WO2016111288A1

WO2016111288A1 - Diamond-like carbon layered laminate and method for manufacturing same

Info

Publication number: WO2016111288A1
Application number: PCT/JP2016/050115
Authority: WO
Inventors: 弘高伊藤
Original assignee: 株式会社神戸製鋼所
Priority date: 2015-01-09
Filing date: 2016-01-05
Publication date: 2016-07-14
Also published as: JP2016128599A

Abstract

The present invention pertains to a laminate in which a DLC layer is formed on a metallic substrate with an intermediate layer therebetween, wherein the intermediate layer comprises a first layer and a second layer in that order from the substrate, the first layer is made of Cr, and the second layer is made of Cr and carbon. Furthermore, the intermediate layer has a composition gradient structure in which carbon content increases and Cr content decreases from the substrate toward the DLC layer, and the ratio of carbon to the sum of Cr and carbon at the surface of the second layer contacting the DLC layer is 80 at% or less.

Description

Diamond-like carbon layer laminate and manufacturing method thereof

The present invention relates to a diamond-like carbon layer laminate and a method for producing the same. In particular, the present invention relates to a laminate in which a diamond-like carbon layer is formed on a metal substrate with good adhesion. Hereinafter, the “diamond-like carbon layer” may be referred to as a DLC (Diamond Like Carbon) layer. Further, the “diamond-like carbon layer laminate” may be referred to as “DLC layer laminate” or simply “laminate”.

Since diamond-like carbon is a hard material with a low coefficient of friction, it has excellent durability and can reduce friction loss. Therefore, the DLC layer is applied in various fields including automobiles, machine parts, and medical devices. On the other hand, since the DLC layer has particularly low adhesion to a metal substrate, it is easy to peel off even if directly formed on the metal substrate and lacks practicality. Hereinafter, the metal substrate is simply referred to as “substrate”.

Therefore, in consideration of practicality, an intermediate layer is formed between the base material and the DLC layer in order to ensure adhesion with the base material. For example, in Patent Document 1, as the intermediate layer, a base layer-side first layer made of Cr and / or Al metal, and an outermost surface layer made of an amorphous layer containing Cr and / or Al metal and carbon. An intermediate layer having a two-layer structure composed of a second layer on the side has been proposed.

In Patent Document 2, as the intermediate layer, a first layer on the substrate side made of one or more metal layers selected from the group consisting of W, Ta, Mo and Nb, and W, Ta, Mo and Nb An intermediate layer having a two-layer structure composed of a second layer on the outermost surface layer side composed of an amorphous layer containing one or more metal elements selected from the group and carbon is proposed.

Patent Document 3 proposes an intermediate layer having a four-layer structure in which the following four layers (1) to (4) are formed in the described order from the base material side to the outermost surface layer side as the intermediate layer. ing.
(1) First layer made of a metal layer of Cr and / or Al (2) Mixed layer of a metal of Cr and / or Al and one or more metals selected from the group consisting of W, Ta, Mo and Nb The second layer (3) consisting of W, Ta, Mo and Nb selected from the group consisting of one or more metal layers (4) selected from the group consisting of W, Ta, Mo and Nb A fourth layer comprising an amorphous layer containing one or more metals and carbon

Japanese Unexamined Patent Publication No. 2002-256415 Japanese Unexamined Patent Publication No. 2000-119843 Japanese Unexamined Patent Publication No. 2003-171758

As described above, various intermediate layers have been proposed to ensure adhesion between the substrate and the DLC layer. Even if the intermediate layer described in Patent Document 1 or Patent Document 2 is formed, a certain degree of adhesion can be secured. However, when the usage environment is severe, for example, when the surface is used at a high surface pressure; or when the DLC layer is thickened and as a result, the internal stress of the DLC layer becomes large; May peel. In addition, the intermediate layer of Patent Document 3 is a film that has been proposed so that it can be used even when the DLC layer is thick. However, since it has a complicated structure, it seems that improvement is necessary from the viewpoint of productivity.

