Coated cemented carbide tool and method for manufacturing the same

Abstract

The present application relates to the technical field of coated cutting tools, and provides a coated cemented carbide cutting tool and a preparation method thereof, wherein the cemented carbide substrate comprises a core and a shallow surface layer covering the core, and the whole is constructed as a hard zone with a two-phase zone lower limit or a decarburization phase, and the shallow surface layer also has a toughness zone rich in binder phase, which effectively avoids the problem of performance degradation of the toughness zone of the substrate caused by carbon loss on the surface of the cemented carbide substrate when a coating is deposited on the substrate by chemical vapor deposition. Moreover, the continuous brittle η phase is generated at the film-substrate interface between the coating and the shallow surface layer, thereby reducing the stress concentration points and crack source distribution between the coating and the substrate, which is beneficial to the formation of a chemical vapor deposition coating with low internal stress and high bonding force, and significantly improves the bonding strength between the coating and the substrate.

Description

Technical Field

[0001] This invention belongs to the field of coated cutting tool technology, specifically relating to a coated cemented carbide cutting tool and its preparation method. Background Technology

[0002] Carbon content is a quality control threshold for cemented carbide. The properties of materials differ in the two-phase region. Increasing the total carbon content can improve performance, but it also narrows the two-phase region, increasing the difficulty of control. When the cobalt magnetic properties are in the lower limit region, the solid solubility of cobalt is high, resulting in high hardness, fracture strength, and overall strength. When the magnetic properties are in the upper limit region, the solid solubility of carbon in cobalt increases, while the solid solubility of W decreases, leading to a decrease in strength and high-temperature resistance, thus affecting the overall mechanical properties of the material.

[0003] After sintering, cemented carbide is typically coated with chemical vapor deposition (CVD) to enhance its surface properties. However, in traditional CVD processes, hydrogen, used as a carrier gas, readily reacts with carbon in the cemented carbide at high temperatures, leading to surface decarburization and the formation of continuous η-phases (such as Co3W3C, Co6W6C, and Co2W4C). These brittle, continuous η-phases exist at the film-substrate interface (i.e., the substrate-coating interface), becoming stress concentration points and crack initiation sites, significantly reducing the bonding strength between the coating and the substrate. Furthermore, the unstable surface state of the decarburized phases is detrimental to the formation of low-stress, high-bonding CVD coatings.

[0004] Therefore, in order to solve the problem of reduced toughness and strength of cemented carbide after chemical vapor deposition, the usual approach is to increase the total carbon in the alloy to compensate for the carbon loss after the coating is deposited on the substrate surface. However, a high total carbon content in the substrate will reduce the solid solubility of tungsten in cobalt, which is not conducive to improving the high-temperature hardness and strength of the alloy. Furthermore, increasing the carbon content narrows the two-phase region, which brings certain difficulties to production control.

[0005] In existing technologies, some carburizing sintering processes introduce a carburizing atmosphere at high temperatures. While this can replenish carbon, the intense diffusion of carbon under high-temperature conditions can easily lead to uneven carbon distribution or over-carburizing, and it is difficult to precisely control the carbon content on the surface and in the shallow layers. Furthermore, high-temperature carburizing may exacerbate grain coarsening, affecting the overall properties of the alloy. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention aims to propose a coated cemented carbide cutting tool and its preparation method.

[0007] According to a first aspect of the present invention, the present invention provides the following technical solution:

[0008] A coated carbide cutting tool, comprising:

[0009] A cemented carbide substrate and a coating deposited on the surface of the cemented carbide substrate using chemical vapor deposition;

[0010] The cemented carbide substrate includes a core and a shallow layer covering the core, with the shallow layer in direct contact with the coating.

[0011] In the film-substrate interface region between the coating and the shallow layer (i.e., in the substrate-coating interface region), there is no η phase, or only a discontinuously distributed η phase with a maximum thickness of less than 1 μm exists;

[0012] And the shallow layer meets the following conditions:

[0013] In the shallow layer, a relatively high carbon layer is formed by carburizing in the region near the surface of the cemented carbide substrate, and the carbon content shows a gradient change from the surface of the cemented carbide substrate toward the core.

[0014] In the shallow layer, a continuous solid solution phase with the characteristics of (Ti,Ta,Nb,Mo)C-type complex cubic carbide structure does not form;

[0015] The mass fraction of the binder phase in the shallow layer is higher than that in the core.

[0016] As a preferred embodiment of the coated cemented carbide cutting tool of the present invention, the core satisfies the following conditions:

[0017] The carbon content of the core in the WC / binder phase alloy two-phase region is 5.5~7.5 wt.%; specifically, the carbon content of the core in the WC / binder phase alloy two-phase region can be, for example, any one or any two of the following: 5.5 wt.%, 5.6 wt.%, 5.7 wt.%, 5.8 wt.%, 5.9 wt.%, 6.0 wt.%, 6.1 wt.%, 6.2 wt.%, 6.3 wt.%, 6.4 wt.%, 6.5 wt.%, 6.6 wt.%, 6.7 wt.%, 6.8 wt.%, 6.9 wt.%, 7.0 wt.%, 7.1 wt.%, 7.2 wt.%, 7.3 wt.%, 7.4 wt.%, 7.5 wt.%.

