CN110777341A - DLC/CNx/MeN/CNx nano multilayer film and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of film materials, and provides a DLC/CNx/Men/CNx nano multilayer film for solving the problems that the traditional DLC film has poor bonding strength with a substrate material and the wear resistance is reduced due to the fact that the bonding strength is improved by reducing stress, wherein the DLC/CNx/Men/CNx nano multilayer film comprises a substrate (1), a metal transition layer (2) and a nano multilayer film, wherein the metal transition layer and the nano multilayer film are sequentially deposited on the surface of the substrate, the nano multilayer film comprises a plurality of nano composite units (3), and the nano composite units sequentially comprise a DLC layer (4), a first gradient CNx layer (5), a metal nitride layer (6) and a second gradient CNx layer (7. The nano multilayer film effectively solves the problem of low film-substrate binding force of the traditional deposition method, reduces the internal stress and has excellent wear resistance; the preparation method has the advantages of simple steps, easily controlled process conditions, safe and pollution-free preparation process, low cost and easy realization of industrialization.

Description

A kind of DLC/CNx/MeN/CNx nano-multilayer film and preparation method thereof

technical field

The invention relates to the technical field of thin film materials, in particular to a DLC/CNx/MeN/CNx nano-multilayer film and a preparation method thereof.

Background technique

Diamond-like carbon (DLC) films have broad application prospects in mechanical parts, electronic devices, biomedicine and other fields due to their high hardness, good wear resistance and biocompatibility. At this stage, the preparation technologies of DLC films mainly include magnetron sputtering deposition, chemical vapor deposition, magnetic filtration cathode vacuum arc deposition, etc. However, DLC films have significant residual stress, which causes the film to easily fall off the substrate during loading.

The bonding strength between the DLC film and the matrix material is poor, and a large part of the reason is that the internal stress of the film is large due to the large difference between the thermal expansion coefficients of the two. At present, the methods for reducing the internal stress of DLC films mainly include doping method and nano-multilayer film technology. The doping method reduces the internal stress of the film by doping metal (Ti, Cr, Al) or non-metal elements in the DLC film, but some studies have shown that after doping the element, the hardness and elastic modulus of the DLC film are accompanied by stress. decrease and decrease, resulting in a decrease in the wear resistance of the film.

Nano-multilayer film is a thin film formed by alternate deposition of two or more materials. When the thickness of the monolayer film is larger, there is a higher internal stress inside it, which makes the film easier to peel off from the substrate. However, the multi-layer film structure can relieve the internal stress to a great extent. This is because when the number of interface layers of the multi-layer film is large, it can effectively absorb the stress and prevent the expansion of cracks, thereby effectively improving the bonding force between the film and the substrate. , and the thinner each layer results in a denser structure that further improves wear resistance.

"Metal carbide/diamond-like carbon (MeC/DLC) nano-multilayer film material and its preparation method" are disclosed in Chinese patent documents, and the application publication number is CN101081557A. The microhardness of the film prepared by this invention is high, reaching HV2000～ 4500, the friction coefficient is as low as 0.10 to 0.25, and the membrane-base bonding force is ≥60N. Yang Fanger et al. ("China Surface Engineering" 2018, 31(2): 66-74) found that the hardness of the multilayer film was higher than that of the single-layer film when they studied the preparation of DLC/CNx multilayer films by magnetron sputtering. Significant improvement, but the binding force is still low and needs further improvement.

SUMMARY OF THE INVENTION

In order to overcome the problems that the traditional DLC film has poor bonding strength with the base material, and reduces the stress and increases the bonding strength, the wear resistance will decrease. Abrasive DLC/CNx/MeN/CNx nano-multilayers.

The invention also provides a preparation method of the DLC/CNx/MeN/CNx nano-multilayer film, which has simple steps, easy control of process conditions, safe and pollution-free preparation process, low cost and easy industrialization.

