Composite tungsten carbide powder and preparation method thereof

Abstract

The invention relates to the field of tungsten carbide, and provides a preparation method of composite tungsten carbide powder in order to solve the problem that in the preparation process of existing tungsten carbide powder, due to concentrated volatilization of a binder during sintering, the morphology of the powder cannot be effectively kept. 55-65 parts of tungsten carbide, 5-9 parts of cobalt powder, 1-3 parts of polyethylene glycol and 18-24 parts of alcohol are put into a ball mill to be subjected to ball milling, and slurry is obtained; s200, granulating the slurry through an atomization drying tower to obtain mixed powder; s300, sintering the mixed powder to obtain a powder block; s400, the powder blocks are made into composite tungsten carbide powder through a dry grinding machine; the polyethylene glycol comprises a polymer with the molecular weight of 2000 to 20000. The molecular weight of the polyethylene glycol is regulated and controlled, so that the polyethylene glycol not only can keep a good bonding effect, but also can be volatilized in batches during sintering, the morphology of mixed powder is kept, the defects of a sintered product are reduced, and the performance of a final product is improved.

Description

Technical Field

[0001] The invention relates to the field of tungsten carbide, and in particular to a composite tungsten carbide powder and a preparation method thereof. Background Art

[0002] Supersonic spraying is an advanced thermal spraying technology used to deposit high-performance coatings on various substrate surfaces. This technology accelerates the material particles heated to a molten or semi-molten state to spray onto the workpiece surface through a high-speed gas flow to form a coating with excellent performance. Tungsten carbide powder is one of the spraying materials commonly used in supersonic spraying. It has good wear resistance, corrosion resistance, bonding strength and thermal stability.

[0003] The patent with publication number CN118218582A discloses a method for spray granulation of ultra-coarse-grained cemented carbide, wherein ultra-coarse-grained cemented carbide tungsten carbide powder, Co powder and a forming agent are ball-milled together, and then the obtained ball-milled slurry is spray-granulated, wherein the forming agent contains polyvinyl butyral, polyethylene glycol, stearic acid and oleic acid and optional alcohol at the same time, thereby improving the spray yield of the mixed product, and also improving the particle morphology and fluidity of the mixed product, and the residual carbon content after sintering is low, and the application prospect is broad. However, during sintering, the binder in the raw material is easily volatilized in a certain period of time, resulting in defects in the sintered product, such as morphological defects. Although the particle morphology of the mixed powder is improved, it is still insufficient. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing composite tungsten carbide powder, so as to solve the problem that in the preparation process of the existing tungsten carbide powder, the powder cannot effectively maintain its morphology due to the concentrated volatilization of the binder during sintering.

[0005] The present invention also aims to provide a composite tungsten carbide powder with good conveying performance.

[0006] The embodiments of the present invention are implemented by the following technical solutions:

[0007] A method for preparing composite tungsten carbide powder, comprising:

[0008] S100, by weight, 55-65 parts of tungsten carbide, 5-9 parts of cobalt powder, 1-3 parts of polyethylene glycol and 18-24 parts of alcohol are put into a ball mill for ball milling to obtain a slurry;

[0009] S200, the slurry is granulated through an atomizing drying tower to obtain a mixed powder;

[0010] S300, the mixed powder is sintered to obtain a powder block;

[0011] S400, powder block is used to obtain composite tungsten carbide powder by dry grinding;

[0012] The polyethylene glycol includes polymers with a molecular weight of 2,000-20,000.

[0013] Tungsten carbide and cobalt powder are raw materials and also components of composite tungsten carbide powder; polyethylene glycol is a binder, and the raw materials form a mixed powder through the bonding effect of polyethylene glycol; alcohol is an organic solvent, which helps the raw materials to disperse evenly. The present invention controls the molecular weight of polyethylene glycol so that when the mixed powder is sintered, the binder will not evaporate in a certain period of time, and the morphology of the mixed powder is maintained.

[0014] Before the slurry is sent to the atomizing drying tower, it can be stirred to prevent the slurry from stratification. During the sintering process, the polyethylene glycol gradually evaporates, and finally the cobalt powder binds the tungsten carbide to form a composite tungsten carbide.

