Chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering and its preparation method

Abstract

The present invention provides a chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering and a preparation method thereof. The chromium nitride multi-layer nano-coating sequentially includes a chromium layer, a multi-layer structure coating, and a chromium nitride layer from bottom to top. The multi-layer structure coating is a multi-layer cyclic alternating layer of Cr<subgt;2< / subgt;N phase layer and CrN phase layer. This coating is obtained by using HiPIMS technology and regulating means such as changing the duty cycle and pulse structure of the discharge mode to regulate the plasma ionization rate, deposition rate, and stoichiometry of the film formation. The coating obtained by the technical solution of the present invention has high hardness, high toughness, good corrosion resistance, and oxidation resistance; applying this multi-layer coating to a tool helps to improve the hardness, corrosion resistance, and high-temperature oxidation resistance of the tool, and has good impact resistance, which can greatly improve the wear resistance of the substrate.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface protective coatings, and particularly relates to a chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering and a preparation method thereof. Background Art

[0002] The complex and harsh working environment of mechanical components poses requirements for the durability and long life of protective coatings. Currently, thick and ultra-thick hard coatings are used for mechanical components to obtain enhanced wear resistance, corrosion resistance, and irradiation resistance. High-quality thick or ultra-thick protective coatings can accommodate defects such as pinholes, grain boundaries, and cracks inside the thick layer, thereby avoiding penetration damage caused by joint defects and effectively improving the durability of the coatings. Generally, the preparation methods of thick coatings include electroplating, heat, plasma spraying, sol-gel method, cathodic arc deposition, chemical vapor deposition, magnetron sputtering deposition, etc. Due to the effects of coarsening grains, defect evolution, and stress on the performance during the coating growth process, the preparation of high-quality thick or ultra-thick protective coatings remains a challenge.

[0003] Chromium nitride (CrN) coatings have received increasing attention in the fields of cutting tools, dies, gears, etc. due to their high hardness, good wear resistance, and corrosion resistance. Although the hardness of multi-layer coatings is significantly improved due to their multi-layer structure design, their bonding strength in extreme environments is not as good as that of gradient coatings. This is because stress concentration occurs due to the huge hardness difference between each single layer, resulting in cracking and peeling between the layers. In experiments, in order to minimize the appearance of intermediate phases during the deposition process of the multi-layer structure and achieve the effect of blocking the growth of columnar crystals with the interface, it is often necessary to pause the target sputtering when switching layers, such as blocking the target surface with a shielding cover and then plating another layer after the residual reaction gas in the cavity is pumped out. Such a result not only reduces the film-forming efficiency but also poses high hardware requirements and precision for the equipment, greatly increasing the uncertainty, and thus it is difficult to be applied in actual industrial production. Summary of the Invention

[0004] Aiming at the above technical problems, the present invention discloses a chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering and a preparation method thereof. The obtained coating has properties such as high hardness, high chemical stability, high temperature resistance, low wear rate, impact toughness, and good corrosion resistance, which can better meet the requirements of modern cutting tools, and the preparation method is simple and easy to control.

[0005] For this, the technical solution adopted by the present invention is as follows:

[0006] A preparation method of a chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering, characterized in that: the chromium nitride multi-layer nano-coating sequentially includes a chromium layer, a multi-layer structure coating, and a surface barrier layer from bottom to top, and the multi-layer structure coating is a multi-layer cyclic alternating layer of Cr2N phase layers and CrN phase layers;

[0007] The chromium nitride multi-layer nano-coating is prepared by the following steps:

[0008] Step S1: Place the substrate in an argon environment, turn on the Cr target, and use HiPIMS (High power impulse magnetron sputtering) technology to activate the surface of the substrate.

[0009] Step S2: Adjust the argon flow rate and deposit a chromium layer on the surface of the substrate using HiPIMS technology.

