A method for improving the intermittent cutting performance of TiN-coated cemented carbide tools and TiN-coated cemented carbide tools

Abstract

The present application relates to the technical field of hard alloy cutter, in particular to a method for improving intermittent cutting performance of TiN coated hard alloy cutter and TiN coated hard alloy cutter.The TiN coated hard alloy cutter comprises a hard alloy cutter base and a TiN coating deposited on the surface of the hard alloy cutter base, an Al-rich surface layer is formed on the side close to the surface of the hard alloy cutter base, and a TiAlN layer is formed on the side close to the hard alloy cutter base of the TiN coating.The preparation method comprises the following steps: (1) batching, (2) mixing, (3) pressing, (4) sintering, and (5) coating.The preparation method is simple, the TiN coated hard alloy cutter prepared has good wear resistance and fracture toughness, and the intermittent cutting performance of the TiN coated hard alloy cutter can be improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hard alloy cutting tools, and particularly relates to a method for improving the intermittent cutting performance of TiN-coated hard alloy cutting tools and a TiN-coated hard alloy cutting tool. BACKGROUND

[0002] The emergence of coated hard alloy cutting tools has a landmark role in the history of cutting tools. Compared with ordinary hard alloy cutting tools, coated hard alloy cutting tools have higher surface hardness, better wear resistance, lower friction coefficient, and better surface finish of the machined workpiece, etc., greatly meeting the needs of modern manufacturing and processing industries such as high-speed machining, high-precision machining and ultra-long time machining. The coating material of the hard alloy cutting tool is generally ceramic material such as TiC, TiN, TiCN and Al2O3, among which TiN-coated cutting tools have the advantages of high hardness, high strength, corrosion resistance and good electrical conductivity, etc., and are one of the earliest applied cutting tool protective coating materials. In the cutting process, the TiN coating can significantly improve the wear resistance of the cutting tool, reduce the cutting force, increase the feed rate, reduce the adhesion of the cutting edge material, maintain the stability of the cutting geometric parameters, improve the surface quality of the workpiece, and improve the machining precision and cutting efficiency, making it an ideal coating material for low-speed cutting tools.

[0003] Although TiN coating exhibits good cutting performance, its oxidation resistance temperature is relatively low (about 500℃), and it is easily oxidized during cutting, and its wear resistance is relatively low, which limits its use to some extent. In order to improve the oxidation resistance and wear resistance of TiN coating, people try to add new elements such as Al, Zr and C to the TiN coating to form multi-element coatings such as TiAlN, TiZrN and TiAlCN. Among them, TiAlN coating has excellent mechanical and thermal properties, and the addition of Al element can improve the high-temperature oxidation resistance and working temperature of the coating. During the cutting process of TiAlN-coated cutting tools, a layer of Al2O3-rich layer is formed on the surface of the coating, which prevents further oxidation of the coating, so it is harder and more wear-resistant. In continuous cutting, it has excellent performance in resisting abrasive wear, oxidation wear, diffusion wear and adhesive wear, and shows excellent cutting performance under different machining rates (low-speed cutting or high-speed cutting), different machining methods (turning 304 stainless steel, milling spherical cast iron and drilling GG30 gray cast iron), and different workpiece materials (Inconel718 alloy, medium carbon steel SAE1045, ductile cast iron and 9GrSi2Mn alloy steel). Its service life is several times higher than that of TiN-coated cutting tools. In addition, PVD-TiAlN-coated cutting tools have better dry cutting effect than using cutting fluid when cutting at high speed, which means that the cost is reduced while the environmental pollution caused by cutting fluid is reduced, so it meets the development direction of green cutting processing.

[0004] However, when the TiAlN coating is deposited on the surface of the cemented carbide substrate, the adhesion between the TiAlN coating and the substrate is weaker than that of TiN due to the difference in crystal structure. In addition, the adhesion between the PVD coating and the substrate is not high enough because of the low coating temperature, the lack of exchange reaction in the deposition process, and the insufficient diffusion and mixing of interface elements. In the intermittent cutting process, when the alternating load shearing effect exceeds the adhesion strength between the coating and the substrate, the TiAlN coating is prone to peeling off, which leads to unstable machining quality, frequent tool replacement, reduced machining efficiency, increased tool cost, and failure to meet the requirements of modern high-speed and efficient cutting.

