Cemented carbide with low cobalt content and tool made of the same

Abstract

The present invention discloses a cemented carbide with low cobalt content and a tool manufactured thereof, belonging to the technical field of low cobalt cemented carbide. The low cobalt content cemented carbide of the present invention comprises the following chemical components by mass fraction: 81.16-81.56 parts of W, 5.90-6.30 parts of C, 1.98 parts of Co, 1.74 parts of Cr, 1.86 parts of Fe, 1.95 parts of Ni, 0.2 parts of Nb, 0.39 parts of V and 4.52 parts of Mo. The present invention limits the addition ratio of each element by comprehensively considering the influence of Fe and Ni on the fcc phase stability of Co, and the influence of Cr on the hcp phase stability of Co, so that the obtained cemented carbide has an extremely low cobalt content, and the cubic carbide gradient zone therein can also effectively hinder crack propagation, and has obvious performance advantages.

Description

Technical Field

[0001] The invention relates to the technical field of low-cobalt cemented carbide, in particular to a cemented carbide with low cobalt content and a tool made thereof. Background Art

[0002] Cemented carbide is an alloy material made of hard compounds of refractory metals and bonding metals through powder metallurgy, such as cemented carbide materials made by bonding tungsten carbide (WC) particles with cobalt. Among them, tungsten carbide is a very hard ceramic material with extremely high hardness and wear resistance. However, tungsten carbide alone is brittle and difficult to process and use. It is usually needed to be used with a bonding phase, which mainly provides ductility, toughness and strength for the alloy. When the bonding phase composition and its content are different, the physical and chemical performance indicators of cemented carbide are also different. The most commonly used bonding metal in the field today is cobalt. Cobalt acts as a binder between tungsten carbide particles, increases the toughness and plasticity of the alloy, and also helps to improve the corrosion resistance of the alloy, making it more suitable for applications under various harsh environmental conditions. Tungsten-cobalt cemented carbide has many excellent properties, including extremely high hardness, excellent wear resistance, excellent corrosion resistance, high thermal stability and chemical stability, and has been widely used in cutting tools, mining tools, molds, drill bits, abrasive materials and other fields.

[0003] However, there are many problems with Co as a binder. Metal Co with a low melting point is prone to severe adhesive wear and oxidative wear. In addition, Co's poor corrosion resistance, high cost and toxicity also limit the mechanical industrial application of WC-Co cemented carbide. Therefore, the application of cemented carbide can be expanded by partially or completely replacing the Co bonding phase. Traditional alternative binder metals are Fe and Ni-based alloys, but iron-based alloys face the problem of a very narrow carbon window in the binder phase, and the concentration range in which tungsten and carbon can be dissolved is very narrow, and unwanted carbides are easily produced. Although nickel-based alloys have a wider carbon window, cemented carbides using them as binders have the disadvantages of low strength and poor thermal conductivity. Therefore, there is an urgent need to improve the bonding metal of cemented carbide. Summary of the invention

[0004] The purpose of the present invention is to provide a cemented carbide with low cobalt content and a tool made of the same. The present invention limits the addition ratio of each element by comprehensively considering the influence of Fe and Ni on the fcc phase stability of Co and the influence of Cr on the hcp phase stability of Co, so that the prepared cemented carbide has an extremely low cobalt content, and the cubic carbide gradient zone therein can effectively hinder crack propagation, and has obvious performance advantages.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is to provide a cemented carbide with a low cobalt content, which comprises the following chemical components by weight:

[0007] W 81.16-81.56 parts, C 5.90-6.30 parts, Co 1.98 parts, Cr 1.74 parts, Fe 1.86 parts, Ni 1.95 parts, Nb 0.2 parts, V 0.39 parts and Mo 4.52 parts.

[0008] The second technical solution of the present invention is to provide a method for preparing the above-mentioned cemented carbide with low cobalt content, comprising the following steps:

[0009] The raw materials are prepared, ground, pressed and sintered to obtain the cemented carbide with low cobalt content.

[0010] The surface energy of WC grains is relatively high, and abnormal grain growth is very likely to occur during sintering, which affects the material properties. In order to prepare cemented carbide with fine grain size, the type of inhibitor is selected as a necessary means to control grain growth. The present invention can better inhibit the increase of grain size by adding NbC, VC and Mo2C to the alloy system, thereby obtaining an ultrafine cemented carbide with high strength and high hardness.

[0011] Preferably, the grinding is grinding to a particle size of ≤5 μm.

[0012] Preferably, the compression molding is to press into a green compact with a void ratio of 2-5%.

