Coated hard alloy cutter and preparation method thereof

Abstract

The invention relates to the technical field of coated cutters, and provides a coated hard alloy cutter and a preparation method thereof.The coated hard alloy cutter is characterized in that a hard alloy matrix comprises a core part and a shallow surface layer wrapping the core part, and the whole hard alloy matrix is constructed into a hard area with the core part provided with a two-phase area lower limit or a decarburized phase; and the shallow surface layer is also provided with a toughness area rich in a binding phase, so that the problem that the performance of the toughness area of the matrix is degraded due to carbon loss on the surface of the hard alloy matrix when the coating is deposited on the matrix by adopting a chemical vapor deposition method is effectively avoided. And the generation of the brittle continuous eta phase at the film-substrate interface between the coating and the shallow surface layer is reduced, so that the stress concentration point and crack source distribution between the coating and the substrate are reduced, the formation of the chemical vapor deposition coating with low internal stress and high binding force is facilitated, and the binding strength of the coating and the substrate is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of coated cutting tools, and in particular relates to a coated cemented carbide cutting tool and a preparation method thereof. Background Art

[0002] Carbon content is the quality control line for cemented carbide. The performance of materials in the two-phase region varies. Increasing the total carbon content of the material can improve performance, but it also causes the two-phase region to narrow, making control more difficult. When the cobalt magnetic properties of the material are at the lower limit, the solid solubility of the metallic elements in the cobalt is high, resulting in high hardness, fracture resistance, and strength. When the magnetic properties are at the upper limit of the two-phase region, the solid solubility of carbon in the cobalt increases, while the solid solubility of W decreases, resulting in a decrease in the material's strength and high-temperature resistance, which in turn affects the material's overall mechanical properties.

[0003] Cemented carbide is typically treated with a chemical vapor deposition (CVD) coating after sintering to enhance surface properties. However, in traditional CVD coating processes, hydrogen is used as a carrier gas, which reacts easily with carbon in the carbide at high temperatures, leading to surface decarburization and the formation of a continuous η phase (e.g., Co3W3C, Co6W6C, Co2W4C). This brittle continuous η phase exists at the film-substrate interface (i.e., between the substrate and coating), creating stress concentration points and crack sources, significantly reducing the bonding strength between the coating and the substrate. Furthermore, the unstable surface state of the decarburized phase is not conducive to the formation of a low-stress, high-bonding CVD coating.

[0004] Therefore, in order to solve the problem of decreased toughness and strength of cemented carbide after chemical vapor deposition, the usual means is to increase the total carbon in the alloy to compensate for the carbon loss after the coating is deposited on the substrate surface. High total carbon inside 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. Increasing the carbon content will narrow the two-phase zone, which brings certain difficulties to production control.

[0005] In existing technologies, some carburizing sintering processes introduce a carburizing atmosphere during the high-temperature stage. While this can replenish carbon, the rapid diffusion of carbon at high temperatures can easily lead to uneven carbon distribution or excessive carburization, and it is difficult to precisely control the carbon content on the surface and in the shallow layer. Furthermore, high-temperature carburization can exacerbate grain coarsening, impacting the overall performance of the alloy. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the present invention aims to provide a coated cemented carbide tool and a preparation method thereof.

[0007] According to the first aspect of the present invention, the present invention provides the following technical solutions: A coated cemented carbide cutting tool, 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 includes a core and a superficial layer covering the core, wherein the superficial layer is in direct contact with the coating; In the film-substrate interface region between the coating and the shallow surface layer (i.e., the interface region between the substrate and the coating), there is no η phase, or only a discontinuously distributed η phase with a maximum thickness of less than 1 μm exists; And the shallow layer meets the following conditions: In the shallow layer, a relatively high carbon layer is formed by carburization in the area close to the surface of the cemented carbide substrate, and the carbon content shows a decreasing gradient from the surface of the cemented carbide substrate to the core; In the shallow layer, a continuous solid solution phase with the characteristic structure of (Ti, Ta, Nb, Mo) C type compound cubic carbide is not formed; The mass fraction of the binder phase in the superficial layer is higher than that in the core.

