Ceramic binder phase gradient cemented carbide tool material and method for producing the same

Abstract

The present application belongs to the technical field of hard alloy material, and particularly relates to a ceramic binder phase gradient hard alloy cutter material and a preparation method thereof. The present application takes cubic structure TiN and hexagonal closest packing structure ZrO2 as a composite ceramic binder phase, cooperates solid solution activation sintering and micro liquid phase strengthening sintering, and sets the grain size as nanometer scale, cooperates silicon carbide nanowire and two-step discharge plasma sintering, and comprehensively uses various sintering advantages to realize high density configuration of the ceramic binder phase hard alloy cutter material. The present application combines component toughening and structure toughening, designs a multi-level organization configuration of micro layer and macro gradient, prevents and eliminates cracks layer by layer, essentially breaks through the old thought of simple composite of complex components, proposes to load traditional toughening phase by low-dimensional toughening phase (graphene, silicon carbide nanowire), introduces traditional toughening mechanism and new toughening mechanism such as graphene, and simultaneously applies gradient structure to introduce surface residual compressive stress toughening, and finally forms a multi-level toughening mechanism with multi-element and multi-scale characteristics.

Description

Technical Field

[0001] This invention belongs to the field of cemented carbide materials technology, and specifically relates to a ceramic-bonded phase gradient cemented carbide cutting tool material and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] The hardness of cemented carbide is slightly lower than that of diamond, cubic boron nitride, and ceramics, but significantly higher than that of high-speed steel. Its toughness is slightly lower than that of high-speed steel, but significantly higher than that of diamond, cubic boron nitride, and ceramics, which makes cemented carbide tools irreplaceable in the field of cutting.

[0004] Traditional cemented carbide, using metallic Co as a binder phase, improves the density and toughness of tool materials to some extent, but it also brings a series of drawbacks: the introduction of Co leads to degradation of material hardness, high-temperature performance, oxidation resistance, and corrosion resistance, making traditional cemented carbide tools often only suitable for low-to-medium speed cutting and requiring the use of cutting fluid; the thermal mismatch between WC and Co makes cemented carbide prone to thermal stress during preparation; the low melting point of Co causes WC-Co cemented carbide tools to easily experience adhesive wear when machining highly ductile materials (such as pure iron), accelerating tool failure; Co is a scarce strategic resource, and its continuously rising price leads to a continuous increase in the manufacturing cost of cemented carbide, which to some extent limits its widespread application; WC-Co composite powder is highly toxic, which is inconsistent with the concept of green manufacturing. For these reasons, both industry and academia are urgently seeking new Co-free binder phases to prepare resource-friendly and environmentally friendly high-performance cemented carbides.

[0005] Ceramic-bonded Co binder phases are used in the preparation of cemented carbide cutting tool materials by employing specific carbide ceramics and / or oxide ceramics, or nitride ceramics, as Co substitute binder phases. Ceramic-bonded cemented carbide tools possess unparalleled wear resistance, oxidation resistance, corrosion resistance, and high-temperature performance compared to traditional cemented carbide tools, as well as higher toughness than traditional ceramic tools. They are particularly suitable for high-speed machining of difficult-to-machine materials such as titanium alloys and aluminum alloys, which generate a large amount of heat and have high plasticity, aligning with the concept of green machining. However, a ceramic-bonded phase gradient cemented carbide tool material that combines both high hardness and high toughness has not yet been developed. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a "dual-high" cemented carbide tool material, namely a ceramic-bonded phase gradient cemented carbide tool material that combines high hardness and high toughness, and provides a simple preparation method suitable for industrial production.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a ceramic-bonded phase gradient cemented carbide tool material, comprising: an upper surface layer, a first transition layer, a core layer, a second transition layer, and a lower surface layer disposed sequentially; wherein the first transition layer and the second transition layer, and the upper surface layer and the lower surface layer are respectively symmetrically disposed with respect to the core layer;

[0009] Both the upper and lower surface layers are composed of the following raw materials in parts by weight: 91.4%–95.7% WC, 1%–3% nano TiN, 3%–5% nano ZrO2, 0.1%–0.2% graphene, and 0.2%–0.4% silicon carbide nanowires;

