WO2019045520A1

WO2019045520A1 - Piston ring with low-friction coating film and manufacturing method therefor

Info

Publication number: WO2019045520A1
Application number: PCT/KR2018/010148
Authority: WO
Inventors: 이한찬; 윤혜원; 문경일; 방경배; 신승용; 전영하; 여기호; 홍정기; 오세필; 정훈
Original assignee: 한국생산기술연구원; (주)제이앤엘테크
Priority date: 2017-08-31
Filing date: 2018-08-31
Publication date: 2019-03-07

Abstract

The present invention provides a manufacturing method for a piston ring, the method comprising the steps of: placing a piston ring inside a physical deposition apparatus, introducing inert gas thereinto, and feeding reactive gas containing nitrogen gas (N2) or nitrogen atoms (N), thereby forming a nanocomposite coating film containing nitrogen on a surface of the piston ring through physical deposition of a Zr-Cu-Si based alloy target, wherein the composition of the alloy target is composed of 82-90 at% of Zr, 4-14 at% of Cu, and 4-8 at% of Si.

Description

Patent application title: PISTON RING WITH A LOW FRICTION COATING FILM

The present invention relates to a piston ring and a manufacturing method thereof, and more particularly, to a piston ring coated with a nanocomposite coating film made of a multi-component metal and having excellent low friction characteristics, and a method for manufacturing the same.

The piston ring is a part that is mounted on the piston inside the cylinder of the internal combustion engine. For example, a plurality of piston ring grooves may be formed in the piston, and each piston ring groove may be fitted with a piston ring. For example, the piston is provided with three piston rings, the upper two piston rings serving as a compression ring to maintain the airtightness inside the combustion chamber and to transfer the heat of the piston heated by the combustion to the cylinder block, May serve as an oil ring to scrape off the engine oil supplied to the cylinder liner.

In such a piston ring, a large number of cases where excellent lubrication characteristics are required are generated. In order to improve such lubrication characteristics, a technique of forming a thin film (or a thick film) having a low friction property on the surface of the piston ring can be applied. For example, energy consumption may occur due to friction between the cylinder inner wall and the piston ring. When the friction between these driving parts is reduced, the consumption of the automobile fuel is reduced, and the fuel efficiency can be improved. Since the thin film (or the thick film) having such a low friction characteristic must withstand a severe friction environment, it is required to have a hardness of not less than a certain level and adhesion to the piston ring in addition to a low friction property, and a high resistance to an oxidizing atmosphere is required. As the thin film (or the thick film) having such a low friction characteristic, a nitride material having a high hardness, a ceramic material based on a carbide, a diamond like carbon (DLC) or the like can be formed on the piston ring. However, the conventional ceramic-based thin film exhibits a high hardness of about 2000 Hv or more, but exhibits a high elastic modulus difference with the metal material (cast iron, carbon steel, alloy steel) forming the piston ring, which may be disadvantageous in terms of durability.

It also exhibits a high coefficient of friction to be applied to important drive members such as automotive engines and the like. On the other hand, in the case of the DLC film, the friction reduction effect is not large in the boundary lubrication environment, and graphitization (sp ³ → sp ² ) progresses due to abrasion under the boundary lubrication environment accompanied by the temperature rise due to the solid- This can result in serious wear of the membrane and may not be compatible with additives such as friction modifiers added in the lubricating oil, such as, for example, organic molybdenum compounds (MoDTC, Molybdenum dialkyldithiocarbamate), which reduces the additive efficiency and increases wear resistance of the DLC film There may be a problem in promoting the use of the present invention.

It is an object of the present invention to solve the above-mentioned problems and to provide a piston ring having a coating film of low friction and high hardness, which is made of an alloy having excellent thermal and mechanical stability. However, these problems are exemplary and do not limit the scope of the present invention.

A method of manufacturing a piston ring according to one aspect of the present invention is provided. The manufacturing method of the piston ring includes forming a Zr-Cu-Si nanocomposite coating film containing nitrogen on the surface of the piston ring. In the nanocomposite coating film, the composition of the component other than nitrogen ranges from 80 atom% to 92 atom% of Zr; 2 atom% to 10 atom% Cu; And 5 atom% to 15 atom% of Si.

Forming a nanocomposite coating film on the surface of the substrate, placing the piston ring in a physical vapor deposition apparatus, introducing an inert gas, introducing a reaction gas containing a nitrogen gas (N ₂ ) or a nitrogen element (N) Forming a nanocomposite coating film containing nitrogen on the surface of the piston ring by physical vapor deposition of a Zr-Cu-Si based alloy target, wherein the composition of the alloy target is 82 atom% to 90 atom% of Zr; 4 atom% to 14 atom% Cu; And 4 at% to 8 at% of Si.

In the manufacturing method of the piston ring in which the low friction coating film is formed, the step of supplying the inert gas and the reactive gas into the physical vapor deposition apparatus while supplying pulse power or DC power having a frequency range of 50 kHz to 350 kHz to the physical vapor deposition plasma source At least 6 W / cm ² per unit area is applied to the Zr-Cu-Si alloy target to discharge the plasma, and nitrogen ions generated from the activated reaction gas are combined with the metal ions of the alloy target to form the nanocomposite coating film .

Wherein the Zr-Cu-Si-based alloy target is physically vapor-deposited to form a Zr-Cu-Si alloy target by introducing an inert gas into the physical vapor deposition apparatus before forming the nanocomposite coating film, And forming a Cu-Si coating buffer film on the surface of the piston ring.