[0008] As a preferred embodiment of the coated carbide tool of the present invention, the core satisfies the following conditions: The carbon content of the core in the WC / binder alloy two-phase region is 5.5-7.5 wt.%. Specifically, the carbon content of the core in the WC / binder alloy two-phase region can be, for example, any one of 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.%, and 7.5 wt.%, or a range between any two of the following: The core has the E0 or E02~E06 decarburization phase characteristics defined in GB / T 3488.4-2022 standard (Metallographic Determination of Cemented Carbide Microstructure).

[0009] As a preferred embodiment of the coated cemented carbide tool of the present invention, the cemented carbide substrate comprises the following components: TiC, content is 2~10 wt.%; One or more of Co and Ni, with a content of 5~10 wt.%; One or more of TiN and TiCN, with a content of 0.1~1 wt.%; One or more carbides of Ta, Nb, and Mo, with a content of 0 to 6 wt.%; WC, margin.

[0010] As a preferred embodiment of the coated cemented carbide tool described in the present invention, the total carbide content of Ti / Ta / Nb / Mo elements in the shallow surface layer is less than 0.5 wt.%, preferably less than 0.3 wt.%.

[0011] As a preferred embodiment of the coated cemented carbide tool described in the present invention, the thickness of the superficial layer is 2-50 μm; and the diffusion depth of carbon from the surface of the cemented carbide substrate to the core is 5-50 μm.

[0012] As a preferred embodiment of the coated cemented carbide tool of the present invention, the mass fraction of the binder phase in the superficial layer is 120-140% of the mass fraction of the binder phase in the core.

[0013] As a preferred embodiment of the coated cemented carbide tool described in the present invention, the coating is deposited on a shallow surface layer, and the coating includes a TiN layer, a TiCN layer, a TiCNO transition layer and an α-Al2O3 layer from the inside to the outside (i.e., from the surface of the cemented carbide substrate to the coating direction).

[0014] As a preferred embodiment of the coated carbide tool of the present invention, wherein: The TiN layer has an equiaxed crystal structure, a thickness of 0.1~2μm, and an average grain size of ≤0.4μm; The TiCN layer has a columnar crystal structure with a thickness of 1.5~10μm and an average grain size of 0.1~2μm; 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; The α-Al2O3 layer has an equiaxed crystal structure with a thickness of 2~10μm and an average grain size of 0.2~3μm.

[0015] As a preferred embodiment of the coated cemented carbide tool of the present invention, the saturation magnetization of the cemented carbide substrate is 65-80%, the coercive force is 100-400 Oe, the hardness HV30 is 1200-1700, and the fracture toughness is 8-18 MPa·m 1 / 2 , the average intercept of WC is 0.4~2.0μm, and the bonding force between the coating and the cemented carbide substrate is ≥80N (determined according to GB / T30707-2014 "Test method for bonding strength of fine ceramic coatings - scratch method" standard).

[0016] According to the second aspect of the present invention, the present invention provides the following technical solutions: A method for preparing the above-mentioned coated cemented carbide tool comprises the following steps: S1. Prepare raw material powder: prepare ingredients according to the cemented carbide matrix components, add a forming agent, adjust the total carbon content of the mixture, and then mix and granulate the mixture by ball milling to obtain raw material powder; S2, compression molding: the raw material powder prepared in step S1 is compression molded to obtain a cemented carbide compact; S3, vacuum dewaxing: placing the cemented carbide compact prepared in step S2 in a sintering furnace, heating to 250-300°C at a rate of 0.5-1.5°C / min under vacuum conditions below 200 Pa, and keeping the temperature for 120-180 min to complete dewaxing; S4. Vacuum sintering: Under vacuum conditions below 10Pa, heat to 1100℃ at 3~7℃ / min and keep warm for 5~30min; S5, atmosphere sintering: after step S4, nitrogen and argon (the volume ratio of nitrogen to argon is 1:2) are introduced into the furnace at 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 in the furnace is raised to 1420-1480°C at a rate of 3-8°C / min under the condition of 10-15 kPa in the furnace; S7, vacuum sintering: after step S6, keep the temperature at the sintering temperature for 20 to 60 minutes under vacuum conditions below 10 Pa; S8, vacuum sintering: after step S7, the temperature is lowered to 1370-1420°C under vacuum conditions below 10 Pa; S9, carburizing sintering: After step S8, carburizing gas and helium are introduced, wherein the carburizing gas includes one or more of CO, CH4, C2H2, and C2H4, and the helium content is 1-10 vol% of the total volume of the introduced gas, followed by holding at a pressure of 20-100 mbar for 40-90 minutes; S10, high pressure sintering: after step S9 is completed, vacuum treatment is carried out, and then argon gas is introduced to a pressure of 4-10 MPa and kept at this temperature for 30-60 minutes; S11, high-pressure cooling: after step S10 is completed, heating is stopped and the atmosphere pressure of step S10 is maintained and 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 using 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.