The present invention has been made paying attention to the circumstances as described above, and its purpose is high adhesion between the base material and the DLC layer, particularly when the use environment is severe as described above or when the DLC layer is thick. Even so, the object is to realize a diamond-like carbon layer laminate that has high adhesion between the substrate and the DLC layer and that can be formed with high productivity without a complicated structure. Hereinafter, “adhesion between the substrate and the DLC layer” may be simply referred to as “adhesion”.

The diamond-like carbon layer laminate of the present invention that has solved the above problems is a laminate in which a diamond-like carbon layer is formed on a base material via an intermediate layer, and the intermediate layer comprises the base The first layer provided on the material and the second layer provided on the first layer, the substrate is made of metal, the first layer is made of Cr, and the second layer is made of Cr. Of the surface in contact with the diamond-like carbon layer of the second layer, and having a composition gradient structure in which Cr increases and Cr decreases from the base material side toward the diamond-like carbon layer side. The ratio of carbon to the total of Cr and carbon is 80 atomic% or less.

The ratio of carbon to the total of Cr and carbon on the surface in contact with the diamond-like carbon layer of the second layer is preferably 40 atom% or more and 80 atom% or less.

The film thickness of the intermediate layer is preferably 0.05 μm or more and 1.0 μm or less.

The present invention also includes a sliding member provided with the diamond-like carbon layer laminate.

The present invention includes a method for producing the diamond-like carbon layer laminate. The manufacturing method is characterized in that the intermediate layer is formed by a PVD method and the diamond-like carbon layer is formed by a PVD method or a CVD method.

According to the present invention, a DLC layer laminate having a high adhesion between the substrate and the DLC layer, particularly when the use environment is severe or the DLC layer is thick, Can be provided. This DLC layer laminate can be formed with high productivity since the intermediate layer is not a complicated structure as in Patent Document 3.

The present inventor conducted intensive studies to obtain a molded article having excellent adhesion between the base material and the DLC layer even in a severe use environment or when the DLC layer is thickened. Many techniques for providing a composition gradient layer between a substrate and a DLC layer have been proposed so far in order to improve adhesion. However, the present inventor refocused on the composition of the composition gradient layer and studied to further improve the adhesion between the substrate and the DLC layer.

As a result, the following knowledge was obtained. That is, conventionally, it has been recommended that the surface of the intermediate layer in direct contact with the DLC layer be 100% carbon. This means that in the paragraph [0026] of Patent Document 1 and the paragraph [0019] of Patent Document 2, “the metal is stepped from the first layer side (base material side) to the DLC layer side (surface layer side) It is preferable to use a gradient composition that continuously decreases (that is, the carbon concentration increases from 0% to 100%) By adopting such a film configuration, the mechanical properties of the multilayer film can be increased from the substrate side to the DLC. It can be changed stepwise or continuously to the side, thereby preventing peeling due to local stress concentration due to thermal shock or the like. " However, in this case, sufficient adhesion cannot be obtained in the above severe use condition; rather, adhesion is increased by suppressing the carbon ratio of the surface of the intermediate layer in direct contact with the DLC layer to a certain level or less; The present invention has been completed.

Hereinafter, the intermediate layer which is a characteristic part of the present invention will be described including this point.

About the intermediate layer The intermediate layer of the present invention has a laminated structure comprising a first layer provided on a substrate and a second layer provided on the first layer.

In the present invention, Cr is used as a metal element constituting the intermediate layer in order to increase the bonding strength with the metal substrate surface. Specifically, the first layer is made of Cr, and the second layer is made of Cr and carbon. The second layer has a composition gradient structure in which carbon increases from the base material side toward the DLC layer side and Cr decreases.

By making the second layer have the above-described composition gradient structure, the bonding force with Cr constituting the first layer can be increased at the interface with the first layer, and the bonding force with the DLC layer at the interface with the DLC layer. Can be increased. Specifically, by setting the surface of the second layer in contact with the first layer to Cr 100 atomic%, a high bonding strength with the first layer can be obtained, that is, high adhesion with the metal substrate can be obtained. Further, as described above, the composition gradient structure in which carbon increases and Cr decreases as it goes from the substrate side to the DLC layer side increases affinity with the DLC layer. However, as described above, in the present invention, the interface between the intermediate layer and the DLC layer is not increased to 100 atomic% of carbon, but the ratio of carbon to the total of Cr and carbon is suppressed to 80 atomic% or less. There are features. Hereinafter, “the ratio of carbon to the total of Cr and carbon” may be simply referred to as “carbon ratio”.

