Ultra-long-life high-entropy nitride coating turning tool for precision machining and preparation method

Abstract

The invention relates to an ultra-long-life high-entropy nitride coating turning tool for precision machining and a preparation method, and the high-entropy nitride coating turning tool comprises a turning tool body and a multi-layer gradient coating attached to the surface of the turning tool body. The multi-layer gradient coating sequentially comprises a Cr base layer, a CrN transition layer and an AlTiNbCrN working layer from inside to outside. The Cr base layer is used for improving the adhesive force of a subsequent coating and a hard alloy matrix; the CrN transition layer is used for relieving lattice mismatch and stress mutation between the base layer and the working layer; the AlTiNbCrN working layer serves as a main functional layer and provides ultrahigh hardness, wear resistance and oxidation resistance. And the atomic ratio of Al to Ti to Nb to Cr in the AlTiNbCrN working layer is 1: 1: 1: 1. The high-entropy nitride coating turning tool has the advantages of being long in service life and stable in performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal cutting tool, in particular to a super-long-life high-entropy nitride coating tool for precision machining and a preparation method thereof. BACKGROUND

[0002] Numerical control machine tool is the core equipment to realize high-precision and high-efficiency machining, and its machining performance depends on the numerical control tool used to a great extent. In the cutting process, the tool directly acts on the workpiece and bears great mechanical stress, friction and high temperature. Therefore, the service life and machining precision of the tool are mainly restricted by the key performances of the surface coating, such as wear resistance, red hardness, thermal stability and oxidation resistance.

[0003] Among them, the multi-element nitride coating represented by TiN and TiAlN is the most widely used, which effectively prolongs the basic life of the tool by providing high hardness and certain thermal stability. However, with the increasing demand for machining efficiency, difficult-to-machine material application and extreme working conditions such as high-speed dry cutting in the field of advanced manufacturing, the traditional coating system gradually exposes its limitations. Especially in long-term high-temperature environment, the problems such as thermal softening, oxidation and microstructure degradation of the coating will cause its wear resistance to decrease significantly, and then cause the tool to wear rapidly and the machining precision to deteriorate, ultimately limiting the overall machining efficiency and cost control.

[0004] To break through the performance bottleneck of traditional coating materials, high-entropy nitride coating as a new material system has attracted widespread attention. This kind of coating is composed of five or more than five main elements in the form of approximate equal atomic ratio. Its unique high-entropy effect, lattice distortion, delayed diffusion and cocktail effect make it easy to form a simple solid solution phase, and in theory, it shows comprehensive performance far beyond traditional coatings, especially excellent high-temperature stability, toughness and oxidation resistance.

[0005] Although high-entropy nitride coating shows great potential in the field of material research, how to convert this theoretical advantage into an industrial coating product that can be applied to numerical control tools with stable performance and repeatable preparation still faces a series of key technical challenges to be solved. These mainly include: multi-element component optimization design for extreme working conditions; precise control of microstructure during coating growth; ensuring high strength and toughness of the interface between the coating and the hard alloy substrate; and developing stable, controllable and suitable for complex tool shape large-scale deposition process. Solving these problems is the only way to realize the practicality of high-performance, super-long-life high-entropy nitride coating tools. SUMMARY

[0006] Therefore, it is necessary to provide a long-life high-entropy nitride coating turning tool for precision machining and a preparation method thereof to solve the problems of short service life and unstable performance of traditional coating tools.

[0007] In a first aspect, the present application provides a long-life high-entropy nitride coating turning tool for precision machining, comprising a turning tool body and a multi-layer gradient coating attached to the surface of the turning tool body. The multi-layer gradient coating comprises, from inside to outside, a Cr base layer, a CrN transition layer and an AlTiNbCrN working layer. The atomic ratio of Al, Ti, Nb and Cr in the AlTiNbCrN working layer is 1:1:1:1.

