A coating with enhanced toughness and wear resistance and a method of making and using the same

Abstract

The present application relates to a coating with enhanced toughness and wear resistance, and its preparation method and application, comprising a Co-containing hard substrate and a hard coating coated on the substrate; the hard coating comprises a layer of ultra-fine, nanocrystalline Ti(C x N y O z ) coating with a thickness >1 μm prepared by a chemical vapor deposition method, wherein x+y+z=1, 0.5≤x≤0.7, 0.3≤y≤0.5, and 0 The present application can effectively improve the problems of weak grain boundary strength caused by enrichment of chlorine impurities at the grain boundary and the problem of toughness reduction of the coating caused by oxygen element doping hardening. The coating of the present application has high hardness, and also has relatively high toughness and grain boundary strength, and can greatly improve the anti-collapse and anti-chip ability, wear resistance and service life when used as a metal cutting tool.

Description

Technical Field

[0001] This invention relates to a chemical vapor deposition coating cutting tool for metal processing and its preparation method, particularly to a Ti(C)-containing coating with enhanced toughness and wear resistance. x N y O z Chemical vapor deposition coated cutting tools, their preparation methods and applications, fall under the category of cutting tools made of hard materials and hard coatings. Technical Background

[0002] Coating the surface of hard material substrates, including cemented carbide and cermet, can significantly improve the wear resistance, corrosion resistance, chemical stability, and high-temperature performance of cemented carbide cutting tools. Commonly used industrial coating methods include physical vapor deposition (PVD) and chemical vapor deposition (CVD). Commercially available CVD-coated cemented carbide tool surfaces typically have a TiN / TiCN / TiAlOCN / α-Al2O3 / TiN composite structure, with the TiCN coating usually prepared using a medium-temperature chemical vapor deposition method (MT-TiCN).

[0003] Compared with high-temperature chemical vapor deposition TiCN (HT-TiCN) coatings, MT-TiCN coatings have a lower deposition temperature, which can suppress the generation of decarburized phases at the coating-substrate interface and help reduce the damage to the toughness of the substrate caused by CVD coatings. They are widely used in the industrial production of coated cutting tools.

[0004] MT-TiCN coating, as an important functional layer, exhibits excellent resistance to flank wear. However, MT-TiCN coatings typically consist of coarse columnar crystals with relatively low hardness. However, its wear resistance can be further improved by reducing the grain size through alloying element doping or increasing the carbon content to increase hardness. Material hardness increases with decreasing alloy grain size, and increasing material hardness is beneficial for improving wear resistance.

[0005] Patent CN100549222C provides a method for controlling the grain size and microstructure of an MT-TiCN coating. This invention achieves a nanocrystalline-level fine equiaxed grain structure in the MT-TiCN coating by doping with CO, CO2, ZrCl4, or AlCl3. The resulting MT-TiCN coating exhibits higher wear resistance, making it particularly suitable for machining ductile metals such as stainless steel.

[0006] Patent CN101688311A discloses a TiCN coating doped with chromium, vanadium, or silicon. This invention regulates the content of doping elements within the coating by introducing and controlling the partial pressure of CrCl2, VCl3, or SiCl4 during the TiCN deposition process. The coated cutting tools of this invention exhibit improved wear resistance and longer cutting life in the machining of steel, cast iron, and stainless steel.

[0007] Patent CN103506640B discloses a TiBCN-coated cutting tool with a boron content between 0.5 at% and 10 at% prepared by CVD method, and its preparation method. This invention patent incorporates BCl3 gas during the MT-TiCN coating deposition process, thereby incorporating boron into the MT-TiCN coating, significantly improving the coating's hardness and wear resistance, and resulting in superior cutting performance for the coated tool.

[0008] Patent CN104099580A discloses a nano-columnar crystal tool coating with enhanced wear resistance and toughness. This method involves controlling the combination and ratio of CH4, C2H6, C2H4, C2H2, N2, and CH3CN in chemical vapor deposition to prepare nano-columnar MT-TiCN with a grain size of 50–150 nm. This coating significantly improves the wear resistance and impact resistance of cutting tools, exhibiting excellent performance in cutting materials such as steel, cast iron, and stainless steel.

[0009] The paper "Atom probe tomography investigations on grain boundary segregation in polycrystalline Ti(C,N) and Zr(C,N) CVD coatings" (Azhari et al. ScriptaMaterialia, 162(2019) 335–340) reports the grain boundary composition of polycrystalline TiCN coatings deposited on WC-Co cemented carbide substrates by intermediate-temperature chemical vapor deposition. Atom probe analysis results indicate that the aggregation of Cl impurities at the grain boundaries is an intrinsic defect of the MT-CVD TiCN coating, which weakens its grain boundary strength.

