JP2009155721A - Hard coating excellent in sliding property and method for forming same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard coating excellent in wear resistance, insusceptible to seizure, and excellent in sliding property even after use over the long term, and to provided a method for forming the hard coating excellent in sliding property in a short period of time. <P>SOLUTION: The hard coating is a hard coating expressed by chemical formula M<SB>x</SB>B<SB>a</SB>C<SB>b</SB>N<SB>c</SB>, wherein M is at least one of metallic element selected from among elements in the groups 4A, 5A, and 6A of the periodic table, and Si and Al. The hard coating has chemical composition satisfying respective formulas expressed by 0≤a≤0.2, 0≤c≤0.2, 0<x-a-c, x-a-c<b≤0.9, 0.05≤x≤0.5, and x+a+b+c=1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hard film excellent in slidability formed on the surface of, for example, a metal mold or a metal working jig, and a method for forming the hard film.

  Conventionally, for metal molds and metal working jigs, improvement of wear resistance and seizure resistance by nitriding has been promoted. In recent years, instead of the nitriding treatment, improvement of wear resistance and seizure resistance by vapor phase coating such as PVD has been studied.

  For example, Patent Document 1 describes a technique for improving slidability by forming a film made of a composite nitride containing at least two types of metal nitrides of Cr, Ti, Al, and V nitrides. Has been. Patent Document 2 and Patent Document 3 include an underlayer composed of at least one of nitride, carbide, and carbonitride mainly composed of one or more metal elements selected from Ti, V, Cr, Al, and Si. Further, on the surface of the underlayer, the outermost layer mainly composed of Ti, V, Cr, Al, Si, Cu, or the outermost layer comprising one or more of Ti and Cr, the balance being made of a sulfide composed of Mo. A technique for improving wear resistance and seizure resistance by forming a surface layer is described. Furthermore, in Patent Document 4, by forming a surface layer made of molybdenum disulfide or a compound mainly composed of molybdenum disulfide on the surface of the base layer of the high-hardness film made of TiN, TiCN, CrN, or the like, A technique for improving wear resistance and seizure resistance is described.

Patent Document 5 is an invention previously filed by the present applicant. This document includes a component composition (X _c M _1-c ) (B _a C _b N _1-ab ) (M is one or more of W and V, X is a group of 4A, 5A, and 6A). And at least one element selected from Al, Si, Fe, Co, and Ni, and c, 1-c, a, b, and 1-ab are atomic ratios of X, M, B, C, and N, respectively. A technique for improving wear resistance and seizure resistance is disclosed.

  The film made of a composite nitride containing at least two kinds of metal nitrides of Cr, Ti, Al, and V described in Patent Document 1 has high hardness and excellent wear resistance, but is not seized. However, it is not sufficient for use in harsh environments such as when plastic working with high surface pressure is performed. In addition, an underlayer composed of one or more of nitride, carbide, and carbonitride mainly composed of one or more metal elements selected from Ti, V, Cr, Al, and Si described in Patent Document 2, The film in which the outermost layer mainly composed of Ti, V, Cr, Al, Si, and Cu is formed on the surface of the underlayer is also high in hardness and excellent in wear resistance like the film described in Patent Document 1, It is inferior in seizure resistance. In addition, the coatings described in Patent Document 3 and Patent Document 4 are provided with a surface layer made of sulfide formed to improve the seizure property, but the sulfide is relatively soft and is used at the beginning of use. Although it is certain that the slidability is excellent, there is a problem in terms of long-term durability and wear over time with use time.

JP 2000-144376 A JP 2002-307129 A JP 2002-307128 A JP 2000-1768 A JP 2006-124818 A

  The present invention has been made as a solution to the above-mentioned conventional problems, and has a hard film that is excellent in wear resistance, hardly seized, and has excellent slidability even after long-term use. It is an object of the present invention to provide a method for forming a hard film that can form an excellent hard film in a short time.

Invention of claim 1, wherein a hard film represented by the chemical formula _{M x B a C b N c} , M is, 4A Group, 5A Group, at least one selected element Group 6A, and Si, the Al It is a kind of metal element, 0 ≦ a ≦ 0.2, 0 ≦ c ≦ 0.2, 0 <x−a−c, x−a−c <b ≦ 0.9, 0.05 ≦ x <0 .5, x + a + b + c = 1, a hard film excellent in slidability characterized by satisfying the respective expressions. However, x, a, b, and c represent atomic ratios of M, B, C, and N, respectively.

  The invention according to claim 2 is a hard film excellent in slidability according to claim 1, wherein when both the atomic ratios of a and c are 0, 0.1 ≦ x ≦ 0.4 is satisfied. is there.

  According to a third aspect of the present invention, M is W and 0 ≦ a ≦ 0.12, 0.5 <b ≦ 0.8, 0.01 ≦ c <0.15, 0.2 ≦ x <0. 5. The hard film having excellent sliding properties according to claim 1, wherein each of the formulas 5 and 5 is satisfied.

  The invention according to claim 4 is the hard film excellent in slidability according to claim 3, characterized in that the crystal structure includes a mixture of δ-WN and WC1-x.

  Invention of Claim 5 is a formation method of the hard film which forms the hard film of Claim 1 or 2 on the surface of a base material, Comprising: From the metal target which consists of metal element M, or metal elements M and B In a mixed atmosphere of Ar and hydrocarbon gas or Ar, hydrocarbon gas, and nitrogen, a cathode discharge type arc ion plating apparatus is used to move forward substantially orthogonal to the evaporation surface of the target. The hard film is formed by depositing the hard film on the surface of the substrate in a state where magnetic lines of force that diverge or travel in parallel are formed.