Wherein the forming of the Zr-Cu-Si coating buffer layer comprises supplying the physical vapor deposition plasma source with the inert gas in the frequency range of 50 kHz to 350 kHz while supplying the inert gas into the physical vapor deposition apparatus, A pulse power or a DC power is applied to the Zr-Cu-Si alloy target at a minimum of 6 W / cm ² per unit area to discharge plasma, nitrogen ions generated from the activated reaction gas are combined with metal ions of the alloy target And forming the Zr-Cu-Si coating buffer film.

The manufacturing method of the piston ring having the low friction coating layer may include: forming the Zr-Cu-Si coating buffer film; A pretreatment step of activating the surface of the piston ring by previously injecting an inert gas into the ion gun plasma source in the physical vapor deposition apparatus and ionizing the inert gas by applying power to release the ion beam, .

In the pretreatment step of the method of manufacturing the piston ring in which the low friction coating film is formed, the power may satisfy a current of 0.3 A to 1.0 A and a voltage of 1000 V to 2000 V.

In the method of manufacturing the piston ring in which the low friction coating film is formed, the nitrogen-containing nanocomposite coating film contains Zr in an amount of 80 atom% to 92 atom% excluding the nitrogen; 2 atom% to 10 atom% Cu; And 5 atom% to 15 atom% of Si.

There is provided a piston ring provided with a low-friction coating film according to another aspect of the present invention. Wherein the piston ring formed with the low friction coating film comprises a nitrogen-containing nanocomposite coating film formed on the surface of the piston ring, wherein the composition of the component other than nitrogen in the nanocomposite coating film is 80 atom% to 92 atom% of Zr; 2 atom% to 10 atom% Cu; And 5 atom% to 15 atom% of Si.

The nanocomposite coating film may have a ZrN or Zr ₂ N-based crystal structure.

Wherein the nanocomposite coating film has a tribo-reaction film formed on at least a part of the surface thereof when the tribo-reaction coating film is rubbed in contact with the counter material, and the composition of Cu in the tribo-reaction film- Lt; / RTI >

The composition of S and P in the region in which the tribo-reaction film is formed may be higher than that in the region in which the tribo-reaction film is not formed.

The nanocomposite coating film may have a hardness of 10 GPa to 45 GPa and an elastic modulus of 150 GPa to 450 GPa. Strictly speaking, the nanocomposite coating film may have a coefficient of friction of 0.008 to 0.024 while having a hardness of 23 GPa to 44 GPa and an elasticity of 265 GPa to 421 GPa.

The surface of the piston ring in which the nitrogen-containing nanocomposite coating film is formed may include an outer circumferential surface of the piston ring in contact with the cylinder liner or the inner surface of the block bore. The piston ring may be made of a metal material, .

There is provided a piston ring provided with a low-friction coating film according to another aspect of the present invention. Wherein the piston ring is a piston ring implemented by the manufacturing method described above, the Zr-Cu-Si coating buffer film formed on the surface of the piston ring; And a nitrogen-containing nanocomposite coating film formed on the Zr-Cu-Si coating buffer film, wherein the composition of the components other than nitrogen in the nanocomposite coating film is 80 atom% to 92 atom% of Zr; 2 atom% to 10 atom% Cu; And 5 atom% to 15 atom% of Si. In this case, the nanocomposite coating film may have a hardness of 10 GPa to 45 GPa and an elastic modulus of 150 GPa to 450 GPa. Strictly speaking, the nanocomposite coating film may have a coefficient of friction of 0.008 to 0.024 while having a hardness of 23 GPa to 44 GPa and an elasticity of 265 GPa to 421 GPa. The nitrogen-containing nanocomposite coating film may have a surface roughness Rz of 0.7 mu m and an Rpk of 0.06 mu m or less. Further, the adhesive force between the piston ring base material and the nitrogen containing nanocomposite coating film may be 28 N or more.

In addition, the thickness of the coating buffer layer may be 0.01 탆 to 5 탆, and the thickness of the nanocomposite coating film containing nitrogen may be 0.5 탆 to 30 탆.

According to one embodiment of the present invention as described above, a piston ring coated with a nanocomposite coating film having low friction characteristics can be provided. Of course, the scope of the present invention is not limited by these effects.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view of a piston ring with a low-friction coating formed thereon according to an embodiment of the present invention; FIG.

2 is a ternary phase diagram of a Zr-Cu-Si alloy which is an alloy constituting a physical vapor deposition alloy target according to an embodiment of the present invention.

Fig. 3 shows the results of SEM and BSE observations of the microstructure of the target specimen corresponding to the composition of Example 4. Fig.

FIG. 4 shows the result of SEM observation of the state of powders after mechanical alloying by introducing Zr, Cu and Si powders into a ball-mill to prepare a target specimen having a composition according to Example 5. FIG.

5 (a) to 5 (c) are the results of analyzing the composition of the powder by EDS.

FIG. 6 is a graph showing the particle size of a powder that has undergone mechanical alloying by using a particle size analyzer (PSA).

FIG. 7 shows the results of SEM and BSE microstructures of specimens sintered by spark plasma sintering using powder subjected to mechanical alloying.

FIG. 8 is a view showing physical vapor deposition process conditions, XRD analysis conditions, and results of forming a coating film of an embodiment of the present invention.

9 is an XRD result of the coating film according to Example 5. Fig.

10 (a) and 10 (b) show the results of SEM observation of the surface and cross-section of the coating film according to Example 5. Fig.

FIG. 11A shows the result of TEM observation of the microstructure of the coating film according to Example 5. FIG. 11B shows the result of SEAD (selective area diffraction) analysis. FIG.