[0010] By comparing with existing technologies, the following conclusions can be drawn: By rationally controlling the composition of the CVD mixed gas, the grain size of the MT-TiCN coating can be significantly reduced, thereby significantly improving its hardness and wear resistance. However, the increase in coating hardness easily leads to a decrease in coating toughness, making it prone to chipping or micro-chipping during cutting, resulting in premature failure of the coated tool. Furthermore, existing inventions cannot eliminate a series of problems caused by the segregation of Cl elements at the grain boundaries of the MT-TiCN coating, such as weakened grain boundary strength, decreased coating cohesion, and increased coating brittleness. Summary of the Invention

[0011] In view of the shortcomings of the prior art, the main purpose of this invention is to solve the problems of low grain boundary bonding strength of MT-TiCNCVD coating and decreased toughness after the coating hardness is increased by oxygen doping.

[0012] This invention discloses a coating with enhanced toughness and wear resistance. The coating with enhanced toughness and wear resistance refers to a hard coating applied to a substrate, wherein the substrate is a Co-containing hard substrate. The hard coating comprises a Ti(C) layer deposited using a CVD method, with a thickness >1 μm. x N y O z The coating has the following properties: x + y + z = 1, 0.5 ≤ x ≤ 0.7, 0.3 ≤ y ≤ 0.5, 0 < z ≤ 0.2. A matrix binder metal with a concentration > 1.0 at.% is distributed at the grain boundaries of the coating. The so-called hard coating has high toughness and wear resistance, and its surface roughness Ra < 0.7 μm. The Co-containing hard matrix refers to Co-containing cemented carbide and Co-containing cermet. The matrix binder metal refers to Co, or Co and Ni, in the Co-containing hard matrix. CVD refers to chemical vapor deposition. at.% refers to atomic percentage. The Co-containing cemented carbide refers to cemented carbide whose binder metal contains Co. Cemented carbide used as a coating matrix typically uses a single metallic Co as the binder metal. The Co-containing cermet refers to cermet whose binder metal contains Co. Ceramic typically uses both Co and Ni as binder metals.

[0013] This invention discloses a coating with enhanced toughness and wear resistance. After coating deposition, the coating undergoes heat treatment to diffuse the binder metal in the substrate to the coating grain boundaries. The post-deposition heat treatment can be carried out in a CVD coating furnace in a pure H2 atmosphere after coating deposition, or it can be carried out in a vacuum or inert atmosphere after the coating is removed from the furnace. The post-deposition heat treatment temperature is lower than the liquid phase appearance temperature in the Co-containing hard substrate, which is 1000-1100℃, and the heat treatment holding time is 200-400 min. Whether it is a Co-containing hard alloy or a Co-containing cermet, the liquid phase appearance temperature in its alloy system is higher than 1100℃, and usually higher than 1280℃.

[0014] This invention discloses a coating with enhanced toughness and wear resistance, wherein the total thickness of the coating is 5–30 μm; the coating consists of 5 layers distributed sequentially outward from the substrate, the first layer being TiN, TiC, or TiCN, preferably TiN, with a thickness of 0.1–2 μm; the second layer being Ti(C)... x N y O zThe first layer is TiAlOCN with a thickness of 2–15 μm; the second layer is TiAlOCN with a thickness of 0.1–1 μm; the third layer is α-Al2O3 with a thickness of 2–15 μm; and the fourth layer is a top TiN coloring layer with a thickness of 0.1–2 μm.

[0015] This invention discloses a coating with enhanced toughness and wear resistance, wherein the second layer is Ti(C) x N y O z The coating is made of ultrafine nanocrystals with an average grain size of <0.2μm.

