iron-vanadium coating layer was prepared under the same conditions except for continuously injecting a hydrocarbon gas without using nitrogen gas.

Comparative Example 6

Producing stainless steel after forming the chromium coating on the iron-based alloy, an iron-based alloy needle carbide layer is coated (SUS316-Cr-SPC) on the coating layer

The carburized layer was prepared in SUS316, in which the chromium coating layer was prepared under the same conditions except that nitrogen gas was not used and the hydrocarbon gas was continuously injected in Preparation Example 4.

Comparative Example 7

After the chromium-iron coating layer was formed on the stainless steel iron alloy, an iron-based alloy (SUS316-Cr-Fe-SPC) having a carburized layer coated on the coating layer was manufactured.

The carburized layer was prepared in SUS316, in which the chromium-iron coating layer was manufactured under the same conditions except that nitrogen gas was not used and the hydrocarbon gas was continuously injected in Preparation Example 5.

Comparative Example 8

After the chromium-iron-vanadium coating layer was formed on the stainless steel iron alloy, an iron- based alloy (SUS316-Cr-Fe-SPC) having a carburized layer coated thereon was manufactured.

In Example 6, a carburized layer was prepared on SUS316 in which a chromium-iron-vanadium coating layer was prepared under the same conditions except for continuously injecting a hydrocarbon gas without using nitrogen gas.

Experimental Example 1

Crystal Structure Analysis of SUJ2-Chromium Coating Layer-SPNC and SUJ2-Chromium Coating Layer-SPC

X-ray diffraction analysis was performed to confirm the crystal structure of SUJ2 in which the coating layer prepared by pack cementation and screen plasma is present.

4 is a manufacturing example 1 (SUJ2-Cr-SPNC) coated with an immersion carbide layer on SUJ2 coated with a chromium-based coating layer by pack cementation, Preparation Example 2 (SUJ2-Cr-Fe-SPNC) and Preparation Example 3 (SUJ2 X-ray diffraction patterns of -Cr-Fe-V-SPNC). 5 is Comparative Example 1 (SUJ2-Cr-SPC), Comparative Example 4 (SUJ2-Cr-Fe-SPC) and Comparative Example 5 (coated with a carburized layer on SUJ2 coated with a chromium-based coating layer by pack cementation). X-ray diffraction patterns of SUJ2-Cr-Fe-V-SPC).

4 to 5, the SUJ2 having the precipitated carbonization layer formed by the screen plasma has a different crystal structure from that of the SUJ2 having the carbonaceous layer formed therein, and the crystal structure differs depending on the chromium-based material for preparing the coating layer by pack cementation. It confirmed that it represents. As a result, it can be determined that various desired crystal phases can be produced by using pack cementation and screen plasma. In addition, it can be determined that the pack cementation and the screen plasma can be performed together in a process for manufacturing a coating layer on SUJ2.

Experimental Example 2

Crystal Structure Analysis of SUS316-Chrome-based Coating Layer-SPNC and SUS316-Chrome-based Coating Layer-SPC

X-ray diffraction analysis was performed to confirm the crystal structure of SUS316 in which the coating layer prepared by pack cementation and screen plasma is present.

6 is a manufacturing example 4 (SUS316-Cr-SPNC), Manufacture Example 5 (SUS316-Cr-Fe-SPNC) and Manufacture Example 6 (SUS316) coated with an immersion carbide layer on the SUS316 coated with a chromium-based coating layer by the pack cementation X-ray diffraction patterns of -Cr-Fe-V-SPNC). In addition, Figure 7 is Comparative Example 6 (SUS316-Cr-SPC), Comparative Example 7 (SUS316-Cr-Fe-SPC) and Comparative Example 8 ( X-ray diffraction patterns of SUS316-Cr-Fe-V-SPC).

Referring to FIGS. 6 to 7, the SUS316 having the carbonaceous layer formed with the screen plasma has a different crystal structure from that of the SUS316 having the carburized layer, and has a different crystal structure depending on the chromium-based material for preparing the coating layer by pack cementation. It confirmed that it represents. As a result, it can be determined that various desired crystal phases can be produced by using pack cementation and screen plasma. In addition, it can be determined that the pack cementation and the screen plasma can be performed together in a process for manufacturing a coating layer on SUS316.