[0015] Preferably, in parts by weight, the polyethylene glycol includes 15-25 parts of a first polymer, 15-25 parts of a second polymer, 15-25 parts of a third polymer, 15-25 parts of a fourth polymer and 15-25 parts of a fifth polymer; the first polymer is polyethylene glycol with a molecular weight of 2000, the second polymer is polyethylene glycol with a molecular weight of 5000, the third polymer is polyethylene glycol with a molecular weight of 10000, the fourth polymer is polyethylene glycol with a molecular weight of 15000, and the fifth polymer is polyethylene glycol with a molecular weight of 20000.

[0016] In order to ensure that the binder composition can maintain good bonding performance, the mixed powder after spray granulation has a certain structural stability and can reach a suitable particle size. One portion of the first polymer is based on the entire polyethylene glycol and is not equal to one portion of tungsten carbide.

[0017] Preferably, the ball milling temperature in S100 is 40-60° C., and the ball milling time is 30-60 h.

[0018] During the ball milling process, polyethylene glycol can also play a lubricating role. At the ball milling temperature of the present invention, no gasification of polyethylene glycol occurs.

[0019] Preferably, the atomizing drying tower in S200 comprises an atomizing disk, the rotation speed of the atomizing disk is 15000-25000 r / min, and the heating medium is nitrogen at 180-220°C.

[0020] Preferably, the heat preservation sintering temperature in S300 is 1100-1300° C., and the sintering time is 1.5-2.5 hours.

[0021] Preferably, the sintering operation in S300 includes: firstly heating the temperature to 180-220° C. for 1.5-2.5 hours, then heating the temperature to 380-420° C. for 8-12 hours, then heating the temperature to 1100-1300° C. for 6-10 hours and keeping the temperature for 1.5-2.5 hours.

[0022] During sintering, the heating rate and sintering time need to be reasonably regulated in accordance with the ratio of the binder in the present invention, so as to reduce the sintering time and improve the performance of the sintered product while minimizing the influence of the volatilization of polyethylene glycol on the morphology of the mixture. During sintering, the mixture can be divided into graphite boxes and sintered into powder blocks in the form of the inner cavity of the graphite box.

[0023] Preferably, the particle size of the mixed powder is 20-40 μm.

[0024] Since the binder in this case is not entirely high molecular weight polyethylene glycol, the bonding effect is lower than that of all high molecular weight polyethylene glycol, so the final particle size of the spray granulation needs to be regulated.

[0025] Preferably, the powder blocks in S400 are subjected to dry grinding, screening and air separation to obtain composite tungsten carbide powder with a particle size of 15-45 μm; the oversize during screening and the unqualified materials during air separation are returned to S100 for ball milling.

[0026] Air separation can select composite tungsten carbide with a particle size less than 5μm and retain finished products with qualified particle size.

[0027] Preferably, the alcohol discharged from the atomizing drying tower is condensed by a condensing device and then recycled to the ball milling process; the gaseous polyethylene glycol discharged by sintering in S300 is pumped to a recovery device by a vacuum pump.

[0028] Return material can reduce process costs.

[0029] A composite tungsten carbide powder prepared by the preparation method.

[0030] The present invention has at least the following beneficial effects:

[0031] The present invention regulates the molecular weight of polyethylene glycol so that it can not only maintain a good bonding effect, but also volatilize in batches during sintering, so that the morphology of the mixed powder is maintained, the defects of the sintered product are reduced, and the performance of the final product is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 This is a morphology picture of the composite tungsten carbide powder prepared by the preparation method of Example 3;

[0034] Figure 2 This is a morphology picture of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 1;

[0035] Figure 3 This is a morphology picture of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 2;

[0036] Figure 4 This is a morphology picture of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 3;

[0037] Figure 5 This is a morphology picture of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 4;

[0038] Figure 6 This is a morphology picture of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 5;

[0039] Figure 7 This is a morphology picture of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 6; DETAILED DESCRIPTION

[0040] In order to make the purpose, method scheme and advantages of the embodiments of the present invention clearer, the method scheme in the embodiments of the present invention is clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0041] Embodiment 1: A method for preparing a composite tungsten carbide powder, comprising:

[0042] S100, by weight, 55 parts of tungsten carbide, 5 parts of cobalt powder, 1 part of polyethylene glycol and 18 parts of alcohol are put into a ball mill for ball milling to obtain a slurry; the ball milling temperature is 40° C. and the ball milling time is 30 hours;

[0043] The polyethylene glycol includes 15 parts of a first polymer, 20 parts of a second polymer, 15 parts of a third polymer, 20 parts of a fourth polymer and 15 parts of a fifth polymer; the first polymer is polyethylene glycol with a molecular weight of 2000, the second polymer is polyethylene glycol with a molecular weight of 5000, the third polymer is polyethylene glycol with a molecular weight of 10000, the fourth polymer is polyethylene glycol with a molecular weight of 15000, and the fifth polymer is polyethylene glycol with a molecular weight of 20000.