In order to achieve the above object, the present invention adopts the following technical solutions:

A DLC/CNx/MeN/CNx nano-multilayer film, comprising a substrate, a metal transition layer and a nano-multilayer film sequentially deposited on the surface of the substrate, the nano-multilayer film is composed of several nano-composite units, and the nano-composite unit From bottom to top are the DLC layer, the first gradient CNx layer, the metal nitride layer and the second gradient CNx layer.

In the present invention, a pure metal transition layer is firstly deposited on the surface of the substrate, and then a DLC/CNx/MeN/CNx nano-multilayer film is deposited, and a suitable metal transition layer is applied between the substrate and the nano-multilayer film as an intermediate layer. Better, a chemical bonding interface can be formed between the metal transition layer and the diamond-like carbon film (DLC), which can alleviate the difference in thermal expansion coefficient between the matrix and the diamond-like carbon film, effectively reduce the internal stress, and improve the film-base bonding of the traditional deposition method. The problem of low force and excellent wear resistance. The lattices of metal nitrides and CNx coatings are easier to match, which can effectively improve the film-based bonding strength of DLC/CNx nanocoatings on commonly used high-speed steel substrates.

Preferably, the total thickness of the DLC/CNx/MeN/CNx nano-multilayer film is 0.6-10 μm.

Preferably, the substrate is a high-speed steel substrate.

Preferably, the metal transition layer is Ti or Cr. In the present invention, Cr and Ti metals are preferred as the transition layer because Cr, Ti have good affinity with carbon elements, and a chemical bonding interface can be formed between the transition layer and the diamond-like carbon film (DLC), which relieves the thermal expansion between the matrix and the diamond-like carbon film. The difference in coefficients can reduce the internal stress of the film and improve the bonding strength of the film base.

Preferably, the metal nitride layer is a TiN layer or a CrN layer.

Preferably, the nitrogen content of the first gradient CNx layer is gradually increased from 0 at. % to 18 at. %.

Preferably, the nitrogen content of the second gradient CNx layer is gradually decreased from 18 at. % to 0 at. %.

The design of the gradient layer with gradually increasing and decreasing N content makes it more mechanically compatible with the DLC layer and metal nitride layer, and enables a better transition to the beginning of the next cycle, the tendency of interlayer debonding is greatly reduced small, and at the same time, high hardness and interlayer bonding force can be obtained. The nitrogen content is controlled at 0-18 at.% because the nitrogen content of the CNx film significantly affects the hardness, elastic modulus and internal stress of the CNx film. Too high nitrogen content leads to excessive hardness and elastic modulus of the CNx film. Low, the performance matching between layers is difficult, and the multi-layer film cannot obtain excellent performance.

Preferably, the nano-indentation hardness of the DLC layer is 20-32 GPa; the nano-indentation hardness of the first gradient CNx layer and the second gradient CNx layer is 15-25 GPa; the nano-indentation hardness of the metal nitride layer The hardness is 20-28GPa.

Preferably, the thickness of the nano-multilayer film is 20-250 nm; the thickness of the nano-composite unit is 5-100 nm.

A preparation method of DLC/CNx/MeN/CNx nano-multilayer film, comprising the following steps:

(1) Pretreatment: the substrate is ultrasonically cleaned in acetone and anhydrous ethanol in turn and dried to remove oily impurities on the surface of the substrate and keep it clean and dry;

(2) Preparations: put the graphite target, metal target and pretreated substrate into the vacuum chamber of the vacuum coating machine, adjust the target-base distance, and pump the air pressure in the vacuum chamber to below 1.0×10 ^-3 Pa, and then pass the Argon gas with a purity of 99.99% keeps the deposition pressure at 0.6~1.2Pa, and the deposition temperature is 150~350℃; the metal target is a Ti target or a Cr target; the thickness of each film can be controlled by the deposition time;

(3) Deposition of metal transition layer: transfer the substrate to the top of the metal target, and form a metal transition layer on the surface of the substrate;