[0016] This invention discloses a method for preparing a coating with enhanced toughness and wear resistance. The coating with enhanced toughness and wear resistance refers to a hard coating applied to a substrate; the substrate refers to a Co-containing hard substrate; the hard coating comprises a Ti(C) layer deposited using a CVD method, with a thickness >1 μm. x N y O z A coating, wherein x + y + z = 1, 0.5 ≤ x ≤ 0.7, 0.3 ≤ y ≤ 0.5, 0 < z ≤ 0.2, is characterized by a matrix binder metal with a concentration > 1.0 at.% distributed at the grain boundaries of the coating; the Co-containing hard matrix refers to Co-containing cemented carbide and Co-containing cermet; the matrix binder metal refers to Co, or Co and Ni in the Co-containing hard matrix; the CVD refers to chemical vapor deposition; after coating deposition, the coating is subjected to heat treatment to diffuse the binder metal in the matrix to the coating grain boundaries; the heat treatment after coating deposition... The heat treatment can be carried out in a CVD coating furnace under a pure H2 atmosphere after coating deposition, or it can be carried out in a vacuum or inert atmosphere after the coating is removed from the furnace. The heat treatment temperature after coating deposition is lower than the liquid phase appearance temperature in the Co-containing hard substrate, which is 1000-1100℃, and the heat treatment holding time is 200-400 min. The total thickness of the coating is 5-30 μm. The coating consists of 5 layers distributed outward from the substrate. The first layer is TiN, TiC, or TiCN, preferably TiN, with a thickness of 0.1-2 μm. The second layer is Ti(C) x N y O z The first layer is Ti(C) with a thickness of 2–15 μm; the second layer is TiAlOCN with a thickness of 0.1–1 μm; the third layer is α-Al₂O₃ with a thickness of 2–15 μm; the fourth layer is a top TiN coloring layer with a thickness of 0.1–2 μm; the fifth layer is a TiN coloring layer with a thickness of 0.1–2 μm. x N y O zThe coating is made of ultrafine, nanocrystalline material with an average grain size of <0.2μm. The coating undergoes surface mechanical treatment before leaving the factory. The surface mechanical treatment refers to treating the coating surface with wet sandblasting and polishing in sequence, so that the surface roughness Ra of the coating is <0.7μm.

[0017] This invention discloses a method for preparing a coating with enhanced toughness and wear resistance. The TiN coating is prepared by chemical reaction using TiCl4, N2, and H2 as precursors at 900–1000℃ and 100–400 mbar. In industrial applications, if both the first and fifth layers are TiN layers, the above-described TiN layer preparation method can be used. When the first layer is made of other materials, existing methods can also be used.

[0018] This invention discloses a method for preparing a coating with enhanced toughness and wear resistance, wherein the Ti(C) coating... x N y O z The second coating, also known as the Ti(C) coating, is prepared by a chemical reaction using a mixture of TiCl4, N2, CO, H2, and CH3CN as precursors at 800–900 °C and 50–200 mbar. x N y O z The O content in the coating is controlled by the volume fraction of CO in the mixed gas; the Ti(C) coating... x N y O z The ultrafine and nano-sized coating grains are achieved by increasing the volume fraction of CO in the mixed gas; the volume fraction of CO in the mixed gas is greater than 2% but less than 8%; the increase in the volume fraction of CO in the mixed gas is achieved by reducing the volume fraction of carrier gas H2 in the mixed gas.

[0019] This invention discloses a method for preparing a coating with enhanced toughness and wear resistance. The TiAlOCN coating is prepared by chemical reaction using a mixed gas of TiCl4, N2, H2, CH4, CO, CO2 and AlCl3 as a precursor under conditions of 900–1000℃ and 50–200 mbar.

[0020] This invention discloses a method for preparing a coating with enhanced toughness and wear resistance. The Al2O3 coating is prepared by chemical reaction using a mixed gas of H2, AlCl3 and CO2 as a precursor and H2S as a catalyst at 900–1000℃ and 100–250 mbar.

[0021] The thickness of each layer in the coating of this invention can be controlled by the coating deposition time.

[0022] This invention relates to an application of a coating with enhanced toughness and wear resistance, wherein the coating is used as a metalworking cutting tool; the coated insert used as a metalworking cutting tool undergoes surface mechanical treatment before leaving the factory; the surface mechanical treatment refers to treating the coating surface by wet sandblasting and polishing successively, so that the surface roughness Ra of the coating is <0.7μm.

[0023] The mechanism and advantages of this invention are briefly described below:

[0024] By adjusting the volume fraction of CO (carbon monoxide) in the mixed gas, ultrafine, nanocrystalline Ti(C) was obtained. x N y O z This improves the coating's hardness and wear resistance. Through systematic experimental research, this invention has found that controlling the volume fraction of CO in the mixed gas to be greater than 2% but less than 8% results in the formation of ultrafine, nanocrystalline Ti(C) coatings. x N y O z The coating exhibits the best overall performance; within this range, increasing the CO concentration can improve the overall performance of Ti(C) coating. x N y O z The coating grain size is effectively reduced and nano-sized.