[0005] Therefore, there is an urgent need to provide a coated cemented carbide tool and a preparation method to improve the adhesion between the coating and the substrate and improve the intermittent cutting performance of the cemented carbide tool. SUMMARY

[0006] The purpose of the present application is to provide a method for improving the intermittent cutting performance of a TiN coated cemented carbide tool and a TiN coated cemented carbide tool to improve the adhesion between the coating and the substrate and improve the intermittent cutting performance of the cemented carbide tool.

[0007] In a first aspect, the present application provides a TiN coated cemented carbide tool, comprising a cemented carbide tool substrate and a TiN coating deposited on the surface of the cemented carbide tool substrate. An Al-rich surface layer is formed on the side of the cemented carbide tool substrate close to the surface, and a TiAlN layer is formed on the side of the TiN coating close to the cemented carbide tool substrate.

[0008] Optionally, the raw material components of the cemented carbide tool substrate, in terms of mass percentage, include (W, Ti)C: 8-20%, Co: 3-10%, Ni: 3-10%, AlN: 0.4-2.5%, W: 0.3-2.5%, and the balance being WC.

[0009] Optionally, the thickness of the TiN coating is 1-3 μm, the thickness of the Al-rich surface layer is 0.8-1.5 μm, and the thickness of the TiAlN layer is 1.2-2.8 μm.

[0010] Optionally, the TiAlN layer is a gradient coating, and in the direction of the TiN coating approaching the cemented carbide tool substrate, the Ti element gradually decreases and the Al gradually increases.

[0011] Optionally, the TiN coating has a columnar crystal structure, the cemented carbide tool substrate has an equiaxed crystal structure, and the grain size of the equiaxed crystal structure is 100-800 nm.

[0012] Optionally, the raw material components of the cemented carbide tool substrate comprise, in percentage of mass of the cemented carbide tool substrate: (W, Ti)C: 8-13%, Co: 4-6%, Ni: 4-6%, AlN: 2.0-2.5%, W: 0.3-0.8%, and the balance being WC.

[0013] In a second aspect, the present application provides a method for improving intermittent cutting performance of a TiN-coated cemented carbide tool, for preparing the aforementioned TiN-coated cemented carbide tool, comprising the following steps:

[0014] (1) batching: weighing raw material powders according to mass ratio;

[0015] (2) mixing: uniformly mixing the raw material powders with a forming agent to obtain a mixed powder;

[0016] (3) compacting: compacting the mixed powder into a compact to obtain a compact body;

[0017] (4) sintering: sintering the compact body to prepare a cemented carbide tool substrate;

[0018] (5) coating: depositing a TiN coating on the surface of the cemented carbide tool substrate.

[0019] Optionally, in step (4), the specific process of sintering comprises: sintering the compact body at 300-650°C for 1-3h, sintering at 1100-1200°C for 1-3h, and sintering at 1400-1500°C for 0.5-2h.

[0020] Optionally, in step (5), the specific process of depositing the TiN coating comprises:

[0021] (5-1) subjecting the cemented carbide tool substrate to surface micro-blasting treatment;

[0022] (5-2) heating the cemented carbide tool substrate and subjecting the surface of the cemented carbide tool substrate to Ar ion etching;

[0023] (5-3) subjecting the cemented carbide tool substrate to magnetron sputtering to form a TiN coating.

[0024] Optionally, in step (5-1), the angle of micro-blasting is 30-60°, the blasting distance is 6-12mm, the abrasive is 300-400 mesh corundum, and the blasting time is 20-50s; and / or,

[0025] in step (5-2), the temperature for heating the cemented carbide tool substrate is 400-500°C; and / or,

[0026] The specific process of Ar ion etching on the surface of the cemented carbide tool base body is: etching pressure is 1*10 -1 ~ 3*10 -1 Pa, pulse bias voltage is -300V~ -600V, empty ratio is 60~85%, direct current bias voltage is -100~ -300V, etching time is 5~20min; and / or,

[0027] In step (5-3), the specific process of magnetron sputtering includes: introducing Ar gas with a flow rate of 60~80sccm and N2 gas with a flow rate of 20~40sccm into a vacuum chamber of magnetron sputtering, keeping the total flow rate of the gas at 80~120sccm, keeping the pressure of the vacuum chamber at 4.5±5*10 -1 Pa, the self-rotation speed of the cemented carbide tool base body is 15~25rev / min, the target current is 6.0~10A, and the deposition time is 120~180min.