The reason why the adhesiveness is increased by suppressing the carbon ratio in this way is not clear enough, but can be considered as follows from the results of Examples described later. That is, when the carbon ratio is higher than 80 atomic%, there is no problem with the bonding force with the DLC layer, but a portion with low hardness is easily formed. For example, when used at a large surface pressure, cracks are likely to occur in the low hardness portion, and as a result, the DLC layer is likely to be peeled off.

The carbon ratio is preferably 75 atomic percent or less, and more preferably 70 atomic percent or less.

On the other hand, if the carbon ratio is too low, the composition gradient of the second layer is too small to achieve the original purpose of the composition gradient layer. That is, the bonding force between the second layer and the DLC layer becomes weak, and the possibility of peeling from the interface between the second layer and the DLC layer increases. Therefore, the carbon ratio is preferably 40 atomic% or more. The carbon ratio is more preferably 45 atomic% or more, further preferably 50 atomic% or more, and still more preferably 55 atomic% or more.

About the film thickness of an intermediate | middle layer From the viewpoint of ensuring adhesiveness with a base material, the film thickness of the said 1st layer becomes like this. Preferably it is 0.01 micrometer or more, More preferably, it is 0.03 micrometer or more. On the other hand, since the first layer is soft, the thickness of the first layer is preferably 0.4 μm or less, more preferably 0.3 μm or less from the viewpoint of suppressing deformation in a high surface pressure environment. is there.

The film thickness of the second layer is preferably 0.02 μm or more, more preferably 0.1 μm or more, from the viewpoint of ensuring adhesion with the DLC layer. When the film thickness is thinner than 0.02 μm, the gradient of the gradient composition becomes steep, and cracks are generated starting from the gradient composition layer having a steep composition gradient, which may lead to peeling of the DLC layer. On the other hand, since the second layer has an inclined structure, if the film thickness becomes too thick, the soft layer containing a large amount of Cr may increase and deform in a high surface pressure environment. From the viewpoint of preventing the deformation, the thickness of the second layer is preferably 0.8 μm or less, and more preferably 0.6 μm or less.

The total film thickness of the first layer and the second layer, that is, the film thickness of the intermediate layer is preferably in the range of 0.05 μm to 1.0 μm. The film thickness is more preferably 0.10 μm or more, and still more preferably 0.20 μm or more. On the other hand, when the film thickness is greater than 1.0 μm, the proportion of the intermediate layer made of a Cr layer or a Cr—C gradient composition layer having a lower hardness than the DLC layer tends to increase. As a result, in a use environment where the surface pressure is large, cracks may occur starting from this thick intermediate layer, which may lead to peeling of the DLC layer. Therefore, the film thickness is preferably 1.0 μm or less, more preferably 0.80 μm or less, and still more preferably 0.75 μm or less. Hereinafter, the total film thickness of the first layer and the second layer is referred to as “intermediate film thickness”.

The ratio of the thickness of the first layer to the thickness of the second layer is preferably in the range of 1st layer: 2nd layer = 1: 1 to 1:25.

DLC layer The present invention does not define the specific composition of the DLC layer, and various DLC layers can be used. For example, aC: H which is amorphous hydrogenated carbon, aC which is amorphous carbon, ta-C: H which is hydrogenated tetrahedral amorphous carbon, ta-C which is tetrahedral amorphous carbon, or those X-DLC added with an element X other than carbon and hydrogen, which contains metal, or a DLC layer having a laminated structure of any two or more of the above can be used.

