Physical vapor deposition target, nanocomposite coating film using the same, and manufacturing method therefor

Abstract

A Zr-Cu-Si based alloy for a physical vapor deposition target for forming a low-friction coating film, the Zr-Cu-Si based alloy comprising 82 at.% to 90 at.% Zr, 4 at.% to 14 at.% Cu, and 4 at.% to 8 at.% Si.

Description

TECHNICAL FIELD

[0001] The present invention relates to an alloy target for physical vapor deposition including a multi-component metal and having excellent low friction properties, a nanocomposite coating film using the same, and a method for producing the same. GENERAL STATE OF THE ART

[0002] In many cases, the driving or sliding elements of various mechanical devices or various tools require excellent lubrication properties. To improve these lubrication properties, a technique can be used to form a thin film with low friction properties on the surface of a base material. For example, the friction between various parts that occurs when driving a vehicle engine can consume energy. Reducing this friction between the driving parts reduces the vehicle's fuel consumption, thus improving fuel efficiency.Since the thin film with low friction properties must be resistant to harsh friction environments, in addition to the low friction properties, the thin film should have a hardness of more than a predetermined degree and adhesion to the base material, and must have high resistance to an oxidation atmosphere. As such a thin film with low friction properties, a high-hardness nitride- or carbide-based ceramic material, or diamond-like carbon (DLC), etc., can be used, and can be applied to the base material by a physical vapor deposition method, a chemical vapor deposition method, a plasma spray coating method, and the like.Although a typical ceramic-based thin film has a high hardness of about 2000 Hv or more, the thin film has a large difference in elastic coefficient from a metal material such as steel, aluminum, and magnesium, and may therefore be disadvantageous in terms of durability.

[0003] In addition, the friction coefficient of the typical ceramic-based thin film is too high to be applied to a critical drive element such as a vehicle engine. In the case of a DLC film, the friction reduction effect is not large under a boundary lubrication condition, and graphitization (sp 3 → sp 2) due to wear can appear as a metastable phase under boundary lubrication conditions, along with a temperature rise caused by solid-to-solid contact of a friction section, leading to severe wear of the film. Furthermore, the DLC film is incompatible with an additive such as a friction modifier, for example, an organic molybdenum compound (molybdenum dialkyldithiocarbamate (MoDTC)) added to a lubricant, so problems may arise in reducing the efficiency of the additive and promoting the wear friction of the DLC film.

[0004] KR 10 2016 0 051 952 A discloses a method for producing a nanostructured film containing an amorphous film and nitrogen, which achieves low friction properties with high hardness and adhesion properties, and also achieves a remarkably low friction coefficient value. The method for producing the nanostructured film includes a step of forming the nanostructured film by sputtering an alloy target while injecting a reaction gas containing nitrogen gas (N_2) or a nitrogen element (N) into a sputtering apparatus.

[0005] CN 1 02 925 869 A discloses a method for producing an amorphous / nanometer crystal multilayer film. The amorphous / nanometer crystal multilayer film is characterized in that the amorphous / nanometer crystal multilayer film is composed of two completely different crystal structures: a nanometer crystal structure and an amorphous structure, and has a multilayer structure consisting of alternately overlapping amorphous materials. The amorphous / nanometer crystal multilayer film produced by the method has a compact film structure and clear interlayers. DISCLOSURE OF THE INVENTION TECHNICAL PROBLEM

[0006] An object of the present invention is to provide an alloy target for physical vapor deposition capable of depositing a low-friction thin film and a high-hardness thin film using an alloy with excellent thermal and mechanical stability as a coating, a nanocomposite coating film achieved by using the alloy target, and a method for producing the same. However, such an object is merely exemplary and does not limit the scope of the present invention. TECHNICAL SOLUTION

[0007] According to one aspect of the present invention, there is provided a Zr-Cu-Si based alloy for a physical vapor deposition target for forming a low-friction coating film, wherein the Zr-Cu-Si based alloy includes 82 at.% to 90 at.% Zr, 4 at.% to 14 at.% Cu, and 4 at.% to 8 at.% Si.

[0008] According to another aspect of the present invention, there is provided a Zr-Cu-Si based alloy physical vapor deposition target for forming a low friction coating film, the target including 82 at.% to 90 at.% Zr, 4 at.% to 14 at.% Cu, and 4 at.% to 8 at.% Si.

[0009] In the physical vapor deposition target, the Zr-Cu-Si-based alloy may be a cast alloy obtained by pouring a molten metal.

[0010] In another example, the alloy may be a sintered alloy produced by a powder metallurgical sintering process.

[0011] In the physical vapor deposition target, the Zr-Cu-Si-based alloy may be a crystalline alloy obtained by performing a step of preparing a plurality of amorphous alloys or a plurality of nanocrystalline alloys consisting of 82 atomic % to 90 atomic % Zr, 4 atomic % to 14 atomic % Cu, and 4 atomic % to 8 atomic % Si, performing a step of primary shrinkage by pressurizing the plurality of amorphous alloys or the plurality of nanocrystalline alloys while maintaining the plurality of amorphous alloys or the plurality of nanocrystalline alloys for a predetermined time at a temperature in the range of the glass transition temperature (Tg) of the amorphous alloy or the nanocrystalline alloy up to its crystallization start temperature (Tx),and performing a step of secondary shrinkage by pressurizing the plurality of amorphous alloys or the plurality of nanocrystalline alloys while maintaining the plurality of amorphous alloys or the plurality of nanocrystalline alloys in a temperature range of 0.7 to 0.9 times the melting temperature (Tm) of the amorphous alloy or the nanocrystalline alloy for a predetermined time.