[0028] In summary, the present application has at least one of the following beneficial effects:

[0029] 1. The TiN coated cemented carbide tool provided by the present application comprises a cemented carbide tool base body and a TiN coating deposited on the surface of the cemented carbide tool base body, an Al-rich surface layer is formed on the side close to the surface inside the tool base body, a TiAlN layer is formed on the side close to the tool base body of the TiN coating, a continuous transition layer is formed between the Al-rich surface layer and the TiAlN layer, the internal stress caused by the difference in crystal structure is reduced, the bonding force between the TiN coating and the tool base body is improved, thereby improving the intermittent cutting performance of the cemented carbide tool.

[0030] 2. The TiN coated cemented carbide tool provided by the present application has a TiAlN layer with high wear resistance and fracture toughness, further improving the intermittent cutting performance of the TiN coated cemented carbide tool.

[0031] 3. The preparation method of the TiN coated cemented carbide tool provided by the present application has simple preparation process, strong controllability, low requirement for equipment and process, and is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is the XRD pattern of the coated cemented carbide tool, wherein a is the comparative example, b is example 1, c is example 2, d is example 3, e is example 4, and f is example 5.

[0033] Figure 2is a SEM image of the cross-sectional morphology of coated cemented carbide tools, wherein a is a comparative example, b is Example 1, c is Example 2, d is Example 3, e is Example 4, and f is Example 5.

[0034] Figure 3 is an elemental distribution map at the tool substrate and coating interface of the coated cemented carbide tool of Example 3;

[0035] Figure 4 is a friction test curve of coated cemented carbide tools, wherein a is a comparative example, b is Example 1, c is Example 2, d is Example 3, e is Example 4, and f is Example 5.

[0036] Figure 5 is a flank face morphology of intermittent cutting impact of the coated cemented carbide tool of Comparative Example 1.

[0037] Figure 6 is a flank face morphology of intermittent cutting impact of the coated cemented carbide tool of Example 3. DETAILED DESCRIPTION

[0038] The present application provides a method for improving the intermittent cutting performance of TiN coated cemented carbide tools and TiN coated cemented carbide tools. To make the purpose, technical scheme and effects of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application.

[0039] In order to improve the oxidation resistance and wear resistance of the TiN coating, a new element Al is added to the TiN coating. Al will form a layer of Al2O3 on the surface of the coating, which will prevent further oxidation of the coating, thus making the coating harder and more wear-resistant. The formation of TiAlN multi-element coating has excellent performance in continuous cutting, such as resistance to abrasive wear, oxidation wear, diffusion wear and adhesive wear. However, when the TiAlN coating is deposited on the surface of the cemented carbide substrate, the bonding strength between the TiAlN coating and the substrate is weaker than that of TiN due to the difference in crystal structure. The film-substrate bonding strength of the PVD coating is not high enough. In the case of intermittent cutting, when the alternating load shear exceeds the bonding strength of the coating and the substrate, the TiAlN coating will easily peel off.

[0040] The inventors have found, through systematic research, that the hard alloy cutter substrate prepared by adding AlN with a specific ratio in the raw material components of the hard alloy cutter substrate, through sintering, and then through subsequent micro-sand blasting treatment, ion etching treatment by heating the cutter substrate, and finally magnetron sputtering deposition of TiN, makes the AlN in the hard alloy cutter substrate diffuse to the surface of the hard alloy cutter substrate and the TiN coating, forms an Al-rich surface layer on the internal surface of the cutter substrate, and forms a TiAlN coating on the side of the TiN coating close to the cutter substrate, the crystal structure between the two is smooth, avoids large internal stress caused by lattice distortion, and improves the bonding force between the TiN coating and the cutter substrate, thereby improving the intermittent cutting performance of the hard alloy cutter.

[0041] Specifically, the application provides a TiN-coated hard alloy cutter, comprising a hard alloy cutter substrate and a TiN coating deposited on the surface of the hard alloy cutter substrate, an Al-rich surface layer is formed on the internal surface of the hard alloy cutter substrate, and a TiAlN layer is formed on the side of the TiN coating close to the hard alloy cutter substrate.