Experimental Example 3

Analysis of the cross-sectional shape and elemental content of the coating layer of SUJ2 including the coating layer made of pack cementation and screen plasma

In order to analyze the element content according to the cross-sectional shape and depth of the SUJ2 having a coating layer, a sample having a cross section was prepared by mounting SUJ2 including the coating layer and etching with hydrochloric acid. The cross-sectional shape of the sample was analyzed using an optical microscope and elemental content analysis was performed by glow discharge optical emission spectrometry (GD-OES).

8 is an image showing the cross-sectional shape of Preparation Example 1 (SUJ2-Cr-SPNC), Figure 9 is a graph showing the element content according to the depth of Preparation Example 1. 10 is an image showing the cross-sectional shape of Preparation Example 2 (SUJ2-Cr-Fe-SPNC), Figure 11 is a graph showing the element content according to the depth of Preparation Example 2. In addition, Figure 12 is an image showing the cross-sectional shape of Preparation Example 3 (SUJ2-Cr-Fe-V-SPNC), Figure 13 is a graph showing the element content according to the depth of Preparation Example 3.

8 to 13, it was confirmed that the content of nitrogen, carbon and chromium elements 5 wt% or more at the outermost surface of Preparation Example 1 in which the chromium coating layer and the precipitated carbonization layer are present, and the thickness of the chromium coating layer is about It confirmed that it was 5 micrometers. In addition, it was confirmed that the coating layer coated on SUJ2 was formed uniformly. In Preparation Example 2 and Example 3 containing iron (Fe) in the chromium-based coating layer formed by pack cementation, the iron (Fe) content was present at the outermost surface of SUJ2, but the thickness thereof was very thin. And it was confirmed that the element of carbon also exists about 5 wt%. Since the depth of 1 μm from the outermost surfaces of the coating layers of Preparation Examples 2 and 3, the amount of chromium element is higher than the other elements, it was confirmed that the chromium coating layer is present in more than 30 μm. In addition, Preparation Example 3 confirmed that the vanadium coating layer is present in 25 μm or more.

14 is an image showing the cross-sectional shape of Comparative Example 1 (SUJ2-Cr-SPC), Figure 15 is a graph showing the element content of the coating layer of Comparative Example 1. In addition, Figure 16 is an image showing the cross-sectional shape of Comparative Example 4 (SUJ2-Cr-Fe-SPC), Figure 17 is a graph showing the element content of the coating layer of Comparative Example 4. In addition, Figure 18 is an image showing the cross-sectional shape of Comparative Example 5 (SUJ2-Cr-Fe-V-SPC), Figure 19 is a graph showing the element content of the coating layer of Comparative Example 5.

8 to 19, it was confirmed that the cross-sectional shapes of SUJ2 having the nitriding carbonization layer and SUJ2 having the nitriding carbide layer formed by screen plasma were similar. In addition, the element content of the coating layer of Preparation Example 1 and Comparative Example 1 or Preparation Example 2 and Comparative Example 4 was confirmed at a similar level except for carbon. However, in Comparative Example 5, elements of chromium and vanadium existed to a deeper depth of the coating layer than Preparation Example 3, and the depth thereof was confirmed to be 35 μm or more.

Based on these results, when chromium and iron or chromium, iron or vanadium are mixed and coated with chromium-based materials in the pack cementation, the depth of the chromizing SUJ2 becomes deeper, and the precipitated carbon layer formed by screen plasma or The thickness of the carburized layer may be determined to be about 1 μm.

Experimental Example 4

However element content analysis of the surface shape and the coating layer of the coating layer made of SUS316 including a pack cementation and plasma screen

In order to analyze the element content according to the cross-sectional shape and depth of the SUS316 formed with the coating layer was mounted (SUS316) containing the coating layer (etched) and then etched with aqua regia to prepare a sample with the cross-section exposed. The cross-sectional shape of the sample was analyzed using an optical microscope and elemental content analysis was performed by glow discharge optical emission spectrometry (GD-OES).

