A composite tungsten carbide powder and its preparation method

Abstract

The present invention relates to the field of tungsten carbide. To solve the problem that during the preparation of existing tungsten carbide powder, due to the concentrated volatilization of the binder during sintering, the powder body cannot effectively maintain its morphology, a preparation method of composite tungsten carbide powder is provided, including: 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; 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. The powder block is ground by a dry grinding machine to obtain composite tungsten carbide powder; the polyethylene glycol includes polymers with a molecular weight of 2000 - 20000. By regulating the molecular weight of the polyethylene glycol, the present invention enables it to not only maintain a good binding 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.

Description

Technical Field

[0001] The present invention relates to the field of tungsten carbide, and more particularly, 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 the surfaces of various substrates. This technology accelerates material particles heated to a molten or semi-molten state by a high-speed gas flow and sprays them onto the workpiece surface to form a coating with excellent properties. Tungsten carbide powder is one of the commonly used spraying materials in supersonic spraying, which has characteristics such as good wear resistance, corrosion resistance, bonding strength, and thermal stability.

[0003] The patent with the publication number CN118218582A discloses a spray granulation method for ultra-coarse-grained cemented carbide, which ball-mills ultra-coarse-grained cemented carbide tungsten carbide powder, Co powder, and a forming agent together, and then spray granulates the obtained ball-milled slurry. The forming agent contains polyvinyl butyral, polyethylene glycol, stearic acid, and oleic acid, and optionally alcohol, which improves the spray yield of the mixture product, and can also improve the particle morphology and fluidity of the mixture. At the same time, the residual carbon content after sintering is low, and the application prospect is broad. However, during sintering, the binder in the raw materials is likely to volatilize concentratedly in a certain period, resulting in defects in the sintered product, such as morphological defects. Although the particle morphology of the mixture powder is improved, there are still deficiencies. Summary of the Invention

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

[0005] The purpose of the present invention is also to provide a composite tungsten carbide powder with good conveying performance.

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

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

[0008] S100. By weight, put 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;

[0009] S200. Granulate the slurry through an atomizing drying tower to obtain a mixed powder;

[0010] S300. Sinter the mixed powder to obtain a powder block;

[0011] S400. The composite tungsten carbide powder is obtained by a dry grinding machine from tungsten carbide powder blocks;

[0012] The polyethylene glycol includes polymers with a molecular weight of 2000 - 20000.

[0013] Tungsten carbide and cobalt powder are raw materials and also components of the composite tungsten carbide powder; polyethylene glycol is a binder, and the raw materials form a mixed powder through the binding action of polyethylene glycol; alcohol is an organic solvent to help the raw materials disperse evenly. In the present invention, by regulating the molecular weight of polyethylene glycol, the binder will not volatilize concentratedly in a certain period during sintering, and the morphology of the mixed powder is maintained.

[0014] Before the slurry is fed into the atomization drying tower, it can be stirred first to prevent the slurry from stratifying. During the sintering process, polyethylene glycol gradually volatilizes, and finally cobalt powder binds tungsten carbide to form composite tungsten carbide.

[0015] Preferably, 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 keep good binding performance of the binder composition, make the mixed powder after spray granulation have a certain structural stability and reach a suitable particle size. One part of the first polymer, etc. is based on the whole polyethylene glycol and is not equal to one part of tungsten carbide, etc.

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

[0018] During ball milling, polyethylene glycol can also play a lubricating role, and at the ball milling temperature of the present invention, there is no gasification phenomenon of polyethylene glycol.

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

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

[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] Returning materials 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] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0033] Figure 1 Morphology diagram of the composite tungsten carbide powder prepared by the preparation method of Example 3;

[0034] Figure 2 Morphology diagram of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 1;

[0035] Figure 3 Morphology diagram of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 2;

[0036] Figure 4 Morphology diagram of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 3;

[0037] Figure 5 Morphology diagram of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 4;

[0038] Figure 6 Morphology diagram of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 5;

[0039] Figure 7 Morphology diagram of the composite tungsten carbide powder prepared by the preparation method of Comparative Example 6; Detailed implementation manners

[0040] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0041] Example 1: A preparation method of 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 temperature of the ball milling is 40°C, and the ball milling time is 30 h;

