Titanium-based cermet, method for producing same, and cutting tool

Abstract

The application relates to the technical field of cermet, and provides a titanium-based cermet, a preparation method thereof and a cutting tool. Through an innovative design of a two-stage nitrogen partial pressure regulation and control process of denitrification-nitriding and a three-layer gradient structure synergistic mechanism, a composite gradient structure cermet with a surface layer gray strengthening phase, an intermediate gradient transition phase and a core homogeneous toughness phase is prepared, so that the fracture toughness is improved while the surface layer high hardness and wear resistance are ensured. In the preparation process of the titanium-based cermet, Ti(C, N) based cermet has strong sensitivity to nitrogen partial pressure. In the sintering process, the external nitrogen atmosphere concentration is regulated and controlled, so that a gradient of the nitrogen concentration of the cermet material itself is generated. The low affinity of transition metals and nitrogen and the high affinity of titanium and nitrogen are utilized to realize the directional migration and distribution regulation of the elements in the gradient direction, and then the in-situ generation of the gray phase structure is realized, so that the high hardness-high toughness of the material is effectively realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cermet, and particularly relates to a titanium-based cermet, a preparation method thereof and a cutting tool. BACKGROUND

[0002] Ti(C,N)-based cermet exhibits unique advantages in the high-speed precision machining field of high-end equipment parts (such as automobile engine cylinder blocks and aerospace structural parts) due to its excellent high-temperature hardness, chemical stability, high-temperature plastic deformation resistance and low friction coefficient with iron-based metals. Under high linear speed (≥300 m / min) machining conditions, higher performance requirements are put forward for cutting tools for machining key parts in general machinery, precision electronics and new energy fields.

[0003] However, the inherent strong covalent bond characteristics of cermet materials result in low fracture toughness (usually only 5-8 MPa·m 1 / 2 , which is lower than that of WC-Co hard alloy (10-17 MPa·m 1 / 2 ). This inherent defect is manifested in actual application as follows: the material is prone to tool edge collapse, internal interface peeling and other failure phenomena under impact load, which seriously limits its application in aerospace, heavy machinery and other fields with high requirements for material impact resistance.

[0004] To solve the above problems, gradient structure design to achieve gradient distribution of material performance has become an important research direction for strengthening and toughening cermet. Early research mainly adopts two-layer gradient structure design (surface layer rich in hard phase + core rich in binder phase), which can improve the surface hardness and core toughness, but the composition of the interface changes significantly, resulting in a difference in thermal expansion coefficient, which easily causes significant thermal stress concentration during sintering cooling or service temperature cycling, causing the interface bonding strength to decrease, ultimately leading to interface peeling failure and reducing the service life of the tool. SUMMARY

[0005] To solve the problems existing in the prior art, the application aims to provide a titanium-based cermet, a preparation method thereof and a cutting tool.

[0006] According to a first aspect of the application, the application provides the following technical scheme:

[0007] A titanium-based cermet, comprising a substrate with a composite gradient structure,

[0008] The composite gradient structure comprises, in order, from the surface of the substrate to the interior:

[0009] a surface layer, the surface layer having a low-content binder phase as a characteristic and a gray phase as a main strengthening hard phase;

[0010] an intermediate transition layer having a composite phase characterized by a high content of binder phase and dominated by a black phase; and

[0011] a core having a homogeneous multi-phase structure consisting of the following phases: a binder phase, a black phase, a gray phase, a core black phase-ring gray phase composite phase, and a core white phase-ring gray phase composite phase;

[0012] wherein the gray phase is a (Ti,W,Nb,Mo,V,Zr)(C,N) solid solution formed by a dissolution-precipitation reaction of Ti(C,N) and one or more of WC, NbC, MoC, VC, ZrC;

[0013] the black phase is undissolved original Ti(C,N) particles;

[0014] the white phase is a (Ti,W,Nb,Mo,V,Zr)(C,N) solid solution formed by a dissolution-precipitation reaction of Ti(C,N) and one or more of WC, NbC, MoC, VC, ZrC, and the total content of Nb, Mo, V, Zr elements in the white phase is higher than the total content of the corresponding elements in the gray phase;

[0015] the core black phase-ring gray phase composite phase is composed of the black phase and the gray phase directly coated outside the black phase;

[0016] the core white phase-ring gray phase composite phase is composed of the white phase and the gray phase directly coated outside the white phase.

