A coated cutting tool suitable for machining of titanium alloys and a method of making the same

Abstract

The application belongs to the field of cutting tool production and manufacturing, and particularly relates to a coating tool suitable for titanium alloy machining and a preparation method thereof. a Al b N c coating and a (Cr x Al y B z )N coating, the CrB2 / Cr a Al b N c coating is composed of a CrB2 sublayer / Cr a Al b N c sublayer composite structure unit cycle, the CrB2 sublayer / Cr a Al b N c sublayer composite structure unit comprises a CrB2 sublayer, a Cr a Al b N c sublayer, the number of cycles is 1 to 4, the CrN coating, the Cr-B-N coating, the CrB2 / Cr a Al b N c coating and the (Cr x Al y B z )N coating are all prepared by a chemical vapor deposition method. The application combines the substrate toughening process optimization and the multi-layer composite coating with a specific composition prepared by CVD, significantly improves the adhesion, hardness, wear resistance, high-temperature oxidation resistance and anti-bonding performance of the coating and the substrate, and effectively solves the problems of easy oxidation, bonding wear and edge collapse of the tool in the titanium alloy machining process.

Description

Technical Field

[0001] This application relates to the field of cutting tool manufacturing, specifically to a coated cutting tool suitable for machining titanium alloys and its preparation method. Background Technology

[0002] Titanium alloys possess excellent strength-to-weight ratio, corrosion resistance, and high-temperature performance, making them widely used in aerospace, medical, and other fields. However, these characteristics also increase the difficulty of machining them. First, their poor thermal conductivity causes heat to concentrate in the tool-workpiece contact area during cutting, accelerating tool wear and shortening tool life. Second, titanium alloys have a low elastic modulus, making them prone to tool deflection during machining, affecting dimensional accuracy and potentially causing vibration. Third, titanium alloys exhibit high chemical reactivity at high temperatures, easily adhering to tool materials, exacerbating tool wear and affecting surface quality. Furthermore, their significant work hardening tendency leads to increased cutting forces, drastically reducing tool life. To address these challenges, titanium alloy cutting tool materials require high hardness and wear resistance, good anti-adhesive wear capability and surface quality, as well as good impact resistance and film adhesion.

[0003] Currently, most cutting tools employ physical vapor deposition (PVD) coatings to meet the needs of titanium alloy machining applications, primarily because it facilitates the preparation of TiB2 and Cr coatings. a Al b N c High-hardness materials are used to improve the coating's resistance to high-temperature oxidation, while a high-cobalt content matrix is ​​combined to enhance the tool's impact resistance. However, coatings prepared using physical vapor deposition (PVD) have the following problems: First, the adhesion is poor, and the coating is prone to peeling under high-speed milling; second, the aluminum content in PVD-prepared aluminum-containing coatings does not exceed 70%, which still limits the coating's resistance to high-temperature oxidation; third, TiB2 coatings do not have good oxidation resistance, and Cr... a Al b N c While coatings offer some oxidation resistance, they have a high affinity for titanium alloys, making them prone to adhesive wear and other problems. Therefore, a coated cutting tool with strong adhesion, high wear resistance, excellent oxidation resistance, and anti-adhesion properties is needed. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a coated cutting tool suitable for machining titanium alloys, wherein the coated cutting tool comprises, from the inside out: a toughened substrate, a CrN coating, a Cr-BN coating, and a CrB2 / Cr coating. a Al b N c Coating and (Cr) x Al y B z)N coating, the CrB2 / Cr a Al b N c The coating consists of a CrB2 sublayer / Cr a Al b N c The sublayer composite structure is composed of cyclically stacked sublayers, wherein the CrB2 sublayer / Cr a Al b N c The sublayer composite structural unit includes CrB2 sublayer, Cr a Al b N c Sublayers, the number of cycles is 1 to 4, the CrN coating, the Cr-BN coating, the CrB2 / Cr a Al b N c Coating and the (Cr) x Al y B z The N coatings were all prepared using chemical vapor deposition.

[0005] As a preferred embodiment of the coated cutting tool suitable for machining titanium alloys described in this application, the CrN coating, the Cr-BN coating, and the CrB2 / Cr coating are preferred embodiments. a Al b N c Coating and the (Cr) x Al y B z The total thickness of the N coating is 7.0-10.7 μm.

[0006] As a preferred embodiment of the coated cutting tool suitable for machining titanium alloys described in this application, the thickness of the CrN coating is 0.5-1.0 μm; the thickness of the Cr-BN coating is 0.5-1.0 μm; the single-layer thickness of the CrB2 sublayer is 1.5-2.5 μm; and the Cr... a Al b N c The thickness of the sublayer monolayer is 0.8-1.5 μm; the (Cr) x Al y B z The thickness of the N coating is 0.5-1.0 μm.

[0007] As a preferred embodiment of the coated cutting tool suitable for machining titanium alloys described in this application, the content of element B in the Cr-BN coating, by atomic percentage, continuously increases from 0.1at%-1at% at the inner interface adjacent to the CrN coating to the content of element B in the CrB2 / Cr coating. a Al b Nc The Cr-BN coating, with an outer interface adjacent to the coating, is 10 at%-15 at%. The Cr-BN coating is composed of a Cr-B phase, a Cr-N phase, and a BN phase. The Cr-B phase contains at least one of CrB2 and Cr2B, the Cr-N phase contains at least one of CrN and Cr2N, and the BN phase contains at least one of cubic boron nitride c-BN and hexagonal boron nitride h-BN.

[0008] As a preferred embodiment of the coated cutting tool suitable for machining titanium alloys described in this application, the CrB2 sublayer is columnar nanocrystals, and the grain size of the CrB2 sublayer is ≤20nm; the Cr a Al b N c The ratio of a, b, and c in the sublayer is (0.26-0.33): (0.45-0.57): (0.15-0.24).

[0009] As a preferred embodiment of the coated cutting tool suitable for machining titanium alloys described in this application, the (Cr) x Al y B z The ratio of x, y, z in the N coating is (0.2-0.3):(0.7-0.6):0.1; the (Cr) coating... x Al y B z The N coating can form a dense Al2O3 and B2O3 composite oxide film on the surface under high cutting temperatures.