[0042] In some embodiments of the application, the raw material components of the hard alloy cutter substrate include (W, Ti)C: 8-20%, Co: 3-10%, Ni: 3-10%, AlN: 0.4-2.5%, W: 0.3-2.5%, and the balance is WC, in terms of mass percentage of the hard alloy cutter substrate; preferably, (W, Ti)C: 8-13%, Co: 4-6%, Ni: 4-6%, AlN: 2.0-2.5%, W: 0.3-0.8%, and the balance is WC. The raw material components within the above specific composition and ratio range, the prepared coated hard alloy cutter has excellent wear resistance, fracture toughness and intermittent cutting performance.

[0043] In some embodiments of the application, the thickness of the TiN coating is 1-3 μm, the thickness of the Al-rich surface layer is 0.8-1.5 μm, and the thickness of the TiAlN layer is 1.2-2.8 μm. The coating structure and cutter substrate structure within the above range and composition form a good bonding force between the coating and the cutter substrate, improving the overall performance of the coated hard alloy cutter.

[0044] In some embodiments of the application, the TiAlN layer is a gradient coating, and the Ti element gradually decreases and the Al element gradually increases in the direction of the TiN coating approaching the hard alloy cutter substrate. The gradient coating with the above structure is beneficial to avoid the formation of large lattice distortion between the coating and the cutter substrate, which leads to weakening of the bonding force.

[0045] In some embodiments of the present application, the TiN coating layer is columnar crystal structure, the cemented carbide tool substrate is equiaxed crystal structure, and the grain size of the equiaxed crystal structure is 100-800 nm, preferably, the grain size of the equiaxed crystal structure is 100-500 nm. The cemented carbide coating layer and tool substrate with the above structure are dense in structure and fine in grain, which is beneficial to improve the strength and toughness of the cemented carbide tool with the coating layer.

[0046] The present application provides a method for improving the intermittent cutting performance of a TiN-coated cemented carbide tool, which is used for preparing the aforementioned TiN-coated cemented carbide tool, and comprises the following steps:

[0047] (1) batching: weighing raw material powders according to mass ratio;

[0048] (2) mixing: uniformly mixing the raw material powders with a forming agent to obtain a mixed powder;

[0049] (3) compacting: compacting the mixed powder into a compact to obtain a compact body;

[0050] (4) sintering: sintering the compact body to prepare a cemented carbide tool substrate;

[0051] (5) coating: depositing a TiN coating layer on the surface of the cemented carbide tool substrate.

[0052] The preparation method of the present application is simple, has strong controllability, can be adapted to existing industrial equipment, and improves industrial applicability.

[0053] In some embodiments of the present application, in step (4), the specific process of sintering comprises: sintering the compact body at 300-650℃ for 1-3 h, sintering at 1100-1200℃ for 1-3 h, and sintering at 1400-1500℃ for 0.5-2 h.

[0054] In some embodiments of the present application, in step (5), the specific process of depositing the TiN coating layer comprises:

[0055] (5-1) performing surface micro-sand blasting treatment on the cemented carbide tool substrate;

[0056] (5-2) heating the cemented carbide tool substrate and performing Ar ion etching on the surface of the cemented carbide tool substrate;

[0057] (5-3) performing magnetron sputtering on the cemented carbide tool substrate to form a TiN coating layer.

[0058] The application activates the tool substrate surface by micro-sand blasting, heating and ion etching, and promotes the diffusion of the tool substrate AlN towards the substrate surface, so that the AlN further diffuses towards the coating in the subsequent magnetron sputtering process, and a specific coating structure and tool substrate structure and a bonding structure between the coating and the tool substrate are formed.

[0059] In some embodiments of the application, in step (5-1), the angle of micro-sand blasting is 30-60°, the sand blasting distance is 6-12 mm, the abrasive is 300-400 mesh corundum, and the sand blasting time is 20-50 s; and / or,

[0060] In step (5-2), the temperature for heating the cemented carbide tool substrate is 400-500℃; and / or,

[0061] The specific process for Ar ion etching the surface of the cemented carbide tool substrate is: etching pressure is 1×10 -1 ~ 3×10 -1 Pa, pulse bias voltage is -300V to -600V, air occupancy ratio is 60-85%, direct current bias voltage is -100 to -300V, and etching time is 5-20 min; and / or,

[0062] In step (5-3), the specific process of magnetron sputtering includes: introducing Ar gas with a flow rate of 60-80 sccm and N2 gas with a flow rate of 20-40 sccm into the vacuum chamber of the magnetron sputtering, keeping the total gas flow rate at 80-120 sccm, keeping the pressure of the vacuum chamber at 4.5±5×10 -1 Pa, the self-rotation speed of the cemented carbide tool substrate is 15-25 rev / min, the target current is 6.0-10A, and the deposition time is 120-180 min.