[0017] As a preferred embodiment of the method for preparing a coated cemented carbide tool according to the present invention, the ingredients are prepared according to the cemented carbide matrix components, specifically: TiC, content is 2~10 wt.%; One or more of Co and Ni, with a content of 5~10 wt.%; One or more of TiN and TiCN, with a content of 0.1~1 wt.%; One or more carbides of Ta, Nb, and Mo, with a content of 0 to 6 wt.%; WC, margin.

[0018] As a preferred embodiment of the method for preparing a coated cemented carbide tool described in the present invention, the particle size of WC is 2.0-6.0 μm, the particle size of TiC is 0.8-2.0 μm, the particle size of Co is 0.6-2.0 μm, the particle size of Ni is 0.6-2.0 μm, the particle size of TiN and / or TiCN is 0.8-1.5 μm, and the particle size of Ta, Nb and / or Mo carbides is 0.6-3.0 μm.

[0019] The beneficial effects of the present invention are as follows: The present invention provides a coated cemented carbide tool and a method for preparing the same. The cemented carbide substrate comprises a core and a shallow surface layer covering the core. The core comprises a hard zone having a lower limit of a two-phase region or a decarburized phase. While taking into account the hardness performance of the substrate, the shallow surface layer also comprises a tough zone rich in a bonding phase. This effectively avoids the problem of carbon loss on the surface of the cemented carbide substrate causing degradation of the tough zone performance of the substrate when depositing the coating on the substrate using a chemical vapor deposition method. Furthermore, because a continuous η phase that reduces brittleness is generated at the film-substrate interface between the coating and the shallow surface layer, stress concentration points and crack source distribution between the coating and the substrate are reduced, which facilitates the formation of a chemical vapor deposition coating with low internal stress and high bonding strength, significantly improving the bonding strength between the coating and the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0021] Figure 1 4 is a cross-sectional view of a coated cemented carbide tool according to Example 1 of the present invention.

[0022] Figure 2 4 is a cross-sectional view of a coated cemented carbide tool according to Example 2 of the present invention.

[0023] Figure 34 is a cross-sectional view of a coated cemented carbide tool according to Example 3 of the present invention.

[0024] Figure 4 4 is a cross-sectional view of the coated cemented carbide tool of Comparative Example 1 of the present invention.

[0025] In the figure, 1-coating, 2-superficial layer, 3-core, 4-η phase at the membrane-substrate interface.

[0026] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0027] The following will be a clear and complete description of the technical solutions in the embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] This invention proposes a coated cemented carbide tool and its preparation method. This method utilizes a one-step gradient sintering method to create a binder-rich, tough zone on the shallow surface of a cemented carbide substrate. Simultaneously, this binder-rich, tough zone is carburized during the liquid phase cooling phase. Carburization of the substrate surface and the shallow surface replenishes carbon loss, preventing the formation of a continuous decarburized phase. This provides a clean, decarburized-free film-substrate interface for subsequent chemical vapor deposition coatings. This clean, carbon-saturated surface reduces internal stress in the coating, extending its lifespan. Specific features are as follows: (1) In the present invention, under the condition that the cemented carbide is low in carbon as a whole and even has a decarburized phase, the cemented carbide is provided with good hardness and wear resistance; (2) In the present invention, the high binder phase mass fraction in the shallow surface layer is conducive to the diffusion of coating cracks into the substrate material during cutting, and the second carbide that migrates into the core maintains better high-temperature red hardness for the substrate material; (3) In the present invention, since the thermal conductivity of helium is significantly higher than that of argon, nitrogen, etc. (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 evenly transfer heat to all parts of the powder body, avoiding "overheating" or "underburning" caused by local temperature differences, reducing 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 in the shallow surface layer; (4) In the present invention, the high carbon content of the shallow surface layer avoids the serious degradation of substrate performance by the continuous η phase at the film-substrate interface generated by the carrier gas reaction in the chemical vapor deposition coating, reduces the stress concentration points and crack sources, and thus improves the bonding strength between the coating and the substrate.