[0010] As a preferred embodiment of the coated cutting tool suitable for machining titanium alloys described in this application, the coated cutting tool has the following properties: coating hardness ≥30GPa and overall adhesion force ≥100N.

[0011] This application also provides a method for preparing a coated cutting tool suitable for titanium alloy machining. The method comprises the following steps: S1, obtaining a tool substrate and toughening the tool substrate to obtain the toughened substrate; S2, depositing a CrN layer on the toughened substrate to obtain a CrN-coated cutting tool, wherein the CrN coating is deposited on the surface of the toughened substrate; S3, depositing a Cr-BN layer on the CrN-coated cutting tool to obtain a Cr-BN-coated cutting tool, wherein the Cr-BN coating is deposited on the surface of the CrN-coated cutting tool; S4, performing a CrB2 / Cr... a Al b N c Layer deposition yielded CrB2 / Cr a Al b N cLayered cutting tool, wherein the Cr-BN layered cutting tool surface is deposited with the CrB2 / Cr a Al b N c Coating; S5, for the CrB2 / Cr a Al b N c Layered cutting tool (Cr) x Al y B z The coated tool is obtained by depositing an N-layer, namely CrB2 / Cr a Al b N c The surface of the layered cutting tool was deposited with the (Cr) x Al y B z The CrN coating, from the inside out, comprises: the toughened substrate, the CrN coating, the Cr-BN coating, and the CrB2 / Cr coating. a Al b N c Coating and the (Cr) x Al y B z N coating.

[0012] As a preferred embodiment of the method for preparing a coated cutting tool suitable for machining titanium alloys as described in this application, in step S1, the tool substrate is a WC-Co cemented carbide, the WC-Co cemented carbide contains carbide solid solution grains of Ta and Nb elements, the average grain size of WC in the WC-Co cemented carbide is 1.1-2.3 μm; the maximum pore size in the WC-Co cemented carbide is <1 μm; the WC-Co cemented carbide, by mass percentage, has the following contents: Co content is 8.0-9.5 wt%, Ta content is 0.5-2.6 wt%, Nb content is 0.2-1.0 wt%, and the balance is WC; the hardness of the WC-Co cemented carbide is ≥1250 HV, and the fracture toughness KIC of the WC-Co cemented carbide is ≥18 MPa•m. 1 / 2 The toughening treatment specifically involves: applying a vacuum of 1×10⁻⁶. -2 Hold at 800-1000℃ for 30-90 minutes, then cool to below 700℃ at a cooling rate of not less than 5℃ / min.

[0013] As a preferred embodiment of the method for preparing a coated cutting tool suitable for titanium alloy machining as described in this application, in step S2, the CrN layer is deposited by depositing the CrN coating on the toughened substrate surface through a chemical reaction of H2, CrCl3, and NH3 at 700-800℃ and 5-15mbar; in step S3, the Cr-BN layer is deposited by depositing the Cr-BN coating on the CrN-coated cutting tool surface through a chemical reaction of introducing BCl3 into a reaction atmosphere of H2, CrCl3, and NH3 and dynamically increasing its flow rate, with the B element content increasing continuously from the inside to the outside; in step S4, the CrB2 / Cr a Al b N c The specific deposition method is as follows: under conditions of 700-800℃ and 5-15mbar, the following sequential cycles are performed: the CrB2 sublayer is deposited through a chemical reaction of H2, CrCl3, BCl3, and Ar; the Cr sublayer is deposited through a chemical reaction of H2, CrCl3, AlCl3, NH3, and Ar. a Al b N c Sub-layer; wherein the number of cycles is 1 to 4; in step S5, the (Cr x Al y B z The N-layer deposition method specifically involves: under conditions of 800-900℃ and 10-20 mbar, the N-layer is deposited through a chemical reaction of H2, CrCl3, AlCl3, BCl3, NH3, and Ar on the CrB2 / Cr... a Al b N c The (Cr) layer tool surface is deposited x Al y B z N coating.

[0014] The beneficial effects of this application are as follows:

[0015] This application proposes a method for preparing coated cutting tools suitable for titanium alloy machining. By combining an optimized substrate toughening process with a multilayer composite coating of a specific composition prepared by chemical vapor deposition (CVD), this application significantly improves the adhesion between the coating and the substrate, the hardness, wear resistance, high-temperature oxidation resistance, and anti-adhesion properties of the coating. This effectively solves the technical problems of excessively rapid oxidation, adhesive wear, and chipping of cutting tools during titanium alloy machining.

[0016] The specific features are as follows:

[0017] 1. Prior to coating deposition, this application employs a specialized vacuum toughening treatment on the cemented carbide substrate. This process effectively optimizes the grain boundary structure of the substrate, reduces surface fragments, and ensures grain integrity, thereby providing a superior foundation for subsequent coatings and significantly improving the film-substrate bonding strength.

[0018] 2. This application uses chemical vapor deposition (CVD) to prepare the CrN bonding layer. The CVD method not only allows Cr to fully dissolve with elements such as Co in the matrix to form a strong metallurgical bond, but also, compared with the CrN coating prepared by physical vapor deposition (PVD), it has better toughness and impact resistance, and can effectively buffer the severe stress generated during high-speed milling of titanium alloys.

[0019] 3. By introducing a Cr-BN boron gradient stress-relieving transition layer with a continuously varying boron content between the CrN bonding layer and the outer layer, the problem of lattice distortion and stress concentration caused by the large difference in lattice constant between the CrN bonding layer and the subsequent CrB2 sublayer in the face-centered cubic (FCC) structure is cleverly solved. This boron gradient stress-relieving transition layer achieves a smooth transition from Cr-N bonds to BN bonds and Cr-B bonds, avoiding bond weakening and forming a stronger chemical bonding interface.

[0020] 4. The CrB2 sublayer prepared by chemical vapor deposition (CVD) in this application has extremely high hardness, while the Cr sublayer prepared by the same chemical vapor deposition (CVD) also has very high hardness. a Al b N c The sublayer can achieve a higher Al content, thus obtaining better high-temperature oxidation resistance. By alternately compounding the two in a nano-multilayer structure, the difference in their crystal structure generates lattice distortion at the interface. This internal stress can effectively hinder dislocation movement and crack propagation, synergistically improving the overall macroscopic hardness, yield strength and crack propagation resistance of the coating.

