Hard alloy containing rare metal and preparation method thereof

Abstract

The invention discloses a hard alloy containing rare metal and a preparation method thereof, the hard alloy comprises a binding phase and a hard phase, the binding phase comprises Co and Re, the hard phase is (W, Re) C, the mass of the Re in solid solution in the hard phase accounts for 50%-90% of the total Re mass, and the total Re / Co atomic percent is not larger than 25%. The preparation method comprises the steps that Co powder, tungsten-rhenium alloy powder, WC powder and carbon powder serve as raw material burdening, pre-ball-milling and ball-milling are conducted, a mixture is dried, granulated, formed and sintered, and the hard alloy containing the rare metal is obtained. The hard alloy containing the rare metal can effectively improve the hardness, wear resistance and high-temperature performance of the hard alloy, and can be suitable for continuous cutting machining of difficult-to-machine materials and stainless steel materials.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy and relates to a hard alloy and a preparation method thereof, in particular to a hard alloy containing rare metals and a preparation method thereof. Background Art

[0002] There have been some reports at home and abroad on adding rare precious metals to cemented carbide, including the addition of rare metal Re. Adding Re can refine WC grains and improve the hardness, bending strength and yield strength of the alloy. Re reduces the stacking fault energy of the cobalt phase and can promote the transformation of the cubic modification of cobalt to the hexagonal system.

[0003] JP Patent Publication No. 2012-86299 discloses a WC-based cemented carbide, wherein the WC-based cemented carbide cutting tool contains Co as a binder phase, Re as an additive, and the balance is composed of WC as a hard phase component and inevitable impurities, wherein the binder phase content is 4-12wt.%, Re is only solid-dissolved in the binder phase, and the content of Re in the binder phase is 3-20wt.%. CN111321334A discloses a corrosion-resistant cemented carbide, wherein the binder phase in the cemented carbide is strengthened by adding rhenium to the binder phase, thereby achieving the purpose of improving the hardness and corrosion resistance of the cemented carbide. The prior art records that Re will solid-dissolve in the binder phase Co, but the cemented carbide still has some defects in the organizational structure.

[0004] In the manufacture of cemented carbide tools, the use of hot isostatic pressing has obvious disadvantages: (1) the dimensional accuracy of the blank is poor, the surface roughness is low, and the grinding process needs to be added, which increases the manufacturing cost; (2) the production efficiency is low and it is not suitable for industrial production. In JP Patent 2012-86299, cemented carbide is sintered by hot isostatic pressing (HIP), and the Re-enriched region is a Re-containing region with an average Re content of 0.2 mass% to 7 mass% at a depth of 1% to 10% of the particle size of the WC particles from the interface of the WC particles, and the average Re content in the region other than the Re-enriched region, that is, the inner side of the WC grains, is less than 0.2 mass%. After experimental research, the present application found that after Re-containing cemented carbide is sintered in a vacuum furnace or a pressure furnace, the solid solution of Re in the cemented carbide is significantly different from that in JP Patent 2012-86299. In addition, when the Re content and the Co content are greater than 25%, the liquid phase temperature of the cemented carbide is greatly increased during the sintering process, the wettability of the hard phase and the bonding phase deteriorates, and the alloy is prone to uneven structure and pores. Therefore, in order to effectively exert the performance improvement advantages of rare metal addition on cemented carbide, on the one hand, it is necessary to solve the defects of cemented carbide caused by the addition of Re, and it is necessary to make a more scientific allocation of the Re addition content. On the other hand, it is necessary to put forward more objective and accurate views on the solid solution of Re in cemented carbide and make more appropriate improvements. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a cemented carbide containing rare metals having uniform structure, good wear resistance and high temperature performance, and applicable to continuous cutting of difficult-to-process materials and stainless steel materials, and a preparation method thereof.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions.

[0007] A rare metal-containing cemented carbide comprises a binder phase and a hard phase, wherein the components of the binder phase include Co and Re, the hard phase is (W, Re)C, the mass of Re dissolved in the hard phase accounts for 50% to 90% of the total mass of Re in the cemented carbide, and the atomic percentage of total Re / Co in the cemented carbide is not greater than 25%.