The DLC layer of the present invention may contain one or more elements X other than carbon and hydrogen in order to control the friction coefficient and wear resistance. Examples of the element X include B, N, O, F, Al, Si, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, and Ru. , Ag, Sn, Sb, Ta, W, Ir, Pt, Au, Pb, Bi, etc. may be used alone or in combination of two or more, for example, within a range of 30 atomic% or less of the entire DLC layer.

The film thickness of the DLC layer is not particularly limited, and can be, for example, 0.5 μm or more and 50.0 μm or less. As described above, according to the configuration of the present invention, even when a relatively thick DLC layer is formed, the adhesion between the DLC layer and the substrate is excellent. For example, the thickness of the DLC layer is preferably 1.5 μm or more, more preferably 1.8 μm or more, and further preferably 2.0 μm or more. Thus, even when the film thickness of the DLC layer is thick, excellent adhesion to the substrate can be maintained, and the effects such as wear resistance of the DLC layer are fully exhibited. Of course, an extremely thin film can be formed as the DLC layer.

In the DLC layer laminate of the present invention, in addition to the case where the DLC layer is formed as the outermost surface layer, another layer may be provided on the DLC layer. As another layer, for example, a low hardness layer may be provided as the conforming layer. Examples of the low-hardness layer include a low-hardness DLC layer and a DLC layer containing the element X as described above. By providing the low hardness layer as the conforming layer, an increase in the friction coefficient immediately after the start of sliding can be suppressed. Further, as the other layer, for example, a conventionally used solid lubricant such as MoS ₂ may be formed.

About the substrate The substrate is not particularly limited as long as it is a metal. For example, carbon steel for machine structure, alloy steel for structure, tool steel including high speed steel HSS, bearing steel, stainless steel, cast iron and the like can be used as the iron base material. Further, as metals other than iron-based metals, Al, Ti, Cu pure metals and alloys; W pure metals and alloys; WC-based cemented carbides can be used. In addition, the substrate may be subjected to carburizing treatment, nitriding treatment, anodizing treatment, plating treatment, or the like in order to increase the strength of the substrate.

The present invention also includes a sliding member provided with the DLC layer laminate. It suffices that the DLC layer laminate of the present invention is provided on at least the sliding surface of the sliding member. The DLC layer laminate of the present invention can be suitably used for various parts such as molds, cutting tools, wear-resistant mechanical parts, magnetic / optical parts and the like in addition to the sliding members.

Next, a method for producing the DLC layer laminate of the present invention will be described. The DLC layer laminate of the present invention is characterized in that the intermediate layer is formed by a PVD (Physical Vapor Deposition) method, and the DLC layer is formed by a PVD method or a CVD (Chemical Vapor Deposition) method. Hereinafter, the production method of the present invention including these methods will be described.

First, the following example is given as a procedure up to the formation of the intermediate layer. A substrate is prepared as an object to be processed, and is subjected to various cleaning processes such as degreasing, ultrasonic cleaning with acetone, ethanol, and the like, and drying of a cleaning liquid. Thereafter, the substrate is mounted in a vacuum chamber of the film forming apparatus, and evacuation is performed as necessary. The degree of vacuum is preferably evacuated to a level of 10 ⁻² Pa or less from the viewpoint of preventing the mixing of impurity components. However, depending on the object to be processed, the influence of impurities may not be considered. Not required.

¡Ar ion bombardment is performed to clean moisture adsorbed on the surface of the metal substrate and components remaining in the cleaning process, such as impurities derived from rust preventive oil. Before the Ar ion bombardment, a step of heating the inside of the chamber or between 100 to 1200 ° C. may be provided in order to evaporate the moisture adsorbed on the inside of the chamber or the substrate surface.

The inert gas for bombardment is cheap and easily available Ar gas. The purity of Ar gas is preferably 99.9% or more, but there is no problem even if it is less than that. First, Ar gas is introduced into the vacuum chamber and waits until the gas pressure reaches a predetermined pressure of 0.2 Pa to 4 Pa. The pressure can be arbitrarily changed. After reaching a predetermined pressure, by applying a current of 2 to 20 A from an external power source to the tungsten filament installed in the vacuum chamber, the tungsten filament becomes red hot and emits thermoelectrons. Ar ions are ionized by collision of the thermal electrons with Ar gas. The ionized argon is drawn into the substrate when a negative voltage is applied to the substrate, and the argon ion strikes the substrate surface to clean the substrate surface. The above description is a method when a normal DC (Direct Current) voltage or a pulsed DC voltage is applied to the substrate.

