A method for preparing high-hardness, high-strength and high-toughness modified cemented carbide

Abstract

The present invention belongs to the technical field of cemented carbide, specifically to a method for preparing a modified cemented carbide with high hardness, strength, and toughness. The method comprises the following steps: S1: raw material preparation; S2: grinding; and S3: sintering. The present invention fully utilizes the characteristics of various raw materials, using WC of various particle sizes and SiC whiskers of various forms for compounding, and through process optimization, significantly improving the hardness, strength, and toughness of the cemented carbide.

Description

Technical Field

[0001] The invention belongs to the technical field of cemented carbide, and particularly relates to a preparation method of a modified cemented carbide with high hardness, high strength and high toughness. Background Art

[0002] Commonly used cemented carbides are generally metal-ceramic composites with tungsten carbide as the hard phase and metal Co or Ni as the binder. They have extremely high hardness and strength and are widely used in industries such as machinery, mining, petroleum, and drilling. With the development of technology, the industry's requirements for cemented carbides are constantly increasing, requiring cemented carbides to balance hardness, strength, and toughness.

[0003] This requires adding other components to modify the cemented carbide, among which graphene and silicon carbide whiskers are commonly used. However, in the actual modification process, the effect is often not as good as expected. This is because there are problems with the dispersion of graphene and silicon carbide whiskers in cemented carbide. Summary of the Invention

[0004] In order to solve the above technical problems and improve the hardness, strength and toughness of cemented carbide at the same time, the present invention provides a method for preparing a high-hardness, high-strength and high-toughness modified cemented carbide, the method comprising the following steps:

[0005] S1: Raw material preparation

[0006] Prepare the ingredients according to the following recipe:

[0007] WC-1 40-65 parts, WC-2 25-50 parts, Co powder 4-8 parts, graphite 0.5-2.0 parts, SiC whisker-1 1.0-2.0 parts, SiC whisker-2 0.5-1.5 parts, CeO2 0.5-1.5 parts;

[0008] S2: Grinding

[0009] Graphite, WC-1, WC-2, CeO2, and Co powders were mixed in an organic solvent, dispersants were added and dispersed evenly, and then the mixture was transferred to a planetary ball mill for ball milling. Two different sizes of grinding balls were used, with diameters of 7-9 mm and 4-6 mm, respectively, and a mass ratio of 1-2:2-3. The rotation speed was 300-500 rpm, and the mixture was milled under N2 protection for 8-12 hours.

[0010] Then, SiC whisker-1 and SiC whisker-2 were added, the rotation speed was 800-1200 rpm, and the mixture was ground for 20-40 minutes and then dried to obtain a cemented carbide composite powder;

[0011] S3: Sintering

[0012] The spark plasma sintering (SPS) process is adopted for sintering, with the heating rate controlled at 40-60℃ / min, the sintering temperature at 700-900℃, the sintering pressure at 10-30MPa, and the holding time at 5-15min. Then the heating rate is controlled at 70-90℃ / min, reaching the sintering temperature at 1400-1500℃, the sintering pressure at 50-70MPa, and the holding time at 10-20min.

[0013] Preferably, in step S1, the raw materials are prepared according to the following formula:

[0014] WC-1 42-64 parts, WC-2 29-47 parts, Co powder 4.5-7 parts, graphite 0.8-1.5 parts, SiC whisker-1 1.1-1.8 parts, SiC whisker-2 0.7-1.2 parts, CeO2 0.6-1 part.

[0015] In step S1, the average particle size (D50) of WC-1 is 0.8-2 μm; the average particle size (D50) of WC-2 is 300-7000 nm; the average particle size (D50) of Co powder is 600-1000 nm; the diameter of SiC whisker-1 is 0.05-0.8 μm, and the length is 6-60 μm; the diameter of SiC whisker-2 is 0.05-0.8 μm, and the length is 60-120 μm; the average particle size (D50) of CeO2 is 100-300 nm; and the graphite is expanded graphite with a sheet diameter of 200-400 μm.