According to the sixth aspect of the present invention, when the metal element M is Ti and the hydrocarbon gas is methane (CH ₄ ) gas, the relationship between the methane partial pressure and the arc current density during film formation is The hard film forming method according to claim 5, wherein Pa)> 0.163 + 1.44 × arc current density (A / cm ² ) is satisfied.

  A seventh aspect of the present invention is a method of forming a hard film by depositing the hard film according to the third or fourth aspect on the surface of a substrate, and includes a C-containing gas and nitrogen using a target made of WC. In a mixed atmosphere, with the cathode discharge type arc ion plating apparatus, the hard coating is applied to the surface of the base material in a state where magnetic lines of force that diverge forward or advance in a direction substantially perpendicular to the evaporation surface of the target are formed. And forming a hard film.

  According to the hard film having excellent slidability according to the first aspect of the present invention, wear resistance is exhibited by the formation of carbide of the metal element M, and free C component that does not react with the metal element M is generated. Thus, excellent sliding characteristics such as low μ can be obtained. That is, it is possible to obtain a hard film having excellent wear resistance, hardly causing seizure, and having excellent slidability even when used for a long time.

  According to the hard film having excellent slidability according to claim 2 of the present invention, the amount of C in the film can be relatively increased, and the coefficient of friction can be effectively reduced particularly in a low temperature region. The amount can also be reduced.

  According to the hard film having excellent slidability according to claim 3 of the present invention, it is excellent in lubricity and high hardness, excellent in abrasion resistance, hardly seized, etc. A hard film with excellent properties can be obtained.

  According to the hard film having excellent slidability according to claim 4 of the present invention, WC1-x having excellent slidability and δ-WN having excellent wear resistance are produced in the film. It is possible to obtain a hard coating having an excellent wear balance.

  According to the method for forming a hard coating film according to claim 5 of the present invention, the hydrocarbon gas is introduced in a state where a magnetic field is formed to form a magnetic field line that diverges forward or travels substantially in front of the evaporation surface of the target. Thus, they can be ionized and incorporated into the film, the carbon content in the film can be increased, and a hard film excellent in slidability can be formed in a short time.

  According to the method for forming a hard film according to claim 6 of the present invention, the C content in the film can be set to a suitable atomic ratio so that a free C component that does not react with Ti can be generated without fail. .

  According to the method for forming a hard coating film according to claim 7 of the present invention, film formation is performed by an arc ion plating apparatus in a mixed atmosphere containing a C-containing gas and nitrogen using a target made of WC. It is possible to form a hard film having excellent stability and slidability over time.

  Hereinafter, the present invention will be described in more detail based on embodiments.

First, the hard film of the present invention is a hard film that can be represented by the chemical formula M _x B _a C _b N _c , where M is selected from elements of groups 4A, 5A, and 6A, and Si and Al. At least one metal element having a component composition of 0 ≦ a ≦ 0.2, 0 ≦ c ≦ 0.2, 0 <xac, xac = b ≦ 0. 9, 0.05 ≦ x <0.5 and x + a + b + c = 1 are satisfied. The reason why the component compositions of M, B, C, and N in the hard coating are thus limited will be described below.

  x, a, b, and c are atomic ratios of the metal elements M, B, C, and N, respectively, and a value obtained by adding all the atomic ratios is 1 (that is, 100%). (X + a + b + c = 1)

  First, as described in the column of the effect of the invention, the requirement of the hard coating of the present invention is that wear resistance is expressed by the formation of carbide of the metal element M, and it does not react with the metal element M. The composition is such that excellent sliding characteristics such as low μ can be obtained by generating free C component.

  Considering the reactivity of B, C, and N with the metal element M, since the reactivity with B and N is greater than the reactivity with C, when adding B, C, and N simultaneously, Nitride and boride are preferentially produced, and then the remaining metal elements M and C react to produce carbide. Therefore, in order to generate carbides of the metal elements M and C, atoms of the metal element M not reacting with B and N obtained by subtracting the atomic ratios a and c of B and N from the atomic ratio x of the metal element M The condition is that the ratio xac is greater than zero. (0 <xac)

  In order to generate a free C component, the atomic ratio x-a of the metal element M not reacting with B and N is obtained by subtracting the atomic ratio a and c of B and N from the atomic ratio x of the metal element M. It is a requirement that -c is smaller than the atomic ratio b of C. (X-a-c <b)

  Considering the case where B and N are not added, the atomic ratio b of C needs to be 0.5 or more in order to satisfy the requirement xac-b <b. A more preferable atomic ratio b of C is 0.7 or more. However, when the atomic ratio b of C exceeds 0.9, the atomic ratio x of the metal element M is relatively low, and the proportion of metal carbide, nitride, and boride that plays a role of improving wear resistance is relatively high. Therefore, the atomic ratio b of C needs to be 0.9 or less. (b ≦ 0.9) Preferably, it is 0.8 or less.

  The nitrides and borides of the metal element M are thermally stable compared to the carbides of the metal element M, and the addition of B and N can improve the heat resistance of the film, so B and N are added. Although it is effective to do so, the atomic ratio b of C is relatively low if added over 0.2, so that the atomic ratios a and c of B and N are both 0.2 or less. In order to increase the atomic ratio b of C, it is not always necessary to add B and N, and both the atomic ratios a and c of B and N may be 0. (0 ≦ a ≦ 0.2, 0 ≦ c ≦ 0.2)

  Note that the addition of B and N affects the wear resistance, although it varies depending on the operating temperature range of the mold and jigs on which the hard film is formed. In the temperature range below 400 ° C., the influence is not so great, but in the temperature range above 400 ° C., the wear resistance is surely affected. Therefore, it is recommended to add B or N to a film formed on a mold or jig used in a temperature range of 400 ° C. or higher. By adding at least one of B and N in an atomic ratio of 0.05 or more, the wear resistance at a high temperature of 400 ° C. or more can be remarkably improved.

