A grain size gradient alloy and its preparation method

Abstract

This application relates to the technical field of cemented carbide production, and discloses a grain size gradient alloy and a preparation method thereof, including the following raw materials: tungsten carbide with a Fisher grain size of 0.5 - 30.0 μm, cobalt powder with a particle size of 1.0 - 5.0 μm, activator with a particle size of 1.0 - 10.0 μm, paraffin wax No. 56, and absolute ethanol. The preparation of the grain size gradient alloy includes the following method steps: Step 1, prepare a mixture with a cobalt content of 10% and an activator content of 0 - 5%, and the total carbon of the mixture is 5.3 - 5.8%; Step 2, put the above mixture into a ball mill cylinder and carry out wet grinding treatment, and the wet grinding time is 5 - 50 hours; Step 3, discharge the slurry, dry it and then carry out granulation treatment to make a mixture. By using an activator as a carrier and adding it to tungsten carbide and cobalt powder, a gradient alloy is prepared through wet grinding, drying, pressing, and sintering. When sintering, a biopharmaceutical gas is introduced, which reduces the sensitivity of tungsten carbide to temperature and delays the growth trend of the grain size of tungsten carbide. It can be adjusted according to process parameters, is easy to operate and control, and can realize industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of cemented carbide production, and specifically to a grain size gradient alloy and a preparation method thereof. Background Art

[0002] Cemented carbide is a composite material prepared by a traditional powder metallurgy method with high-hardness refractory metal carbide powder as the hard phase and metals such as CO and Ni as the bonding phase. Cemented carbide has the characteristics of strong comprehensive properties such as wear resistance, strength, and toughness, and is widely used in fields such as cutting tools, oil drilling and production, and wear-resistant parts. With the development of modern science and technology, end-users in the market have higher and higher requirements for the use cost and efficiency of cemented carbide. Traditional cemented carbide is difficult to meet the requirements of both high hardness and high toughness at the same time. In cemented carbide materials, hardness and toughness are a pair of contradictory entities. When increasing hardness, toughness needs to be reduced as a prerequisite. Therefore, many experts proposed a long time ago a gradient material that can increase both hardness and toughness. For gradient cemented carbide, more research has been done on composition gradient, that is, the bonding metals Co and Ni are distributed incrementally from the outside to the inside in the product.

[0003] At present, there are many patent reports on the preparation methods of gradient cemented carbide, including the carburizing method, the layered pressing forming method, and the melt infiltration method of Sandvik in Sweden and the University of Utah in the United States. The carburizing method mainly controls the different solubility of carbon inside the alloy, thereby forming different cobalt distributions. This process is complex, difficult to control, and not easy to form industrial production; the layered pressing method is easy to homogenize, difficult to form a gradient, and the alloy is easy to deform; the melt infiltration method requires immersing the alloy in the melt at high temperature, with high energy consumption and not easy to control the gradient. These current gradient alloy preparation methods are all complex in process, difficult to control, and not easy to form industrial production.

[0004] The present invention provides a simple, feasible, easy-to-control method for preparing gradient cemented carbide that can form industrial production, which is a major breakthrough in the performance of existing cemented carbide. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a grain size gradient alloy and a preparation method thereof, which solve the problems of high energy consumption, difficult gradient control, complex process, difficult to control, and not easy to form industrial production in the current gradient cemented carbide preparation methods.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A grain size gradient alloy, comprising the following raw materials:

[0007] Tungsten carbide with a Fisher grain size of 0.5 - 30.0 μm, cobalt powder with a particle size of 1.0 - 5.0 μm, activator with a particle size of 1.0 - 10.0 μm, paraffin wax No. 56, and absolute ethanol.

[0008] A preparation method of a grain size gradient alloy, which is used to prepare the above-mentioned grain size gradient alloy, includes the following method steps:

[0009] Step 1: Prepare a mixture with a cobalt content of 10% and an activator content of 0-5%, and the total carbon of the mixture is 5.3-5.8%;

[0010] Step 2: Put the above mixture into a ball mill, and perform wet grinding treatment with a ball-to-material ratio of 1-8:1 and a liquid-to-material ratio of 0.1-0.8 L / kg, and the wet grinding time is 5-50 hours;

[0011] Step 3: Discharge the slurry, dry it and then perform granulation treatment to make a mixture;

[0012] Step 4: Press the mixture into a square product and sinter it in a low-pressure vacuum sintering furnace. The dewaxing temperature is 300-500 °C and the holding time is 30-160 minutes;

[0013] Step 5: When the sintering temperature is 1100-1300 °C, introduce a biopharmaceutical gas with a flow rate of 2-20 L / min and a holding time of 30-210 minutes;

[0014] Step 6: The vacuum sintering temperature is 1300-1500 °C, the holding time is 30-150 minutes, and the pressure is 3-10 MPa;

[0015] Step 7: Cool to room temperature with the furnace;

[0016] Step 8: Detect the grain size distribution of the product.

[0017] Preferably, in the above Step 2, the ball is an alloy cylinder, and the liquid material refers to anhydrous alcohol.