[0012] According to yet another aspect of the present invention, there is provided a method for producing a nanocomposite coating film, the method including: a step of forming a nitrogen-containing nanocomposite coating film by introducing an inert gas into a physical vapor deposition system, introducing a reaction gas containing a nitrogen gas (N2) or a nitrogen element (N) thereinto to physically deposit a Zr-Cu-Si-based alloy target, the alloy target having a composition consisting of 82 at.% to 90 at.% Zr, 4 at.% to 14 at.% Cu, and 4 at.% to 8 at.% Si.

[0013] The method for producing a nanocomposite coating film may further include, before the step of forming a nanocomposite coating film, a step of forming a Zr-Cu-Si coating buffer layer by introducing an inert gas into the physical vapor deposition system to physically deposit a Zr-Cu-Si based alloy target.

[0014] The method for producing a nanocomposite coating film may further include, before the step of forming a Zr-Cu-Si coating buffer layer, a pretreatment step of activating the surface of an object on which the Zr-Cu-Si coating buffer layer is to be formed by introducing an inert gas into an ion gun plasma source in the physical vapor deposition system and applying energy to ionize the inert gas and release ion beams.

[0015] In the method for producing a nanocomposite coating film, the film forming step or the pretreatment step may be carried out in a plasma atmosphere.

[0016] In the method for producing a nanocomposite coating film, the nitrogen-containing nanocomposite coating film has, in addition to nitrogen, a composition consisting of 80 at% to 92 at% Zr, 2 at% to 10 at% Cu, and 7 at% to 15 at% Si.

[0017] According to yet another aspect of the present invention, there is provided a nitrogen-containing nanocomposite coating film, wherein the nanocomposite coating film has, in addition to nitrogen, a composition consisting of 80 atomic % to 92 atomic % Zr, 2 atomic % to 10 atomic % Cu, and 5 atomic % to 15 atomic % Si.

[0018] The nanocomposite coating film may have a crystal structure based on ZrN or Zr2N.

[0019] When the nanocomposite coating film comes into contact with and is rubbed against a counter-rotating material, a triboreaction film is formed at least in some areas of the surface of the nanocomposite coating film, and the Cu content in the areas where the triboreaction film is formed is higher than in other areas where the triboreaction film is not formed.

[0020] At this time, the contents of S and P in the areas where the triboreaction film is formed are higher than in other areas where the triboreaction film is not formed.

[0021] The nanocomposite coating film can have a hardness of 10 GPa to 45 GPa and a modulus of elasticity of 150 GPa to 450 GPa. Specifically, the nanocomposite coating film can have a friction coefficient 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. BENEFICIAL EFFECTS

[0022] According to one embodiment of the present invention as described above, there can be provided: an alloy target for physical vapor deposition capable of forming a thin film with low friction properties, and capable of preventing problems of thin film composition non-uniformity, particle generation, and brittle fracture, and producing a uniform thin film during physical vapor deposition; a nanocomposite coating film obtained by using the alloy target; and a manufacturing method thereof. However, the scope of the present invention is not limited by the effect. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a ternary phase diagram of a Zr-Cu-Si alloy, which is an alloy that is an alloy target for physical vapor deposition according to an embodiment of the present invention. Fig. Figure 2 is the result of observation of the microstructure of a target sample corresponding to the composition of Example 4 by SEM and BSE. Fig. Figure 3 is the result obtained by measuring the powder state by SEM after introducing Zr, Cu, and Si powder into a ball mill for mechanical alloying thereof to prepare a target sample having the composition according to Example 5. (a) to (c) of Fig. 4 are the results obtained by analyzing the composition of the powder using EDS. Fig.Figure 5 is the result obtained by analyzing the particle size of the powder subjected to mechanical alloying with a particle size analyzer. Fig. Figure 6 is the result obtained by measuring the microstructure of a sample sintered by a spark plasma sintering process using mechanically alloyed powder by SEM and BSE. Fig. 7 is a view showing the conditions of the physical vapor deposition process for forming a coating film of an embodiment of the present invention and the conditions and results of XRD analysis. Fig. Figure 8 is the XRD result of a coating film corresponding to Example 5. (a) and (b) of Fig. 9 are the results obtained by measuring the surface and cross-section of a coating film by SEM according to Example 5. (a) of Fig. 10 is the result obtained by measuring the microstructure of a coating film according to Example 5 by TEM, and (b) of Fig. Figure 10 is the result obtained by performing selected area electron diffraction (SAED) analysis on it. Fig. 11 is a view showing the conditions and results of a reciprocating friction test for coating films according to some examples and comparative examples of the present invention. Fig. 12 is the result of a ring insert abrasion resistance test. Fig. 13A and Fig. 13B is an AFM micrograph of a tappet with a coating film according to the example of the present invention and a friction coefficient mapping image by an LFM, respectively. Fig. 14A and Fig.14B is an AFM micrograph of a tappet having a coating film according to the comparative example of the present invention and a friction coefficient mapping image by an LFM, respectively. Fig. 15 is an SEM image for the result of AES analysis of a tappet having a coating film according to the example of the present invention. Fig. 16 is an SEM image for the result of AES analysis of a tappet having a coating film according to the comparative example of the present invention. Fig. 17 is the result of observation of the cross section of a triboreaction layer observed by TEM according to an embodiment. MODE FOR CARRYING OUT THE INVENTION

[0023] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and should not be considered limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Moreover, components may be exaggerated or reduced in size in the drawings for ease of description. A film referred to herein may also be referred to as a thin film or a thick film, depending on the thickness of the film.

[0024] In the present invention, when an alloy "consists" of specific elements with predetermined content ranges, this means that elements other than the specific elements, apart from unavoidable impurities, each have a significant content range without participating in the composition of the alloy.