[0029] The technical solution of the present invention is further described below with reference to specific embodiments.

[0030] Example 1 A method for preparing a coated cemented carbide tool comprises the following steps: S1. Prepare raw material powder: Prepare ingredients according to the cemented carbide matrix components, specifically: TiC, content is 2.5wt.%, Co, content is 6wt.%, TiN, content is 0.5wt.%, TaC, content is 5wt.%, and WC, balance; add 52# paraffin molding agent 2wt.%, total carbon content of the mixture is 5.88wt.%, and then mix by ball milling and granulation to obtain raw material powder; S2, compression molding: the raw material powder prepared in step S1 is compression molded to obtain a cemented carbide compact; S3, vacuum dewaxing: placing the cemented carbide compact prepared in step S2 in a sintering furnace, heating to 260°C at a rate of 1°C / min under a vacuum condition below 200 Pa, and keeping the temperature for 180 minutes to complete dewaxing; S4. Vacuum sintering: under vacuum conditions below 10 Pa, heat to 1100°C at 5°C / min and keep at this temperature for 30 minutes; S5, atmosphere sintering: after step S4, nitrogen and argon (nitrogen and argon volume ratio of 1:2) are introduced into the furnace at a pressure of 15 kPa, and the temperature is raised to 1270°C at a rate of 0.5°C / min; S6, atmosphere sintering: after step S5, the temperature in the furnace is raised to 1470°C at a rate of 5°C / min under the condition of 15kPa pressure; S7, vacuum sintering: after step S6, keep the temperature at the sintering temperature for 30 minutes under vacuum conditions below 10 Pa; S8, vacuum sintering: after step S7, the temperature is lowered to 1370°C under vacuum conditions below 10 Pa; S9, carburizing sintering: After step S8, carburizing gas and helium are introduced, wherein the carburizing gas is CH4 and the helium content is 5 vol% of the total volume of the introduced gas, followed by holding at a pressure of 40 mbar for 60 minutes; S10, high pressure sintering: after step S9 is completed, vacuum treatment is carried out, and then argon gas is introduced to a pressure of 6 MPa and kept at this temperature for 30 minutes; S11, high-pressure cooling: after step S10 is completed, heating is stopped and the atmosphere pressure of step S10 is maintained and 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 using chemical vapor deposition, which includes 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. The cross-sectional metallographic micrograph is shown in FIG. Figure 1 As shown, it can be seen that the distribution of the decarburized phase 4 in the film-base interface region between the coating 1 and the superficial layer 2 (the lower part of the superficial layer 2 is the core 3) of this embodiment is as follows: the η phase thickness is less than 1 μm, and the η phase in the interface region is discontinuous in the entire field of view.

