JP2015218335A - Nitride membrane, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride membrane having a friction coefficient lowered to a level similar to a diamond-like carbon membrane, while keeping abrasion resistance, seizure resistance and thermal resistance, which are characteristics of a nitride.SOLUTION: A nitride membrane 2 is made from a nitride of one or more kinds of metal selected from the group consisting of the groups IV, V, and VI of the periodic table, Al, and Si. A solid lubricant component 3 is dispersed in the nitride membrane 2, the content of the solid lubricant component 3 being 3-23 atm%. The nitride membrane 2 is manufactured by a PVD process under a nitrogen gas atmosphere using a target of the nitride or a metal constituting the nitride and a target of the solid lubricant component.

Description

  The present invention relates to a nitride film containing a solid lubricating component and a method for producing the same.

  A nitride film is hard and has excellent wear resistance and seizure resistance, and is therefore used as a film for various sliding parts (Patent Document 1). In addition, since it is excellent in heat resistance, it is also used as a coating for cutting tools (Patent Document 2).

  In the above applications, diamond-like carbon (hereinafter sometimes referred to as “DLC”) coatings are often used in recent years. The DLC film has excellent characteristics such as excellent wear resistance and a low friction coefficient. On the other hand, when used for cutting iron-based materials or in a use environment such as in a high temperature environment, the characteristics deteriorate and it is difficult to use. Therefore, a DLC film containing silicon has been proposed in order to compensate for such drawbacks (Patent Document 3). However, even a DLC film containing silicon cannot be said to have sufficient heat resistance compared to nitride.

Japanese Patent Laid-Open No. 9-31628 JP 2004-332004 A JP 2007-308753 A

  A nitride mainly composed of Group 4, Group 5, Group 6, Al or Si of the periodic table is a material having high hardness and excellent wear resistance and seizure resistance. Furthermore, since the heat resistance can be used even at 600 ° C. or higher, it is used as a material for a cutting tool or a fuel injection system that becomes a high temperature environment, or an automobile part that becomes high temperature due to oil shortage.

  However, the nitride film tends to have a higher friction coefficient than the DLC film. Therefore, in cutting tool applications, workability improvement and long life are required by reducing cutting resistance. Further, in automotive parts applications, a reduction in friction coefficient is required from the viewpoint of reducing fuel consumption by reducing friction loss.

  The present invention has been made in view of such a situation. That is, an object of the present invention is to provide a nitride film in which the friction coefficient is reduced to the same level as that of the DLC film while maintaining the wear resistance, seizure resistance, and heat resistance that are the characteristics of the nitride film. is there.

  The inventors provide a predetermined amount of a solid lubricating component in a nitride film of one or more metals selected from the group consisting of Group 4, Group 5, Group 6, Al, Si of the periodic table. It has been found that when uniformly dispersed, a solid lubricating component is always supplied to the surface to be worn, which effectively works to reduce the friction coefficient.

  The present invention has been made on the basis of such knowledge, and the present invention has the following configuration.

  The nitride film of the present invention is a nitride film made of a nitride of one or more metals selected from the group consisting of Group 4, Group 5, Group 6, Al, Si of the periodic table. In the nitride film, a solid lubricating component is present in a dispersed state, and the content of the solid lubricating component is 3 to 23 atomic%.

  With such a configuration, it is possible to maintain both wear resistance, seizure resistance, and heat resistance while reducing the wear coefficient.

In the nitride film of the present invention, the nitride may be a nitride of one or more metals selected from the group consisting of Ti, V, Cr, Zr, Nb, Hf, Ta, W, Al, and Si. preferable.
With such a configuration, the wear resistance, seizure resistance, and heat resistance are further improved.

In the nitride film of the present invention, the solid lubricating component is preferably at least one selected from the group consisting of Pb, Sn, Au, Ag, Cu, Ni, Mo, MoS ₂ and PbS.
With such a configuration, the performance is further improved in reducing the wear coefficient.

The method for producing a nitride film according to the present invention is characterized in that a film is formed by a PVD process in a nitrogen gas atmosphere using a target of a nitride or a constituent metal of nitride and a target of a solid lubricating component.
With such a production method, nitride films of various compositions and types can be produced relatively easily.