[0010] Step S3: Introduce nitrogen, adjust the argon-nitrogen ratio of the gas to 2-3, and the gas pressure to 0.05-0.6 Pa. Deposit a Cr2N phase layer on the surface of the chromium layer using HiPIMS. The HiPIMS duty cycle is 5.5-6.5%, and the frequency is 150-400 Hz. Then, keep the gas pressure and the argon-nitrogen ratio unchanged, adjust the HiPIMS duty cycle to 1-2%, and the frequency to 600-1000 Hz, and deposit a CrN phase layer. Repeat the alternate deposition of the Cr2N phase layer and the CrN phase layer according to this step to obtain a multi-layer structure coating.

[0011] Step S4: Deposit a surface barrier layer on the surface of the multi-layer structure coating.

[0012] This technical solution uses HiPIMS technology. By means of regulating means such as changing the duty cycle and pulse structure of the discharge mode, the plasma ionization rate, deposition rate, and stoichiometry of the film formation are regulated to obtain a multi-layer coating. The obtained coating has the characteristics of high hardness, high toughness, good corrosion resistance, and oxidation resistance. When applied to tools, it can meet the performance requirements of modern tools such as high hardness, high chemical stability, high temperature resistance, low wear rate, impact toughness, and good corrosion resistance.

[0013] In addition, this preparation method significantly enhances the bombardment efficiency on the surface of the growing coating through high-density deposited ions. As the number of ion bombardments increases, the surface migration energy of the adsorbed atoms increases sharply, inhibiting the growth of transgranular fractures, resulting in grain refinement, increased density and smoothness, and increased hardness, toughness, and adhesion strength. This method solves typical problems in the deposition process, such as the formation of unwanted phases due to the switching of nitrogen gas flow. This method not only retains the effect of ion bombardment, but also has a simple process, gives full play to the advantages of HiPIMS, and is easy to industrialize.

[0014] As a further improvement of the present invention, the thickness of each Cr2N phase layer and CrN phase layer is 0.1-0.6 μm.

[0015] As a further improvement of the present invention, the Cr2N phase layer and the CrN phase layer have the same thickness.

[0016] As a further improvement of the present invention, the thickness of the chromium layer is 0.1 - 0.2 μm.

[0017] As a further improvement of the present invention, the thickness of the chromium nitride layer is 1 - 2 μm.

[0018] As a further improvement of the present invention, in step S1, before the activation treatment, the substrate is first subjected to glow cleaning. Further, the glow cleaning conditions are: vacuum degree 0.06 - 1 Pa, bias voltage -300 V - -1000 V, and time 20 - 60 min.

[0019] As a further improvement of the present invention, in step S1, the conditions of the activation treatment are: the duty cycle of HiPIMS is 40 - 90%, the frequency is 150 - 1000 Hz, the peak current of the target is 20 - 500 A, and the tool substrate is bombarded with high - energy Cr ions for 1 - 20 min.

[0020] As a further improvement of the present invention, in step S2, the air pressure is 0.05 - 0.8 Pa, the duty cycle of HiPIMS is 1 - 6.5%, and the frequency is 150 - 1000 Hz. Further preferably, in step S2, the air pressure is 0.2 - 0.8 Pa, the duty cycle of HiPIMS is 1 - 3%, and the frequency is 150 - 1000 Hz.

[0021] As a further improvement of the present invention, the distance between the substrate and the target surface is 60 mm - 150 mm, and the substrate is kept rotating in front of the target or rotating both around its own axis and around the furnace axis.

[0022] The present invention also discloses a chromium nitride multi - layer nano - coating based on pulsed magnetron sputtering, which is prepared by using the preparation method of the chromium nitride multi - layer nano - coating based on pulsed magnetron sputtering described in any one of the above.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] First, the chromium nitride multi - layer coating obtained by the technical solution of the present invention has high hardness, high toughness, good corrosion resistance and oxidation resistance; applying this multi - layer coating to the tool helps to improve the hardness, corrosion resistance and high - temperature oxidation resistance of the tool, and has good impact resistance, which can greatly improve the wear resistance of the substrate. When applying this multi - layer coating to plastic, resin or rubber molds, it can greatly improve the bonding strength between the coating and the flexible substrate, especially beneficial for resisting various corrosive substances precipitated during the processing of plastics and rubbers, thereby greatly improving the service life of the molds.

