A CVD coated cutting tool and its preparation method

Abstract

This invention discloses a CVD-coated cutting tool and its preparation method. The cutting tool includes a tool substrate and a CVD wear-resistant coating deposited on the tool substrate. The CVD wear-resistant coating includes a hard lower layer, a transition layer, and a hard upper layer arranged sequentially from bottom to top. The hard lower layer includes at least one layer of Ti. 1‑a‑b Al a Zr b The N coating satisfies: 0.5 < a < 0.75, 0.02 < b < 0.09; the hard upper layer includes at least one Ti layer. 1‑x‑y‑z Al x Zr y B z The N-coating satisfies the following conditions: 0.6 < x < 0.87, 0.01 < y < 0.06, 0.01 < z < 0.06, and 1.2 < x / a < 1.7, 0.6 < y / b < 0.9. In the transition layer, the Zr atom content gradually decreases from bottom to top, while the Al and B atom contents gradually increase from bottom to top. The tool coating of this invention exhibits high interlayer adhesion, excellent wear resistance, anti-chipping performance, and high-temperature oxidation resistance.

Description

Technical Field

[0001] This invention relates to the field of coated cutting tool technology, and in particular to a CVD coated tool and its preparation method. Background Technology

[0002] Tool coatings typically require excellent wear resistance, high bonding strength, smooth surface, and low coefficient of friction. TiN coatings were among the earliest used coatings, but their low oxidation temperature and low hot hardness have led to their performance becoming increasingly inadequate as industrial development and processing requirements have risen. Adding other elements to TiN coatings is a convenient and effective way to improve their performance.

[0003] Adding the metallic element Al to TiN coatings can improve the coating's hardness and wear resistance, as well as its resistance to high-temperature oxidation. Appropriate Al addition can maintain the face-centered cubic structure of TiAlN, preventing the formation of the hexagonal AlN soft phase and thus optimizing structural stability. Chinese Patent Publication No. CN118241181A discloses a Ti... x Al y A tool with an overlapping N-layer and an Al2O3 layer, wherein Ti... x Al y The N layer has a face-centered cubic crystal structure, x+y=1, where x takes values ​​of 0.1-0.4 and y takes values ​​of 0.6-0.9. Above 800℃, the TiAlN coating undergoes amplitude modulation decomposition into metastable Ti-rich cubic phases c-Ti(Al)N and Al-rich cubic phases c-Al(TiN), resulting in age hardening. However, above 1000℃, these metastable phases transform into their stable phases c-TiN and w-AlN, leading to a decrease in the coating's mechanical properties. In high-speed machining, the cutting edge temperature of the tool exceeds 1000℃, surpassing the service temperature of TiAlN.

[0004] Doping conventional coatings with Zr can improve their hardness and wear resistance. Simultaneously, due to the lattice stabilization effect and the formation of zirconium oxide on the film surface, it can reduce diffusion wear. Adding Zr to TiAlN coatings can improve their thermal stability and high-temperature oxidation resistance, as well as reduce built-up edge. Chinese Patent Publication No. CN1015966607A discloses a method for sequentially depositing Ti, Zr / Ti, and TiZrN coatings on a substrate using PVD. This coating exhibits high hardness and good corrosion resistance, but it has poor toughness and is prone to peeling.

[0005] Using boron-doped TiN coatings can reduce the coefficient of friction and improve the coating's hardness, wear resistance, and oxidation resistance. Chinese Patent Publication No. CN118127459A discloses a TiBN layer containing TiN and TiB2 phases prepared by PVD method. The coating has high hardness but is also brittle. Traditional PVD methods for preparing coatings are prone to peeling off at sharp cutting edges of tools and are difficult to prepare thick coatings.

[0006] With the increasing diversity of cutting materials and the continuous upgrading of performance requirements, improving tool performance by adding two or more other elements to enhance coating performance has attracted more and more attention. Finding new coating systems to further improve the performance of coated tools has become a research hotspot. Chinese Patent Publication No. CN113652639A discloses an alloy coating with a gradient structure containing TiAlYN, TiZrN, and TiSiN layers, which possesses both hardness and toughness. However, the internal stress between the different components of the coating is relatively large, and the bonding force is insufficient, making it prone to peeling and coating failure during use.

[0007] Therefore, a new coating system and preparation method are needed to solve the technical problems of existing coated tools, such as performance degradation at high temperatures, insufficient interlayer bonding, and difficulty in preparing thick coatings by PVD method. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a CVD coated tool with high interlayer adhesion, excellent wear resistance, anti-chipping performance and high temperature oxidation resistance, and its preparation method.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A CVD-coated cutting tool includes a tool substrate and a CVD wear-resistant coating deposited on the tool substrate. The CVD wear-resistant coating comprises a hard lower layer, a transition layer, and a hard upper layer, arranged sequentially from bottom to top. The hard lower layer includes at least one layer of Ti. 1-a-b Al a Zr b N coating, 0.5 < a < 0.75, 0.02 < b < 0.09; the hard upper layer includes at least one Ti layer. 1-x-y-z Al x Zr y B z The N coating has the following properties: 0.6 < x < 0.87, 0.01 < y < 0.06, 0.01 < z < 0.06, 1.2 < x / a < 1.7, and 0.6 < y / b < 0.9. In the transition layer, the Zr atom content gradually decreases from bottom to top, while the Al and B atom contents gradually increase from bottom to top.

[0010] Preferably, as a further improvement to the above technical solution: The transition layer includes at least one Ti layer. h Al i Zr j B k The N coating has the following properties: 0.5 < i < 0.87, 0.01 < j < 0.09, 0 ≤ k < 0.06, and h + i + j + k = 1; the thickness of the transition layer is 0.1~2 μm.

[0011] T i1-a-b Al a Zr b The N coating thickness is 3~10μm, Ti 1-x-y-z Al x Zr y B z The N coating thickness is 3~12μm. This thickness range is beneficial for the coating to have sufficient wear resistance while avoiding excessive coating thickness that could lead to increased thermal residual stress and peeling. The hard lower layer acts as a load-bearing layer, providing support and controlling internal stress, while the hard upper layer acts as the main working layer, providing wear resistance and oxidation resistance. This is achieved by controlling the Ti... 1-x-y-z Al x Zr y B z To improve the thickness of the N coating to enhance Ti 1-x-y-z Al x Zr y B z The performance of the N coating avoids the influence of Ti 1-x-y-z Al x ZryB z Insufficient N coating thickness leads to inadequate wear resistance of the coating; Ti 1-x-y-z Al x Zr y B z If the N coating is too thick, it is prone to peeling due to residual thermal stress.

[0012] Ti 1-x-y-z Al x Zr y B z The microhardness of the N coating is greater than or equal to 34 GPa. This high hardness contributes to the coating's excellent wear resistance during high-speed cutting, effectively extending tool life.