[0031] Example 2 A method for preparing a coated cemented carbide tool comprises the following steps: S1. Prepare raw material powder: Prepare ingredients according to the cemented carbide matrix components, specifically: TiC, content is 2.5wt.%, Co, content is 6wt.%, TiN, content is 0.5wt.%, TaC, content is 5wt.%, and WC, balance; add 52# paraffin molding agent 2wt.%, total carbon content of the mixture is 5.88wt.%, and then mix by ball milling and granulation to obtain raw material powder; S2, compression molding: the raw material powder prepared in step S1 is compression molded to obtain a cemented carbide compact; S3, vacuum dewaxing: placing the cemented carbide compact prepared in step S2 in a sintering furnace, heating to 260°C at a rate of 1°C / min under a vacuum condition below 200 Pa, and keeping the temperature for 180 minutes to complete dewaxing; S4. Vacuum sintering: under vacuum conditions below 10 Pa, heat to 1100°C at 5°C / min and keep at this temperature for 30 minutes; S5, atmosphere sintering: after step S4, nitrogen and argon (nitrogen and argon volume ratio is 1:2) are introduced into the furnace at a pressure of 15 kPa, and the temperature is raised to 1300°C at a rate of 0.8°C / min; S6, atmosphere sintering: after step S5, the temperature is raised to 1450°C at a rate of 7.5°C / min under the condition of 15kPa in the furnace; S7, vacuum sintering: after step S6, keep the temperature at the sintering temperature for 45 minutes under vacuum conditions below 10 Pa; S8, vacuum sintering: after step S7, the temperature is lowered to 1400°C under vacuum conditions below 10 Pa; S9, carburizing sintering: After step S8, carburizing gas and helium are introduced, wherein the carburizing gas is CO and the helium content is 10 vol% of the total volume of the introduced gas, followed by holding at a pressure of 60 mbar for 40 minutes; S10, high pressure sintering: after step S9 is completed, vacuum treatment is carried out, and then argon gas is introduced to a pressure of 6 MPa and kept at this temperature for 30 minutes; S11, high-pressure cooling: after step S10 is completed, heating is stopped and the atmosphere pressure of step S10 is maintained and 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 using chemical vapor deposition, which includes 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. The cross-sectional metallographic micrograph is shown in FIG. Figure 2 As shown, it can be seen that the distribution of the decarburized phase 4 in the film-base interface region between the coating 1 and the superficial layer 2 (the lower part of the superficial layer 2 is the core 3) of this embodiment is as follows: the η phase thickness is less than 1 μm, and the η phase in the interface region is discontinuous in the entire field of view.

[0032] Example 3 A method for preparing a coated cemented carbide tool comprises the following steps: S1. Prepare raw material powder: Prepare ingredients according to the cemented carbide matrix components, specifically: TiC, content is 2.5wt.%, Co, content is 6wt.%, TiN, content is 0.5wt.%, TaC, content is 5wt.%, and WC, balance; add 56# paraffin molding agent 2wt.%, total carbon content of the mixture is 5.88wt.%, and then mix by ball milling and granulation to obtain raw material powder; S2, compression molding: the raw material powder prepared in step S1 is compression molded to obtain a cemented carbide compact; S3, vacuum dewaxing: placing the cemented carbide compact prepared in step S2 in a sintering furnace, heating to 280°C at a rate of 1°C / min under a vacuum condition below 200 Pa, and keeping the temperature for 150 minutes to complete dewaxing; S4. Vacuum sintering: under vacuum conditions below 10 Pa, heat to 1100°C at 3.5°C / min and keep at this temperature for 15 minutes; S5, atmosphere sintering: after step S4, nitrogen and argon (nitrogen and argon volume ratio is 1:2) are introduced into the furnace at a pressure of 10 kPa, and the temperature is raised to 1250°C at a rate of 1°C / min; S6, atmosphere sintering: after step S5, the temperature is raised to 1450°C at a rate of 3°C / min under the condition of 15kPa in the furnace; S7, vacuum sintering: after step S6, keep the temperature at the sintering temperature for 30 minutes under vacuum conditions below 10 Pa; S8, vacuum sintering: after step S7, the temperature is lowered to 1380°C under vacuum conditions below 10 Pa; S9, carburizing sintering: After step S8, carburizing gas and helium are introduced, wherein the carburizing gas includes CO and C2H2, and the helium content is 2 vol% of the total volume of the introduced gas, and then the temperature is kept at 20 mbar pressure for 90 minutes; S10, high pressure sintering: after step S9 is completed, vacuum treatment is carried out, and then argon gas is introduced to a pressure of 9 MPa and kept at this temperature for 30 minutes; S11, high-pressure cooling: after step S10 is completed, heating is stopped and the atmosphere pressure of step S10 is maintained and 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 using chemical vapor deposition, which includes 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. The cross-sectional metallographic micrograph is shown in FIG. Figure 3 As shown, it can be seen that the distribution of the decarburized phase 4 in the membrane-base interface region between the coating 1 and the superficial layer 2 (the lower part of the superficial layer 2 is the core 3) of this embodiment is: there is almost no η phase.