[0018] The core exhibits decarburized phase characteristics of grade E0 or E02~E06 as defined in GB / T 3488.4-2022 standard (Metallographic determination of microstructure of cemented carbide).

[0019] In a preferred embodiment of the coated cemented carbide cutting tool of the present invention, the cemented carbide substrate comprises the following components:

[0020] TiC content is 2~10 wt.%;

[0021] One or more of Co and Ni, in a content of 5-10 wt.%;

[0022] One or more of TiN and TiCN, in a content of 0.1~1 wt.%;

[0023] One or more of Ta, Nb, and Mo carbides, in a content of 0–6 wt.%;

[0024] WC, remaining balance.

[0025] As a preferred embodiment of the coated cemented carbide cutting tool of the present invention, the total content of Ti / Ta / Nb / Mo carbides in the shallow layer is <0.5 wt.%, preferably <0.3 wt.%.

[0026] As a preferred embodiment of the coated cemented carbide cutting tool of the present invention, the thickness of the shallow layer is 2~50μm; the diffusion depth of carbon from the surface of the cemented carbide substrate towards the core is 5~50μm.

[0027] In a preferred embodiment of the coated cemented carbide cutting tool of the present invention, the mass fraction of the binder phase in the shallow layer is 120-140% of the mass fraction of the binder phase in the core.

[0028] As a preferred embodiment of the coated cemented carbide cutting tool of the present invention, the coating is deposited on a shallow surface layer, and the coating includes, from the inside out (i.e. from the surface of the cemented carbide substrate to the coating direction), a TiN layer, a TiCN layer, a TiCNO transition layer and an α-Al2O3 layer.

[0029] As a preferred embodiment of the coated cemented carbide cutting tool of the present invention, wherein:

[0030] The TiN layer has an equiaxed crystal structure with a thickness of 0.1~2μm and an average grain size of ≤0.4μm;

[0031] The TiCN layer has a columnar crystal structure with a thickness of 1.5~10μm and an average grain size of 0.1~2μm.

[0032] The TiCNO transition layer has a needle-like or equiaxed crystal structure, with a thickness of 0.1~1.5μm and an average grain size of ≤0.5μm;

[0033] The α-Al₂O₃ layer has an equiaxed crystal structure with a thickness of 2–10 μm and an average grain size of 0.2–3 μm.

[0034] As a preferred embodiment of the coated cemented carbide cutting tool of the present invention, the cemented carbide substrate has the following characteristics: saturation magnetization of 65-80%, coercivity of 100-400 Oe, hardness of HV30 of 1200-1700, and fracture toughness of 8-18 MPa·m. 1 / 2The WC average intercept is 0.4~2.0μm, and the adhesion between the coating and the cemented carbide substrate is ≥80N (determined according to GB / T30707-2014 "Test Method for Adhesion of Fine Ceramic Coatings - Scratch Method").

[0035] According to a second aspect of the present invention, the present invention provides the following technical solution:

[0036] A method for preparing the above-mentioned coated cemented carbide cutting tool includes the following steps:

[0037] S1. Preparation of raw material powder: The raw material powder is prepared by mixing the components of the cemented carbide matrix, adding a forming agent, and mixing the total carbon of the mixture. Then, the raw material powder is obtained by ball milling and granulation.

[0038] S2, Compression molding: The raw material powder prepared in step S1 is molded into a cemented carbide blank;

[0039] S3. Vacuum dewaxing: The cemented carbide blank prepared in step S2 is placed in a sintering furnace and heated to 250-300℃ at a rate of 0.5-1.5℃ / min under a vacuum of less than 200Pa, and held for 120-180min to complete the dewaxing.

[0040] S4. Vacuum sintering: Under vacuum conditions below 10 Pa, heat to 1100℃ at a rate of 3~7℃ / min and hold for 5~30min;

[0041] S5. Atmosphere sintering: After step S4, nitrogen and argon are introduced into the furnace at a pressure of 10~15 kPa (the volume ratio of nitrogen to argon is 1:2), and the temperature is increased to 1200~1300℃ at a rate of 0.5~1℃ / min.

[0042] S6. Atmosphere sintering: After step S5, the temperature is increased to 1420~1480℃ at a rate of 3~8℃ / min under a furnace pressure of 10~15kPa.

[0043] S7. Vacuum sintering: After step S6, hold at the sintering temperature for 20-60 minutes under a vacuum of less than 10 Pa.

[0044] S8. Vacuum sintering: After step S7, the temperature is lowered to 1370~1420℃ under a vacuum condition of less than 10Pa.

[0045] S9. Carburizing sintering: After step S8, carburizing gas and helium are introduced. The carburizing gas includes one or more of CO, CH4, C2H2, and C2H4. The helium content is 1 to 10 vol% of the total volume of the introduced gas. Then, the gas is held at a pressure of 20 to 100 mbar for 40 to 90 min.