[0017] As a preferred scheme of the titanium-based cermet according to the present application, wherein: the substrate comprises the following components:

[0018] Ti(C,N) in an amount of 40-60wt%;

[0019] WC in an amount of 10-30wt%;

[0020] one or more of Co, Ni in an amount of 10-20wt%;

[0021] one or more of NbC, MoC, VC, ZrC in an amount of 5-10wt%.

[0022] As a preferred scheme of the titanium-based cermet according to the present application, wherein: the content of Ti element in the surface layer is 50-60wt%, which is 10wt% and above higher than the content of Ti element in the intermediate transition layer, and 20wt% and above higher than the content of Ti element in the core; the content of W element in the surface layer is 20-30wt%, which is 1-10wt% higher than the content of W element in the intermediate transition layer, and 1-5wt% lower than the content of W element in the core.

[0023] As a preferred scheme of the titanium-based cermet according to the present application, the total content of Nb, Mo, V and Zr in the white phase is 30-90wt% higher than that of the corresponding elements in the gray phase, and the content of each of Nb, Mo, V and Zr in the white phase is higher than that of the corresponding element in the gray phase.

[0024] As a preferred scheme of the titanium-based cermet according to the present application, the thickness of the surface layer is 5-15μm; the volume fraction of the gray phase in the surface layer is ≥90%, and the volume fraction of the binder phase is 0-5%; the grain size of the surface layer is distributed in a gradient increasing from inside to outside along the thickness direction of the surface layer, and the grain size in the inner region of the surface layer is 0.1-1μm, and the grain size at the outermost side of the surface layer is 1-3μm.

[0025] As a preferred scheme of the titanium-based cermet according to the present application, the thickness of the intermediate transition layer is 20-40μm, the volume fraction of the black phase in the intermediate transition layer is 75-95%, the volume fraction of the binder phase is 5-25%, and the grain size of the black phase in the intermediate transition layer is 0.5-2μm.

[0026] As a preferred scheme of the titanium-based cermet according to the present application, the volume fraction of the binder phase in the core is 5-15%, the volume fraction of the black phase is 5-25%, the volume fraction of the gray phase is 15-40%, the volume fraction of the core black phase-ring gray phase composite phase is 5-25%, the volume fraction of the core white phase-ring gray phase composite phase is 0.1-5%, and the fracture toughness of the core is 10-12MPa·m 1 / 2 .

[0027] According to a second aspect of the present application, the present application provides the following technical scheme:

[0028] A preparation method of the above-mentioned titanium-based cermet, comprising the following steps:

[0029] S1, raw material proportioning: weighing Ti(C, N), WC, alloy powder composed of one or more of Co and Ni, composite additive composed of one or more of NbC, MoC, VC and ZrC, and carbon black as raw materials;

[0030] S2, powder mixing and granulation: the raw materials obtained in step S1 are wet ball milled with a forming agent and then spray dried to obtain a mixed powder;

[0031] S3, cold isostatic pressing: the mixed powder obtained in step S2 is cold isostatic pressed under a pressure of 100-200MPa to obtain a titanium-based cermet blank;

[0032] S4, gradient sintering: sinter the titanium-based cermet blank obtained in step S3 by the following steps:

[0033] S41, denitrogenation stage: increase the temperature to 500-1400℃ at a temperature increase rate of 2-5℃ / min, vacuum degree ≤5×10 -3 Pa, promote the pre-diffusion of the binder phase and form a homogeneous multi-phase structure;

[0034] S42, high-temperature sintering: increase the temperature to 1400-1500℃ at a temperature increase rate of 2-3℃ / min, nitrogen partial pressure is 25-30mbar, and heat preservation for 30-60 min, to promote the enrichment of the binder phase and form an intermediate transition layer;

[0035] S43, nitriding regulation: decrease the temperature to 1200-1300℃ at a temperature decrease rate of 5-10℃ / min, nitrogen partial pressure is 30-40mbar, and heat preservation for 20-40 min, to promote the formation of a surface gray phase;

[0036] S44, rapid cooling: rapidly cool to 20℃ at a cooling rate of 20-30℃ / min, and apply 3-6bar high-pressure helium / argon gas to inhibit diffusion channels, to obtain a titanium-based cermet with a composite gradient structure.