[0044] S200, the slurry is sent to the mixing tank through a material tank for stirring and then sent to the atomizing drying tower. The slurry collides with the columns around the atomizing disk in the atomizing drying tower to form mist particles. At the same time, the mist particles are dried and de-alcoholized by nitrogen at 180°C. The alcohol is condensed by the condensing device and returned to the ball milling process for continued use. A small amount of ethanol gas is discharged from the discharge valve and enters the spray tower to be completely absorbed by water. The mixed powder obtained by granulation is discharged from the discharge port; the rotation speed of the atomizing disk is 15000r / min; the mixed powder is screened by a vibrating screen with a particle size of 20-40μm, and the screened material is returned to the ball milling process;

[0045] S300, the mixed powder of qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20cm*20cm*10cm is obtained by sintering; a vacuum pump and a recovery device are installed at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, the polyethylene glycol is volatilized and pumped to the recovery device by the vacuum pump for recycling and reuse. Part of the polyethylene glycol gas is treated and discharged. The sintering operation includes: first, it takes 1.5 hours to uniformly heat up to 180℃, then 8 hours to uniformly heat up to 380℃, and then 6 hours to uniformly heat up to 1100℃ and keep warm for 1.5 hours;

[0046] S400, the powder block is transported to the grinding area in a closed tank, and the powder block is placed in a dry mill (semi-enclosed) and ground into powder, and then transported to the screening area, and screened with a vibrating screen. The screened material is returned to the batching process as a return material for continued use, and the screened material (5-45μm) enters the next step of air selection to obtain a composite tungsten carbide powder with a particle size of 15-45μm.

[0047] Embodiment 2: A method for preparing a composite tungsten carbide powder, comprising:

[0048] S100, by weight, 65 parts of tungsten carbide, 9 parts of cobalt powder, 3 parts of polyethylene glycol and 24 parts of alcohol are put into a ball mill for ball milling to obtain a slurry; the ball milling temperature is 60° C. and the ball milling time is 60 h;

[0049] The polyethylene glycol includes 20 parts of a first polymer, 15 parts of a second polymer, 20 parts of a third polymer, 15 parts of a fourth polymer and 20 parts of a fifth polymer; the first polymer is polyethylene glycol with a molecular weight of 2000, the second polymer is polyethylene glycol with a molecular weight of 5000, the third polymer is polyethylene glycol with a molecular weight of 10000, the fourth polymer is polyethylene glycol with a molecular weight of 15000, and the fifth polymer is polyethylene glycol with a molecular weight of 20000.

[0050] S200, the slurry is sent to the mixing tank through the material tank for stirring and then sent to the atomizing drying tower. The slurry collides with the columns around the atomizing disk in the atomizing drying tower to form mist particles. At the same time, the nitrogen at 220°C dries the mist particles to remove alcohol. The alcohol is condensed through the condensing device and returned to the ball milling process for continued use. A small amount of ethanol gas is discharged from the discharge valve and enters the spray tower to be completely absorbed by water. The mixed powder obtained by granulation is discharged from the discharge port; the rotation speed of the atomizing disk is 25000r / min; the mixed powder is screened by a vibrating screen to select powder with a particle size of 20-40μm, and the screened material is returned to the ball milling process;

[0051] S300, the mixed powder of qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20cm*20cm*10cm is obtained by sintering; a vacuum pump and a recovery device are installed at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, the polyethylene glycol is volatilized and pumped to the recovery device by the vacuum pump for recycling and reuse. Part of the polyethylene glycol gas is treated and discharged. The sintering operation includes: first, uniformly heating to 220℃ for 2.5h, then uniformly heating to 420℃ for 12h, then uniformly heating to 1300℃ for 10h and keeping warm for 2.5h;

[0052] S400, the powder block is transported to the grinding area in a closed tank, and the powder block is placed in a dry mill (semi-enclosed) and ground into powder, and then transported to the screening area, and screened with a vibrating screen. The screened material is returned to the batching process as a return material for continued use, and the screened material (5-45μm) enters the next step of air selection to obtain a composite tungsten carbide powder with a particle size of 15-45μm.