[0013] The CVD wear-resistant coating also includes a bonding layer, which is located between the hard sublayer and the tool substrate. The thickness of the bonding layer is 0.1~3μm, and the bonding layer includes one or more layers of TiN, TiCN, TiAlN, and TiZrN.

[0014] The CVD wear-resistant coating also includes a surface layer, which is located on the hard upper layer. The thickness of the surface layer is 0.1~3μm, and the surface layer includes one or more of TiN layer, TiC layer, TiCN layer and h-AlN layer.

[0015] The tool substrate 1 is made of a superhard material, including one or more of cemented carbide, ceramic, steel or cubic boron nitride.

[0016] This invention also provides a method for preparing CVD coated cutting tools, comprising the following steps: S1. Ti is deposited on the tool substrate using CVD. 1-a-b Al a Zr b The N-coating serves as a hard underlayer. During deposition, the reactive gases include a first gas mixture D1, a second gas mixture D2, and a third gas mixture D3. The first gas mixture D1 comprises AlCl3, TiCl4, and H2; the second gas mixture D2 comprises ZrCl4 and H2; and the third gas mixture D3 comprises NH3 and H2. The volume concentrations of each gas in the first gas mixture D1, the second gas mixture D2, and the third gas mixture D3 are constant. S2, in Ti 1-a-b Al a Zr b A transition layer is deposited on the N-coating using CVD. During deposition, the reaction gases include a first gas mixture M1, a second gas mixture M2, a third gas mixture M3, and a fourth gas mixture M4. The first gas mixture M1 includes AlCl3, TiCl4, and H2; the second gas mixture M2 includes ZrCl4 and H2; the third gas mixture M3 includes NH3 and H2; and the fourth gas mixture M4 includes BCl3 and H2. The volume concentration of AlCl3 in the first gas mixture M1 increases with time, the volume concentration of ZrCl4 in the second gas mixture M2 decreases with time, and the volume concentration of BCl3 in the fourth gas mixture M4 increases with time. S3. Deposit Ti on the transition layer using CVD method. 1-x-y-z Al x Zr y B zDuring the deposition of the N-coating hard upper layer, the reactive gases include a first gas mixture U1, a second gas mixture U2, a third gas mixture U3, and a fourth gas mixture U4. The first gas mixture U1 includes AlCl3, TiCl4, and H2; the second gas mixture U2 includes ZrCl4 and H2; the third gas mixture U3 includes NH3 and H2; and the fourth gas mixture U4 includes BCl3 and H2. The volume concentrations of the first gas mixture U1, the second gas mixture U2, the third gas mixture U3, and the fourth gas mixture U4 are constant. In step S2, the volume concentration of AlCl3 during deposition is between the volume concentration of AlCl3 during deposition in step S1 and the volume concentration of AlCl3 during deposition in step S3. The volume concentration of ZrCl4 during deposition in step S2 is between the volume concentration of ZrCl4 during deposition in step S1 and the volume concentration of ZrCl4 during deposition in step S3. The volume concentration of BCl3 during deposition in step S2 is not higher than the volume concentration of BCl3 during deposition in step S3.

[0017] Preferably, as a further improvement to the above technical solution: In step S1, the volume concentration of TiCl4 in the first gas mixture D1 is 0.01 vol% to 1.0 vol%, the volume concentration ratio of AlCl3 to TiCl4 is 1.0 to 1.8, and the balance is H2; the volume concentration of ZrCl4 in the second gas mixture D2 is 0.1 vol% to 0.6 vol%, and the balance is H2; the volume concentration of NH3 in the third gas mixture D3 is 0.1 vol% to 12 vol%, and the balance is H2. The volume ratio of the first gas mixture D1 to the second gas mixture D2 is 0.5~1.5:1; the volume ratio of the first gas mixture D1 to the third gas mixture D3 is 1~15:1. The deposition temperature was 650-950℃, the deposition pressure was 1-20mbar, and the deposition time was 50-280min.

[0018] Preferably, as a further improvement to the above technical solution: In step S1, the volume concentration of TiCl4 in the first gas mixture D1 is 0.3 vol% to 0.9 vol%, and the volume concentration ratio of AlCl3 to TiCl4 is 1.2 to 1.8. In the second gas mixture D2, the volume concentration of ZrCl4 is 0.2 vol% to 0.6 vol%.

[0019] In the third gas mixture D3, the volume concentration of NH3 is 5 vol%~12 vol.

[0020] The volume ratio of the first gas mixture D1 to the third gas mixture D3 is 5~9:1.

[0021] Preferably, as a further improvement to the above technical solution: In step S2, the volume concentration of TiCl4 in the first gas mixture M1 is 0.01 vol%~1.0 vol%, the volume concentration ratio of AlCl3 to TiCl4 is 1.0~2.4, and the remainder is H2; the volume concentration of ZrCl4 in the second gas mixture M2 is 0.01 vol%~0.6 vol%, and the remainder is H2; the volume concentration of NH3 in the third gas mixture M3 is 0.1 vol%~12 vol%, and the remainder is H2; the volume concentration of BCl3 in M4 is 0.001 vol%~0.5 vol%, and the remainder is H2; the volume ratio of the first gas mixture M1 to the second gas mixture M2 is 0.5~1.5:1; the volume ratio of the first gas mixture M1 to the third gas mixture M3 is 1~15:1; and the volume ratio of the first gas mixture M1 to the third gas mixture M4 is 0.5~1.5:1. The deposition temperature was 650-950℃, the deposition pressure was 1-20mbar, and the deposition time was 10-40min.

[0022] Preferably, as a further improvement to the above technical solution: In the first gas mixture M1, the volume concentration of TiCl4 is 0.3 vol% to 0.9 vol%, and the volume concentration ratio of AlCl3 to TiCl4 is 1.2 to 2.4. In the second gas mixture M2, the volume concentration of ZrCl4 is 0.1 vol% to 0.6 vol%. In the third gas mixture M3, the volume concentration of NH3 is 5 vol% to 12 vol%.

[0023] The volume ratio of the first gas mixture M1 to the third gas mixture M3 is 5~9:1.

[0024] Preferably, as a further improvement to the above technical solution: In step S3, the volume concentration of TiCl4 in the first gas mixture U1 is 0.01 vol%~1.0 vol%, the volume concentration ratio of AlCl3 to TiCl4 is 1.2~2.4, and the remainder is H2; the volume concentration of ZrCl4 in the second gas mixture U2 is 0.01 vol%~0.5 vol%, and the remainder is H2; the volume concentration of NH3 in the third gas mixture U3 is 0.1 vol%~12 vol%, and the remainder is H2; the volume concentration of BCl3 in the fourth gas mixture U4 is 0.1 vol%~0.5 vol%, and the remainder is H2; the volume ratio of the first gas mixture U1 to the second gas mixture U2 is 0.5~1.5:1; the volume ratio of the first gas mixture U1 to the third gas mixture U3 is 1~15:1; and the volume ratio of the first gas mixture U1 to the fourth gas mixture U4 is 0.5~1.5:1. The deposition temperature was 650-950℃, the deposition pressure was 1-20mbar, and the deposition time was 50-330min.