[0008] In a second aspect, the present application further provides a preparation method of a long-life high-entropy nitride coating turning tool for precision machining, which is used to prepare the long-life high-entropy nitride coating turning tool for precision machining. S1: cleaning and drying Al block, Ti block, Nb block and Cr block raw materials; S2: preparing AlTiNbCr high-entropy alloy target material by vacuum arc furnace smelting; S3: fixing the turning tool body on the magnetron sputtering turntable, aligning the tool tip with the target source, installing AlTiNbCr high-entropy target material at the radio frequency target site, and installing pure Cr target material at the direct current target site; S4: vacuumizing until the pressure is below 2.5E -5 Pa; S5: setting the substrate temperature to 450℃, and using argon to glow clean the target material and the turning tool body during the temperature rising process; S6: after the substrate temperature reaches 450℃, using pure Cr target material to perform base layer sputtering on the turning tool body; S7: after the base layer sputtering is completed, adjusting Ar:N2=7:1, and using pure Cr target material to perform transition layer sputtering on the basis of the Cr base layer; S8: after the transition layer sputtering is completed, using AlTiNbCr high-entropy target material to perform working layer sputtering, and obtaining the target turning tool after the layer sputtering is completed, and keeping the working pressure less than 1Pa.

[0009] In one of the embodiments, step S2 specifically comprises the following steps: S21: smelting Al block and Ti block in a first smelting tank to obtain AlTi intermediate alloy; S22: smelting Nb block and Cr block in a second smelting tank to obtain NbCr intermediate alloy; S23: placing the AlTi intermediate alloy and the NbCr intermediate alloy in a third smelting tank, repeatedly smelting by electric arc for more than 20 times, and obtaining AlTiNbCr high-entropy alloy ingot after cooling. S24: cutting the AlTiNbCr high-entropy alloy ingot into an AlTiNbCr high-entropy alloy target material of a target size by using a wire cutting method.

[0010] In one of the embodiments, in step S1, the purity of the Al block, the Ti block, the Nb block and the Cr block raw materials is greater than or equal to 99.99%, and the raw materials are sequentially cleaned using acetone, alcohol and deionized water. In step S2, the vacuum degree of the vacuum arc furnace is 0.001-0.1 Pa.

[0011] In one of the embodiments, in step S5, the parameters of the glow cleaning are direct current power 20 W, bias voltage 400 V, argon flow rate 20 sccm / min, and cleaning time 20 min.

[0012] In one of the embodiments, in step S6, the sputtering parameters of the base layer are as follows: the power of the pure Cr target material is increased from 20 W to 200 W in 6 min, the power increasing rate is 30 W / min, the bias voltage is decreased from 400 V to 200 V in 5 min, the bias voltage decreasing rate is 40 V / min, the argon flow rate is set to 20 sccm / min, and the sputtering time is 10 min.

[0013] In one of the embodiments, in step S7, the sputtering parameters of the transition layer are as follows: the power of the pure Cr target material is 200 W, the bias voltage is 200 V, and the sputtering time is 20 min.

[0014] In one of the embodiments, in step S8, the sputtering parameters of the working layer are as follows: the power of the AlTiNbCr high-entropy alloy target material is 200 W, the bias voltage is 200 V, and the sputtering time is 240 min.

[0015] In one of the embodiments, the target size of the AlTiNbCr high-entropy alloy target material is 50 mm in diameter and 4 mm in thickness.

[0016] The beneficial effects of the present application are as follows: (1) The high-entropy nitride coated turning tool adopts AlTiNbCrN high-entropy nitride as the working layer in an equimolar ratio, the AlTiNbCrN high-entropy nitride forms a stable single-phase FCC structure through high-entropy effect, has high nano-hardness, far exceeds traditional TiN and TiAlN coatings, and the synergistic effect of Al and Nb in the working layer significantly enhances the high-temperature oxidation resistance and corrosion resistance of the coating; Ti and Cr provide high hardness and good toughness. The cocktail effect of multiple components makes the AlTiNbCrN coating achieve an excellent balance between hardness, toughness and thermal stability, which can significantly enhance the service life and performance stability of the tool.