[0016] Preferably, the average particle size (D50) of WC-1 is 1-1.4 μm, the average particle size (D50) of WC-2 is 400-600 nm; the average particle size (D50) of Co powder is 700-900 nm; the diameter of SiC whisker-1 is 0.1-0.6 μm, and the length is 10-50 μm; the diameter of SiC whisker-2 is 0.1-0.6 μm, and the length is 50-100 μm; the average particle size (D50) of CeO2 is 150-250 nm; and the graphite is expanded graphite with a sheet diameter of 250-350 μm.

[0017] The organic solvent in step S2 is one or more of ethylene glycol, cyclohexane, and acetone, preferably ethylene glycol.

[0018] The amount of the organic solvent is not limited, as long as the raw materials can be dispersed. The amount of the organic solvent is not limited, and is 200-3000 parts, preferably 500-2000 parts, and more preferably 750-1200 parts.

[0019] The dispersant in step S2 is one or more of PVA, PVP, PEG200, and PEG400, preferably PVP.

[0020] The amount of the dispersant is not limited, as long as it can assist in dispersing the raw materials. The amount of the dispersant is not limited, and is 0.1-8 parts, preferably 0.5-5 parts, and more preferably 1-3 parts.

[0021] In step S2, the mixture is first dispersed by ultrasonic and then transferred to a planetary ball mill.

[0022] The grinding balls used in step S2 are zirconia grinding balls.

[0023] In step S3, the temperature is slowly lowered to room temperature after sintering is completed.

[0024] It is known in the art that graphene can improve the mechanical properties of cemented carbide, but graphene often has difficulty in dispersion. In the present invention, the high hardness of carbides in cemented carbide powder is utilized, and combined with grinding balls of different particle sizes and cemented carbide raw materials such as WC of different particle sizes, the graphite can be ground and the graphene can be peeled off during the ball milling process. Moreover, the in-situ generated graphene is fully mixed with other raw materials, which can maximize the modification effect of graphene.

[0025] SiC whiskers are also a common modification material for cemented carbide, used to improve the toughness and strength of cemented carbide. However, during the experiment, the inventors found that adding SiC whiskers and other raw materials together into a grinder did not produce good results. After several adjustments, they thought of adding them separately. After rapid grinding, they found that this method could not only prevent significant damage to the structure of the SiC whiskers, but also ensure uniform mixing of the various components of the cemented carbide. Only based on this mixing method can the reinforcing and toughening effects of SiC whiskers be fully exerted.

[0026] On the basis of the above selection, the present invention also combines two-stage temperature increase for sintering, so that the obtained cemented carbide is denser, has a better structure, and has correspondingly better performance.

[0027] Secondly, the present invention provides a high-hardness, high-strength and high-toughness modified cemented carbide, which is prepared using the above method.

[0028] In addition, the present invention also provides an application of a high-hardness, high-strength, and high-toughness modified cemented carbide, which is used to prepare cutting tools, rods, pipes, and the like.

[0029] Preferably, the cemented carbide is used to prepare cutting tools.

[0030] Preferably, the cutting tools include turning tools, milling cutters, planer cutters, drill bits, etc.

[0031] The advantages and beneficial effects of the present invention are:

[0032] (1) The present invention makes full use of the characteristics of various raw materials, uses WC of various particle sizes and SiC whiskers of various forms for compounding, and makes full use of other raw materials such as Co powder and CeO2 to coordinate the components and particle sizes, adjusts to obtain the optimal component formula, and synergistically improves the hardness, strength and toughness of cemented carbide.

[0033] (2) The present invention uses graphene, SiC whiskers, etc. to modify cemented carbide, and uses a mixing method of separate feeding and differential grinding, and then sintering in two stages of heating. The resulting cemented carbide has the best performance and the hardness can reach about 2000HV. 30 , the strength can reach about 2500MPa, and the toughness can reach about 12MPa·m 1 / 2 , the wear rate can reach about 3.5×10 -7 mm 3 ·N -1 ·m -1 , effectively extending the service life of cemented carbide and greatly reducing costs.

[0034] (3) The cemented carbide modification process of the present invention is simple, low-cost, has no requirements on equipment, has good modification effect, and has broad application prospects. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the solutions of the present invention and to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the technical solutions in the embodiments of the present invention are clearly and completely described below with reference to specific illustrations.