[0037] As a preferred scheme of the preparation method of the titanium-based cermet, in the step S1, the content of Ti(C, N) in the raw material is 40-60wt%, the content of WC is 10-30wt%, the content of alloy powder composed of one or more of Co, Ni is 10-20wt%, the content of composite additive composed of one or more of NbC, MoC, VC, ZrC is 3-8wt%, and the content of carbon black is 0.5-2wt%.

[0038] As a preferred scheme of the preparation method of the titanium-based cermet, in the step S1, the mass ratio of Co:Ni in the alloy powder is (1-3):1; and the mass ratio of NbC:MoC:VC:ZrC in the composite additive is (15-20):(1-2):(3-5):1.

[0039] As a preferred scheme of the preparation method of the titanium-based cermet, in the step S2, the ball milling parameters are: ball-to-material ratio is (8-12):1, rotation speed is 200-300r / min, and ball milling time is 12-24h; the spray drying parameters are: inlet temperature is 200-250℃, and outlet temperature is 80-100℃; and the powder requirements are: pass through 100-200 mesh sieve, and fluidity ≥60s / 50g.

[0040] As a preferred scheme of the preparation method of the titanium-based cermet, in the step S42, the binder phase is subjected to directional migration, and the migration rate is 0.5-1.2 μm / min; the volume fraction V of the binder phase in the intermediate transition layer is controlled by controlling the holding time t, and the relationship V=0.33t+5 is satisfied, wherein the unit of the volume fraction V is %, and the unit of the holding time t is min; and the volume fraction of the binder phase in the intermediate transition layer is controlled to be in the range of 5%-25%.

[0041] As a preferred scheme of the preparation method of the titanium-based cermet, in the step S43, the Ti(C,N) dissolution rate is controlled by adjusting the nitrogen partial pressure, and the nitrogen partial pressure is increased by 1 mbar, and the Ti(C,N) dissolution rate is increased by 8-12% as the control means, so as to realize the reconstruction of the gray phase in the surface layer; the thickness H of the surface layer is accurately controlled by controlling the holding time t, and the growth rule satisfies the relationship H=0.5t-5, wherein the unit of the thickness H is μm, and the unit of the holding time t is min; and the thickness of the surface layer is controlled to be in the range of 5 μm-15 μm.

[0042] As a preferred scheme of the preparation method of the titanium-based cermet, in the step S43, the grain size of the outermost side of the surface layer is accurately controlled by controlling the holding time t.

[0043] When the holding time is 0-20 min, the outermost side grain size is 0.1-1 μm;

[0044] When the holding time is 20-30 min, the outermost side grain size is 1-2 μm;

[0045] When the holding time is 30-40 min, the outermost side grain size is 2-3 μm.

[0046] According to a third aspect of the present application, the present application provides the following technical scheme:

[0047] A cutting tool, comprising: a substrate composed of the titanium-based cermet obtained by any of the following ways:

[0048] (i) the above-mentioned titanium-based cermet; or

[0049] (ii) the titanium-based cermet prepared according to the above-mentioned preparation method.

[0050] The beneficial effects of the present application are as follows:

[0051] The application provides a titanium-based cermet, a preparation method thereof and a cutting tool. The cermet with a composite gradient structure of a surface layer gray strengthening phase, an intermediate gradient transition phase and a core homogeneous toughness phase is prepared through an innovative design of a two-stage nitrogen partial pressure regulation process of denitrogenation-nitriding and a three-layer gradient structure synergistic mechanism, so that the high hardness and wear resistance of the surface layer are ensured, and the fracture toughness is improved. In the preparation process of the titanium-based cermet, the Ti(C, N)-based cermet has strong sensitivity to nitrogen partial pressure. Therefore, in the sintering process, the external nitrogen atmosphere concentration is regulated to generate a gradient with the nitrogen concentration of the cermet material itself, so that the low affinity of transition metals (such as cobalt and nickel) and nitrogen and the high affinity of titanium and nitrogen are utilized to realize the directional migration and distribution regulation of the elements in the gradient direction, and then the in-situ generation of the gray phase structure is realized, and the high hardness-high toughness of the material is effectively realized. BRIEF DESCRIPTION OF DRAWINGS

[0052] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0053] Fig. 1 It is an internal organization scanning electron microscope graph of the present application.