  The nitride film of the present invention can reduce the friction coefficient to a level equivalent to that of the DLC film while maintaining the wear resistance, seizure resistance, and heat resistance that are the characteristics of the nitride. The nitride film production method of the present invention can produce the nitride film described above.

FIG. 5 is a schematic cross-sectional view showing a dispersion state of a solid lubricating component in a nitride film. It is a schematic diagram of the sliding test method of a nitride film.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the present invention is not limited to the embodiments and drawings as specific examples described below.

(Nitride coating)
In the nitride film of the present invention, since the solid lubricating component is dispersed in the film, the solid lubricating component is always supplied to the surface to be worn, and the friction coefficient is dramatically reduced. Can do.

  Examples of the method for dispersing the solid lubricating component in the nitride film include a method of coating the solid lubricating component only on the outermost surface of the nitride film, and a method of alternately laminating nitride layers and solid lubricating component layers. Can be considered. However, in the former method, since the solid lubricating component is soft, it disappears immediately during sliding, and the effect is not sustained.

  Further, in the latter method, since the disappearance rate of each layer is different in the laminated structure, the soft solid lubricating component layer does not immediately exert an effect, and the friction coefficient is dominated by the value of the nitride layer. Therefore, the effect of reducing the friction coefficient is small. In addition, since the laminated structure has a laminated structure of a hard nitride layer and a soft solid lubricating component layer, a crack is generated in a high surface pressure environment, and the film is easily broken.

  For this reason, the solid lubricating component is present dispersed in the nitride film. As a result, while maintaining the basic characteristics of nitride, such as wear resistance, seizure resistance, and heat resistance, the friction coefficient is reduced by properly supplying the solid lubricating component to the sliding surface. It becomes possible to make it.

  The solid lubricant component in the nitride film is preferably dispersed three-dimensionally, that is, both in the in-plane direction and in the film thickness direction. Even when viewed microscopically, it is preferable to exist in a three-dimensionally dispersed manner, but when viewed macroscopically, a solid lubricating component is always supplied to the sliding surface in a part of the surface. It only has to exist.

  FIG. 1A to FIG. 1D are schematic cross-sectional views showing the dispersion state of the solid lubricating component in the nitride film. In each of FIGS. 1A, 1B, and 1C, the solid lubricating component 3 is three-dimensionally dispersed in the nitride film 2 on the substrate 1. It is shown that. FIG. 1A shows a case where the content of the solid lubricating component 3 is small. FIG. 1B shows a case where the content of the solid lubricating component 3 is large. Although FIG. 1C is close to a laminated structure, the individual solid lubricating components 3 exist in a three-dimensionally independent manner in a dispersed manner. FIG. 1 (d) shows a complete laminated structure of the nitride film 2 and the solid lubricating component 3, and is a comparative example of the present invention.

  The thickness of the nitride film of the present invention is preferably 0.2 to 50.0 μm, although it depends on the application and shape of the part. If the thickness is less than 0.2 μm, the film thickness becomes thin, so that the film may be worn before showing good sliding characteristics, and a sufficient effect cannot be expected. On the other hand, if it exceeds 50.0 μm, the film is too thick and the internal stress of the nitride film is high, so that the film tends to break, resulting in poor durability. More preferably, the lower limit is 0.5 μm and the upper limit is 30.0 μm.

(Nitride)
The nitride of the present invention is a nitride of one or more metals selected from the group consisting of Group 4, Group 5, Group 6, Al and Si in the periodic table. These metal nitrides have excellent performance in terms of wear resistance, seizure resistance, and heat resistance. Specifically, the Group 4 metals in the periodic table are Ti, Zr, and Hf. Specifically, the Group 5 metal is V, Nb, or Ta. Specifically, the Group 6 metal is Cr, Mo, or W.

  In addition, as a constituent metal of nitride, even if it is a metal other than the group consisting of Group 4, Group 5, Group 6, Al, Si of the periodic table, as long as it does not impair the effects of the present invention Appropriate amount can be used. For example, Group 3 Y, Group 8 Fe, Ru, Os, Group 9 Co, Rh, Ir, Group 10 Ni, Pd, Pt, Group 12 Zn, Group 13 Ga, etc. Can be added as needed.