[0025] By means of Ti(C) in a pure H2 atmosphere, an inert atmosphere, or a vacuum, under conditions below the liquid phase appearance temperature in a Co-containing hard matrix. x N y O z The ultrafine, nanocrystalline properties of the coating (average grain size <0.2 μm) and its driving effect on the migration of Co or Co and Ni binder metals in Co-containing hard substrates, as well as its regulatory effect on the migration paths of Co and Ni binder metals, enable the slow and orderly migration and diffusion of solid binder metal atoms in the substrate along the coating growth direction. These atoms are then uniformly distributed at the grain boundaries of each coating layer in the form of an atomically thin film, thereby improving the intergranular bonding strength, toughness, and resistance to cohesive failure. Improving the grain boundary bonding strength enhances the coating's cohesiveness and substrate adhesion, reduces its brittleness, and thus improves the resistance of coated tools to chipping and breakage. However, excessively high heat treatment temperatures or prolonged holding times after coating deposition can easily lead to uncontrolled migration and diffusion of the binder metal, resulting in coating defects. Through systematic experimental research, this invention has found that a heat treatment temperature of 1000–1100℃ and a holding time of 200–400 min after coating deposition can enable coated cutting tools to obtain the best comprehensive performance. Under these process conditions, the migration amount and distribution of the binder metal that migrates from the substrate to the coating can reach the optimal conditions required to optimize the comprehensive performance of the coated cutting tools.

[0026] In summary, this invention effectively improves the problems of reduced grain boundary strength, interlayer bonding strength, coating cohesion, and coating toughness caused by the enrichment of chlorine impurities at grain boundaries in coatings prepared by in-situ chemical vapor deposition reactions involving chlorides such as TiCl4 and AlCl3, including MT-Ti(C,N,O) coatings, as well as the problem of decreased coating toughness caused by increased coating hardness after oxygen doping. Therefore, it can effectively improve coating toughness, coating cohesive failure resistance, and film-substrate adhesion, reduce chipping (micro-chipping) and edge breakage during the service of coated tools, and improve coating wear resistance, service life, and service performance stability of coated tools.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the coating with enhanced toughness and wear resistance, its preparation method, and its application are not limited to the embodiments. The evaluation method for the toughness and wear resistance of the coated cutting tool adopts the comprehensive evaluation of anti-chipping ability (performance) and cutting life, which are commonly used in the field of cutting tools. Attached Figure Description

[0028] Figure 1 The images show scanning electron microscope (SEM) images (a) of the micro-region containing MT-Ti(C,N,O) in the cross-section of the coating of the untreated comparative sample B, and energy dispersive spectroscopy (EDS) analysis results of the area marked by the box in the figure (b).

[0029] Figure 2 The images show scanning electron microscope (SEM) images (a) of the micro-region containing MT-Ti(C,N,O) in the coating cross section of sample A after heat treatment and energy dispersive spectroscopy (EDS) analysis results (b) of the area marked by the box in the figure.

[0030] from Figure 1 and Figure 2 It can be seen that trace amounts of Cl impurities exist in the MT-Ti(C,N,O) layer of the untreated comparative sample B, but no Co elements were detected. The grain boundaries of the MT-Ti(C,N,O) layer of the treated sample A exhibit white lines due to the presence of Co elements diffused from the matrix to the coating. At the same time, the energy dispersive spectroscopy analysis results also show that the coating contains 1.39% Co elements in atomic fraction. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments, comparative examples and accompanying drawings.

[0032] Example 1

[0033] Five layers of coating were applied to a cemented carbide indexable insert (CNMG120408E, turning tool) using CVD technology. The cemented carbide composition included 7% Co (mass fraction, the same below), 3.5% cubic carbide, and the balance WC. The five layers were approximately 16.5 μm thick and consisted of TiN (approximately 0.5 μm), MT-TiCNO (approximately 8 μm), TiAlOCN (approximately 0.5 μm), α-Al₂O₃ (approximately 7 μm), and TiN (approximately 0.5 μm). Three samples were designated as Sample A, Sample B (Comparative Sample 1), and Sample C (Comparative Sample 2). The coating processes for all three samples were identical, as shown in Table 1.