[0018] Preferably, in the above Step 3, the particle size of the made mixture is 60-150 μm.

[0019] Preferably, in the above Step 4, argon is introduced during sintering with a flow rate of 8-18 L / min.

[0020] The present invention provides a grain size gradient alloy and a preparation method thereof. It has the following beneficial effects:

[0021] In the present invention, an activator is used as a carrier and added to tungsten carbide and cobalt powder. After wet grinding, drying, pressing, and sintering, a gradient alloy is prepared. During sintering, a biocidal agent gas is introduced. The combined action of the agent and the activator reduces the sensitivity of tungsten carbide to temperature and delays the growth trend of the grain size of tungsten carbide. Since the agent gas diffuses into the product from the surface to the inside, a hard alloy with a gradient distribution of tungsten carbide grain size is formed, where the grain size of tungsten carbide is fine on the outside and coarse in the middle. Different types of hard alloys with a gradient distribution of tungsten carbide grain size can be produced according to process parameters, enabling the product to have better performance advantages. By using this mechanism to prepare hard alloys with a grain size gradient, the process operation is simple and easy to control, and industrial production can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the finished product structure of the grain size gradient alloy prepared in Example 1 of the present invention;

[0023] Figure 2 Schematic diagram of the finished product structure of the grain size gradient alloy prepared in Example 2 of the present invention;

[0024] Figure 3 Schematic diagram of the finished product structure of the grain size gradient alloy prepared in Example 3 of the present invention;

[0025] Figure 4 Schematic diagram of the finished product structure of the grain size gradient alloy prepared in Example 4 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Example 1:

[0028] Experimental raw materials: Tungsten carbide: Fisher particle size is 15 μm, total carbon is 6.11%; cobalt powder, Fisher particle size 1.2 μm; chromium sesquioxide, Fisher particle size 2 μm; molding agent: paraffin wax No. 56; wet grinding medium: absolute alcohol; a mixture is prepared according to a cobalt content of 10%, a chromium sesquioxide content of 0.5%, and a total carbon of 5.5%.

[0029] Preparation steps:

[0030] Step 1: Select 895 g of tungsten carbide with a Fisher particle size of 15 μm and a total carbon of 6.11%, 100 g of cobalt powder with a Fisher particle size of 1.2 μm, and 5 g of chromium sesquioxide with a Fisher particle size of 2 μm.

[0031] Step 2: Put the above mixture into a 1-liter ball mill cylinder, add another 5000 g of alloy grinding rods, 0.4 liters of alcohol, and 22 g of paraffin, and wet grind for 30 hours.

[0032] Step 3: Discharge the above slurry, dry and granulate it to make a mixed material, with the particle size of 80 - 150 μm.

[0033] Step 4: Press the above mixed material into a square product, dewax and pre-sinter it in a low-pressure furnace, with the argon flow rate of 10 liters per minute, the dewaxing temperature of 350 °C, and keep it warm for 40 minutes.

[0034] Step 5: Sinter the product in vacuum. When the temperature rises to 1200 °C, introduce methane gas, with the gas flow rate of 5 liters per minute, and keep it warm for 30 minutes.

[0035] Step 6: Raise the temperature to 1430 °C, keep it warm for 40 minutes, and apply a pressure of 6 MPa.

[0036] Example 2: (Change in the gas flow rate of the reagent)

[0037] Experimental raw materials: Tungsten carbide: The Fisher particle size is 15 μm, and the total carbon content is 6.11%; Cobalt powder, the Fisher particle size is 1.2 μm; Chromium sesquioxide, the Fisher particle size is 2 μm; Molding agent: Paraffin No. 56; Wet grinding medium: Absolute alcohol; Prepare a mixed material according to the cobalt content of 10%, the chromium sesquioxide content of 0.5%, and the total carbon content of 5.5%.

[0038] Experimental steps

[0039] Step 1: Select 895 g of tungsten carbide with a Fisher particle size of 15 μm and a total carbon content of 6.11%, 100 g of cobalt powder with a Fisher particle size of 1.2 μm, and 5 g of chromium sesquioxide with a Fisher particle size of 2 μm.

[0040] Step 2: Put the above mixture into a 1-liter ball mill cylinder, add another 5000 g of alloy grinding rods, 0.4 liters of alcohol, and 22 g of paraffin, and wet grind for 30 hours.

[0041] Step 3: Discharge the above slurry, dry and granulate it to make a mixed material, with the particle size of 80 - 150 μm.

[0042] Step 4: Press the above mixed material into a square product, dewax and pre-sinter it in a low-pressure furnace, with the argon flow rate of 10 liters per minute, the dewaxing temperature of 350 °C, and keep it warm for 40 minutes.

[0043] Step 5: Sinter the product in vacuum. When the temperature rises to 1200 °C, introduce methane gas, with the gas flow rate of 10 liters per minute, and keep it warm for 30 minutes.

[0044] Step 6: Raise the temperature to 1430 °C, keep it warm for 40 minutes, and apply a pressure of 6 MPa.