[0053] Embodiment 3: A method for preparing a composite tungsten carbide powder, comprising:

[0054] S100, by weight, 60 parts of tungsten carbide, 7 parts of cobalt powder, 2 parts of polyethylene glycol and 20 parts of alcohol are put into a ball mill for ball milling to obtain a slurry; the ball milling temperature is 50° C. and the ball milling time is 48 hours;

[0055] The polyethylene glycol includes 18 parts of a first polymer, 18 parts of a second polymer, 18 parts of a third polymer, 18 parts of a fourth polymer and 18 parts of a fifth polymer; the first polymer is polyethylene glycol with a molecular weight of 2000, the second polymer is polyethylene glycol with a molecular weight of 5000, the third polymer is polyethylene glycol with a molecular weight of 10000, the fourth polymer is polyethylene glycol with a molecular weight of 15000, and the fifth polymer is polyethylene glycol with a molecular weight of 20000.

[0056] S200, the slurry is sent to the mixing tank through the material tank for stirring and then sent to the atomizing drying tower. The slurry collides with the columns around the atomizing disk in the atomizing drying tower to form mist particles. At the same time, the nitrogen at 200°C dries the mist particles to remove alcohol. The alcohol is condensed through the condensing device and returned to the ball milling process for continued use. A small amount of ethanol gas is discharged from the discharge valve and enters the spray tower to be completely absorbed by water. The mixed powder obtained by granulation is discharged from the discharge port; the rotation speed of the atomizing disk is 20000r / min; the mixed powder is screened by a vibrating screen with a particle size of 20-40μm, and the screened material is returned to the ball milling process;

[0057] S300, the mixed powder of qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20cm*20cm*10cm is obtained by sintering; a vacuum pump and a recovery device are installed at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, the polyethylene glycol volatilizes and is pumped to the recovery device by the vacuum pump for recycling and reuse. Part of the polyethylene glycol gas is treated and discharged. The sintering operation includes: first, uniformly heating to 200℃ for 2h, then uniformly heating to 400℃ for 10h, then uniformly heating to 1200℃ for 8h and keeping warm for 2h;

[0058] S400, the powder block is transported to the grinding area in a closed tank, and the powder block is placed in a dry mill (semi-enclosed) and ground into powder, and then transported to the screening area, and screened with a vibrating screen. The screened material is returned to the batching process as a return material for continued use, and the screened material (5-45μm) enters the next step of air selection to obtain a composite tungsten carbide powder with a particle size of 15-45μm.

[0059] Comparative Example 1: A method for preparing a composite tungsten carbide powder, comprising:

[0060] S100, by weight, 60 parts of tungsten carbide, 7 parts of cobalt powder, 2 parts of polyethylene glycol and 20 parts of alcohol are put into a ball mill for ball milling to obtain a slurry; the ball milling temperature is 50° C. and the ball milling time is 48 hours;

[0061] The polyethylene glycol includes 18 parts of a first polymer, 18 parts of a third polymer, 18 parts of a fourth polymer and 18 parts of a fifth polymer; the first polymer is polyethylene glycol with a molecular weight of 2000, the third polymer is polyethylene glycol with a molecular weight of 10000, the fourth polymer is polyethylene glycol with a molecular weight of 15000, and the fifth polymer is polyethylene glycol with a molecular weight of 20000.

[0062] S200, the slurry is sent to the mixing tank through the material tank for stirring and then sent to the atomizing drying tower. The slurry collides with the columns around the atomizing disk in the atomizing drying tower to form mist particles. At the same time, the nitrogen at 200°C dries the mist particles to remove alcohol. The alcohol is condensed through the condensing device and returned to the ball milling process for continued use. A small amount of ethanol gas is discharged from the discharge valve and enters the spray tower to be completely absorbed by water. The mixed powder obtained by granulation is discharged from the discharge port; the rotation speed of the atomizing disk is 20000r / min; the mixed powder is screened by a vibrating screen with a particle size of 20-40μm, and the screened material is returned to the ball milling process;

[0063] S300, the mixed powder of qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20cm*20cm*10cm is obtained by sintering; a vacuum pump and a recovery device are installed at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, the polyethylene glycol volatilizes and is pumped to the recovery device by the vacuum pump for recycling and reuse. Part of the polyethylene glycol gas is treated and discharged. The sintering operation includes: first, uniformly heating to 200℃ for 2h, then uniformly heating to 400℃ for 10h, then uniformly heating to 1200℃ for 8h and keeping warm for 2h;

[0064] S400, the powder block is transported to the grinding area in a closed tank, and the powder block is placed in a dry mill (semi-enclosed) and ground into powder, and then transported to the screening area, and screened with a vibrating screen. The screened material is returned to the batching process as a return material for continued use, and the screened material (5-45μm) enters the next step of air selection to obtain a composite tungsten carbide powder with a particle size of 15-45μm.