[0046] S10, High-pressure sintering: After step S9, vacuum treatment is performed, followed by argon gas being introduced to a pressure of 4~10MPa and held at that temperature for 30~60min.

[0047] S11, High-pressure cooling: After step S10 is completed, heating is stopped, and the atmospheric pressure of step S10 is maintained to cool to room temperature to obtain a cemented carbide matrix;

[0048] S12, Tool Substrate Coating: After step S11, a coating is deposited on the surface of the cemented carbide substrate using chemical vapor deposition. The coating consists of a TiN layer, a TiCN layer, a TiCNO transition layer, and an α-Al2O3 layer, from the inside out, to obtain a coated cemented carbide tool.

[0049] In a preferred embodiment of the method for preparing a coated cemented carbide cutting tool according to the present invention, the following steps are taken: The materials are prepared according to the composition of the cemented carbide matrix, specifically:

[0050] TiC content is 2~10 wt.%;

[0051] One or more of Co and Ni, in a content of 5-10 wt.%;

[0052] One or more of TiN and TiCN, in a content of 0.1~1 wt.%;

[0053] One or more of Ta, Nb, and Mo carbides, in a content of 0–6 wt.%;

[0054] WC, remaining balance.

[0055] In a preferred embodiment of the preparation method of the coated cemented carbide cutting tool of the present invention, the particle size of WC is 2.0~6.0μm, the particle size of TiC is 0.8~2.0μm, the particle size of Co is 0.6~2.0μm, the particle size of Ni is 0.6~2.0μm, the particle size of TiN and / or TiCN is 0.8~1.5μm, and the particle size of the carbides of Ta, Nb and / or Mo is 0.6~3.0μm.

[0056] The beneficial effects of this invention are as follows:

[0057] This invention provides a coated cemented carbide cutting tool and its preparation method. The cemented carbide substrate includes a core and a shallow layer covering the core. The overall structure consists of a hard region in the core with a two-phase lower limit or a decarburized phase. While maintaining the hardness of the substrate, the shallow layer also has a tough region rich in a binder phase. This effectively avoids the problem of carbon loss on the surface of the cemented carbide substrate, which leads to the degradation of the tough region's properties when depositing coatings on the substrate using chemical vapor deposition (CVD). Furthermore, because a continuous η-phase, which reduces brittleness, is generated at the film-substrate interface between the coating and the shallow layer, the distribution of stress concentration points and crack initiation sites between the coating and the substrate is reduced. This is beneficial for forming a low-stress, high-adhesion CVD coating, significantly improving the bonding strength between the coating and the substrate. Attached Figure Description

[0058] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0059] Figure 1 This is a cross-sectional view of the coated cemented carbide cutting tool of Embodiment 1 of the present invention.

[0060] Figure 2 This is a cross-sectional view of the coated cemented carbide cutting tool of Embodiment 2 of the present invention.

[0061] Figure 3 This is a cross-sectional view of the coated cemented carbide cutting tool of Embodiment 3 of the present invention.

[0062] Figure 4 This is a cross-sectional view of the coated cemented carbide cutting tool of Comparative Example 1 of the present invention.

[0063] In the figure, 1-coating, 2-shallow layer, 3-core, 4-η phase at the membrane-substrate interface.

[0064] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0065] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] This invention proposes a coated cemented carbide cutting tool and its preparation method. It employs a one-step gradient sintering method to prepare a binder-rich, tough region on the shallow surface of a cemented carbide substrate. Simultaneously, during the liquid-phase cooling stage, the binder-rich, tough region undergoes carburizing treatment. Through carburizing of the substrate surface and the shallow surface layer, carbon loss from the substrate surface is compensated, preventing the formation of continuous decarburized phases. This provides a clean, decarburized-phase-free film-substrate interface for subsequent chemical vapor deposition coating. The clean, carbon-saturated surface reduces internal stress in the coating and extends its lifespan. Specific features are as follows:

[0067] (1) In this invention, under the condition that the cemented carbide is low in carbon as a whole, or even has a decarburized phase, it provides good hardness and wear resistance to the cemented carbide.

[0068] (2) In this invention, the high mass fraction of the binder phase in the shallow layer is beneficial for the diffusion of coating cracks into the matrix material during the cutting process of the chemical vapor deposition coating, and the second carbide that migrates into the core maintains better high-temperature red hardness of the matrix material.

[0069] (3) In this invention, since the thermal conductivity of helium is significantly higher than that of argon, nitrogen and other gases (at 20°C, the thermal conductivity of helium is about 0.15 W / (m·K), which is more than 5 times that of argon), it can quickly and uniformly transfer heat to all parts of the powder blank, avoid "overheating" or "underfiring" caused by local temperature differences, reduce defects such as cracks and deformation, and the implementation stage is lower than the final firing temperature, which makes it easy to finely control the uniform distribution of carburization and the carbon content of the shallow surface layer.

[0070] (4) In this invention, the high carbon content of the shallow layer avoids the serious deterioration of the substrate properties due to the continuous η phase at the film-substrate interface caused by the reaction of the carrier gas in the chemical vapor deposition coating, reduces the possibility of stress concentration points and crack sources, thereby improving the bonding strength between the coating and the substrate.