[0010] The first transition layer and the second transition layer are both composed of the following raw materials in parts by weight: 87.4% to 92.7% WC, 2% to 5% nano TiN, 5% to 7% nano ZrO2, 0.1% to 0.2% graphene, and 0.2% to 0.4% silicon carbide nanowires;

[0011] The core layer is composed of the following raw materials in parts by weight: 83.25%–89.55% WC, 3%–7% nano TiN, 7%–9% nano ZrO2, 0.15%–0.25% graphene, and 0.3%–0.5% silicon carbide nanowires.

[0012] A second aspect of the present invention provides a method for preparing a ceramic-bonded phase gradient cemented carbide tool material, comprising:

[0013] Nano-TiN and nano-ZrO2 were dispersed in anhydrous ethanol, and polyethylene glycol was added and dispersed evenly to obtain a nano-multiphase ceramic binder suspension.

[0014] Graphene and silicon carbide nanowires were dispersed in anhydrous ethanol, and a complex dispersant was added to disperse them evenly, thus obtaining a graphene-silicon carbide nanowire suspension.

[0015] The graphene-silicon carbide nanowire suspension was added to the nano-composite ceramic binder phase suspension, dispersed evenly, ball-milled, and vacuum dried in two steps to obtain graphene-silicon carbide nanowire-nano-composite ceramic composite powder.

[0016] The graphene-silicon carbide nanowire-nano-multiphase ceramic composite powder and WC powder were dispersed and mixed separately to obtain powder suspensions of each gradient layer; then ball milled and dried to obtain powders of each gradient layer.

[0017] The powders of each gradient layer are pressed into shape in a mold and sintered to obtain a ceramic-bonded phase gradient cemented carbide tool material.

[0018] In some embodiments, the amount of polyethylene glycol used is 1.0%-1.5% of the mass of the nano-ceramic particles.

[0019] In some embodiments, the compound dispersant is composed of polyethylene glycol and polyvinylpyrrolidone in a mass ratio of 1:1-1.5.

[0020] In some embodiments, the amount of the complex dispersant is 75%-80% of the total mass of graphene and silicon carbide nanowires.

[0021] In some embodiments, the dispersion is carried out under conditions of mechanical stirring and ultrasonic dispersion.

[0022] In some embodiments, the specific steps of the two-step vacuum drying include: first drying at 70-75℃ for 6-8 hours, and then drying at 85-90℃ until completely dry.

[0023] In some implementations, a layered compaction method is used for material loading.

[0024] In some embodiments, the sintering is performed using a two-step spark plasma sintering process.

[0025] In some embodiments, the specific conditions of the two-step discharge plasma sintering process include: maintaining a vacuum degree below 10-12 Pa, heating to 1700-1900°C at a rate of 150-160°C / min, holding at that temperature for 0-5 min, then cooling to 1600-1750°C at a rate of 150-160°C / min and holding at that temperature for 0.5-5 h, followed by furnace cooling; maintaining a pressure of 20-24 MPa from room temperature to 1200°C, and maintaining a pressure of 40-45 MPa from 1200°C to 1700-1900°C.

[0026] More specifically, the present invention provides a ceramic-bonded phase gradient cemented carbide tool material, wherein the gradient layer comprises 5 symmetrical layers. The surface layer is composed of (91.4-95.7)WC-(1-3) nano-TiN-(3-5) nano-ZrO2-(0.1-0.2) graphene-(0.2-0.4) silicon carbide nanowires by mass ratio. The transition layer is composed of (87.4-92.7)WC-(2-5) nano-TiN-(5-7) nano-ZrO2-(0.1-0.2) graphene-(0.2-0.4) silicon carbide nanowires by mass ratio. The core layer is composed of (83.25-89.55)WC-(3-7) nano-TiN-(7-9) nano-ZrO2-(0.15-0.25) graphene-(0.3-0.5) silicon carbide nanowires by mass ratio.