[0063] The TiN coating deposited on the surface of the cemented carbide tool substrate by using the specific process described above can improve the wear resistance and fracture toughness of the coated cemented carbide tool, and further improve the intermittent cutting performance of the coated cemented carbide tool.

[0064] The application will be described below with reference to specific examples, and it should be noted that these examples are merely descriptive and do not limit the application in any way.

[0065] The compositions of the raw material powders used in the examples and comparative examples are shown in Table 1, and the raw material powders are commercially available with a purity higher than 99.5wt.%, wherein the particle size of Co powder is 1.10μm, the particle size of WC powder is 6.02μm, the particle size of (W,Ti)C powder is 2.80μm, the particle size of Ni powder is 1.80μm, the particle size of AlN powder is 4.20μm, and the particle size of W powder is 2.00μm.

[0066] Table 1 Mass percentage (wt%) of each component of raw material powder in the examples and comparative examples

[0067] WC (W,Ti)C Co Ni AlN W Example 1 77.28 10 5 5 0.4 2.32 Example 2 77.28 10 5 5 0.8 1.92 Example 3 77.28 10 5 5 1.2 1.52 Example 4 77.28 10 5 5 1.6 1.12 Example 5 77.28 10 5 5 2.0 0.72 Comparative Example 1 77.28 10 5 5 0 2.72

[0068] The method for preparing the coated cemented carbide tool of examples 1-5 and comparative example 1 comprises the following steps:

[0069] (1) batching: raw material powder is weighed according to the mass ratio shown in Table 1.

[0070] (2) mixing: the weighed raw material powder is ball-mixed with a molding agent SD rubber. The addition amount of SD rubber powder is 4wt% based on the mass of raw material powder. The ball-milling time is 72h, the ball-milling speed is 56r / min, the ball-milling medium is anhydrous ethanol, the ball material is WC-6Co cemented carbide, and the ball-to-material ratio is 10:1. After ball-milling, the slurry is taken out, dried, and mixed powder is obtained.

[0071] (3) compacting: the mixed powder is compacted into a compact at 450MPa to obtain a compact body.

[0072] (4) sintering: the compact body is placed in a sintering furnace, sintered at 650℃ for 2h under a vacuum degree of 25Pa, then heated to 1150℃ for 2.5h, then vacuum sintered at 1410℃ for 0.5h, then Ar gas is filled, and the sintering is further carried out at 1420℃ for 1h under the condition of 5MPa Ar gas, to obtain a cemented carbide tool substrate.

[0073] (5) coating: the specific process for depositing a TiN coating on the surface of the prepared cemented carbide tool substrate comprises:

[0074] (5-1) the cemented carbide tool substrate is subjected to surface micro-blasting treatment, the blasting angle is 45°, the blasting distance is 8mm, the abrasive is 320 mesh corundum, the blasting time is 30s, then ultrasonic cleaning is carried out, the cleaning time is 20min, the vibration frequency is 40Hz, after cleaning, the treated cemented carbide tool substrate is dried;

[0075] (5-2) the cemented carbide tool substrate is heated, and the surface of the cemented carbide tool substrate is etched by Ar ions. Specifically, the cemented carbide tool substrate obtained in step (5-1) is placed in the vacuum chamber of a magnetron sputtering device, the vacuum chamber is evacuated, when the vacuum degree reaches 3.0×10 -3 Pa, the tool substrate is heated to 450℃ by using a heating wire, high-purity Ar gas (purity 99.999%) is introduced, and the surface of the cemented carbide tool substrate is etched by Ar ions: the etching pressure is 1.5×10 -1Pa, pulse bias-500V, duty ratio 80%, DC bias-200V, etching time 15min;

[0076] (5-3) Magnetron sputtering was used to form a TiN coating on the cemented carbide tool substrate. Specifically, the tool substrate was heated to 450℃, Ar and N2 were introduced into the vacuum chamber at flow rates of 75sccm and 35sccm respectively, the total gas flow rate was kept at 110sccm, and the pressure in the vacuum chamber was kept at 4.5±0.5×10 -1 Pa, the self-rotation speed of the cemented carbide tool substrate was 19.5 rev / min, the titanium target current was 8.0A, during the preparation of the coating, the hot cathode ion gun was continuously working to provide additional plasma for magnetron sputtering, and the whole process lasted for 150min, and a TiN coating was prepared on the surface of the tool substrate.