In order to further enhance the effect of bombardment, there is a method in which a plurality of base materials are used and an AC voltage is applied between the base materials by an external power source. When the above-described normal DC voltage or pulse DC voltage is applied, argon ions move only between the tungsten filament and the substrate. On the other hand, according to the method of applying an AC voltage between the base material and the base material by an external power source, in addition to the movement of the argon ions, the argon ions and electrons between the base material and the base material Communication is accelerated. Thereby, when a negative bias is applied to one of the substrates, the effect of argon ion bombardment on the substrate is enhanced, while a positive bias is applied to the other substrate, and the surface is modified by electron irradiation. Specifically, the surface is activated by electron beam irradiation to become a highly reactive surface. That is, according to this method, the substrate surface cleaning and modification effects can be sufficiently enhanced. Further, by using an AC power source, the negative bias and the positive bias described above are alternately applied, and the cleaning and reforming effects on the substrate surface are accelerated. When the AC power supply is used, the above effect can be obtained by applying the applied voltage within the range of the power supply set value of 350V to 1600V.

About the formation method of an intermediate | middle layer An intermediate | middle layer is formed by PVD method as above-mentioned. This is because the Cr layer as the first layer cannot be formed by a CVD method in which a gas is decomposed to form a film. It is effective to use a Cr target having a purity of 99% or more for forming the Cr layer. As the PVD method, it is effective to use a sputtering method including an unbalanced magnetron sputtering (UBMS) method, an arc ion plating (AIP) method, a vacuum deposition method, or the like.

Further, the gradient composition layer as the second layer can be formed by the following method. For example, by using a Cr target as the target and introducing a hydrocarbon gas such as methane, acetylene, benzene, toluene, etc. as the film forming gas, and gradually increasing the amount of introduction, the Cr—C gradient composition The method of forming a layer is mentioned. As another method, a Cr target and a C target are used as targets. In this case, for example, Ar gas is used as an atmospheric gas, and the film formation rate of Cr is reduced. A method of increasing the film formation rate of carbon, specifically, for example, increasing the input power of the carbon target. Further, as another method, a film forming method using a Cr target and a C target as targets and also using a hydrocarbon gas as a carbon supply source can be considered. As described above, it is effective to use a Cr target having a purity of 99% or more as the Cr target.

When the intermediate layer is formed, that is, when the first layer and the second layer are formed, the target component can be effectively adhered to the substrate by applying a negative bias to the substrate by a bias power source. Further, the density of the film can be controlled by controlling the bias voltage. Since the dense film has high deformation resistance, the possibility of breaking when an external force is applied is reduced. That is, adhesion is also improved. In order to improve the adhesion, the negative bias voltage is preferably smaller than −40V, that is, a value having a large absolute value. On the other hand, if the value is smaller than −1000 V, the effect of the bias is too strong, and the formed intermediate layer is easily etched, and the deposition rate is extremely reduced. As a result, the adhesion tends to decrease. Therefore, it is preferable that the negative bias voltage is larger than −1000 V, that is, a value having an absolute value smaller than −1000 V.

As other film formation conditions, for example, the film formation conditions of the first layer and the second layer can be as follows. That is, the substrate temperature can be in the range of room temperature to 200 ° C. The total pressure can be in the range of 0.1 to 5.0 Pa, and the partial pressure can be adjusted so that the amount ratio of Ar is in the range of 100 to 30%. The power applied to the target can be in the range of 0.1 to 5.0 kW.