[0025] Preferably, as a further improvement to the above technical solution: The volume concentration of TiCl4 in the first gas mixture U1 is 0.3 vol% to 0.9 vol%, and the volume concentration ratio of AlCl3 to TiCl4 is 1.5 to 2.4. In the second gas mixture U2, the volume concentration of ZrCl4 is 0.1 vol% to 0.5 vol%. In the third gas mixture U3, the volume concentration of NH3 is 5 vol% to 12 vol%.

[0026] The volume ratio of the first gas mixture U1 to the third gas mixture U3 is 5~9:1.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The hard lower layer of the present invention comprises at least one layer of Ti. 1-a-b Al a Zr b N coating, hard upper layer including at least one Ti layer 1-x-y-z Al x Zr y B zIn the TiAlZrN coating of this invention, Zr atoms replace some Ti atoms to form a substitutional solid solution, which strengthens the coating and increases its hardness. Furthermore, because Zr atoms have a larger radius than Ti atoms, their dislocation-hinding effect is more effective, further promoting the increase in coating hardness. Simultaneously, since Zr atoms occupy Ti atoms, they effectively delay the formation of the TiO2 phase during cutting thermal shock, thereby improving the coating's oxidation resistance. Secondly, this invention contains a small amount of Zr in the hard lower layer, the hard upper layer, and the transition layer between these two layers, which helps to improve the bonding force between the coating layers. 1-x-y-z Al x Zr y B z N is set with Ti, which has excellent wear resistance. 1-a-b Al a Zr b The nitrogen coating can improve the load-bearing capacity of the film while reducing the internal stress of the coating. The CVD-coated tool of this invention operates at an edge temperature above 1000℃, and a Ti composition composed of Zr is added to the main working layer, the hard upper layer. 1-x-y-z Al x Zr y B z The N coating forms zirconium oxide on the coating surface, reducing diffused wear and helping to improve the wear resistance of the cutting tool.

[0028] 2. In this invention, the boron (B) atom content in the transition layer gradually increases from bottom to top. This means that a continuous gradient change in B atom content is achieved within the same coating system, rather than a superposition between different coating systems. By setting a transition layer with a gradually changing B atom content, cracks within the coating can be split and deflected, crack propagation can be suppressed, and the toughness of the coating can be improved. Simultaneously, it can alleviate the effects of Ti... 1-a-b Al a Zr b N coating and Ti 1-x-y-z Al x Zr y B z The abrupt change in nitrogen composition enhances the bonding strength between coating layers. Simultaneously, as the boron (B) atom content gradually increases, the coating hardness exhibits an increasing trend, thus optimizing the coating's toughness and wear resistance.

[0029] 3. In the transition layer of this invention, the Al atom content gradually increases from bottom to top, while the Zr atom content gradually decreases from bottom to top. This ensures that the Al atom content in the hard upper layer is higher than that in the hard lower layer, and the Zr atom content in the hard lower layer is higher than that in the hard upper layer. This arrangement allows the hard lower layer to have higher hardness due to its high Zr content, thus providing better support, while the hard upper layer has better resistance to high-temperature oxidation due to its high Al content. By controlling the ratio range of Al content and Zr content in the hard upper and lower layers, this invention ensures that the rate of change in the atomic content of the transition layer is steadily controllable, while also allowing the hard upper and lower layers to support each other and achieve optimal performance.

[0030] 4. This invention further enhances wear resistance and high-temperature oxidation resistance by simultaneously adding small amounts of Zr and B elements to the TiAlN coating, which has excellent high-temperature oxidation resistance, while also reducing the coating friction coefficient. Furthermore, by controlling the atomic content range of Zr and B, it effectively avoids the adverse effects of increasing Zr and B atomic content, such as the complexity and uncontrollability of the coating phase.

[0031] 5. In the preparation method of the present invention, during the deposition of the hard lower layer, a metal source and a nitrogen source are introduced respectively through a three-way gas mixture, and the concentration of each gas mixture is constant, thereby achieving Ti… 1-a-b Al a Zr b Stable deposition of the N coating. During the deposition of the transition layer, the volume concentrations of each gas in the first gas mixture M1, the second gas mixture M2, and the fourth gas mixture M4 vary over time, which facilitates a smooth transition of the transition layer, effectively mitigates abrupt changes in composition, and improves interlayer bonding strength. During the deposition of the hard upper layer, the concentrations of each gas mixture are kept constant to achieve Ti... 1-x-y-z Al x Zr y B z Stable control of the atomic content in the N coating is beneficial for the hard upper layer to have uniform composition and properties. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of the present invention.

[0033] Figure 2 This is a process flow diagram of the present invention.

[0034] Figure 3 This is a comparison diagram of the impact resistance, hardness, and spalling performance of the embodiments and comparative examples of the present invention.

[0035] Figure 4 This is a comparison chart of the wear resistance performance of the embodiments and comparative examples of the present invention.

[0036] Each label in the figure represents: 1. Tool substrate; 2. CVD wear-resistant coating; 20. Bonding layer; 21. Hard lower layer; 22. Transition layer; 23. Hard upper layer; 24. Surface layer Detailed implementation mode The following will further elaborate on the present invention. Unless otherwise specified, the instruments or materials used in the present invention are commercially available.

[0037] As Figure 1 shown, a CVD-coated tool includes a tool substrate 1 and a CVD wear-resistant coating 2 deposited on the tool substrate 1. The CVD wear-resistant coating 2 includes a hard lower layer 21, a transition layer 22, and a hard upper layer 23 arranged in sequence from bottom to top. The hard lower layer 21 includes at least one layer of Ti 1-a-b Al a Zr b N coating, satisfying: 0.55 < a < 0.75, 0.02 < b < 0.09. The hard upper layer 23 includes at least one layer of Ti 1-x-y-z Al x Zr y B z N coating, satisfying: 0.6 < x < 0.87, 0.01 < y < 0.06, 0.01 < z < 0.06, and 1.2 < x / a < 1.7, 0.6 < y / b < 0.9. In the transition layer 22, the content of Zr atoms gradually decreases from bottom to top, and the contents of Al atoms and B atoms gradually increase from bottom to top.