[0033] Example 4 A method for preparing a coated cemented carbide tool comprises the following steps: S1. Prepare raw material powder: prepare ingredients according to the cemented carbide matrix components, specifically: TiC, content is 4 wt.%, Co, content is 6 wt.%, TiN, content is 1 wt.%, TaC, content is 5 wt.%, Mo2C, content is 1 wt.%, and WC, balance; add 2 wt.% of 52# paraffin molding agent, and the total carbon content of the mixture is 5.88 wt.%, and then mix by ball milling and granulation to obtain raw material powder; S2, compression molding: the raw material powder prepared in step S1 is compression molded to obtain a cemented carbide compact; S3, vacuum dewaxing: placing the cemented carbide compact prepared in step S2 in a sintering furnace, heating to 260°C at a rate of 1°C / min under a vacuum condition below 200 Pa, and keeping the temperature for 180 minutes to complete dewaxing; S4. Vacuum sintering: under vacuum conditions below 10 Pa, heat to 1100°C at 5°C / min and keep at this temperature for 30 minutes; S5, atmosphere sintering: after step S4, nitrogen and argon (nitrogen and argon volume ratio of 1:2) are introduced into the furnace at a pressure of 15 kPa, and the temperature is raised to 1270°C at a rate of 0.5°C / min; S6, atmosphere sintering: after step S5, the temperature in the furnace is raised to 1470°C at a rate of 5°C / min under the condition of 15kPa pressure; S7, vacuum sintering: after step S6, keep the temperature at the sintering temperature for 30 minutes under vacuum conditions below 10 Pa; S8, vacuum sintering: after step S7, the temperature is lowered to 1370°C under vacuum conditions below 10 Pa; S9, carburizing sintering: After step S8, carburizing gas and helium are introduced, wherein the carburizing gas is CH4 and the helium content is 5 vol% of the total volume of the introduced gas, followed by holding at a pressure of 40 mbar for 60 minutes; S10, high pressure sintering: after step S9 is completed, vacuum treatment is carried out, and then argon gas is introduced to a pressure of 6 MPa and kept at this temperature for 30 minutes; S11, high-pressure cooling: after step S10 is completed, heating is stopped and the atmosphere pressure of step S10 is maintained and 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 using 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.

[0034] Example 5 A method for preparing a coated cemented carbide tool comprises the following steps: S1. Prepare raw material powder: Prepare ingredients according to the cemented carbide matrix components, specifically: TiC, content is 4 wt.%, Co, content is 6 wt.%, TiN, content is 1 wt.%, TaC, content is 5 wt.%, and WC, balance; add 2 wt.% of 52# paraffin molding agent, and the total carbon content of the mixture is 5.97 wt.%, and then mix by ball milling and granulation to obtain raw material powder; S2, compression molding: the raw material powder prepared in step S1 is compression molded to obtain a cemented carbide compact; S3, vacuum dewaxing: placing the cemented carbide compact prepared in step S2 in a sintering furnace, heating to 260°C at a rate of 1°C / min under a vacuum condition below 200 Pa, and keeping the temperature for 180 minutes to complete dewaxing; S4. Vacuum sintering: under vacuum conditions below 10 Pa, heat to 1100°C at 5°C / min and keep at this temperature for 30 minutes; S5, atmosphere sintering: after step S4, nitrogen and argon (nitrogen and argon volume ratio of 1:2) are introduced into the furnace at a pressure of 15 kPa, and the temperature is raised to 1270°C at a rate of 0.5°C / min; S6, atmosphere sintering: after step S5, the temperature in the furnace is raised to 1470°C at a rate of 5°C / min under the condition of 15kPa pressure; S7, vacuum sintering: after step S6, keep the temperature at the sintering temperature for 30 minutes under vacuum conditions below 10 Pa; S8, vacuum sintering: after step S7, the temperature is lowered to 1370°C under vacuum conditions below 10 Pa; S9, carburizing sintering: After step S8, carburizing gas and helium are introduced, wherein the carburizing gas is CH4 and the helium content is 5 vol% of the total volume of the introduced gas, followed by holding at a pressure of 40 mbar for 60 minutes; S10, high pressure sintering: after step S9 is completed, vacuum treatment is carried out, and then argon gas is introduced to a pressure of 6 MPa and kept at this temperature for 30 minutes; S11, high-pressure cooling: after step S10 is completed, heating is stopped and the atmosphere pressure of step S10 is maintained and 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 using 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.