[0017] (2) The present application is attached to the tool body on the multi-layer gradient coating, the multi-layer gradient coating includes Cr base layer, CrN transition layer and AlTiNbCrN working layer from inside to outside in turn, the Cr base layer is used for improving the adhesion of the subsequent coating and the hard alloy substrate;The CrN transition layer is used for relieving the lattice mismatch and stress mutation between the base layer and the working layer;AlTiNbCrN working layer as the main functional layer, provides super high hardness, wear resistance and oxidation resistance;The multi-layer gradient coating is gradually transitioned through the composition and lattice, effectively relieves the interface stress concentration caused by the mismatch of the thermal expansion coefficient and the lattice difference, realizes the ordered release of internal stress, and increases the bonding force of the multi-layer gradient coating and the tool body; (3) The present application can obtain high-quality coating with small grain size, dense structure and low defect density by controlling the specific base vacuum degree, deposition temperature range, and combining the substrate bias and power to cooperatively control the deposition rate. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The mounting schematic diagram of the tool body provided by the embodiment of the present application in the magnetron sputtering vacuum cavity is shown; Figure 2 The surface SEM diagram of the high-entropy nitride coating hard alloy piece provided by the embodiment of the present application is shown; Figure 3 The wear scar morphology diagram obtained by reciprocating friction of the high-entropy nitride coating hard alloy piece and the SiC ball is shown; Figure 4 The tool tip micro-morphology comparison diagram of the high-entropy nitride coating tool and the uncoated tool under the same working condition turning SK4 bar until the two tools reach the effective service life is shown; Figure 5 The wear band width diagram of the high-entropy nitride coating tool after continuously turning SK4 bar for 37h is shown; Figure 6 The surface roughness comprehensive comparison diagram of the uncoated tool after continuously turning SK4 bar for 13h, and one sample is obtained every hour is shown; Figure 7 The surface roughness comprehensive comparison diagram of the high-entropy nitride coating tool after continuously turning SK4 bar for 37h, and one sample is obtained every hour is shown; Figure 8 The SEM cross-section morphology comparison diagram of the high-entropy nitride coating and the TiN coating is shown; Figure 9 The micro-morphology diagram of the TiN coating tool turning SK4 bar for 10h and 20h is shown; Figure 10A TiN-coated turning tool provided by the embodiment of the present application is used to collect the surface roughness of the turning sample at each hour as a node, and a comparison chart is provided. Figure 11 A comparison chart of the SEM cross-sectional morphology of the high-entropy nitride coating and the TiAlN coating provided by the embodiment of the present application is provided. Figure 12 A micro-morphology chart of the TiAlN-coated turning tool provided by the embodiment of the present application after turning the SK4 bar for 10 hours and 20 hours is provided. Figure 13 A comparison chart of the surface roughness of the turning sample collected by the TiAlN-coated turning tool provided by the embodiment of the present application at each hour as a node is provided. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] In one embodiment, an ultra-long-life high-entropy nitride coating turning tool for precision machining includes a turning tool body and a multi-layer gradient coating attached to the surface of the turning tool body. The multi-layer gradient coating includes, from inside to outside, a Cr primer layer, a CrN transition layer and an AlTiNbCrN working layer; the atomic ratio of Al, Ti, Nb and Cr in the AlTiNbCrN working layer is 1:1:1:1.

[0021] AlTiNbCrN uses a specific equimolar ratio combination of Al, Ti, Nb and Cr four elements to stabilize a single face-centered cubic (FCC) solid solution structure through high-entropy effect, avoiding the generation of brittle intermetallic compounds. The synergistic effect of Al and Nb significantly enhances the high-temperature oxidation resistance and corrosion resistance of the coating; Ti and Cr provide high hardness and good toughness. This multi-component cocktail effect makes the AlTiNbCrN working layer achieve an excellent balance between hardness, toughness and thermal stability, which can significantly enhance the service life and performance stability of the tool.