[0038] In the hard lower layer 21, 0.5 < a < 0.75, 0.02 < b < 0.09. This composition range is conducive to Al elements maintaining the face-centered cubic structure, avoiding the precipitation of the hexagonal AlN soft phase, ensuring the balance of high hardness and toughness. The Zr element in this composition range can effectively improve the coating hardness while avoiding the complication and uncontrollability of the coating phase caused by too high Zr atom content.

[0039] In the hard upper layer 23, 0.6 < x < 0.87, 0.01 < y < 0.06, 0.01 < z < 0.06. This composition range realizes the synergistic strengthening effect of the three elements of Al, Zr, and B. The Al element provides high-temperature oxidation resistance, the Zr element provides solid solution strengthening and delays the formation of TiO2 to improve the oxidation resistance performance, the B element reduces the friction coefficient and improves the self-lubricity, while avoiding the embrittlement of the coating caused by too high Zr atom and B atom contents.

[0040] The ratio range of 1.2 < x / a < 1.7 and 0.6 < y / b < 0.9 enables the lower hardness layer 21, the transition layer 22 and the upper hardness layer 23 to synergistically improve performance to achieve the optimal solution. The lower hardness layer 21 provides a high-strength and high-hardness foundation for the upper hardness layer. The gradual transition of Al, Zr and B elements in the transition layer 22 strengthens the bonding effect between the coatings. The high Al and low Zr content of the upper hardness layer 23 enables the coating to have high wear resistance, high temperature oxidation resistance and high toughness.

[0041] like Figure 2 As shown, a method for preparing a CVD coated tool according to the present invention includes the following steps: S1. Ti is deposited on the tool substrate 1 using CVD method. 1-a-b Al a Zr b The N-coating serves as the hard lower layer 21. During deposition, the reactive gases include a first gas mixture D1, a second gas mixture D2, and a third gas mixture D3. The first gas mixture D1 includes AlCl3, TiCl4, and H2; the second gas mixture D2 includes ZrCl4 and H2; and the third gas mixture D3 includes NH3 and H2. The volume concentration of each gas in the first gas mixture D1, the second gas mixture D2, and the third gas mixture D3 is constant. S2, in Ti 1-a-b Al a Zr b A transition layer 22 is deposited on the N-coating using CVD. During deposition, the reaction gases include a first gas mixture M1, a second gas mixture M2, a third gas mixture M3, and a fourth gas mixture M4. The first gas mixture M1 includes AlCl3, TiCl4, and H2; the second gas mixture M2 includes ZrCl4 and H2; the third gas mixture M3 includes NH3 and H2; and the fourth gas mixture M4 includes BCl3 and H2. The volume concentration of AlCl3 in the first gas mixture M1 increases with time, the volume concentration of ZrCl4 in the second gas mixture M2 decreases with time, and the volume concentration of BCl3 in the fourth gas mixture M4 increases with time. S3. Ti is deposited on transition layer 22 using CVD method. 1-x-y-z Al x Zr y B zThe N-coating, serving as the hard upper layer 23, is deposited using a reaction gas mixture comprising a first gas mixture U1, a second gas mixture U2, a third gas mixture U3, and a fourth gas mixture U4. The first gas mixture U1 comprises AlCl3, TiCl4, and H2; the second gas mixture U2 comprises ZrCl4 and H2; the third gas mixture U3 comprises NH3 and H2; and the fourth gas mixture U4 comprises BCl3 and H2. The volume concentrations of the first gas mixture U1, the second gas mixture U2, the third gas mixture U3, and the fourth gas mixture U4 are constant. In step S2, the volume concentration of AlCl3 during deposition is between the volume concentration of AlCl3 during deposition in step S1 and the volume concentration of AlCl3 during deposition in step S3. The volume concentration of ZrCl4 during deposition in step S2 is between the volume concentration of ZrCl4 during deposition in step S1 and the volume concentration of ZrCl4 during deposition in step S3. The volume concentration of BCl3 during deposition in step S2 is not higher than the volume concentration of BCl3 during deposition in step S3.

[0042] In the preparation method of this invention, during the deposition of the hard lower layer 21, a metal source and a nitrogen source are introduced through a three-way gas mixture. The concentration of each gas mixture is constant, thereby achieving Ti… 1-a-b Al a Zr b Stable deposition of the N coating. During the deposition of the transition layer 22, the volume concentrations of each gas in the first gas mixture M1, the second gas mixture M2, and the fourth gas mixture M4 vary over time. The volume concentrations of AlCl3 and BCl3 at earlier times are lower than those at later times, while the volume concentration of ZrCl4 at earlier times is higher than that at later times. This achieves a gradient transition with gradually increasing Al and B atom content and a gradually decreasing Zr atom content, which is beneficial for the smooth transition of the transition layer 22, effectively mitigating abrupt compositional changes and improving interlayer bonding strength. During the deposition of the hard upper layer 23, the concentrations of each gas mixture are kept constant to achieve Ti... 1-x-y-z Al x Zr y B z Stable control of the Al, Zr and B atom content in the N coating is beneficial for the hard upper layer 23 to have uniform composition and properties.

[0043] Example 1 like Figure 2 As shown, a method for preparing a CVD-coated tool includes the following steps: (1) Prepare a cemented carbide tool substrate 1 with model number CNMG120408-TC. Its composition includes 6wt.% Co, 1wt.% (Ta+Nb), and the balance is WC.

[0044] (2) Coating is performed in a CVD coating furnace. A TiN layer is deposited on the tool substrate 1 as a bonding layer 20 using existing CVD technology, with a deposition thickness of 1.0 μm.

[0045] (3) Deposition of TiAlZrN coating: On the bonding layer 20, TiAlZrN coating is deposited as a hard lower layer 21. The reaction gas is introduced into the coating furnace through three gas pipelines. The first gas mixture D1, the second gas mixture D2 and the third gas mixture D3 are preheated and then mixed in the coating furnace to deposit the TiAlZrN coating. The deposition conditions are shown in Table 1.

[0046] Table 1. Deposition conditions of TiAlZrN coatings in the examples

[0047] (4) Deposition of transition layer 22: The transition layer 22 is deposited on the TiAlZrN coating. The reaction gas is introduced into the coating furnace through four gas pipelines. The first gas mixture M1, the second gas mixture M2, the third gas mixture M3 and the fourth gas mixture M4 are preheated and then mixed in the coating furnace to deposit the transition layer 22. The deposition conditions are shown in Table 2.

[0048] Table 2 Deposition conditions of transition layer 22 in the embodiments

[0049] (5) Deposition of TiAlZrBN coating: On the transition layer 22, TiAlZrBN coating is deposited as a hard upper layer 23. The reaction gas is introduced into the coating furnace through four gas pipelines. The first gas mixture U1, the second gas mixture U2, the third gas mixture U3 and the fourth gas mixture U4 are preheated and then mixed in the coating furnace to deposit the TiAlZrBN coating. The deposition conditions are shown in Table 3.