[0025] Second, the technical solution of the present invention adopts high-power pulsed magnetron sputtering technology. By utilizing its high plasma ionization rate, high energy is provided for the film-forming particles, and a ceramic-phase coating can be obtained at low temperature, effectively protecting the substrate from the loss of mechanical properties caused by high-temperature annealing, greatly improving the deposition efficiency of the ceramic coating, effectively improving the adhesion and quality of the film layer, and improving the production efficiency. By making full use of the adjustable characteristics of the plasma properties of high-power pulsed magnetron sputtering technology, by adjusting the duty cycle and frequency pulse width, the plasma properties are changed, and then the plasma ionization rate, deposition rate, and stoichiometry of the film formation are regulated to obtain a multi-layer coating. This method can effectively avoid the problem of generating impurity phases caused by adjusting the reaction gas, obtain a pure multi-layer film with clear interfaces; for the unwanted phases formed due to the switching of the nitrogen flow rate, this method retains the effect of ion bombardment, and the process is simple and easy to industrialize.

[0026] Third, the preparation method of the technical solution of the present invention has a simple process, is easy to industrialize, reduces environmental pollution, and is more environmentally friendly and green. Description of the Drawings

[0027] Figure 1 It is the XRD phase diagram of Example 1 and Comparative Example 1 of the present invention.

[0028] Figure 2 It is the edx elemental atomic ratio analysis diagram of Example 1 and Comparative Example 1 of the present invention.

[0029] Figure 3 It is the comparison result of the hardness and elastic modulus of Example 1 and Comparative Example 1 of the present invention; among them, (a) is the hardness and (b) is the elastic modulus.

[0030] Figure 4 It is the comparison photo of the coating cross-section electron micrographs prepared in Example 2 and Comparative Example 2 of the present invention; among them, (a) is Example 2 and (b) is Comparative Example 2.

[0031] Figure 5 It is the comparison result of the hardness and elastic modulus of Example 2 and Comparative Example 2 of the present invention; among them, (a) is the hardness and (b) is the elastic modulus.

[0032] Figure 6 It is the comparison result of the coating wear rates of Example 2 and Comparative Example 2 of the present invention.

[0033] Figure 7 It is the comparison of the coatings after the impact toughness test of Example 2 and Comparative Example 2 of the present invention, where (a) is Example 2 and (b) is Comparative Example 2.

[0034] Figure 8 It is the comparison of the coatings after the impact toughness test of Example 2 and Comparative Example 2 of the present invention, where (a) is Example 2 and (b) is Comparative Example 2.

[0035] Figure 9 It is the comparison result of the corrosion resistance performance between Example 2 and Comparative Example 2 of the present invention. Detailed implementation manners

[0036] The following further elaborates on the preferred embodiments of the present invention.

[0037] A chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering, the bottom layer is a pure chromium layer, followed by a multi-layer structure composed of Cr2N phase and CrN phase, and the top layer is a chromium nitride layer. The multi-layer structure includes a CrN phase layer with 50% - 58% Cr and 42 - 48% N, and a Cr2N phase layer with 58% - 72% Cr and 28% - 42% N, which are repeatedly arranged alternately.