[0013] Preferably, the sintering is performed by heating the material to 1500° C. at a rate of 1-10° C. / min and then sintering the material for 1 hour; the sintering is performed in an oxygen-free condition.

[0014] The third technical solution of the present invention is to provide an application of the above-mentioned cemented carbide with low cobalt content in the field of tool preparation.

[0015] The technical principles of the present invention are as follows:

[0016] According to the Greer confusion principle, complex phases or amorphous phases can form in HEAs (high entropy alloy binder phases). These multi-component alloys may actually form simple, random substitutional alloys, also known as disordered solid solutions (DSS) on simple lattices.

[0017] The reason why Co can become an effective bonding phase is that it can promote the martensitic phase transformation between the low-temperature hexagonal close-packed (hcp) and face-centered cubic (fcc) phases, which has an important influence on the resistance to plastic deformation. There are very few elements that can add Co without destroying the stability of the hcp phase. The hcp-fcc phase transformation is difficult to achieve through other elements. The direct hcp-fcc transformation only occurs in 6 elements in the periodic table, among which Co is the only element that does not present a bcc phase in the phase diagram. This phase transformation is always missing in standard alternative binder alloys. The inventors of the present invention used the phase diagram calculation (CALPHAD) method to study the carbon window and phase equilibrium of various materials, and found a low-Co content binder solution that can expand the carbon window as much as possible while promoting the hcp-fcc transformation. , thereby achieving the addition of as little Co as possible to promote the completion of the hcp-fcc phase transformation.

[0018] The beneficial technical effects of the present invention are as follows:

[0019] Since there is a martensitic phase transformation between a low-temperature hexagonal close-packed (hcp) phase and a face-centered cubic (fcc) phase in the low-cobalt content cemented carbide of the present invention, Co has a strong ability to resist plastic deformation.

[0020] In the prior art, the stability of hcp and fcc phases is usually improved by forming a solid solution of Co and hard phases such as WC. However, the present invention comprehensively considers the influence of Fe and Ni on the fcc phase stability of Co, and the influence of Cr on the hcp phase stability of Co, and limits the addition ratio of each element, so that the cemented carbide made of the prepared new binder CoCrFeNi multi-component alloy has an extremely low cobalt content, and the cubic carbide gradient zone therein can also effectively hinder crack propagation, with obvious performance advantages.

[0021] The tool prepared by the cemented carbide of the present invention is far superior to the conventional cemented carbide tool using cobalt as the bonding metal in the prior art in terms of plastic deformation resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 This is a vertical cross-sectional view of the product of Example 1.

[0024] Figure 2The relationship between the solubility of W element in the FCC_L12 phase and the C content of the product of Example 1. DETAILED DESCRIPTION

[0025] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0026] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0027] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0028] The words “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0029] Unless otherwise specified, the parts in the present invention are all calculated by mass.

[0030] The "room temperature" in the present invention is 20-30°C unless otherwise specified.

[0031] All raw materials used in the following examples and comparative examples of the present invention are commercially available products.

[0032] Example 1

[0033] A cemented carbide with a low cobalt content, consisting of the following chemical components in parts by mass:

[0034] W: 81.56 parts, C: 5.90 parts, Co: 1.98 parts, Cr: 1.74 parts, Fe: 1.86 parts, Ni: 1.95 parts, Nb: 0.2 parts, V: 0.39 parts, and Mo: 4.52 parts.

[0035] Preparation of cemented carbide with low cobalt content:

[0036] (1) preparing various raw materials, and then wet-grinding them together with a cylindrical pebble mill made of WC-Co material in ethanol to a particle size of ≤5 mm, and then drying the powder to evaporate all the ethanol to obtain a pre-made powder;

[0037] (2) The prefabricated powder was pressed into a blade-shaped compact with a porosity of 4.1%, and then the compact was sintered under vacuum conditions; the sintering method was to heat the compact to 900°C at a rate of 9°C / min under vacuum conditions, and then heat the compact to 1500°C at a rate of 5°C / min and maintain for 1 hour, during which the gas pressure was controlled to 0.3 MPa by argon back pressure, and then placed in a cooling device, in a nitrogen atmosphere, the sample temperature was cooled to room temperature at a cooling rate of 50°C / min to obtain a cemented carbide with a low cobalt content.

[0038] Example 2

[0039] The only difference from Example 1 is that the cemented carbide thereof is composed of the following chemical components in parts by mass:

[0040] W: 81.51 parts, C: 5.95 parts, Co: 1.98 parts, Cr: 1.74 parts, Fe: 1.86 parts, Ni: 1.95 parts, Nb: 0.2 parts, V: 0.39 parts, and Mo: 4.52 parts.