[0054] Fig. 2 It is an internal organization structure schematic diagram of the present application.

[0055] In the figure, 100 is a surface layer, 200 is an intermediate transition layer, 300 is a core, 1 is a binder phase, 2 is a black phase, 3 is a gray phase, 4 is a core black phase-ring gray phase composite phase, and 5 is a core white phase-ring gray phase composite phase.

[0056] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the drawings. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0058] The application provides a titanium-based cermet, a preparation method thereof and a cutting tool, and through an innovative design of a "denitrogenation-nitriding" two-stage nitrogen partial pressure regulation process and a three-layer gradient structure synergistic mechanism, a composite gradient structure cermet with a surface layer gray strengthening phase, an intermediate gradient transition phase and a core homogeneous toughness phase is prepared by taking TiC-TiN-WC-Co-Ni as a basic system, adding NbC, MoC, VC, ZrC and other grain growth inhibitors and carbon black sintering aids, and through wet ball milling-spray granulation-gradient sintering. 1 / 2 The presence of the intermediate transition layer realizes thermal stress buffering, the prepared titanium-based cermet has high hardness and wear resistance of the surface layer, and the fracture toughness of the prepared titanium-based cermet is improved to 10-12 MPa·m 1 / 2 , and the technical bottleneck of imbalance between strength and toughness of traditional cermet is solved.

[0059] (1) Process innovation and gradient controllability

[0060] Based on the nitrogen partial pressure sensitivity of the Ti(C,N)-based cermet, an innovative "denitrogenation-nitriding" two-stage dynamic atmosphere regulation process is adopted: by accurately controlling the nitrogen partial pressure in the sintering process, the directional migration and distribution regulation of the binder phase (Co / Ni alloy) in the gradient direction is realized, and then the in-situ reconstruction of the surface layer gray phase (Ti(C,N) solid solution enrichment phase) is promoted. The process breaks through the bottleneck of low regulation precision of traditional gradient structure, and realizes the accurate controllability of composition-structure-performance of the composite gradient structure from the surface layer to the core.

[0061] (2) Three-layer gradient structure design and performance gradient matching

[0062] The Ti(C,N)-based cermet tool prepared by the application has a three-layer gradient structure of surface layer-intermediate transition layer-core:

[0063] Surface layer (thickness 5-15 μm): Ti(C,N) gray strengthening phase structure with low binder phase content (hard phase volume fraction ≥ 90%, binder phase volume fraction 0-5%), forming a highest hardness surface layer;

[0064] Intermediate transition layer (thickness 20-40 μm): black phase structure with high content of binder phase (binder phase volume fraction 5-25%), realizing transition matching of hardness and toughness;

[0065] Core: homogeneous multiphase structure (binder phase volume fraction 5-15%), composed of binder phase, black phase, gray phase, core black phase-ring gray phase composite phase and core white phase-ring gray phase composite phase, ensuring the highest fracture toughness (10-12 MPa·m 1 / 2 ).

[0066] Overall, the performance gradient matching characteristics of "high hardness of surface layer-intermediate transition-core high toughness" are formed.

[0067] (3) Stress relief and synergistic improvement of anti-broken performance

[0068] By designing the composition gradient of the intermediate transition layer, a double-layer stress buffer mechanism of "surface layer-intermediate layer-core" is constructed to reduce the interface stress. Under the premise of ensuring the high hardness and high wear resistance required for cutting tools, the dynamic anti-broken performance of the cermet cutting tool is significantly improved.