[0077] Structural analysis and performance testing

[0078] XRD test: XRD was used to analyze the crystal structure of the coated cemented carbide tool.

[0079] SEM test: Scanning electron microscopy and energy dispersive spectroscopy were used to test and analyze the morphology and composition of the coated cemented carbide tool.

[0080] Friction coefficient test: A surface tester was used to perform reciprocating friction experiments to test the friction coefficient of the coating.

[0081] Fracture toughness test: A nanoindenter was used to test the fracture toughness value of the coating.

[0082] Figure 1 XRD patterns of the coated cemented carbide tools of Examples 1-5 and Comparative Example 1, where a is Comparative Example 1, b is Example 1, c is Example 2, d is Example 3, e is Example 4, and f is Example 5.

[0083] As can be seen from Figure 1 , in the range of 20°-95°, WC phase, Co / Ni phase, and TiN phase were detected in the coated cemented carbide tool. The main diffraction peaks of the TiN phase correspond to (111), (200), and (220) crystal planes, among which (111) is the strongest peak, indicating that TiN has a preferred orientation along the (111) plane.

[0084] Figure 2 SEM images of the cross-sectional morphology of the coated cemented carbide tool, where a is Comparative Example 1, b is Example 1, c is Example 2, d is Example 3, e is Example 4, and f is Example 5. As can be seen from Figure 2 (a), there are obvious holes at the interface between the TiN coating and the tool substrate of Comparative Example 1. As can be seen from Figure 2As can be seen in (b), the TiN coating layer of Example 1 has a thickness of 1.3 μm, the TiN coating layer and the tool substrate are tightly combined, no obvious hole is observed at the interface, the crystal structure of the TiN coating layer is columnar crystal, and the crystal structure of the tool substrate is equiaxed crystal, but there are some coarse grains in Example 1, and the grain size of the equiaxed crystal structure is 100 nm to 1200 nm. From Figure 2 As can be seen in (c), the TiN coating layer of Example 2 has a thickness of 1.7 μm, local holes are observed at the combination of the TiN coating layer and the tool substrate, the crystal structure of the TiN coating layer is columnar crystal, and the crystal structure of the tool substrate is equiaxed crystal, the equiaxed crystal structure has fine and uniform grains, and the grain size is 100 nm to 500 nm. From Figure 2 As can be seen in (d), the TiN coating layer of Example 3 has a thickness of 1.8 μm, there is an obvious transition layer at the combination of the TiN coating layer and the tool substrate, the combination is tight, the crystal structure of the TiN coating layer is columnar crystal, and the crystal structure of the tool substrate is equiaxed crystal, the grain size of the equiaxed crystal structure is 100 nm to 800 nm, but the transition layer has the phenomenon of grain structure growth. From Figure 2 As can be seen in (e), the TiN coating layer of Example 4 has a thickness of 1.8 μm, there is an obvious transition layer at the combination of the TiN coating layer and the tool substrate, holes are observed between the transition layer and the tool substrate, the crystal structure of the TiN coating layer is columnar crystal, and the crystal structure of the tool substrate is equiaxed crystal, the grain size of the equiaxed crystal structure is 100 nm to 500 nm. From Figure 2 As can be seen in (f), the TiN coating layer of Example 5 has a thickness of 2.1 μm, the TiN coating layer and the tool substrate are tightly combined, the crystal structure of the TiN coating layer is columnar crystal, and the crystal structure of the tool substrate is equiaxed crystal, the grain size of the equiaxed crystal structure is 100 nm to 600 nm. With the increase of the amount of AlN in the tool substrate, the thickness of the TiN coating layer shows an increasing trend, and the main reason is that the AlN in the tool substrate promotes the deposition of TiN on the surface of the tool substrate.