  The metal element M to be added is at least one metal element selected from elements of Group 4A, Group 5A, Group 6A, Si, and Al, and can form high-hardness carbides, nitrides, and borides. The metal element M is desirable, and it is recommended to add Ti, V, Zr, Nb, Cr, Si alone or a complex element mainly composed of these. Among these metal elements M, Ti and V are particularly recommended as additive elements because they have high hardness and form carbides with a low coefficient of friction.

  In addition, the role of the metal element M is to combine with C, N, and B to form metal carbide, nitride, and boride excellent in wear resistance in the film. x must be at least 0.05, preferably 0.1 or more. However, if the atomic ratio x of the metal element M is 0.5 or more, the expression xac−b <b described above cannot be satisfied, so the atomic ratio x of the metal element M is 0.5. Must be less than Preferably it is 0.3 or less. (0.05 ≦ x <0.5)

  Next, the condition when the atomic ratios a and c of B and N are both 0, that is, when B and N are not added will be described.

  When a = c = 0, the amount of C in the film is relatively increased, and particularly affects the film formed on a mold or jig used in a low temperature range of less than 400 ° C., The friction coefficient is reduced and the friction amount is reduced. When B and N are not added, the preferable atomic ratio of the metal element M is 0.1 to 0.4, and more preferably 0.2 to 0.3.

  Next, a method for forming the hard coating described above will be described.

  This hard film can be obtained by using a metal target consisting of a metal element M and a C target, and simultaneously discharging them to obtain a film having a desired composition. The film formation rate is very slow and takes time. Thus, as a result of intensive studies by the inventor, the inventors have come up with the method for forming a hard coating of the present invention.

  The hard film is formed by using, for example, a cathode discharge type arc ion plating apparatus 1 shown in FIG. 1, and using an arc evaporation source 5, a metal target composed of a metal element M, and a metal element M While evaporating the metal element M from the target 2 such as a composite target made of B, a hydrocarbon gas and further a nitrogen gas are supplied together with Ar, and these are ionized and taken into a film formed on the surface of the substrate 3. By this, it is the formation method of the hard film which can form the hard film excellent in slidability in a short time.

  First, an example of the configuration of the cathode discharge type arc ion plating apparatus 1 will be briefly described with reference to the drawings. As shown in FIG. 1, the arc ion plating apparatus 1 is connected to a vacuum pump (not shown) and supplies an exhaust port 6 for evacuation and a film forming gas such as Ar, hydrocarbon gas, nitrogen gas or the like. Supports a vacuum vessel 8 provided with a gas supply port 7, an arc evaporation source 5 for evaporating and ionizing a target 2 (shown in FIG. 2) constituting a cathode by arc discharge, and a substrate 3 for forming a hard film. And a bias power source 10 for applying a negative bias voltage to the substrate 3 through the substrate stage 9 between the substrate stage 9 and the vacuum vessel 8. In addition, the bias power supply 10 includes a ground 16.

  1, 12 is a filament heating AC power source for applying a voltage to the filament type ion source 13, 14 is a discharging DC power source, and 15 provided at four locations so as to surround the substrate stage 9 is a heater. It is.

  As shown in FIG. 2, the arc evaporation source 5 includes a target 2 constituting a cathode, an arc power source 11 connected between the target 2 and a vacuum vessel 8 constituting an anode, and an evaporation surface 2a of the target 2. And a magnet (permanent magnet) 17 that forms a magnetic field line 4 that diverges forward or travels parallel to the front. The magnet 17 is disposed so as to surround the evaporation surface 2 a of the target 2. The phrase “substantially orthogonal to the evaporation surface 2a of the target 2” means to include a range inclined by about 30 degrees or less with respect to the normal direction of the evaporation surface 2a. The arc evaporation source 5 shown in FIG. 2 will be described as a use evaporation source A in the embodiments described later.

  FIG. 3 shows an example of an arc evaporation source 5 different from FIG. In the arc evaporation source 5, an electromagnet is used as the magnet 17 instead of a permanent magnet. Unlike the case of FIG. 2, the magnet is disposed at a position surrounding the front of the evaporation surface 2 a of the target 2, that is, the front of the base 3 on which the hard film is formed. Even when the magnet 17 is arranged at this location, the magnetic field lines 4 that diverge forward or proceed in parallel are formed substantially orthogonally to the evaporation surface 2a of the target 2 as in the case of using the arc evaporation source 5 shown in FIG. be able to. The arc evaporation source 5 shown in FIG. 2 will be described as a use evaporation source B in the embodiments described later.

  The arc evaporation source 5 shown in FIG. 4 is not the arc evaporation source 5 used in the method for forming a hard film of the present invention, but is an arc evaporation source 5 that has been used in the arc ion plating apparatus 1 conventionally, so that it is used as a reference. explain. In this arc evaporation source 5, a magnet (electromagnet) 17 is arranged on the back side of the target 2 (the side opposite to the base material 3), and the magnetic field lines 4 formed are in the vicinity of the evaporation surface 2 a of the target 2. It is substantially parallel to the evaporation surface 2 a and does not reach the vicinity of the base material 3. The arc evaporation source 5 shown in FIG. 4 will be described as a use evaporation source C in the embodiments described later.