[0038] The preparation method of this coating mainly is when depositing the coating on the surface of the workpiece by using high-power pulsed magnetron sputtering technology, introducing a certain proportion of argon and nitrogen, and realizing the transformation between Cr2N phase and CrN phase by adjusting the duty cycle of HiPIMS, thereby realizing the preparation of the multi-layer coating. Specifically, it includes:

[0039] First, place the clean substrate in an argon environment, 60mm - 150mm away from the target surface, and keep the substrate rotating in front of the target or rotating both around the furnace. By adjusting the argon flow rate, adjust the vacuum degree to 0.06 - 1Pa, and carry out glow cleaning for 20 - 60min under the bias voltage condition of -300V - -1000V; after the glow cleaning is completed, adjust the bias voltage to -50V - -300V, turn on the Cr target, apply HiPIMS to the target surface, with a duty cycle of 1 - 2%, a frequency of 150 - 1000Hz, adjust the peak current of the target material to 20 - 500A, and bombard the tool substrate with high-energy Cr ions for 1 - 20min to activate the surface of the tool substrate;

[0040] After the surface of the substrate is activated, adjust the argon flow rate, and adjust the air pressure to 0.05 - 0.8Pa. For HiPIMS, with a duty cycle of 1 - 3%, a frequency of 150 - 1000Hz, deposit a chromium bottom layer on the tool substrate, with a thickness of 0.1 - 0.2μm. The deposition time is adjusted accordingly according to the thickness.

[0041] After reaching the corresponding thickness, deposit the Cr2N phase layer. Specifically: open the nitrogen flowmeter, adjust the gas argon-nitrogen ratio to 2 - 3, and keep the air pressure at 0.05 - 0.6Pa. Adjust the HiPIMS duty cycle to 5.5 - 6.5%, preferably 6%, adjust the frequency to 150Hz - 400Hz, with a film layer thickness of 0.1 - 0.6μm, and deposit the Cr2N phase layer on the bottom layer by using HiPIMS.

[0042] After obtaining the Cr2N film with the corresponding thickness, deposit the CrN phase layer. Specifically: keep the gas pressure and the argon-nitrogen ratio unchanged, adjust the HiPIMS duty cycle to 1%-2%, preferably 1.5%, adjust the frequency to 600-1000 Hz, and deposit the CrN phase layer on the Cr2N phase layer by HiPIMS. The film thickness of the CrN phase layer is kept consistent with that of the Cr2N phase layer. The deposition time is adjusted accordingly according to the deposition rate.

[0043] After completion, repeat the alternating deposition of the Cr2N phase layer and the CrN phase layer, control the corresponding deposition time, and obtain a coating with a multi-layer structure.

[0044] Finally, deposit a 1-2 μm chromium nitride layer on the surface of the multi-layer structure coating as a barrier layer to resist impact, oxidation, and the infiltration of corrosive liquids.

[0045] The following is illustrated with specific examples.

[0046] Example 1

[0047] A chromium nitride multi-layer nano-coating is prepared by the following steps:

[0048] After the metal substrate is surface-cleaned, place it in front of the magnetron target, 80 mm away from the target surface, and make it rotate self in front of the target. Evacuate to the base vacuum of 1.0*10 -3 Pa, then fill in argon gas to make the vacuum reach 1 Pa, turn on the pulsed bias voltage, set the parameters as bias voltage -800 V, and the power supply parameters as 100 KHz / 8 μs for glow cleaning for 40 min. After the glow cleaning is completed, adjust the bias voltage to -300 V, keep other deposition parameters unchanged, turn on the Cr target, apply HiPIMS to the target surface, with a frequency of 800 Hz and a pulse width of 20 μs. At this time, the peak current of the target is 40 A, and bombard the tool substrate with high-energy Cr ions for 20 min to activate the surface of the tool substrate.

[0049] After the surface of the substrate is activated, adjust the argon gas flow rate and the air pressure to 0.3 Pa. Adjust the HiPIMS parameters, with a frequency of 200 Hz, a pulse width of 150 μs, and a duty cycle of 3%. Deposit a chromium underlayer on the tool substrate surface for 5 min, and the thickness of the obtained underlayer is about 200 nm.

[0050] Then introduce nitrogen gas to deposit the Cr2N phase layer; adjust the argon-nitrogen ratio of the gas to 2, and keep the air pressure at 0.4 Pa. Adjust the HiPIMS duty cycle to 6%, adjust the frequency to 100 Hz, and the pulse width to 300 μs, and the deposition duration is 10 min. The thickness of this Cr2N phase layer is about 300 nm.