About the formation method of a DLC layer Either the PVD method or CVD method may be sufficient as the formation method of a DLC layer. As the PVD method, an AIP method, a sputtering method, or the like can be used. By forming DLC using a solid carbon target as a main raw material, a DLC layer not containing hydrogen can be formed. Alternatively, a DLC layer containing hydrogen can be formed by introducing a hydrocarbon gas during film formation. When a DLC layer to which an element other than carbon and hydrogen is added is formed by the PVD method, a target containing the element can be used.

In the case of forming by the CVD method, a DLC layer is formed by decomposing the hydrocarbon gas by applying a voltage or electric power to the base material with the hydrocarbon gas as a main component and decomposing the hydrocarbon gas. Any of DC, pulsed DC, and AC (Alternating Current) may be used as a method for applying voltage or power to the substrate. When the DLC layer to which elements other than carbon and hydrogen are added is formed by this CVD method, in addition to the hydrocarbon gas, a gas containing silicon, various metal components, or oxides thereof can be used. .

Examples of film forming conditions for forming by the CVD method include the following conditions. The substrate temperature can be in the range of room temperature to 200 ° C. In general, the substrate is not heated, and the substrate is not heated in the examples described later, but the substrate temperature can rise to, for example, about 50 to 200 ° C. during film formation. However, when the substrate temperature exceeds 250 ° C., DLC softening occurs, which is not preferable.

The total pressure during film formation by the CVD method can be in the range of 0.5 to 20 Pa. Increasing the total pressure increases the film formation rate, but tends to cause problems such as a decrease in hardness and an increase in surface roughness. The partial pressure may be adjusted so that the hydrocarbon gas such as acetylene and methane is in the range of 100 to 30%, and the rest is an inert gas such as Ar. When an inert gas is contained, the film formation rate decreases but the hardness tends to increase. On the other hand, an excessive amount of inert gas is not preferable because the film forming rate is extremely lowered.

The applied voltage during film formation by the CVD method can be in the range of 500V to 2000V. If this applied voltage is too low, plasma is not generated. On the other hand, if it is too high, abnormal discharge occurs frequently and the plasma is not stable.

For example, the following conditions may be cited as film forming conditions when forming by the PVD method. The substrate temperature can be in the range of room temperature to 200 ° C. In general, the substrate is not heated, and the substrate is not heated in the examples described later, but the substrate temperature can rise to, for example, about 50 to 200 ° C. during film formation. However, when the substrate temperature exceeds 250 ° C., DLC softening occurs, which is not preferable.

The total pressure during film formation by the PVD method can be in the range of 0.1 to 2.0 Pa. In addition, the partial pressure may be adjusted so that the amount ratio of Ar is in the range of 50% or more and less than 100%. More preferable conditions include, for example, a total pressure of 1.0 Pa, a hydrocarbon gas such as methane of 1 to 10% and the balance of Ar.

The voltage applied to the target during film formation by the PVD method can be 0.1 to 5.0 kW. Also, the negative bias voltage applied to the substrate can be in the range of 50 to 400 V in absolute value. By increasing the absolute value of this negative bias voltage, the hardness of the film can be increased and the wear resistance can be increased. On the other hand, if the absolute value of the negative bias voltage is too high, an etching effect occurs and the film formation rate tends to be extremely reduced.

As conditions for the AIP method, for example, the arc current can be in the range of 10 to 100 A, and the Ar gas can be in the range of 0 to 100%.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

The intermediate layer was formed using an unbalanced magnetron sputtering apparatus manufactured by Kobe Steel, Ltd., trade name: UBMS202. The substrate used was JIS SKH51 with a mirror polished surface and an HRC of 65.

First, the substrate was introduced into the chamber and then evacuated to 1 × 10 ⁻³ Pa or less. Thereafter, moisture in the chamber was removed by heat treatment at 300 ° C. for 10 minutes. Next, Ar ion bombardment for cleaning the substrate surface was performed using a DC power source or an AC power source under the following conditions.
Ar ion bombardment conditions Ar gas purity: 99.9%
Gas pressure: 1.0Pa
Tungsten filament current: When using 5 ADC power supply Power supply: Kyosan Seisakusho HPK03ZI
Bias voltage: -200 VAC when using power supply Power: Huttinger Tru-Plasma MF3010
Bias voltage: -200V

The intermediate layer was formed by a UBMS method using a Cr target with a purity of 99.9% and a C target with a purity of 99.9%. Argon gas is used as the process gas and acetylene gas as the hydrocarbon-based gas. When forming the carbon-free layer, only argon gas is used, and when forming the carbon-containing layer, a mixed gas of argon gas and acetylene gas is placed in the chamber. Introduced. The substrate temperature during film formation of the first layer and the second layer was 100 ° C., the total gas pressure was 1.0 Pa, and the substrate bias was constant at −200V.