  Since the hard coating of the present invention has a larger atomic ratio of C compared to the atomic ratio of the metal element M, the gas supplied from the gas supply port 7 into the vacuum vessel 8 when forming the hard coating, In particular, it is necessary to efficiently decompose hydrocarbon gas to obtain a C component. For this purpose, a state is formed in which magnetic lines of force that diverge forward or proceed in parallel approximately perpendicular to the evaporation surface 2a of the target 2 are formed. It is preferable. When the cathode discharge type arc ion plating apparatus 1 is used, the electrons e are discharged from the cathode, and the arc-discharged electrons e fly toward the anode. When there is a magnetic field line 4 that diverges forward or travels in a direction substantially orthogonal to 2a, for example, as shown in FIG. 3, the arc-discharged electron e moves around the magnetic field line 4 while performing a spiral motion. To do. In this way, by applying a magnetic field, the trajectory of the electrons e becomes longer, and many collisions with the supplied gas are repeated to promote the decomposition of the ionized / hydrocarbon gas.

  Also, Ar is supplied from the gas supply port 7 into the vacuum vessel 8 together with the hydrocarbon gas and nitrogen gas because the ionized Ar collides with the film being formed, densifies the film, and has high hardness. This is because of The ratio of Ar is preferably 30 to 70 vol% in all the gases to be supplied. More preferably, it is 40-60 vol%. Moreover, it is preferable that the pressure in the vacuum vessel 8 at the time of film-forming is about 0.5-5Pa. If the pressure is lower than 0.5 Pa, the discharge becomes unstable, and if the pressure is higher than 5 Pa, the film formation rate decreases due to gas scattering. The pressure in the vacuum vessel 8 during film formation is more preferably 1 to 3 Pa. Examples of the hydrocarbon gas to be supplied include methane gas, ethylene gas, acetylene gas, toluene gas, and benzene gas.

  Further, in forming the hard coating of the present invention, it is necessary to adjust the atomic ratio of the metal element M so as not to exceed the atomic ratio of C, and this can be dealt with by keeping the arc discharge current low. . That is, the atomic ratio of C in the hard coating varies depending on the arc current density.

The details will be described in an example described later. For example, when the metal element M used for the target 2 is Ti and the hydrocarbon gas to be supplied is methane (CH ₄ ) gas, the methane partial pressure (Pa) and the arc current are set. The density (A / cm ² ) relationship is
Methane partial pressure (Pa)> 0.163 + 1.44 × arc current density (A / cm ² )
It can be expressed by the mathematical formula. By satisfy | filling this numerical formula, the atomic ratio of C in a hard film can be 0.7 or more which is a more preferable atomic ratio of C when B and N are not added. It should be noted that this mathematical formula can also be applied to a target 2 having an equivalent arc current, such as V, and an evaporation amount equivalent to Ti.

  Furthermore, it can be recommended that the metal element M to be added is W. Thus, when the metal element M to be added is W, a WC bond having particularly excellent lubricity and a WN bond with high hardness are generated. Therefore, when the metal element M to be added is W, C and N are essential elements.

  The atomic ratio b of C contained in the hard film needs to be at least more than 0.5, and when it is 0.8 or less, the film has excellent lubricity and low coefficient of friction. A more preferable atomic ratio b of C is 0.55 or more (0.5 <b ≦ 0.8).

  About N, since the W-N bond excellent in abrasion resistance can be produced even with a slight addition, the lower limit of the atomic ratio c of N contained in the hard coating is set to 0.01. A more preferable lower limit of the atomic ratio c of N is 0.02. On the other hand, when N is added too much, the lubricity is lowered, the friction coefficient is increased, and the wear resistance is also lowered. Therefore, the upper limit of the atomic ratio c of N contained in the hard coating is made less than 0.15. (0.01 ≦ c <0.15) The upper limit of the atomic ratio c of N is more preferably 0.1.

  B is an optional element, but can be added because it produces a WB bond with high hardness and also a BN bond having lubricity. However, since the entire coating becomes amorphous due to excessive addition and the hardness thereof decreases, the upper limit of the atomic ratio a of B contained in the hard coating is set to 0.12. The upper limit of the atomic ratio a of B is more preferably 0.05 (0 ≦ a ≦ 0.12). If the sliding temperature is not so high and close to room temperature, a = 0 is recommended.

  The atomic ratio x of W contained in the hard coating is determined by the atomic ratio of C, B, and N described above. When the atomic ratio x of W is less than 0.2, W—C, W—N, Bonds such as WB are reduced and wear resistance is poor. On the other hand, in the case of 0.5 or more, the lubricity is lost and the wear resistance is lowered. Therefore, the atomic ratio x of W contained in the hard coating is in the range of 0.2 or more and less than 0.5. (0.2 ≦ x <0.5) The upper limit of the atomic ratio x of W is more preferably 0.45.

  Depending on the composition ratio (atomic ratio) of these elements, the crystal structure of the film also changes. The crystal structure of the film when N is not added is WC1-x which is excellent in cubic slidability, but the hexagonal δ-WN which is a nitride which is excellent in wear resistance by adding a small amount of N is It is produced in the film.

  The wear resistance and friction coefficient are both good when the film has both WC1-x and δ-WN crystals, and the balance between slidability and wear resistance is good. A mixed film having both −x and δ-WN crystals can be recommended as a good film. The crystal structure of the film is identified by X-ray diffraction.

  Next, a method for forming a hard film in which the metal element M to be added is W will be described.

  In order to form a hard film containing W, in addition to the sputtering method, the arc ion plating method using the arc ion plating apparatus described above can be used, but the sputtering method using a W target is also possible. In the case of forming a hard film, there is a practical problem because the film forming speed is very slow. In the arc ion plating method, when a W target is used, there is a practical problem because W arc discharge is not stable.