[0069] As shown in Figs. 1-2 The present application provides a titanium-based cermet, comprising a substrate with a composite gradient structure,

[0070] The composite gradient structure comprises, in order, from the surface of the substrate to the interior:

[0071] a surface layer 100, the surface layer 100 having a reinforced hard phase characterized by a low content of binder phase 1 and dominated by gray phase 3;

[0072] an intermediate transition layer 200, the intermediate transition layer having a composite phase characterized by a high content of binder phase 1 and dominated by black phase 2; and

[0073] a core 300, the core having a homogeneous multi-phase structure composed of the following phases: binder phase 1, black phase 2, gray phase 3, core black phase-ring gray phase composite phase 4, and core white phase-ring gray phase composite phase 5;

[0074] The gray phase 3 is a (Ti, W, Nb, Mo, V, Zr)(C, N) solid solution formed by Ti(C, N) and one or more metal carbides of WC, NbC, MoC, VC, and ZrC through dissolution-precipitation reaction;

[0075] The black phase 2 is undissolved original Ti(C, N) particles;

[0076] The white phase is a (Ti, W, Nb, Mo, V, Zr)(C, N) solid solution formed by Ti(C, N) and one or more metal carbides of WC, NbC, MoC, VC, and ZrC through dissolution-precipitation reaction, and the total content of Nb, Mo, V, and Zr elements in the white phase is higher than the total content of the corresponding elements in the gray phase 3;

[0077] The core black phase-ring gray phase composite phase 4 is composed of black phase 2 and gray phase 3 directly coated outside it;

[0078] The core white phase-ring gray phase composite phase 5 is composed of white phase and gray phase 3 directly coated outside it.

[0079] The technical solutions of the present application are further described in conjunction with specific embodiments.

[0080] Example 1

[0081] A titanium-based cermet with a composite gradient structure is prepared by the following method:

[0082] S1, the raw material powders are weighed in the following mass ratio: Ti(C, N) 50wt%, WC 25wt%, Co-Ni alloy powder (Co:Ni=2:1) 15wt%, NbC / MoC / VC / ZrC composite additive (mass ratio 18:1.5:4:1) 8wt%, carbon black 2wt%;

[0083] S2, using anhydrous ethanol as medium, the above mixed raw materials and forming agent are wet ball milled in a planetary ball mill at a ball-to-material ratio of 8:1 and a rotation speed of 250 r / min for 18 h, using 56# paraffin as forming agent (content 4%), then spray drying granulation is carried out at an inlet temperature of 220℃ and an outlet temperature of 90℃, and the mixture powder with a flowability of 65s / 50g is obtained by sieving through a 200 mesh screen;

[0084] S3, the mixture is cold isostatic pressed into a green body at a pressure of 200 MPa to obtain a compact;

[0085] S4, the compact is placed in a vacuum sintering furnace, heated according to the predetermined sintering process, the forming agent is removed, and gradient sintering is carried out:

[0086] First, heat up to 1000℃ at a rate of 3℃ / min, maintain a vacuum degree ≤2×10 -3 Pa in the furnace;

[0087] Heat up to 1450℃ at a rate of 2.5℃ / min, introduce nitrogen gas to a partial pressure of 28 mbar, and keep for 45 min;

[0088] Then, cool down to 1250℃ at a rate of 8℃ / min, adjust the nitrogen partial pressure to 35 mbar, and keep for 30 min;

[0089] Finally, cool down to 20℃ at a rate of 25℃ / min under a high pressure argon atmosphere of 5bar, to obtain a titanium-based cermet with a composite gradient structure.

[0090] Example 2

[0091] A titanium-based cermet with a composite gradient structure is prepared by the following method:

[0092] S1, the raw material powder is weighed with the following raw material mass ratio: Ti(C, N) 60wt%, WC 20wt%, Co-Ni alloy powder (Co:Ni = 1:1) 14wt%, NbC / MoC / VC / ZrC composite additive (mass ratio 15:1:3:1) 5.5wt%, carbon black 0.5wt%;

[0093] S2, using anhydrous ethanol as a medium, the above mixed raw materials and molding agent are wet ball milled in a planetary ball mill at a ball-to-material ratio of 12:1 and a rotation speed of 200 r / min for 24 h, 56# paraffin is used as a molding agent (content is 4%), then, under the conditions of an inlet air temperature of 200℃ and an outlet air temperature of 80℃, spray drying granulation is performed, and the mixture powder with a flowability of 60s / 50g is obtained by sieving through a 200 mesh screen;

[0094] S3, the mixture is cold isostatic pressed into a green body under a pressure of 200 MPa to obtain a compact;