[0051] Subsequently, a CrN layer was deposited while keeping the gas pressure and the argon-nitrogen ratio unchanged. The HiPIMS frequency was adjusted to 1000 Hz, the duty cycle was 1.5%, and the pulse width was 15 μs. The deposition time was also 10 min, and the thickness of the CrN layer was approximately 300 nm.

[0052] After completion, the Cr2N phase layer and the CrN phase layer were alternately deposited repeatedly, and the corresponding deposition time was controlled to obtain a coating with a multi-layer cyclic structure, with 4 cycles. After the deposition of the multi-layer structure was completed, a 2-μm-thick chromium nitride layer was deposited on the surface layer, and other deposition parameters remained unchanged.

[0053] Comparative Example 1

[0054] Based on Example 1, the deposition process in this comparative example remained unchanged, and only the power supply parameters for depositing the Cr2N layer were changed to 1000 Hz / 30 μs, the duty cycle was 3%, and other parameters remained unchanged.

[0055] The XRD phase diagrams of Example 1 and the control group are as Figure 1 shown, and the edx elemental atomic ratios are as Figure 2 shown. It can be seen from the figure that there is an obvious Cr2N phase in Example 1, and there is also a Cr2N phase in the control group, but the relative content is less. Through eds elemental analysis, it was found that the N / Cr atomic ratio in Example 1 was 0.76, while the element in the control group was 0.92. Combining the phase analysis, it can be clearly seen from the elemental atomic ratio that in the control group, due to the lower HiPIMS duty cycle and higher frequency of the Cr2N layer, the grown coating produced the CrN(111) phase, which in turn reduced the presence of the Cr2N phase, and the elemental ratio also approached 1. Such parameter settings could not meet the requirements of the layered structure, and thus the impact on performance also decreased.

[0056] Through the comparison between Example 1 and the comparative example, it can be seen that different power supply parameter settings result in different chemical compositions of the obtained coatings, resulting in different performances. The comparison results of the hardness and elastic modulus of the coatings in Example 1 and Comparative Example 1 are as Figure 3 shown, and it can be seen that Example 1 has higher hardness and elastic modulus.

[0057] Example 2

[0058] A chromium nitride multi-layer nano-coating was deposited on the tool surface, and the preparation method included the following:

[0059] The glow cleaning, surface activation, and underlayer were the same as in Example 1.

[0060] After depositing a chromium underlayer on the surface of the tool substrate, a Cr2N layer is deposited on the surface of the chromium underlayer by the high-energy pulsed magnetron method. Among them, nitrogen is introduced, and the argon-nitrogen ratio is adjusted to 2:1. Under the conditions of a vacuum degree of 0.4 Pa, a pulsed bias voltage of -80 V, and a duty cycle of 90%, where nitrogen and argon are fully mixed through a gas mixing cylinder before entering the cavity and then introduced into the chamber. The flow rate of argon is 120 sccm and the flow rate of nitrogen is 80 sccm. The Cr target is turned on, the target current is adjusted to 40 A, the duty cycle of the target power supply is 6%, and the frequency is 100 Hz. The deposition thickness is controlled to be 200 nm by adjusting the deposition time. The Cr2N layer contains 30% Cr and 70% N.

[0061] Then, a CrN layer is deposited on the surface of the tool substrate coated with Cr2N. Without changing the atmosphere, only the duty cycle of the target power supply is adjusted to 1.5% and the frequency is 1000 Hz. The corresponding deposition time is controlled to obtain a CrN layer with a thickness of 200 nm. The CrN layer contains 48% Cr and 52% N.

[0062] After the deposition of the CrN layer is completed, the deposition of Cr2N is continued by repeating the previous power supply parameters. Depositing a Cr2N layer and a CrN layer with equal thickness is recorded as one cycle period. The deposition is cycled 5 times on the surface of the tool substrate, and the top layer is a CrN layer. The thickness is controlled to be 1 μm by regulating the deposition time, that is, a nano-composite tool with multi-layer coatings and equal thickness for each layer is obtained.