12 is a view showing conditions and results of a reciprocating friction test for a coating film according to some embodiments of the present invention and a comparative example.

13 shows the ring-liner scuffing resistance test result.

14A and 14B are AFM optical microscope photographs and friction coefficient mapping diagrams of LFM of a base material on which a coating film is formed according to an embodiment of the present invention.

15A and 15B are AFM optical microscope photographs and friction coefficient mapping diagrams of LFM of a base material on which a coating film according to a comparative example of the present invention is formed.

16 is an SEM image of an AES analysis result of a tappet having a coating film according to an embodiment of the present invention.

17 is an SEM image for AES analysis of a tappet having a coating film according to a comparative example of the present invention.

Fig. 18 shows the results of TEM observation of the cross-section of the tribo-reaction layer.

19 is a photograph of a digital camera taken with a piston ring having a low friction coating film formed according to an embodiment of the present invention.

20 is an optical photograph of a section of a piston ring having a buffer layer and a low-friction coating film formed thereon.

FIG. 21 is a photograph showing a result of adhesion test for a piston ring having a low friction coating film formed according to an embodiment of the present invention.

22 is a graph showing a result of evaluating a friction coefficient of a piston ring formed with a coating film according to 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. The membrane referred to herein may also be referred to as a thin film or a thick film depending on the thickness of the film.

In the present invention, the term " consist of " an element having a predetermined content range means that an element other than the specific elements except for unavoidable inevitable impurities has a significant content range, Of the population.

Referring to Fig. 1, a piston ring 10 having a low friction coating film formed thereon has a low friction coating film formed on at least a part of the surfaces of the piston ring and the piston ring (e.g., sliding surfaces). The low friction coating film is a material film realized in a physical vapor deposition process using a physical vapor deposition target made of a Zr-Cu-Si alloy having a specific composition range. The physical vapor deposition target is a physical vapor deposition target made of a Zr-Cu-Si-based alloy for forming a low-friction coating film, and has a Zr of 82 atom% to 90 atom%; 4 atom% to 14 atom% Cu; And 4 at% to 8 at% of Si.

Physical vapor deposition refers to a technique of coating a surface of a base material by vaporizing or sputtering a solid phase evaporation source by using a sputtering method or an evaporation method, deposition, ion beam deposition, and the like.

Hereinafter, various embodiments are provided 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, but the present invention is not limited by the following examples.

FIG. 2 is a ternary phase diagram of a Zr-Cu-Si alloy which is an alloy constituting a physical vapor deposition alloy target according to an embodiment of the present invention, and Table 1 below shows a physical vapor deposition alloy target according to embodiments of the present invention. The composition of the constituent alloy is shown.

2 and Table 1, an alloy for a physical vapor deposition target according to one aspect of the present invention is made of at least 3 metal elements, and more specifically 4.0 atom% to 14.0 atom% of copper (Cu), silicon (Si) Of 4.0 atom% to 8.0 atom% and the balance of zirconium (Zr). That is, the Zr-Cu-Si-based alloy for the physical vapor deposition target has a Zr content of 82 atom% to 90 atom%; 4 atom% to 14 atom% Cu; And 4 at% to 8 at% of Si.

When the Zr-Cu-Si alloy of the present invention satisfies the above-mentioned composition range, the physical vapor deposition material film realized by using the physical vapor deposition target made of such an alloy can realize a high hardness of 23 GPa or more and a high elasticity of 265 GPa or more A friction coefficient lower than 0.024 can be realized. On the contrary, when the composition of Zr is lower than 82 atomic%, for example, the oxidation resistance of the alloy becomes relatively low, and when the composition of Cu exceeds 16 atomic%, the composition of Cu becomes 14 atomic% , The friction coefficient of the physical vapor deposition alloy film becomes remarkably high. When the composition of Si is more than 26 at%, more strictly, when the composition of Si exceeds 8 at% And there is a problem that hardness and elasticity of the physical vapor deposition alloy film are lowered.

The embodiments of the present invention shown in Table 1 satisfy the composition ranges described above. For example, the alloy target according to Example 1 has a chemical composition (atomic%) of Zr ₈₂ Cu _13.5 Si _4.5 , and the alloy target according to Example 2 has a chemical composition (atomic%) of Zr _84.1 Cu _10.4 Si _5.5 , The alloy target according to Example 3 had a chemical composition (atomic%) of Zr _86.3 Cu _7.2 Si _6.5 , the alloy target according to Example 4 had a chemical composition (atomic%) of Zr _88.4 Cu _4.1 Si _7.5 , The alloy target according to Example 5 has a chemical composition (atomic%) of Zr _89.6 Cu _3.3 Si _7.1 .

In one embodiment, the Zr-Cu-Si-based alloy constituting the physical vapor deposition target may be a cast alloy realized by casting a molten metal. For example, the alloy may be produced by casting a molten metal produced by the plasma arc melting method, and then cutting the ingot to produce a target.

In another embodiment, the Zr-Cu-Si-based alloy constituting the physical vapor deposition target may be a small-sized gold alloy produced by a powder metallurgy method. For example, Zr, Cu, and Si powders may be mechanically alloyed using a ball-mill or the like, followed by sintering the mechanically alloyed powders. The sintering may include, for example, hot sintering, spark plasma sintering, hot pressing, hot isostatic press sintering, and the like.