[0065] Comparative Example 2: A method for preparing a composite tungsten carbide powder, comprising:

[0066] S100, by weight, 60 parts of tungsten carbide, 7 parts of cobalt powder, 2 parts of polyethylene glycol and 20 parts of alcohol are put into a ball mill for ball milling to obtain a slurry; the ball milling temperature is 50° C. and the ball milling time is 48 hours;

[0067] The polyethylene glycol includes 18 parts of a first polymer, 18 parts of a second polymer, 18 parts of a third polymer, and 18 parts of a fourth polymer; the first polymer is polyethylene glycol with a molecular weight of 2000, the second polymer is polyethylene glycol with a molecular weight of 5000, the third polymer is polyethylene glycol with a molecular weight of 10000, and the fourth polymer is polyethylene glycol with a molecular weight of 15000.

[0068] S200, the slurry is sent to the mixing tank through the material tank for stirring and then sent to the atomizing drying tower. The slurry collides with the columns around the atomizing disk in the atomizing drying tower to form mist particles. At the same time, the nitrogen at 200°C dries the mist particles to remove alcohol. The alcohol is condensed through the condensing device and returned to the ball milling process for continued use. A small amount of ethanol gas is discharged from the discharge valve and enters the spray tower to be completely absorbed by water. The mixed powder obtained by granulation is discharged from the discharge port; the rotation speed of the atomizing disk is 20000r / min; the mixed powder is screened by a vibrating screen with a particle size of 20-40μm, and the screened material is returned to the ball milling process;

[0069] S300, the mixed powder of qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20cm*20cm*10cm is obtained by sintering; a vacuum pump and a recovery device are installed at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, the polyethylene glycol volatilizes and is pumped to the recovery device by the vacuum pump for recycling and reuse. Part of the polyethylene glycol gas is treated and discharged. The sintering operation includes: first, uniformly heating to 200℃ for 2h, then uniformly heating to 400℃ for 10h, then uniformly heating to 1200℃ for 8h and keeping warm for 2h;

[0070] S400, the powder block is transported to the grinding area in a closed tank, and the powder block is placed in a dry mill (semi-enclosed) and ground into powder, and then transported to the screening area, and screened with a vibrating screen. The screened material is returned to the batching process as a return material for continued use, and the screened material (5-45μm) enters the next step of air selection to obtain a composite tungsten carbide powder with a particle size of 15-45μm.

[0071] Comparative Example 3: A method for preparing a composite tungsten carbide powder, comprising:

[0072] S100, by weight, 60 parts of tungsten carbide, 7 parts of cobalt powder, 2 parts of polyethylene glycol and 20 parts of alcohol are put into a ball mill for ball milling to obtain a slurry; the ball milling temperature is 50° C. and the ball milling time is 48 hours;

[0073] The polyethylene glycol includes a fifth polymer; the fifth polymer is polyethylene glycol with a molecular weight of 20,000.

[0074] S200, the slurry is sent to the mixing tank through the material tank for stirring and then sent to the atomizing drying tower. The slurry collides with the columns around the atomizing disk in the atomizing drying tower to form mist particles. At the same time, the nitrogen at 200°C dries the mist particles to remove alcohol. The alcohol is condensed through the condensing device and returned to the ball milling process for continued use. A small amount of ethanol gas is discharged from the discharge valve and enters the spray tower to be completely absorbed by water. The mixed powder obtained by granulation is discharged from the discharge port; the rotation speed of the atomizing disk is 20000r / min; the mixed powder is screened by a vibrating screen with a particle size of 20-40μm, and the screened material is returned to the ball milling process;