[0021] 5.(Cr x Al y B z Under high cutting temperatures, the Al and B elements in the N-type anti-oxidation surface layer can combine with oxygen to form a dense Al2O3 and a lubricating B2O3 composite oxide film, respectively. This composite film not only further enhances the coating's anti-oxidation ability but also achieves surface self-lubrication, effectively reducing the coefficient of friction and chemical affinity with the titanium alloy workpiece, thereby significantly inhibiting adhesive wear. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application 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 this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the coating cross-sectional structure of a coated cutting tool suitable for machining titanium alloys according to this application;

[0024] Figure 2 This is a scanning electron microscope image of the matrix before toughening in Example 1 of this application;

[0025] Figure 3 This is a scanning electron microscope image of the toughened matrix of Example 1 in this application;

[0026] Figure 4 This is a scanning electron microscope image of the coating prepared in Example 1 of this application;

[0027] Figure 5 The images show the wear test results of the cutting tools prepared in Examples 1, 1, 2, 6, and 7 of this application.

[0028] Figure 1 Chinese markings: 100, toughened matrix; 200, CrN coating; 300, Cr-BN coating; 400, CrB2 / Cr a Al b N c Coating; 410, CrB2 sublayer / Cr a Al b N c Sublayer composite structural unit; 411, CrB2 sublayer; 412, Cr a Al b N c Sublayer; 500, (Cr) x Al y B z N coating.

[0029] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0030] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0031] Please see Figure 1 This application provides a coated cutting tool suitable for machining titanium alloys, comprising, from the inside out: a toughened substrate 100, a CrN coating 200, a Cr-BN coating 300, and a CrB2 / Cr coating. a Al b N c Coating 400 and (Cr) x Al y B z )N coating 500, the CrB2 / Cr a Al b N c Coating 400 consists of CrB2 sublayer / Cr a Al b N c The sublayer composite structural unit 410 is composed of cyclic superposition, wherein the CrB2 sublayer / Cr a Al b N c Sublayer composite structural unit 410 includes CrB2 sublayer 411, Cr a Al b N c Sub-layer 412, the number of cycles is 1 to 4.

[0032] This application also provides a method for preparing a coated cutting tool suitable for machining titanium alloys, comprising the following steps:

[0033] S1. Obtain the tool substrate and toughen the tool substrate to obtain a toughened substrate;

[0034] The tool matrix is ​​WC-Co cemented carbide, which contains carbide solid solution grains of Ta and Nb elements. The average grain size of WC in the WC-Co cemented carbide is 1.1-2.3 μm; the maximum pore size in the WC-Co cemented carbide is <1 μm; the WC-Co cemented carbide, by mass percentage, contains 8.0-9.5 wt% Co, 0.5-2.6 wt% Ta, 0.2-1.0 wt% Nb, with the balance being WC; the hardness of the WC-Co cemented carbide is ≥1250 HV, and the fracture toughness KIC of the WC-Co cemented carbide is ≥18 MPa•m. 1 / 2 The toughening treatment specifically involves: applying a vacuum of 1×10⁻⁶.-2 Hold at 800-1000℃ for 30-90 minutes, then cool to below 700℃ at a cooling rate of not less than 5℃ / min.

[0035] S2. A CrN layer is deposited on the toughened substrate to obtain a CrN layer tool, wherein a CrN coating is deposited on the surface of the toughened substrate.

[0036] The CrN layer is deposited by depositing the CrN coating on the toughened substrate surface through a chemical reaction of H2, CrCl3, and NH3 at 700-800℃ and 5-15mbar.

[0037] S3. A Cr-BN layer is deposited on the CrN layer tool to obtain a Cr-BN layer tool, wherein a Cr-BN coating is deposited on the surface of the CrN layer tool.

[0038] The Cr-BN layer deposition method is as follows: under the conditions of 700-800℃ and 5-15mbar, BCl3 is introduced into the reaction atmosphere of H2, CrCl3 and NH3 and its flow rate is dynamically increased through a chemical reaction to deposit the Cr-BN coating on the surface of the CrN layer tool with the B element content continuously increasing from the inside to the outside.

[0039] S4. Perform CrB2 / Cr on the Cr-BN layer tool. a Al b N c Layer deposition yielded CrB2 / Cr a Al b N c Layered cutting tool, wherein the surface of the Cr-BN layered cutting tool is deposited with CrB2 / Cr a Al b N c The coating, the CrB2 / Cr a Al b N c The coating consists of a CrB2 sublayer and a Cr layer. a Al b N c Sub-layer;

[0040] The CrB2 / Cr a Al b N c The specific deposition method is as follows: under conditions of 700-800℃ and 5-15mbar, the following sequential cycles are performed: the CrB2 sublayer is deposited through a chemical reaction of H2, CrCl3, BCl3, and Ar; the Cr sublayer is deposited through a chemical reaction of H2, CrCl3, AlCl3, NH3, and Ar. a Alb N c Sub-layer; wherein the number of iterations is 1 to 4;

[0041] S5, regarding the CrB2 / Cr a Al b N c Layered cutting tool (Cr) x Al y B z The coated tool is obtained by depositing an N-layer, namely CrB2 / Cr a Al b N c The surface of the cutting tool was deposited with (Cr) x Al y B z The CrN coating, from the inside out, comprises: the toughened substrate, the CrN coating, the Cr-BN coating, and the CrB2 / Cr coating. a Al b N c Coating and the (Cr) x Al y B z N coating;

[0042] The (Cr) x Al y B z The N-layer deposition method specifically involves: under conditions of 800-900℃ and 10-20 mbar, the N-layer is deposited through a chemical reaction of H2, CrCl3, AlCl3, BCl3, NH3, and Ar on the CrB2 / Cr... a Al b N c The (Cr) layer tool surface is deposited x Al y B z N coating.

[0043] The technical solution of this application will be further described below with reference to specific embodiments.