[0063] The multi-layer coatings composed of Cr2N and CrN layers alternately in the above-mentioned Example 1 and Example 2 can be applied not only to tools but also to other metal parts or molds.

[0064] Comparative Example 2

[0065] On the basis of Example 1, the deposition process and other deposition parameters in this comparative example remain unchanged. Only when depositing the Cr2N layer, nitrogen is not filled, but only argon is introduced, and the air pressure is maintained at 0.4 Pa. This layer is a pure Cr metal phase layer, and a Cr / CrN multi-layer structure coating commonly used in industry is obtained.

[0066] The cross-sectional scanning photos of the coatings prepared in Example 2 and Comparative Example 2 are as Figure 4 shown. It can be seen that the coating interface in Example 2 is clear, the thickness is about 2 microns, the coating structure is dense and well combined with the substrate.

[0067] The hardness and elastic modulus of Example 2 and Comparative Example 2 are as Figure 5 shown. It can be seen that the hardness and elastic modulus of Example 2 are both superior to those of Comparative Example 2, indicating that the multi-layer coating composed of Cr2N and CrN layers alternately has higher hardness and elastic modulus than the Cr / CrN multi-layer structure coating of the prior art.

[0068] The following is a comparison of high-temperature oxidation performance, impact toughness, wear performance, corrosion resistance, etc. respectively. Wear performance: The wear test was carried out on the equipment MST-3001, using Al2O3 balls as the grinding balls, with a normal load of 2 N, 300 r / min, and a wear time of 60 min. After wear, the matrix of Comparative Example 2 was severely worn, with a wide and deep wear mark, and the wear mark depth reached 2.8 microns. In contrast, the wear mark on the worn surface of the coating in Example 2 did not reach the substrate, and the wear mark depth was only 0.8 microns. By calculating the wear rate, the comparison result of the wear rate between Example 2 and Comparative Example 2 is as Figure 4 shown. It can be seen that the coating in Example 2 can effectively improve the wear performance of the matrix compared with Comparative Example 2. The wear morphology is as Figure 8 shown.

[0069] High-temperature oxidation performance: The weights of the two coatings of Example 2 and Comparative Example 2 were measured respectively, and then placed in a muffle furnace for 1000 h at 600 °C. After that, the weights of the two coatings were measured again, and it was found that the weight gain of Example 2 was 0.032 mg / cm 2 , and the weight gain of Comparative Example 2 was 0.41 mg / cm 2 . It shows that the antioxidant performance of Example 2 is better than that of Comparative Example 2.

[0070] Impact toughness: For the two coatings, a Rockwell hardness tester was used to apply a force of 1472 N for 10 s with a diamond indenter, and the morphology of the indentation edge was observed with a microscope to judge the impact resistance of the coating. As shown in the figure, there are no obvious radial cracks at the indentation edge of Example 2, indicating that its bonding force with the matrix is better, and it can still maintain good bonding strength after plastic deformation. For Comparative Example 2, obvious radial crack propagation can be seen at the indentation edge, indicating that the bonding force between the coating and the matrix is poor under the condition of severe coating deformation, and the coating shows delamination phenomenon and the coating fails, as Figure 7 shown.

[0071] Corrosion resistance: The Tafel curve test of the sample was carried out using a Gamry electrochemical workstation, with an Ag-AgCl electrode as the reference electrode and a graphite electrode as the auxiliary electrode. The scanning range from negative potential to positive potential was -1 V to 1 V, the set scanning speed was 1 mV / s, and the electrolyte was 3.5 wt% NaCl solution.