[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 from the material tank to the stirring tank, stirred, and then sent to the atomization drying tower. The slurry collides with the column around the atomization disk in the atomization drying tower to form misty particles. At the same time, nitrogen gas at 180 °C dries and removes alcohol from the misty particles. After the alcohol is condensed by the condensation device, it returns to the ball milling process for continued use. A small amount of ethanol gas is discharged through 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 atomization disk is 15000 r / min; the mixed powder is screened by a vibrating screen to obtain powder with a particle size of 20 - 40 μm, and the oversize material is returned to the ball milling process;

[0045] S300. The mixed powder with qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20 cm * 20 cm * 10 cm is obtained through sintering; a vacuum pump and a recovery device are arranged 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 part of the polyethylene glycol gas is discharged after being treated. The sintering operation includes: first, heating uniformly to 180 °C at a constant speed for 1.5 h, then heating uniformly to 380 °C at a constant speed for 8 h, and then heating uniformly to 1100 °C at a constant speed for 6 h and holding for 1.5 h;

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

[0047] Example 2: A method for preparing a composite tungsten carbide powder, including:

[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 temperature of the ball milling 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 from the material tank to the stirring tank, stirred, and then sent to the atomization drying tower. The slurry collides with the column around the atomization disk in the atomization drying tower to form misty particles. At the same time, nitrogen gas at 220 °C dries and removes alcohol from the misty particles. After the alcohol is condensed by the condensation device, it returns to the ball milling process for continued use. A small amount of ethanol gas is discharged through 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 atomization disk is 25000 r / min; the mixed powder is screened by a vibrating screen to obtain powder with a particle size of 20 - 40 μm, and the oversize material is returned to the ball milling process.

[0051] S300. The mixed powder with qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20 cm * 20 cm * 10 cm is obtained through sintering; a vacuum pump and a recovery device are arranged 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, and part of the polyethylene glycol gas is discharged after treatment. The sintering operation includes: first, heating up to 220 °C at a uniform speed for 2.5 h, then heating up to 420 °C at a uniform speed for 12 h, and then heating up to 1300 °C at a uniform speed for 10 h and holding for 2.5 h.

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

[0053] Example 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 temperature of ball milling is 50 °C, and the ball milling time is 48 h.

[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 from the material tank to the stirring tank, stirred, and then sent to the atomization drying tower. The slurry collides with the cylinder around the atomization disk in the atomization drying tower to form fog-like particles. At the same time, nitrogen gas at 200 °C dries the fog-like particles to remove alcohol. After the alcohol is condensed by the condensing device, it returns to the ball milling process for continued use. A small amount of ethanol gas is discharged through 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 atomization disk is 20000 r / min; the mixed powder is screened by a vibrating screen to obtain powder with a particle size of 20 - 40 μm, and the oversize material is returned to the ball milling process.

[0057] S300. The mixed powder with qualified particle size is transported to an electric sintering furnace in a closed tank, and a powder block of 20 cm * 20 cm * 10 cm is obtained through sintering; a vacuum pump and a recovery device are arranged 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, and part of the polyethylene glycol gas is discharged after treatment. The sintering operation includes: first, heating uniformly to 200 °C at a constant speed for 2 h, then heating uniformly to 400 °C at a constant speed for 10 h, and then heating uniformly to 1200 °C at a constant speed for 8 h and holding for 2 h.

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

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

[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 temperature of the ball milling is 50 °C, and the ball milling time is 48 h.

[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 from the material tank to the stirring tank, stirred, and then sent to the atomization drying tower. The slurry collides with the column around the atomization disk in the atomization drying tower to form misty particles. At the same time, nitrogen gas at 200°C dries the misty particles to remove alcohol. After the alcohol is condensed by the condensing device, it returns to the ball milling process for continued use. A small amount of ethanol gas is discharged through 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 atomization disk is 20000 r / min; the mixed powder is screened by a vibrating screen to obtain powder with a particle size of 20 - 40 μm, and the oversize material is returned to the ball milling process.

[0063] S300. The mixed powder with qualified particle size is transported to an electric sintering furnace in a closed tank, and a powder block of 20 cm * 20 cm * 10 cm is obtained through sintering; a vacuum pump and a recovery device are arranged 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, and part of the polyethylene glycol gas is discharged after treatment. The sintering operation includes: first, heating uniformly to 200°C at a constant speed for 2 h, then heating uniformly to 400°C at a constant speed for 10 h, and then heating uniformly to 1200°C at a constant speed for 8 h and holding for 2 h.

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

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

[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 temperature of the ball milling is 50°C, and the ball milling time is 48 h.