[0044] Example 1

[0045] This application provides a method for preparing a coated cutting tool suitable for machining titanium alloys, comprising the following steps:

[0046] S1. Obtain the tool substrate. The tool model is APMT1135PDER carbide end mill. The tool substrate is toughened to obtain a toughened substrate. The toughening treatment method is as follows: under a vacuum degree of 1×10⁻⁶... -2The tool was held at 1000℃ for 30 minutes, then cooled to below 700℃ at a rate of 10℃ / min. The tool matrix was WC-Co cemented carbide, containing Ta and Nb carbide solid solution grains. The average grain size of WC in the WC-Co cemented carbide was 2.3 μm, and the maximum pore size was <1 μm. The WC-Co cemented carbide, by mass percentage, contained 9.5 wt% Co, 0.5 wt% Ta, 1.0 wt% Nb, with the balance being WC. The WC-Co cemented carbide had a hardness of 1250 HV and a fracture toughness (KIC) of 20 MPa•m. 1 / 2 ;

[0047] S2. A CrN layer was deposited on the toughened substrate to obtain a CrN layer tool. The CrN layer was deposited by depositing a CrN coating on the surface of the toughened substrate through a chemical reaction of H2, CrCl3 and NH3 at 700℃ and 15mbar. A 1.0μm thick CrN coating was deposited on the surface of the toughened substrate.

[0048] S3. A Cr-BN layer was deposited on the CrN-layered tool to obtain a Cr-BN-layered tool. The specific deposition method was as follows: under conditions of 700℃ and 15mbar, a chemical reaction was carried out by introducing BCl3 into a reaction atmosphere of H2, CrCl3, and NH3, with the flow rate dynamically increasing. This resulted in the deposition of a Cr-BN coating on the CrN-layered tool surface with a continuously increasing B element content from the inside out. A 1.0μm thick Cr-BN coating was deposited on the CrN-layered tool surface. The B element content continuously increased from 1.0 at% at the inner interface adjacent to the CrN coating to the CrB2 / Cr... a Al b N c At 15 at% of the adjacent outer interface of the coating, the Cr-BN coating is composed of Cr-B phase, Cr-N phase and BN phase. The Cr-B phase is CrB2, the Cr-N phase is CrN and the BN phase is cubic boron nitride c-BN.

[0049] S4. Apply CrB2 / Cr to the Cr-BN layer tool. 0.26 Al 0.50 N 0.24 Layer deposition yielded CrB2 / Cr 0.26 Al 0.50 N 0.24 Layer cutting tool, CrB2 / Cr 0.26 Al 0.50 N 0.24The specific deposition method is as follows: under conditions of 750℃ and 10mbar, the following sequential cycles are performed: a CrB2 sublayer is deposited through a chemical reaction of H2, CrCl3, BCl3, and Ar; a Cr sublayer is deposited through a chemical reaction of H2, CrCl3, AlCl3, NH3, and Ar. 0.26 Al 0.50 N 0.24 Sublayer; Cr-BN layer: CrB2 / Cr is deposited on the tool surface. 0.26 Al 0.50 N 0.24 Coating; wherein, CrB2 / Cr 0.26 Al 0.50 N 0.24 The coating consists of a 2.5 μm thick CrB2 sublayer and a 1.5 μm thick Cr... 0.26 Al 0.50 N 0.24 Sublayer; CrB2 / Cr 0.26 Al 0.50 N 0.24 The coating consists of a CrB2 sublayer / Cr 0.26 Al 0.50 N 0.24 The sublayer composite structure is composed of cyclic superposition of units, with a cycle of 1 time; the CrB2 sublayer is columnar nanocrystals with a grain size of 15 nm;

[0050] S5, for CrB2 / Cr 0.26 Al 0.50 N 0.24 Layered cutting tool (Cr) 0.3 Al 0.6 B 0.1 N-layer deposition yields coated cutting tools, (Cr) 0.3 Al 0.6 B 0.1 The N-layer deposition method specifically involves the chemical reaction of H2, CrCl3, AlCl3, BCl3, NH3, and Ar in a CrB2 / Cr layer at 850℃ and 15mbar. 0.26 Al 0.50 N 0.24 Layered tool surface deposition (Cr) 0.3 Al 0.6 B 0.1 N coating; CrB2 / Cr 0.26 Al 0.50 N 0.24 A 1.0 μm thick layer of (Cr) was deposited on the surface of the cutting tool. 0.3 Al 0.6 B 0.1 N coating;

[0051] The coated cutting tools, from the inside out, consist of: toughened substrate, CrN coating, Cr-BN coating, and CrB2 / Cr. 0.26 Al 0.50 N 0.24 Coating and (Cr) 0.3 Al 0.6 B 0.1 The coating has a total thickness of 7μm, a hardness of 32GPa, and an overall adhesion of 125N.

[0052] Please see Figure 2 and Figure 3 , Figure 2 This is a scanning electron microscope image of the matrix before toughening in Example 1 of this application. Figure 3 This is a scanning electron microscope image of the matrix after toughening in Example 1 of this application; please refer to... Figure 4 , Figure 4 This is a scanning electron microscope image of the coating prepared in Example 1 of this application.

[0053] Example 2

[0054] This application provides a method for preparing a coated cutting tool suitable for machining titanium alloys, comprising the following steps:

[0055] S1. Obtain the tool substrate. The tool model is XNMU070508-MME carbide end mill. The tool substrate is toughened to obtain a toughened substrate. The toughening treatment method is as follows: under a vacuum degree of 1×10⁻⁶… -2 The tool was held at 900℃ for 60 minutes, then cooled to below 700℃ at a rate of 6℃ / min. The tool matrix was WC-Co cemented carbide, containing Ta and Nb carbide solid solution grains. The average grain size of WC in the WC-Co cemented carbide was 2.0 μm, and the maximum pore size was <1 μm. The WC-Co cemented carbide, by mass percentage, contained 8.5 wt% Co, 1.5 wt% Ta, and 0.5 wt% Nb, with the balance being WC. The WC-Co cemented carbide had a hardness of 1350 HV and a fracture toughness (KIC) of 19.5 MPa•m. 1 / 2 ;

[0056] S2. A CrN layer is deposited on the toughened substrate to obtain a CrN layer tool. The CrN layer is deposited by depositing a CrN coating on the surface of the toughened substrate through a chemical reaction of H2, CrCl3 and NH3 at 750℃ and 10mbar. A 0.5μm thick CrN coating is deposited on the surface of the toughened substrate.

