Cutter composite coating with long cutting life and preparation method thereof

Abstract

The invention relates to the technical field of machining cutter cutting and surface treatment, and discloses a cutter composite coating with long cutting life and a preparation method of the cutter composite coating. High-power pulse magnetron sputtering synchronous pulse bias voltage is used for carrying out composite coating deposition on the surface of a cutter base body; the deposition of the composite coating comprises alternate deposition of TiAlN thin layers and (CrAl) 2O3 thin layers and deposition of a TiSiN thin layer on the outermost layer, so that the TiAlN / (CrAl) 2O3 / TiSiN multi-layer composite coating is obtained. By optimizing the structural design and the deposition process, the prepared composite coating shows comprehensive properties such as high hardness, high wear resistance and excellent high-temperature oxidation resistance, and has a remarkable effect on prolonging the service life of a cutter under a dry high-speed cutting working condition; a TiAlN thin layer, a (CrAl) 2O3 thin layer and a TiSiN thin layer are alternately deposited to construct the cutter composite coating, and the performance of the cutter is remarkably improved through the synergistic effect of all functional layers; and the high-power pulse magnetron sputtering technology is matched with synchronous pulse bias for deposition, the prepared coating is compact in structure, and the service life of the cutter under severe conditions is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of machining tool cutting and surface treatment, and in particular to a tool composite coating with a long cutting life and a preparation method thereof. Background Art

[0002] With the rapid development of strategic emerging industries such as aerospace, new energy, and modern manufacturing, the demand for high-performance materials is growing. Advanced materials such as high-temperature alloys, titanium alloys, and high-carbon steel are widely used in high-end manufacturing fields such as aircraft engines, gas turbines, and nuclear power equipment due to their excellent overall performance, including high strength, good high-temperature stability, and outstanding corrosion resistance. However, these materials present significant machining difficulties during cutting. The tool surface not only withstands extremely high cutting temperatures and enormous cutting forces, but is also prone to adhesion to the material being machined, leading to premature tool wear, chipping, and even failure.

[0003] At the same time, in response to the development trend of green manufacturing and the industry's demand for improved processing efficiency, advanced processing technologies such as dry cutting and high-speed cutting are gradually replacing traditional wet cutting processes. This shift in processing methods places more stringent requirements on cutting tools: on the one hand, the tools need to maintain excellent cutting performance without cooling and lubrication; on the other hand, they must adapt to higher cutting speeds and greater cutting loads. These challenges require breakthrough innovations in the selection of tool materials, structural design, and surface treatment technologies. Specifically, it is necessary to systematically improve the heat resistance and wear resistance of the tool base material, the optimized design of the tool geometry, and the nano- and multi-layered surface coating technology to meet the modern manufacturing industry's growing demand for efficient, precise, and green processing.

[0004] The development of high-performance coatings plays a decisive role in improving the service performance of cutting tools under extreme cutting conditions. Compared with single-layer coatings with a single function, multi-layer coatings and nano-composite coatings have become research hotspots and key development directions in the current industrial field due to their excellent comprehensive performance. Among them, the (CrAl)2O3 coating with a stable phase has attracted much attention due to its unique thermal stability. Under high-temperature conditions, the coating can maintain a stable crystal structure and mechanical properties. At the same time, its low thermal conductivity can effectively block the large amount of heat generated during the cutting process from being transferred to the substrate, thereby significantly reducing the risk of thermal damage to the tool substrate. It shows great application potential in the cutting of difficult-to-process materials such as high-temperature alloys. In addition, the use of traditional magnetron sputtering technology cannot stably obtain (CrAl)2O3 coatings. Because the (CrAl)2O3 coating has high dielectric properties, a large amount of charge will accumulate on the target surface due to the formation of an insulating (CrAl)2O3 thin layer during coating deposition. When the charge accumulates sufficiently, a breakdown phenomenon will occur, damaging the equipment. Therefore, the traditional magnetron sputtering technology cannot stably obtain such coatings. In addition, the (CrAl)2O3 coating is very brittle. As a tool coating alone, it faces the risk of collapse. Not only will it not increase the service life of the coating, it may also cause the surface quality of the workpiece to deteriorate. Summary of the Invention

[0005] The present invention aims to provide a composite coating for cutting tools with a long cutting life and a preparation method thereof. A self-lubricating TiSiN coating, a highly wear-resistant TiAlN coating, and a heat-insulating (CrAl)2O3 coating are alternately grown to form a composite coating for cutting tools with a long cutting life. The composite coating not only fully utilizes the advantages of the (CrAl)2O3 coating, but also achieves stable deposition of the (CrAl)2O3 coating. The (CrAl)2O3 coating is used as a protective layer for the cutting tool to extend its service life under harsh conditions. The coating is particularly suitable for dry high-speed cutting scenarios.

[0006] The basic solution provided by the present invention is: a method for preparing a composite coating for a tool with a long cutting life, comprising depositing a composite coating on the surface of a tool substrate using high-power pulsed magnetron sputtering with a synchronous pulse bias; the composite coating deposition comprises alternating deposition of TiAlN thin layers and (CrAl)2O3 thin layers and deposition of an outermost TiSiN thin layer to obtain a TiAlN / (CrAl)2O3 / TiSiN multilayer composite coating.