[0008] The above-mentioned cemented carbide containing rare metals, preferably, the atomic percentage of total Re / W in the cemented carbide is not less than 1.3%.

[0009] For the above-mentioned rare metal-containing cemented carbide, preferably, 3%≤the total atomic percentage of Re / Co≤15%, and 1.3%≤the total atomic percentage of Re / W≤7.2%.

[0010] As a general technical concept, the present invention also provides a method for preparing the above-mentioned cemented carbide containing rare metals, comprising the following steps:

[0011] (1) Ingredients: Co powder, tungsten-rhenium alloy powder, WC powder and carbon powder are used as raw materials. The total amount of raw materials is 100%. By mass fraction, cobalt powder is 5% to 12%, tungsten-rhenium alloy powder is 4.5% to 28.5%. The addition amount of tungsten-rhenium alloy powder should follow the principle that the total Re / Co atomic percentage in the cemented carbide is not greater than 25%. The addition amount of carbon powder is m C =(0.0653m W +0.0496m Re )×x, x=0.85~1.00, m C is the mass of toner, m w 、m Re are the masses of tungsten and rhenium in tungsten-rhenium alloy powder, respectively, and WC powder is the remainder;

[0012] (2) The raw materials are pre-milled and then ball-milled, and the resulting mixture is dried, granulated, molded and sintered to obtain a cemented carbide containing rare metals.

[0013] In the above-mentioned method for preparing a rare metal-containing cemented carbide, preferably, in step (1), the mass fraction of Re in the tungsten-rhenium alloy powder is 20%≤≤26%, and the purity of the tungsten-rhenium alloy powder is not less than 99.90%.

[0014] In the above method for preparing rare metal-containing cemented carbide, preferably, in step (1), the Fsss particle size of the WC powder is 0.2 μm to 6.0 μm.

[0015] In the above-mentioned method for preparing rare metal-containing cemented carbide, preferably, in step (1), the raw material also includes an inhibitor, and the inhibitor includes Cr3C2 powder and / or VC powder.

[0016] In the above-mentioned method for preparing cemented carbide containing rare metals, preferably, in step (2), the specific process of pre-ball milling and ball milling is as follows: the raw materials except WC powder are mixed and pre-ball milled until the Fsss particle size of the powder is ≤1μm, and then WC powder is added for ball milling.

[0017] In the above-mentioned method for preparing rare metal-containing cemented carbide, preferably, in step (2), the pre-ball milling time is 5h to 40h, and the ball milling time is 10h to 60h.

[0018] In the above-mentioned method for preparing a rare metal-containing cemented carbide, preferably, in step (2), the sintering is high-pressure sintering, and the process of the high-pressure sintering is: after removing the molding agent from the cemented carbide compact obtained by molding, the temperature is raised to 1400°C to 1500°C in an Ar atmosphere for high-pressure sintering at a pressure of 40 bar to 80 bar, and the temperature is kept for 20 min to 120 min, and then cooled to room temperature for a cooling time of 30 min to 90 min.

[0019] In the present invention, the hard alloy containing rare metals has good wear resistance and high temperature performance, can be applied to hard alloy cutting tools, and can be suitable for continuous cutting of difficult-to-cut materials and stainless steel materials.

[0020] The main innovative features of the present invention are:

[0021] In the prior art, after adding Ru element to cemented carbide, all Ru is dissolved in the binder phase Co, so technicians simply believe that Re will only be dissolved in the binder phase Co. After research by the applicant, it was found that when different contents of Re are added, its solubility in the hard phase and the binder phase is different, and it is not just dissolved in the binder phase. However, the Re content in WC is not high. The applicant adds rhenium element in the form of tungsten-rhenium alloy powder to obtain a cemented carbide with a high content of Re dissolved in WC. Since the particle size of tungsten-rhenium alloy powder is relatively coarse, it is not conducive to the solid solution of tungsten and rhenium. Therefore, the present invention further adopts a pre-ball milling process to obtain fine-grained tungsten-rhenium alloy powder, and fully mixes it with cobalt powder to obtain a hard phase with a high Re content solid solution. The applicant also found in the study that when the atomic percentage of Re and Co is greater than 25%, the cemented carbide is prone to uneven structure and porosity. When the Re content continues to increase, a decarburized phase will appear in the alloy, and this material is not suitable for cemented carbide tools. Therefore, the total Re / Co atomic percentage in the cemented carbide in the present invention is not greater than 25%.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] 1. In the hard alloy containing rare metals of the present invention, the mass of Re dissolved in the hard phase accounts for 50% to 90% of the total Re mass in the hard alloy, which can improve the structural defects of the hard alloy and improve the wear resistance and high temperature performance of the hard alloy. The atomic percentage of total Re / Co in the hard alloy of the present invention is not more than 25%. When the atomic percentage of total Re / Co is more than 25%, the hard alloy is prone to uneven structure and pores. When the Re content continues to increase, the alloy will have a decarburized phase, and the alloy is not suitable for making hard alloy tools. The hard alloy of the present invention is suitable for continuous cutting of difficult-to-process materials and stainless steel materials.

[0024] 2. In the rare metal-containing cemented carbide of the present invention, the total Re / W atomic percentage is not less than 1.3%. Compared with conventional WC-Co cemented carbide, when the total Re / W atomic percentage is 1.3%, the hardness of the alloy is increased by one level, about 50kg / mm 2 If the total Re / W atomic percentage is less than 1.3%, the hardness of the alloy will not be significantly improved.

[0025] 3. The preparation method of the present invention adds Re element by adopting tungsten-rhenium alloy powder, so that more Re element is dissolved in the hard phase WC, which plays a role in solid solution strengthening on the hard phase WC, and can obtain a cemented carbide with a high content of Re dissolved in WC, which significantly improves the wear resistance of the cemented carbide. The present invention scientifically utilizes the rare metal Re, accurately controls the amount of Re element added, and sets the amount of tungsten-rhenium alloy powder added to follow the principle of making the total Re / Co atomic percentage in the cemented carbide not greater than 25%, so as to avoid the occurrence of microscopic defects such as uneven structure and pores in the cemented carbide. Adding tungsten-rhenium alloy powder can also act as an inhibitor on the growth of WC grain size, refine the main WC grains, control the abnormal growth of WC grains, and help the cemented carbide structure to be more uniform. Since the tungsten-rhenium alloy powder has a coarse particle size, which is not conducive to the solid solution of tungsten and rhenium, the present invention adopts a pre-ball milling process to obtain fine-grained tungsten-rhenium alloy powder, and fully mixes it with cobalt powder to obtain WC with a high Re content solid solution. After adding tungsten-rhenium alloy powder in the present invention, an appropriate amount of carbon powder needs to be added to avoid decarburization phase defects in the alloy, and the amount of carbon powder added is in an arithmetic proportional relationship with the tungsten-rhenium content in the tungsten-rhenium alloy powder. The present invention can be produced and prepared according to a conventional powder metallurgy method, has low production cost, and is convenient for actual production application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an element distribution diagram of the rare metal-containing cemented carbide according to Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0028] Example 1

[0029] A rare metal-containing cemented carbide of the present invention comprises a binder phase and a hard phase, wherein the components of the binder phase include Co and Re, the hard phase is (W, Re)C, the mass of Re dissolved in the hard phase accounts for 58wt.% of the total Re mass in the cemented carbide, the atomic percentage of total Re / Co in the cemented carbide is 4.99at.%, and the atomic percentage of total Re / W is 1.78at.%.