[0036] This embodiment is only a part of the embodiments of the present invention and does not represent all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0037] raw material

[0038] WC-1: average particle size (D50) = 1.2 μm;

[0039] WC-2: average particle size (D50) = 500 nm;

[0040] Co powder: average particle size (D50) = 800 nm;

[0041] SiC whisker-1: diameter 0.1-0.6μm, length 10-50μm;

[0042] SiC whisker-2: diameter 0.1-0.6μm, length 50-100μm;

[0043] CeO2: average particle size (D50) = 200 nm;

[0044] Graphite: expanded graphite with a flake diameter of 300 μm.

[0045] [Example 1]

[0046] A method for preparing a high-hardness, high-strength, and high-toughness modified cemented carbide, the method comprising the following steps:

[0047] S1: Raw material preparation

[0048] Prepare the ingredients according to the following recipe:

[0049] WC-1 55 parts, WC-2 37 parts, Co powder 6 parts, graphite 1.2 parts, SiC whisker-1 1.5 parts, SiC whisker-2 1 part, CeO2 0.8 parts, PVP 2 parts, ethylene glycol 1000 parts;

[0050] S2: Grinding

[0051] Graphite, WC-1, WC-2, CeO2, and Co powders were mixed in ethylene glycol, and PVP was added for ultrasonic dispersion. The mixture was then transferred to a planetary ball mill for ball milling. Two different sizes of zirconia grinding balls were used, with diameters of 8 mm and 5 mm, respectively, with a mass ratio of 2:3. The speed was 400 rpm, and the grinding was carried out under N2 protection for 10 hours.

[0052] Then SiC whisker-1 and SiC whisker-2 were added, the rotation speed was 1000 rpm, and the mixture was ground for 30 min and then dried to obtain cemented carbide composite powder;

[0053] S3: Sintering

[0054] The spark plasma sintering (SPS) process was adopted for sintering, with the heating rate controlled at about 50℃ / min, the sintering temperature at 800℃, the sintering pressure at 20MPa, and the holding time at 10min. Then the heating rate was controlled at 80℃ / min to reach the sintering temperature at 1450℃, the sintering pressure at 60MPa, and the holding time at 15min, and then the temperature was slowly cooled to room temperature.

[0055] [Example 2]

[0056] A method for preparing a high-hardness, high-strength, and high-toughness modified cemented carbide, the method comprising the following steps:

[0057] S1: Raw material preparation

[0058] Prepare the ingredients according to the following recipe:

[0059] WC-1 64 parts, WC-2 47 parts, Co powder 7 parts, graphite 1.5 parts, SiC whisker-1 1.8 parts, SiC whisker-2 1.2 parts, CeO2 1 part, PVP 2.4 parts, ethylene glycol 1200 parts;

[0060] S2: Grinding

[0061] Graphite, WC-1, WC-2, CeO2, and Co powders were mixed in ethylene glycol, and PVP was added for ultrasonic dispersion. The mixture was then transferred to a planetary ball mill for ball milling. Two different sizes of zirconia grinding balls were used, with diameters of 8 mm and 5 mm, respectively, with a mass ratio of 2:3. The speed was 400 rpm, and the grinding was carried out under N2 protection for 10 hours.

[0062] Then SiC whisker-1 and SiC whisker-2 were added, the rotation speed was 1000 rpm, and the mixture was ground for 30 min and then dried to obtain cemented carbide composite powder;

[0063] S3: Sintering

[0064] The spark plasma sintering (SPS) process was adopted for sintering, with the heating rate controlled at about 50℃ / min, the sintering temperature at 800℃, the sintering pressure at 20MPa, and the holding time at 10min. Then the heating rate was controlled at 80℃ / min to reach the sintering temperature at 1450℃, the sintering pressure at 60MPa, and the holding time at 15min, and then the temperature was slowly cooled to room temperature.