[0072] Figure 9 is the Tafel curve of the sample in 3.5 wt% NaCl solution. The corrosion potential (Eorr) and corrosion current density (Icorr) can be used to judge the corrosion resistance of the sample. It can be obtained from the figure that the corrosion potential of Example 2 is -0.28 V, and the corrosion current density is 2.06×10-7 A / cm 2The corrosion potential of Comparative Example 2 was -0.63V, and the corrosion current density was 1.50×10-5A / cm2. After testing, the corrosion potential increased significantly, and the corrosion current density decreased by two orders of magnitude. The corrosion resistance of Example 2 in 3.5wt% NaCl solution was significantly better than that of Comparative Example 2.

[0073] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A preparation method of a chromium nitride multilayer nano-coating based on pulsed magnetron sputtering, characterized in that: The chromium nitride multi-layer nano-coating sequentially includes a chromium layer, a multi-layer structure coating, and a surface barrier layer from bottom to top. The multi-layer structure coating is a multi-layer cyclic alternating layer of Cr2N phase layers and CrN phase layers; The chromium nitride multi-layer nano-coating is prepared by the following steps: Step S1: Place the substrate in an argon environment, turn on the Cr target, and activate the surface of the substrate using HiPIMS technology; Step S2: Adjust the argon flow rate, and deposit a chromium layer on the surface of the substrate using HiPIMS technology; Step S3: Introduce nitrogen, and adjust the gas argon-nitrogen ratio to 2-3 and the gas pressure to 0.05-0.6 Pa. Deposit a Cr2N phase layer on the surface of the chromium layer using HiPIMS technology. The HiPIMS duty cycle is 5.5-6.5%, and the frequency is 150-400 Hz; then keep the gas pressure and the argon-nitrogen ratio unchanged, adjust the HiPIMS duty cycle to 1-2%, and the frequency to 600-1000 Hz, and deposit a CrN phase layer; repeat the alternate deposition of the Cr2N phase layer and the CrN phase layer according to this step to obtain a multi-layer structure coating; Step S4: Deposit a surface barrier layer on the surface of the multi-layer structure coating; The Cr2N phase layer contains 58%-72% by mass of Cr and 28%-42% by mass of N. The CrN phase layer contains 50%-58% by mass of Cr and 42%-48% by mass of N. The thickness of each Cr2N phase layer and CrN phase layer is not greater than 0.8 μm.

2. The preparation method of the chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering according to claim 1, characterized in that: In step S1, before the activation treatment, the substrate is first subjected to glow cleaning; the glow cleaning conditions are: vacuum degree 0.06-1 Pa, bias voltage -300 V to -1000 V, duty cycle 40-90%, and time 20-60 min.

3. The preparation method of the chromium nitride multilayer nano-coating based on pulsed magnetron sputtering according to claim 2, characterized in that: In step S1, the conditions of the activation treatment are: the duty cycle of HiPIMS is 1-2%, the frequency is 150-1000 Hz, the peak current of the target is 20-500 A, and the cutting tool substrate is bombarded with high-energy Cr ions for 1-20 min.

4. The preparation method of the chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering according to claim 2, characterized in that: In step S2, the gas pressure is 0.2-0.8 Pa, the HiPIMS duty cycle is 1-6.5%, and the frequency is 150-1000 Hz.

5. The preparation method of the chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering according to claim 1, characterized in that: The distance between the substrate and the target surface is 60 mm to 150 mm.

6. The preparation method of the chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering according to claim 1, characterized in that: The thickness of the chromium layer is 0.1-0.2 μm, and the thickness of each Cr2N phase layer and CrN phase layer is 0.1-0.6 μm.

7. The preparation method of the chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering according to claim 1, characterized in that: The thickness of each Cr2N phase layer and CrN phase layer is the same.

8. The preparation method of the chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering according to claim 1, characterized in that: The surface barrier layer is a chromium nitride layer, and the thickness of the chromium nitride layer is 1-2 μm.

9. A chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering, characterized in that: It is prepared by using the preparation method of the chromium nitride multi-layer nano-coating based on pulsed magnetron sputtering according to any one of claims 1-8.

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