[0041] Example 3

[0042] The only difference from Example 1 is that the cemented carbide thereof is composed of the following chemical components in parts by mass:

[0043] W: 81.16 parts, C: 6.30 parts, Co: 1.98 parts, Cr: 1.74 parts, Fe: 1.86 parts, Ni: 1.95 parts, Nb: 0.2 parts, V: 0.39 parts, and Mo: 4.52 parts.

[0044] Comparative Example 1

[0045] The only difference from Example 1 is that the mass fraction of the cobalt content in the cemented carbide is changed to 1.0 part.

[0046] Comparative Example 2

[0047] The only difference from Example 1 is that the mass fraction of the cobalt content in the cemented carbide is changed to 1.6 parts.

[0048] Comparative Example 3

[0049] The only difference from Example 1 is that the mass fraction of the cobalt content in the cemented carbide is changed to 2.4 parts.

[0050] Comparative Example 4 (conventional cemented carbide in the prior art)

[0051] The only difference from Example 1 is that the cemented carbide thereof is composed of the following chemical components in parts by mass:

[0052] W: 81.86 parts, C: 5.95 parts, Co: 7.20 parts, Ni: 0.09 parts, N: 0.41 parts, Nb: 2.69 parts, and Ta: 1.80 parts.

[0053] Effect verification

[0054] (1) The CALPHAD method was used to analyze the phase diagram of Example 1, and the change in the solubility of the W element in the high entropy alloy binder phase was calculated by changing only the proportion of the C element in the cemented carbide of Example 1. The test results are shown in Figure 1-2 shown.

[0055] Figure 1 It is a vertical cross-sectional view of the product of Example 1. Figure 1 It can be seen that there are 17 phase regions in the isophase of its product system, and the fifth phase represents the carbon window. At a lower carbon content (about 5.0wt%), the figure shows phase regions such as liquid phase (liq), face-centered cubic phase (FCC) and HCP. With the increase of carbon content, more phase regions gradually appear in the system, such as carbide phases such as M6C, M7C3 and graphite (GRAPHITE). This phase diagram has important guiding significance for understanding the heat treatment process and mechanical properties of the alloy. Different combinations of phase regions will result in alloys with different hardness, strength, toughness and other properties. This phase diagram reflects the complexity of the evolution law of the high entropy alloy system after the addition of carbon elements, and provides a theoretical basis for the research and development and application of related materials.

[0056] Figure 2 The relationship between the solubility of W element in the FCC_L12 phase and the C content of the product of Example 1. Figure 2 It can be seen that the solubility of W element in the high entropy alloy binder phase increases with the increase of carbon content at low carbon content. When the carbon content increases to 5.9, the solubility of W element decreases with the increase of carbon content.

[0057] (2) Hardness tests were performed on Examples 1-3 and Comparative Examples 1-4, and compared with a commercially available product (brand: Jinboshi, item number 4160511, grade YG8, referred to as the control group). The test results are shown in Table 1.

[0058] Table 1

[0059] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Control group 1820 1800 1675 1690 1755 1720 1550 1532

[0060] As can be seen from Table 1, the hardness is high at low carbon levels and decreases with increasing carbon content.

[0061] (3) Dry friction and wear tests were performed on Examples 1-3 and Comparative Examples 1-4, and compared with a commercially available product (brand: Jinboshi, item number: 4160511, grade: YG8, denoted as the control group). The test instrument was a Pin-on-Disk friction and wear tester. The sample was made into a pin shape and the wear test was performed on a rotating disk. A load of 10N and a rotation speed of 300rpm were applied, and the test time was 60 minutes. The wear rate and friction coefficient between the pin and the disk were recorded. The test results are shown in Table 2.

[0062] Table 2

[0063]

[0064] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A cemented carbide with low cobalt content, characterized in that: By mass, it is composed of the following chemical components: W 81.16-81.56 parts, C 5.90-6.30 parts, Co 1.98 parts, Cr 1.74 parts, Fe 1.86 parts, Ni 1.95 parts, Nb 0.2 parts, V 0.39 parts and Mo 4.52 parts; The preparation method of the low cobalt content cemented carbide is: Prepare raw materials, grind, press-form, and sinter to obtain the low-cobalt-content cemented carbide; The grinding is grinding to a particle size of ≤5 μm; The pressing molding is to press into a green compact with a porosity of 2-5%; The sintering is performed by heating the temperature to 1500° C. at a speed of 1-10° C. / min and then sintering for 1 hour; the sintering is performed under oxygen-free conditions.

2. Use of the low-cobalt content cemented carbide according to claim 1 in the field of tool preparation.

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