  Therefore, as a result of the inventor's extensive research, the inventors have come up with a hard film forming method described below. In the present invention, a hard film containing W can be formed at high speed and with high stability by an arc ion plating method by using a target made of WC as a target when forming a hard film containing W. Revealed.

  As described above, the arc ion plating method is a method for forming a hard film using an arc ion plating apparatus. In brief, the cathode discharge type arc ion plating apparatus 1 shown in FIG. In this method, a film is formed on the surface of the substrate 4 in a state in which the magnetic lines 4 that diverge forward or proceed in parallel substantially perpendicular to the evaporation surface 2a of the target 2 are formed.

In addition, it has been described that a hard film containing W can be formed at high speed and with high stability by an arc ion plating method by using a target made of WC as a target, but only by using a target made of WC, Since there is a tendency for C to escape from the formed hard film, in order to supplement C, the gas is formed in a mixed atmosphere containing nitrogen and a C-containing gas such as methane (CH ₄ ) or acetylene (C ₂ H ₂ ). It is necessary to do a membrane.

  In addition to the C-containing gas and nitrogen, a rare gas such as Ar, Ne, or Xe may be added for discharge stability.

  The partial pressure of the C-containing gas at the time of film formation is preferably set to 0.5 Pa or less because if the partial pressure is excessively high, C is deposited on the surface of the WC target and discharge becomes difficult. More preferably, it is 0.2 Pa or less.

  In addition, the crystal structure of the film changes depending on the bias voltage applied to the substrate during film formation. However, if the bias voltage is too low, the ratio of the δ-WN phase becomes small and the wear resistance cannot be exhibited. On the other hand, when the bias voltage is too high, the energy incident on the base material becomes too high, causing the temperature of the base material to rise, and the ratio of the WC1-x phase becomes small. Therefore, the bias voltage is preferably in the range of −50V to −100V.

  In addition, when forming into a film using not only a WC target but also a metal oxide target made of MC, the atomic ratio b of C contained in the formed film is more than the atomic ratio of C contained in the target. Since there is a tendency to decrease, it is difficult to form a film that satisfies the condition xac-b <b. Therefore, it is necessary to always form a film using a C-containing gas at the time of film formation.

Example 1
Using a metal target composed of the metal element M or a composite target composed of the metal elements M and B, a film having each composition having an atomic ratio shown in Table 1 is formed by a cathode discharge type arc ion plating apparatus as shown in FIG. It formed on the substrate surface. In Example 1, first, in order to confirm the composition of the film and measure the hardness of the film, a cemented carbide whose surface was mirror-polished was used as a base material, and the film of each composition shown in Table 1 on the surface. Formed. For sliding tests, a SKD11 substrate (hardness HRC60) is used as a base material, and a CrN layer having a thickness of 3 μm is formed on the surface of the base material. A film of composition was formed.

First, after setting these substrates on the substrate stage of the arc ion plating apparatus, air is exhausted from the exhaust port by a vacuum pump so that the pressure in the vacuum vessel is 1 × 10 ⁻³ Pa or less. The material was heated to 400 ° C., and then sputter cleaning was performed using Ar ions. Next, a φ100 mm target containing the metal element M (B is a target that evaporates the target and takes it into the film. Therefore, when forming a film containing B, a metal target consisting of only the metal element M is not a metal target. Using a composite target composed of elements M and B), Ar and methane (CH ₄ ) gas are supplied into the vacuum vessel, and in the case of Nos. 8, 9, and 19 to 23, nitrogen is further supplied. The film was formed by setting the partial pressure of methane (CH ₄ ) to 1.5 Pa, the total pressure to 3 Pa, and the arc current to 60 A in a mixed gas atmosphere of Ar—CH ₄ (—N ₂ ). The arc evaporation sources used, that is, the use evaporation sources are the use evaporation source A shown in FIG. 2 and the use evaporation source C shown in FIG. The substrate voltage at the time of film formation is 200V.

  The composition of the film was confirmed by an electron beam microanalyzer (EPDA), and the film hardness was measured using a micro Vickers hardness tester (test load: 0.25 N). If the hardness of the film was 30 GPa or more, it was determined that the film had high hardness and excellent wear resistance. In the sliding test, the coefficient of friction and the wear depth of the film were investigated under the conditions of 25 ° C. (normal temperature) and 400 ° C. without heating. It can be seen that seizure hardly occurs when the friction coefficient is small, and that wear resistance is excellent when the wear depth is small. In addition, about the friction coefficient, it was set as data using the average value of 100m-300m in which the most stable data is obtained in the sliding distance mentioned below. The acceptance criterion for the coefficient of friction was 0.35 or less, and the acceptance criterion for the wear depth was 2.0 μm or less.

  The sliding test apparatus and test conditions used for the sliding test are as shown below. The test results are as shown in Table 1.

Test device: Vane on disk type sliding test device Vane: SKD61 steel (HRC50), 3.5 × 5 mm, length 20 mm, tip radius 10R
Disc: SKD11 steel (HRC60) + coating Sliding speed: 0.2m / sec Load: 500N
Sliding distance: 500m
Test temperature: 25 ° C. (no heating) and 400 ° C.

  The composition (atomic ratio) of the film formed is as shown in Table 1. No. in Table 1 4 to 10, 12 to 15, 17, 19 to 22, and 24 to 29 are films having a composition that satisfies the conditions of claims 1 and 2, and the hardness of each film is as high as 30 GPa or more. Also, the friction coefficient of the film is as low as 0.35 or less under both conditions of 25 ° C. (room temperature) and 400 ° C., and the wear depth of the film is 400 under both conditions of 25 ° C. (room temperature). Even under conditions of ° C., all are as small as 2.0 μm or less. That is, it can be seen that a film having a composition satisfying the conditions described in claims 1 and 2 is excellent in abrasion resistance, hardly seized, and has excellent slidability even when used for a long time.