[0050] Table 3. Deposition conditions of TiAlZrBN coating in the examples

[0051] (6) A TiN layer was deposited on the TiAlZrBN coating as a surface layer 24 using the existing CVD process, with a deposition thickness of 1.0 μm.

[0052] (7) Perform wet sandblasting and polishing on the coating surface.

[0053] Example 2 The preparation method of a CVD coated tool in this embodiment is largely the same as that in Embodiment 1, except that the deposition conditions are different, as shown in Tables 1, 2 and 3 for Embodiment 2.

[0054] Comparative Examples 1-10 A method for preparing a CVD-coated cutting tool includes the following steps: (1) Prepare a cemented carbide tool substrate 1 with model number CNMG120408-TC. Its composition includes 6wt.% Co, 1wt.% (Ta+Nb), and the balance is WC.

[0055] (2) Coating is performed in a CVD coating furnace. A TiN layer is deposited on the tool substrate 1 as a bonding layer 20 using existing CVD technology, with a deposition thickness of 1.0 μm.

[0056] (3) Using CVD process, the first gas mixture D1, the second gas mixture D2 and the third gas mixture D3 are preheated and introduced into the coating furnace as reaction gases for mixing. The hard lower layer 21 is deposited in the coating furnace according to the deposition conditions in Table 4.

[0057] Table 4. Depositional conditions of the lower hard layer 21

[0058]

[0059] (4) Using CVD process, the first gas mixture M1, the second gas mixture M2, the third gas mixture M3 and the fourth gas mixture M4 are preheated and introduced into the coating furnace as reaction gases for mixing. In the coating furnace, the transition layer 22 is deposited on the hard lower layer 21 according to the deposition conditions in Table 5.

[0060] Table 5 shows the depositional conditions of transition layer 22 in the comparative examples.

[0061]

[0062] (5) Using CVD process, the first gas mixture U1, the second gas mixture U2, the third gas mixture U3 and the fourth gas mixture U4 are used as reaction gases and are introduced into the coating furnace after preheating. In the coating furnace, the hard upper layer 23 is deposited on the transition layer 22 according to the deposition conditions in Table 6.

[0063] Table 6. Depositional conditions of the hard upper layer 23

[0064] (6) A TiN layer is deposited on the hard upper layer 23 as the surface layer 24 using the existing CVD process.

[0065] (7) Perform wet sandblasting and polishing on the coating surface.

[0066] Coating composition analysis: After cutting, mounting, grinding, and polishing the blades of the examples and comparative examples, the coating composition was analyzed by scanning electron microscopy (SEM-EDS). The thickness of the hard substrate layer and the hard layer was measured. The results are shown in Table 7.

[0067] Table 7. Coating composition and thickness of each embodiment and comparative example.

[0068] Table 7 shows that, compared to Examples 1 and 2, the Zr atom content in the hard upper layer 23 of Comparative Example 1 is higher; the B atom content in the hard upper layer 23 of Comparative Example 2 is higher; the Al atom content in the hard upper layer 23 of Comparative Example 3 is higher, while the Zr and B atom contents are both lower; the Al atom content in the hard upper layer 23 of Comparative Example 4 is lower, while the Zr and B atom contents are both higher; neither the hard upper layer 23 nor the transition layer 22 of Comparative Example 5 contains Zr; neither the hard upper layer 23 nor the transition layer 22 of Comparative Example 6 contains B; neither the hard upper layer 23 nor the transition layer 22 of Comparative Example 7 contains Al; neither the hard lower layer 21 of Comparative Example 8 contains Zr; neither the hard lower layer 21 of Comparative Example 9 contains Al; and neither the hard lower layer 21 of Comparative Example 10 contains Zr. The Al content of the hard lower layer 21 is higher than that of the hard upper layer 23. In Comparative Example 11, the Zr content of the hard upper layer 23 is higher than that of the hard lower layer 21. In Comparative Example 12, there is only the hard lower layer 21 without the transition layer 22 and the hard upper layer 23. In Comparative Example 13, there is only the hard upper layer 23 without the hard lower layer 21 and the transition layer 22. In Comparative Example 14, there are only the hard lower layer 21 and the hard upper layer 23 without the transition layer 22. In Comparative Example 15, the composition of the transition layer 22 is fixed, with no gradient change in elements. In Comparative Example 16, the ratio of Al atoms in the hard upper layer 23 to the hard lower layer 21 is 0.82 / 0.33≈2.48, which is greater than 1.7. In Comparative Example 17, the ratio of Zr atoms in the hard upper layer 23 to the hard lower layer 21 is 0.02 / 0.1=0.2, which is less than 0.6.

[0069] Nanohardness test The nanohardness of the hardened blade layers in each set of examples and comparative examples was tested using nanoindentation. The maximum load was 30.00 mN, the loading rate was 60.00 mN / min, the unloading rate was 60.00 mN / min, and the holding time was 10.0 s. To avoid the influence of the substrate on the hardness, the indentation depth was less than 1 / 10 of the total coating thickness. The hardness of each sample was measured at 10 different points, and the average value was taken as the nanohardness of the coating. The results are shown in Table 8.

[0070] Table 8. Nanoscale hardness of the hard layer in each embodiment and comparative example.

[0071] The test results show that the nanohardness of the coating of the present invention is comparable to that of comparative examples 6, 11, and 13, slightly better than comparative examples 1 and 14-16, and significantly better than the other comparative examples. The measured results for the coating of the present invention and comparative examples 6, 11, and 13-16 are Ti. 1-x-y- z Al x Zr y B z The N coating (hard upper layer 23), and the Al and Zr contents of both are within appropriate ranges, indicate that the Ti of the present invention... 1-x-y-z Al x Zr y B z The high nanohardness of the N coating also indicates that the presence of Al and Zr within an appropriate range significantly promotes the nanohardness of the coating.

[0072] Combined strength test: indentation peel test The coating adhesion strength of each set of examples and comparative examples was tested using an indentation-peel test. The method is as follows: The experimental equipment was a standard Rockwell hardness tester, with a diamond indenter specification of HRC-3, a vertex angle α = 120° ± 30°, and a spherical radius R at the tip of the indenter = 0.2 ± 0.01 mm. The applied force was 588 N. The coating adhesion strength was evaluated by the proportion of the perimeter of the coating peeled off around the indentation. The results are shown in Table 9.

[0073] Table 9. Test results of bonding strength for each embodiment and comparative example.

[0074] Experimental results show that the indentation peeling rate of the present invention is lower than that of most of the comparative examples, indicating that the bonding strength between the coatings of the present invention is high.