[0034] Table 1 Process parameters for coating deposition

[0035]

[0036] The difference lies in the following: After coating deposition, sample A undergoes heat treatment in a CVD coating furnace at 1100℃ for 200 min in a pure H2 atmosphere (post-coating in-situ heat treatment); sample B undergoes no heat treatment after coating deposition and proceeds directly to the cooling stage. Sample C undergoes heat treatment in a vacuum furnace at 1130℃ for 500 min after coating deposition and cooling. Figure 1 These are scanning electron microscope (SEM) images of the micro-region containing the MT-Ti(C,N,O) coating in sample B (without post-coating heat treatment) and energy dispersive spectroscopy (EDS) analysis results of the area marked by the box in the image. Figure 1 It can be seen that trace amounts of Cl impurities exist in the MT-Ti(C,N,O) coating, but no Co elements were detected. Figure 2 These are scanning electron microscope (SEM) images of the micro-region containing MT-Ti(C,N,O) in the coating of sample A (which underwent heat treatment after coating deposition), and energy dispersive spectroscopy (EDS) analysis results of the area marked by the box in the image. From Figure 2 The scanning electron backscattering (SEM) image shows that the grain boundaries of the coating appear as white lines due to the diffusion of Co elements from the substrate to the coating. Energy dispersive spectroscopy (EDS) analysis indicates that the coating contains 1.39% Co atomically. Based on X-ray diffraction (XRD) analysis of the polished cross-sections of samples A and B, calculations using the Scherrer formula show that the average grain size of the prepared MT-Ti(C,N,O) coating is 50 nm. Figure 1 The energy dispersive spectroscopy (EDS) analysis results for sample b show that the atomic fractions of C, N, and O in the MT-Ti(C,N,O) surface of sample B are 0.55, 0.33, and 0.12, respectively. From... Figure 2 According to the energy dispersive spectroscopy analysis results of b, the atomic fractions of C, N, and O in MT-Ti(C,N,O) on the surface of sample A are 0.52, 0.35, and 0.13, respectively.

[0037] A comparative cutting experiment was conducted on samples A, B, and C from Example 1 by turning the steel parts. Five cutting tools were tested for each of the three groups of samples. Before the cutting experiment, the coating surface was treated with wet sandblasting and polishing, and the surface roughness Ra was measured to be 0.15 μm. The cutting experiment parameters are as follows:

[0038] Operation: Continuous turning

[0039] Workpiece shape: Cylindrical part;

[0040] Materials: 45 # Carbon steel;

[0041] Blade type: CNMG 120408E;

[0042] Cutting speed: 300 m / min;

[0043] Feed rate: 0.3 mm / rev;

[0044] Depth of cut: 2.0 mm;

[0045] Cutting method: wet cutting

[0046] Turning test results showed that in Comparative Sample B, one sample exhibited chipping after 14 minutes of cutting. The other four samples all showed coating tool failure due to micro-chipping or chipping after 18 minutes of cutting. In Comparative Sample C, coating tool failure due to micro-chipping or chipping was observed after 9 minutes of cutting. The measurement results of the flank wear VB (unit: mm) for the three types of inserts are shown in Table 2. The flank wear VB of Comparative Sample B after 14 minutes of cutting is the average measurement result of the four samples.

[0047] Table 2. Rake face wear of turning inserts, mm

[0048] Sample number 4 minutes 9 minutes 14 minutes 18 minutes Sample A 0.04 0.07 0.12 0.30 Sample B (Comparative Sample 1) 0.05 0.12 0.29 Failure Sample C (Comparative Sample 2) 0.09 Failure

[0049] As shown in Table 2, this invention significantly improves the wear resistance, chipping resistance, and anti-scratching ability of the coated cutting tools. Clearly, the improved wear resistance is closely related to the increased hardness resulting from the nano-structure effect of the MT-Ti(C,N,O) coating; the improved chipping resistance and anti-scratching ability are closely related to the improved coating toughness. It is worth noting that excessive heat treatment can lead to premature tool failure.

[0050] To more authoritatively and professionally characterize the toughness of coated cutting inserts, this invention conducted impact toughness tests on samples A and B in Example 1, following a common method for evaluating the impact toughness of cutting inserts in the field of cutting tools. The test method involved end-face turning of a round bar with four symmetrical grooves. The insert was considered to have failed when it chipped or broke. The impact toughness of the insert was evaluated by the number of grooves it had cut, i.e., the number of impacts it could withstand. Since sample C's resistance to chipping was significantly lower than that of samples A and B, impact toughness tests were not performed on sample C.