[0095] S4, the compact is placed in a vacuum sintering furnace, heated according to a predetermined sintering process, the molding agent is removed, and gradient sintering is performed:

[0096] firstly, heating at a rate of 2℃ / min to 1400℃, maintaining a vacuum degree in the furnace ≤5×10 -3 Pa;

[0097] heating at a rate of 2℃ / min to 1500℃, introducing nitrogen gas to a partial pressure of 25 mbar, and maintaining for 60 min;

[0098] then, cooling at a rate of 5℃ / min to 1200℃, adjusting the nitrogen gas partial pressure to 35 mbar, and maintaining for 40 min;

[0099] finally, rapidly cooling to 20℃ at a rate of 30℃ / min under a high-pressure argon atmosphere of 3 bar, to obtain a titanium-based cermet with a composite gradient structure.

[0100] Example 3

[0101] A titanium-based cermet with a composite gradient structure is prepared by the following preparation method:

[0102] S1, the raw material powder is weighed with the following raw material mass ratio: Ti(C, N) 60wt%, WC 20wt%, Co-Ni alloy powder (Co:Ni = 1:1) 14wt%, NbC / MoC / VC / ZrC composite additive (mass ratio 15:1:3:1) 5.5wt%, carbon black 0.5wt%;

[0103] S2, using anhydrous ethanol as medium, in a planetary ball mill with ball-to-charge ratio of 10:1, rotation speed of 250 r / min, wet ball milling the above mixed raw materials and molding agent for 22 h, using 56# paraffin as molding agent (content of 4%), then, under the conditions of inlet air temperature of 250℃ and outlet air temperature of 100℃, via spray drying granulation, and sieving through a 200 mesh screen, obtaining a mixed material powder with flowability of 65 s / 50g;

[0104] S3, cold isostatic pressing the mixed material under a pressure of 200 MPa to form a green body, obtaining a compact;

[0105] S4, placing the compact in a vacuum sintering furnace, heating according to a predetermined sintering process, removing the molding agent, and performing gradient sintering:

[0106] firstly, heating at a rate of 5℃ / min to 1400℃, maintaining a vacuum degree in the furnace of ≤2×10 -3 Pa;

[0107] heating at a rate of 3℃ / min to 1500℃, introducing nitrogen gas to a partial pressure of 30 mbar, and maintaining for 30 min;

[0108] subsequently, cooling at a rate of 10℃ / min to 1300℃, adjusting the nitrogen gas partial pressure to 40 mbar, and maintaining for 20 min;

[0109] finally, under a high-pressure argon atmosphere of 6 bar, rapidly cooling at a rate of 30℃ / min to 20℃, obtaining a titanium-based cermet with a composite gradient structure.

[0110] Comparative Example 1

[0111] The difference from Example 1 is that there is no nitriding regulation stage, after the sintering temperature reaches 1500℃ and maintaining for 60 min, directly applying a high-pressure argon of 5 bar and rapidly cooling to room temperature, to prepare a homogeneous cermet without gradient structure.

[0112] Comparative Example 2

[0113] The difference from Example 1 is that, in the nitriding regulation stage corresponding to Example 1, the nitrogen gas partial pressure is changed to 20 mbar, and then cooled to room temperature at the same temperature program, retaining a two-layer gradient structure, to prepare a corresponding cermet.

[0114] The titanium-based cermet materials obtained in each example and comparative example are characterized in terms of micro-morphology and element content, and the test results are summarized as follows:

[0115]

[0116] The titanium-based cermet material obtained in each embodiment and the comparative example is subjected to cutting treatment to obtain a cutter base. A blade edge passivation treatment is performed on the cutter base using a spray gun capable of spraying fine sand. The cutter blank after treatment is subjected to cleaning treatment, and a PVD / CVD coating is deposited on the surface to obtain a coated cermet cutter.

[0117] The coated cermet cutters of each embodiment and the comparative example are subjected to different cutting test conditions: end face turning of 4140 steel round bar is performed on each embodiment and the comparative example, and the service life of all cutters is compared; external turning of 4140 steel round bar is performed on each embodiment and the comparative example, and the surface roughness of the workpiece machined by all cutters is compared.