First, a power of 2.0 kW was applied to the Cr target to discharge it, and a Cr layer as the first layer was formed. Next, the voltage applied to the Cr target was decreased, and at the same time, the voltage applied to the C target was increased to 2.0 kW. Furthermore, the Cr—C gradient composition layer as the second layer was formed by changing the flow ratio of argon gas and acetylene gas to control the ratio of Cr and carbon in the intermediate layer. The film thickness of the intermediate layer was adjusted by the film formation time.

As a comparative example, No. in Table 1 below. In No. 19, the composition gradient layer was not formed, and a compositional single layer of Cr and C having an atomic ratio of 1: 1 was formed as the second layer. No. 1 in Table 1 below. In No. 20, a tungsten target was used instead of the Cr target, and a W layer as a first layer and a WC gradient composition layer as a second layer were formed.

Next, a DLC layer was formed. As the DLC film, a DLC layer having a film thickness shown in Table 1 was formed by a CVD method or a UBMS method as a PVD method. In the CVD method, methane as a hydrocarbon gas is introduced into the chamber so that the total pressure becomes 2.0 Pa, 900 V is applied to the substrate holder from a pulsed DC power source manufactured by Kyosan Seisakusho, and the components of the hydrocarbon gas Was decomposed to form a DLC film. In the PVD method, specifically, the UBMS method, a power of 2.0 kW is applied to the carbon target, a mixed gas of methane and Ar is used as a process gas, the total pressure is 1.0 Pa, the negative bias voltage is 100 V, and the above DLC films having various film thicknesses shown in Table 1 were formed under the conditions of 5% methane and the balance Ar.

As described above, a sample in which the intermediate layer and the DLC layer were sequentially formed on the substrate was taken out of the chamber, and the following measurements and evaluations were performed.

Measurement of intermediate layer and DLC layer thickness
As a measurement sample, FIB (Focused Ion Beam) processing was performed so that a cross section in the film thickness direction of the sample could be observed, and a SEM (Scanning Electron Microscope) observation sample was created. Then, using this SEM observation sample, SEM observation was performed, and the film thickness of the intermediate layer, that is, the film thickness of the first layer and the second layer, and the film thickness of the DLC layer were measured from the obtained cross-sectional SEM image. .

Measurement of carbon ratio at interface of DLC layer in second layer The component composition of the gradient composition layer of the second layer was determined from the depth profile of the AES (Atomic Emission Spectroscopy) method. The carbon ratio at the interface of the DLC layer in the second layer was determined from the boundary with the DLC layer of the second layer. The carbon ratio was determined in terms of atomic% (t%) when Cr + C = 100 atomic% without considering impurities other than Cr and C.

Evaluation of Adhesion Adhesion was performed by a peel determination test shown in the standard VDI3198 of the German Engineers Association. Specifically, the C scale evaluation of the Rockwell test, that is, a diamond cone having a tip angle of 120 degrees was driven at a load of 150 kg. And the peeling | exfoliation condition of the film | membrane of an indenter implantation part was evaluated in six steps from HF1 with the highest adhesiveness to HF6 with the lowest adhesiveness in the said specification. In this example, HF1 and HF2 were evaluated as having good adhesion, and HF3 to HF6 were evaluated as having poor adhesion.

These results are also shown in Table 1.