[0051] The cutting experiment parameters are as follows:

[0052] Operation: Intermittent turning

[0053] Workpiece shape: Grooved cylindrical part

[0054] Materials: 45 # carbon steel

[0055] Blade type: CNMG 120408E

[0056] Cutting speed: 270 m / min

[0057] Feed rate: 0.18 mm / rev

[0058] Cut depth: 1.5mm

[0059] Cutting method: Dry cutting

[0060] Table 3. Number of impacts subjected to by turning inserts (in seconds)

[0061] Sample number Group 1 Group 2 Group 3 Group 4 Sample A 4090 4856 4538 4672 Sample B (Control Sample) 3568 2627 3153 3866

[0062] As shown in Table 3, even when subjected to repeated mechanical and thermal shocks during cutting, sample A, after heat treatment following coating deposition, did not experience coating damage or peeling, significantly improving the cutting tool's resistance to chipping and spalling. Clearly, this improvement in resistance to chipping and spalling is closely related to the improvement in coating toughness.

[0063] Example 2

[0064] Five layers of coating were applied to a TiCN-based cermet indexable cutting tool (CNMG120408E, turning tool) using CVD technology. The TiCN-based cermet composition includes: 7.5% Co (mass fraction), 7.5% Ni, 20% WC, 5% Mo2C, 3% TaC, 3% NbC, and the balance TiC. 0.5 N 0.5The total thickness of the 5-layer coating is approximately 13.5 μm, consisting of TiN (approximately 0.5 μm), MT-Ti(C,N,O) (approximately 8 μm), TiAlOCN (approximately 0.5 μm), α-Al₂O₃ (approximately 4 μm), and TiN (approximately 0.5 μm). Two samples are designated as Sample D and Sample E (comparison sample). The coating processes for both samples are identical. The reactive gas composition, deposition pressure, and temperature are as shown in Table 1; only the deposition time was adjusted to change the coating thickness. After coating deposition, Sample D underwent heat treatment at 1050 °C for 240 min in a vacuum furnace; Sample E did not undergo heat treatment after coating deposition. Micro-area composition analysis of the heat-treated coatings was performed according to the measurement method described in Example 1. The results showed that the average atomic percentages of Co and Ni in the coating of Sample D were 0.71% and 0.64%, respectively, with a total average atomic percentage of 1.35%.

[0065] A comparative cutting experiment was conducted on samples D and E of Example 2 by turning cast iron. Five cutting inserts were tested in each group. Before the cutting experiment, the coating surface was treated with wet sandblasting and polishing. The surface roughness Ra of the coating was measured to be 0.15 μm. The cutting experiment parameters are as follows:

[0066] Operation: Continuous turning

[0067] Workpiece shape: Cylindrical part

[0068] Material: Gray cast iron

[0069] Blade type: CNMG 120408E

[0070] Cutting speed: 350m / min

[0071] Feed rate: 0.3 mm / rev

[0072] Depth of cut: 1.8mm

[0073] Cutting method: Dry cutting

[0074] Turning tests showed that, in Comparative Sample E, the flank wear of all four specimens exceeded 0.3 mm after 24 minutes of cutting, indicating failure. One specimen exhibited coating tool failure due to chipping after 24 minutes of cutting. The flank wear VB (in mm) measurements for both types of inserts are shown in Table 4. The flank wear VB of Comparative Sample E after 18 minutes of cutting is the average measurement of the four specimens, as one specimen already showed micro-chipping. The failure mode of Comparative Sample E after 24 minutes of cutting was flank wear exceeding 0.3 mm and chipping. The failure criterion of 0.3 mm flank wear is a commonly used industry standard.

[0075] Table 4. Rake face wear of turning inserts, mm

[0076] Sample number 6 minutes 12 minutes 18 minutes 24 minutes 32 minutes Sample D 0.08 0.14 0.20 0.25 0.30 Sample E (Comparison Sample) 0.12 0.19 0.28 Failure

[0077] As shown in Table 4, the present invention significantly improves the wear resistance of coated cutting tools.

[0078] Example 3

[0079] Five layers of coating were applied to a carbide indexable insert (SNGX1206ANN, end mill) using CVD technology. The carbide composition included 10% Co (mass fraction, the same below), 1.5% (Ti,Ta,Nb)C, and the balance WC. The total thickness of the five coating layers was approximately 6.5 μm, consisting of TiN (approximately 0.5 μm), MT-Ti(C,N,O) (approximately 2.2 μm), TiAlOCN (approximately 0.5 μm), α-Al₂O₃ (approximately 3.0 μm), and TiN (approximately 0.3 μm). Two samples were designated as Sample F and Sample G (Comparative Sample 1), respectively. The coating processes for both samples were identical. The reactive gas composition, deposition pressure, and temperature are shown in Table 1; only the deposition time was adjusted to change the coating thickness. After the coating was deposited and removed from the furnace, sample F was heat-treated in a tube furnace at 1000℃ for 400 min in high-purity Ar gas; sample G was not heat-treated after coating deposition.