[0118] The cutting test parameters are shown in the following table:

[0119]

[0120] The comparative test data and test results of the coated cermet cutters of each embodiment and the comparative example under different cutting conditions are as follows:

[0121]

[0122] The test results show that under the continuous cutting conditions of 4140 steel round bar: for end face turning, the service life of the embodiments of the present application relative to the comparative example samples is significantly improved; for external turning, the surface roughness of the workpiece machined by the embodiments of the present application relative to the comparative example samples is significantly improved. It can be proved that the cutter of the embodiments of the present application can improve the impact resistance while ensuring the hardness and wear resistance.

[0123] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made by using the content of the present application, or direct / indirect application in other related technical fields within the concept of the present application is included in the patent protection scope of the present application.

Claims

1. A titanium-based metal ceramic, characterized in that, Including matrices with composite gradient structures, The composite gradient structure comprises, from the surface of the matrix to its interior, the following: The surface layer has a reinforced hard phase characterized by a low content of binder phase and dominated by a gray phase; An intermediate transition layer having a composite phase characterized by a high content of binder phase and dominated by a black phase; as well as The core has a homogeneous multiphase structure and is composed of the following phases: a binder phase, a black phase, a gray phase, a core black phase-ring gray phase composite phase, and a core white phase-ring gray phase composite phase. The gray phase is a (Ti,W,Nb,Mo,V,Zr)(C,N) solid solution formed by a dissolution-precipitation reaction of Ti(C,N) and WC, as well as one or more metal carbides selected from NbC, MoC, VC, and ZrC. The black phase is undissolved, original Ti(C,N) particles; The white phase is a (Ti,W,Nb,Mo,V,Zr)(C,N) solid solution formed by the dissolution-precipitation reaction of Ti(C,N) and WC, as well as one or more metal carbides selected from NbC, MoC, VC, and ZrC, and the total content of Nb, Mo, V, and Zr elements in the white phase is higher than the total content of the corresponding elements in the gray phase. The core black phase-ring gray phase composite phase is composed of a black phase and a gray phase directly covering its exterior. The core white phase-ring gray phase composite phase is composed of a white phase and a gray phase directly covering its exterior; The Ti content in the surface layer is 50-60 wt%, which is 10 wt% or more higher than the Ti content in the intermediate transition layer and 20 wt% or more higher than the Ti content in the core; the W content in the surface layer is 20-30 wt%, which is 1-10 wt% higher than the W content in the intermediate transition layer and 1-5 wt% lower than the W content in the core. The thickness of the surface layer is 5-15 μm; the volume fraction of the gray phase in the surface layer is ≥90%, and the volume fraction of the binder phase is 0-5%. The thickness of the intermediate transition layer is 20-40 μm, and the volume fraction of the black phase in the intermediate transition layer is 75-95%, while the volume fraction of the binder phase is 5-25%. The volume fraction of the binder phase in the core is 5-15%, the volume fraction of the black phase is 5-25%, the volume fraction of the gray phase is 15-40%, the volume fraction of the core black phase-ring gray phase composite phase is 5-25%, the volume fraction of the core white phase-ring gray phase composite phase is 0.1-5%, and the sum of the volume fractions of all phases in the core is 100%.

2. The titanium-based metal ceramic according to claim 1, characterized in that, The total content of Nb, Mo, V and Zr elements in the white phase is 30-90 wt% higher than the total content of the corresponding elements in the gray phase, and the content of each of Nb, Mo, V and Zr elements in the white phase is higher than the content of the corresponding elements in the gray phase.

3. The titanium-based metal ceramic according to claim 1, characterized in that, The grain size of the surface layer increases gradually from the inside to the outside along the thickness direction of the surface layer, and satisfies the following: the grain size in the inner region of the surface layer is 0.1-1 μm, and the grain size in the outermost region of the surface layer is 1-3 μm.

4. The titanium-based metal ceramic according to claim 1, characterized in that, Furthermore, the black phase grain size of the intermediate transition layer is 0.5-2 μm.

5. The titanium-based metal ceramic according to claim 1, characterized in that, Furthermore, the fracture toughness of the core is 10-12 MPa·m. 1 / 2 .