  In Table 1, No. 4 to 6, 10, 12, and 24 to 29 are films having a composition that satisfies the condition of claim 2. These coatings satisfy the conditions described in claim 1 in which the metal element M in the coating satisfies the same conditions, but when compared with coatings that do not satisfy the conditions described in claim 2, they are 25 ° C. (normal temperature) ), The reduction of the friction coefficient and the reduction of the friction amount are remarkable.

  No. No. 1 is a comparative example in which the film is TiN and C is not contained in the film. In this comparative example, since C was not contained, carbide could not be formed, the hardness of the film was low, and the coefficient of friction and wear depth of the film were 25 ° C. (normal temperature) or 400 ° C. large. As a result, there is a problem with wear resistance, and there is also a problem with slidability.

  No. 2 and 3 are films that do not satisfy the condition of xac−b <b and the condition of 0.05 ≦ x <0.5. With this composition, a free C component could not be produced, and no. Similar to 1, the hardness of the film is low, and the coefficient of friction and the wear depth of the film are large both at 25 ° C. (normal temperature) and at 400 ° C. That is, excellent sliding characteristics such as low μ can be obtained, and there are problems in both wear resistance and sliding properties.

  No. 11 and 18 are films that do not satisfy the condition of b ≦ 0.9. As a result of the atomic ratio of C being excessively high, the atomic ratio of the metal element M is relatively low, and the proportion of metal carbide, nitride, and boride that plays a role in improving wear resistance is relatively low. The film hardness decreased, and the film friction coefficient and wear depth increased. That is, there are problems in both wear resistance and slidability.

  No. 16 is a film that does not satisfy the condition of 0 ≦ a ≦ 0.2. Since B was added exceeding the atomic ratio of 0.2, the atomic ratio of C was relatively low. As a result, the hardness of the film was lowered, and the friction coefficient and wear depth of the film were also 25 ° C. (normal temperature). It became large even under the condition of 400 ° C. below. That is, there are problems in both wear resistance and slidability.

  No. 23 is a film that does not satisfy the condition of 0 ≦ c ≦ 0.2. Since N was added exceeding the atomic ratio of 0.2, the atomic ratio of C was relatively low. As a result, the hardness of the film was reduced, and the friction coefficient and wear depth of the film were also 25 ° C. (normal temperature). It became large even under the condition of 400 ° C. below. That is, there are problems in both wear resistance and slidability.

  In Table 1, the difference between the wear depth under the condition of 25 ° C. (normal temperature) and the wear depth under the condition of 400 ° C. is also described as the wear depth variation (high-low). The film containing B or N has a smaller difference in wear depth when the added metal element M and the atomic ratio are the same as compared with the film containing no B or N. It can be seen that the wear resistance at high temperatures is improved by the addition.

(Example 2)
As a metal target using Ti as the metal element M, the arc current and the methane (CH ₄ ) partial pressure are shown in Table 2 using a cathode discharge type arc ion plating apparatus as shown in FIG. As shown in the drawing, a cemented carbide whose surface was mirror-polished was used as a base material, and a hard film was formed on the surface. The arc evaporation sources used, that is, the use evaporation sources are the three types of the use evaporation source A shown in FIG. 2, the use evaporation source B shown in FIG. 3, and the use evaporation source C shown in FIG. The substrate voltage at the time of film formation is 200V.

In Example 2, the gas supplied into the vacuum vessel was only Ar and methane (CH ₄ ) gas, and the other experimental conditions were similar to those in Example 1. The component composition of the film was confirmed by an electron beam microanalyzer (EPDA). The analysis confirmation results are shown in Table 2.

In Example 2, since all the metal elements M used for the metal target are Ti and the gas supplied into the vacuum vessel is only Ar and methane (CH ₄ ) gas, the hard film formed on the surface of the base material The component composition of all is Ti _x C _b . In Table 2, although only the atomic ratio of C is described as b, all except C are Ti.

No. in Table 2 13, 27, and 28 show the confirmation results obtained by analyzing the component composition of the hard film formed on the surface of the base material under the same conditions of the arc current and the methane (CH ₄ ) partial pressure and changing the evaporation source used. The hard film formed using the used evaporation source A has an atomic ratio C of 0.7, the hard film formed using the used evaporation source B has an atomic ratio C of 0.8, and formed using the used evaporation source C. The hard film has an atomic ratio of C of 0.45. Both the evaporation sources A and B used to form a hard film having a high atomic ratio of C are arc evaporation sources that form magnetic field lines that diverge forward or proceed in parallel substantially perpendicular to the evaporation surface of the target. . In other words, it was verified that the atomic ratio of C in the film can be suitably increased by forming magnetic lines of force that diverge forward or travel in a direction substantially orthogonal to the evaporation surface of the target.

From the test results shown in Table 2, the relationship between the methane partial pressure (Pa) and the arc current density (A / cm ² ) for each specimen was plotted in FIG. Further, the relationship between the methane partial pressure and the arc current density for each atomic ratio of C in the film is obtained by connecting the data points of the experiment and interpolating the points between them, and drawing a contour map. Displayed. The more preferable atomic ratio b of C in the case where B and N are not added is 0.7 or more according to the above description. Therefore, the recommended relationship between the partial pressure of methane and the arc current density is:
Methane partial pressure (Pa) = 0.163 + 1.44 × arc current density (A / cm ² )
It can be seen that the region above the oblique line displayed in FIG.