[0007] The present invention also provides a tool composite coating with long cutting life, which is prepared based on a method for preparing a tool composite coating with long cutting life; the number of coating layers is ≥7, and the total thickness of the coating is 4-6 μm.

[0008] The working principle and advantages of the present invention are:

[0009] Compared with the existing technology, by optimizing the structural design and deposition process, the prepared composite coating exhibits comprehensive properties such as high hardness, high wear resistance and excellent high-temperature oxidation resistance, which has a significant effect on improving the service life of the tool under dry high-speed cutting conditions.

[0010] (1) The present invention constructs a tool composite coating by alternately depositing TiAlN thin layers, (CrAl)2O3 thin layers and TiSiN thin layers. The synergistic effect of each functional layer significantly improves the tool performance. Specifically, the composite coating adopts a multi-layer alternating deposition structure, consisting of a high-wear-resistant TiAlN layer, a heat-insulating (CrAl)2O3 layer and a self-lubricating TiSiN layer. The TiAlN layer provides basic mechanical performance guarantee for the coating with its excellent high-temperature stability and wear resistance; the (CrAl)2O3 layer has the characteristics of low thermal conductivity, which can effectively block the large amount of heat generated during the cutting process from being transferred to the interior of the coating, thereby preventing the tool from failing due to thermal damage; the TiSiN layer significantly reduces tool wear through its self-lubricating properties; at the same time, the bottom functional layer (i.e., the first layer) TiAlN has the maximum thickness, which is several dozen times thicker than the other layers to ensure the basic performance of the coating; the heat-insulating layer (CrAl)2O3 adopts the minimum thickness to achieve the best heat insulation effect. This multi-layer composite structure design fully utilizes the advantages of each functional coating and significantly improves the service life and processing efficiency of the tool through synergistic effects. During dry high-speed cutting, coated tools generate a large amount of heat because they are constantly in a high-pressure and friction environment. For workpiece materials with low thermal conductivity, the heat generated during the cutting process cannot be quickly dissipated through the cutting process, resulting in a large amount of heat accumulating on the coating surface and rapidly transferring to the tool surface. This will cause a large number of thermal cracks between the tool and the coating, resulting in tool failure. The present invention utilizes the thermal insulation function of the (CrAl)2O3 layer to step-by-step suppress the large amount of heat generated during the cutting process from entering the coating, ensuring that each functional layer TiAlN layer plays its full role, which plays an important role in improving the cutting efficiency and service life of the tool. At the same time, the self-lubricating TiSiN layer is deposited on the outermost layer to provide better wear resistance in the early stage of cutting at lower temperatures, which is also of great significance for delaying the service life of the tool.

[0011] (2) The present invention utilizes high-power pulsed magnetron sputtering technology and combines it with synchronous pulse bias voltage for multi-layer deposition to prepare a coating with excellent performance. First, the tool coating has a multi-layer structure. The coating thickness can be precisely controlled by regulating the single-layer deposition time. The prepared multi-layer structure coating has low residual stress, a dense organizational structure, and no obvious defects inside the coating. It can significantly improve the bonding strength and wear resistance between the coating and the substrate, thereby extending the service life of the tool. Secondly, in the coating deposition process, an innovative combination of a high-power pulse power supply and a synchronous high-power pulse bias power supply is used. This technical solution effectively reduces the risk of target material oxidation poisoning, makes it easier to obtain a (CrAl)2O3 thin layer with a stable structure, ensures the stability of the coating preparation process, and provides a reliable guarantee for obtaining high-performance tool coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic flow chart of a method for preparing a composite coating for a tool with a long cutting life provided by an embodiment of the present invention;

[0013] Figure 2 A schematic diagram of a composite coating deposition process according to an embodiment of the present invention;

[0014] Figure 3 A schematic structural diagram of a composite coating for a tool with a long cutting life provided by an embodiment of the present invention;

[0015] Figure 4 This is a cross-sectional morphology diagram of the multilayer composite coating of Example 1 of the present invention;

[0016] Figure 5 Schematic diagram of the wear morphology of the front and rear tool faces and the service life of the multi-layer composite coating tool after cutting a solid solution state 304 stainless steel bar in Example 1 of the present invention;

[0017] Figure 6 This is a cross-sectional morphology diagram of the multilayer composite coating of Comparative Example 1 of the present invention;

[0018] Figure 7 Schematic diagram of the wear morphology of the front and rear tool faces and the service life of the multi-layer composite coating tool after cutting a solid solution state 304 stainless steel bar in Comparative Example 1 of the present invention;

[0019] Figure 8 Schematic diagram of the wear morphology of the front and rear tool faces and the service life of the coated tool after cutting a solid solution state 304 stainless steel bar in Comparative Example 2 of the present invention;

[0020] Figure 9 This is a schematic diagram of the wear morphology of the front and rear tool faces and the service life of the coated tool after cutting the solid solution state 304 stainless steel bar in comparative example 3 of the present invention. DETAILED DESCRIPTION

[0021] The following is a further detailed description through specific implementation methods:

[0022] The embodiment is basically as shown in the attached Figure 1 A method for preparing a composite coating for a tool with a long cutting life is shown. The method includes depositing the composite coating on the surface of a tool substrate using high-power pulsed magnetron sputtering with a synchronous pulsed bias. The composite coating deposition involves alternating thin TiAlN and (CrAl)2O3 layers, followed by an outermost TiSiN layer, to form a TiAlN / (CrAl)2O3 / TiSiN multilayer composite coating. The TiAlN coating exhibits high wear resistance, the TiSiN coating exhibits self-lubrication, and the stable (CrAl)2O3 coating possesses unique thermal stability.