(4) Deposition of nano-multilayer films:

a) Transfer the substrate after the deposition of the metal transition layer to the top of the graphite target, adjust the argon flow rate to 30sccm, and coat the DLC layer; b) Pour N ₂ into the substrate, and place the substrate treated in step a) in a mixture of argon and N ₂ In the mixed atmosphere, the first gradient CNx layer is plated; the N ₂ flow is controlled to gradually increase from 0 to the set value;

c) transferring the substrate processed in step b) to the top of the metal target, and plating a metal nitride layer in a mixed atmosphere of argon and N ₂ ;

d) transferring the substrate processed in step c) to the top of the graphite target, and plating a second gradient CNx layer in a mixed atmosphere of argon and N ₂ ; and controlling the N ₂ flow rate to gradually transition from the set value to 0;

Steps a) to d) are repeated, and several cycles are alternated in this way to obtain a DLC/CNx/MeN/CNx nano-multilayer film.

The present invention adopts the deposition principle of the DC magnetron sputtering method as follows: under the action of the electric field, the plasma generated by the argon gas in the abnormal glow discharge bombards the surface of the cathode metal target or the graphite target, and the atoms on the surface of the target are bombarded. Sputtered out, and under the action of the electric field, it shoots toward the surface of the substrate in a certain direction to form a coating on the surface of the substrate.

Preferably, in step b), in the mixed atmosphere of argon and N ₂ , the set value of N ₂ flow rate is 1/2 of the argon gas flow rate.

Preferably, in step c): in the mixed atmosphere of argon and N ₂ , the mixing ratio of N ₂ and argon is 1:2.

Preferably, in step d), in the mixed atmosphere of argon and N ₂ , the set value of N ₂ flow rate is 1/2 of the argon gas flow rate.

Therefore, the present invention has the following beneficial effects:

(1) The DLC/CNx/MeN/CNx nano-multilayer film of the present invention effectively improves the problem of low bonding force of the film base of the traditional deposition method, reduces the internal stress, and has excellent wear resistance;

(2) The steps of the preparation method are simple, the process conditions are easy to control, the preparation process is safe and pollution-free, the cost is low, and it is easy to realize industrialization.

Description of drawings

FIG. 1 is a schematic structural diagram of the DLC/CNx/MeN/CNx nano-multilayer film of the present invention.

FIG. 2 is a graph showing the results of the bonding force test of the DLC/CNx/MeN/CNx nano-multilayer film prepared in Example 1. FIG.

3 is a friction and wear curve diagram of the DLC/CNx/MeN/CNx nano-multilayer film prepared in Example 1.

In FIG. 1 : substrate 1 , metal transition layer 2 , nanocomposite unit 3 , DLC layer 4 , first gradient CNx layer 5 , metal nitride layer 6 , second gradient CNx layer 7 .

Detailed ways

The technical solutions of the present invention will be further specifically described below through specific embodiments and in conjunction with the accompanying drawings.

In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following examples are conventional methods in the art unless otherwise specified.

As shown in Figure 1, a DLC/CNx/MeN/CNx nano-multilayer film includes a substrate 1, a metal transition layer 2 and a nano-multilayer film deposited on the surface of the substrate in turn, and the nano-multilayer film is composed of several nanocomposite units 3 The nanocomposite unit is composed of a DLC layer 4 , a first gradient CNx layer 5 , a metal nitride layer 6 and a second gradient CNx layer 7 in order from bottom to top.

Example 1

(1) Matrix pretreatment: put the high-speed steel matrix into acetone and anhydrous ethanol for ultrasonic cleaning for 20 minutes each to remove oil stains on the surface, dry it after cleaning, and install it on the sample stage;

(2) Experimental preparation: put the graphite target, metal target and pretreated high-speed steel substrate into the deposition chamber of the vacuum coating machine, adjust the distance between the target and the sample stage to 60mm, and pump the air pressure in the deposition chamber to After 1.0×10 ^-3 Pa, heat the high-speed steel to stabilize the temperature at 200℃;

(3) Deposition of Cr metal transition layer: Pour high-purity argon gas into the deposition chamber, control the flow of argon gas to stabilize the pressure in the vacuum chamber at 0.8Pa, select Cr as the metal transition layer, and adjust the power of the pure metal Cr target to 80W , plus a negative bias voltage of 200V, a pure metal Cr layer was deposited on the rotating sample stage, and the deposition time was 7.5min;