[0027] Specifically, the following steps are included:

[0028] (1) Ingredients

[0029] The surface layer is composed of (91.4–95.7)WC-(1–3)nm TiN-(3–5)nm ZrO2-(0.1–0.2)graphene-(0.2–0.4)silicon carbide nanowires by mass ratio; the transition layer is composed of (87.4–92.7)WC-(2–5)nm TiN-(5–7)nm ZrO2-(0.1–0.2)graphene-(0.2–0.4)silicon carbide nanowires by mass ratio; and the core layer is composed of (83.25–89.55)WC-(3–7)nm TiN-(7–9)nm ZrO2-(0.15–0.25)graphene-(0.3–0.5)silicon carbide nanowires by mass ratio.

[0030] (2) Nanoscale multiphase ceramic binder phase dispersion

[0031] According to the required mass ratio, anhydrous ethanol was used as the dispersion solvent to disperse nano-TiN and nano-ZrO2 in a specific mass ratio. 1.0% polyethylene glycol relative to the mass of the nano-ceramic particles was added, and the mixture was mechanically stirred and ultrasonically dispersed for 60 min to obtain a nano-multiphase ceramic binder suspension.

[0032] (3) Dispersion of graphene and silicon carbide nanowires

[0033] According to the required mass ratio, the graphene and silicon carbide nanowires were dispersed using anhydrous ethanol as the dispersion solvent. A compound dispersant (polyethylene glycol: polyvinylpyrrolidone = 1:1) of 75% relative to the mass of graphene and silicon carbide nanowires was added. The mixture was mechanically stirred and ultrasonically dispersed for 60 minutes to obtain a graphene-silicon carbide nanowire suspension.

[0034] (4) Preparation of graphene-silicon carbide nanowire-nano-composite ceramic powder

[0035] The graphene-silicon carbide nanowire suspension obtained in step (2) was poured into the nano-composite ceramic binder phase suspension obtained in step (1). After ultrasonic dispersion for 30 min, high-energy ball milling was performed for 12 h. Then, two-step vacuum drying was performed: first drying at 70 °C for 8 h, and then drying at 90 °C until completely dried. After sieving, a uniformly mixed graphene-silicon carbide nanowire-nano-composite ceramic composite powder was obtained.

[0036] (5) Mixing

[0037] Following the proportions in step (1), the graphene-silicon carbide nanowire-nano-multiphase ceramic composite powder and WC powder were dispersed and mixed separately to obtain powder suspensions of each gradient layer. The suspensions were then ball-milled at high energy for 20 hours and vacuum-dried to obtain powders of each gradient layer.

[0038] (6) Pressing and sintering

[0039] The weight of powder in each gradient layer was calculated based on the mold size and gradient layer thickness. The five gradient powder layers were pressed into shape using a layered pressing method. A two-step spark plasma sintering process was adopted: the vacuum degree was maintained below 10 Pa, the temperature was increased to 1700-1900℃ at 150℃ / min, held for 0-5 min, then cooled to 1600-1750℃ at 150℃ / min, held for 0.5-5 h, and then cooled in the furnace. The pressure was maintained at 20 MPa from room temperature to 1200℃, and at 40 MPa from 1200-1700~1900℃.

[0040] The above process continues until the sintering process is completed, and a "double-high" ceramic binder gradient cemented carbide tool material with both high hardness and high toughness can be obtained.

[0041] Beneficial effects of the present invention

[0042] (1) This invention introduces cubic TiN and hexagonal close-packed ZrO2 as composite ceramic binder phases, which work together with solid solution activation sintering and micro liquid phase strengthening sintering. At the same time, the grain size is set to the nanoscale, which works together with silicon carbide nanowires and two-step discharge plasma sintering. By combining multiple sintering advantages, a high-density configuration of ceramic binder phase cemented carbide tool material is achieved.

[0043] (2) The present invention employs secondary high-energy ball milling, which can achieve uniform distribution of the binder phase-graphene-silicon carbide nanowires in cemented carbide tool materials.