  The nitride is preferably a nitride of one or more metals selected from the group consisting of Ti, V, Cr, Zr, Nb, Hf, Ta, W, Al, and Si. These metal nitrides have better performance in terms of wear resistance, seizure resistance, and heat resistance. One type of metal nitride selected from these groups includes TiN, VN, CrN, ZrN, NbN, HfN, TaN, WN, AlN, SiN, and the like. As the nitrides of two kinds of metals selected from these groups, combinations such as TiAlN, AlCrN, TiCrN, TiSiN, AlSiN, CrSiN, and TiZrN are conceivable, but other combinations may be used. Examples of the nitride of three or more metals selected from these groups include TiCrAlN, TiCrAlSiN, TiCrAlSiYN, and AlCrSiN, but other combinations may also be used. Specific examples of the above-mentioned metal nitrides are more preferable in terms of performance and production.

  From the viewpoint of heat resistance of the nitride, the heat resistance temperature of the film of TiN and CrN is 600 to 700 ° C., and the heat resistance temperature of the film of TiAlN and the like is about 800 ° C. The heat resistant temperature is 1000 ° C. or higher. By the way, in the case of a normal hydrogenated DLC film, the DLC film changes to griffite at about 300 to 400 ° C. and becomes an extremely soft film, resulting in deterioration of wear resistance. Therefore, it cannot be used for parts that require heat resistance.

(Solid lubricant component)
The solid lubricating component of the present invention is preferably at least one selected from the group consisting of Pb, Sn, Au, Ag, Cu, Ni, Mo, MoS ₂ and PbS. These have better properties in reducing the wear coefficient. Each of them functions as a lubricating component sufficiently even if it is a simple substance, but two or more kinds may be mixed and used. Further, when the effect of reducing the wear coefficient is further improved by using a compound such as MoS ₂ or PbS, it may be used as a compound.

  In the present invention, the content of the solid lubricating component in the nitride film is 3 to 23 atomic%. The content of the solid lubricating component is obtained as a ratio of the total amount of the constituent elements of the solid lubricating component when the total amount of the constituent elements of the nitride and the constituent elements of the solid lubricating component is 100 atomic%. Here, as a constituent element, not only a metal element but also the number of atoms of nitrogen and sulfur are counted. However, when a film forming process using an inert gas such as a sputtering method is used, gas components such as argon inevitably contained are also detected, but these are constituent elements of nitride or solid lubricating components. The composition is evaluated by excluding gas components. The content of the solid lubricating component can be measured using an energy dispersive X-ray analyzer (EDX).

  When the content of the solid lubricating component is less than 3 atomic%, the friction reducing effect is not seen, and the friction coefficient is almost the same as that of the nitride alone, while the content of the solid lubricating component is more than 23 atomic%. In such a case, there are too many soft solid lubricating components, and the performance deteriorates from the viewpoint of wear resistance. From the viewpoint of making the friction coefficient reduction and the wear resistance compatible, the lower limit of the content of the solid lubricating component is preferably 5 atomic%, more preferably 10 atomic%. Further, the upper limit of the content of the solid lubricating component is preferably 20 atomic%, more preferably 18 atomic%.

  The solid lubricating component may exist as a mass of atoms on the order of several to several tens of angstroms, or may exist as a precipitate on the order of several tens to several thousand nm. The size of each solid lubricating component varies depending on the film forming method and film forming conditions, and can be controlled to some extent.

  Further, the number of solid lubricating components can be determined from the average size per solid lubricating component and the content of the solid lubricating component. The number density of the solid lubricating component is determined as the number of solid lubricating components per unit volume.

(Manufacturing method of nitride film)
In the present invention, a PVD (Physical Vapor Deposition) method is used as a method for producing the nitride film. This is because the composition and type of the nitride and the composition and type of the solid lubricating component can be easily changed by changing the type and composition of the solid target. Nitride films can also be produced by CVD (chemical vapor deposition) methods, but the film components and compositions that can be formed by the metal-containing gas species used as a raw material are limited, and it is difficult to add solid lubricant components. Therefore, the PVD method is more suitable. Specific examples of the PVD method include an AIP (arc ion plating) method, a sputtering method, and a vacuum deposition method.

  For forming the nitride film, a target of a nitride or a constituent metal of nitride and a target of a solid lubricating component are used. One target may be used for each target, or a plurality of targets may be used. A process is set in a vacuum chamber, evacuated, heated, and etched to form a substrate. At the time of film formation, by introducing nitrogen gas, a nitride film can be produced by reactive film formation using a pure metal or alloy target made of a constituent metal of nitride without using a nitride target. Can do. Further, a plurality of metal targets constituting the alloy may be used without using an alloy target.