[0085] Figure 3 Figure (f) is an element distribution diagram of the tool substrate and the coating layer interface of the coated cemented carbide tool of Example 3. From Figure 3As can be seen in the figure, an Al-rich surface layer is formed inside the cemented carbide tool substrate near the surface side, the thickness of the Al-rich surface layer is 1.2 μm, a TiAlN layer is formed near the side of the TiN coating layer close to the cemented carbide tool substrate, the thickness of the TiAlN layer is 1.5 μm, and in the direction close to the cemented carbide tool substrate of the TiN coating layer, the Ti element gradually decreases and the Al element gradually increases. The main reason for the analysis is that in the process of depositing the TiN coating layer on the surface of the tool substrate, the Al and N elements in the AlN diffuse to the surface, the Al element forms an Al-rich surface layer inside the tool substrate, and forms a TiAlN layer together with the Ti and N elements, which promotes the deposition of TiN on the tool substrate, and makes the coating and the tool substrate smoothly transition, reduces the internal stress caused by lattice distortion, and improves the bonding force between the coating and the tool substrate.

[0086] Figure 4 is the friction test curve of the coated cemented carbide tool, wherein a is Comparative Example 1, b is Example 1, c is Example 2, d is Example 3, e is Example 4, and f is Example 5.

[0087] Figure 4 The figure marks three stages of running-in period, transition period and stable wear period, wherein the stage before the vertical solid line is the running-in period, the stage between the vertical solid line and the vertical dashed line is the transition period, and the stage after the vertical dashed line is the stable wear period. The horizontal dashed line represents the average friction coefficient of the coating. According to the obtained curve, it can be seen that with the increase of the AlN content in the cemented carbide tool substrate, the friction coefficient of the surface TiN coating layer first increases, then decreases, and the decrease of the coating friction coefficient of Example 5 is more significant, which is only 0.17, as shown in Table 2.

[0088] Table 2 Friction coefficient of the coated cemented carbide tool of the examples and comparative examples

[0089] Test Specimen Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Coefficient of Friction 0.25 0.35 0.29 0.20 0.18 0.17

[0090] In addition, the friction curve also shows that compared with the coating of Comparative Example 1, the running-in period and the transition period of the coated cemented carbide tool of Examples 1-5 are shortened, that is, the initial wear stage is obviously shortened, and it can be considered that the addition of AlN in the tool substrate improves the wear resistance of the coated cemented carbide tool, and the wear resistance increases with the increase of AlN.

[0091] The fracture toughness of the coated cemented carbide tool of the examples and comparative examples is tested, and the results are shown in Table 3. According to Table 3, it can be seen that with the increase of the AlN content in the cemented carbide tool substrate, the fracture toughness of the coated cemented carbide tool first increases, then decreases, and then increases, and the increase of the fracture toughness of Example 5 is the most significant, which reaches 12.07 MPa·m -1 / 2 .

[0092] Table 3. Fracture toughness of coated cemented carbide cutting tools in the examples and comparative examples.

[0093]

[0094] Interrupted cutting (turning) tests were conducted using coated indexable tools. In the interrupted cutting tests, the coated carbide tool of Comparative Example 1 suffered brittle fracture after 6000 interrupted cuts, the coated carbide tool of Example 1 suffered brittle fracture after 9000 interrupted cuts, and the coated carbide tool of Example 2 suffered brittle fracture after 12000 interrupted cuts. However, the coated carbide tools of Examples 3-5 did not suffer brittle fracture after 12000 interrupted cuts. By selecting an appropriate AlN addition amount, the coated carbide tool can significantly improve the impact wear resistance, interrupted cutting behavior, and cutting life of the coated tool.

[0095] The flank morphology of the coated carbide tool in Comparative Example 1 under interrupted cutting impact was examined. The results are as follows: Figure 5 As shown, Figure 5 The image shows the tool face morphology after intermittent cutting impact of the coated carbide tool in Comparative Example 1. Figure 5 (a) 3000 times; Figure 5 (b) is 5000 times; Figure 5 (c) is 6000 times.

[0096] The TiN-coated tool in Comparative Example 1, after 3000 interrupted cutting impacts, showed the following performance: Figure 5 As shown in (a), comb-like scratches appear on the flank face, suggesting that in the early stages of interrupted cutting, hard particles in the hardened steel of the workpiece or built-up edge fragments adhering to the workpiece and chips etched grooves on the coated tool surface, leading to abrasive wear. After 5000 interrupted cutting impacts, as... Figure 5 As shown in (b), microcracks and minor peeling can be observed in some parts of the coating. It is speculated that at this stage, the tool adheres to the workpiece and chips. After the adhesion point tears, the coating on the tool surface is carried away, resulting in peeling and cracks. Further, as Figure 5 As shown in (c), after 6000 intermittent cutting impacts, obvious cold weld points have formed on the tool surface. Therefore, adhesive wear is more severe, and brittle fracture occurs.