[0035] Comparative Example 1 A method for preparing a coated cemented carbide tool comprises the following steps: S1. Prepare the ingredients according to the cemented carbide matrix components, specifically: TiC, content is 2.5 wt.%, Co, content is 6 wt.%, TiN, content is 0.5 wt.%, TaC, content is 5 wt.%, and WC, balance; add 52# paraffin molding agent 2 wt.%, the total carbon content of the mixture is 5.88 wt.%, and then mix by ball milling and granulation to obtain raw material powder; S2, pressing the raw material powder prepared in step S1 to obtain a cemented carbide compact; S3, placing the cemented carbide compact prepared in step S2 in a sintering furnace, heating to 260°C at a rate of 1°C / min under a vacuum condition below 200 Pa, and keeping the temperature for 180 minutes to complete dewaxing; S4. Under vacuum conditions below 10 Pa, heat to 1100°C at 5°C / min and keep warm for 15 minutes; S5. After step S4, nitrogen and argon (the volume ratio of nitrogen to argon is 1:2) are introduced into the furnace at a pressure of 15 kPa, and the temperature is raised to 1270°C at a rate of 0.5°C / min; S6. After step S5, the temperature in the furnace is raised to 1470° C. at a rate of 5° C. / min under the condition of 15 kPa in the furnace; S7, after step S6, argon gas is introduced to a pressure of 6 MPa and kept warm for 60 minutes; S8, after step S7 is completed, stop heating, maintain the atmosphere pressure of step S7 and cool to room temperature to obtain a cemented carbide substrate; S9, after step S8, a coating is deposited on the surface of the cemented carbide substrate by chemical vapor deposition, which includes 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. The cross-sectional metallographic micrograph is shown in FIG. Figure 4 As shown, it can be seen that the distribution of the decarburized phase 4 in the membrane-based interface region between the coating 1 and the superficial layer 2 (the lower part of the superficial layer 2 is the core 3) of this comparative example is: the thickness of the η phase is as high as 2.49 μm, and the η phase in the interface region exists continuously in the entire field of view.

[0036] Comparative Example 2 A method for preparing a coated cemented carbide tool comprises the following steps: S1. Prepare the ingredients according to the cemented carbide matrix components, specifically: TiC, content is 5 wt.%, Co, content is 8 wt.%, NbC, content is 4.5 wt.%, and WC, balance; add 52# paraffin molding agent 2 wt.%, the total carbon content of the mixture is 5.80 wt.%, and then mix by ball milling and granulation to obtain raw material powder; S2, pressing the raw material powder prepared in step S1 to obtain a cemented carbide compact; S3, placing the cemented carbide compact prepared in step S2 in a sintering furnace, heating to 260°C at a rate of 1°C / min under a vacuum condition below 200 Pa, and keeping the temperature for 180 minutes to complete dewaxing; S4. Under vacuum conditions below 10 Pa, heat to 1100°C at 5°C / min and keep warm for 15 minutes; S5. After step S4, argon gas is introduced into the furnace at a pressure of 15 kPa, and the temperature is raised to 1300° C. at a rate of 0.5° C. / min; S6. After step S5, the temperature in the furnace is raised to 1490° C. at a rate of 5° C. / min under the condition of 15 kPa in the furnace; S7, after step S6, argon gas is introduced to a pressure of 6 MPa and kept warm for 60 minutes; S8, after step S7 is completed, stop heating, maintain the atmosphere pressure of step S7 and cool to room temperature to obtain a cemented carbide substrate; S9. After step S8, a coating is deposited on the surface of the cemented carbide substrate using a chemical vapor deposition method, which includes 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.