[0025] According to one aspect of the present invention, a Zr-Cu-Si-based alloy for a physical vapor deposition target is provided. The Zr-Cu-Si-based alloy for a physical vapor deposition target is a Zr-Cu-Si-based alloy for a physical vapor deposition target for forming a low-friction coating film and consists of 82 at.% to 90 at.% Zr, 4 at.% to 14 at.% Cu, and 4 at.% to 8 at.% Si.

[0026] Physical vapor deposition refers to a technique for coating the surface of a base material by melting and evaporating a solid target, which serves as a deposition source, or by sputtering the target. Physical vapor deposition may include, for example, a sputtering method, an evaporation method, an arc method, ion beam deposition, and the like.

[0027] Meanwhile, according to another aspect of the present invention, a physical vapor deposition target is provided. The physical vapor deposition target is a physical vapor deposition target composed of a Zr-Cu-Si-based alloy for forming a low-friction coating film, and consists of 82 atomic % to 90 atomic % Zr, 4 atomic % to 14 atomic % Cu, and 4 atomic % to 8 atomic % Si.

[0028] Fig.1 is a ternary phase diagram of a Zr-Cu-Si alloy which is an alloy constituting an alloy target for physical vapor deposition according to an embodiment of the present invention, and the following Table 1 shows the composition of an alloy constituting an alloy target for physical vapor deposition according to examples of the present invention.

[0029] With reference to Fig.1 and Table 1, the physical vapor deposition target according to one aspect of the present invention is composed of three types of metal elements, and specifically, it is composed of 4.0 at.% to 14.0 at.% copper (Cu), 4.0 at.% to 8.0 at.% silicon (Si), and the balance zirconium (Zr). That is, the Zr-Cu-Si-based alloy for a physical vapor deposition target is composed of 82 at.% to 90 at.% Zr, 4 at.% to 14 at.% Cu, and 4 at.% to 8 at.% Si.

[0030] When the Zr-Cu-Si-based alloy of the present invention satisfies the above-described composition range, a physical vapor deposition material film made of the alloy using a physical vapor deposition target can exhibit high hardness of 23 GPa or more and high elasticity of 265 GPa or more, while having a friction coefficient of less than 0.024. In contrast, when Zr in the composition is less than 82 atomic%, the oxidation resistance of the alloy becomes relatively low; and when Cu in the composition is more than 16 atomic%, especially when Cu in the composition is more than 14 atomic%, the friction coefficient of a physical vapor deposition alloy film is significantly increased.When Si in the composition is more than 26 at%, especially when Si in the composition is more than 8 at%, Si is excessively deposited without being dissolved into a nitride, so that the hardness and elasticity of the alloy film for physical vapor deposition are reduced.

[0031] Examples of the present invention shown in Table 1 satisfy the composition range described above. For example, an alloy target according to Example 1 has a chemical composition (atomic %) of Zr 82 Cu 13,5 Si 4,5 An alloy target according to Example 2 has a chemical composition (atomic %) of Zr 84,1 Cu 10,4 Si 5,5 An alloy target according to Example 3 has a chemical composition (atomic %) of Zr 86,3 Cu 7,2 Si 6,5 An alloy target according to Example 4 has a chemical composition (atomic %) of Zr 88,4Cu 4,1 Si 7,5 and an alloy target according to Example 5 has a chemical composition (atomic %) of Zr 89,6 Cu 3,3 Si 7,1 on.

[0032] In one embodiment, the Zr-Cu-Si-based alloy serving as the physical vapor deposition target may be a cast alloy obtained by casting a molten metal. For example, the alloy may be produced by casting a molten metal prepared by a plasma arc melting process to prepare a blank, which is then cut and machined to produce a target. Table 2 illustrates the plasma arc melting conditions used in the present embodiment. [Table 2] Melting conditions melting apparatus Arc melting machine Applied current (A) 100-5000 Process duration (minute) 1-120 Degree of vacuum (Torr) 2 -2 up to 2 -6 Process atmosphere argon

[0033] In another embodiment, the Zr-Cu-Si-based alloy serving as the target for physical vapor deposition may be a sintered alloy produced by a powder metallurgy process. For example, the Zr-Cu-Si-based alloy may be produced by mechanically alloying Zr, Cu, and Si powders using a ball mill and the like, followed by sintering the mechanically alloyed powders. Sintering may include, for example, hot sintering, spark plasma sintering, hot pressing, high isostatic sintering, and the like. Table 3 illustrates the process conditions for hot pressing and spark plasma sintering. [Table 3] Sintering conditions Sintering apparatus Hot pressing, spark plasma sintering Sintering temperature (°C) 300-1200 Sintering pressure (MPa) 40-300 Degree of vacuum (Torr) 2 -2 up to 2 -5 Sintering time (minute) 5-800

[0034] Meanwhile, as another example, the Zr-Cu-Si-based alloy constituting the physical vapor deposition target may be a crystalline alloy obtained by the following steps: a step of preparing an amorphous alloy or a plurality of nanocrystalline alloys consisting of 82 atomic % to 90 atomic % Zr, 4 atomic % to 14 atomic % Cu, and 4 atomic % to 8 atomic % Si; a step of subjecting the plurality of amorphous alloys or the plurality of nanocrystalline alloys to primary shrinkage by pressurizing them while maintaining the plurality of amorphous alloys or the plurality of nanocrystalline alloys at a temperature ranging from the glass transition temperature (Tg) of the amorphous alloy or the nanocrystalline alloy to its crystallization start temperature (Tx) for a predetermined time;and a step of performing secondary shrinkage by pressurizing the plurality of amorphous alloys or the plurality of nanocrystalline alloys while maintaining the plurality of amorphous alloys or the plurality of nanocrystalline alloys in a temperature range of 0.7 to 0.9 times the melting temperature (Tm) of the amorphous alloy or the nanocrystalline alloy for a predetermined time.;

[0035] A nanocomposite coating film according to another aspect of the present invention can be obtained by introducing an inert gas into a physical vapor deposition system, introducing a reaction gas containing a nitrogen gas (N2) or a nitrogen element (N), and physically depositing the Zr-Cu-Si based alloy target.