[0023] In specific applications, the tool substrate is pretreated before the composite coating is deposited; after the composite coating is deposited, the coated tool sample is post-processed.

[0024] 1. The tool base pretreatment includes dry sandblasting, wet sandblasting and ultrasonic cleaning; conventional process is used.

[0025] The tool base material includes any one of cemented carbide, ceramic, high temperature alloy and ultra-high strength steel; the tool type includes any one of turning tool, milling cutter and gear shaping cutter.

[0026] 2. If Figure 2 As shown, composite coating deposition includes:

[0027] a. The coating chamber is vacuumed and the tool substrate is heated;

[0028] b. Etching of tool substrate surface;

[0029] c. Target surface cleaning;

[0030] de. Alternately depositing TiAlN and (CrAl)2O3 composite coatings; d. Depositing a first TiAlN thin layer and a second (CrAl)2O3 thin layer, and cleaning the target surface after both layers are deposited; e. Alternately depositing additional TiAlN thin layers and (CrAl)2O3 thin layers in the same order as in d. During this process, the single-layer thickness is controlled by varying parameters that characterize the effects of coating thickness;

[0031] f. Depositing the outermost TiSiN thin layer to obtain a tool sample having a TiAlN / (CrAl)2O3 / TiSiN multilayer composite coating deposited on the surface;

[0032] g. The tool sample is taken out after naturally cooling to the preset temperature under vacuum environment.

[0033] Specifically:

[0034] a. Place the cleaned and dried tool substrate on the workpiece holder and send it into the coating chamber. Use a mechanical pump and a molecular pump to reduce the vacuum degree of the coating chamber to 3mPa; then heat the tool substrate for >1h at a temperature of 450-500℃ and maintain the substrate rotation speed at 0.3-1r / min.

[0035] b. After heating, the surface of the tool substrate is etched. The etching power supply uses a high-power pulse power supply, the voltage is set to -100~-300V, the frequency is 2000~4000Hz, the pulse width is 70~200μs, the etching gas uses Ar, the flow rate is set to 320~520mln, the etching time is >1h, and the substrate rotation speed is maintained at 1~3r / min during this process.

[0036] c. After the tool surface treatment is completed, the target surface is sputtered. Before turning on the power, all target baffles are closed, and then sputtering gas Ar is introduced with a flow rate of 600-1250mln and the target cathode power supply is turned on with a power of 8000-12000W and a discharge time of 190-600s to complete the target surface cleaning;

[0037] d. After the impurities on the target surface are removed, the first layer of TiAlN layer is deposited on the tool surface. Before the TiAl target power supply is turned on, sputtering gas Ar and reaction gas N2 are introduced, where the Ar flow rate is 424~636mln and the N2 flow rate is 50~300mln. After the gas flow in the vacuum chamber is stable, the corresponding TiAl target baffle is opened and the cathode power supply and bias power supply are turned on at the same time. Both the cathode power supply and the bias power supply use synchronous high-power pulse power supplies. The cathode power supply power is set to 8000~12000W, the frequency is 4000Hz, the pulse width is 70μs, the bias power supply voltage is set to -60~-100V, the pulse width is 60μs, the delay time is 40μs, the first layer of TiAlN coating time is 3600~7200s, and the substrate speed is 1r / min.

[0038] After the deposition of the first layer of TiAlN coating is completed, all cathode power supplies, bias power supplies and gas are turned off, and then the second layer of (CrAl)2O3 thin layer is deposited. Before the CrAl target power supply is turned on, the sputtering gas Kr and the reaction gas O2 are introduced, and the flow rates are controlled at 488mln and 27mln respectively. After the gas flow in the vacuum chamber is stable, the corresponding CrAl target baffle is opened, and the cathode power supply and bias power supply are turned on at the same time. Both the cathode power supply and the bias power supply use synchronous high-power pulse power supplies. The cathode power supply power is set at 2000W, the frequency is 1500Hz, the pulse width is 30μs, the bias power supply voltage is set to -100V, the pulse width is 80μs, the coating time is 2000~4000s, and the substrate speed is 1r / min.

[0039] After the deposition of the second (CrAl)2O3 thin layer is completed, the target surface cleaning stage of step c is performed again.

[0040] e. The process of depositing the third TiAlN thin layer and the fourth (CrAl)2O3 thin layer, as well as the fifth TiAlN thin layer and the sixth (CrAl)2O3 thin layer on the tool surface is the same as the sequence of depositing the first TiAlN thin layer and the second (CrAl)2O3 thin layer. The difference is that the single layer thickness is controlled by changing the coating time.