[0057] S3. A Cr-BN layer was deposited on the CrN-layered tool to obtain a Cr-BN-layered tool. The specific deposition method was as follows: under conditions of 750℃ and 10 mbar, a chemical reaction was carried out by introducing BCl3 into a reaction atmosphere of H2, CrCl3, and NH3, with the flow rate dynamically increasing. This resulted in the deposition of a Cr-BN coating on the CrN-layered tool surface with a continuously increasing B element content from the inside out. A 0.5 μm thick Cr-BN coating was deposited on the CrN-layered tool surface. The B element content continuously increased from 0.6 at% at the inner interface adjacent to the CrN coating to the CrB2 / Cr... a Al b N c At 13 at% of the adjacent outer interface of the coating, the Cr-BN coating is composed of Cr-B phase, Cr-N phase and BN phase. The Cr-B phase is CrB2 and Cr2B, the Cr-N phase is CrN, and the BN phase is cubic boron nitride c-BN and hexagonal boron nitride h-BN.

[0058] S4. Apply CrB2 / Cr to the Cr-BN layer tool. 0.33 Al 0.45 N 0.22 Layer deposition yielded CrB2 / Cr 0.33 Al 0.45 N 0.22 Layer cutting tool, CrB2 / Cr 0.33 Al 0.45 N 0.22 The specific deposition method is as follows: under conditions of 800℃ and 5mbar, the following sequential cycles are performed: a CrB2 sublayer is deposited through a chemical reaction of H2, CrCl3, BCl3, and Ar; a Cr sublayer is deposited through a chemical reaction of H2, CrCl3, AlCl3, NH3, and Ar. 0.33 Al 0.45 N 0.22 Sublayer; Cr-BN layer: CrB2 / Cr is deposited on the tool surface. 0.33 Al 0.45 N 0.22 Coating; wherein, CrB2 / Cr 0.33 Al 0.45 N 0.22 The coating consists of a 1.5 μm thick CrB2 sublayer and a 0.8 μm thick Cr... 0.33 Al 0.45 N 0.22 Sublayer; CrB2 / Cr 0.33 Al 0.45 N 0.22 Coating CrB2 sublayer / Cr 0.33 Al 0.45 N 0.22The sublayer composite structure is composed of cyclic superposition of units, with a cycle of 4 times; the CrB2 sublayer is columnar nanocrystals with a grain size of 18 nm;

[0059] S5, for CrB2 / Cr 0.33 Al 0.45 N 0.22 Layered cutting tool (Cr) 0.25 Al 0.65 B 0.1 N-layer deposition yields coated cutting tools, (Cr) 0.25 Al 0.65 B 0.1 The N-layer deposition method is as follows: under conditions of 800℃ and 20mbar, the N-layer is deposited on CrB2 / Cr through a chemical reaction of H2, CrCl3, AlCl3, BCl3, NH3, and Ar. 0.33 Al 0.45 N 0.22 Layered tool surface deposition (Cr) 0.25 Al 0.65 B 0.1 N coating; CrB2 / Cr 0.33 Al 0.45 N 0.22 A 0.5 μm thick layer of (Cr) was deposited on the surface of the cutting tool. 0.25 Al 0.65 B 0.1 N coating;

[0060] The coated cutting tools, from the inside out, consist of: toughened substrate, CrN coating, Cr-BN coating, and CrB2 / Cr. 0.33 Al 0.45 N 0.22 Coating and (Cr) 0.25 Al 0.65 B 0.1 The coating has a total thickness of 10.7 μm, a hardness of 30.5 GPa, and an overall adhesion of 102 N.

[0061] Example 3

[0062] This application provides a method for preparing a coated cutting tool suitable for machining titanium alloys, comprising the following steps:

[0063] S1. Obtain the tool substrate. The tool model is RPHT1204M8E-MM3 carbide end mill. The tool substrate is toughened to obtain a toughened substrate. The toughening treatment method is as follows: under a vacuum degree of 1×10⁻⁶... -2The tool was held at 800℃ for 90 minutes, then cooled to below 700℃ at a rate of 8℃ / min. The tool matrix was WC-Co cemented carbide, containing Ta and Nb carbide solid solution grains. The average grain size of WC in the WC-Co cemented carbide was 1.1 μm, and the maximum pore size was <1 μm. The WC-Co cemented carbide, by mass percentage, contained 8.0 wt% Co, 2.6 wt% Ta, and 0.2 wt% Nb, with the balance being WC. The WC-Co cemented carbide had a hardness of 1400 HV and a fracture toughness (KIC) of 18.5 MPa•m. 1 / 2 ;

[0064] S2. A CrN layer is deposited on the toughened substrate to obtain a CrN layer tool. The CrN layer deposition method is as follows: under the conditions of 800℃ and 5mbar, a CrN coating is deposited on the surface of the toughened substrate through the chemical reaction of H2, CrCl3 and NH3; a CrN coating with a thickness of 0.7μm is deposited on the surface of the toughened substrate.

[0065] S3. A Cr-BN layer was deposited on the CrN-layered tool to obtain a Cr-BN-layered tool. The specific deposition method was as follows: under conditions of 800℃ and 5 mbar, a chemical reaction was carried out by introducing BCl3 into a reaction atmosphere of H2, CrCl3, and NH3, with the flow rate dynamically increasing. This resulted in the deposition of a Cr-BN coating on the CrN-layered tool surface with a continuously increasing B element content from the inside out. A 0.7 μm thick Cr-BN coating was deposited on the CrN-layered tool surface. The B element content continuously increased from 0.1 at% at the inner interface adjacent to the CrN coating to the CrB2 / Cr... a Al b N c At 10 at% of the adjacent outer interface of the coating, the Cr-BN coating is composed of Cr-B phase, Cr-N phase and BN phase. The Cr-B phase is CrB2 and Cr2B, the Cr-N phase is CrN and Cr2N, and the BN phase is cubic boron nitride c-BN and hexagonal boron nitride h-BN.