[0075] Performance Comparison Test: Cutting Performance Test Turning wear resistance tests were conducted on each set of examples and comparative examples. The wear value on the flank face, Vb = 0.3 mm, was used as the criterion for insert failure. The longer the machining time before failure, the better the wear resistance. The turning test conditions are shown in Table 10.

[0076] Table 10 Turning Test Conditions

[0077] The test results are shown in Table 11, which compares the wear on the back face.

[0078] Table 11 Comparison of back face wear Vb (mm) for each embodiment and comparative example.

[0079]

[0080] Based on the results in Table 11, a comparison chart of the wear resistance performance of the examples and comparative examples is presented, as follows: Figure 4 As shown in Table 11 and Figure 4 It can be seen that the lifespan of the coated blades of Examples 1 and 2 of the present invention is 20 minutes, which is 100% higher than that of Comparative Examples 3, 4, 7 and 12, 33% higher than that of Comparative Examples 1-2, 5-6, 8, 11 and 13-17, and lower than that of Comparative Examples 9 and 10 at the same processing time. This indicates that the coated blades of Examples 1 and 2 of the present invention have excellent wear resistance.

[0081] Impact test Impact tests were conducted on each set of examples and comparative examples. Edge chipping was used as the criterion for blade failure, and the number of impacts was used to evaluate the blade's resistance to chipping; more impacts indicated better resistance. Test conditions are shown in Table 12. Impact test results are shown in Table 13.

[0082] Table 12 Impact test conditions for each embodiment and comparative example

[0083] Table 13 Impact test results of each embodiment and comparative example

[0084] As can be seen from the comparison of the impact test results in Table 13, the blade coated with the coating of the present invention has significantly more impact resistance times, indicating that the coated blade of the present invention has better chipping resistance.

[0085] Based on the above data and Figure 3 , Figure 4It can be seen that: compared with Comparative Examples 1, 5, and 14-17, Examples 1 and 2 have a slight advantage in nanoscale hardness, and significant advantages in anti-stripping performance, impact resistance, and wear resistance; compared with Comparative Examples 2-4 and 7, Examples 1 and 2 have significant advantages in nanoscale hardness, anti-stripping performance, impact resistance, and wear resistance; compared with Comparative Example 6, Examples 1 and 2 are comparable in nanoscale hardness and anti-stripping performance, and have advantages in impact resistance and wear resistance; compared with Comparative Example 8, Examples 1 and 2 have a slight advantage in impact resistance and anti-stripping performance, and significant advantages in nanoscale hardness and wear resistance; compared with Comparative Example 9, Examples 1 and 2 have advantages in impact resistance... Examples 1 and 2 show slight advantages in impact resistance and wear resistance, but significant advantages in anti-stripping and nano-hardness. Compared to Comparative Example 10, Examples 1 and 2 have comparable impact resistance, slight advantages in anti-stripping and wear resistance, and significant advantages in nano-hardness. Compared to Comparative Example 11, Examples 1 and 2 have comparable nano-hardness and significant advantages in anti-stripping, impact resistance, and wear resistance. Compared to Comparative Example 12, Examples 1 and 2 have comparable anti-stripping performance, but advantages in nano-hardness, impact resistance, and wear resistance. Compared to Comparative Example 13, Examples 1 and 2 have comparable nano-hardness and anti-stripping performance, a slight advantage in impact resistance, and a significant advantage in wear resistance. Considering all factors, the embodiments of this invention exhibit the best overall performance.

[0086] Example 3 A method for preparing a CVD-coated cutting tool includes the following steps: (1) Prepare a cemented carbide tool substrate 1 with model number SEET12T3-DM, the composition of which includes 10wt.% Co, 3wt.% (Ta+Nb), and the balance is WC.

[0087] (2) Coating is performed in a CVD coating furnace. A TiN layer is deposited on the tool substrate 1 as a bonding layer 20 using existing CVD technology, with a deposition thickness of 1.0 μm.

[0088] (3) Deposition of TiAlZrN coating: TiAlZrN coating is deposited on the bonding layer 20 as a hard lower layer 21. CVD process is used, and the reaction gas is introduced into the coating furnace through three gas pipelines. The first gas mixture D1, the second gas mixture D2 and the third gas mixture D3 are preheated and then mixed in the coating furnace to deposit the TiAlZrN coating. The deposition conditions are shown in Table 14.

[0089] (4) Deposition of transition layer 22: The transition layer 22 is deposited on the TiAlZrN coating. The CVD process is used, and the reaction gas is introduced into the coating furnace through four gas pipelines. The first gas mixture M1, the second gas mixture M2, the third gas mixture M3 and the fourth gas mixture M4 are preheated and then mixed in the coating furnace to deposit the transition layer 22. The deposition conditions are shown in Table 14.

[0090] (5) Deposition of TiAlZrBN coating: Continue to deposit TiAlZrBN coating on transition layer 22. CVD process is adopted. The reaction gas is introduced into the coating furnace through four gas pipelines. The first gas mixture U1, the second gas mixture U2, the third gas mixture U3 and the fourth gas mixture U4 are preheated and then mixed in the coating furnace to deposit the TiAlZrBN coating. The deposition conditions are shown in Table 14.

[0091] (6) A TiN layer was deposited on the TiAlZrBN coating as a surface layer 24 using the existing CVD process, with a deposition thickness of 1.0 μm.

[0092] (7) Perform wet sandblasting and polishing on the coating surface.

[0093] Table 14 Deposition conditions of each coating in Example 3

[0094] Example 4 A method for preparing a CVD-coated cutting tool includes the following steps: (1) Prepare a cemented carbide tool substrate 1 with model number SEET12T3-DM, the composition of which includes 10wt.% Co, 3wt.% (Ta+Nb), and the balance is WC.

[0095] (2) Coating is performed in a CVD coating furnace. A TiN layer is deposited on the tool substrate 1 as a bonding layer 20 using existing CVD technology, with a deposition thickness of 1.0 μm.

[0096] (3) Deposition of TiAlZrN coating: TiAlZrN coating is deposited on the bonding layer 20 as a hard lower layer 21. CVD process is used, and the reaction gas is introduced into the coating furnace through three gas pipelines. The first gas mixture D1, the second gas mixture D2 and the third gas mixture D3 are preheated and then mixed in the coating furnace to deposit the TiAlZrN coating. The deposition conditions are shown in Table 15.

[0097] (4) Deposition of transition layer 22: The transition layer 22 is deposited on the TiAlZrN coating. The CVD process is used, and the reaction gas is introduced into the coating furnace through four gas pipelines. The first gas mixture M1, the second gas mixture M2, the third gas mixture M3 and the fourth gas mixture M4 are preheated and then mixed in the coating furnace to deposit the transition layer 22. The deposition conditions are shown in Table 15.