[0036] The nanocomposite coating film is a nitrogen-containing nanocomposite coating film and can be understood as a nanostructured film, a nanonitride film, or a nanostructured composite film containing nitrogen.

[0037] For example, the physical vapor deposition process may be a sputtering process. Table 4 shows the coating process conditions by a sputtering method used in the present embodiment. [Table 4] Coating process conditions Coating apparatus Sputtering, ion plating, etc. Process gas Argon, nitrogen Process pressure (mtorr) 1-50 Process duration (minute) 5-600 Degree of vacuum (Torr) 2 -2 up to 2 -5

[0038] In physical vapor deposition, when reactive sputtering is performed by introducing a reactive gas, such as nitrogen (N2) or a nitrogen-containing gas (N), such as ammonia (NH3), into a sputtering chamber, zirconium (Zr), which is highly reactive with the nitrogen in the alloy, can react with the nitrogen to form zirconium nitride (ZrN). Other elements can be dissolved in zirconium nitride or present in a metallic phase.

[0039] The thin film has a structure in which a nitride phase of a metal or one or more metal phases thereof are mixed together. The nitride phase of the metal may include, for example, zirconium as a component of a nitride. At this time, the nitrogen-containing nanocomposite coating film has the crystal structure of zirconium nitride, and other metal elements may be dissolved in the zirconium nitride in the form of a nitride. At this time, the zirconium nitride may include at least one of ZrN or Zr2N according to the conditions of a nitrogen-containing reactive gas during physical vapor deposition.

[0040] In the nitrogen-containing nanocomposite coating film, the nitride phase of the metal exhibits a nanocrystalline structure consisting of grains ranging from several to several tens of nanometers in size. On the other hand, the metal phase may be distributed in small amounts within such nanograin boundaries. For example, the metal phase is distributed in units of several atoms and may exist in a form that does not exhibit a specific crystal structure. However, the metal phase is uniformly distributed throughout the thin film and is not concentrated in a specific area.

[0041] To further improve the properties of a base material coated with the nitrogen-containing nanocomposite coating film, a buffer layer may be further formed under the nitrogen-containing nanocomposite coating film, that is, between the base material and the nitrogen-containing nanocomposite coating film. At this time, the buffer layer may function, for example, as an adhesion layer to further improve the adhesion of the nitrogen-containing nanocomposite coating film to the base material. In another example, the buffer layer may be a stress relaxation layer for reducing the stress between the base material and the nitrogen-containing nanocomposite coating film, and in another example, the buffer layer may be an anticorrosive layer for improving corrosion resistance.However, the buffer layer is not limited to this and can refer to any layer that can be inserted between the nitrogen-containing nanocomposite coating film and the base material in terms of the structure of the thin film.

[0042] As a buffer layer, a Zr-Cu-Si coating buffer layer can be used, which is achieved by introducing an inert gas (e.g., argon gas) into the physical vapor deposition system and physically depositing the Zr-Cu-Si-based alloy target described above. Specifically, in the coating process of a base material by physical vapor deposition, after mounting an alloy target in a physical vapor deposition system,

[0043] In a vapor deposition chamber, a buffer layer is formed on an upper portion of the base material to a predetermined thickness by a non-reactive physical vapor deposition process while introducing an inert gas into the physical vapor deposition chamber. A nitrogen-containing nanocomposite coating film can then be formed by performing physical vapor deposition while introducing nitrogen gas into the physical vapor deposition chamber. In this case, using the same alloy target, the buffer layer and a nitrogen-containing nanostructure film can be formed in situ. However, the present invention is not limited to this.

[0044] The interface between the buffer layer and the nitrogen-containing nanocomposite coating film can include an interfacial layer in which nitrogen or elements constituting the buffer layer are gradually formed. That is, the composition at the interface changes gradually, rather than drastically, allowing the interfacial layer to be formed with a gradient composition.

[0045] The nitrogen-containing nanocomposite coating film according to the above-described technical idea of the present invention can be applied as a coating film on the surface of a piston pin, a piston ring, or a tappet, which is an engine piston part. An application example thereof will be described below.

[0046] A method for manufacturing a piston pin, piston ring, or tappet coated with the nitrogen-containing nanocomposite coating film according to the technical idea of the present invention includes a step of placing a piston pin, piston ring, or tappet in a physical vapor deposition system, introducing an inert gas, and then introducing a reaction gas containing a nitrogen gas (N2) or a nitrogen element (N) to physically deposit a Zr-Cu-Si-based alloy target, thereby forming a nitrogen-containing nanocomposite coating film on the surface of the piston pin, piston ring, or tappet. In this case, the composition of the alloy target is 82 atomic% to 90 atomic% Zr, 4 atomic% to 14 atomic% Cu, and 4 atomic% to 8 atomic% Si.

[0047] When the deposition is carried out by sputtering of the physical vapor deposition methods, the step of forming the nitrogen-containing nanocomposite coating film on the surface of the piston pin, the piston ring, or the tappet may include: a step of forming the nanocomposite coating film by combining metal ions of the alloy target with nitrogen ions generated from a reaction gas generated by applying a pulse power or DC power in a frequency range of 50 kHz to 350 kHz in a physical vapor deposition plasma source by at least 6 W / cm 2 per unit area to the Zr-Cu-Si based alloy target, while the inert gas and the reaction gas are supplied to a sputtering system and the plasma is discharged.