[0037] The microstructure of the substrates of 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 substrate and its coating were tested, and the following parameter results were measured, as shown in the table below.

[0038] As can be seen from the above table, the performance of the coated cemented carbide cutting tools of the embodiments of the present invention is superior to that of the comparative examples. When the core hardness and toughness of the materials of the embodiments of the present invention and the comparative examples are similar, the WC hard grain size is comparable, and the overall material properties of the materials are maintained. However, the continuity of the η phase at the coating interface is significantly weaker than that of the comparative example (or even no η phase at the interface exists). The coating adhesion measured by scratch measurement is significantly higher than that of the comparative example. In actual cutting test applications, the main failure mode of the corresponding blades of the embodiments is coating wear, while a higher proportion of coating peeling occurs in the comparative example.

[0039] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A coated carbide tool, characterized in that: include: A cemented carbide substrate and a coating deposited on the surface of the cemented carbide substrate by chemical vapor deposition; The cemented carbide substrate includes a core and a superficial layer covering the core, wherein the superficial layer is in direct contact with the coating; In the film-based interface region between the coating and the superficial layer, there is no η phase, or only a discontinuously distributed η phase with a maximum thickness of less than 1 μm exists; And the shallow layer meets the following conditions: In the shallow layer, a relatively high carbon layer is formed by carburization in the area close to the surface of the cemented carbide substrate, and the carbon content shows a decreasing gradient from the surface of the cemented carbide substrate to the core; In the shallow layer, a continuous solid solution phase with the characteristic structure of (Ti, Ta, Nb, Mo) C type compound cubic carbide is not formed; The mass fraction of the binder phase in the superficial layer is higher than that in the core.

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

3. The coated carbide tool according to claim 1, characterized in that The cemented carbide substrate consists of the following components: TiC, content is 2~10 wt.%; One or more of Co and Ni, with a content of 5~10 wt.%; One or more of TiN and TiCN, with a content of 0.1~1 wt.%; One or more carbides of Ta, Nb, and Mo, with a content of 0 to 6 wt.%; WC, margin.

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

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

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

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

8. The coated carbide tool according to claim 7, characterized in that: The TiN layer has an equiaxed crystal structure, a thickness of 0.1~2μm, and an average grain size of ≤0.4μm; The TiCN layer has a columnar crystal structure with a thickness of 1.5~10μm and an average grain size of 0.1~2μm; 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; The α-Al2O3 layer has an equiaxed crystal structure with a thickness of 2~10μm and an average grain size of 0.2~3μm.

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

10. A method for preparing a coated cemented carbide tool according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Prepare raw material powder: prepare ingredients according to the cemented carbide matrix components, and then mix and granulate to obtain raw material powder; S2, compression molding: the raw material powder prepared in step S1 is compression molded to obtain a cemented carbide compact; S3, vacuum dewaxing: placing the cemented carbide compact prepared in step S2 in a sintering furnace, keeping it warm under vacuum conditions, and completing dewaxing; S4, vacuum sintering: sintering under vacuum conditions; S5, atmosphere sintering: after step S4, nitrogen and argon with a volume ratio of 1:2 are introduced into the furnace at 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 in the furnace is raised to 1420-1480°C at a rate of 3-8°C / min under the condition of 10-15 kPa in the furnace; S7, vacuum sintering: after step S6, keep the temperature at the sintering temperature for 20 to 60 minutes under vacuum conditions below 10 Pa; S8, vacuum sintering: after step S7, the temperature is lowered to 1370-1420°C under vacuum conditions below 10 Pa; S9, carburizing sintering: After step S8, carburizing gas and helium are introduced, wherein the carburizing gas includes one or more of CO, CH4, C2H2, and C2H4, and the helium content is 1-10 vol% of the total volume of the introduced gas, followed by holding at a pressure of 20-100 mbar for 40-90 minutes; S10, high pressure sintering: after step S9 is completed, vacuum treatment is carried out, and then argon gas is introduced to a pressure of 4-10 MPa and kept at this temperature for 30-60 minutes; S11, high-pressure cooling: after step S10 is completed, heating is stopped and the atmosphere pressure of step S10 is maintained and 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 using 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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