6. A method for preparing a titanium-based cermet according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Raw material ratio: Weigh Ti(C,N), WC, alloy powder composed of one or more of Co and Ni, composite additive composed of one or more of NbC, MoC, VC, ZrC, and carbon black as raw materials. S2. Mixing and granulation: The raw materials obtained in step S1 are wet ball-milled with the molding agent and then spray-dried to obtain a mixed powder. S3. Cold isostatic pressing: The mixed powder obtained in step S2 is cold isostatically pressed under a pressure of 100-200MPa to obtain a titanium-based metal ceramic blank. S4. Gradient sintering: The titanium-based metal ceramic preform obtained in step S3 is sintered through the following steps: S41. Denitrification stage: Heat to 500-1400℃ at a heating rate of 2-5℃ / min, with a vacuum degree ≤5×10⁻⁶. -3 Pa; S42. High-temperature sintering: Heat to 1400-1500℃ at a heating rate of 2-3℃ / min, with a nitrogen partial pressure of 25-30mbar, and hold for 30-60 min. S43, Nitrogen permeation control: Cool to 1200-1300℃ at a cooling rate of 5-10℃ / min, with a nitrogen partial pressure of 30-40mbar, and hold for 20-40 min; S44. Rapid cooling: Rapidly cool to 20°C at a cooling rate of 20-30°C / min, and apply 3-6 bar high-pressure helium and / or argon gas to obtain titanium-based metal ceramics with a composite gradient structure.

7. The method for preparing titanium-based cermets according to claim 6, characterized in that, In step S1, the raw materials contain: Ti (C,N) content of 40-60wt%, WC content of 10-30wt%, alloy powder composed of one or more of Co and Ni content of 10-20wt%, composite additive composed of one or more of NbC, MoC, VC, and ZrC content of 3-8wt%, and carbon black content of 0.5-2wt%.

8. The method for preparing titanium-based cermets according to claim 6, characterized in that, In step S1, the mass ratio of Co:Ni in the alloy powder is (1-3):1; the mass ratio of NbC:MoC:VC:ZrC in the composite additive is (15-20):(1-2):(3-5):

1.

9. The method for preparing titanium-based cermets according to claim 6, characterized in that, In step S2, the ball milling parameters are: ball-to-material ratio of (8-12):1, rotation speed of 200-300 r / min, and ball milling time of 12-24 h; the spray drying parameters are: inlet air temperature of 200-250℃, outlet air temperature of 80-100℃; and the powder requirements are: passing through a 100-200 mesh sieve, with a flowability ≥60s / 50g.

10. The method for preparing titanium-based cermets according to claim 6, characterized in that, In step S42, the binder phase undergoes directional migration at a rate of 0.5-1.2 μm / min. The volume fraction V of the binder phase in the intermediate transition layer is controlled by controlling the holding time t, which satisfies the relationship: V=0.33t+5, where the volume fraction V is in % and the holding time t is in min.

11. The method for preparing titanium-based cermets according to claim 6, characterized in that, In step S43, the dissolution rate of Ti(C,N) is controlled by adjusting the partial pressure of nitrogen. Specifically, increasing the partial pressure of nitrogen by 1 mbar is used as a means to increase the dissolution rate of Ti(C,N) by 8-12%, thereby achieving the reconstruction of the gray phase in the surface layer. The thickness H of the surface layer is precisely controlled by controlling the holding time t, and its growth law satisfies the relationship: H = 0.5t - 5, where the unit of thickness H is μm and the unit of holding time t is min. Furthermore, the thickness of the surface layer is controlled within the range of 5 μm to 15 μm.

12. The method for preparing titanium-based cermets according to claim 6, characterized in that, In step S43, the grain size of the outermost layer is precisely controlled by controlling the heat preservation time t. When the heat preservation time is 20-30 min, the outermost grain size is 1-2 μm; When the heat preservation time is 30-40 min, the outermost grain size is 2-3 μm.

13. A cutting tool, characterized in that, include: The matrix is ​​composed of titanium-based metal ceramics obtained in any of the following ways: (i) The titanium-based metal ceramic according to any one of claims 1-5; or (ii) Titanium-based metal ceramics prepared by the preparation method according to any one of claims 6-12.

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