(4) Preparation of DLC/CNx/CrN/CNx nano-multilayer film:

a) Pour high-purity argon gas into the deposition chamber, stabilize the pressure in the chamber at 0.8Pa, and deposit a DLC layer on the Cr transition layer with a graphite target sputtering power of 60W and a negative bias voltage of 100V for 36min;

b) deposit a first gradient CNx layer on the DLC layer with a graphite target sputtering power of 55W and a negative bias voltage of 100V, gradually introduce high-purity nitrogen, and control the flow rate to increase from 0 sccm to 15 sccm within 31 min;

c) Deposit a CrN layer on the CNx layer with a metal target sputtering power of 80W and a negative bias voltage of 200V, and the deposition time is 1.5min;

d) A second gradient CNx layer was deposited on the CrN layer with a graphite target sputtering power of 55W and a negative bias voltage of 100V, and the flow rate of high-purity nitrogen was controlled to decrease uniformly from 15sccm to 0sccm within 31min. Then start the next cycle of deposition, the number of cycles of the multi-layer film is controlled at 10 cycles, and the film thickness of the multi-layer film is about 1.2 μm.

After the above steps, the DLC/CNx/CrN/CNx nano-multilayer film deposited on the high-speed steel substrate is finally obtained. The bonding force test results are shown in Figure 2. It can be seen that when the load reaches 61N, a strong acoustic emission signal begins to appear, indicating that the multi-layer film is damaged at this time, and the bonding force of the multi-layer film is 61N. The friction factor curve is shown in Figure 3. It can be seen that the friction factor is relatively stable. The average friction factor of the multilayer film is 0.118 by averaging the instantaneous friction factors in the entire time period.

Example 2

(1) Matrix pretreatment: same as Example 1;

(2) Experimental preparation: the same as in Example 1;

(3) Deposition of Ti transition layer: Pour high-purity argon into the deposition chamber, control the flow of argon to stabilize the pressure in the vacuum chamber at 0.8Pa; adjust the power of the pure metal Ti target to 80W, plus a negative bias of 200V , deposit a pure metal Ti layer on the rotating sample stage, and the deposition time is 10min;

(4) Preparation of DLC/CNx/TiN/CNx nano-multilayer film:

a) Pour high-purity argon gas into the deposition chamber, stabilize the pressure in the chamber at 0.8Pa, and deposit a DLC layer on the Ti transition layer with a graphite target sputtering power of 60W and a negative bias voltage of 100V for 36min;

c) deposit a first gradient CNx layer on the DLC layer with a graphite target sputtering power of 55W and a negative bias voltage of 100V, gradually feed high-purity nitrogen, and control the flow rate to increase from 0 sccm to 15 sccm within 31 min;

d) A TiN layer was deposited on the high-speed steel substrate with a sputtering power of 80W metal Ti target and a negative bias voltage of 200V for 2 minutes. A second gradient CNx layer was deposited on the TiN layer with a graphite target sputtering power of 55W and a negative bias voltage of 100V; the flow rate of high-purity nitrogen was controlled to decrease from 15sccm to 0sccm uniformly within 31min. The number of cycles of the multilayer film is controlled at 10 cycles, and the thickness of the multilayer film is about 1.2 μm.

After the above steps, the DLC/CNx/TiN/CNx nano-multilayer film deposited on the high-speed steel substrate is finally obtained.

Comparative Example 1 (without the first gradient CNx layer)

The difference between Comparative Example 1 and Example 1 is: step (4) is the preparation of DLC/CrN/CNx nano-multilayer film:

Pour high-purity argon gas into the deposition chamber, and stabilize the chamber pressure at 0.8Pa; use a graphite target sputtering power of 60W and a negative bias voltage of 100V to deposit a DLC layer on the Cr transition layer for 36 minutes. A metal nitride layer was deposited on the DLC with a metal Cr target sputtering power of 80W and a negative bias voltage of 200V for 2 minutes. Then, a graphite target sputtering power of 55W and a negative bias voltage of 100V were used to deposit a gradient second gradient CNx layer on the metal layer; the flow rate of high-purity nitrogen was controlled to decrease uniformly from 15sccm to 0sccm within 31min. The number of cycles of the multilayer film is controlled at 10 cycles, and the thickness of the multilayer film is about 950nm;

The remaining steps and process conditions are exactly the same.