On the other hand, as another example, the Zr-Cu-Si-based alloy constituting the physical vapor deposition target has a Zr content of 82 atom% to 90 atom%; 4 atom% to 14 atom% Cu; And 4 at% to 8 at% of Si; a plurality of amorphous alloys or nanocrystalline alloys comprising: The first shrinkage of the amorphous alloy or the nanocrystalline alloy by pressing the amorphous alloy or the nanocrystalline alloy while maintaining the amorphous alloy or the nanocrystalline alloy at a temperature not higher than the glass transition temperature (Tg) of the amorphous alloy or the nanocrystalline alloy at the crystallization start temperature (Tx) ; And secondarily shrinking the plurality of amorphous alloys or nanocrystalline alloys by pressurizing the amorphous alloy or the nanocrystalline alloy while maintaining the temperature within a range of 0.7 to 0.9 times the melting temperature (Tm) of the amorphous alloy or nano-crystalline alloy for a predetermined period of time; The present invention may be a crystalline alloy, which is implemented by performing the above process.

The nanocomposite coating film according to another aspect of the present invention can be produced by injecting inert gas into a physical vapor deposition apparatus and introducing a reaction gas containing nitrogen gas (N ₂ ) or nitrogen element (N) -Si-based alloy target by physical vapor deposition.

The nanocomposite coating film is a nanocomposite coating film containing nitrogen, and can be understood as a nano-structured film containing nitrogen, a nano-nitride film, or a nano-structured composite film.

For example, in a physical vapor deposition process, a gas including nitrogen gas (N ₂ ) or nitrogen (N), for example, ammonia (NH ₃ ) as a reactive gas is introduced into a physical vapor deposition chamber, , High zirconium (Zr) reactive with nitrogen in the alloy can react with nitrogen to form zirconium nitride. Other elements may be solubilized in the zirconium nitride or may be present in the metal phase.

The thin film has a structure in which a nitride phase of a metal or one or more metal phases are mixed with each other, and the nitride phase of the metal may include, for example, zirconium as a constituent element of the nitride. At this time, the nitrogen-containing nanocomposite coating film shows a crystal structure of zirconium nitride, and other metal elements can be dissolved in zirconium nitride in the form of nitride. At this time, the zirconium nitride may contain any one or more of Zr or ZrN ₂ N in accordance with the conditions of the reactive gas containing nitrogen during physical vapor deposition.

In the nanocomposite coating film containing nitrogen, the nitride phase of the metal has a nanocrystalline structure consisting of crystal grains of several to several tens of nanometers in size. On the other hand, the metal phase can be distributed in a trace amount to such a nanocrystalline system. For example, the metal phase is distributed in several atomic units and may exist in a form that does not form a special crystal structure. However, such a metal phase is not distributed intensively in a specific region but distributed uniformly throughout the film.

In order to further improve the characteristics of the base material coated with the nitrogen-containing nanocomposite coating film, a buffer layer is formed between the bottom of the nanocomposite coating film containing nitrogen, that is, between the base material (piston ring) and the nitrogen- May be formed. At this time, the buffer layer may function as an adhesion layer for further improving the adhesion of the nanocomposite coating film containing nitrogen, for example, to the base material. As another example, the stress relaxation layer may be a stress relaxation layer for relieving the stress between the base material and the nanocomposite coating film containing nitrogen, and as another example, it may be a corrosion resistant layer for improving corrosion resistance. However, the buffer layer is not limited thereto, and may refer to both a nanocomposite coating film containing nitrogen in the structural aspect of the thin film (or thick film) and a layer that can be interposed between the parent material.

As such a buffer layer, a Zr-Cu-Si coating buffer layer implemented by introducing an inert gas (for example, argon gas) into the physical vapor deposition apparatus and physical vapor deposition of the Zr-Cu-Si based alloy target described above is used . Specifically, in the step of coating the base material with physical vapor deposition after the alloy target is mounted in the physical vapor deposition chamber, a buffer layer is formed on the base material by a non-reactive physical vapor deposition process with a predetermined thickness while introducing an inert gas into the physical vapor deposition chamber Then, a nitrogen-containing nanocomposite coating film can be formed by performing physical vapor deposition while introducing nitrogen gas into the physical vapor deposition chamber. In this case, the buffer layer and the nanostructured film containing nitrogen can be formed in-situ by using the same alloy target. In this case, the nanocomposite coating film may be made of the same element as the buffer layer except nitrogen. However, the present invention is not limited thereto.

The interface of the buffer layer and the nitrogen-containing nanocomposite coating film may include nitrogen or a boundary layer in which elements constituting the buffer layer are inclined and constituted. That is, the boundary layer may be formed in which the composition changes gradually without changing the composition abruptly at the interface, and the composition has a slope.

The thickness of the buffer layer described above may be, for example, from 0.01 탆 to 5 탆, and the thickness of the nitrogen-containing nanocomposite coating film may be, for example, 0.5 탆 to 30 탆.

Hereinafter, it will be explained that the nanocomposite coating film containing nitrogen according to the embodiments of the present invention exhibits greatly improved friction characteristics, and has high hardness and adhesion.

Table 2 shows the composition, thickness, roughness, hardness, elasticity, and friction of the nanocomposite coating film implemented by the composition of the sputtering target and the sputtering process conditions according to Examples 1 to 5 and Comparative Examples 1 to 5 of the present invention Respectively. As the substrate, carburized SCM415 was used.

The sputtering target according to Examples 1 to 4 is a cast alloy produced by the plasma arc melting method, and the sputtering target according to Example 5 is a sintered alloy produced by the spark plasma sintering method.