[0071] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0072] Example 1

[0073] A method for preparing a coated cemented carbide cutting tool includes the following steps:

[0074] S1. Preparation of raw material powder: The raw materials are prepared according to the composition of the cemented carbide matrix, specifically: TiC, content of 2.5 wt.%; Co, content of 6 wt.%; TiN, content of 0.5 wt.%; TaC, content of 5 wt.%; WC, balance; 2 wt.% of 52# paraffin molding agent is added, and the total carbon content of the mixture is 5.88 wt.%. The raw material powder is then obtained by ball milling and granulation.

[0075] S2, Compression molding: The raw material powder prepared in step S1 is molded into a cemented carbide blank;

[0076] S3. Vacuum dewaxing: The cemented carbide blank prepared in step S2 is placed in a sintering furnace and heated to 260°C at a rate of 1°C / min under a vacuum of less than 200 Pa, and held for 180 min to complete the dewaxing.

[0077] S4. Vacuum sintering: Under vacuum conditions below 10 Pa, heat to 1100℃ at a rate of 5℃ / min and hold for 30 min.

[0078] S5. Atmosphere sintering: After step S4, nitrogen and argon are introduced into the furnace at a pressure of 15 kPa (the volume ratio of nitrogen to argon is 1:2), and the temperature is increased to 1270℃ at a rate of 0.5℃ / min.

[0079] S6. Atmosphere sintering: After step S5, the temperature is increased to 1470℃ at a rate of 5℃ / min under a furnace pressure of 15kPa.

[0080] S7. Vacuum sintering: After step S6, hold at the sintering temperature for 30 minutes under a vacuum of less than 10 Pa.

[0081] S8. Vacuum sintering: After step S7, the temperature is lowered to 1370℃ under a vacuum condition of less than 10 Pa.

[0082] S9. Carburizing sintering: After step S8, carburizing gas and helium are introduced. The carburizing gas is CH4 and the helium content is 5 vol% of the total volume of the introduced gas. Then, the temperature is maintained at 40 mbar for 60 min.

[0083] S10, High-pressure sintering: After step S9, vacuum treatment is performed, followed by argon gas being introduced to a pressure of 6MPa and held at that temperature for 30 minutes.

[0084] S11, High-pressure cooling: After step S10 is completed, heating is stopped, and the atmospheric pressure of step S10 is maintained to cool to room temperature to obtain a cemented carbide matrix;

[0085] S12. Tool Substrate Coating: After step S11, a coating is deposited on the surface of the cemented carbide substrate using chemical vapor deposition. From the inside out, the coating consists of a TiN layer, a TiCN layer, a TiCNO transition layer, and an α-Al2O3 layer, resulting in a coated cemented carbide tool. Its cross-sectional metallographic micrograph is shown below. Figure 1 As shown, the distribution of the decarburized phase 4 in the film-based interface region between the coating 1 and the shallow layer 2 (the lower part of the shallow layer 2 is the core 3) in this embodiment is as follows: the thickness of the η phase is less than 1 μm, and the η phase in the interface region is discontinuous throughout the entire field of view.

[0086] Example 2

[0087] A method for preparing a coated cemented carbide cutting tool includes the following steps:

[0088] S1. Preparation of raw material powder: The raw materials are prepared according to the composition of the cemented carbide matrix, specifically: TiC, content of 2.5 wt.%; Co, content of 6 wt.%; TiN, content of 0.5 wt.%; TaC, content of 5 wt.%; WC, balance; 2 wt.% of 52# paraffin molding agent is added, and the total carbon content of the mixture is 5.88 wt.%. The raw material powder is then obtained by ball milling and granulation.

[0089] S2, Compression molding: The raw material powder prepared in step S1 is molded into a cemented carbide blank;

[0090] S3. Vacuum dewaxing: The cemented carbide blank prepared in step S2 is placed in a sintering furnace and heated to 260°C at a rate of 1°C / min under a vacuum of less than 200 Pa, and held for 180 min to complete the dewaxing.

[0091] S4. Vacuum sintering: Under vacuum conditions below 10 Pa, heat to 1100℃ at a rate of 5℃ / min and hold for 30 min.

[0092] S5. Atmosphere sintering: After step S4, nitrogen and argon are introduced into the furnace at a pressure of 15 kPa (the volume ratio of nitrogen to argon is 1:2), and the temperature is increased to 1300℃ at a rate of 0.8℃ / min.

[0093] S6. Atmosphere sintering: After step S5, the temperature is increased to 1450℃ at a rate of 7.5℃ / min under a furnace pressure of 15kPa.

[0094] S7. Vacuum sintering: After step S6, hold at the sintering temperature for 45 minutes under a vacuum of less than 10 Pa.

[0095] S8. Vacuum sintering: After step S7, the temperature is reduced to 1400℃ under a vacuum condition of less than 10 Pa.