[0098] (5) Deposition of TiAlZrBN coating: Continue to deposit TiAlZrBN coating on transition layer 22. CVD process is adopted. The reaction gas is introduced into the coating furnace through four gas pipelines. The first gas mixture U1, the second gas mixture U2, the third gas mixture U3 and the fourth gas mixture U4 are preheated and then mixed in the coating furnace to deposit the TiAlZrBN coating. The deposition conditions are shown in Table 15.

[0099] (6) A TiN layer was deposited on the TiAlZrBN coating as a surface layer 24 using the existing CVD process, with a deposition thickness of 1.0 μm.

[0100] (7) Perform wet sandblasting and polishing on the coating surface.

[0101] Table 15 Deposition conditions of each coating in Example 4

[0102] Comparative Example 11 A method for preparing a PVD-coated cutting tool includes the following steps: A cemented carbide tool substrate 1 with model number SEET12T3-DM was prepared. Its composition includes 10 wt.% Co, 3 wt.% (Ta+Nb), and the balance is WC.

[0103] A PVD coating is applied to the substrate using conventional PVD coating technology. The preparation method is as follows: (1) A TiN layer was deposited on the pretreated tool substrate by PVD DC magnetron sputtering at a deposition temperature of 500℃ and a deposition pressure of 1Pa. Ar and N2 were used, the target material was a Ti target, the target power was 1kW, and the coating thickness was 1μm. (2) A TiAlZrN layer was deposited on the TiN layer by PVD DC magnetron sputtering at a deposition temperature of 500℃ and a deposition pressure of 1Pa. Ar and N2 were used, the target material was a TiAlZr composite target, the target power was 2kW, and the coating thickness was 4μm.

[0104] (3) A TiAlZrBN layer was deposited on the TiAlZrN layer by PVD DC magnetron sputtering at a deposition temperature of 500℃ and a deposition pressure of 1Pa. Ar and N2 were used, the target material was a TiAlZrB composite target, the target power was 2kW, and the coating thickness was 4μm.

[0105] Comparative Example 12 A method for preparing a PVD-coated cutting tool includes the following steps: A cemented carbide tool substrate 1 with model number SEET12T3-DM was prepared. Its composition includes 10 wt.% Co, 3 wt.% (Ta+Nb), and the balance is WC.

[0106] A PVD coating is applied to the substrate using conventional PVD coating technology. The preparation method is as follows: (1) A TiN layer was deposited on the pretreated tool substrate by PVD DC magnetron sputtering at a deposition temperature of 500℃ and a deposition pressure of 1Pa. Ar and N2 were used, the target material was a Ti target, the target power was 1kW, and the coating thickness was 1μm. (2) A TiAlZrN layer was deposited on the TiN layer by PVD DC magnetron sputtering at a deposition temperature of 500℃ and a deposition pressure of 1Pa. Ar and N2 were used, the target material was a TiAlZr composite target, the target power was 2kW, and the coating thickness was 8μm.

[0107] (3) A TiAlZrBN layer was deposited on the TiAlZrN layer by PVD DC magnetron sputtering at a deposition temperature of 500℃ and a deposition pressure of 1Pa. Ar and N2 were used, the target material was a TiAlZrB composite target, the target power was 2kW, and the coating thickness was 8μm.

[0108] After cutting, mounting, grinding, and polishing the blades of Examples 2, 3, and Comparative Examples 11-12, the coating composition was analyzed by scanning electron microscopy (SEM-EDS), and the thickness was measured. The results are shown in Table 16.

[0109] Table 16 Coating composition and thickness of each embodiment and comparative example

[0110] As shown in Table 16, the coating composition and thickness of Example 3 and Comparative Example 11 are not significantly different. The main difference is that the coating of Example 3 was prepared by CVD, while the coating of Comparative Example 11 was prepared by PVD. Similarly, the coating composition and thickness of Example 4 and Comparative Example 12 are not significantly different. The main difference is that the coating of Example 4 was prepared by CVD, while the coating of Comparative Example 12 was prepared by PVD.

[0111] Coating adhesion testing: Sandblasting peeling test The finished cutting tools from Examples 3-4 and Comparative Examples 11-12 were subjected to sandblasting under the same conditions: a slurry of 400-mesh corundum powder and water was used, with a water-to-sand ratio of 20%~25%. Sandblasting was performed on a rotary table wet sandblasting machine at a pressure of 3.5 kg for 10 seconds. The sandblasted cutting tools were then examined under an optical microscope at X40 magnification to assess the coating peeling in four regions (A, B, C, and D). Region A represents the small facet and arc area of ​​the cutting tool; region B represents the effective cutting edge area; region C represents the ineffective cutting edge area; and region D represents the center hole and clamping area. The test results are shown in Table 17 below.

[0112] Table 17. Statistics on coating peeling in each embodiment and comparative example.

[0113] As can be seen from the percentage of coating peeling in the effective processing areas A and B of the blade in Table 17, the coating peeling percentage of the present invention is significantly lower than that of the comparative example. Because poor coating adhesion is the reason why coating peeling is easy to occur, the low coating peeling percentage indicates that the coating of the present invention has excellent adhesion.

[0114] High-temperature oxidation resistance test: Oxidative weight gain test The oxidation weight gain of Examples 3-4 and Comparative Examples 11-12 was tested using the following method: Each group of samples was placed in a muffle furnace and heated to 1000°C in air for 1.5 hours. The samples were then removed from the muffle furnace and cooled to room temperature in air. The weight of each sample before and after oxidation was measured using an electronic balance with an accuracy of 0.1 mg, and the weight difference before and after oxidation was calculated as the oxidation weight gain. The results are shown in Table 18.

[0115] Table 18 Statistics on Oxidative Weight Gain

[0116] As can be seen from Table 18, the weight gain of the embodiments using the present invention is relatively small, indicating that the coating still maintains its original dense structure when kept at 1000°C for 1 hour, and less oxygen enters the coating, indicating that the coating of the present invention has excellent high-temperature oxidation resistance.

[0117] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A CVD coated cutting tool, characterized in that: The tool substrate (1) includes a CVD wear-resistant coating (2) deposited on the tool substrate (1). The CVD wear-resistant coating (2) includes a hard lower layer (21), a transition layer (22) and a hard upper layer (23) arranged sequentially from bottom to top. The hard lower layer (21) includes at least one Ti layer. 1-a-b Al a Zr b N coating, 0.50 < a < 0.75, 0.02 < b < 0.09, the hard upper layer (23) includes at least one Ti layer. 1-x-y-z Al x Zr y B z The N coating has the following properties: 0.6 < x < 0.87, 0.01 < y < 0.06, 0.01 < z < 0.06, and 1.2 < x / a < 1.7, 0.6 < y / b < 0.

9. In the transition layer (22), the Zr atom content gradually decreases from bottom to top, while the Al and B atom contents gradually increase from bottom to top.