[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] The S200: The slurry is sent from the material tank to the stirring tank, stirred, and then sent to the atomization drying tower. The slurry collides with the column around the atomization disk in the atomization drying tower to form misty particles. At the same time, nitrogen gas at 200°C dries the misty particles to remove alcohol. After the alcohol is condensed by the condensation device, it returns to the ball milling process for continued use. A small amount of ethanol gas is discharged through 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 atomization disk is 20,000 r / min. The mixed powder is screened by a vibrating screen to select powder with a particle size of 20 - 40 μm, and the oversize material is returned to the ball milling process;

[0069] The S300: The mixed powder with qualified particle size is transported to the electric sintering furnace in a closed tank, and a powder block of 20 cm * 20 cm * 10 cm is obtained through sintering. A vacuum pump and a recovery device are arranged at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, polyethylene glycol volatilizes and is pumped to the recovery device by the vacuum pump for recycling, and part of the polyethylene glycol gas is discharged after treatment. The sintering operation includes: first, heating up to 200°C at a uniform speed for 2 h, then heating up to 400°C at a uniform speed for 10 h, and then heating up to 1200°C at a uniform speed for 8 h and holding for 2 h;

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

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

[0072] The 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 temperature of the ball milling is 50°C, and the ball milling time is 48 h;

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

[0074] The S200: The slurry is sent from the material tank to the stirring tank, stirred, and then sent to the atomization drying tower. The slurry collides with the column around the atomization disk in the atomization drying tower to form misty particles. At the same time, nitrogen gas at 200°C dries the misty particles to remove alcohol. After the alcohol is condensed by the condensation device, it returns to the ball milling process for continued use. A small amount of ethanol gas is discharged through 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 atomization disk is 20,000 r / min. The mixed powder is screened by a vibrating screen to select powder with a particle size of 20 - 40 μm, and the oversize material is returned to the ball milling process;

[0075] The mixed powder with qualified particle size is transported to an electric sintering furnace in a closed tank, and a powder block of 20 cm * 20 cm * 10 cm is obtained through sintering. A vacuum pump and a recovery device are arranged at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, polyethylene glycol volatilizes and is pumped by the vacuum pump to the recovery device for recycling, and part of the polyethylene glycol gas is discharged after treatment. The sintering operation includes: first, heating uniformly to 200 °C at a constant speed for 2 h, then heating uniformly to 400 °C at a constant speed for 10 h, and then heating uniformly to 1200 °C at a constant speed for 8 h and holding for 2 h;

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

[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 temperature of the ball milling is 50 °C, and the ball milling time is 48 h;

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

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

[0081] S300. The mixed powder with qualified particle size is transported to an electric sintering furnace in a closed tank, and a powder block of 20 cm * 20 cm * 10 cm is obtained through sintering. A vacuum pump and a recovery device are arranged at the rear end of the sintering furnace to evacuate the sintering furnace. At this time, polyethylene glycol volatilizes and is pumped by the vacuum pump to the recovery device for recycling, and part of the polyethylene glycol gas is discharged after treatment. The sintering operation includes: first, heating uniformly to 200 °C at a constant speed for 2 h, then heating uniformly to 400 °C at a constant speed for 10 h, and then heating uniformly to 1200 °C at a constant speed for 8 h and holding for 2 h;

[0082] S400. Transfer the powder blocks to the grinding and dispersing area in a closed tank, place the powder blocks in a dry mill (semi-closed) to grind them into powder, then transport them to the screening area and screen them with a vibrating screen. The oversize materials are returned as recycled materials to the batching process for continued use, and the undersize materials (5 - 45 μm) enter the next air separation step to obtain composite tungsten carbide powder with a particle size of 15 - 45 μm.

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

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

[0085] The polyethylene glycol includes 18 parts of the first polymer, 18 parts of the second polymer, 18 parts of the third polymer, 18 parts of the fourth polymer, and 18 parts of the 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. Send the slurry to a stirring tank through a trough for stirring and then to an atomization drying tower. The slurry collides with the column around the atomization disk in the atomization drying tower to form fog-like particles. At the same time, nitrogen gas at 200 °C dries the fog-like particles to remove alcohol. After the alcohol is condensed by a condensing device, it returns to the ball milling process for continued use. A small amount of ethanol gas is discharged through an exhaust valve and enters a 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 atomization disk is 20000 r / min; the mixed powder is screened through a vibrating screen to select powder with a particle size of 20 - 40 μm, and the oversize materials are recycled and returned to the ball milling process;