[0096] S9. Carburizing sintering: After step S8, carburizing gas and helium are introduced. The carburizing gas is CO and the helium content is 10 vol% of the total volume of the introduced gas. Then, the temperature is maintained at 60 mbar for 40 min.

[0097] S10, High-pressure sintering: After step S9, vacuum treatment is performed, followed by argon gas being introduced to a pressure of 6MPa and held at that temperature for 30 minutes.

[0098] S11, High-pressure cooling: After step S10 is completed, heating is stopped, and the atmospheric pressure of step S10 is maintained to cool to room temperature to obtain a cemented carbide matrix;

[0099] S12. Tool Substrate Coating: After step S11, a coating is deposited on the surface of the cemented carbide substrate using chemical vapor deposition. From the inside out, the coating consists of a TiN layer, a TiCN layer, a TiCNO transition layer, and an α-Al2O3 layer, resulting in a coated cemented carbide tool. Its cross-sectional metallographic micrograph is shown below. Figure 2 As shown, the distribution of the decarburized phase 4 in the film-based interface region between the coating 1 and the shallow layer 2 (the lower part of the shallow layer 2 is the core 3) in this embodiment is as follows: the thickness of the η phase is less than 1 μm, and the η phase in the interface region is discontinuous throughout the entire field of view.

[0100] Example 3

[0101] A method for preparing a coated cemented carbide cutting tool includes the following steps:

[0102] S1. Preparation of raw material powder: The raw materials are prepared according to the composition of the cemented carbide matrix, specifically: TiC, content of 2.5 wt.%; Co, content of 6 wt.%; TiN, content of 0.5 wt.%; TaC, content of 5 wt.%; WC, balance; 2 wt.% of 56# paraffin molding agent is added, and the total carbon content of the mixture is 5.88 wt.%. The raw material powder is then obtained by ball milling and granulation.

[0103] S2, Compression molding: The raw material powder prepared in step S1 is molded into a cemented carbide blank;

[0104] S3. Vacuum dewaxing: The cemented carbide blank prepared in step S2 is placed in a sintering furnace and heated to 280°C at a rate of 1°C / min under a vacuum of less than 200Pa, and held for 150min to complete the dewaxing.

[0105] S4. Vacuum sintering: Under vacuum conditions below 10 Pa, heat to 1100℃ at a rate of 3.5℃ / min and hold for 15 min;

[0106] S5. Atmosphere sintering: After step S4, nitrogen and argon are introduced into the furnace at a pressure of 10 kPa (the volume ratio of nitrogen to argon is 1:2), and the temperature is increased to 1250℃ at a rate of 1℃ / min.

[0107] S6. Atmosphere sintering: After step S5, the temperature is increased to 1450℃ at a rate of 3℃ / min under a furnace pressure of 15kPa.

[0108] S7. Vacuum sintering: After step S6, hold at the sintering temperature for 30 minutes under a vacuum of less than 10 Pa.

[0109] S8. Vacuum sintering: After step S7, the temperature is reduced to 1380℃ under a vacuum condition of less than 10 Pa.

[0110] S9. Carburizing sintering: After step S8, carburizing gas and helium are introduced. The carburizing gas includes CO and C2H2. The helium content is 2 vol% of the total volume of the introduced gas. Then, the temperature is maintained at 20 mbar for 90 min.

[0111] S10, High-pressure sintering: After step S9, vacuum treatment is performed, followed by argon gas being introduced to a pressure of 9MPa and held at that temperature for 30 minutes.

[0112] S11, High-pressure cooling: After step S10 is completed, heating is stopped, and the atmospheric pressure of step S10 is maintained to cool to room temperature to obtain a cemented carbide matrix;

[0113] S12. Tool Substrate Coating: After step S11, a coating is deposited on the surface of the cemented carbide substrate using chemical vapor deposition. From the inside out, the coating consists of a TiN layer, a TiCN layer, a TiCNO transition layer, and an α-Al2O3 layer, resulting in a coated cemented carbide tool. Its cross-sectional metallographic micrograph is shown below. Figure 3 As shown, in this embodiment, the distribution of the decarburized phase 4 in the membrane-based interface region between the coating 1 and the shallow layer 2 (the lower part of the shallow layer 2 is the core 3) is as follows: there is almost no η phase.

[0114] Example 4

[0115] A method for preparing a coated cemented carbide cutting tool includes the following steps:

[0116] S1. Preparation of raw material powder: The raw materials are prepared according to the composition of the cemented carbide matrix, specifically: TiC, 4 wt.%; Co, 6 wt.%; TiN, 1 wt.%; TaC, 5 wt.%; Mo2C, 1 wt.%; WC, balance; 2 wt.% of 52# paraffin molding agent is added, and the total carbon content of the mixture is 5.88 wt.%. The mixture is then ball-milled and granulated to obtain the raw material powder.

[0117] S2, Compression molding: The raw material powder prepared in step S1 is molded into a cemented carbide blank;

[0118] S3. Vacuum dewaxing: The cemented carbide blank prepared in step S2 is placed in a sintering furnace and heated to 260°C at a rate of 1°C / min under a vacuum of less than 200 Pa, and held for 180 min to complete the dewaxing.