[0041] f. After the alternating deposition of the TiAlN thin layer and the (CrAl)2O3 thin layer is completed, the outermost TiSiN thin layer is deposited on the tool surface. Before turning on the TiSi target cathode power supply, the reaction gas N2 and the sputtering gas Ar are introduced, with the Ar flow rate being 424-636 mln and the N2 flow rate being 100-200 mln. When the gas flow in the vacuum chamber stabilizes, the corresponding TiSi target baffle is opened, and the cathode power supply and bias power supply are turned on simultaneously. Both the cathode power supply and the bias power supply use synchronized high-power pulse power supplies. The cathode power supply power is set to 8000-12000 W, the frequency is 4000 Hz, and the pulse width is 70 μs. The bias power supply voltage is set to -60--100 V, the pulse width is 60 μs, and the delay time is 40 μs. The coating time of the TiSiN thin layer is 4200-6000 s. During this stage, the substrate speed is controlled at 1 r / min. During this process, the thickness of the TiSiN thin layer can be changed by changing the coating time of the TiSiN thin layer.

[0042] g. After steps a to f are completed, turn off the cathode power supply, bias power supply, and heating power supply, and remove the sample after the sample is naturally cooled to 180°C under a vacuum environment.

[0043] 3. Post-processing of the coated tool samples with TiAlN / (CrAl)2O3 / TiSiN multilayer composite coating deposited on the surface was performed, including wet sandblasting and ultrasonic cleaning. The wet sandblasting and ultrasonic cleaning were processed using conventional processes, which were different from the corresponding processing time in the tool pretreatment process. The processing time in the tool pretreatment process was relatively long.

[0044] The composite coating structure prepared by the above preparation method is as follows Figure 3 For illustration, it can be understood that the composite coating structure obtained by continuing to increase the number of coating layers and adjusting the thickness of the single layer on this basis falls within the technical protection scope of the present invention.

[0045] The tool composite coating is a TiAlN / (CrAl)2O3 / TiSiN multilayer composite coating with ≥7 layers and a total coating thickness of 4-6 μm. It should be noted that because the coating thickness on the front and rear cutting edges of the tool prepared using this type of PVD coating equipment and clamping method varies somewhat, the front cutting edge is generally thinner than the rear cutting edge, with a typical rear cutting edge thickness of 5-6 μm. Therefore, a total coating thickness of 4-6 μm is a reasonable design for this solution.

[0046] Taking the area close to the tool base as the first layer, when the first layer is a TiAlN thin layer and the second layer is a (CrAl)2O3 thin layer and they are alternately deposited, the thickness of the first TiAlN thin layer is 2.0-3.5 μm, and the thickness of the other TiAlN thin layers is 0.2-0.3 μm; the thickness of the (CrAl)2O3 thin layer is 0.15-0.40 μm; and the thickness of the TiSiN thin layer is 0.8-1.0 μm.

[0047] If the number of coating layers is 7, the data can be referred to as follows: the first layer is close to the tool substrate, which is a TiAlN thin layer with a thickness of 2.0~3.5μm, the second layer is a (CrAl)2O3 thin layer with a thickness of 0.15~0.40μm, the third layer is a TiAlN thin layer with a thickness of 0.2~0.3μm, the fourth layer is a (CrAl)2O3 thin layer with a thickness of 0.15~0.40μm, the fifth layer is a TiAlN thin layer with a thickness of 0.2~0.3μm, the sixth layer is a (CrAl)2O3 thin layer with a thickness of 0.15~0.40μm, and the seventh layer is a TiSiN thin layer with a thickness of 0.8~1.0μm.

[0048] The cutting life of the tool composite coating obtained by the preparation method of this scheme is ≥40 minutes when cutting solid solution 304 stainless steel bars in a dry high-speed cutting mode.

[0049] The cutting parameters used to evaluate the service life of the composite coating produced by this method include a cutting speed of Vc = 200 m / min, a cutting depth of D = 1 mm, and a feed rate of ft = 0.2 mm / rev. These cutting parameters represent dry, high-speed cutting, a very harsh cutting environment, further demonstrating the superior service performance of this coating. If, under these cutting parameters, the tool's operating life exceeds that of a conventionally coated tool, then the tool's cutting life will be significantly increased under actual operating conditions.

[0050] This embodiment provides a composite coating for a tool with a long cutting life and a preparation method thereof. Compared with the existing technology, the prepared composite coating exhibits comprehensive properties such as high hardness, high wear resistance and excellent high-temperature oxidation resistance through optimized structural design and deposition process, which has a significant effect on improving the service life of the tool under dry high-speed cutting conditions.

[0051] Example 1:

[0052] A method for preparing a composite coating for a tool with a long cutting life, comprising:

[0053] 1. Before coating deposition, the tool substrate needs to be pretreated to remove oil and impurities that the tool substrate is exposed to during the processing process, including dry sandblasting, wet sandblasting and ultrasonic cleaning.

[0054] 2. Coating deposition:

[0055] a: Use compressed air to dry the tool substrate and place it on the workpiece holder and send it into the coating chamber. Use a mechanical pump and a molecular pump to evacuate the coating chamber to a vacuum of 3mPa. Then heat the tool substrate for 1 hour at a temperature of 500°C and maintain the substrate rotation speed at 0.3r / min.

[0056] b: Tool surface etching treatment, the etching power supply uses a high-power pulse power supply, the voltage is set to -200V, the frequency is 4000Hz, the pulse width is 70μs, the etching gas uses Ar, the flow rate is set to 320mln, the etching time is 1h, and the substrate rotation speed is maintained at 1r / min during this process.