[0030] A method for preparing a rare metal-containing cemented carbide according to this embodiment comprises the following steps:

[0031] (1) Ingredients: Co powder, tungsten-rhenium alloy powder, WC powder and carbon powder are used as raw materials, the total amount of raw materials is 100%, and by mass fraction, the cobalt powder is 9.50wt.%, the tungsten-rhenium alloy powder is 6.10wt.%, and the added amount of carbon powder is m C =(0.0653m W +0.0496m Re )×x,x=0.95,m C is the mass of toner, m w 、m Re are the masses of tungsten and rhenium in tungsten-rhenium alloy powder respectively. The mass fraction of carbon powder corresponding to the mass of carbon powder is 0.64wt.%, and WC powder is the remainder (83.76wt.%).

[0032] In this embodiment, the mass fraction of Re in the tungsten-rhenium alloy powder is 24.6wt.%, the Fsss particle size of the tungsten-rhenium alloy powder is 3μm, the purity is not less than 99.95%, the Fsss particle size of the WC powder is 3.0μm, and the Fsss particle size of the cobalt powder is 1.0μm.

[0033] (2) Add all raw materials except WC powder into a wet mill, add 0.25 L of alcohol as a ball milling medium per kg of mixed raw materials, add 2 wt.% of PEG4000 molding agent based on the total mass of the mixed raw materials, and the mass ratio of the mixed raw materials to the ball mill rod is 1:5. Pre-ball milling is performed for 20 hours to make the Fsss particle size of the powder 0.9 μm, and then add WC powder. After ball milling for 24 hours, discharge the material to obtain a mixed material;

[0034] (3) spray drying and granulating the mixture;

[0035] (4) The granulated mixture is pressed into a shape, and after the molding agent is removed, the temperature is raised to 1460° C. in an Ar atmosphere for high-pressure sintering at a pressure of 50 bar, and the temperature is kept at this temperature for 60 minutes, and then the mixture is rapidly cooled to room temperature for 60 minutes to obtain a cemented carbide containing rare metals.

[0036] Figure 1 This is the element distribution diagram of the transmission electron microscope analysis of the rare metal-containing cemented carbide prepared in this example. It can be seen from the figure that Re is dissolved in WC to form a (W, Re) C hard phase.

[0037] Example 2

[0038] A rare metal-containing cemented carbide of the present invention comprises a binder phase and a hard phase, wherein the components of the binder phase include Co and Re, the hard phase is (W, Re)C, the mass of Re dissolved in the hard phase accounts for 64wt.% of the total Re mass in the cemented carbide, the atomic percentage of total Re / Co in the cemented carbide is 10.02at.%, and the atomic percentage of total Re / W is 2.19at.%.

[0039] A method for preparing a rare metal-containing cemented carbide according to this embodiment comprises the following steps:

[0040] (1) Ingredients: Co powder, tungsten-rhenium alloy powder, WC powder, carbon powder and inhibitor Cr3C2 powder are used as raw materials, the total amount of raw materials is 100%, and by mass fraction, the cobalt powder is 6.01wt.%, the tungsten-rhenium alloy powder is 7.74wt.%, and the addition amount of carbon powder is m C =(0.0653m W +0.0496m Re )×x,x=0.95,m C is the mass of toner, m w 、m Re are the masses of tungsten and rhenium in tungsten-rhenium alloy powder respectively. The mass fraction of carbon powder corresponding to the mass of carbon powder is 0.81wt.%, Cr3C2 powder is 0.23wt.%, and WC powder is the remainder (85.21wt.%).

[0041] In this embodiment, the mass fraction of Re in the tungsten-rhenium alloy powder is 24.6wt.%, the Fsss particle size of the tungsten-rhenium alloy powder is 3μm, the purity is not less than 99.95%, the Fsss particle size of the WC powder is 0.9μm, and the Fsss particle size of the cobalt powder is 1.0μm.

[0042] (2) Add all the above raw materials except WC powder into a wet mill, add 0.25L of alcohol as a ball milling medium per kg of mixed raw materials, add 2.0wt.% PEG4000 and 0.5wt.% PEG1500 forming agents, the mass ratio of the mixed raw materials to the ball mill rod is 1:10, pre-ball mill for 24 hours to make the Fsss particle size of the powder 0.9μm, then add WC powder, continue ball milling for 40 hours and then discharge to obtain a mixed material;

[0043] (3) spray drying and granulating the mixture;

[0044] (4) The granulated mixture is pressed into a shape, and after the molding agent is removed, the temperature is raised to 1420° C. in an Ar atmosphere for high-pressure sintering at a pressure of 60 bar, and the temperature is kept at this temperature for 30 minutes, and then cooled to 100° C. for a cooling time of 60 minutes to obtain a cemented carbide containing rare metals.