According to Examples 1 to 5, Zr is 82 atom% to 90 atom%; 4 atom% to 14 atom% Cu; And nitrogen (N ₂ ) or a nitrogen element (N) in a sputtering apparatus, wherein the sputtering target is a sputtering target having a Si content of 4 to 8 atom% And the Zr-Cu-Si based alloy target is physically vapor deposited to form a nanocomposite coating film containing nitrogen, the composition of the nanocomposite coating film excluding nitrogen is 80 atom% to 92 atom% of Zr; 2 atom% to 10 atom% Cu; And 5 atom% to 15 atom% of Si.

On the contrary, Comparative Example 1 to Comparative Example 2 formed a nanocomposite coating film using a Zr-Cu-Si based alloy target, but the alloy target did not satisfy the above-mentioned composition range, Si-based alloy target instead of the Si-based alloy target, Comparative Example 4 corresponds to the case where the Si-DLC coating film of the prior art is applied without using the physical vapor deposition process, and Comparative Example 4 corresponds to the case of using the Zr- Example 5 corresponds to a case in which a coating film is not separately applied.

Table 2 shows that the nanocomposite coating film according to the embodiments of the present invention has a high hardness of 23 GPa to 44 GPa and a high elasticity of 265 GPa to 421 GPa and a low coefficient of friction of 0.008 to 0.024. On the other hand, according to the comparative example of the present invention, the hardness and elasticity are high but the friction coefficient is relatively high (Comparative Example 1 and Comparative Example 2), the friction coefficient is low but the hardness and elasticity are relatively low ), Low hardness and elasticity, and high coefficient of friction (Comparative Example 4 and Comparative Example 5), indicating that it is not suitable for a low friction coating film.

Fig. 3 shows the results of SEM and BSE observations of the microstructure of the target specimen corresponding to the composition of Example 4. Fig. The relative density of the target specimen was as high as about 99%. On the other hand, as shown in Fig. 3, the cast specimen showed a dendrite structure. In order to investigate the uniformity of the composition of each specimen, EDS analysis was carried out and it was confirmed that the composition distribution was uniform throughout.

FIG. 4 shows the result of SEM observation of the state of the powder after mechanical alloying by injecting Zr, Cu and Si powder into a ball-mill to prepare a target specimen having a composition according to Example 5. FIG. To (c) are the results of analyzing the composition of the powder by EDS. Referring to FIGS. 4 and 5, it is confirmed that the Zr, Cu and Si powders are alloyed so as to have a uniform distribution by mechanical alloying. FIG. 6 shows that the particle size of the powder that has undergone mechanical alloying is analyzed by a particle size analyzer (PSA), and that it has a uniform particle size as a whole.

FIG. 7 shows the result of SEM observation of the microstructure of a specimen sintered by spark plasma sintering using powder subjected to mechanical alloying. It shows uniform microstructure composed of very fine grains as a whole, and it can be confirmed that EDS analysis has a uniform composition distribution as a whole.

FIG. 8 is a view showing sputtering process conditions and XRD analysis conditions and results for forming a coating film according to Example 2 of the present invention, and FIG. 9 is an XRD result of a coating film according to Example 5. 8 and 9, it is confirmed that the coating film has a ZrN-based nanocomposite crystal structure, wherein the coating film has a ZrN crystal structure as a basic structure, wherein Cu and Si form a ZrN crystal Structure having a nanocomposite crystal structure.

10 (a) and 10 (b) show the results of SEM observation of the surface and cross-section of the coating film according to Example 5. FIG. 10 (a) and 10 (b), it can be seen that the produced coating film has a very smooth surface and has a columnar structure.

FIG. 11A shows the result of TEM observation of the microstructure of the coating film according to Example 5. FIG. 11B shows the result of SEAD (selective area diffraction) analysis. FIG. Referring to FIG. 11 (a), it can be seen that the grain size has a very fine grain size in the range of 5 to 20 nm. Referring to FIG. 11 (b), it can be seen that a ring-pattern is observed in the nanocomposite coating.

Referring to FIG. 12, the coefficient of friction of the nitrogen-containing nanocomposite coating film according to the embodiments of the present invention is significantly lower than that of the DLC coating film. Therefore, it can be confirmed that the nitrogen-containing nanocomposite coating film according to the embodiments of the present invention is formed on the base material rather than the case where the DLC is formed on the base material, and thus the low friction characteristic is better.

The nanocomposite coating film containing nitrogen according to the technical idea of the present invention can be applied as a coating film formed on the surface of a piston ring which is a piston part. Hereinafter, such an application example will be described.

In the manufacturing method of the piston ring according to the technical idea of the present invention, first, a piston ring made of cast iron, carbon steel or alloy steel is disposed inside the physical vapor deposition apparatus. Before being placed in the physical vapor deposition apparatus, the piston ring may optionally be nitrided or CrN or TiN surface treated. After the piston ring is placed inside the physical vapor deposition apparatus, inert gas is introduced and a reaction gas containing a nitrogen gas (N ₂ ) or a nitrogen element (N) is introduced to physically deposit a Zr-Cu- Thereby forming a nanocomposite coating film containing nitrogen on the surface of the piston ring. In this case, the composition of the alloy target is such that Zr is 82 atom% to 90 atom%; 4 atom% to 14 atom% Cu; And 4 at% to 8 at% of Si.

The step of forming the nano-composite coating film containing nitrogen on the surface of the piston pin, the piston ring, or the tappet may include supplying the inert gas and the reactive gas into the sputtering apparatus while performing physical vapor deposition plasma A pulse power or a DC power source having a frequency range of 50 kHz to 350 kHz is applied to the Zr-Cu-Si based alloy target at a minimum of 6 W / cm ² per unit area, and nitrogen is generated from the activated reaction gas by discharging the plasma And forming the nanocomposite coating film by binding with metal ions of the alloy target.