Therefore, when the metal element M is Ti and the hydrocarbon gas is methane (CH ₄ ) gas, the relationship between the methane partial pressure and the arc current density during film formation is
C content in the film so that a free C component not reacting with Ti can always be produced if methane partial pressure (Pa)> 0.163 + 1.44 × arc current density (A / cm ² ) is satisfied. Can be set to a suitable atomic ratio of 0.7 or more.

  In addition, although this Example 2 showed the case where all the metal elements M used for the metal target were Ti, the above formula was also obtained in the case of a metal target having the same arc current and equivalent to Ti and the evaporation amount, such as V. It is possible to apply. Further, when the evaporation amount is different, it can be dealt with by appropriately correcting.

(Example 3)
A cathode discharge type arc ion plating apparatus as shown in FIG. 1 using a W _0.5 C _0.5 target (hot-pressed product φ100 mm) made of WC as a target and a metal element M as a target. A hard film containing W was formed on the surface.

As conditions for forming a hard coating containing W, the arc current is 150 A, the methane (CH ₄ ) flow rate ratio is changed between 0 and 30 vol%, and the nitrogen (N ₂ ) flow rate ratio is changed between 0 and 30 vol%, respectively. Furthermore, Ar was supplied into the vacuum vessel to adjust the total pressure to 1.33 Pa. No. to which B is added In the case of 15 to 17, it was supplied _B 2 _{H 6} gas in addition the vacuum vessel. The deposition temperature was 400 ° C. and the bias voltage was 100V.

  The film thickness of the formed hard film containing W was 10 μm, and the crystal structure of the film was identified by X-ray diffraction. X-ray diffraction is performed using Cukα as a radiation source, measuring 40 ° V to 40 mA at a range of 10 ° to 100 ° by the θ-2θ method, and identifying the crystal phase from the observed peak. It was.

  The composition of the hard coating containing W was analyzed by an electron beam microanalyzer (EPDA). A sliding test was performed under the same conditions as in Example 1. In this sliding test, the friction coefficient and wear depth of the film were investigated under the conditions of 25 ° C. (normal temperature) and 400 ° C. without heating. It can be seen that seizure hardly occurs when the friction coefficient is small, and that wear resistance is excellent when the wear depth is small. In addition, about the friction coefficient, it was set as data using the average value of 100m-300m in which the most stable data is obtained in the sliding distance mentioned below. The acceptance criterion for the coefficient of friction was 0.35 or less, and the acceptance criterion for the wear depth was 2.0 μm or less. The test results are shown in Table 3.

  The composition (atomic ratio) of the deposited film is as shown in Table 3. No. in Table 3 It was confirmed that 7 to 12 and 14 to 16 are films having a composition satisfying the condition of claim 3 and mixed films having both WC1-x and δ-WN crystals. Also, the friction coefficient of the film is as low as 0.35 or less under both conditions of 25 ° C. (room temperature) and 400 ° C., and the wear depth of the film is 400 under both conditions of 25 ° C. (room temperature). Even under conditions of ° C., all are as small as 2.0 μm or less. Therefore, it was found that the hard film containing W having a composition satisfying the conditions described in claim 3 is excellent in wear resistance, hardly seized, and excellent in slidability even when used for a long time. .

  Furthermore, in the above description, the numbers corresponding to all the ranges indicated as the more preferable ranges of the composition of BCN. 8, 11, 12, 14 and 15, the friction coefficient of the film is 0.25 or less under the condition of 25 ° C. (room temperature) or 400 ° C., and the wear depth of the film is 25 ° C. It was found to be 1.0 μm or less both under normal temperature conditions and at 400 ° C., and was found to be particularly excellent in friction characteristics and wear resistance.

No. From the test results of 1, 5, and 6, the atomic ratio b of C in the film is defined in claim 3 even if a target made of WC is used unless the atmosphere contains C-containing gas (CH ₄ gas). It was confirmed that the range was not reached.

Example 4
In the same manner as in Example 3, the metal element M is W, and a W _0.5 C _0.5 target (diameter is 10 inches) made of WC is used as a target. In a nitrogen atmosphere, a hard film containing W was formed on the surface of the substrate.

  Deposition rate when forming a hard film containing W on the surface of the substrate by this sputtering method and when forming a hard film containing W on the surface of the substrate by the arc ion plating method of Example 3 Compared. The comparison results are shown in Table 4.

  According to Table 4, the arc ion plating method can form a film of 5 μm per hour, while the sputtering method can form a film of 1 μm per hour, and the arc ion plating method is faster. It was confirmed that a hard film containing W could be formed.

(Example 5)
Similarly to Example 3, using a W _0.5 C _0.5 target (hot-pressed product φ100 mm), a cathode discharge type arc ion plating apparatus as shown in FIG. A hard coating was formed.

The conditions at the time of film formation of the hard film containing W are as follows: the arc current is 150 A, the flow rate ratio of methane (CH ₄ ) and nitrogen (N ₂ ) is 10 vol%, and Ar is supplied into the vacuum vessel. The pressure was adjusted to 1.33 Pa. The film forming temperature was changed to 400 ° C. and the bias voltage was changed in the range of −30 to −200 V to form a 10 μm thick film (all atomic ratios were W _0.38 C _0.55 N _0.07 ).

  In order to confirm the slidability of this film, a sliding test was performed under the same conditions as in Examples 1 and 3. In this sliding test, the friction coefficient and wear depth of the film were investigated under the conditions of 25 ° C. (normal temperature) and 400 ° C. without heating. It can be seen that seizure hardly occurs when the friction coefficient is small, and that wear resistance is excellent when the wear depth is small. In addition, about the friction coefficient, it was set as data using the average value of 100m-300m in which the most stable data is obtained in the sliding distance mentioned below. The acceptance criteria for the friction coefficient and the wear depth are 0.35 or less and 2.0 μm or less, respectively, which are the same as in the other examples. In this example, the friction coefficient is 0.25 or less and the wear depth is A thickness of 1.0 μm or less was judged to be more preferable. The test results are shown in Table 5.