[0075] S300, the mixed powder of qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20cm*20cm*10cm is obtained by sintering; a vacuum pump and a recovery device are installed at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, the polyethylene glycol volatilizes and is pumped to the recovery device by the vacuum pump for recycling and reuse. Part of the polyethylene glycol gas is treated and discharged. The sintering operation includes: first, uniformly heating to 200℃ for 2h, then uniformly heating to 400℃ for 10h, then uniformly heating to 1200℃ for 8h and keeping warm for 2h;

[0076] S400, the powder block is transported to the grinding area in a closed tank, and the powder block is placed in a dry mill (semi-enclosed) and ground into powder, and then transported to the screening area, and screened with a vibrating screen. The screened material is returned to the batching process as a return material for continued use, and the screened material (5-45μm) enters the next step of air selection to obtain a composite tungsten carbide powder with a particle size of 15-45μm.

[0077] Comparative Example 4: A method for preparing a composite tungsten carbide powder, comprising:

[0078] S100, by weight, 60 parts of tungsten carbide, 7 parts of cobalt powder, 2 parts of polyethylene glycol and 20 parts of alcohol are put into a ball mill for ball milling to obtain a slurry; the ball milling temperature is 50° C. and the ball milling time is 48 hours;

[0079] The polyethylene glycol comprises a second polymer, and the second polymer is polyethylene glycol with a molecular weight of 5000.

[0080] S200, the slurry is sent to the mixing tank through the material tank for stirring and then sent to the atomizing drying tower. The slurry collides with the columns around the atomizing disk in the atomizing drying tower to form mist particles. At the same time, the nitrogen at 200°C dries the mist particles to remove alcohol. The alcohol is condensed through the condensing device and returned to the ball milling process for continued use. A small amount of ethanol gas is discharged from the discharge valve and enters the spray tower to be completely absorbed by water. The mixed powder obtained by granulation is discharged from the discharge port; the rotation speed of the atomizing disk is 20000r / min; the mixed powder is screened by a vibrating screen with a particle size of 20-40μm, and the screened material is returned to the ball milling process;

[0081] S300, the mixed powder of qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20cm*20cm*10cm is obtained by sintering; a vacuum pump and a recovery device are installed at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, the polyethylene glycol volatilizes and is pumped to the recovery device by the vacuum pump for recycling and reuse. Part of the polyethylene glycol gas is treated and discharged. The sintering operation includes: first, uniformly heating to 200℃ for 2h, then uniformly heating to 400℃ for 10h, then uniformly heating to 1200℃ for 8h and keeping warm for 2h;

[0082] S400, the powder block is transported to the grinding area in a closed tank, and the powder block is placed in a dry mill (semi-enclosed) and ground into powder, and then transported to the screening area, and screened with a vibrating screen. The screened material is returned to the batching process as a return material for continued use, and the screened material (5-45μm) enters the next step of air selection to obtain a composite tungsten carbide powder with a particle size of 15-45μm.

[0083] Comparative Example 5: A method for preparing a composite tungsten carbide powder, comprising:

[0084] S100, by weight, 60 parts of tungsten carbide, 7 parts of cobalt powder, 2 parts of polyethylene glycol and 20 parts of alcohol are put into a ball mill for ball milling to obtain a slurry; the ball milling temperature is 50° C. and the ball milling time is 48 hours;

[0085] The polyethylene glycol includes 18 parts of a first polymer, 18 parts of a second polymer, 18 parts of a third polymer, 18 parts of a fourth polymer and 18 parts of a fifth polymer; the first polymer is polyethylene glycol with a molecular weight of 2000, the second polymer is polyethylene glycol with a molecular weight of 5000, the third polymer is polyethylene glycol with a molecular weight of 10000, the fourth polymer is polyethylene glycol with a molecular weight of 15000, and the fifth polymer is polyethylene glycol with a molecular weight of 20000.

[0086] S200, the slurry is sent to the mixing tank through the material tank for stirring and then sent to the atomizing drying tower. The slurry collides with the columns around the atomizing disk in the atomizing drying tower to form mist particles. At the same time, the nitrogen at 200°C dries the mist particles to remove alcohol. The alcohol is condensed through the condensing device and returned to the ball milling process for continued use. A small amount of ethanol gas is discharged from the discharge valve and enters the spray tower to be completely absorbed by water. The mixed powder obtained by granulation is discharged from the discharge port; the rotation speed of the atomizing disk is 20000r / min; the mixed powder is screened by a vibrating screen with a particle size of 20-40μm, and the screened material is returned to the ball milling process;