[0097] The flank morphology of the coated insert in Example 3 under intermittent cutting impact was examined. The results are as follows: Figure 6 As shown, Figure 6 (a) 3000 times; Figure 6 (b) is 9000 times; Figure 6 (c) is 9500 times; Figure 6 (d) is 12,000 times.

[0098] The coated tool of Example 3 showed comb-like scratches and dot-like particles of cold-welding after 3000 intermittent cutting impacts, showing the characteristics of abrasive wear and adhesive wear. It is worth noting that the coating was severely worn after 3000 intermittent cutting impacts, compared to the higher number of intermittent cutting impacts of the flank surface morphology, which may be due to the uneven sandblasting during the pretreatment of the tool substrate coating, resulting in a large roughness near the cutting edge, and the coating in some areas is not tightly combined with the substrate, thus quickly worn under the extrusion of external force. After 6000 intermittent cutting impacts, the coating on the flank surface did not appear to peel off, which was in a normal wear state. After 9500 intermittent cutting impacts and 12000 intermittent cutting impacts, the abrasive wear of the coating tool flank surface was more serious, and there were more cold-welding substances in the morphology after 12000 intermittent cutting impacts, indicating that the adhesive wear was intensified, but brittle failure did not occur.

[0099] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, therefore: any equivalent changes made on the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for improving the interrupted cutting performance of a TiN-coated cemented carbide tool for the manufacture of TiN-coated cemented carbide tools, c h a r a c t e r i s e d in that, The method comprises the following steps: (1) batching: weighing raw material powders according to mass proportions; the raw material components of the hard alloy cutter base body include (W, Ti)C: 8-20%, Co: 3-10%, Ni: 3-10%, AlN: 0.8-2.5%, W: 0.3-2.5%, and the balance is WC, in terms of mass percentage of the hard alloy cutter base body; (2) mixing: uniformly mixing the raw material powders with a forming agent to obtain mixed powders; (3) compacting: compacting the mixed powders into a compact to obtain a compact body; (4) sintering: sintering the compact body to prepare the hard alloy cutter base body; the specific process of sintering includes: sintering at 650 DEG C for 2h under a vacuum degree of 25Pa, then sintering at 1150 DEG C for 2.5h, then vacuum sintering at 1410 DEG C for 0.5h, then filling Ar gas, and then sintering at 1420 DEG C for 1h under the condition of Ar gas at 5MPa, to prepare the hard alloy cutter base body; (5) coating: depositing a TiN coating on the surface of the hard alloy cutter base body; The TiN coating hard alloy cutter comprises a hard alloy cutter base body and a TiN coating deposited on the surface of the hard alloy cutter base body, an Al-rich surface layer is formed on the side of the hard alloy cutter base body close to the surface, and a TiAlN layer is formed on the side of the TiN coating close to the hard alloy cutter base body. The TiN coating is columnar crystal structure, the hard alloy cutter base body is equiaxed crystal structure, and the grain size of the equiaxed crystal structure is 100-800nm.

2. The method of improving the interrupted cutting performance of TiN coated cemented carbide tools according to claim 1, characterized in that, The thickness of the TiN coating is 1-3μm, the thickness of the Al-rich surface layer is 0.8-1.5μm, and the thickness of the TiAlN layer is 1.2-2.8μm.

3. The method of improving the interrupted cutting performance of TiN coated cemented carbide tools according to claim 1, characterized in that, The TiAlN layer is a gradient coating, and Ti element gradually decreases and Al element gradually increases in the direction close to the hard alloy cutter base body of the TiN coating.

4. The method of improving the interrupted cutting performance of TiN coated cemented carbide tools according to claim 1, characterized in that, The raw material components of the hard alloy cutter base body include (W, Ti)C: 8-13%, Co: 4-6%, Ni: 4-6%, AlN: 2.0-2.5%, W: 0.3-0.8%, and the balance is WC, in terms of mass percentage of the hard alloy cutter base body.

5. The method of improving the interrupted cutting performance of TiN coated cemented carbide tools according to claim 1, characterized in that, In step (5), the specific process of depositing the TiN coating includes: (5-1) performing surface micro-sand blasting treatment on the hard alloy cutter base body; (5-2) heating the hard alloy cutter base body and performing Ar ion etching on the surface of the hard alloy cutter base body; (5-3) performing magnetron sputtering on the hard alloy cutter base body to form a TiN coating.

Images