20 is an image showing the cross-sectional shape of Preparation Example 4 (SUS316-Cr-SPNC), Figure 21 is a graph showing the element content according to the depth of Preparation Example 4. 22 is an image showing the cross-sectional shape of Preparation Example 5 (SUS316-Cr-Fe-SPNC), Figure 23 is a graph showing the element content according to the depth of Preparation Example 5. 24 is an image showing the cross-sectional shape of Preparation Example 6 (SUS316-Cr-Fe-V-SPNC), Figure 25 is a graph showing the element content according to the depth of Preparation Example 6.

20 to 25, it was confirmed that the content of the elemental chromium 20 wt% or more in the outermost surface of Preparation Example 4 in which the chromium coating layer and the precipitated carbonization layer of Preparation Example 4 is present, the thickness of the chromium coating layer is 60 It confirmed that it was more than micrometer. In addition, it was confirmed that the coating layer coated on the SUS316 is formed uniformly. In Preparation Example 5 in which iron (Fe) is included in the chromium-based coating layer formed by pack cementation, iron (Fe) is present at the outermost surface of SUS316, but the thickness thereof is very thin. 5 wt% was confirmed to exist. After the depth of 1 μm from the outermost surface of the coating layer of Preparation Example 5, the amount of chromium element was higher than that of other elements, and it was confirmed that the chromium coating layer was present at 60 μm or more. In addition, in Preparation Example 5, the vanadium coating layer was present at 70 wt% or more at the outermost surface, and it was confirmed that a coating layer having a uniform content of elements was formed after the depth of 10 μm from the outermost surface of the coating layer of Preparation Example 5.

26 is an image showing the cross-sectional shape of Comparative Example 6 (SUS316-Cr-SPC), Figure 27 is a graph showing the element content of the coating layer of Comparative Example 6. In addition, Figure 28 is an image showing the cross-sectional shape of Comparative Example 7 (SUS316-Cr-Fe-SPC), Figure 29 is a graph showing the element content of the coating layer of Comparative Example 7. In addition, Figure 30 is an image showing the cross-sectional shape of Comparative Example 8 (SUS316-Cr-Fe-V-SPC), Figure 31 is a graph showing the element content of the coating layer of Comparative Example 8.

20 to 31, it was confirmed that the cross-sectional shape of the SUS316 in which the precipitated carbonized layer or the carbonized layer was formed by the screen plasma was similar. In addition, the element content of the coating layer of Preparation Example 4 and Comparative Example 6, Preparation Example 5 and Comparative Example 7 or Preparation Example 6 and Comparative Example 8 was confirmed at a similar level except for carbon.

Based on these results, when chromium and iron or chromium, iron or vanadium are mixed and coated with chromium-based materials in pack cementation, the depth of SUS316 to be chromized becomes deeper, and the precipitated carbon layer formed by screen plasma or The thickness of the carburized layer may be determined to be about 1 μm.

Experimental Example 5

Friction Coefficient Analysis of SUJ2 with Coatings Made by Pack Cementation and Screen Plasma

The friction coefficient of the coating layer was a ball-on-disk method for measuring the relative friction coefficient between the product and the hard bearing ball. The ball-on-disk method uses a 6 mm diameter STB 2 ball. A linear velocity of 10 mm / sec and 1N load is used, and the relative humidity is a method of measuring the coefficient of friction in a constant temperature and humidity chamber to maintain a 50% wear condition.

32 is a graph measuring the coefficient of friction of Preparation Example 1 (SUJ2-Cr-SPNC), Figure 33 is a graph measuring the coefficient of friction of Preparation Example 2 (SUJ2-Cr-Fe-SPNC), Figure 34 is a graph This is a graph measuring the friction coefficient of Example 3 (SUJ2-Cr-Fe-V-SPNC). 35 is a graph measuring the friction coefficient of Comparative Example 1 (SUJ2-Cr-SPC), FIG. 36 is a graph measuring the friction coefficient of Comparative Example 4 (SUJ2-Cr-Fe-SPC), and FIG. 37 is a comparison. It is a graph which measured the friction coefficient of Example 5 (SUJ2-Cr-Fe-V-SPC).