[0048] Meanwhile, the method for manufacturing a piston pin, a piston ring, or a tappet coated with the nitrogen-containing nanocomposite coating film according to the technical idea of the present invention may further include, before the step of forming the nanocomposite coating film, a step of forming a Zr-Cu-Si coating buffer layer on the surface of the piston pin, the piston ring, or the tappet by introducing an inert gas into the physical vapor deposition system to physically deposit the Zr-Cu-Si-based alloy target.

[0049] For example, in the case of performing sputtering, the step of forming the Zr-Cu-Si coating buffer layer may include a step of forming the Zr-Cu-Si coating buffer layer in which nitrogen ions are combined with metal ions of the alloy target, the nitrogen ions being generated from a reaction gas which is thereby activated while the inert gas and the reaction gas are introduced into a sputtering system, wherein a pulse power or DC power in a frequency range of 50 kHz to 350 kHz is applied in a sputtering plasma source of at least 6 W / cm 2 per unit area to the Zr-Cu-Si based alloy target, thereby discharging plasma.

[0050] Furthermore, the method for manufacturing a piston pin, piston ring, or tappet coated with the nitrogen-containing nanocomposite coating film according to the technical idea of the present invention may include a pretreatment step, before the step of forming the Zr-Cu-Si coating buffer layer, for activating the surface of the piston pin, piston ring, or tappet by introducing an inert gas into an ion gun plasma source in the physical vapor deposition system and applying energy to ionize the inert gas and release ion beams. In this case, the power in the pretreatment step may meet the conditions of a current of 0.3 A to 1.0 A and a voltage of 1000 V to 2000 V.

[0051] The piston pin, piston ring, or tappet implemented by the above-described manufacturing method includes a nitrogen-containing nanocomposite coating film formed on the surface of the piston pin, piston ring, or tappet. The nanocomposite coating film has an all-nitrogen composition consisting of 80 at% to 92 at% Zr, 2 at% to 10 at% Cu, and 5 at% to 15 at% Si. The nitrogen-containing nanocomposite coating film has a friction coefficient of 0.008 to 0.024, while exhibiting a hardness of 10 GPa to 44 GPa and an elasticity of 150 GPa to 450 GPa.

[0052] Examples are provided below to better understand the present invention. However, the following examples are intended only to illustrate the present invention, and the present invention is not limited to the following examples.

[0053] Table 5 shows the composition of a sputtering target and the composition, thickness, roughness, hardness, elasticity, and friction coefficient of a nanocomposite coating film obtained under the physical vapor deposition process conditions according to Examples 1 to 5 and Comparative Examples 1 to 5 of the present invention. Carburized SCM415 was used as the substrate. [Table 5] Alloy composition for 5-inch sputtering target (atomic fraction) Applied voltage (kW) Argon gas flow rate (sccm) Nitrogen gas flow rate (sccm) Reactive sputter coating film composition without nitrogen (atomic fraction) Film thickness (µm) Roughness (Ra, µm) Hardness (GPa) Elasticity (GPa) Fraction coefficient Example 1 Zr 82 The 13,5 Be 4,5 1,52 6 9,5 Zr 83,2 The 9,48 Be 7,23 2 ± 0,2 0,01240 27 310 0,014 Example 2 Zr 84,1 The 10,4 Be 5,5 1,52 6 9 Zr 81,5 The 7,6 Be 10,9 2 ± 0,2 0,01125 26 289 0,016 Example 3 Zr 86,3 The 7,2 Be 6,5 1,52 6 9 Zr 80,3 The 5,7 Be 14 2 ± 0,2 0,01220 23 280 0,019 Example 4 Zr 88,4 The 4,1 Be 7,5 1,52 6 9,5 Zr 82,7 The 2,9 Be 14,4 2 ± 0,2 0,01075 25 265 0,008 Example 5 Zr 89,6 The 3,3 Be 7,1 1,52 6 9,5 Zr 91,3 The 3,5 Be 5,2 2 ± 0,2 0,01075 44 421 0,024 Comparison example 1 Zr 78,4 The 16 Be 5,6 1,52 6 9 Zr 80,45 The 8,35 Be 11,2 2 ± 0,2 0,00997 24 290 0,029 Comparison example 2 Zr 79,9 The 16,6 Be 3,5 1,52 6 9 Zr 80,74 The 13,79 Be 5,47 2 ± 0,2 0,00989 26 280 0,025 Comparison example 3 Zr 85,6 Yes 14,5 1,52 6 10 Zr 73,68 Yes 26,32 2 ± 0,2 0,01072 13 187 0,015 Comparison example 4 Si-DLC (commercial) - - - - 0,01247 18 157 0,033 Comparison example 5 Uncoated tappets (SCM415 carburized) - - - - 0,01057 10 235 0,038 Comparison example 6 Ta-C (commercial) - - - - 0,02133 52 582 0,091

[0054] Sputtering targets according to Example 1 to Example 4 are cast alloys produced by a plasma arc melting process, and a sputtering target according to Example 5 is a sintered alloy produced by a spark plasma sintering process.