[0066] S4. Apply CrB2 / Cr to the Cr-BN layer tool. 0.28 Al 0.57 N 0.15 Layer deposition yielded CrB2 / Cr 0.28 Al 0.57 N 0.15 Layer cutting tool, CrB2 / Cr 0.28 Al 0.57 N 0.15The specific deposition method is as follows: under conditions of 700℃ and 15mbar, the following sequential cycles are performed: a CrB2 sublayer is deposited through a chemical reaction of H2, CrCl3, BCl3, and Ar; a Cr sublayer is deposited through a chemical reaction of H2, CrCl3, AlCl3, NH3, and Ar. 0.28 Al 0.57 N 0.15 Sublayer; Cr-BN layer: CrB2 / Cr is deposited on the tool surface. 0.28 Al 0.57 N 0.15 Coating; wherein, CrB2 / Cr 0.28 Al 0.57 N 0.15 The coating consists of a 2.0 μm thick CrB2 sublayer and a 1.2 μm thick Cr... 0.28 Al 0.57 N 0.15 Sublayer; CrB2 / Cr 0.28 Al 0.57 N 0.15 Coating CrB2 sublayer / Cr 0.28 Al 0.57 N 0.15 The sublayer composite structure is composed of cyclic superposition of units, with the cycle number being 2 times; the CrB2 sublayer is columnar nanocrystals with a grain size of 12 nm;

[0067] S5, for CrB2 / Cr 0.28 Al 0.57 N 0.15 Layered cutting tool (Cr) 0.2 Al 0.7 B 0.1 N-layer deposition yields coated cutting tools, (Cr) 0.2 Al 0.7 B 0.1 The N-layer deposition method specifically involves the chemical reaction of H2, CrCl3, AlCl3, BCl3, NH3, and Ar on a CrB2 / Cr layer at 900℃ and 10 mbar. 0.28 Al 0.57 N 0.15 Layered tool surface deposition (Cr) 0.2 Al 0.7 B 0.1 N coating; CrB2 / Cr 0.28 Al 0.57 N 0.15 A 0.7 μm thick layer of (Cr) was deposited on the surface of the cutting tool. 0.2 Al 0.7 B 0.1 N coating;

[0068] The coated cutting tools, from the inside out, consist of: toughened substrate, CrN coating, Cr-BN coating, and CrB2 / Cr. 0.28 Al 0.57 N 0.15 Coating and (Cr) 0.2 Al 0.7 B 0.1 The coating has a total thickness of 8.5 μm, a hardness of 33 GPa, and an overall adhesion of 116 N.

[0069] Comparative Example 1

[0070] The difference between this comparative example and Example 1 is that step S1 is omitted, while all other steps are the same as in Example 1.

[0071] Comparative Example 2

[0072] The difference between this comparative example and Example 1 is that the composite structural units in step S4 are not cyclically superimposed, while the other steps are the same as in Example 1.

[0073] Comparative Example 3

[0074] The difference between this comparative example and Example 2 is that the composite structural unit in step S4 is CrB2 / Cr. 0.6 Al 0.2 N 0.2 The coating process and other steps are the same as in Example 2.

[0075] Comparative Example 4

[0076] The difference between this comparative example and Example 2 is that the coating was prepared using physical vapor deposition, and the target materials used were Cr target, CrB2 target, and Al. 45 Cr 33 Target, Al 65 Cr 35 The target, other reactants include nitrogen gas, and all other steps are the same as in Example 2.

[0077] Comparative Example 5

[0078] The difference between this comparative example and Example 3 is that step S5 is omitted; all other steps are the same as in Example 3.

[0079] Comparative Example 6

[0080] The difference between this comparative example and Example 1 is that step S3 is omitted; all other steps are the same as in Example 1.

[0081] Comparative Example 7

[0082] The difference between this comparative example and Example 1 is that the number of cycles for the composite structural unit in step S4 is 5, while the other steps are the same as in Example 1.

[0083] Comparative Example 8

[0084] The difference between this comparative example and Example 1 is that in step S4, a single CrB2 coating of the same thickness is used instead of the CrB2 / Cr coating. 0.26 Al 0.50 N 0.24 The coating process and other steps are the same as in Example 1.

[0085] Tool wear tests were conducted on Examples 1, 1, 2, 6, and 7. The specific test parameters were as follows: Vc = 160 m / min, fz = 0.25 mm, ap = 2.5 mm, ae = 75 mm; machining material: titanium alloy (Ti-6Al-4V); machining environment: wet cutting, face milling; tool failure was determined by chipping or flank wear ≥ 0.3 mm. Please refer to the test comparison results. Figure 5 , Figure 5 The figures show the wear test results of the cutting tools prepared in Examples 1, 1, 2, 6, and 7 of this application. A comparison with Examples 1, 1, 2, 6, and 7 shows that Example 1 has better impact resistance and tip life stability than Examples 1, 2, 6, and 7. A comparison with Example 1 and Comparative Example 1 demonstrates that the hardened carbide substrate can improve the adhesion between the tool coating and the substrate, enhancing the tool's impact resistance. A comparison with Example 1 and Comparative Example 2 shows that increasing the number of cycles can effectively reduce tensile stress between coatings, improve adhesion, enhance overall coating toughness, and reduce the risk of peeling during cutting. A comparison with Example 1 and Comparative Example 6 shows that without a boron gradient stress relief layer, the bottom CrN layer alone cannot effectively prevent the diffusion of Co elements from the substrate to the coating, causing the coating to peel off rapidly from the bottom layer, significantly reducing the tool coating's impact resistance. A comparison with Example 1 and Comparative Example 7 shows that when CrB2 / Cr... 0.26 Al 0.50 N 0.24 When the number of cycles of the composite structural unit is greater than 4, the interfacial energy between the coatings will be weakened, thereby affecting the bonding force between the composite coatings and reducing the overall impact resistance of the coating.

[0086] Tool wear tests were conducted on Examples 2, 3, and 4. The specific test parameters were as follows: Vc = 150 m / min, fz = 0.25 mm, ap = 2.0 mm, ae = 100 mm; machining material: titanium alloy (Ti-6Al-4V); machining environment: wet cutting, face milling; the tool was judged to be in failure when the chipping or flank wear value was ≥ 0.3 mm; the test comparison results are shown in Table 1, which is the tool wear test result table for Examples 2, 3, and 4.