[0119] S4. Vacuum sintering: Under vacuum conditions below 10 Pa, heat to 1100℃ at a rate of 5℃ / min and hold for 30 min.

[0120] S5. Atmosphere sintering: After step S4, nitrogen and argon are introduced into the furnace at a pressure of 15 kPa (the volume ratio of nitrogen to argon is 1:2), and the temperature is increased to 1270℃ at a rate of 0.5℃ / min.

[0121] S6. Atmosphere sintering: After step S5, the temperature is increased to 1470℃ at a rate of 5℃ / min under a furnace pressure of 15kPa.

[0122] S7. Vacuum sintering: After step S6, hold at the sintering temperature for 30 minutes under a vacuum of less than 10 Pa.

[0123] S8. Vacuum sintering: After step S7, the temperature is lowered to 1370℃ under a vacuum condition of less than 10 Pa.

[0124] S9. Carburizing sintering: After step S8, carburizing gas and helium are introduced. The carburizing gas is CH4 and the helium content is 5 vol% of the total volume of the introduced gas. Then, the temperature is maintained at 40 mbar for 60 min.

[0125] S10, High-pressure sintering: After step S9, vacuum treatment is performed, followed by argon gas being introduced to a pressure of 6MPa and held at that temperature for 30 minutes.

[0126] S11, High-pressure cooling: After step S10 is completed, heating is stopped, and the atmospheric pressure of step S10 is maintained to cool to room temperature to obtain a cemented carbide matrix;

[0127] S12, Tool Substrate Coating: After step S11, a coating is deposited on the surface of the cemented carbide substrate using chemical vapor deposition. The coating consists of a TiN layer, a TiCN layer, a TiCNO transition layer, and an α-Al2O3 layer, from the inside out, to obtain a coated cemented carbide tool.

[0128] Example 5

[0129] A method for preparing a coated cemented carbide cutting tool includes the following steps:

[0130] S1. Preparation of raw material powder: The raw materials are prepared according to the composition of the cemented carbide matrix, specifically: TiC, 4 wt.%; Co, 6 wt.%; TiN, 1 wt.%; TaC, 5 wt.%; WC, balance; 2 wt.% of 52# paraffin molding agent is added, and the total carbon content of the mixture is 5.97 wt.%. The mixture is then ball-milled and granulated to obtain the raw material powder.

[0131] S2, Compression molding: The raw material powder prepared in step S1 is molded into a cemented carbide blank;

[0132] S3. Vacuum dewaxing: The cemented carbide blank prepared in step S2 is placed in a sintering furnace and heated to 260°C at a rate of 1°C / min under a vacuum of less than 200 Pa, and held for 180 min to complete the dewaxing.

[0133] S4. Vacuum sintering: Under vacuum conditions below 10 Pa, heat to 1100℃ at a rate of 5℃ / min and hold for 30 min.

[0134] S5. Atmosphere sintering: After step S4, nitrogen and argon are introduced into the furnace at a pressure of 15 kPa (the volume ratio of nitrogen to argon is 1:2), and the temperature is increased to 1270℃ at a rate of 0.5℃ / min.

[0135] S6. Atmosphere sintering: After step S5, the temperature is increased to 1470℃ at a rate of 5℃ / min under a furnace pressure of 15kPa.

[0136] S7. Vacuum sintering: After step S6, hold at the sintering temperature for 30 minutes under a vacuum of less than 10 Pa.

[0137] S8. Vacuum sintering: After step S7, the temperature is lowered to 1370℃ under a vacuum condition of less than 10 Pa.

[0138] S9. Carburizing sintering: After step S8, carburizing gas and helium are introduced. The carburizing gas is CH4 and the helium content is 5 vol% of the total volume of the introduced gas. Then, the temperature is maintained at 40 mbar for 60 min.

[0139] S10, High-pressure sintering: After step S9, vacuum treatment is performed, followed by argon gas being introduced to a pressure of 6MPa and held at that temperature for 30 minutes.

[0140] S11, High-pressure cooling: After step S10 is completed, heating is stopped, and the atmospheric pressure of step S10 is maintained to cool to room temperature to obtain a cemented carbide matrix;

[0141] S12, Tool Substrate Coating: After step S11, a coating is deposited on the surface of the cemented carbide substrate using chemical vapor deposition. The coating consists of a TiN layer, a TiCN layer, a TiCNO transition layer, and an α-Al2O3 layer, from the inside out, to obtain a coated cemented carbide tool.

[0142] Comparative Example 1

[0143] A method for preparing a coated cemented carbide cutting tool includes the following steps:

[0144] S1. The raw materials are prepared according to the composition of the cemented carbide matrix, specifically: TiC, 2.5 wt.%; Co, 6 wt.%; TiN, 0.5 wt.%; TaC, 5 wt.%; WC, balance; 2 wt.% of 52# paraffin molding agent is added, and the total carbon content of the mixture is 5.88 wt.%. The mixture is then ball-milled and granulated to obtain the raw material powder.