[0044] (3) This invention proposes to combine component toughening and structural toughening, and designs a multi-level organizational structure with micro-layered and macro-gradient structures to “defend against cracks layer by layer and eliminate them on the spot”. It breaks through the old idea of ​​simple composite of complex components in essence. It proposes to load traditional toughening phases with low-dimensional toughening phases (graphene, silicon carbide nanowires), introduce traditional toughening mechanisms and new toughening mechanisms such as graphene, and apply gradient structure to introduce surface residual compressive stress toughening, and finally form a multi-level toughening mechanism with multi-dimensional and multi-scale characteristics.

[0045] (4) From a production technology perspective, a technology is provided for the industrial production of high-hardness, high-toughness ceramic-bonded phase gradient cemented carbide tool materials.

[0046] (5) The preparation method of the present invention is simple, practical and easy to promote. Attached Figure Description

[0047] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. Exemplary embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0048] Figure 1This is a phase analysis diagram of the ceramic binder phase gradient cemented carbide tool material prepared in Example 1;

[0049] Figure 2 The graph shows the toughness changes of the ceramic binder phase gradient hard alloy prepared in Example 1 from the surface to the interior using a hardness tester. Detailed Implementation

[0050] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0051] Terminology Explanation:

[0052] WC refers to tungsten carbide.

[0053] TiN refers to titanium nitride.

[0054] ZrO2 refers to zirconium dioxide.

[0055] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0056] In the following embodiments, the hardness, fracture toughness, and bending strength of the cutting tool were all tested using methods commonly used in the industry.

[0057] Example 1

[0058] (1) Using 0.4μm WC, 20nm TiN, 100nm ZrO2, graphene, and silicon carbide nanowires as raw materials, the surface layer is composed of 95.7WC-1nm TiN-3nm ZrO2-0.1graphene-0.2silicon carbide nanowires by mass ratio, the transition layer is composed of 92.7WC-2nm TiN-5nm ZrO2-0.1graphene-0.2silicon carbide nanowires by mass ratio, and the core layer is composed of 89.7WC-3nm TiN-7nm ZrO2-0.15graphene-0.3silicon carbide nanowires by mass ratio.

[0059] (2) The nano-ceramic powder was dispersed according to the mass ratio of TiN to ZrO2 in the surface layer, transition layer and core layer respectively. Anhydrous ethanol was used as the dispersion solvent, and 1.0% polyethylene glycol relative to the mass of the nano-ceramic particles was added. The mixture was mechanically stirred and ultrasonically dispersed for 60 min to obtain a nano-multiphase ceramic binder suspension.

[0060] (3) Graphene and silicon carbide nanowires were dispersed according to the mass ratio of the surface layer, transition layer and core layer respectively. Anhydrous ethanol was used as the dispersion solvent. A compound dispersant (polyethylene glycol: polyvinylpyrrolidone = 1:1) of 75% relative to the mass of graphene and silicon carbide nanowires was added. The mixture was mechanically stirred and ultrasonically dispersed for 60 min to obtain a graphene-silicon carbide nanowire suspension.

[0061] (4) Pour the graphene-silicon carbide nanowire suspension obtained in step (2) into the nano-composite ceramic binder phase suspension obtained in step (1), continue ultrasonic dispersion for 30 min, then perform high-energy ball milling for 12 h, and then perform two-step vacuum drying, first drying at 70℃ for 8 h, then drying at 90℃ until completely dried, and sieve to obtain a uniformly mixed graphene-silicon carbide nanowire-nano-composite ceramic composite powder.

[0062] (5) Following the proportions in step (1), the graphene-silicon carbide nanowire-nano-multiphase ceramic composite powder and WC powder were dispersed and mixed separately to obtain powder suspensions of each gradient layer. The suspensions were ball-milled at high energy for 20 hours and then vacuum-dried to obtain powders of each gradient layer.

[0063] (6) The pressure was maintained at 20 MPa from room temperature to 1200℃, and at 40 MPa from 1200℃ to 1800℃. A layered pressing method was used to press five layers of gradient powder into shape; a two-step discharge plasma sintering process was employed: heating at 120℃ / min to 1800℃, holding for 3 min, then cooling at 125℃ / min to 1675℃, holding for 0.5 h, and then cooling with the furnace; the pressure was maintained at 20 MPa from room temperature to 1200℃.