[0087] Table 1

[0088]

[0089] A comparison of Examples 2, 3, and 4 shows that the average lifespan of Example 2 is significantly better than that of Examples 3 and 4; the lifespan of each cutting tip in Example 2 is stable, and the wear pattern is normal flank wear; a comparison between Example 2 and Example 3 shows that Cr... a Al b N c The Al content of the coating can effectively improve the wear resistance of the coating and thus improve the tool life; Comparative Example 4, with the same Al content, has a large inter-coating stress and poor coating adhesion due to the physical vapor deposition method, which leads to the peeling of the coating during the cutting process and causes abnormal wear failure.

[0090] Tool wear tests were conducted on Example 3 and Comparative Example 5. The specific test parameters were as follows: comparative test parameters: Vc=180m / min, fz=0.25mm, ap=1.5mm, ae=80mm; machining material: titanium alloy (Ti-6Al-4V); machining environment: wet cutting, face milling; the built-up edge area on the tool tip was compared for the same machining time to determine the tool's resistance to adhesive wear; the test comparison results are shown in Table 2, which is the tool wear test result table for Example 3 and Comparative Example 5.

[0091] Table 2

[0092]

[0093] A comparison of Example 3 and Comparative Example 5 shows that the (Cr) deposited on the surface... 0.2 Al 0.7 B 0.1 The presence of boron (B) in the N coating can effectively reduce the affinity between the coating and the workpiece material. The Al and B elements can combine with oxygen to form a dense Al2O3 and a lubricating B2O3 composite oxide film, respectively, thereby improving the coating tool's resistance to adhesive wear.

[0094] An isothermal oxidation experiment was conducted on the cutting tools in Example 1 and Comparative Example 8 to simulate the condition of the cutting tools being heated at a constant temperature in air for a long time. The isothermal heating temperature was T=1000℃, the holding time was t=5h, and a normal amount of air was introduced. The test results are shown in Table 3, which is a table of the isothermal oxidation experiment results of the cutting tools in Example 1 and Comparative Example 8.

[0095] Table 3

[0096]

[0097] A comparison of Example 1 and Comparative Example 9 shows that the single CrB2 coating in Comparative Example 8 is severely oxidized, while the CrB2 / Cr coating in Example 1... 0.26 Al 0.50 N 0.24 Cr coating 0.26 Al 0.50 N 0.24 The sublayer effectively prevents oxygen from the air from diffusing into the coating, maintaining the integrity of the coating structure and performance.

[0098] As can be seen from the above embodiments and comparative examples, the final cutting effect is significantly better than that of the comparative example, whether it is structural optimization or coating composition optimization. In particular, the anti-chipping, wear resistance and anti-adhesive wear ability of the coated tool are significantly enhanced during the machining of titanium alloys.

[0099] This application proposes a method for preparing coated cutting tools suitable for titanium alloy machining. By combining an optimized substrate toughening process with a multilayer composite coating of a specific composition prepared by chemical vapor deposition (CVD), this application significantly improves the adhesion between the coating and the substrate, the hardness, wear resistance, high-temperature oxidation resistance, and anti-adhesion properties of the coating. This effectively solves the technical problems of excessively rapid oxidation, adhesive wear, and chipping of cutting tools during titanium alloy machining.

[0100] The specific features are as follows:

[0101] 1. Prior to coating deposition, this application employs a specialized vacuum toughening treatment on the cemented carbide substrate. This process effectively optimizes the grain boundary structure of the substrate, reduces surface fragments, and ensures grain integrity, thereby providing a superior foundation for subsequent coatings and significantly improving the film-substrate bonding strength.

[0102] 2. This application uses chemical vapor deposition (CVD) to prepare the CrN bonding layer. The CVD method not only allows Cr to fully dissolve with elements such as Co in the matrix to form a strong metallurgical bond, but also, compared with the CrN coating prepared by physical vapor deposition (PVD), it has better toughness and impact resistance, and can effectively buffer the severe stress generated during high-speed milling of titanium alloys.

[0103] 3. By introducing a Cr-BN boron gradient stress-relieving transition layer with a continuously varying boron content between the CrN bonding layer and the outer layer, the problem of lattice distortion and stress concentration caused by the large difference in lattice constant between the CrN bonding layer and the subsequent CrB2 sublayer in the face-centered cubic (FCC) structure is cleverly solved. This boron gradient stress-relieving transition layer achieves a smooth transition from Cr-N bonds to BN bonds and Cr-B bonds, avoiding bond weakening and forming a stronger chemical bonding interface.

[0104] 4. The CrB2 sublayer prepared by chemical vapor deposition (CVD) in this application has extremely high hardness, while the Cr sublayer prepared by the same chemical vapor deposition (CVD) also has very high hardness. a Al b N c The sublayer can achieve a higher Al content, thus obtaining better high-temperature oxidation resistance. By alternately compounding the two in a nano-multilayer structure, the difference in their crystal structure generates lattice distortion at the interface. This internal stress can effectively hinder dislocation movement and crack propagation, synergistically improving the overall macroscopic hardness, yield strength and crack propagation resistance of the coating.

[0105] 5.(Cr x Al y B z Under high cutting temperatures, the Al and B elements in the N-type anti-oxidation surface layer can combine with oxygen to form a dense Al2O3 and a lubricating B2O3 composite oxide film, respectively. This composite film not only further enhances the coating's anti-oxidation ability but also achieves surface self-lubrication, effectively reducing the coefficient of friction and chemical affinity with the titanium alloy workpiece, thereby significantly inhibiting adhesive wear.

[0106] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A coated cutting tool suitable for machining titanium alloys, characterized in that, The coated cutting tool, from the inside out, comprises: a toughened substrate, a CrN coating, a Cr-BN coating, and a CrB2 / Cr coating. a Al b N c Coating and (Cr) x Al y B z )N coating, the CrB2 / Cr a Al b N c The coating consists of a CrB2 sublayer / Cr a Al b N c The sublayer composite structure is composed of cyclically stacked sublayers, wherein the CrB2 sublayer / Cr a Al b N c The sublayer composite structural unit includes CrB2 sublayer, Cr a Al b N c Sublayers, the number of cycles is 2 to 4, the CrN coating, the Cr-BN coating, the CrB2 / Cr a Al b N c Coating and the (Cr) x Al y B z The N coatings were all prepared using chemical vapor deposition. In the Cr-BN coating, the content of element B, by atomic percentage, continuously increases from 0.1 at% to 1 at% at the inner interface adjacent to the CrN coating, up to the content of element B in the CrB2 / Cr coating. a Al b N c The Cr-BN coating consists of Cr-B phase, Cr-N phase and BN phase, with 10 at%-15 at% at adjacent outer interfaces of the coating. The specific method for obtaining the toughened matrix is ​​as follows: obtain a tool matrix, toughen the tool matrix to obtain the toughened matrix, and the tool matrix is ​​WC-Co cemented carbide.