[0057] c: Sputter the target surface. Close all target baffles before turning on the power. Then introduce sputtering gas Ar with a flow rate of 1250mln and turn on the required target cathode power with a power of 12000W and a discharge time of 190s to remove impurities on the target surface.

[0058] d: Start depositing the first TiAlN thin layer on the tool surface. Before the TiAl target power supply is turned on, sputtering gas Ar and reaction gas N2 are introduced, where the Ar flow rate is 520mln and the N2 flow rate is 120mln. When the gas flow in the vacuum chamber is stable, open the corresponding TiAl target baffle, and turn on the cathode power supply and bias power supply at the same time. Both the cathode power supply and the bias power supply use synchronous high-power pulse power supplies. The cathode power supply power is set to 12000W, the frequency is 4000Hz, and the pulse width is 70μs. The bias power supply voltage is set to -60V, the pulse width is 60μs, the delay time is 40μs, the coating time of the first TiAlN thin layer is 7200s, and the substrate speed is 1r / min.

[0059] After the deposition of the first layer of TiAlN thin layer is completed, all cathode power supplies, bias power supplies and gas are turned off, and then the deposition of the second layer of (CrAl)2O3 thin layer is started. During this process, the sputtering gas and reaction gas are replaced with Kr and O2 respectively, and the flow rate is controlled at 488mln and 27mln. After the gas flow is stable, the target baffle is opened and the cathode power supply and bias power supply are turned on at the same time. The cathode power supply and bias power supply also use synchronous high-power pulse power supplies. The cathode power supply power is set to 2000W, the frequency is 1500Hz, the pulse width is 30μs, the bias power supply voltage is set to -100V, the pulse width is 80μs, the coating time is 3000s, and the substrate speed is 1r / min.

[0060] After the second (CrAl)2O3 thin layer is deposited, the target cleaning phase in step c is repeated. Similarly, before turning on the power, all target shutters are closed. Ar gas is introduced as a sputtering gas at a flow rate of 1250 ml / min and the target cathode power supply is turned on at 12,000 W for 600 seconds.

[0061] e. Deposit a third TiAlN thin layer using the same deposition parameters and process as the first TiAlN thin layer in step d, except that the thickness of the single layer was varied by varying the coating time. The coating time for the third TiAlN thin layer was 600 s. Similarly, the deposition parameters and process for the fourth (CrAl)2O3 thin layer were the same as those for the second (CrAl)2O3 thin layer in step d. The thickness of the single layer was varied by varying the coating time. The coating time was 900 s. After the third and fourth layers were deposited, the target was cleaned using the same parameters as above, with a cathode discharge time of 600 s.

[0062] The deposition parameters of the fifth and sixth TiAlN thin layers and (CrAl)2O3 thin layers are the same as those of the third and fourth layers described above.

[0063] f. After the alternating deposition of the TiAlN thin layer and the (CrAl)2O3 thin layer is completed, the outermost TiSiN layer is deposited on the tool surface. Similarly, before turning on the cathode power supply, the reaction gas N2 and the sputtering gas Ar are introduced, where the Ar flow rate is 450mln and the N2 flow rate is 100mln. When the gas flow in the vacuum chamber is stable, the corresponding TiSi target baffle is opened, and the cathode power supply and the bias power supply are turned on at the same time. Both the cathode power supply and the bias power supply use synchronous high-power pulse power supplies. The cathode power supply power is set to 12000W, the frequency is 4000Hz, and the pulse width is 70μs. The bias power supply voltage is set to -60V, the pulse width is 60μs, the delay time is 40μs, and the coating time of the TiSiN thin layer is 5400s. During this stage, the substrate speed is controlled at 1r / min.

[0064] g. After steps a to f are completed, turn off the cathode power supply, bias power supply, and heating power supply, and remove the sample after the sample is naturally cooled to 180°C under a vacuum environment.

[0065] 3. The tool samples with TiAlN / (CrAl)2O3 / TiSiN multilayer composite coating deposited on the surface were post-processed, including wet sandblasting and ultrasonic cleaning.

[0066] The cross-sectional morphology of the composite coating of the tool in this embodiment is as follows Figure 4 As shown in the figure, it can be clearly observed that the coating is divided into seven layers, consisting of three layers of TiAlN, three layers of (CrAl)2O3 and one layer of TiSiN, with a total thickness of 5.3μm. Among them, the bottom layer TiAlN is the thickest, and the oxide layer is very thin. Its main function is to prevent external heat from diffusing to the inside and affecting the coating performance.

[0067] The cutting performance of the tool coating in this embodiment is as follows Figure 5 As shown in the figure, it can be seen that in the initial stage of wear, the main cutting edge segment removes the hardened layer of the previous pass, resulting in micro-chipping, which then evolves into groove wear. The wear band on the cutting edge shows non-uniform characteristics. As the cumulative cutting time increases, the groove depth increases, chipping occurs in the direction of the groove adjacent to the secondary cutting edge, the width increases, and obvious wear marks of the coating can be observed. In the stable wear stage, the wear rate of the flank surface remains stable, and only the groove wear evolves. In the severe wear stage, the groove width expands to 946.14μm, and it evolves violently along the secondary cutting edge. The groove reduces the coating performance in the adjacent area, the edge coating fails, and the cutting life of the coated tool is 43min.