[0045] Comparative Example 1

[0046] A cemented carbide and a preparation method thereof are basically the same as those in Example 1, except that no tungsten-rhenium alloy powder is added to obtain a WC-Co cemented carbide.

[0047] Comparative Example 2

[0048] A cemented carbide and a preparation method thereof are basically the same as those in Example 1, except that no carbon powder is added, a third phase of decarburization appears in the obtained cemented carbide, and the cemented carbide is not suitable for cemented carbide tools.

[0049] Comparative Example 3

[0050] A cemented carbide and a preparation method thereof are basically the same as those in Example 1, except that rhenium powder is used to replace tungsten-rhenium alloy powder, the rhenium powder content is 1.50wt.%, and the carbon powder addition amount is 0.07wt.%, thereby obtaining WC-Co-Re cemented carbide.

[0051] Comparative Example 4

[0052] A cemented carbide and a preparation method thereof are basically the same as those in Example 2, except that no tungsten-rhenium alloy powder is added to obtain a WC-Co-Cr cemented carbide.

[0053] Comparative Example 5

[0054] A cemented carbide and a preparation method thereof are basically the same as those in Example 2, except that rhenium powder replaces tungsten-rhenium alloy powder, the rhenium powder content is 1.90wt.%, and the carbon powder addition amount is 0.09wt.%, thereby obtaining WC-Co-Cr-Re cemented carbide.

[0055] Table 1 below is the composition and performance table of the cemented carbides prepared in Example 1 and Comparative Examples 1-3. Compared with Comparative Examples 1, 2, and 3, the cemented carbide prepared in Example 1 has better wear resistance and high temperature performance. In terms of metallography, the metallographic phase of the cemented carbide in Comparative Example 2 has a decarburized phase E08. Analysis shows that the tungsten and rhenium elements in the tungsten-rhenium powder need the C element when forming (W, Re) C. There is no additional carbon powder, so a decarburized phase is formed. The metallographic phases of Example 1 and other comparative examples have no obvious defects. Table 2 is the energy spectrum data of the bonding phase of the cemented carbide. In the cemented carbide of Comparative Example 3, 89% of Re is dissolved in the bonding phase and 11% of Re is dissolved in WC. In the alloy of Example 1, 42% of Re is dissolved in the bonding phase and 58% of Re is dissolved in WC. Therefore, the use of tungsten-rhenium powder will cause more Re to be dissolved in WC. Compared with the cemented carbides of comparative examples 1 and 3, the cemented carbides of embodiment 1 can increase the tool life by about 46% and 16% under the continuous cutting condition of stainless steel materials.

[0056] Table 1 Composition and performance of cemented carbides prepared in Example 1 and Comparative Examples 1-3

[0057]

[0058] Note: TG is the high temperature oxidation weight gain of cemented carbide, which is the oxidation weight gain percentage of cemented carbide when the temperature rises from room temperature to 900°C at a rate of 5°C / min in air atmosphere (the same below).

[0059] Table 2 Binder phase energy spectrum data table of cemented carbide of Example 1 and Comparative Example 3

[0060]

[0061] Table 3 below is the composition and performance table of the cemented carbides prepared in Example 2 and Comparative Examples 4-5. Compared with Comparative Examples 4 and 5, the cemented carbide of Example 2 has better wear resistance and high temperature performance. The metallographic phases of the cemented carbides of Example 2, Comparative Example 4 and Comparative Example 5 have no obvious defects. Table 4 is the energy spectrum data of the bonding phase of the cemented carbides of Example 2 and Comparative Example 5. In the cemented carbide of Comparative Example 5, 82% of Re is dissolved in the bonding phase and 18% of Re is dissolved in WC, while in the cemented carbide of Example 2, 36% of Re is dissolved in the bonding phase and 64% of Re is dissolved in WC. It can be seen that the use of tungsten-rhenium alloy powder will cause more Re to be dissolved in WC. Compared with the cemented carbides of Comparative Examples 4 and Comparative Examples 5, the cemented carbide of Example 2 can increase the tool life by about 50% and 21% under the continuous cutting conditions of the difficult-to-process nickel-based high-temperature alloy.