[0087] S300, the mixed powder of qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20cm*20cm*10cm is obtained by sintering; a vacuum pump and a recovery device are installed at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, the polyethylene glycol volatilizes and is pumped to the recovery device by the vacuum pump for recycling and reuse. Part of the polyethylene glycol gas is treated and discharged. The sintering operation includes: first, the temperature is raised to 1200℃ at a uniform speed for 20 hours and kept at this temperature for 2 hours;

[0088] S400, the powder block is transported to the grinding area in a closed tank, and the powder block is placed in a dry mill (semi-enclosed) and ground into powder, and then transported to the screening area, and screened with a vibrating screen. The screened material is returned to the batching process as a return material for continued use, and the screened material (5-45μm) enters the next step of air selection to obtain a composite tungsten carbide powder with a particle size of 15-45μm.

[0089] Comparative Example 6: A method for preparing a composite tungsten carbide powder, comprising:

[0090] S100, by weight, 60 parts of tungsten carbide, 7 parts of cobalt powder, 2 parts of polyethylene glycol and 20 parts of alcohol are put into a ball mill for ball milling to obtain a slurry; the ball milling temperature is 50° C. and the ball milling time is 48 hours;

[0091] The polyethylene glycol includes 18 parts of a first polymer, 18 parts of a second polymer, 18 parts of a third polymer, 18 parts of a fourth polymer and 18 parts of a fifth polymer; the first polymer is polyethylene glycol with a molecular weight of 2000, the second polymer is polyethylene glycol with a molecular weight of 5000, the third polymer is polyethylene glycol with a molecular weight of 10000, the fourth polymer is polyethylene glycol with a molecular weight of 15000, and the fifth polymer is polyethylene glycol with a molecular weight of 20000.

[0092] S200, the slurry is sent to the mixing tank through the material tank for stirring and then sent to the atomizing drying tower. The slurry collides with the columns around the atomizing disk in the atomizing drying tower to form mist particles. At the same time, the nitrogen at 200°C dries the mist particles to remove alcohol. The alcohol is condensed through the condensing device and returned to the ball milling process for continued use. A small amount of ethanol gas is discharged from the discharge valve and enters the spray tower to be completely absorbed by water. The mixed powder obtained by granulation is discharged from the discharge port; the rotation speed of the atomizing disk is 20000r / min; the mixed powder is screened by a vibrating screen with a particle size of 20-40μm, and the screened material is returned to the ball milling process;

[0093] S300, the mixed powder of qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20cm*20cm*10cm is obtained by sintering; a vacuum pump and a recovery device are installed at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, the polyethylene glycol volatilizes and is pumped to the recovery device by the vacuum pump for recycling and reuse. Part of the polyethylene glycol gas is treated and discharged. The sintering operation includes: first, heating to 400℃ at a constant speed for 12h, then heating to 1200℃ at a constant speed for 8h and keeping warm for 2h;

[0094] S400, the powder block is transported to the grinding area in a closed tank, and the powder block is placed in a dry mill (semi-enclosed) and ground into powder, and then transported to the screening area, and screened with a vibrating screen. The screened material is returned to the batching process as a return material for continued use, and the screened material (5-45μm) enters the next step of air selection to obtain a composite tungsten carbide powder with a particle size of 15-45μm.

[0095] Experiment 1: According to the preparation methods of Examples 1-3 and Comparative Examples 1-6, 20 μm composite tungsten carbide powder was prepared and its bulk density (g / cm 3) and fluidity (s / 50g), the bulk density was tested in accordance with GB / T 1479-1984, and the fluidity was tested in accordance with GB / T 1482-2010. Each test was performed five times and the average value was taken. The test results are shown in Table 1.

[0096] Table 1

[0097]

[0098] It can be seen from Examples 1-3 that the composite tungsten carbide powder prepared by the preparation method of the present invention has good bulk density and fluidity, and can be better applied to supersonic spraying; the composite tungsten carbide powder prepared by the preparation method provided in Example 3 has the best fluidity.

[0099] From the comparison between Comparative Examples 1-4 and Example 3, it can be seen that the composite tungsten carbide powder prepared by using the polyethylene glycol molecular weight ratio provided by the present invention has better fluidity.

[0100] From the comparison between Comparative Examples 5-6 and Example 3, it can be seen that the sintering process provided by the present invention can effectively improve the fluidity of the product.