[0068] Example 2:

[0069] This embodiment provides a method for preparing a composite coating for a tool with a long cutting life, which differs from that of Example 1 in that:

[0070] Coating deposition:

[0071] a. The tool base heating temperature is 450℃.

[0072] c. Sputter the target surface with a discharge time of 600s.

[0073] e. Alternately deposit a seventh TiAlN thin layer and an eighth (CrAl)2O3 thin layer, wherein the deposition parameters and steps of the seventh TiAlN thin layer and the eighth (CrAl)2O3 thin layer are the same as those of the fifth TiAlN layer and the sixth (CrAl)2O3 thin layer in Example 1.

[0074] It can be understood that the other steps and parameters are the same as those in Example 1.

[0075] The tool composite coating prepared by the preparation method of this embodiment consists of nine layers, namely four layers of TiAlN, four layers of (CrAl)2O3 and one layer of TiSiN, with a total thickness of 5.7 μm. The wear form of the tool when cutting solid solution 304 stainless steel bar is similar to that of the embodiment, but wear failure occurs prematurely, and its cutting life is 40 minutes.

[0076] Comparative Example 1:

[0077] The method for preparing a composite coating for a tool with a long cutting life provided in this comparative example is different from that in Example 1 in terms of the composition of the outermost layer. The difference is as follows:

[0078] f. The outermost layer is a TiAlN layer, and its deposition parameters and steps are the same as those of the first TiAlN layer in step d of Example 1, and the deposition time is set to 1200s.

[0079] It can be understood that the other steps and parameters are the same as those in Example 1.

[0080] The cross-sectional morphology of the tool composite coating prepared by the preparation method of this comparative example is as follows: Figure 6 As shown in the figure, it can be clearly observed that the coating is divided into seven layers, consisting of four layers of TiAlN and three layers of (CrAl)2O3, with a total thickness of 4.2μm.

[0081] The cutting performance of the tool coating prepared in this comparative example is as follows: Figure 7 As shown in the figure, it can be seen that in the initial stage of stable wear, micro-chipping occurs on the main cutting edge, and multiple micro-chippings merge to form a larger gap. As the cutting time increases, the gap on the cutting edge becomes larger and larger, eventually leading to tool cutting failure. The service life of the coated tool is 11 minutes.

[0082] Comparative Example 2:

[0083] The coating type in this comparative example is a TiAlN single-layer tool coating. The difference from Example 1 is the coating deposition:

[0084] a. After the tool substrate is pretreated, use compressed air to dry the tool substrate and place it on the workpiece holder and send it into the coating chamber. The vacuum degree of the coating chamber is evacuated to 3mPa by a mechanical pump and a molecular pump, and then heat treatment is carried out. The heating time is 1 hour, the heating temperature is 500℃, and the substrate rotation speed is maintained at 0.3r / min.

[0085] b. After heating, the tool surface is etched. The etching power supply uses a high-power pulse power supply, the voltage is set to -200 V, the frequency is 4000 Hz, the pulse width is 70 μs, the etching gas is Ar, the flow rate is set to 620 mln, and the etching time is 1 h. During this process, the substrate rotation speed is maintained at 0.3 r / min.

[0086] c. After the tool surface treatment is completed, the target surface is sputtered. Before turning on the power, all target baffles are closed, and then sputtering gas Ar is introduced with a flow rate set to 1250mln and the required target cathode power supply is turned on with a power of 8000W and a discharge time of 190s.

[0087] d. After the target is cleaned, the coating stage is carried out. First, the corresponding target baffle is opened. Four identical TiAl alloy targets are selected as the target material. The substrate speed is controlled at 1r / min, the Ar flow rate is controlled at 530mln, and 220mln of N2 is introduced at the same time. After the gas flow is stable, the cathode power supply and bias power supply are turned on. The cathode power supply power is set to 12000W, the frequency is 4000Hz, and the pulse width is 70μs. The bias power supply voltage is -60V, the frequency is 4000Hz, the pulse width is 60μs, the delay is 40μs, and the coating time is 5000s.

[0088] It can be understood that the tool substrate pretreatment, tool sample cooling and coated tool sample post-treatment in this embodiment are the same as those in Example 1.

[0089] The thickness of the tool coating prepared by the preparation method of this comparative example is 4 μm, and the cutting performance of the tool coating is as follows: Figure 8 As shown in the figure, micro-chipping occurs at the beginning of wear, and grooves appear at 4.15 minutes. Subsequently, the flank face is dominated by groove wear. The wear rate of the grooves is lower in the direction close to the secondary cutting edge, and the coating performance is better. After 20.96 minutes, the groove depth does not increase significantly, but the grooves weaken the coating strength at the cutting edge. The grooves rapidly increase in size along the cutting edge. Finally, after 33 minutes, the coated tool fails due to the large grooves on the flank face.

[0090] Comparative Example 3:

[0091] This comparative example has the same coating type as that of comparative example 2. The main changes in comparative example 2 are the cathode power supply and bias power supply type used during coating deposition and the Ti / Al ratio in the coating. The coating deposition includes:

[0092] a. After the tool substrate is pretreated, the tool substrate is heated for 1.5 hours.