[0062] Table 3 Composition and performance of cemented carbide of Example 2 and Comparative Examples 4-5

[0063]

[0064] Table 4 Binder phase energy spectrum data table of cemented carbide of Example 2 and Comparative Example 5

[0065]

[0066] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A hard alloy containing rare metals, characterized in that: It comprises a binder phase and a hard phase, wherein the components of the binder phase include Co and Re, the hard phase is (W, Re)C, the mass of Re dissolved in the hard phase accounts for 50% to 90% of the total mass of Re in the cemented carbide, and the atomic percentage of total Re / Co in the cemented carbide is not greater than 25%.

2. The rare metal-containing cemented carbide according to claim 1, characterized in that: The atomic percentage of total Re / W in the cemented carbide is not less than 1.3%.

3. The rare metal-containing cemented carbide according to claim 2, characterized in that: 3%≤the atomic percentage of the total Re / Co≤15%, and 1.3%≤the atomic percentage of the total Re / W≤7.2%.

4. A method for preparing a rare metal-containing cemented carbide according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Ingredients: Co powder, tungsten-rhenium alloy powder, WC powder and carbon powder are used as raw materials. The total amount of raw materials is 100%. By mass fraction, cobalt powder is 5% to 12%, tungsten-rhenium alloy powder is 4.5% to 28.5%. The addition amount of tungsten-rhenium alloy powder should follow the principle that the total Re / Co atomic percentage in the cemented carbide is not greater than 25%. The addition amount of carbon powder is m C =(0.0653m W +0.0496m Re )×x, x=0.85~1.00, m C is the mass of toner, m w 、m Re are the masses of tungsten and rhenium in tungsten-rhenium alloy powder, respectively, and WC powder is the remainder; (2) The raw materials are pre-milled and then ball-milled, and the resulting mixture is dried, granulated, molded and sintered to obtain a cemented carbide containing rare metals.

5. The method for preparing a rare metal-containing cemented carbide according to claim 4, characterized in that: In step (1), the mass fraction of Re in the tungsten-rhenium alloy powder is 20%≤≤26%, and the purity of the tungsten-rhenium alloy powder is not less than 99.90%.

6. The method for preparing a rare metal-containing cemented carbide according to claim 4, characterized in that: In step (1), the Fsss particle size of the WC powder is 0.2 μm to 6.0 μm.

7. The method for preparing a rare metal-containing cemented carbide according to claim 4, characterized in that: In step (1), the raw material also includes an inhibitor, and the inhibitor includes Cr3C2 powder and / or VC powder.

8. The method for preparing a rare metal-containing cemented carbide according to any one of claims 4 to 7, characterized in that: In step (2), the specific process of the pre-ball milling and ball milling is as follows: the raw materials except the WC powder are mixed, and pre-ball milled until the Fsss particle size of the powder is ≤1 μm, and then the WC powder is added for ball milling.

9. The method for preparing a rare metal-containing cemented carbide according to claim 8, characterized in that: In step (2), the pre-ball milling time is 5 h to 40 h, and the ball milling time is 10 h to 60 h.

10. The method for preparing a rare metal-containing cemented carbide according to any one of claims 4 to 7, characterized in that: In step (2), the sintering is high pressure sintering, and the process of high pressure sintering is: forming the hard alloy After the compact is freed from the molding agent, the temperature is raised to 1400℃~1500℃ in an Ar atmosphere for high-pressure sintering at a pressure of 40bar~80bar. Keep warm for 20min to 120min, cool to room temperature, the cooling time is 30min to 90min.

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