[0065] [Example 3]

[0066] A method for preparing a high-hardness, high-strength, and high-toughness modified cemented carbide, the method comprising the following steps:

[0067] S1: Raw material preparation

[0068] Prepare the ingredients according to the following recipe:

[0069] WC-1 42 parts, WC-2 29 parts, Co powder 4.5 parts, graphite 0.8 parts, SiC whisker-1 1.1 parts, SiC whisker-2 0.7 parts, CeO2 0.6 parts, PVP 1.5 parts, ethylene glycol 750 parts;

[0070] S2: Grinding

[0071] Graphite, WC-1, WC-2, CeO2, and Co powders were mixed in ethylene glycol, and PVP was added for ultrasonic dispersion. The mixture was then transferred to a planetary ball mill for ball milling. Two different sizes of zirconia grinding balls were used, with diameters of 8 mm and 5 mm, respectively, with a mass ratio of 2:3. The speed was 400 rpm, and the grinding was carried out under N2 protection for 10 hours.

[0072] Then SiC whisker-1 and SiC whisker-2 were added, the rotation speed was 1000 rpm, and the mixture was ground for 30 min and then dried to obtain cemented carbide composite powder;

[0073] S3: Sintering

[0074] The spark plasma sintering (SPS) process was adopted for sintering, with the heating rate controlled at about 50℃ / min, the sintering temperature at 800℃, the sintering pressure at 20MPa, and the holding time at 10min. Then the heating rate was controlled at 80℃ / min to reach the sintering temperature at 1450℃, the sintering pressure at 60MPa, and the holding time at 15min, and then the temperature was slowly cooled to room temperature.

[0075] [Comparative Example 1]

[0076] A method for preparing a modified cemented carbide with high hardness, high strength and high toughness, wherein the raw materials are changed to the following formula:

[0077] WC-1 25 parts, WC-2 67 parts, Co powder 6 parts, graphite 1.2 parts, SiC whisker-1 1.5 parts, SiC whisker-2 1 part, CeO2 0.8 parts, PVP 2 parts, ethylene glycol 1000 parts;

[0078] The remaining steps are the same as those in Example 1.

[0079] [Comparative Example 2]

[0080] A method for preparing a modified cemented carbide with high hardness, high strength and high toughness, wherein the raw materials in step S1 are changed to the following formula (without adding WC-1):

[0081] WC-2 92 parts, Co powder 6 parts, graphite 1.2 parts, SiC whisker-1 1.5 parts, SiC whisker-2 1 part, CeO2 0.8 parts, PVP 2 parts, ethylene glycol 1000 parts;

[0082] The remaining steps are the same as those in Example 1.

[0083] [Comparative Example 3]

[0084] A method for preparing a modified cemented carbide with high hardness, high strength and high toughness, wherein the raw materials are changed to the following formula (without adding SiC whisker-2):

[0085] WC-1 55 parts, WC-2 37 parts, Co powder 6 parts, graphite 1.2 parts, SiC whisker-1 2.5 parts, CeO2 0.8 parts, PVP 2 parts, ethylene glycol 1000 parts;

[0086] The remaining steps are the same as those in Example 1.

[0087] [Comparative Example 4]

[0088] A method for preparing a modified cemented carbide with high hardness, high strength and high toughness, wherein step S2 is changed to the following steps:

[0089] Graphite, WC-1, WC-2, CeO2, Co powder, SiC whisker-1, and SiC whisker-2 were mixed in ethylene glycol, and PVP was added for ultrasonic dispersion. The mixture was then transferred to a planetary ball mill for ball milling. Two different sizes of zirconia grinding balls were used, with diameters of 8 mm and 5 mm, respectively, in a mass ratio of 2:3. The speed was 400 rpm, and the mixture was milled under N2 protection for 10 hours to obtain cemented carbide composite powder.

[0090] The remaining steps are the same as those in Example 1.

[0091] [Comparative Example 5]

[0092] A method for preparing a modified cemented carbide with high hardness, high strength and high toughness, wherein step S3 is changed to the following steps:

[0093] The spark plasma sintering (SPS) process was used for sintering, with a heating rate of about 50°C / min, a sintering temperature of 1450°C, a sintering pressure of 60 MPa, and a holding time of 15 minutes, followed by a slow cooling to room temperature.

[0094] The remaining steps are the same as those in Example 1.