Table 1 shows the following. No. 1 to 8 are configurations of the first layer and the second layer in the intermediate layer, the film thickness of the intermediate layer, the film formation method of the DLC layer, and the film thickness of the DLC layer, and the inclination of the second layer in the intermediate layer This is an example in which the composition is changed. Of these examples, no. In 1 and 2, the carbon ratio at the interface of the DLC layer of the second layer exceeded 80 atomic%, and thus the adhesion decreased. In these examples, it is considered that a portion having low hardness was formed in a region where the amount of C in the second layer was large, and peeling occurred from the portion having low hardness. In particular, no. 1 is an example in which the carbon concentration is increased from 0 atomic% on the substrate side to 100 atomic% on the DLC layer side, which is recommended in Patent Document 1 and Patent Document 2, but excellent adhesion is obtained in this example. There wasn't.

On the other hand, No. 7 and 8 are examples in which the carbon ratio at the DLC layer interface of the second layer is too small, in other words, the amount of Cr is too large. In this case, it is considered that the bond strength with the carbon constituting the DLC layer is weakened, the interface strength between the DLC and the second layer in the intermediate layer is weakened, and the adhesion is lowered.

No. in Table 1. Nos. 9 to 14 are the configurations of the first layer and the second layer in the intermediate layer, the gradient composition of the second layer in the intermediate layer, the film forming method of the DLC layer, and the film thickness of the DLC layer. This is an example in which only is changed. Of these examples, no. No. 9 was a gradient composition layer with a steep composition gradient because the intermediate layer was too thin, and good adhesion could not be obtained. This No. In No. 9, it is considered that cracks occurred starting from the steep gradient composition layer. On the other hand, no. No. 14, because the film thickness of the intermediate layer was too thick, good adhesion could not be obtained. This No. No. 14, it is considered that peeling occurred from the inside of the thick intermediate layer.

No. 15 to 18 are examples in which the thickness of the DLC layer is changed while the composition of the first layer and the second layer in the intermediate layer, the gradient composition of the second layer in the intermediate layer, and the thickness of the intermediate layer are made constant. is there. No. 15 shows the result of forming the DLC layer by the UBMS method which is a kind of PVD method. From these results, it was found that good adhesion can be obtained even when the film forming method and film thickness of the DLC layer are changed.

No. No. 19 is an example in which the second layer in the intermediate layer is not a gradient composition but a single composition of Cr—C. In this way, when the inclined structure was not formed in the intermediate layer, the adhesion was remarkably lowered. No. 20 is an example in which a laminated film is formed in the same manner as in the present invention except that tungsten is used instead of Cr. In this case, since the strength of the interface between tungsten and the substrate is insufficient, it is considered that the adhesiveness has decreased.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on January 9, 2015 (Japanese Patent Application No. 2015-003517), the contents of which are incorporated herein by reference.

The DLC layer laminate of the present invention is useful as various parts such as sliding members, molds, cutting tools, wear-resistant mechanical parts, magnetic / optical parts, and the like.

Claims

On the substrate, a diamond-like carbon layer is a laminate formed through an intermediate layer,
The intermediate layer includes a first layer provided on the base material and a second layer provided on the first layer,
The substrate is made of metal;
The first layer is made of Cr;
The second layer is made of Cr and carbon, has a composition gradient structure in which carbon increases from the substrate side toward the diamond-like carbon layer side and Cr decreases, and the diamond-like layer of the second layer A diamond-like carbon layer laminate, wherein the ratio of carbon to the total of Cr and carbon on the surface in contact with the carbon layer is 80 atomic% or less.
2. The diamond-like carbon layer laminate according to claim 1, wherein a ratio of carbon to a total of Cr and carbon on a surface in contact with the second diamond-like carbon layer is 40 atomic% or more and 80 atomic% or less.
The diamond-like carbon layer laminate according to claim 1 or 2, wherein the intermediate layer has a thickness of 0.05 µm or more and 1.0 µm or less.
A sliding member comprising the diamond-like carbon layer laminate according to claim 1.
The diamond-like carbon layer laminate manufacturing method according to claim 1, wherein the intermediate layer is formed by a PVD method, and the diamond-like carbon layer is formed by a PVD method or a CVD method. A method for producing a like carbon layer laminate.