Comparative example 2 (single CNx layer and no gradient)

The difference between Comparative Example 1 and Example 1 is: Step (4) Preparation of DLC/CrN/CNx nano-multilayer film: Pour high-purity argon gas into the deposition chamber, and stabilize the chamber pressure at 0.8Pa. A DLC layer was deposited on the Cr transition layer with a graphite target sputtering power of 60W and a negative bias voltage of 100V for 36 minutes. A metal nitride layer was deposited on the DLC layer with a metal Cr target sputtering power of 80W and a negative bias voltage of 200V for 1 min. A CNx layer was deposited on the metal layer by using a graphite target sputtering power of 55W, a negative bias voltage of 100V, and a nitrogen flow rate of 15sccm. The number of cycles of the multilayer film is controlled at 10 cycles, and the thickness of the multilayer film is about 950 nm; the rest of the process conditions are exactly the same.

Comparative example 3 (without metal transition layer)

The difference between Comparative Example 3 and Example 1 is that there is no step (3), and the remaining steps and process conditions are exactly the same.

Comparative example 4 (two CNx layers and no gradient)

The difference between Comparative Example 4 and Example 1 is that in step (4), the nitrogen flow rate in b) and d) is maintained at 15 sccm, and the remaining steps and process conditions are exactly the same.

The films prepared in Examples 1, 2 and Comparative Examples 1-4 were tested by the following test methods:

The bonding strength of the film was measured using the WS-2005 coating adhesion scratch tester. Test conditions: loading rate 100N/min, scratch length 4mm, scratch rate 4mm/min.

The hardness of the films was measured with a Nano Indenter G200 nanoindenter, using the continuous stiffness method.

WTM-1E ball-disk friction and wear testing machine tests the friction coefficient of the film, the smaller the friction coefficient, the higher the wear resistance. Test conditions: ball-disk friction pair, Si ₃ N ₄ ball, diameter 3mm, normal load 0.5N, relative sliding velocity 0.11m/s, test duration 10min.

The results are shown in Table 1:

Table 1. Test Results

It can be seen from Table 1 that the DLC/CNx/MeN/CNx nano-multilayer film of the present invention has high film-base bonding force, hardness and excellent wear resistance. By comparing the data of Comparative Example 1 and Example 1, it can be seen that the absence of the first gradient CNx layer leads to a decrease in bonding force and hardness, because the mechanical compatibility of the DLC layer with the first gradient CNx layer is better than that of the DLC layer and CrN The direct contact of the layers, the existence of the first gradient CNx layer, reduces the internal stress and at the same time enhances the interfacial strengthening effect; by comparing the data of Comparative Example 2 and Example 1, it can be seen that only one CNx layer without concentration gradient will lead to hardness and the sudden decrease of the binding force, because the design of the gradient CNx layer can reduce the large difference in mechanical properties between DLC and CrN, and the hardness of the non-concentration gradient CNx layer is lower than that of the gradient CNx layer; It can be seen from the data of Example 3 and Example 1 that without the metal transition layer, the bonding force of the film base will be significantly reduced, and the tribological properties will also be affected; by comparing the data of Comparative Example 4 and Example 1, it can be seen that the gradient of the CNx layer Design is critical, as nanomultilayers with only a fixed nitrogen content, without gradient design, lead to a significant drop in binding force and stiffness.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. There are other variations and modifications under the premise of not exceeding the technical solutions described in the claims.