  According to Table 5, since the composition (atomic ratio) of the film satisfies the requirements described in claim 3, 1-No. All of 6 satisfy the acceptance criteria. Among them, no. 2-No. No. 4 has a friction coefficient of 0.25 or less under the condition of 25 ° C. (normal temperature) or 400 ° C., and the wear depth of the film is 400 ° C. under the condition of 25 ° C. (normal temperature). Even under conditions, it is 1.0 μm or less. From these results, it was found that the friction characteristics and wear resistance were further improved by setting the bias voltage within the range of −50V to −100V.

(Example 6)
A hard coating containing W on the surface of a substrate using a cathode discharge type arc ion plating apparatus as shown in FIG. 1 using a W _0.5 C _0.5 target (hot-pressed product φ100 mm) or a W target. A test was performed to form

In the case of a W _0.5 C _0.5 target, as conditions for forming a hard coating containing W, the arc current is 150 A, and the methane (CH ₄ ) and nitrogen (N ₂ ) flow rate ratio is 10 vol%, respectively. Further, Ar was supplied into the vacuum vessel to adjust the total pressure to 1.33 Pa. The film forming temperature was 400 ° C., the bias voltage was −70 V, and a 10 μm thick film was formed. (Same conditions as No. 3 in Example 5)

On the other hand, in the case of the W target, the total pressure is 2.66 Pa, the Ar partial pressure is 1.33 Pa, the methane (CH ₄ ) partial pressure is 1 Pa, and the nitrogen (N ₂ ) partial pressure is 0.33 Pa. Was 400 ° C., the bias voltage was −70 V, and a 10 μm thick film was formed.

  When the WC target was used, film formation on the substrate surface could be performed, but when the W target was used, arc discharge did not continue and film formation on the substrate surface could not be performed. That is, when a W target is used, arc discharge is not stable, and a hard coating containing W cannot be formed with good stability. However, a hard coating containing W with good stability can be obtained using a WC target. Can be formed.

It is a schematic sectional drawing which shows typically an example of the cathode discharge type arc ion plating apparatus used for formation of the hard film of the present invention. It is a schematic sectional drawing which shows an example of the use evaporation source of the arc ion plating apparatus. It is a schematic sectional drawing which shows another example of the use evaporation source of the arc ion plating apparatus. It is a schematic sectional drawing which shows the use evaporation source of the conventional arc ion plating apparatus. The metal element M is a Ti, when the hydrocarbon gas is methane (CH ₄₎ gas is an explanatory diagram showing the relationship between the methane partial pressure and arc current density.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Arc ion plating apparatus 2 ... Target 2a ... Evaporation surface 3 ... Base material 4 ... Magnetic field line 5 ... Arc evaporation source 6 ... Exhaust port 7 ... Gas supply port 8 ... Vacuum vessel 9 ... Base material stage 10 ... Bias power supply 11 ... Arc power supply 12 ... Filament heating AC power supply 13 ... Filament type ion source 14 ... Discharge DC power supply 15 ... Heater 16 ... Earth 17 ... Magnet e ... Electron

Claims (7)

A hard film represented by the chemical formula M _x B _a C _b N _c ,
M is an element of Group 4A, Group 5A, Group 6A, and at least one metal element selected from Si and Al.
0 ≦ a ≦ 0.2,
0 ≦ c ≦ 0.2,
0 <x-a-c,
x-a-c <b ≦ 0.9,
0.05 ≦ x <0.5,
x + a + b + c = 1
A hard film excellent in slidability characterized by satisfying each formula of
However, x, a, b, and c represent atomic ratios of M, B, C, and N, respectively. When the atomic ratio of a and c is both 0,
0.1 ≦ x ≦ 0.4
The hard film having excellent sliding properties according to claim 1, wherein: M is W,
0 ≦ a ≦ 0.12,
0.5 <b ≦ 0.8,
0.01 ≦ c <0.15,
0.2 ≦ x <0.5,
The hard coating having excellent slidability according to claim 1, wherein the following formulas are satisfied.   4. The hard film having excellent sliding properties according to claim 3, wherein the crystal structure contains a mixture of δ-WN and WC1-x. A method of forming a hard film, wherein the hard film according to claim 1 or 2 is formed on a surface of a substrate.
Cathode discharge type arc ion plating in a mixed atmosphere of Ar and hydrocarbon gas or Ar, hydrocarbon gas and nitrogen using a metal target composed of metal element M or a composite target composed of metal elements M and B The hard coating is formed on the surface of the substrate in a state in which a magnetic line of force that diverges or advances in a direction substantially perpendicular to the evaporation surface of the target is formed by an apparatus. Method. When the metal element M is Ti or V and the hydrocarbon gas is methane (CH ₄ ) gas, the relationship between the methane partial pressure and the arc current density during film formation is
Methane partial pressure (Pa)> 0.163 + 1.44 × arc current density (A / cm ² )
The method for forming a hard film according to claim 5, wherein: A method of forming a hard film, wherein the hard film according to claim 3 or 4 is formed on a surface of a substrate.
Magnetic field lines that diverge forward or proceed in parallel approximately perpendicular to the evaporation surface of the target by a cathode discharge type arc ion plating apparatus in a mixed atmosphere containing a C-containing gas and nitrogen using a target made of WC In the state which formed, the said hard film is formed into a film on the surface of the said base material, The formation method of the hard film characterized by the above-mentioned.

Images