[0064] Maintain a pressure of 40 MPa at 1200-1800℃.

[0065] After the sintering process is completed, a "dual-high" ceramic binder gradient cemented carbide tool material with both high hardness and high toughness can be obtained. Its phase analysis is as follows: Figure 1 As shown, the mechanical properties from the surface to the interior are as follows: Figure 2 As shown. The mechanical properties are: hardness HV 25.7 GPa, fracture toughness 12.6 MPa·m. 1 / 2 Flexural strength 1406MPa.

[0066] Example 2

[0067] (1) Using 0.4μm WC, 20nm TiN, 100nm ZrO2, graphene, and silicon carbide nanowires as raw materials, the surface layer is composed of 95.4WC-1nm TiN-3nm ZrO2-0.2 graphene-0.4 silicon carbide nanowires by mass ratio, the transition layer is composed of 92.4WC-2nm TiN-5nm ZrO2-0.2 graphene-0.4 silicon carbide nanowires by mass ratio, and the core layer is composed of 89.4WC-3nm TiN-7nm ZrO2-0.25 graphene-0.5 silicon carbide nanowires by mass ratio.

[0068] (2) Same as Example 1.

[0069] (3) Same as Example 1.

[0070] (4) Same as Example 1.

[0071] (5) Same as Example 1.

[0072] (6) Same as Example 1.

[0073] After the sintering process is completed, a "dual-high" ceramic-bonded phase gradient cemented carbide tool material with both high hardness and high toughness can be obtained. Its mechanical properties are: hardness HV 23.3 GPa, fracture toughness 12.2 MPa·m. 1 / 2 Flexural strength 1292.7 MPa.

[0074] Example 3

[0075] (1) Same as Example 1. The surface layer is composed of 91.4 WC-3 nm TiN-5 nm ZrO2-0.2 nm graphene-0.4 nm silicon carbide nanowires by mass ratio, the transition layer is composed of 87.4 WC-5 nm TiN-7 nm ZrO2-0.2 nm graphene-0.4 nm silicon carbide nanowires by mass ratio, and the core layer is composed of 83.25 WC-7 nm TiN-9 nm ZrO2-0.25 nm graphene-0.5 nm silicon carbide nanowires by mass ratio.

[0076] (2) Same as Example 1.

[0077] (3) Same as Example 1.

[0078] (4) Same as Example 1.

[0079] (5) Same as Example 1.

[0080] (6) Same as Example 1.

[0081] After the sintering process is completed, a "dual-high" ceramic-bonded phase gradient cemented carbide tool material with both high hardness and high toughness can be obtained. Its mechanical properties are: hardness HV 22.9 GPa, fracture toughness 12.7 MPa·m. 1 / 2Flexural strength 1214.6 MPa.

[0082] Comparative Example 1

[0083] The difference from Example 1 is that no nano-TiN was added; instead, WC was used to replace the corresponding proportion of nano-TiN. Its mechanical properties are: hardness HV 21.2 GPa, fracture toughness 10.7 MPa·m. 1 / 2 The bending strength is 1034.1 MPa.

[0084] Comparative Example 2

[0085] The difference from Example 1 is that micron-sized TiN is used instead of nano-sized TiN. Its mechanical properties are: hardness HV 21.5 GPa, fracture toughness 11.2 MPa·m. 1 / 2 The bending strength is 1063.6 MPa.

[0086] As can be seen from the comparison between Example 1 and Comparative Example 1, the introduction of nano-TiN can form a composite ceramic binder phase with ZrO2, which effectively enhances the hardness and toughness of the tool material.