[0080] A comparative cutting experiment was conducted on samples F and G of Example 3 by milling the steel parts. Five cutting tools were tested in each group. Before the cutting experiment, the coating surface was treated with wet sandblasting and polishing. The surface roughness Ra of the coating was measured to be 0.15 μm. The cutting experiment parameters are as follows:

[0081] Operation: Face milling

[0082] Workpiece shape: block part

[0083] Material: Alloy steel

[0084] Blade type: SNGX1206ANN

[0085] Milling speed: 200m / min

[0086] Milling feed rate: 0.2 mm / z

[0087] Milling depth of cut: 1mm

[0088] Milling width: 60mm

[0089] Cutting method: Dry cutting

[0090] The measurement results of the blade flank wear VB (unit: mm) are shown in Table 5. Comparative sample G showed varying degrees of chipping or edge breakage leading to coated tool failure after cutting time exceeding 16 minutes.

[0091] Table 5. Rake face wear of milling inserts, mm

[0092] Sample number 4 minutes 10 minutes 16 minutes 22 minutes Sample F 0.04 0.14 0.20 0.29 Sample G (Comparative Sample 1) 0.06 0.18 0.28 Failure

[0093] As can be seen from Table 5 above, the coated cutting insert of the present invention improves the chipping resistance and wear resistance of the cutting tool.

[0094] Compared with existing technologies, the cutting tools of this invention significantly improve tool life for both turning and milling operations.

[0095] The above embodiments are only used to further illustrate a coating with enhanced toughness and wear resistance, its preparation method and application, but the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A coating having enhanced toughness and wear resistance, characterized by: The coating with enhanced toughness and wear resistance refers to a hard coating coated on a substrate, wherein the substrate refers to a Co-containing hard substrate; the hard coating comprises a Ti(C x N y O z ) coating deposited by a CVD method, wherein x+y+z=1, 0.5≤x≤0.7, 0.3≤y≤0.5, and 0 The hard coating has a surface roughness Ra<0.7 μm; the Co-containing hard substrate refers to a Co-containing cemented carbide and a Co-containing cermet; the substrate binder metal refers to Co, or Co and Ni in the Co-containing hard substrate; the CVD refers to chemical vapor deposition; and the at.% refers to atomic percentage. The total thickness of the coating is 5-30μm; the coating is distributed by the substrate in turn outwardly 5 layers, the first layer is TiN or TiC or TiCN, the thickness is 0.1-2μm; the second layer is Ti(C x N y O z ), the thickness is 2-15μm; the third layer is TiAlOCN, the thickness is 0.1-1μm; the fourth layer is α-Al2O3, the thickness is 2-15μm; the fifth layer is the top layer TiN coloring layer with the thickness of 0.1-2μm; The Ti(C x N y O z ) coating is ultrafine, nanocrystalline, with an average grain size of <0.2 μm. The Ti(C) x N y O z The coating was prepared by chemical reaction using a mixture of TiCl4, N2, CO, H2, and CH3CN as precursors at 800–900 °C and 50–200 mbar; the Ti(C) coating was prepared by chemical reaction. x N y O z The O content in the coating is controlled by the volume fraction of CO in the mixed gas; the Ti(C) coating... x N y O z The ultrafine and nano-sized coating grains are achieved by increasing the volume fraction of CO in the mixed gas; the volume fraction of CO in the mixed gas is 5%; the increase in the volume fraction of CO in the mixed gas is achieved by reducing the volume fraction of the carrier gas H2 in the mixed gas. The coating is subjected to heat treatment after coating deposition to diffuse the binder metal in the substrate to the coating grain boundary; the heat treatment after coating deposition is carried out in a pure H2 atmosphere in a CVD coating furnace after coating deposition, or in a vacuum or inert atmosphere after the coating is discharged from the furnace; the heat treatment after coating deposition is at a temperature lower than the liquid phase appearance temperature of the Co-containing hard substrate, at 1000-1100℃, and the heat treatment holding time is 200-400min; The TiAlOCN coating is prepared by chemical reaction at 900-1000℃ and 50-200mbar, using TiCl4, N2, H2, CH4, CO, CO2 and AlCl3 mixed gas as the precursor. The Al2O3 coating is prepared by chemical reaction at 900-1000℃ and 100-250mbar, using H2, AlCl3 and CO2 mixed gas as the precursor, and H2S as the catalyst.