[0022] The multi-layer gradient coating includes, from inside to outside, a Cr primer layer, a CrN transition layer and an AlTiNbCrN working layer, the Cr primer layer is used to improve the adhesion of the subsequent coating to the hard alloy substrate; the CrN transition layer is used to relieve the lattice mismatch and stress mutation between the primer layer and the working layer; the AlTiNbCrN working layer serves as the main functional layer, providing ultra-high hardness, wear resistance and oxidation resistance; through the gradual change of composition and structure, the internal stress is effectively released, and the bonding force of the multi-layer gradient coating to the tool body is increased.

[0023] In one embodiment, a method for preparing a precision machining ultra-long life high-entropy nitride coated turning tool, used to prepare the precision machining ultra-long life high-entropy nitride coated turning tool of the above embodiment, includes the following steps: S1: Clean and dry the raw materials, including Al blocks, Ti blocks, Nb blocks, and Cr blocks.

[0024] Specifically, in step S1, the purity of the raw materials Al, Ti, Nb and Cr blocks is greater than or equal to 99.99%. The raw materials are washed sequentially with acetone, alcohol and deionized water, and then dried for later use.

[0025] S2: AlTiNbCr high-entropy alloy targets were prepared by vacuum arc furnace melting, with a vacuum degree of 0.001-0.1 Pa.

[0026] S3: Fix the cutting tool body on the turntable inside the magnetron sputtering vacuum chamber, align the tool tip with the target source, install the AlTiNbCr high-entropy target at the RF target position, and install the pure Cr target at the DC target position.

[0027] Specifically, such as Figure 1 As shown, in this embodiment, a special fixture is used to align the tool tip with the target source at 45°, and with the rotation, priority and uniform deposition can be achieved on the key cutting edge area of ​​the tool. While ensuring the coating performance, production efficiency and batch stability can be improved.

[0028] In addition, in order to observe the microstructure and friction coefficient of the AlTiNbCrN high-entropy nitride alloy coating, a polished hard alloy sheet was placed in the magnetron sputtering vacuum chamber, and a multilayer gradient coating was sputtered on its surface simultaneously.

[0029] S4: Evacuate to 2.5E -5 Below Pa. During the vacuuming process, when the mechanical pump evacuates to a vacuum level of 3.0E... 0 At Pa, turn on the molecular pump and continue evacuating until the vacuum level in the vacuum chamber reaches 2.5E. -5 Below Pa; S5: Set the substrate temperature to 450℃, and use argon gas to perform glow discharge cleaning on the target and the cutting tool body during the heating process.

[0030] Glow discharge cleaning is performed during the heating process to remove dirt and oxides from the target surface. Specifically, the parameters for glow discharge cleaning are: DC power 20W, bias voltage 400V, argon flow rate 20 sccm / min, and cleaning time 20 min.

[0031] S6: After the substrate temperature reaches 450℃, use a pure Cr sputtering target to perform a bottom layer sputtering on the cutting tool body.

[0032] Specifically, the sputtering parameters for the bottom layer are as follows: the power of the pure Cr target increases from 20W to 200W within 6 minutes at a rate of 30W / min; the bias voltage decreases from 400V to 200V within 5 minutes at a rate of 40V / min; the argon flow rate is set to 20 sccm / min; and the sputtering time is 10 min.

[0033] S7: After the base layer sputtering is completed, adjust Ar:N2=7:1 and use pure Cr target material to perform transition layer sputtering on the Cr base layer.

[0034] Specifically, the sputtering parameters for the transition layer are: pure Cr target power 200W, bias voltage 200V, and sputtering time 20min.

[0035] S8: After the transition layer sputtering is completed, the working layer is sputtered using an AlTiNbCr high-entropy target. After the working layer sputtering is completed, the target cutting tool is obtained, and the working gas pressure is kept less than 1 Pa.

[0036] Specifically, the sputtering parameters for the working layer are: AlTiNbCr high-entropy alloy target power 200W, bias voltage 200V, and sputtering time 240min.

[0037] like Figure 2 As shown, the AlTiNbCrN high-entropy nitride alloy coating exhibits uniform grain size, is flat and free of clusters, and has a dense coating. Figure 3 As shown, the coefficient of friction of the high-entropy nitride coated cemented carbide sheet is stable at 0.6.