Claims (10)

1. a DLC/CNx/MeN/CNx nano-multilayer film, is characterized in that, comprises matrix (1), the metal transition layer (2) and the nanometer multilayer film deposited on the matrix surface successively, described nanometer multilayer film It is composed of several nanocomposite units (3), the nanocomposite units are, from bottom to top, a DLC layer (4), a first gradient CNx layer (5), a metal nitride layer (6) and a second gradient CNx layer (7) ). 2 . The DLC/CNx/MeN/CNx nano-multilayer film according to claim 1 , wherein the total thickness of the DLC/CNx/MeN/CNx nano-multilayer film is 0.6-10 μm. 3 . 3 . The DLC/CNx/MeN/CNx nano-multilayer film according to claim 1 , wherein the substrate is a high-speed steel substrate. 4 . 4. The DLC/CNx/MeN/CNx nano-multilayer film according to claim 1, wherein the metal transition layer is Ti or Cr; and the metal nitride layer is a TiN layer or a CrN layer. 5 . The DLC/CNx/MeN/CNx nano-multilayer film according to claim 1 , wherein the nitrogen content of the first gradient CNx layer is gradually increased from 0 at.% to 18 at.%. 6 . 6 . The DLC/CNx/MeN/CNx nano-multilayer film according to claim 1 , wherein the nitrogen content of the second gradient CNx layer gradually decreases from 18 at.% to 0 at.%. 7 . 7. A DLC/CNx/MeN/CNx nano-multilayer film according to claim 1, wherein the nano-indentation hardness of the DLC layer is 20-32 GPa; the first gradient CNx layer and the first gradient CNx layer are The nano-indentation hardness of the two-gradient CNx layer is 15-25 GPa; the nano-indentation hardness of the metal nitride layer is 20-28 GPa. 8 . The DLC/CNx/MeN/CNx nano-multilayer film according to claim 1 , wherein the thickness of the nano-multilayer film is 20-250 nm; the thickness of the nano-composite unit is 5-250 nm. 9 . 100nm. 9. a preparation method of DLC/CNx/MeN/CNx nano-multilayer film as described in any one of claim 1-8, is characterized in that, comprises the following steps: (1) Pretreatment: the substrate is ultrasonically cleaned in acetone solution and anhydrous ethanol in turn and dried to remove oily impurities on the surface of the substrate and keep it clean and dry; (2) Preparation work: put the graphite target, metal target and pretreated substrate into the vacuum chamber of the vacuum coating machine, adjust the target-base distance, and pump the air pressure in the vacuum chamber to below 1.0×10 ^-3 Pa, and then pass the Argon gas with a purity of 99.99% keeps the deposition pressure at 0.6-1.2Pa, and the deposition temperature is 150-350°C; the metal target is a Ti target or a Cr target; (3) Deposition of metal transition layer: transfer the substrate to the top of the metal target, and form a metal transition layer on the surface of the substrate; (4) Deposition of nano-multilayer films: a) Transfer the substrate on which the metal transition layer deposition is completed to the top of the graphite target, adjust the argon flow rate to 30sccm, and coat the DLC layer; b) feeding N ₂ into the substrate treated in step a) in a mixed atmosphere of argon and N ₂ to form a first gradient CNx layer; controlling the flow of N ₂ to gradually increase from 0 to a set value; c) transferring the substrate processed in step b) to the top of the metal target, and plating a metal nitride layer in a mixed atmosphere of argon and N ₂ ; d) transferring the substrate processed in step c) to the top of the graphite target, and plating the second gradient CNx layer in a mixed atmosphere of argon gas and N ₂ ; and controlling the N ₂ flow rate to gradually transition from the set value to 0; Steps a) to d) are repeated to obtain a DLC/CNx/MeN/CNx nano-multilayer film. 10. the preparation method of DLC/CNx/MeN/CNx nano-multilayer film according to claim 9, is characterized in that, In step b), in the mixed atmosphere of argon gas and N ₂ , the set value of N ₂ flow rate is 1/2 of the argon gas flow rate; In step c): in the mixed atmosphere of argon and N , the mixing ratio of N and argon is ₁ : ₂ ; In step d), in the mixed atmosphere of argon and N ₂ , the set value of N ₂ flow rate is 1/2 of the argon gas flow rate.

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