[0101] Test 2: A 20 μm composite tungsten carbide powder was prepared according to the preparation methods of Examples 1-3 and Comparative Examples 1-6, and the powder coating rate (%) of the powder during supersonic spraying was tested. The powder coating rate is the percentage between the weight of the powder coating formed on the substrate and the total weight of the powder during supersonic spraying. Each group of tests was measured five times and the average value was taken. The test results are shown in Table 2.

[0102] Table 2

[0103]

[0104] It can be seen from the test results of Examples 1-3 that the composite tungsten carbide powder prepared by the preparation methods of Examples 1-3 of the present invention has a good powder loading rate.

[0105] From the comparison between Comparative Examples 1-4 and Example 3, it can be seen that the change in the ratio of polyethylene glycol leads to a decrease in the morphology retention effect of the mixed powder, which in turn leads to a significant decrease in the powder loading rate.

[0106] From the comparison between Comparative Examples 5-6 and Example 3, it can be seen that the temperature regulation during sintering in the present invention can effectively improve the powder loading rate of the product.

[0107] Experiment 3: Electron Microscope Image

[0108] pass Figure 1 and Figure 2-7 It can be seen from the comparison that the composite tungsten carbide powder prepared in Comparative Examples 1-6 is prone to the following defects: shape deformation, pores and fractures on the surface, etc.

[0109] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing composite tungsten carbide powder, characterized in that: include: S100, by weight, putting 55-65 parts of tungsten carbide, 5-9 parts of cobalt powder, 1-3 parts of polyethylene glycol and 18-24 parts of alcohol into a ball mill for ball milling to obtain a slurry; S200, the slurry is granulated through an atomizing drying tower to obtain a mixed powder; S300, the mixed powder is sintered to obtain a powder block; S400, powder block is used to obtain composite tungsten carbide powder by dry grinding; The polyethylene glycol includes polymers with a molecular weight of 2,000-20,000.

2. The method for preparing composite tungsten carbide powder according to claim 1, characterized in that: In parts by weight, the polyethylene glycol comprises 15-25 parts of a first polymer, 15-25 parts of a second polymer, 15-25 parts of a third polymer, 15-25 parts of a fourth polymer and 15-25 parts of a fifth polymer; The first polymer is polyethylene glycol with a molecular weight of 2000, the second polymer is polyethylene glycol with a molecular weight of 5000, the third polymer is polyethylene glycol with a molecular weight of 10000, the fourth polymer is polyethylene glycol with a molecular weight of 15000, and the fifth polymer is polyethylene glycol with a molecular weight of 20000.

3. The method for preparing composite tungsten carbide powder according to claim 1, characterized in that: The ball milling temperature in S100 is 40-60° C., and the ball milling time is 30-60 h.

4. The method for preparing composite tungsten carbide powder according to claim 1, characterized in that: The atomizing drying tower in S200 includes an atomizing disk, the rotation speed of the atomizing disk is 15000-25000 r / min, and the heating medium is nitrogen at 180-220°C.

5. The method for preparing composite tungsten carbide powder according to any one of claims 1 to 4, characterized in that: The heat preservation sintering temperature in S300 is 1100-1300° C., and the sintering time is 1.5-2.5 hours.

6. The method for preparing composite tungsten carbide powder according to claim 5, characterized in that: The sintering operation in S300 includes: firstly heating the temperature to 180-220° C. for 1.5-2.5 hours, then heating the temperature to 380-420° C. for 8-12 hours, then heating the temperature to 1100-1300° C. for 6-10 hours and keeping the temperature for 1.5-2.5 hours.

7. The method for preparing composite tungsten carbide powder according to claim 5, characterized in that: The particle size of the mixed powder is 20-40 μm.

8. The method for preparing composite tungsten carbide powder according to claim 5, characterized in that: The powder blocks in S400 are subjected to dry grinding, screening and air separation to obtain composite tungsten carbide powder with a particle size of 15-45 μm; the oversize during screening and the unqualified materials during air separation are returned to S100 for ball milling.

9. The method for preparing composite tungsten carbide powder according to claim 5, characterized in that: The alcohol discharged from the atomizing drying tower is condensed by a condensing device and then recycled to the ball milling process; the gaseous polyethylene glycol discharged by sintering in S300 is pumped to a recovery device by a vacuum pump.

10. A composite tungsten carbide powder obtained by the preparation method according to any one of claims 1 to 9.

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