[0038] In this embodiment, the multilayer gradient coating is sputtered with a magnetron sputtering vacuum level controlled to be less than 2.5E. -5 Pa, at this vacuum level, contamination from impurity gases can be minimized. Furthermore, in this embodiment, the sputtering temperature is controlled at 450℃. This temperature ensures good crystallinity and density of the coating while avoiding damage to the toughness of the cemented carbide substrate. Moreover, the deposition rate can be controlled by adjusting the target power and gas pressure during the sputtering process; in this embodiment, it is specifically controlled at 0.5-1.5 μm / h. This deposition rate ensures dense coating growth with few defects.

[0039] In one embodiment, step S2 specifically includes the following steps: S21: Melt Al and Ti blocks in the first melting tank to obtain an AlTi master alloy. The melting points of Al and Ti blocks are below 2000K.

[0040] S22: Nb blocks and Cr blocks are smelted in the second smelting tank to obtain NbCr master alloy.

[0041] S23: The AlTi master alloy and NbCr master alloy are placed in the third melting tank and repeatedly melted by electric arc more than 20 times. After cooling, an AlTiNbCr high-entropy alloy ingot is obtained. Repeated melting more than 20 times is to ensure that the alloy block is completely melted and has a uniform composition.

[0042] Specifically, the third smelting tank is larger than the first and second smelting tanks.

[0043] S24: AlTiNbCr high-entropy alloy ingots are cut to the target size using wire cutting method to obtain AlTiNbCr high-entropy alloy targets.

[0044] Specifically, the target dimensions of the AlTiNbCr high-entropy alloy target are 50 mm in diameter and 4 mm in thickness.

[0045] Preferably, the AlTiNbCr high-entropy alloy target has a grain size of 1-20 μm and a density of over 98%. The density of the target can further improve the uniformity of the coating composition. Alternatively, a grain size of 5-15 μm is preferred.

[0046] In this embodiment, after the vacuum electric arc furnace is energized by the electrodes introduced from the top of the furnace and the water-cooled crystallizer at the bottom of the furnace, an electric arc is generated. The heat of the electric arc melts the metal or alloy and solidifies it in the crystallizer.

[0047] To verify the performance of the AlTiNbCr high-entropy nitride coated turning tool of the present invention, in a specific embodiment, the AlTiNbCr high-entropy nitride coated turning tool of the present invention was continuously turned with an uncoated turning tool, a TiN coated turning tool, and a TiAlN coated turning tool of the same type until the turning tool failed.

[0048] It should be noted that the thickness of the TiN coating, TiAlN coating, and AlTiNbCr high-entropy nitride coating is the same, and the sputtering method is magnetron sputtering.

[0049] According to the ISO recommended dulling standard for carbide coated tools, the following criteria are used to judge the failure of turning tools: (1) If the wear marks in the middle area of ​​the wear band on the flank face are relatively uniform, the dulling standard is VBmax=300μm; (2) If the wear marks on the flank face are irregular, the dulling standard is VBmax=600μm; (3) When measuring the width of the wear band on the flank face corresponding to each time interval, if the wear marks are regular, measure the width four times and take the average value as the wear amount; (4) If the wear marks are irregular, take the maximum width of the wear band area as the wear amount. Alternatively, the effective life of the turning tool can be judged by whether the surface roughness of the sample obtained by turning exceeds the standard. The surface roughness value Ra of the sample required for precision machining is ≤0.4μm.

[0050] Therefore, in this embodiment, the effective life, thickness wear bandwidth, turning life, and surface roughness per hour of the above-mentioned cutting tools are compared. The comparison results are as follows: Figures 4 to 13 As shown.