2. The coating with enhanced toughness and wear resistance according to claim 1, characterized in that: The first layer is TiN.

3. A method of producing a coating having enhanced toughness and wear resistance, characterized by: The coating with enhanced toughness and wear resistance refers to a hard coating coated on a substrate; the substrate refers to a Co-containing hard substrate; the hard coating comprises a Ti(C x N y O z ) coating layer deposited by a CVD method, with a thickness > 1 μm, wherein x+y+z=1, 0.5≤x≤0.7, 0.3≤y≤0.5, 0 z≤0.

2. The Co-containing hard substrate refers to Co-containing cemented carbide and Co-containing cermet; the binder metal in the substrate refers to Co, or Co and Ni in the Co-containing hard substrate; the CVD refers to chemical vapor deposition; The coating is subjected to heat treatment after coating deposition to diffuse the binder metal in the substrate to the coating grain boundary, and the binder metal in the substrate is distributed at the coating grain boundary at a concentration >1.0at.%; The heat treatment after coating deposition can be carried out in a pure H2 atmosphere in a CVD coating furnace after coating deposition, or in a vacuum or inert atmosphere after the coating is discharged from the furnace; the heat treatment after coating deposition is at a temperature lower than the liquid phase appearance temperature of the Co-containing hard substrate, at 1000-1100℃, and the heat treatment holding time is 200-400min; The total thickness of the coating is 5-30μm; the coating is distributed by the base body in turn to the outside 5 layers, the first layer is TiN or TiC or TiCN, the thickness is 0.1-2μm; the second layer is Ti(C x N y O z ), the thickness is 2-15μm; the third layer is TiAlOCN, the thickness is 0.1-1μm; the fourth layer is α-Al2O3, the thickness is 2-15μm; the fifth layer is the top layer TiN coloring layer, the thickness is 0.1-2μm; the second layer Ti(C x N y O z ) coating is superfine, nanocrystalline, the average grain size is <0.2μm; the coating is subjected to coating surface mechanical treatment before leaving the factory; the coating surface mechanical treatment refers to that the coating surface is treated by wet sand blasting and polishing in turn, so that the coating surface roughness Ra is <0.7μm.

4. The method of claim 3, wherein the coating has enhanced toughness and wear resistance. The TiN coating is prepared by chemical reaction at 900-1000℃ and 100-400mbar, using TiCl4, N2 and H2 as the precursor.

5. The method of claim 3, wherein the coating has enhanced toughness and wear resistance. The Ti(C x N y O z ) coating is prepared by chemical reaction at 800-900 ℃ and 50-200 mbar using TiCl4, N2, CO, H2 and CH3CN mixed gas as precursor; the O content in the Ti(C x N y O z ) coating is controlled by the volume fraction of CO in the mixed gas; the ultra-fine and nanocrystallization of the Ti(C x N y O z ) coating is achieved by increasing the volume fraction of CO in the mixed gas; the volume fraction of CO in the mixed gas is 5%; the increase of the volume fraction of CO in the mixed gas is achieved by reducing the volume fraction of carrier gas H2 in the mixed gas.

6. The method of claim 3, wherein the coating has enhanced toughness and wear resistance. The TiAlOCN coating is prepared by chemical reaction at 900-1000℃ and 50-200mbar, using TiCl4, N2, H2, CH4, CO, CO2 and AlCl3 mixed gas as the precursor.

7. The method of claim 3, wherein the coating has enhanced toughness and wear resistance. The Al2O3 coating is prepared by chemical reaction at 900-1000℃ and 100-250mbar, using H2, AlCl3 and CO2 mixed gas as the precursor, and H2S as the catalyst.

8. Use of a coating with enhanced toughness and wear resistance according to any one of claims 1-2, characterized in that: The application of the coating with enhanced toughness and wear resistance is to be used as a metal machining cutting tool; The coated insert used as a metal machining cutting tool is subjected to coating surface mechanical treatment before leaving the factory; the coating surface mechanical treatment refers to that the coating surface is treated by wet sand blasting and polishing in sequence, so that the coating surface roughness Ra is <0.7μm.

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