2. The CVD coated tool according to claim 1, characterized in that: The T i1-a-b Al a Zr b The thickness of the N coating is 3~10μm, and the Ti 1-x-y-z Al x Zr y B z The thickness of the N coating is 3~12μm.

3. The CVD coated tool according to claim 1, characterized in that: The minimum Zr atom content of the transition layer (22) is not lower than the Zr atom content in the hard upper layer (23), the maximum B atom content of the transition layer (22) is not higher than the B atom content in the hard upper layer (23), and the maximum Al atom content of the transition layer (22) is not higher than the Al atom content in the hard upper layer (23).

4. The CVD coated tool according to any one of claims 1 to 3, characterized in that: The CVD wear-resistant coating (2) further includes a bonding layer (20) and a surface layer (24). The bonding layer (20) is located between the hard lower layer (21) and the tool substrate (1), and the surface layer (24) is located on the hard upper layer (23).

5. The CVD coated tool according to claim 4, characterized in that: The thickness of the bonding layer (20) is 0.1~3μm; the bonding layer (20) includes one or more of TiN layer, TiCN layer, TiAlN layer, and TiZrN layer.

6. The CVD coated tool according to claim 4, characterized in that: The thickness of the surface layer (24) is 0.1~3μm; the surface layer (24) includes one or more of TiN layer, TiC layer, TiCN layer and h-AlN layer.

7. A method for preparing a CVD coated tool according to any one of claims 1 to 6, characterized in that: Includes the following steps: S1. Ti is deposited on the tool substrate (1) using CVD method. 1-a-b Al a Zr b The N-coating serves as a hard lower layer (21). During deposition, the reaction gases include a first gas mixture D1, a second gas mixture D2, and a third gas mixture D3. The first gas mixture D1 includes AlCl3, TiCl4, and H2; the second gas mixture D2 includes ZrCl4 and H2; and the third gas mixture D3 includes NH3 and H2. The volume concentration of each gas in the first gas mixture D1, the second gas mixture D2, and the third gas mixture D3 is constant. S2, in Ti 1-a-b Al a Zr b A transition layer (22) is deposited on the N coating using CVD. During deposition, the reaction gases include a first gas mixture M1, a second gas mixture M2, a third gas mixture M3, and a fourth gas mixture M4. The first gas mixture M1 includes AlCl3, TiCl4, and H2. The second gas mixture M2 includes ZrCl4 and H2. The third gas mixture M3 includes NH3 and H2. The fourth gas mixture M4 includes BCl3 and H2. The volume concentration of AlCl3 in the first gas mixture M1 increases with time. The volume concentration of ZrCl4 in the second gas mixture M2 decreases with time. The volume concentration of BCl3 in the fourth gas mixture M4 increases with time. S3. Ti is deposited on the transition layer (22) using CVD. 1-x-y-z Al x Zr y B z The N-coating serves as a hard upper layer (23). During deposition, the reactive gases include a first gas mixture U1, a second gas mixture U2, a third gas mixture U3, and a fourth gas mixture U4. The first gas mixture U1 includes AlCl3, TiCl4, and H2; the second gas mixture U2 includes ZrCl4 and H2; the third gas mixture U3 includes NH3 and H2; and the fourth gas mixture U4 includes BCl3 and H2. The volume concentrations of the first gas mixture U1, the second gas mixture U2, the third gas mixture U3, and the fourth gas mixture U4 are constant. In step S2, the volume concentration of AlCl3 during deposition is between the volume concentration of AlCl3 during deposition in step S1 and the volume concentration of AlCl3 during deposition in step S3. The volume concentration of ZrCl4 during deposition in step S2 is between the volume concentration of ZrCl4 during deposition in step S1 and the volume concentration of ZrCl4 during deposition in step S3. The volume concentration of BCl3 during deposition in step S2 is not higher than the volume concentration of BCl3 during deposition in step S3.

8. The method for preparing CVD coated cutting tools according to claim 7, characterized in that: In step S1, the volume concentration of TiCl4 in the first gas mixture D1 is 0.01 vol% to 1.0 vol%, the volume concentration ratio of AlCl3 to TiCl4 is 1.0 to 1.8, and the balance is H2; the volume concentration of ZrCl4 in the second gas mixture D2 is 0.1 vol% to 0.6 vol%, and the balance is H2; the volume concentration of NH3 in the third gas mixture D3 is 0.1 vol% to 12 vol%, and the balance is H2. The volume ratio of the first gas mixture D1 to the second gas mixture D2 is 0.5~1.5:1; the volume ratio of the first gas mixture D1 to the third gas mixture D3 is 1~15:

1. The deposition temperature is 650-950℃ and the deposition pressure is 1-20mbar.

9. The method for preparing the CVD coated tool according to claim 7, characterized in that: In step S2, in the first gas mixture M1, the volume concentration of TiCl4 is 0.01 vol%~1.0 vol%, the volume concentration ratio of AlCl3 to TiCl4 is 1.0~2.4, and the balance is H2; in the second gas mixture M2, the volume concentration of ZrCl4 is 0.01 vol%~0.6 vol%, and the balance is H2; in the third gas mixture M3, the volume concentration of NH3 is 0.1 vol%~12 vol%, and the balance is H2; in the fourth gas mixture M4, the volume concentration of BCl3 is 0.001 vol%~0.5 vol%, and the balance is H2. The volume ratio of the first gas mixture M1 to the second gas mixture M2 is 0.5~1.5:1; the volume ratio of the first gas mixture M1 to the third gas mixture M3 is 1~15:1; and the volume ratio of the first gas mixture M1 to the fourth gas mixture M4 is 0.5~1.5:

1. The deposition temperature is 650-950℃ and the deposition pressure is 1-20mbar.

10. The method for preparing the CVD coated tool according to claim 7, characterized in that: In step S3, in the first gas mixture U1, the volume concentration of TiCl4 is 0.01 vol%~1.0 vol%, the volume concentration ratio of AlCl3 to TiCl4 is 1.2~2.4, and the balance is H2; in the second gas mixture U2, the volume concentration of ZrCl4 is 0.01 vol%~0.5 vol%, and the balance is H2; in the third gas mixture U3, the volume concentration of NH3 is 0.1 vol%~12 vol%, and the balance is H2; in the fourth gas mixture U4, the volume concentration of BCl3 is 0.1 vol%~0.5 vol%, and the balance is H2. The volume ratio of the first gas mixture U1 to the second gas mixture U2 is 0.5~1.5:1; the volume ratio of the first gas mixture U1 to the third gas mixture U3 is 1~15:1; and the volume ratio of the first gas mixture U1 to the fourth gas mixture U4 is 0.5~1.5:

1. The deposition temperature is 650-950℃ and the deposition pressure is 1-20mbar.

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