[0051] Depend on Figure 4 It can be seen that, Figure 4 The top two images are SEM images of the cutting tips of high-entropy nitride coated turning tools, the bottom two images are SEM images of the cutting tips of uncoated turning tools, the left two images are SEM images of the cutting tips of two types of turning tools after 13 hours of continuous operation, and the left two images are SEM images of the cutting tips of two types of turning tools after 37 hours of continuous operation. The cutting tips of the uncoated turning tools could not withstand the continuous operation for about 13 hours and broke down and became unusable. The cutting tips of the high-entropy coated tools remained intact after 37 hours of continuous operation and had a normal amount of chips attached.

[0052] Depend on Figure 5 It can be seen that after continuous turning of 37hSK4 bar with a high-entropy nitride coated turning tool, the wear band width on the flank face is 37.5μm, which is far below the wear standard specified by ISO.

[0053] from Figure 6 As can be seen, starting from the 5th working hour, the surface roughness of the sample has consistently failed to meet the requirements of precision machining, indicating that its effective turning life is 4 hours.

[0054] from Figure 7 As can be seen, starting from the 32nd working hour, the surface roughness of the sample no longer meets the requirements for precision machining, indicating that its effective turning life is 31 hours, which is about 7 times the life of an uncoated turning tool. This reduces the time and cost of changing turning tools and effectively improves machining efficiency.

[0055] from Figure 8 From this, we can know that Figure 8 The image on the left shows the SEM cross-sectional morphology of the high-entropy nitride coating, and the image on the right shows the SEM cross-sectional morphology of the TiN coating. The coating thicknesses obtained by sputtering using the same technique are 1.425 μm and 1.325 μm, respectively, which are basically maintained at the same thickness level, thus minimizing the influence of film thickness on the tool life.

[0056] from Figure 9 From this, we can know that Figure 9 The top two images are SEM images of the tool tip of a high-entropy nitride coated turning tool, and the bottom two images are SEM images of the tool tip of a TiN coated turning tool. The left two images are SEM images of the tool tips of two different turning tools after 10 hours, and the left two images are SEM images of the tool tips of two different turning tools after 20 hours. The TiN coated turning tool broke down between 10 and 20 hours, while the high-entropy coated tool remained intact with a normal amount of chips after 37 hours of continuous operation.

[0057] from Figure 10As can be seen, starting from the 17th working hour, the surface roughness of the sample no longer meets the roughness requirements of precision machining, indicating that its effective turning life is about 16 hours.

[0058] from Figure 11 Let's take a look. Figure 11 The image on the left shows the SEM cross-sectional morphology of the high-entropy nitride coating, and the image on the right shows the SEM cross-sectional morphology of the TiAlN coating. The coating thicknesses of the high-entropy nitride coating and the TiAlN coating, obtained by sputtering using the same technology, are 1.425 μm and 1.325 μm, respectively, which are basically maintained at the same thickness level, thus minimizing the influence of film thickness on the tool life.

[0059] from Figure 12 Let's take a look. Figure 12 The top two images are SEM images of the tool tip of a high-entropy nitride coated turning tool, and the bottom two images are SEM images of the tool tip of a TiAlN coated turning tool. The left two images are SEM images of the tool tips of two different turning tools after 10 hours, and the left two images are SEM images of the tool tips of two different turning tools after 20 hours. The TiAlN coated turning tool broke down between 10 and 20 hours, while the high-entropy coated tool remained intact with a normal amount of chips after 37 hours of continuous operation.

[0060] from Figure 13 As can be seen, starting from the 16th working hour, the surface roughness of the sample has consistently failed to meet the requirements of precision machining, indicating that its effective turning life is approximately 15 hours.

[0061] In summary Figures 4 to 13 Analysis shows that the high-entropy nitride coated turning tool of the present invention has a longer life and more stable performance compared with TiN coated turning tools and TiAlN coated turning tools.

[0062] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A precision machining ultra-long life high-entropy nitride coated turning tool, characterized in that, Includes the cutting tool body and a multi-layer gradient coating attached to the surface of the cutting tool body; The multilayer gradient coating consists of, from the inside out, a Cr base layer, a CrN transition layer, and an AlTiNbCrN working layer. The atomic ratio of Al, Ti, Nb and Cr in the AlTiNbCrN working layer is 1:1:1:

1.