[0093] b. The etching gas Ar flow rate was set to 420 mln, the etching time was 1.2 h, and the substrate rotation speed was maintained at 1 r / min during this process.

[0094] c. The target surface is sputtered with a cathode power of 9500 W and a discharge time of 200 s.

[0095] d. After the target cleaning is completed, the coating stage is carried out. Three identical TiAl alloy targets and one pure Ti metal target are selected as the target materials. First, the TiAl alloy target and Ti target baffle are opened, the substrate speed is controlled at 1r / min, the Ar flow rate is controlled to 320mln, the Kr flow rate is controlled to 190mln, and 240mln of N2 is introduced at the same time. After the gas flow rate stabilizes, the TiAl target and Ti target power supplies and bias power supply are turned on. The cathode power supply and bias power supply both use DC power supplies. The power of the TiAl target power supply is controlled at 9500W, the power of the Ti target power supply is controlled at 4000W, the voltage of the bias power supply is set to -100V, and the coating time is 7600s.

[0096] It can be understood that the tool substrate pretreatment, tool sample cooling and coated tool sample post-treatment in this embodiment are the same as those adopted in Comparative Example 2.

[0097] The thickness of the tool coating prepared by the preparation method provided in this comparative example is 4.7 μm, and the cutting performance of the tool coating is as follows: Figure 9 As shown in the figure, in the initial stage of wear, micro-chipping occurred on both the main cutting edge and the arc segment, and the corresponding coating peeled off on the rake face. As wear progressed, a notch formed on the main cutting edge, reaching a depth of 81 μm. The coating peeled off due to the chipping of the groove and the arc segment, resulting in large-scale coating failure on the rake face, and the groove gradually expanded. In the later stages of wear, the groove depth increased sharply, weakening the strength of the area adjacent to the cutting edge and significantly increasing the width of the wear band on the flank face, ultimately leading to tool failure. The cutting life of the coated tool was 10 minutes.

[0098] In summary, the cutting life of the tool coating in the comparative example is significantly lower than that of the tool coating in the example, which further confirms the excellence of the TiAlN / (CrAl)2O3 / TiSiN multilayer composite coating tool proposed in this scheme. The combination of the self-lubricating TiSiN thin layer and the thermal insulation layer (CrAl)2O3 thin layer plays a key role in improving the tool's ability to resist wear under high temperature and high pressure. This innovative introduction of a gradient multilayer composite structure combines the intrinsic properties of different types of layers, maximizes their strengths and minimizes their weaknesses, and gives full play to the functions of the functional layer TiAlN layer, the thermal insulation layer (CrAl)2O3 layer and the lubricating layer TiSiN layer, thereby greatly improving the tool's service life. In addition, compared with the best embodiment 1, the cutting life of the coated tool in embodiment 2 is slightly reduced. This may be due to the excessive thickness of the coating, which leads to excessive residual stress in the coating, resulting in a decrease in the bonding force between the coating and the substrate, thereby causing the service life of the cutting tool to be reduced. Therefore, for the tool, its structure is strongly correlated with the type and thickness of the coating. For example, a tool with a small passivation zone cannot use a thicker coating; a soft tool substrate surface cannot use an ultra-hard coating, etc.; this further confirms that the design of the structural layout of each coating and the design of the control parameters and thickness in this scheme have a significant positive promoting effect on the excellent performance of the tool.

[0099] The above is only an embodiment of the present invention. Common knowledge such as the specific structure and characteristics of the scheme is not described in detail here. Ordinary technicians in the relevant field are aware of all common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the guidance of this application. Some typical well-known structures or well-known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for preparing a composite coating for a tool with a long cutting life, characterized in that: The method comprises depositing a composite coating on the surface of a tool substrate by using high-power pulsed magnetron sputtering with synchronous pulse bias; the composite coating deposition comprises alternating deposition of TiAlN thin layers and (CrAl)2O3 thin layers and deposition of an outermost TiSiN thin layer to obtain a TiAlN / (CrAl)2O3 / TiSiN multilayer composite coating.

2. The method for preparing a composite coating for a tool with a long cutting life according to claim 1, characterized in that: The alternating deposition of TiAlN thin layers and (CrAl)2O3 thin layers includes: depositing a first TiAlN thin layer and a second (CrAl)2O3 thin layer, and cleaning the target surface after the two layers are deposited; and alternately depositing other TiAlN thin layers and (CrAl)2O3 thin layers in the aforementioned order, and controlling the single layer thickness by changing parameters that characterize and affect the coating thickness during the process.

3. The method for preparing a composite coating for a tool with a long cutting life according to claim 1, characterized in that: Before the composite coating is deposited, the tool substrate is pretreated, wherein the tool substrate pretreatment includes dry sandblasting, wet sandblasting and ultrasonic cleaning. The composite coating deposition includes: a. evacuating the coating chamber and heating the tool substrate; b. etching the tool substrate surface; c. cleaning the target surface; d. alternating deposition of TiAlN thin layers and (CrAl)2O3 thin layers; f. depositing the outermost TiSiN thin layer to obtain a tool sample with a TiAlN / (CrAl)2O3 / TiSiN multilayer composite coating deposited on the surface; g. naturally cooling the tool sample to a preset temperature under a vacuum environment and then taking it out. After the composite coating is deposited, the coated tool sample is post-treated, wherein the coated tool sample post-treatment includes wet sandblasting and ultrasonic cleaning.