2. A coated cutting tool suitable for machining titanium alloys according to claim 1, characterized in that, The CrN coating, the Cr-BN coating, the CrB2 / Cr a Al b N c Coating and the (Cr) x Al y B z The total thickness of the N coating is 7.0-10.7 μm.

3. A coated cutting tool suitable for machining titanium alloys according to claim 1, characterized in that, The thickness of the CrN coating is 0.5-1.0 μm; The thickness of the Cr-BN coating is 0.5-1.0 μm; the thickness of the single layer of the CrB2 sublayer is 1.5-2.5 μm; the Cr... a Al b N c The thickness of the sublayer monolayer is 0.8-1.5 μm; the (Cr) x Al y B z The thickness of the N coating is 0.5-1.0 μm.

4. A coated cutting tool suitable for machining titanium alloys according to claim 1, characterized in that, The Cr-B phase comprises at least one of CrB2 and Cr2B, the Cr-N phase comprises at least one of CrN and Cr2N, and the BN phase comprises at least one of cubic boron nitride c-BN and hexagonal boron nitride h-BN.

5. A coated cutting tool suitable for machining titanium alloys according to claim 1, characterized in that, The CrB2 sublayer is columnar nanocrystals, and the grain size of the CrB2 sublayer is ≤20nm; the Cr a Al b N c The ratio of a, b, and c in the sublayer is (0.26-0.33): (0.45-0.57): (0.15-0.24).

6. A coated cutting tool suitable for machining titanium alloys according to claim 1, characterized in that, The (Cr) x Al y B z The ratio of x, y, z in the N coating is (0.2-0.3):(0.6-0.7):0.1; the (Cr) coating... x Al y B z The N coating can form a dense Al2O3 and B2O3 composite oxide film on the surface under high cutting temperatures.

7. A coated cutting tool suitable for machining titanium alloys according to claim 1, characterized in that, The coating tool has the following properties: coating hardness ≥30GPa and overall adhesion force ≥100N.

8. A method for preparing a coated cutting tool suitable for machining titanium alloys, characterized in that, This method is used to prepare a coated cutting tool suitable for machining titanium alloys as described in any one of claims 1-7, the preparation method comprising the following steps: S1. Obtain the tool substrate, and toughen the tool substrate to obtain the toughened substrate; S2. A CrN layer is deposited on the toughened substrate to obtain a CrN layer tool, wherein the CrN coating is deposited on the surface of the toughened substrate; S3. A Cr-BN layer is deposited on the CrN layer tool to obtain a Cr-BN layer tool, wherein the Cr-BN coating is deposited on the surface of the CrN layer tool. S4. Perform CrB2 / Cr on the Cr-BN layer tool. a Al b N c Layer deposition yielded CrB2 / Cr a Al b N c Layered cutting tool, wherein the Cr-BN layered cutting tool surface is deposited with the CrB2 / Cr a Al b N c coating; S5, regarding the CrB2 / Cr a Al b N c Layered cutting tool (Cr) x Al y B z The coated tool is obtained by depositing an N-layer, namely CrB2 / Cr a Al b N c The surface of the layered cutting tool was deposited with the (Cr) x Al y B z The CrN coating, from the inside out, comprises: the toughened substrate, the CrN coating, the Cr-BN coating, and the CrB2 / Cr coating. a Al b N c Coating and the (Cr) x Al y B z N coating.

9. A method for preparing a coated cutting tool suitable for machining titanium alloys according to claim 8, characterized in that, In step S1, the tool substrate is a WC-Co cemented carbide containing carbide solid solution grains of Ta and Nb elements. The average grain size of WC in the WC-Co cemented carbide is 1.1-2.3 μm; the maximum pore size in the WC-Co cemented carbide is <1 μm; the WC-Co cemented carbide, by mass percentage, contains 8.0-9.5 wt% Co, 0.5-2.6 wt% Ta, 0.2-1.0 wt% Nb, with the balance being WC; the hardness of the WC-Co cemented carbide is ≥1250 HV; and the fracture toughness KIC of the WC-Co cemented carbide is ≥18 MPa•m. 1 / 2 The toughening treatment specifically involves: applying a vacuum of 1×10⁻⁶. -2 Hold at 800-1000℃ for 30-90 minutes, then cool to below 700℃ at a cooling rate of not less than 5℃ / min.

10. A method for preparing a coated cutting tool suitable for machining titanium alloys according to claim 8, characterized in that, In step S2, the CrN layer is deposited by depositing the CrN coating on the toughened substrate surface through a chemical reaction of H2, CrCl3, and NH3 at 700-800℃ and 5-15mbar. In step S3, the Cr-BN layer is deposited by depositing a Cr-BN coating on the CrN-based tool surface through a chemical reaction of H2, CrCl3, and NH3 at 700-800℃ and 5-15mbar, where BCl3 is introduced into the reaction atmosphere and its flow rate is dynamically increased. The B element content increases continuously from the inside to the outside during this chemical reaction. In step S4, the CrB2 / Cr... a Al b N c The specific deposition method is as follows: under conditions of 700-800℃ and 5-15mbar, the following sequential cycles are performed: the CrB2 sublayer is deposited through a chemical reaction of H2, CrCl3, BCl3, and Ar; the Cr sublayer is deposited through a chemical reaction of H2, CrCl3, AlCl3, NH3, and Ar. a Al b N c Sub-layer; wherein the number of cycles is 2 to 4; in step S5, the (Cr) x Al y B z The N-layer deposition method specifically involves: under conditions of 800-900℃ and 10-20 mbar, the N-layer is deposited through a chemical reaction of H2, CrCl3, AlCl3, BCl3, NH3, and Ar on the CrB2 / Cr... a Al b N c The (Cr) layer tool surface is deposited x Al y B z N coating.

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