According to another aspect of the present invention, there is provided a method of manufacturing a piston ring coated with a nanocomposite coating film containing nitrogen, wherein an inert gas is introduced into the physical vapor deposition apparatus before forming the nanocomposite coating film, And forming a Zr-Cu-Si coating buffer film on the surface of the piston ring by physical vapor deposition of a Cu-Si based alloy target.

For example, in the case of sputtering, the step of forming the Zr-Cu-Si coating buffer film may include supplying pulsed power having a frequency range of 50 kHz to 350 kHz to a physical vapor deposition plasma source while supplying the inert gas into the physical vapor deposition apparatus, Is applied to the Zr-Cu-Si-based alloy target at a minimum of 6 W / cm ² per unit area to discharge the plasma, nitrogen ions generated from the activated reaction gas combine with the metal ions of the alloy target to form the Zr- Si coating buffer film.

Further, a method of manufacturing a piston ring coated with a nanocomposite coating film containing nitrogen according to the technical idea of the present invention comprises the steps of: forming the Zr-Cu-Si coating buffer film; A pretreatment step of activating the surface of the piston ring by previously injecting an inert gas into the ion gun plasma source in the physical vapor deposition apparatus and ionizing the inert gas by applying power to release the ion beam, . In this case, in the preprocessing step, the power may satisfy a current of 0.3 A to 1.0 A and a voltage of 1000 V to 2000 V.

The piston ring implemented by the above-described manufacturing method includes a nitrogen-containing nano composite coating film formed on the surface of the piston ring, wherein the composition of the component other than nitrogen in the nano composite coating film is 80 atom% to 92 atom% ; 2 atom% to 10 atom% Cu; And 5 atom% to 15 atom% of Si. The nitrogen-containing nanocomposite coating film has a high hardness of 10 GPa to 45 GPa and a high elasticity of 150 GPa to 450 GPa, and has a low friction coefficient of 0.008 to 0.024.

Fig. 13 shows the result of the ring-liner scuffing resistance test. The test material on which the coating film was formed was a piston ring, and the test material was a cylinder liner. The lubricant was a mixture of 5W30 and MoDTC. As a comparative example, two types of TaC (tetrahedral amorphous carbon) coating films TaC (1) (Comparative Example 7) and TaC (2) (Comparative Example 8) was used. Referring to FIG. 13, it can be seen that the coating film according to Example 5 of the present invention exhibits superior properties as compared with Comparative Examples 7 and 8.

Table 3 shows changes in roughness of Example 5, Comparative Example 7, and Comparative Example 8 before and after the liner scuffing resistance test. Referring to Table 3, in the case of the coating film of Example 5, the damage of the liner did not occur even after the test was completed, and the surface of the coating film itself was hardly worn. On the other hand, in the case of Comparative Example 7 and Comparative Example 8, the roughness changes remarkably due to the severe wear of the coating film.

Hereinafter, the tribo-reaction layer analysis results of the coating film according to Examples and Comparative Examples of the present invention will be described. On the surface of the specimen tappet, a coating corresponding to Example 2 and Comparative Example 4 was formed, and after the reciprocating friction test was completed, the tribo reaction layer formed on the surface was analyzed. Coated tappets were subjected to a friction test for 1 hour in a lubrication condition of 5W30 and MoDCT using a reciprocating high temperature friction tester. The applied load was 75 N, and the reciprocating distance was 10 mm, the speed was 5 Hz (100 mm / sec) and the temperature was 100 ° C. Each sample was washed in an ultrasonic bath with ethanol for 1 minute to remove residual lubricant on the surface prior to LFM analysis. Then, in order to investigate the friction characteristics of the tribo reaction layer formed on the nanocomposite coating film, the friction coefficient was obtained in the LFM mode using an AFM machine. The LFM measurement condition was a measurement of the area of 20 × 20 μm at a scan speed of 0.5 Hz and a load of 10 mN, and the measured coefficient of friction was represented by mapping.

The principle of LFM (lateral force microscopy) is very similar to AFM (Atomic Force Microscopy). In the contact mode of the AFM, the degree of bending of the cantilever in the vertical direction is measured to collect information on the surface of the sample, while in the LFM, the degree of bending of the cantilever in the horizontal direction is measured. When measuring the surface of a sample with a cantilever, the degree of warping depends on the shape of the surface of the sample, the friction coefficient, the moving direction of the cantilever, and the horizontal spring constant of the cantilever. This makes it possible to analyze the friction characteristics of the sample surface by measuring the cantilever slope difference on the material surface composed of different components.

14A and 14B are AFM optical microscope photographs and friction coefficient mapping diagrams of a tappet having a coating film formed according to the second embodiment of the present invention using LFM. 15A and 15B are AFM optical microscope photographs and friction coefficient mapping diagrams of a tappet having a coating film according to Comparative Example 4 of the present invention, using LFM.

As a result of the friction coefficient measured by LFM, the tappet on which the nanocomposite coating film (Example 2) was deposited showed a significantly lower friction coefficient than the tappet on which Si-DLC (Comparative Example 4) was deposited. This can be seen from the LFM results in Figs. 14 and 15. Fig. The SEM observation results for measuring the friction region of each composition show that the dark region and the bright region are significantly different in the case of the nanocomposite coating film of Example 14 (FIG. 14A). On the other hand, it can be seen that the coating film of Comparative Example 4 (FIG. 15A) does not have a relatively large difference. The dark region identified in the nanocomposite coating film (Example 2) of FIG. 14A is regarded as a tribo-reaction layer, and the bright region is determined as a region in which such a trivalent reaction layer is not formed.