[0055] It was confirmed that, according to Example 1 to Example 5, when a sputtering target consisting of 82 at.% to 90 at.% Zr, 4 at.% to 14 at.% Cu, and 4 at.% to 8 at.% Si is placed in a sputtering system, and then an inert gas is introduced into the sputtering system, followed by the introduction of a reaction gas containing a nitrogen gas (N2) or a nitrogen element (N) to physically deposit a Zr-Cu-Si-based alloy target, thereby forming a nitrogen-containing nanocomposite coating film, the nanocomposite coating film has a nitrogen-only composition consisting of 80 at.% to 92 at.% Zr, 2 at.% to 10 at.% Cu, and 5 at.% to 15 at.% Si.

[0056] On the other hand, Comparative Example 1 and Comparative Example 2 are cases where a nanocomposite coating film was formed using a Zr-Cu-Si-based alloy target, but the alloy target did not conform to the composition range described above. Comparative Example 3 corresponds to a case where a coating film was formed using a binary Zr-Si alloy target instead of the Zr-Cu-Si-based alloy target. Comparative Example 4 corresponds to a case where a typical Si-DLC coating film was applied, and Comparative Example 5 corresponds to a case where no coating film was applied.

[0057] Fig.Figure 2 is the result obtained by observing the microstructure of a target sample corresponding to the composition of Example 4 by SEM and BSE. The relative density of the target sample has a very high numerical value of about 99%. Meanwhile, as shown in Fig. As shown in Figure 2, a cast specimen exhibited a dendrite structure. EDS analysis was performed to examine the compositional uniformity of each sample, and it was confirmed that an overall uniform compositional distribution was achieved.

[0058] Fig. 3 is the result obtained by observing the state of the powder by SEM after Zr, Cu and Si powders were introduced into a ball mill to mechanically alloy it to prepare a target sample of the composition according to Example 5, and (a) to (c) from Fig.4 are results obtained by analyzing the composition of the powder by EDS. With reference to Fig. 3 and Fig. 4, it was confirmed that the introduced Zr, Cu and Si powders were alloyed to have a uniform distribution by mechanical alloying. Fig. Figure 5 is the result obtained by analyzing the particle size of the powder subjected to mechanical alloying with a particle size analyzer, and it was confirmed that a uniform particle size was achieved overall.

[0059] Fig.Figure 6 is the result obtained by observing the microstructure of a sample sintered by a spark plasma sintering process using mechanically alloyed powder by SEM. Overall, a uniform microstructure composed of very fine grains was observed, and EDS analysis confirmed that a uniform compositional distribution was achieved overall.

[0060] Fig. Fig. 7 is a view showing the sputtering process conditions for forming a coating film according to Example 2 of the present invention, the XRD analysis conditions, and the results of the analysis, and Fig. Figure 8 is an XRD result of a coating film according to Example 5. Referring to Fig. 7 and Fig.8, it can be confirmed that the prepared coating film has a nanocomposite crystal structure based on ZrN, and it can be seen that the coating film has a ZrN crystal structure as the basic structure, and Cu and Si have a nanocomposite crystal structure included in the ZrN crystal structure.

[0061] (a) and (b) of Fig. 9 show the results obtained by observing the surface and cross section of the coating film by SEM according to Example 5. Referring to (a) and (b) of Fig. 9, the prepared coating film shows a very smooth surface, and it can be seen that the coating film has a columnar structure.

[0062] (a) of Fig. 10 is the result obtained by observing the microstructure of a coating film according to Example 5 by TEM, and (b) of Fig.Figure 10 is the result obtained by performing selected area diffraction analysis (SEAD) thereon. Referring to (a) of Fig. 10 it can be seen that the grains each have a very fine grain size in the range of 5 to 20 nm. In addition, with reference to (b) of Fig. 10 that a ring pattern identified in a nanocomposite coating is shown.

[0063] Referring to Table 5, it can be confirmed that nanocomposite coating films according to Examples of the present invention each have a low friction coefficient of 0.008 to 0.024 with a hardness of 23 GPa to 44 GPa and an elasticity of 265 GPa to 421 GPa. On the other hand, in the nanocomposite coating films according to Comparative Examples of the present invention, it was confirmed that the hardness and elasticity were high, but the friction coefficient was relatively high (Comparative Example 1 and Comparative Example 2), the friction coefficient was low, but the hardness or elasticity was relatively low (Comparative Example 3), or the hardness and elasticity were low and the friction coefficient was high (Comparative Example 4 and Comparative Example 5), and therefore the nanocomposite coating films were not suitable for a low-friction coating film.

[0064] Fig.11 is a view showing the conditions and results of a back-and-forth friction test for coating films according to some examples and comparative examples of the present invention.

[0065] With reference to Fig. 11, it was confirmed that the friction coefficient of the nitrogen-containing nanocomposite coating films according to Examples of the present invention was significantly lower than that of the DLC coating film. Accordingly, it can be confirmed that the low friction properties were more pronounced when the nitrogen-containing nanocomposite coating films according to Examples of the present invention were formed on the base material than when the DLC was formed on the base material.

[0066] Fig.Figure 12 shows the result of a ring liner abrasion resistance test. A test material on which a coating film was to be formed was a piston ring, and the counter-test material was a cylinder liner. A mixture of 5W30 and MoDTC was used as the lubricant. A coating film according to Example 5 was used in the test, and two types of tetrahedral amorphous carbon (TaC) coating films prepared separately, TaC(1) (Comparative Example 7) and TaC(2) (Comparative Example 8), were used as a comparison example. Referring to Fig. 12, it can be confirmed that the coating film according to Example 5 of the present invention has superior properties compared to the properties of Comparative Example 7 and Comparative Example 8.