[0087] As can be seen from the comparison between Example 1 and Comparative Example 2, nano-TiN can better improve the hardness and toughness of tool materials compared with micron-sized TiN.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A ceramic binder phase gradient cemented carbide tool material, characterized in that, include: The upper surface layer, the first transition layer, the core layer, the second transition layer, and the lower surface layer are arranged sequentially; the first transition layer and the second transition layer, and the upper surface layer and the lower surface layer are respectively arranged symmetrically with respect to the core layer; Both the upper and lower surface layers are composed of the following raw materials in parts by weight: 91.4%~95.7% WC, 1%~3% nano TiN, 3%~5% nano ZrO2, 0.1%~0.2% graphene, and 0.2%~0.4% silicon carbide nanowires; The first transition layer and the second transition layer are both composed of the following raw materials in parts by weight: 87.4%~92.7% WC, 2%~5% nano TiN, 5%~7% nano ZrO2, 0.1%~0.2% graphene, and 0.2%~0.4% silicon carbide nanowires; The core layer is composed of the following raw materials in parts by weight: 83.25%~89.55% WC, 3%~7% nano TiN, 7%~9% nano ZrO2, 0.15%~0.25% graphene, and 0.3%~0.5% silicon carbide nanowires.

2. The method for preparing the ceramic-bonded phase gradient cemented carbide tool material according to claim 1, characterized in that, include: Nano-TiN and nano-ZrO2 were dispersed in anhydrous ethanol, and polyethylene glycol was added and dispersed evenly to obtain a nano-multiphase ceramic binder suspension. Graphene and silicon carbide nanowires were dispersed in anhydrous ethanol, and a complex dispersant was added to disperse them evenly, thus obtaining a graphene-silicon carbide nanowire suspension. The graphene-silicon carbide nanowire suspension was added to the nano-composite ceramic binder phase suspension, dispersed evenly, ball-milled, and vacuum dried in two steps to obtain graphene-silicon carbide nanowire-nano-composite ceramic composite powder. The graphene-silicon carbide nanowire-nano-multiphase ceramic composite powder and WC powder were dispersed and then mixed to obtain powder suspensions of each gradient layer. Ball milling and drying were performed to obtain powders of various gradient layers; The powders of each gradient layer are pressed into shape in a mold and sintered to obtain a ceramic-bonded phase gradient cemented carbide tool material.

3. The method for preparing ceramic-bonded phase gradient cemented carbide tool material as described in claim 2, characterized in that, The amount of polyethylene glycol used is 1.0%-1.5% of the mass of the nano-ceramic particles.

4. The method for preparing the ceramic-bonded phase gradient cemented carbide tool material as described in claim 2, characterized in that, The compound dispersant is composed of polyethylene glycol and polyvinylpyrrolidone in a mass ratio of 1:1-1.

5.

5. The method for preparing the ceramic-bonded phase gradient cemented carbide tool material as described in claim 2, characterized in that, The amount of the compound dispersant is 75%-80% of the total mass of graphene and silicon carbide nanowires.

6. The method for preparing ceramic-bonded phase gradient cemented carbide tool material as described in claim 2, characterized in that, The dispersion was carried out under mechanical stirring and ultrasonic dispersion conditions.

7. The method for preparing ceramic-bonded phase gradient cemented carbide tool material as described in claim 2, characterized in that, The specific steps of the two-step vacuum drying include: first drying at 70-75℃ for 6-8 hours, and then drying at 85-90℃ until completely dry.

8. The method for preparing ceramic-bonded phase gradient cemented carbide tool material as described in claim 2, characterized in that, The material is loaded using a layered compaction method.

9. The method for preparing the ceramic-bonded phase gradient cemented carbide tool material as described in claim 2, characterized in that, The sintering process employs a two-step spark plasma sintering process.

10. The method for preparing the ceramic-bonded phase gradient cemented carbide tool material as described in claim 9, characterized in that, The specific conditions for the two-step discharge plasma sintering process include: maintaining a vacuum degree below 10-12 Pa, heating to 1700-1900℃ at a rate of 150-160℃ / min, holding at that temperature for 0-5 min, then cooling to 1600-1750℃ at a rate of 150-160℃ / min and holding at that temperature for 0.5-5 h, followed by furnace cooling; maintaining a pressure of 20-24 MPa from room temperature to 1200℃, and maintaining a pressure of 40-45 MPa from 1200℃ to 1700-1900℃.

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