2. A method for preparing a precision machining ultra-long life high-entropy nitride coated turning tool, used to prepare the precision machining ultra-long life high-entropy nitride coated turning tool as described in claim 1, characterized in that, Includes the following steps: S1: Clean and dry the raw materials, including Al blocks, Ti blocks, Nb blocks, and Cr blocks; S2: AlTiNbCr high-entropy alloy target material was prepared by vacuum arc furnace melting; S3: Fix the lathe tool body on the turntable inside the magnetron sputtering vacuum chamber, align the tool tip with the target source, install AlTiNbCr high-entropy target material at the RF target position, and install pure Cr target material at the DC target position. S4: Evacuate until 2.5E -5 Below Pa; S5: Set the substrate temperature to 450℃, and use argon gas to perform glow discharge cleaning on the target and the cutting tool body during the heating process; S6: After the substrate temperature reaches 450℃, use a pure Cr sputtering target to perform a bottom layer sputtering on the cutting tool body; S7: After the base layer sputtering is completed, adjust Ar:N2=7:1 and use pure Cr target material to perform transition layer sputtering on the Cr base layer; S8: After the transition layer sputtering is completed, the working layer is sputtered using an AlTiNbCr high-entropy target. After the working layer sputtering is completed, the target cutting tool is obtained, and the working gas pressure is kept less than 1 Pa.

3. The method for preparing ultra-long life high-entropy nitride coated turning tools for precision machining according to claim 2, characterized in that, Step S2 specifically includes the following steps: S21: Melt Al blocks and Ti blocks in the first melting tank to obtain an AlTi intermediate alloy; S22: Melt Nb blocks and Cr blocks in the second melting tank to obtain NbCr master alloy; S23: Place the AlTi master alloy and NbCr master alloy in the third melting tank and repeatedly melt them by electric arc more than 20 times. After cooling, obtain the AlTiNbCr high-entropy alloy ingot. S24: The AlTiNbCr high-entropy alloy ingot is cut into AlTiNbCr high-entropy alloy targets of the target size using wire cutting method.

4. The method for preparing ultra-long life high-entropy nitride coated turning tools for precision machining according to claim 2, characterized in that, In step S1, the purity of the raw materials Al blocks, Ti blocks, Nb blocks and Cr blocks is greater than or equal to 99.99%, and the raw materials are washed sequentially with acetone, alcohol and deionized water; In step S2, the vacuum degree of the vacuum electric arc furnace is 0.001-0.1 Pa.

5. The method for preparing ultra-long life high-entropy nitride coated turning tools for precision machining according to claim 2, characterized in that, In step S5, the parameters for glow discharge cleaning are: DC power 20W, bias voltage 400V, argon flow rate 20 sccm / min, and cleaning time 20 min.

6. The method for preparing ultra-long life high-entropy nitride coated turning tools for precision machining according to claim 2, characterized in that, In step S6, the sputtering parameters for the bottom layer are as follows: the power of the pure Cr target increases from 20W to 200W within 6 minutes at a rate of 30W / min; the bias voltage decreases from 400V to 200V within 5 minutes at a rate of 40V / min; the argon flow rate is set to 20sccm / min; and the sputtering time is 10 min.

7. The method for preparing ultra-long life high-entropy nitride coated turning tools for precision machining according to claim 2, characterized in that, In step S7, the sputtering parameters for the transition layer are: pure Cr target power 200W, bias voltage 200V, and sputtering time 20min.

8. The method for preparing ultra-long life high-entropy nitride coated turning tools for precision machining according to claim 2, characterized in that, In step S8, the sputtering parameters for the working layer are: AlTiNbCr high-entropy alloy target power 200W, bias voltage 200V, and sputtering time 240min.

9. The method for preparing ultra-long life high-entropy nitride coated turning tools for precision machining according to claim 3, characterized in that, The target dimensions of the AlTiNbCr high-entropy alloy target are 50 mm in diameter and 4 mm in thickness.

Images