The tribo-reaction layer formed by friction has a total thickness of 300 nm to 600 nm, and the organic material layer formed at the outermost portion of the reaction layer has a thickness of 2 nm to 100 nm. FIG. 18 exemplarily shows a cross- TEM observation results are shown.

A friction coefficient mapping image measured with LFM is shown in Figs. 14B and 15B. The coating film of Example 2 has an average coefficient of friction of 0.016 and exhibits a low coefficient of friction over the whole area measured. Especially, in the dark region where solid contact occurs during the friction test, low friction coefficient was confirmed, and high friction coefficient was confirmed in the bright region. On the other hand, referring to FIG. 15B, in Comparative Example 4, the average coefficient of friction was 0.032, and a high coefficient of friction was confirmed throughout the entire region, and a low coefficient of friction was confirmed only in the minimum region in the measured region.

AES measurements were performed for more detailed component analysis of the triabo reaction layer. 16 is a SEM image for AES analysis results of a tappet having a coating film according to Example 2 of the present invention, and Table 4 is a SEM image of a tappet-reaction layer of a tappet having a coating film formed according to Example 2 of the present invention. layer analysis results.

17 is an SEM image for AES analysis results of a tappet having a coating film according to Comparative Example 4 of the present invention, and Table 5 is a SEM image of a tappet having a coating film formed according to Comparative Example 4 of the present invention. The results are shown.

An element analysis of a dark region and a bright region without a triboactivation layer, which were judged to be the tribo-reaction layers of each sample confirmed in the SEM images of FIGS. 16 and 17, were performed through the AES point analysis. AES analysis showed that both the coating layer composition and the lubricant composition were detected throughout the two samples. Table 4 shows changes in the contents of the dark region and the bright region of the nanocomposite coating film (Example 2). In the dark region, the content of Cu was higher than that of bright region, and the content of Zr and Si was higher in bright region. Among the lubricating oil components, S, P, which are known to act as a tribo - reaction layer, and Mo, Ca, K, which exhibit low friction characteristics, were detected high in the dark region.

17 and Table 5, in the case of Comparative Example 4, the coating layer compositions C and Si were detected to be high in the dark region. S, P, Mo, Ca, and K are detected more in the bright region than in the dark region. Compared with the results of the nanocomposite coating film (Example 2), the low-friction region of the very small region confirmed in the friction coefficient mapping result using the dark region and the LFM confirmed in the AES analysis of the Si-DLC is the residual oil .

As a result, copper (Cu), which is well known as a solid lubricant soft metal among the nanocomposite coating films according to the embodiment of the present invention, reacts with the lubricant composition during the friction test to contribute to the formation of the tribo-reactive layer, can confirm.

FIG. 19 is a photograph of a digital camera taken on a piston ring having a low friction coating film formed thereon according to an embodiment of the present invention, and FIG. 20 is an optical photograph of a cross section of a piston ring formed with a buffer layer and a low friction coating film. The 'base material' shown in the figure corresponds to the base material of the piston ring, the 'Buffer' layer corresponds to the buffer layer described above, and the 'ZALC' layer corresponds to the nanocomposite coating film.

The compression ring shown in Figs. 19 and 20 is a piston ring mounted on the upper portion of the piston, and serves to maintain the airtightness inside the combustion chamber and to transfer the heat of the piston heated by the combustion to the cylinder block, The oil ring is a piston ring mounted on the lower part of the piston and serves to scrape down the engine oil supplied to the cylinder liner.

The base material of the compression ring (top, 2nd) and the oil ring (2 piece, 3 piece (side rail)) is, for example, a cast iron or carbon steel used as a bar in a metal state, Alternatively, the surface can be nitrided and coated with a low-friction coating. The cast iron may include cast graphite cast iron, gray cast iron, spheroidized cast iron, or cast iron, and the alloy steel may include molybdenum steel, chromium molybdenum steel, chromium nickel steel, or stainless steel. For example, if the chromium component is contained in the alloy steel, it can be used by nitriding or non-nitriding.

In the piston ring formed with the low friction coating film according to an embodiment of the present invention, the coating area is coated on the outer circumferential surface (sliding portion) of the piston ring in contact with the cylinder liner or the block bore inner diameter. Of course, in a special case, the coating film may be coated on a portion other than the outer peripheral surface of the piston ring.

Referring to FIG. 21 showing the result of the torsion test in the adhesion test, it can be confirmed that the piston ring formed with the low-friction coating film according to an embodiment of the present invention is free from boundary separation even when twisted. On the other hand, as a result of the scratch test in the adhesion test, it can be confirmed that the adhesive force between the piston ring body and the nitrogen-containing nanocomposite coating film is 35 N or more.

22 is a graph showing a result of evaluating a friction coefficient of a piston ring formed with a coating film according to an embodiment of the present invention and a comparative example using a friction and wear tester for evaluating a friction coefficient against a piston ring.

Referring to FIG. 22, the piston ring, which is a first comparative example of the present invention, has a CrN coating film having a thickness of about 30 占 퐉, a hardness of 850 to 1300 Hv, and a highest friction coefficient. The piston ring, which is the second comparative example of the present invention, has a Si-DLC coating film having a thickness of about 7 탆, a hardness of about 1600 Hv, and a relatively high coefficient of friction. The piston ring, which is an embodiment of the present invention, is formed with a nanocomposite coating film (ZALC) coating film having a thickness of about 10 mu m, has a hardness of 2000 to 2500 Hv, and has the lowest friction coefficient.