[0145] S2. The raw material powder prepared in step S1 is molded into a cemented carbide blank.

[0146] S3. Place the cemented carbide blank prepared in step S2 in a sintering furnace, heat it to 260°C at a rate of 1°C / min under a vacuum condition below 200Pa, and hold it for 180min to complete the dewaxing.

[0147] S4. Under vacuum conditions below 10 Pa, heat to 1100℃ at a rate of 5℃ / min and hold for 15 min;

[0148] S5. After step S4, nitrogen and argon (volume ratio of nitrogen to argon is 1:2) are introduced into the furnace at a pressure of 15 kPa, and the temperature is increased to 1270℃ at a rate of 0.5℃ / min.

[0149] S6. After step S5 is completed, the temperature is increased to 1470℃ at a rate of 5℃ / min under a furnace pressure of 15kPa.

[0150] S7. After step S6 is completed, argon gas is introduced and kept at a pressure of 6 MPa for 60 min.

[0151] S8. After step S7 is completed, stop heating and maintain the atmospheric pressure of step S7 to cool to room temperature to obtain a cemented carbide matrix.

[0152] S9. After step S8, a coating is deposited on the surface of the cemented carbide substrate using chemical vapor deposition. From the inside out, the coating consists of a TiN layer, a TiCN layer, a TiCNO transition layer, and an α-Al₂O₃ layer, resulting in a coated cemented carbide cutting tool. Its cross-sectional metallographic micrograph is shown below. Figure 4 As shown, the distribution of the decarburized phase 4 in the film-based interface region between coating 1 and shallow layer 2 (the lower part of shallow layer 2 is the core 3) in this comparative example is as follows: the thickness of the η phase is as high as 2.49 μm, and the η phase exists continuously in the interface region throughout the entire field of view.

[0153] Comparative Example 2

[0154] A method for preparing a coated cemented carbide cutting tool includes the following steps:

[0155] S1. The raw materials are prepared according to the composition of the cemented carbide matrix, specifically: TiC, with a content of 5 wt.%; Co, with a content of 8 wt.%; NbC, with a content of 4.5 wt.%; WC, balance; 2 wt.% of 52# paraffin molding agent is added, and the total carbon content of the mixture is 5.80 wt.%. The mixture is then ball-milled and granulated to obtain the raw material powder.

[0156] S2. The raw material powder prepared in step S1 is molded into a cemented carbide blank.

[0157] S3. Place the cemented carbide blank prepared in step S2 in a sintering furnace, heat it to 260°C at a rate of 1°C / min under a vacuum condition below 200Pa, and hold it for 180min to complete the dewaxing.

[0158] S4. Under vacuum conditions below 10 Pa, heat to 1100℃ at a rate of 5℃ / min and hold for 15 min;

[0159] S5. After step S4 is completed, argon gas is introduced into the furnace at a pressure of 15 kPa, and the temperature is increased to 1300℃ at a rate of 0.5℃ / min.

[0160] S6. After step S5 is completed, the temperature is increased to 1490℃ at a rate of 5℃ / min under a furnace pressure of 15kPa.

[0161] S7. After step S6 is completed, argon gas is introduced and kept at a pressure of 6 MPa for 60 min.

[0162] S8. After step S7 is completed, stop heating and maintain the atmospheric pressure of step S7 to cool to room temperature to obtain a cemented carbide matrix.

[0163] S9. After step S8, a coating is deposited on the surface of the cemented carbide substrate using chemical vapor deposition. The coating consists of a TiN layer, a TiCN layer, a TiCNO transition layer, and an α-Al2O3 layer, from the inside out, to obtain a coated cemented carbide cutting tool.

[0164] The microstructure of the substrates in the examples and comparative examples was studied, and the average intercept length of the tungsten carbide phase was measured. The mechanical / mechanical properties of the substrates and their interaction with the coating were tested, and the following parameters were obtained, as shown in the table below.

[0165]

[0166] As can be seen from the table above, the performance of the coated carbide cutting tools in the embodiments of the present invention is better than that in the comparative examples. When the core hardness and toughness of the materials in the embodiments of the present invention and the comparative examples are similar, the WC hard carbide grain size is comparable, maintaining the overall material performance. However, the continuity of the η phase at the coating interface is significantly less than that in the comparative examples (or even non-existent). The coating adhesion measured by scratch is significantly higher than that in the comparative examples. In actual cutting test applications, the failure mode of the cutting tools in the embodiments is mainly coating wear, while a higher proportion of coating peeling occurs in the comparative examples.

[0167] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A coated cemented carbide tool, characterized in that, Comprising: a cemented carbide substrate and a coating deposited on the surface of the cemented carbide substrate by chemical vapor deposition; the cemented carbide substrate comprises a core and a surface layer covering the core, and is integrally constructed as a hard zone with a two-phase zone lower limit or a decarburized phase in the core, so that the surface layer has a toughness zone rich in binder phase in addition to the hardness performance of the substrate; the surface layer is in direct contact with the coating; in the film-substrate interface region between the coating and the surface layer, there is no η phase, or only discontinuously distributed η phase with a maximum thickness of less than 1 μm; and the surface layer satisfies the following conditions: in the surface layer, a relatively high carbon layer is formed by carburization in the region close to the surface of the cemented carbide substrate, and the carbon content presents a decreasing gradient from the surface of the cemented carbide substrate to the core; in the surface layer, no continuous solid solution phase of the (Ti, Ta, Nb, Mo)C type of complex cubic carbide structure feature is formed; the mass fraction of the binder phase in the surface layer is higher than that in the core.