[0087] S300. Transfer the mixed powder with qualified particle size to an electric sintering furnace in a closed tank, and obtain a powder block of 20 cm * 20 cm * 10 cm through sintering; a vacuum pump and a recovery device are arranged 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, and part of the polyethylene glycol gas is discharged after treatment. The sintering operation includes: first, uniformly heat to 1200 °C at a constant speed for 20 h and keep it warm for 2 h;

[0088] S400. Transfer the powder blocks to the grinding and dispersing area in a closed tank, place the powder blocks in a dry mill (semi-closed) to grind them into powder, then transport them to the screening area and screen them with a vibrating screen. The oversize materials are returned as recycled materials to the batching process for continued use, and the undersize materials (5 - 45 μm) enter the next air separation step to obtain composite tungsten carbide powder with a particle size of 15 - 45 μm.

[0089] Comparative Example 6: A preparation method of 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 temperature of the ball milling is 50 °C, and the ball milling time is 48 h;

[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 a stirring tank by a feeding trough, stirred, and then sent to an atomization drying tower. The slurry collides with the column around the atomization disk in the atomization drying tower to form misty particles. At the same time, after the misty particles are dried and de-alcoholized by nitrogen gas at 200 °C, the alcohol is condensed by a condensing device and then returned to the ball milling process for continued use. A small amount of ethanol gas is discharged through a discharge valve and enters a spray tower to be completely absorbed by water. The granulated mixed powder is discharged from the discharge port; the rotation speed of the atomization disk is 20000 r / min; the mixed powder is screened by a vibrating screen to select powder with a particle size of 20 - 40 μm, and the oversize material is returned to the ball milling process;

[0093] S300: The mixed powder with qualified particle size is transported to an electric sintering furnace in a closed tank, and a powder block of 20 cm * 20 cm * 10 cm is obtained through sintering; a vacuum pump and a recovery device are arranged 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 part of the polyethylene glycol gas is discharged after treatment. The sintering operation includes: first, heating uniformly to 400 °C at a constant speed for 12 h, and then heating uniformly to 1200 °C at a constant speed for 8 h and holding for 2 h;

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

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

[0096] Table 1

[0097]

[0098] As can be seen from Examples 1-3, the composite tungsten carbide powder prepared by the preparation method of the present invention has good loose 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] As can be seen from the comparison between Comparative Examples 1-4 and Example 3, the composite tungsten carbide powder prepared with the polyethylene glycol molecular weight ratio provided by the present invention has better fluidity.

[0100] As can be seen from the comparison between Comparative Examples 5-6 and Example 3, by using the sintering process provided by the present invention, the fluidity of the product can be effectively improved.

[0101] Experiment 2: 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 feeding rate (%) of the powder during supersonic spraying was tested. The powder feeding rate is the percentage between the weight of the powder forming the coating on the substrate and the total weight of the powder during supersonic spraying. Each group of tests was measured five times and then the average value was taken. The test results are shown in Table 2.

[0102] Table 2

[0103]

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

[0105] As can be seen from the comparison between Comparative Examples 1-4 and Example 3, due to the change in the polyethylene glycol ratio, the morphology retention effect of the mixed powder is reduced, resulting in a significant decrease in its powder feeding rate.

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

[0107] Experiment 3: Electron micrograph

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

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

Claims

1. A preparation method of a composite tungsten carbide powder, characterized in that, Including: 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; 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: The powder block is ground by a dry grinder to obtain a composite tungsten carbide powder; The polyethylene glycol includes polymers with a molecular weight of 2000 - 20000; 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; The sintering operation in S300 includes: first heating to 180 - 220°C in 1.5 - 2.5 h, then heating to 380 - 420°C in 8 - 12 h, and then heating to 1100 - 1300°C in 6 - 10 h and holding for 1.5 - 2.5 h; The particle size of the mixed powder is 20 - 40 μm.

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

3. The preparation method of the 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.

4. The preparation method of the composite tungsten carbide powder according to any one of claims 1-3, characterized in that, In S400, the powder block is dry - ground, screened, and air - selected to obtain a composite tungsten carbide powder with a particle size of 15 - 45 μm; the over - size material during screening and the unqualified material during air - selection are recycled to S100 for ball milling.

5. The preparation method of the composite tungsten carbide powder according to claim 4, 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 during sintering in S300 is pumped to a recovery device by a vacuum pump.

6. A composite tungsten carbide powder prepared by the preparation method according to any one of claims 1 - 5.

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