  As a method for adding the solid lubricant component to the nitride film, the film is formed while rotating the substrate holder. The rotation of the substrate holder may be revolving or self revolving. When the substrate holder passes in front of the target of the solid lubricant component, by controlling the film formation rate so that the amount formed is less than the thickness of the nitride film, a clear laminated structure is not formed. A nitride film having a structure in which metal particles of the solid lubricating component are three-dimensionally dispersed in the nitride film can be produced. In principle, it is necessary to produce the solid lubricant component at a film formation speed of 1 atomic layer or less. However, even if the thickness is 1 atomic layer or more, the solid lubricant is formed by the effect of heating the substrate. A laminated structure is not formed by aggregation of the lubricant component.

  As mentioned above, although the form for implementing this invention has been described, the Example which confirmed the effect of this invention is described concretely compared with the comparative example which does not satisfy the requirements of this invention below. However, the present invention is not limited to the following examples.

  Film formation was performed using an unbalanced magnetron sputtering (UBM202) apparatus manufactured by Kobe Steel. As the base material, a high-speed steel base material (SKH51: φ34 × t5 mm) whose surface was mirror-polished was used for the sliding test. A pure silicon single crystal wafer was used for film thickness confirmation and composition analysis. Furthermore, a carbide tip (UTi20t: manufactured by Mitsubishi Materials Corporation) was also used for composition analysis.

After introducing the substrate into the apparatus, the substrate is evacuated to 1 × 10 ⁻³ Pa or less. Then, the base material was heated to 300-700 degreeC with the heater installed in the chamber, and it confirmed that temperature became constant. Thereafter, Ar ion bombardment was carried out for 5 minutes in order to clean the substrate surface.

  At the time of forming the nitride film, two types of targets for the nitride film and for the solid lubricating component were used as targets. The target size is φ6 inches.

As the target for the nitride film, Ti, V, Cr, Zr, Nb, Hf, Ta, W, Al, and Si were used as pure metal targets. Further, TiAl, AlCr, TiCr, TiSi, AlSi, CrSi, TiZr, TiCrAl, TiCrAlSi, TiCrAlSiY, and AlCrSi were used as alloy targets. The composition of the alloy target was varied.
Furthermore, as a target for the solid lubricating component, Pb, Sn, Au, Ag, Cu, Ni, and Mo were used as pure metal targets. Moreover, MoS ₂ and PbS were used as compound targets.

As the process gas introduced into the chamber, a mixed gas of argon gas and nitrogen gas was used. The nitrogen content of the nitride was adjusted by controlling the flow rate ratio of Ar and N ₂ gas. The Ar gas: N ₂ gas flow rate ratio was appropriately changed within the range of 1: 4 to 4: 1. Although the total gas pressure at the time of film formation varied depending on the flow rate ratio, all were in the range of 0.6 to 2.0 Pa. About the base-material temperature at the time of film-forming, it controlled to the fixed temperature in the range of 300-700 degreeC. The number of rotations of the substrate was changed within the range of 3 to 10 rpm, and the film formation rate was controlled. At the time of film formation, the amount of solid lubricant component added is fixed by fixing the input power to the target on the nitride film side to 2 kW and changing the input power to the target on the solid lubricant component side from 0.05 to 2.0 kW. Controlled. During film formation, the substrate application bias voltage was unified by applying −100 V using a DC power source.

  The film thickness after film formation is determined by applying a correction liquid onto the Si wafer in advance, removing the correction liquid after film formation, and measuring the step between the base material and the nitride film using a surface roughness meter (Veeco). Manufactured by Dektak 6M). Samples for a sliding test were prepared in advance after calculating the film formation rate, and all the films were formed with an aim of a thickness of 1.0 μm. For composition analysis, measurement was carried out by EDX attached to SEM (S-3500N manufactured by Hitachi, Ltd.).