[0067] Table 6 shows the change in roughness of Example 5, Comparative Example 7, and Comparative Example 8 before and after the liner abrasion resistance test. Referring to Table 6, in the case of the coating film of Example 5, no damage was observed on any liner even after the test, and the surface of the coating film was barely worn. However, in the case of Comparative Example 7 and Comparative Example 8, the change in roughness was significant due to the severe wear of the coating film. [Table 6] sample Before the test Ra (µm) After the test Ra (µm) Example 5 0,26285 0,19 Comparison example 7 0,344 0,099 Comparison example 8 0,300 0,055

[0068] The following describes the results of triboreaction layer analysis of the coating films according to Examples and Comparative Examples of the present invention. The coating according to each of Example 2 and Comparative Example 4 was applied to the surface of a tappet, which was a sample, and a triboreaction layer formed on the surface was analyzed after completion of a reciprocating friction test. The coated tappets were subjected to reciprocating motion for 1 hour in a lubricated state of 5W30 and MoDCT using a high-temperature friction tester. The test was conducted under an applied load of 75 N, a reciprocating motion distance of 10 mm, a speed of 5 Hz (100 mm / sec), and a temperature of 100°C.After the reciprocating friction test, each sample was washed with ethanol for 1 minute in an ultrasonic bath to remove residual lubrication on the surface. To further investigate the friction properties of the triboreaction layer formed on the nanocomposite coating film, the friction coefficient was subsequently measured in a lateral force microscopy (LFM) mode using an AFM device. The LFM measurement conditions were a scanning speed of 0.5 Hz and a load of 10 mN for an area of 20 × 20 μm, and the measured friction coefficient was plotted.

[0069] The principle of LFM is very similar to that of atomic force microscopy (AFM). In the case of AFM, the degree of bending in the vertical direction of a cantilever is measured to collect information about the surface of a sample in a contact mode, whereas in the case of LFM, the degree of bending in the horizontal direction of a cantilever is measured. When the surface of the sample is measured with a cantilever, the degree of bending varies depending on the surface morphology of the sample, the friction coefficient, the direction of movement of the cantilever, and the horizontal spring constant of the cantilever. By measuring the tilt difference of the cantilever on the material surface composed of different components, it is possible to analyze the friction properties of the sample surface.

[0070] Fig. 13A and Fig.13B are an AFM micrograph of a tappet having a coating film according to the example of the present invention and a friction coefficient mapping image by an LFM, respectively. Fig. 14A and Fig. 14B is a friction coefficient mapping image of a tappet having a coating film according to Comparative Example 4 of the present invention using an AFM micrograph and an LFM.

[0071] From the result of the friction coefficient measured by LFM, it can be seen that a tappet on which the nanocomposite coating (Example 2) was deposited has a significantly lower friction coefficient than a tappet on which Si-DLC (Comparative Example 4) was deposited. This is evident from the LFM results of Fig. 13 and Fig.14. From the result of SEM observation to measure the friction ratio of each composition, it was confirmed that a dark area and a bright area of the nanocomposite coating film (Example 2) consisted of Fig. 13A were clearly different. In the case of the coating film (Comparative Example 4) from Fig. 14A, however, there was relatively little difference. The dark area that appeared in the nanocomposite coating film (Example 2) from Fig. 13A is identified as a triboreaction layer, and the bright area is identified as an area where such a triboreaction layer was not formed.

[0072] The triboreaction layer formed by friction has a total thickness of 300 nm to 600 nm, and an organic layer formed at the outermost portion of the reaction layer has a thickness of 2 nm to 100 nm. Fig.Figure 17 illustrates the results obtained by observing the cross section of a friction reaction layer by TEM.

[0073] Images of the friction coefficient mapping measured by LFM are shown in Fig. 13B and Fig. 14B. The coating film from Example 2 has an average friction coefficient of 0.016 and exhibits a low friction coefficient over the entire measured area. In particular, during the friction test, a low friction coefficient was identified in the dark area where solid contact occurs, and a high friction coefficient was identified in the light area. On the other hand, based on Fig.14B, in the case of Comparative Example 4, a high friction coefficient was identified over the entire range, with the average friction coefficient being 0.032, and a low friction coefficient was identified only in a very small part within the measured range.

[0074] The AES measurement was performed for a more detailed component analysis of the triboreaction layer. Fig. 15 is an SEM photograph showing the result of AES analysis of a tappet having a coating film according to Example 2 of the present invention, and Table 7 shows the results of spot analysis for the triboreaction layer for a tappet having the coating film according to Example 2 of the present invention. [Table 7] element Dark phase (atomic %) Bright phase (atomic %) Coating material Cu 14,19 11,06 N 7,23 7,74 Zr 0 7,77 Si 0 1,86 Fe 1,3 2,03 O 27,39 35,44 Contaminated material C 18,8 20,54 S 13,72 4,81 Zn,Na 8,5 5,89 Ca 4,79 0,28 P 2,95 1,66 Mob 1,5 0,91 K 0,08 0

[0075] Fig.16 is an SEM photograph showing the result of AES analysis of a tappet having a coating film according to Comparative Example 4 of the present invention, and Table 8 shows the results of spot analysis for the triboreaction layer for a tappet having the coating film according to Comparative Example 4 of the present invention. [Table 8] element Dark phase (atomic %) Bright phase (atomic %) Coating material C 51,15 38,77 Si 10,75 5,08 Fe 0,98 1,14 Contaminated material O 27,25 26,52 S 6,62 18,57 Zn,Na 2,49 5,14 Ca 0 2,4 P 0,41 1,07 Mob 0,36 0,91 K 0 0

[0076] AES spot analysis was used to perform elemental analysis of a dark area, which is considered to be the triboreaction layer of each sample in the SEM images. Fig. 15 and Fig.16, and a bright area without a triboreaction layer. The results of the AES analysis showed that both the coating layer components and the lubricant compositions were detected over the entire area of the two samples. Table 7 shows the change in the content of the dark area and the bright area of the nanocomposite coating layer (Example 2). One of the coating elements, Cu, showed a higher content in the dark area than in the brighter area, while Zr and Si showed a higher content in the bright area. In addition, S and P, known as the triboreaction layer in the lubrication components, as well as Mo, Ca, and K, which show low friction properties, were detected in a high content in the dark area.