[0095] The modified cemented carbide was tested as follows, wherein the bending strength of the cemented carbide was tested by a three-point bending test method; the Vickers hardness was measured using a Vickers hardness tester; and the wear rate of the cemented carbide was tested using a ball-on-disc friction and wear testing machine with a load of 80N.

[0096]

[0097] As can be seen from the above, the WC of different particle sizes is used in conjunction with the grinding balls of two different diameters, so that when the graphite in-situ grinding is become Graphene, each component of hard alloy is fully mixed, and the sintering for next step is prepared. No matter the hard alloy obtained is hardness, strength and toughness, it is all very good. Secondly, as can be seen from Comparative Example 4, although SiC whisker has good modification effect, the time of ball milling with other components is too long, causing certain damage in the form, and fully utilizing the excellent performance of whisker. In addition, as can be seen from Comparative Example 5, the hard alloy obtained by two-stage heating is more dense, and structure is better, and corresponding performance is also better.

[0098] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-hardness, high-strength and high-toughness modified cemented carbide, the technical characteristics of which are: The method comprises the following steps: S1: Raw material preparation Prepare the ingredients according to the following recipe: WC-1 40-65 parts, WC-2 25-50 parts, Co powder 4-8 parts, graphite 0.5-2.0 parts, SiC whisker-1 1.0-2.0 parts, SiC whisker-2 0.5-1.5 parts, CeO2 0.5-1.5 parts; The average particle size D50 of WC-1 is 1-1.4 μm, and the average particle size D50 of WC-2 is 400-600 nm; the diameter of SiC whisker-1 is 0.1-0.6 μm, and the length is 10-50 μm; the diameter of SiC whisker-2 is 0.1-0.6 μm, and the length is greater than 50 μm and less than or equal to 100 μm; S2: Grinding Graphite, WC-1, WC-2, CeO2, and Co powders were mixed in an organic solvent, dispersants were added and dispersed evenly, and then the mixture was transferred to a planetary ball mill for ball milling. Two different sizes of grinding balls were used, with diameters of 7-9 mm and 4-6 mm, respectively, and a mass ratio of 1-2:2-3. The rotation speed was 300-500 rpm, and the mixture was milled under N2 protection for 8-12 hours. Then, SiC whisker-1 and SiC whisker-2 were added, the rotation speed was 800-1200 rpm, and the mixture was ground for 20-40 minutes and then dried to obtain a cemented carbide composite powder; S3: Sintering The spark plasma sintering process is adopted for sintering, the heating rate is controlled at 40-60℃ / min, the sintering temperature is 700-900℃, the sintering pressure is 10-30MPa, and the holding time is 5-15min. Then the heating rate is controlled at 70-90℃ / min, reaching the sintering temperature of 1400-1500℃, the sintering pressure is 50-70MPa, and the holding time is 10-20min.

2. The preparation method according to claim 1, wherein the raw materials are prepared according to the following formula in step S1: WC-1 42-64 parts, WC-2 29-47 parts, Co powder 4.5-7 parts, graphite 0.8-1.5 parts, SiC whisker-1 1.1-1.8 parts, SiC whisker-2 0.7-1.2 parts, CeO2 0.6-1 part.

3. The preparation method according to claim 1, wherein in step S1, the average particle size D50 of the Co powder is 700-900 nm; the average particle size D50 of the CeO2 is 150-250 nm; and the graphite is expanded graphite with a flake diameter of 250-350 μm.

4. The preparation method according to claim 1, wherein the organic solvent in step S2 is one or more of ethylene glycol, cyclohexane, and acetone.

5. The preparation method according to claim 4, wherein the dispersant in step S2 is one or more of PVA, PVP, PEG200, and PEG400.

6. The preparation method according to claim 1, wherein the dispersant is added in step S2 and then uniformly dispersed by ultrasonication and then transferred to a planetary ball mill.

7. The preparation method according to claim 1, wherein the grinding balls used in step S2 are zirconium oxide grinding balls.

8. The preparation method according to claim 1, wherein the temperature is slowly lowered to room temperature after sintering in step S3.

9. A modified cemented carbide with high hardness, high strength and high toughness, the technical feature of which is that it is prepared using the method described in any one of claims 1 to 8.

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