2. The coated cemented carbide tool according to claim 1, characterized in that, the core satisfies the following conditions: the carbon content of the core in the WC / binder phase alloy two-phase zone is 5.5-7.5 wt.%; the core has E0 grade or E02-E06 grade decarburized phase characteristics.

3. The coated cemented carbide tool according to claim 1, characterized in that, The cemented carbide substrate comprises the following components: TiC, content 2-10 wt.%; one or more of Co, Ni, content 5-10 wt.%; one or more of TiN, TiCN, content 0.1-1 wt.%; one or more of carbides of Ta, Nb, Mo, content 0-6 wt.%; WC, balance.

4. The coated cemented carbide tool according to claim 1, characterized in that, The total content of Ti / Ta / Nb / Mo carbides in the surface layer is <0.5 wt.%.

5. The coated cemented carbide tool according to claim 1, characterized in that, The thickness of the surface layer is 2-50 μm; the diffusion depth of carbon from the surface of the cemented carbide substrate to the core is 5-50 μm.

6. The coated cemented carbide tool according to claim 1, characterized in that, The mass fraction of the binder phase in the surface layer is 120-140% of that in the core.

7. The coated cemented carbide tool according to claim 1, characterized in that, The coating is deposited on the surface layer, and the coating comprises, from inside to outside, a TiN layer, a TiCN layer, a TiCNO transition layer and an α-Al2O3 layer.

8. The coated cemented carbide tool according to claim 7, characterized in that, The TiN layer is an equiaxed crystal structure, the thickness is 0.1-2 μm, and the average grain size is ≤0.4 μm; The TiCN layer is a columnar crystal structure, the thickness is 1.5-10 μm, and the average grain size is 0.1-2 μm; The TiCNO transition layer is a needle-shaped crystal or equiaxed crystal structure, the thickness is 0.1-1.5 μm, and the average grain size is ≤0.5 μm; The α-Al2O3 layer is an equiaxed crystal structure, the thickness is 2-10 μm, and the average grain size is 0.2-3 μm.

9. The coated cemented carbide tool according to claim 1, characterized in that, The saturation magnetization of the cemented carbide base is 65-80%, the coercive force is 100-400 Oe, the hardness HV30 is 1200-1700, the fracture toughness is 8-18 MPa·m 1 / 2 , the average intercept of WC is 0.4-2.0 μm, and the bonding force between the coating and the cemented carbide base is ≥80 N.

10. A method of producing a coated cemented carbide tool according to any one of claims 1-9, c h a r a c t e r i s e d in that Comprising the following steps: S1, preparing raw material powder: according to the composition of the cemented carbide substrate, the raw material powder is prepared by ball milling and granulation; S2, press forming: the raw material powder prepared in step S1 is molded to obtain a cemented carbide compact; S3, vacuum dewaxing: the cemented carbide compact prepared in step S2 is placed in a sintering furnace and heat treated under vacuum to complete dewaxing; S4, vacuum sintering: heat treatment and sintering under vacuum; S5, atmosphere sintering: after step S4, nitrogen and argon with a volume ratio of 1:2 are introduced into the furnace under a pressure of 10-15 kPa, and the temperature is raised to 1200-1300°C at a rate of 0.5-1°C / min; S6, atmosphere sintering: after step S5, the temperature is raised to 1420-1480°C at a rate of 3-8°C / min under a pressure of 10-15 kPa in the furnace; S7, vacuum sintering: after step S6, the temperature is maintained at the sintering temperature for 20-60 min under a vacuum of 10 Pa or less; S8, vacuum sintering: after step S7, the temperature is lowered to 1370-1420°C under a vacuum of 10 Pa or less; S9, carburizing sintering: after step S8, carburizing gas and helium are introduced, the carburizing gas including one or more of CO, CH4, C2H2, and C2H4, and the helium content being 1-10 vol% of the total volume of the introduced gas, and then the temperature is maintained for 40-90 min under a pressure of 20-100 mbar; S10, high-pressure sintering: after step S9, vacuum treatment is performed, and then argon is introduced to a pressure of 4-10 MPa, and the temperature is maintained for 30-60 min; S11, high-pressure cooling: after step S10, the heating is stopped, the atmosphere pressure of step S10 is maintained, and the temperature is cooled to room temperature, to obtain a cemented carbide substrate; S12, tool substrate coating: after step S11, a coating is deposited on the surface of the cemented carbide substrate by chemical vapor deposition, including a TiN layer, a TiCN layer, a TiCNO transition layer, and an α-Al2O3 layer from the inside to the outside, to obtain a coated cemented carbide tool.

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