FIG. 2 is a schematic diagram of a nitride film sliding test method. For the sliding test, a ring-on-disk type sliding test device (Tribot: manufactured by Shinko Engineering Co., Ltd.) was used. As the disk 5, a φ34 × t5 mm SKH51 disk having a nitride film formed on the surface thereof was used (see FIG. 2B). The ring 4 has an outer diameter of 25.58 mm, an inner diameter of 20.0 mm, and is provided with three planar protrusions at 120 ° intervals, and the contact area with the disk 5 is 24.97 mm ^2. A ring 4 made of HRC 65 (the sliding surface is mirror-polished) was used (see FIG. 2A).

  The sliding was tested in the base oil 6 (see FIG. 2 (b)). As the oil, Dynafresia W8 (manufactured by Idemitsu Kosan Co., Ltd.) was used, and the temperature was room temperature. As the sliding condition, as a familiar operation, a load of 100 N was applied and the operation was performed at 100 rpm for 20 minutes. Thereafter, with the rotational speed kept at 100 rpm, the load was increased from 200 N to 100 N, held at each load for 10 minutes, and finally the load was increased to 800 N. As the friction coefficient, an average value of values when held at 800 N for 10 minutes was used.

  Table 1 shows the composition of the nitride film and the evaluation results of the friction coefficient when the nitride film and the solid lubricating component are formed in various combinations. Regarding the wear amount, the nitride film was hardly worn and could not be measured.

  No. 1-3 are comparative examples which do not contain a solid lubricating component. No. Although 1 is a DLC film and not a nitride film, it was carried out for comparison. It can be seen that the DLC film has a lower coefficient of friction than the nitride film. No. Nos. 4 to 8 are obtained by adding Ag as a solid lubricating component to the CrN film. No. In No. 4, the amount of Ag is too small. In No. 8, since there is too much Ag amount, the reduction effect of a friction coefficient is not seen. No. In 5-7, the reduction of the friction coefficient was confirmed.

  No. Nos. 9 to 13 are obtained by adding Au as a solid lubricating component to the CrN film. No. In No. 9, the amount of Au is too small. In No. 13, since there is too much Au amount, the effect of reducing the friction coefficient is not seen. No. In 10-12, reduction of the friction coefficient was confirmed.

No. Nos. 14 to 18 are obtained by adding MoS ₂ as a solid lubricating component to the CrN film. No. In No. 14, the amount of MoS ₂ is too small. In No. 18, since the amount of MoS ₂ is too large, the effect of reducing the friction coefficient is not observed. No. In 15-17, reduction of the friction coefficient was confirmed.

  No. Nos. 19 to 23 are obtained by adding Ag as a solid lubricating component to the TiN film. No. In No. 19, the amount of Ag is too small. In 23, since there is too much Ag amount, the reduction effect of a friction coefficient is not seen. No. In 20-22, reduction of the friction coefficient was confirmed.

  No. Nos. 24 to 29 are obtained by adding various solid lubricating components to the CrN film in the range of 13 to 18 atomic%. A reduction in the coefficient of friction was confirmed for all solid lubricating components.

  No. 30 to 47 are obtained by adding Ag as a solid lubricating component to a nitride film containing two or more metal components. It can be seen that in any nitride, the friction coefficient is reduced by adding an appropriate amount of the solid lubricating component. No. Nos. 48 to 51 are obtained by adding Ag and Sn as solid lubricant components to the TiAlN film. It was confirmed that the friction coefficient is not reduced unless the addition amount is appropriate.

1 Base Material 2 Nitride Film 3 Solid Lubricating Component 4 Ring 5 Disc 6 Base Oil

Claims (4)

A nitride film made of a nitride of one or more metals selected from the group consisting of Group 4, Group 5, Group 6, Al, Si of the Periodic Table,
In the nitride film, a solid lubricating component is present dispersed,
A nitride film, wherein the content of the solid lubricating component is 3 to 23 atomic%.   2. The nitride according to claim 1, wherein the nitride is a nitride of one or more metals selected from the group consisting of Ti, V, Cr, Zr, Nb, Hf, Ta, W, Al, and Si. The nitride film as described. The solid lubricant component is at least one selected from the group consisting of Pb, Sn, Au, Ag, Cu, Ni, Mo, MoS ₂ , and PbS. Nitride film. It is a manufacturing method of the nitride coat given in any 1 paragraph of Claims 1-3,
A method for producing a nitride film, comprising forming a film by a PVD process in a nitrogen gas atmosphere using a target of a nitride or a constituent metal of nitride and a target of a solid lubricating component.

Images