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 invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims

And forming a Zr-Cu-Si nanocomposite coating film containing nitrogen on the surface of the piston ring.

A method for manufacturing a piston ring having a low friction coating film formed thereon.
The method according to claim 1,

Wherein the composition of the nanocomposite coating film is composed of 80 atomic% to 92 atomic% of Zr, 2 atom% to 10 atom% Cu; And Si is 5 atomic% to 15 atomic%, based on the total mass of the low-friction coating film.
The method according to claim 1,

Forming a nanocomposite coating film on the surface of the substrate, placing the piston ring in a physical vapor deposition apparatus, introducing an inert gas, introducing a reaction gas containing a nitrogen gas (N 2 ) or a nitrogen element (N) And a physical vapor deposition step of forming a nanocomposite coating film containing nitrogen on the surface of the piston ring by physical vapor deposition of a Zr-Cu-Si alloy target,

The composition of the alloy target is 82 atom% to 90 atom% of Zr; 4 atom% to 14 atom% Cu; And 4 at% to 8 at% of Si.

A method for manufacturing a piston ring having a low friction coating film formed thereon.
The method of claim 3,

Wherein the physical vapor deposition step comprises supplying a pulsed power or a DC power having a frequency range of 50 kHz to 350 kHz to the physical vapor deposition plasma source to the Zr-Cu-Si based alloy target in the unit of the physical vapor deposition apparatus while supplying the inert gas and the reactive gas into the physical vapor deposition apparatus. coating at least 6W / by applying cm 2 with nitrogen ions produced from the reaction gas activated by a discharge plasma is formed with a low-friction coating, comprising the step of forming the nanocomposite coating in conjunction with the metal ion of the alloy target A method of manufacturing a piston ring.
The method of claim 3,

Before forming the nanocomposite coating film,

And forming a Zr-Cu-Si coating buffer film on the surface of the piston ring by physically depositing the Zr-Cu-Si alloy target by injecting an inert gas into the physical vapor deposition apparatus.

A method for manufacturing a piston ring having a low friction coating film formed thereon.
6. The method of claim 5,

The forming of the Zr-Cu-Si coating buffer layer may include supplying a pulsed power having a frequency of 50 kHz to 350 kHz or a DC power source to the physical vapor deposition plasma source while supplying the inert gas into the physical vapor deposition apparatus, The step of discharging the plasma by applying a minimum of 6 W / cm 2 per unit area to the alloy target to form the Zr-Cu-Si coated buffer film by binding nitrogen ions generated from the activated reaction gas with the metal ions of the alloy target Wherein the low friction coating film is formed on the piston ring.
6. The method of claim 5,

Forming a Zr-Cu-Si coated buffer film; Before,

A pretreatment step of applying an inert gas into the ion gun plasma source in the physical vapor deposition apparatus and applying power to ionize the inert gas and emit an ion beam to activate the surface of the piston ring;

A method for manufacturing a piston ring having a low friction coating film formed thereon.
8. The method of claim 7,

Wherein the power in the pretreatment step satisfies a current of 0.3 A to 1.0 A and a voltage condition of 1000 V to 2000 V. A method of manufacturing a piston ring,
And a nitrogen-containing Zr-Cu-Si nanocomposite coating film formed on the surface of the piston ring.
10. The method of claim 9,

Wherein the composition of the nanocomposite coating film is composed of 80 atomic% to 92 atomic% of Zr, 2 atom% to 10 atom% Cu; And 5 atom% to 15 atom% of Si.
11. The method of claim 10,

The nano-composite coating film is ZrN or Zr 2 N base having a crystal structure of a low-friction piston ring coating film is formed.
11. The method of claim 10,

When the nanocomposite coating film is rubbed in contact with the counter material, a tribo-reaction film is formed on at least a part of the surface,

Wherein a composition of Cu in the region in which the tribo-reaction film is formed is higher than that in the region in which the tribo-reaction film is not formed.
13. The method of claim 12,

And the composition of S and P in the region where the tri-anti-reflection film is formed is higher than that in the region where the anti-tribo-reaction film is not formed.
11. The method of claim 10,

Wherein the nitrogen-containing nanocomposite coating film has a hardness of 10 GPa to 45 GPa and an elastic modulus of 150 GPa to 450 GPa.
11. The method of claim 10,

Wherein the surface of the piston ring in which the nitrogen-containing nanocomposite coating film is formed comprises an outer circumferential surface of the piston ring in contact with the cylinder liner or the block bore inner diameter.
11. The method of claim 10,

Wherein the piston ring is a compression ring or an oil ring whose base material is made of a metal, and a low friction coating film is formed on the piston ring.
9. A piston ring embodied by the method according to any one of claims 5 to 8, comprising: a Zr-Cu-Si coated buffer film formed on the surface of the piston ring; And a nitrogen-containing Zr-Cu-Si nanocomposite coating film formed on the Zr-Cu-Si coating buffer film.
18. The method of claim 17,

Wherein the nitrogen-containing Zr-Cu-Si nanocomposite coating film contains Zr-Cu-Si nanocomposite coating films containing nitrogen in an amount of 80 atomic% to 92 atomic% Zr; 2 atom% to 10 atom% Cu; And 5 atom% to 15 atom% of Si.
18. The method of claim 17,

Wherein the nitrogen-containing nanocomposite coating film has a hardness of 10 GPa to 45 GPa and an elastic modulus of 150 GPa to 450 GPa.
18. The method of claim 17,

Wherein the thickness of the coating buffer film is 0.01 탆 to 5 탆, and the thickness of the nitrogen-containing nanocomposite coating film is 0.5 탆 to 30 탆.