4. The method for preparing a composite coating for a tool with a long cutting life according to claim 3, characterized in that: a. Place the cleaned and dried tool substrate on a workpiece holder and place it in the coating chamber. Reduce the vacuum level in the coating chamber to 3 mPa. Then heat the tool substrate for >1 hour at a temperature of 450-500°C. Maintain a substrate speed of 0.3-1 rpm. b. After heating, the tool substrate surface is etched. The etching power supply uses a high-power pulse power supply, the voltage is set to -100 ~ -300V, the frequency is 2000 ~ 4000Hz, the pulse width is 70 ~ 200μs, the etching gas is Ar, the flow rate is set to 320 ~ 520mln, the etching time is > 1h, and the substrate speed is maintained at 1 ~ 3r / min during this process; c. After the tool surface etching treatment is completed, the target surface is sputtered. Before turning on the power, close all target baffles, introduce sputtering gas Ar, set the flow rate to 600~1250mln, and turn on the required target cathode power supply with a power of 8000~12000W and a discharge time of 190~600s to complete the target surface cleaning.

5. The method for preparing a composite coating for a tool with a long cutting life according to claim 1, characterized in that: The deposition of a TiAlN thin layer comprises the following steps: before a TiAl target power supply is turned on, a sputtering gas Ar and a reaction gas N2 are introduced, wherein the Ar flow rate is 424-636 mln and the N2 flow rate is 50-300 mln; after the gas flow rates are stabilized, a corresponding TiAl target baffle is opened and a cathode power supply and a bias power supply are simultaneously turned on, wherein both the cathode power supply and the bias power supply adopt a synchronous high-power pulse power supply, wherein the cathode power supply power is set to 8000-12000 W, the frequency is 4000 Hz, the pulse width is 70 μs, the bias power supply voltage is set to -60--100 V, the pulse width is 60 μs, and the delay time is 40 μs; the coating time of the first TiAlN thin layer is 3600-7200 s, and the coating time of other TiAlN thin layers is 600-720 s; during this process, the substrate rotation speed is 1 r / min; and after the deposition is completed, all cathode power supplies, bias power supplies and gas introductions are turned off.

6. The method for preparing a composite coating for a tool with a long cutting life according to claim 1, characterized in that: The deposition of a (CrAl)2O3 thin layer includes: before the CrAl target power supply is turned on, sputtering gas Kr and reaction gas O2 are introduced, and the flow rates are controlled at 488mln and 27mln respectively. After the gas flow rates are stable, the corresponding CrAl target baffle is opened and the cathode power supply and bias power supply are turned on at the same time. Both the cathode power supply and the bias power supply use synchronous high-power pulse power supplies. The cathode power supply power is set to 2000W, the frequency is 1500Hz, and the pulse width is 30μs. The bias power supply voltage is set to -100V, the pulse width is 80μs, the coating time is 900~4000s, and the substrate speed is 1r / min during this process. After the deposition is completed, all cathode power supplies, bias power supplies and gas introductions are turned off.

7. The method for preparing a composite coating for a tool with a long cutting life according to claim 1, characterized in that: Depositing the outermost TiSiN thin layer includes: before turning on the TiSi target power supply, first introducing sputtering gas Ar and reaction gas N2, wherein the Ar flow rate is 424-636 mln, and the N2 flow rate is 100-200 mln. After the gas flow rate is stable, the corresponding TiSi target baffle is opened, and the cathode power supply and bias power supply are turned on at the same time. Both the cathode power supply and the bias power supply use synchronous high-power pulse power supplies. The cathode power supply power is set to 8000-12000 W, the frequency is 4000 Hz, and the pulse width is 70 μs. The bias power supply voltage is set to -60--100 V, the pulse width is 60 μs, and the delay time is 40 μs. The coating time of the TiSiN thin layer is 4200-6000 s. During this process, the substrate rotation speed is 1 r / min.

8. A composite coating for a tool with a long cutting life, characterized in that: The composite coating for cutting tools with a long cutting life is prepared by the method for preparing the composite coating for cutting tools according to any one of claims 1 to 7, wherein the number of coating layers is ≥ 7 and the total thickness of the coating is 4 to 6 μm.

9. The composite coating for cutting tools with a long cutting life according to claim 8, characterized in that: Taking the area close to the tool base as the first layer, when the first layer is a TiAlN thin layer and the second layer is a (CrAl)2O3 thin layer and they are alternately deposited, the thickness of the first TiAlN thin layer is 2.0-3.5 μm, and the thickness of the other TiAlN thin layers is 0.2-0.3 μm; the thickness of the (CrAl)2O3 thin layer is 0.15-0.40 μm; and the thickness of the TiSiN thin layer is 0.8-1.0 μm.

10. The composite coating for cutting tools with a long cutting life according to claim 8, characterized in that: The cutting parameters for evaluating the service life of the tool composite coating include cutting speed Vc=200 m / min, cutting depth D=1 mm, and feed rate ft=0.2 mm / rev.

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