32 to 37, the coefficient of friction of Preparation Example 1 in which the chromium coating layer and the carbonization layer are present is 0.5, and the coefficient of friction of Comparative Example 2 in which the chromium coating layer and the carbonization layer is present is 0.6. In addition, the friction coefficient of Preparation Example 2 in which the chromium-iron coating layer and the precipitated carbonization layer is 0.6 is 0.6, and the friction coefficient of Comparative Example 4 in which the chromium-iron coating layer and the carbonization layer is present is 0.7. In addition, the coefficient of friction of Preparation Example 3, in which the chromium-iron-vanadium coating layer and the precipitated carbonization layer are present is 0.4, and the coefficient of friction of Comparative Example 5, in which the chromium-iron-vanadium coating layer and the carbide-carburized layer is present, is 0.6.

As a result, it was confirmed that the friction coefficient of Preparation Example 3 in which the chromium-iron-vanadium coating layer and the precipitated carbonization layer were formed showed lower values than Preparation Examples 1 and 2. In addition, it was confirmed that Preparation Example 1, Preparation Example 2, and Preparation Example 3 in which the carbonaceous carbide layer was formed had a lower coefficient of friction than Comparative Examples 1, 4, and 5, in which the carbonization layer without nitrogen was formed. These results can be determined that the friction coefficient is lowered when the coating is mixed with chromium and iron or chromium, iron or vanadium in the chromium-based material in the pack cementation. In particular, SUJ2, which has an impregnated carbonized layer, penetrates nitrogen and carbon in the screen plasma, and penetrates only carbon, thereby lowering the coefficient of friction than SUJ2, which has formed a carburized layer. It can be judged that it is preferable to form an precipitated carbonized layer.

 FIG. 38 is a graph illustrating a friction coefficient of Comparative Example 2 (SUJ2-SPNC) in which an impregnated carbon layer was formed of screen plasma without performing pack cementation, and FIG. 39 is carburized with screen plasma without performing pack cementation. It is a graph which measured the friction coefficient of the comparative example 3 (SUJ2-SPC) which formed the flower layer.

32 and 38 to 39, the frictional coefficient of Comparative Example 2 in which the nitriding carbonization layer was formed by screen plasma without performing pack cementation was 0.6, and the comparative example 3 in which the carbonization layer except for nitrogen was formed was The coefficient of friction is also 0.6.

As a result, the SUJ2 having only the screen plasma and the precipitated carbonized layer or the carbonized layer may be determined to have a higher friction coefficient than the SUJ2 having both the pack cementation and the screen plasma. These results can be determined that it is desirable to perform both the pack cementation and the screen plasma in order to reduce the friction coefficient of SUJ2.

Experimental Example 6

Friction coefficient analysis of SUS316 including a coating layer made of a pack cementation and plasma screen

The friction coefficient of the coating layer was a ball-on-disk method for measuring the relative friction coefficient between the product and the high hardness stainless steel ball. The ball-on-disk method uses a 6 mm diameter STS 316 ball. A linear velocity of 10 mm / sec and 1N load is used, and the relative humidity is a method of measuring the coefficient of friction in a constant temperature and humidity chamber to maintain a 50% wear condition.

40 is a graph measuring the coefficient of friction of Preparation Example 4 (SUS316-Cr-SPNC), Figure 41 is a graph measuring the coefficient of friction of Preparation Example 5 (SUS316-Cr-Fe-SPNC), Figure 42 It is a graph which measured the friction coefficient of Example 6 (SUS316-Cr-Fe-V-SPNC). FIG. 43 is a graph measuring friction coefficient of Comparative Example 6 (SUS316-Cr-SPC), FIG. 44 is a graph measuring friction coefficient of Comparative Example 7 (SUS316-Cr-Fe-SPC), and FIG. 45 is a comparison. It is a graph which measured the friction coefficient of Example 8 (SUS316-Cr-Fe-V-SPC).

40 to 45, the coefficient of friction of Preparation Example 4 in which the chromium coating layer and the carbonization layer are present is 0.6, and the coefficient of friction of Comparative Example 6 in which the chromium coating layer and the carbonization layer is present is 0.6. In addition, the friction coefficient of Preparation Example 5 in which the chromium-iron coating layer and the precipitated carbonization layer are 0.4 is 0.4, and the friction coefficient of Comparative Example 7 in which the chromium-iron coating layer and the carbonization layer is present is 0.6. In addition, the coefficient of friction of Preparation Example 6 in which the chromium-iron-vanadium coating layer and the precipitated carbonization layer are present is 0.7, and the coefficient of friction of Comparative Example 8 in which the chromium-iron-vanadium coating layer and the carbonization layer is present is 0.7.