[0077] With reference to Fig.16 and Table 8, in the case of Comparative Example 4, the coating layer compositions C and Si were detected at a high content in the dark region. S, P, Mo, Ca, and K are detected in the light region rather than the dark region. When compared with the results of the nanocomposite coating film (Example 2), the dark region identified in the AES analysis of Si-DLC and the low-friction region of the very small section identified in the friction coefficient mapping by LFM are determined to be residual oil and not a triboreaction layer.

[0078] From the result, it can be confirmed that the copper (Cu) known as solid lubricant soft metal in the nanocomposite coating film according to an embodiment of the present invention reacts with the lubricant composition in the friction test and thus contributes to the formation of the triboreaction layer, resulting in a low friction coefficient.

[0079] Although the present invention has been described with reference to the embodiments shown in the drawings, it is merely exemplary. Those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible. Accordingly, the true technical scope of the inventive concept should be determined by the technical spirit of the appended claims.

Claims

[1] A Zr-Cu-Si based alloy for a physical vapor deposition target for forming a low-friction coating film, the Zr-Cu-Si based alloy comprising 82 at.% to 90 at.% Zr, 4 at.% to 14 at.% Cu and 4 at.% to 8 at.% Si. [2] A physical vapor deposition target formed from a Zr-Cu-Si based alloy to form a low-friction coating film, the target comprising 82 at% to 90 at% Zr, 4 at% to 14 at% Cu, and 4 at% to 8 at% Si. [3] The physical vapor deposition target according to claim 2, wherein the Zr-Cu-Si based alloy is a cast alloy obtained by casting a molten metal. [4] The physical vapor deposition target according to claim 2, wherein the Zr-Cu-Si based alloy is a sintered alloy produced by a sintering method using powder. [5] A physical vapor deposition target according to claim 2, wherein the Zr-Cu-Si based alloy is obtained by performing the following: a step of producing a plurality of amorphous alloys or a plurality of nanocrystalline alloys consisting of 82 atomic% to 90 atomic% Zr, 4 atomic% to 14 atomic% Cu and 4 atomic% to 8 atomic% Si; a step of performing primary shrinkage by pressurizing the plurality of amorphous alloys or the plurality of nanocrystalline alloys while the plurality of amorphous alloys or the plurality of nanocrystalline alloys for a predetermined time at a temperature in the range of the glass transition temperature of the amorphous alloy or the nanocrystalline alloy is kept up to its crystallization start temperature; and a step of performing secondary shrinkage by pressurizing the plurality of amorphous alloys or the plurality of nanocrystalline alloys while maintaining the plurality of amorphous alloys or the plurality of nanocrystalline alloys in a temperature range of 0.7 times to 0.9 times the melting temperature of the amorphous alloy or the nanocrystalline alloy for a predetermined time. [6] A method for producing a nanocomposite coating film, the method comprising a step of forming a nitrogen-containing nanocomposite coating film by introducing an inert gas into a physical vapor deposition system, introducing a reaction gas containing a nitrogen gas or a nitrogen element thereinto to physically deposit a Zr-Cu-Si based alloy target, the alloy target having a composition consisting of 82 at% to 90 at% Zr, 4 at% to 14 at% Cu and 4 at% to 8 at% Si. [7] The method according to claim 6, further comprising, prior to the step of forming a nanocomposite coating film, a step of forming a Zr-Cu-Si coating buffer layer by introducing an inert gas into the physical vapor deposition system for physical deposition using the Zr-Cu-Si based alloy target. [8] The method according to claim 7, further comprising, prior to the step of forming a Zr-Cu-Si coating buffer layer, a pretreatment step of activating the surface of an object on which the Zr-Cu-Si coating buffer layer is to be formed by introducing an inert gas into an ion gun plasma source in the physical vapor deposition system and applying energy to ionize the inert gas and release ion beams. [9] A method according to any one of claims 6 to 8, wherein the step of forming a film or the pretreatment step is carried out in a plasma atmosphere. [10] The method according to claim 6, wherein the nitrogen-containing nanocomposite coating film has, in addition to nitrogen, a composition consisting of 80 atomic% to 92 atomic% Zr, 2 atomic% to 10 atomic% Cu, and 7 atomic% to 15 atomic% Si. [11] Nitrogen-containing nanocomposite coating film, wherein the nanocomposite coating film has a composition consisting of 80 at% to 92 at% Zr, 2 at% to 10 at% Cu and 5 at% to 15 at% Si, except for nitrogen. [12] The nanocomposite coating film according to claim 11, wherein the nanocomposite coating film has a crystal structure based on ZrN or Zr2N. [13] The nanocomposite coating film according to claim 11, wherein, when the nanocomposite coating film comes into contact with and is rubbed against a counter-rotating material, a triboreaction film is formed in at least some regions of the surface of the nanocomposite coating film, and the content of Cu in the regions where the triboreaction film is formed is higher than that in other regions where the triboreaction film is not formed. [14] The nanocomposite coating film according to claim 13, wherein the contents of S and P in the regions where the triboreaction film is formed are higher than in other regions where the triboreaction film is not formed. [15] The nanocomposite coating film according to claim 11, wherein the nanocomposite coating film has a hardness of 10 GPa to 45 GPa and a modulus of elasticity of 150 GPa to 450 GPa.

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