As a result, it was confirmed that the friction coefficient of Preparation Example 5 in which the chromium-iron coating layer and the precipitated carbonization layer were formed showed lower values than Preparation Examples 4 and 6. In addition, it was confirmed that Preparation Example 5 in which the carbonaceous carbide layer was formed had a lower friction coefficient than Comparative Example 7 in which the carbonaceous carbide layer except for nitrogen was formed. In Preparation Example 4 and Comparative Example 6 or Preparation Example 6 and Comparative Example 8 including a chromium coating layer and a chromium-iron-vanadium coating layer, it was confirmed that there is no difference in the friction coefficient depending on the formation of the carbonized layer and the carburized layer.

Such a result may be determined that the friction coefficient is lowered when the chromium-based material is mixed and coated with the chromium-based material in the pack cementation. In particular, SUS316 in which an impregnated carbonization layer is formed by penetrating nitrogen and carbon on the chromium-iron coating layer in a screen plasma infiltrates only carbon, thereby lowering the coefficient of friction than SUS316 in which the carbonization layer is formed. And it can be judged that it is preferable to penetrate all carbon to form an impregnated carbonization layer.

Experimental Example 7

Hardness analysis of SUJ2 with a coating layer made of pack cementation and screen plasma

In order to analyze the hardness of SUJ2 having a coating layer, the hardness was measured using a micro-Vickers hardness measurement method. Micro Vickers hardness measurement method is a method of measuring the hardness of the material by calculating the size engraved by applying a certain load to the material to be measured with a pyramidal diamond indenter.

Table 1 is a table showing the hardness values of the embodiments subjected to the pack cementation and screen plasma using the SUJ2 iron alloy, or the screen plasma only.

Example	Hardness (HV)	Example	Hardness (HV)
Preparation Example 1	2377	Comparative Example 2	1133
Comparative Example 1	2397	Comparative Example 3	705

Referring to Table 1, the pack cementation and the screen plasma were performed together with the pack cementation and the screen plasma rather than Comparative Example 2, which produced the precipitated carbon layer using screen plasma, and Comparative Example 3, which prepared the carburized layer, without pack cementation. The hardness value of the manufacture example 1 which prepared the and the comparative example 1 which produced the carburized layer improved.

Based on these results, it can be determined that when the pack cementation and the screen plasma are performed together, the hardness of SUJ2 is improved compared to when only the screen plasma is performed.

Experimental Example 8

Hardness analysis of SUS316 with coating layer made of pack cementation and screen plasma

Hardness was measured using the same method as Experimental Example 7 to analyze the hardness of SUS316 having a coating layer.

Table 2 is a table showing the hardness values of the embodiments subjected to the pack cementation and screen plasma using the SUS316 iron-based alloy.

Example	Hardness (HV)	Example	Hardness (HV)
Preparation Example 4	1510	Comparative Example 6	1674
Preparation Example 5	1499	Comparative Example 7	1853
Preparation Example 6	1496	Comparative Example 8	1156

Referring to Table 2, it was confirmed that when the nitriding or carburizing layer was formed by using screen plasma after pack cementation, the hardness value was higher than 800 HV, which is the hardness value of general SUS316.

Based on these results, it can be determined that the hardness of SUS316 is improved when the pack cementation and the screen plasma are performed together.

Therefore, referring to Preparation Examples and Experimental Examples of the present invention, it is possible to prepare a chromium-based coating layer and an immersion carbonization layer on an iron-based alloy using pack cementation and screen plasma. In addition, when the iron-based alloy is used as SUS316, the chromated chromium-based coating layer may be formed to a thickness of 60 μm or more. In addition, the friction coefficient of the iron-based alloy formed with the chromium-based coating layer and the precipitated carbonization layer was shown to exhibit a characteristic of lowering to a minimum of 0.4 level, and exhibited improved hardness characteristics of 1450 HV or more.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is represented by the following claims, and it should be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.

[Description of the code]

1: screen plasma device

  10: vacuum chamber

  20: screen

  30: heater

  40: vacuum pump

  50: cathode power supply

  60: heater power unit

  70: dual screen

     71: outer cylinder

     72: inner tube

2: iron-based alloy

Claims (16)

1. Forming a chromium-based coating layer on the surface of the iron-based alloy using pack cementation; And

   Iron-based alloy coating method comprising the step of: forming a precipitated carbonized layer using a screen plasma on the chromium-based coating layer.
2. The method of claim 1,

   The iron-based alloy coating method, characterized in that it comprises a bearing steel or stainless steel.
3. The method of claim 1,

   The chromium-based coating layer is chromium (Cr), chromium (Cr) and iron (Fe) or chromium (Cr), iron (Fe) and vanadium (V), characterized in that the iron-based alloy coating method.
4. The method of claim 1,

   Forming a chromium-based coating layer on the surface of the iron-based alloy using the pack cementation,

   Injecting an iron-based alloy and a pack mixture into a pack;

   Charging the pack to a vacuum chamber;

   A heating step of heating the pack charged in the vacuum chamber; And

   And a chromium-based coating layer forming step of forming a chromium-based coating layer on the iron-based alloy while heating is maintained in the heating step.

   The pack mixture includes a chromium-based powder, an activator which reacts with the chromium-based powder and contributes to the formation of the chromium-based coating layer, and an inert agent preventing sintering of the iron-based alloy in the process of forming the chromium-based coating layer. Iron-based alloy coating method.
5. The method of claim 4, wherein

   The chromium-based powder of the pack mixture includes chromium (Cr) powder, chromium (Cr) powder and iron (Fe) powder or chromium (Cr) powder, iron (Fe) powder and vanadium (V) powder. Iron-based alloy coating method.
6. The method of claim 4, wherein

   The pack mixture comprises 10.5 wt% to 52.9 wt% of the chromium-based powder, 0.1 wt% to 3 wt% of the activator, and 47 wt% to 89.4 wt% of the inert agent.
7. The method of claim 1,

   Forming an nitriding carbonization layer using the screen plasma on the chromium-based coating layer,

   Charging the iron-based alloy coated with the chromium-based coating layer into a vacuum chamber and covering the iron-based alloy with a double screen;

   An ion cleaning step of reducing a chromium-based oxide film present on the iron-based alloy by injecting a first hydrogen gas into the vacuum chamber;

   Applying a process current to the dual screen and injecting a second hydrogen gas, nitrogen gas and hydrocarbon gas into the vacuum chamber to generate a mixed plasma; And

   The mixed plasma is coated on the chromium-based coating layer formed on the surface of the iron-based alloy to form an impregnated carbonization layer; Iron-based alloy coating method comprising a.
8. The method of claim 7, wherein

   The ion cleaning step,

   Heating the vacuum chamber by applying a first current to the dual screen;

   Injecting first hydrogen into the vacuum chamber;

   Applying a second current to the dual screen to generate a hydrogen plasma around the dual screen; And

   Reducing and removing the chromium-based oxide film present on the iron-based alloy; Iron-based alloy coating method comprising a.
9. The method of claim 8,

   The first current is 3 A to 5 A and the second current is 5 A to 15 A, characterized in that the iron-based alloy coating method.
10. The method of claim 8,

    The chromium-based oxide film is chromium (Cr), chromium (Cr) and iron (Fe) or chromium (Cr), iron (Fe) and vanadium (V), characterized in that the iron-based alloy coating method.
11. The method of claim 7, wherein

    The process current is iron coating method, characterized in that 20 to 30 A.
12. The method of claim 7, wherein

    And the content ratio of the nitrogen gas to the second hydrogen gas is 1: 3 to 4: 1.
13. The method of claim 7, wherein

    The hydrocarbon gas includes CH ₄ or C ₂ H ₂ and the iron-based alloy coating method, characterized in that the pulse amount of 1 sccm to 10 sccm gas is repeatedly injected in the injection section and the stop section.
14. A product having high hardness and low friction characteristics manufactured by the method of claim 1.
15. The method of claim 14,

    Hardness of the product is a product having high hardness and low friction characteristics, characterized in that 1450 HV to 2400 HV.
16. The method of claim 14,

    The friction coefficient of the product is a product having high hardness and low friction characteristics, characterized in that 0.3 to 0.4.

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