[0045] Example 3: (Activator content changes)

[0046] Experimental raw materials: tungsten carbide: Fischer particle size is 15μm, total carbon is 6.11%; cobalt powder, Fischer particle size is 1.2μm; chromium trioxide, Fischer particle size is 2μm; molding agent: No. 56 paraffin wax; wet grinding medium: anhydrous alcohol; the mixture is prepared according to the cobalt content of 10%, the chromium trioxide content of 1%, and the total carbon of 5.5%.

[0047] Experimental steps:

[0048] Step 1: Select 890g tungsten carbide with a Fischer-Tropsch particle size of 15μm and a total carbon content of 6.11%, 100g cobalt powder with a Fischer-Tropsch particle size of 1.2μm, and 10g chromium trioxide with a Fischer-Tropsch particle size of 2μm.

[0049] Step 2: Place the above mixture into a 1-liter ball mill, add 5000 g of alloy grinding rod, 0.4 liter of alcohol, 22 g of paraffin wax, and wet grind for 30 hours.

[0050] Step 3: discharge the above slurry, dry and granulate it to make a mixture with particles of 80-150 μm.

[0051] Step 4: Press the above mixture into cube products, dewax and pre-sinter in a low-pressure furnace, with an argon flow rate of 10 liters per minute, a dewaxing temperature of 350°C, and keep warm for 40 minutes.

[0052] Step 5: The product is vacuum sintered. When the temperature reaches 1200°C, methane gas is introduced at a gas flow rate of 5 liters per minute and the temperature is kept for 30 minutes.

[0053] Step 6: Heat to 1430°C and keep warm for 40 minutes, then pressurize to 6 MPa.

[0054] Example 4: (Comparative experiment, without adding activator and biological agent)

[0055] Experimental raw material preparation: tungsten carbide: Fischer particle size is 15μm, total carbon is 6.11%; cobalt powder, Fischer particle size is 1.2μm; molding agent: No. 56 paraffin; wet grinding medium: anhydrous alcohol; the mixture is prepared according to the cobalt content of 10% and the total carbon of 5.5%.

[0056] Experimental steps:

[0057] Step 1: Select 900g of tungsten carbide with a Fischer-Tropsch particle size of 15μm and a total carbon content of 6.11%, and 100g of cobalt powder with a Fischer-Tropsch particle size of 1.2μm.

[0058] Step 2: Place the above mixture into a 1-liter ball mill, add 5000 g of alloy grinding rod, 0.4 liters of alcohol, 22 g of paraffin, and wet grind for 30 hours.

[0059] Step 3: Discharge the above-mentioned slurry, dry and granulate it to form a mixed material, with the particle size being 80 - 150 μm.

[0060] Step 4: Press the above-mentioned mixed material into a square product, dewax and pre-sinter it in a low-pressure furnace, with the argon flow rate being 10 liters per minute, the dewaxing temperature being 350 °C, and keep it warm for 40 minutes.

[0061] Step 5: Heat up to 1430 °C, keep it warm for 40 minutes, and apply a pressure of 6 MPa.

[0062] Table 1. Performance parameter table of the grain size gradient alloys prepared in Examples 1 to 4:

[0063]

[0064] From the content shown in the above Examples 1 to 4, for the grain size gradient alloy provided by the present invention and its preparation method, by using an activator as a carrier and adding it to tungsten carbide and cobalt powder, and through wet grinding, drying, pressing, and sintering to prepare a gradient alloy, the entire production process can be adjusted according to process parameters to produce cemented carbides with different types of tungsten carbide grain sizes distributed in a gradient manner, making the products have better performance advantages. At the same time, the present invention utilizes this mechanism to prepare grain size gradient cemented carbides, with simple process operations, easy to control, and can achieve industrial production.

[0065] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A grain size gradient alloy, characterized in that: Including the following ingredients: Tungsten carbide with a Fischer particle size of 0.5-30.0 μm, cobalt powder with a Fischer particle size of 1.0-5.0 μm, an activator with a Fischer particle size of 1.0-10.0 μm, No. 56 paraffin and anhydrous alcohol, wherein the activator is chromium trioxide; The grain size gradient alloy is made by the following method steps: Step 1: Prepare the raw materials into a mixture with a cobalt content of 10%, an activator content of 0.5-1%, and a total carbon content of 5.3-5.8%; Step 2: Place the mixture into a ball mill with a ball-to-material ratio of 1-8:1 and a liquid-to-material ratio of 0.1-0.8 L / kg for wet grinding for 5-50 hours; Step 3, unloading the slurry, drying it, and then granulating it to make a mixed material; Step 4: Press the mixture into cube products and sinter them in a low-pressure vacuum sintering furnace. The dewaxing temperature is 300-500°C and the insulation time is 30-160 minutes. Step 5: When the sintering temperature is 1100-1300° C., a biopharmaceutical gas is introduced, wherein the biopharmaceutical gas is methane gas, with a flow rate of 2-20 liters / minute and a holding time of 30-210 minutes; Step 6: vacuum sintering temperature is 1300-1500°C, holding time is 30-150 minutes, and pressure is 3-10MPa; Step 7: Cooling to room temperature with the furnace; Step 8: Detect the grain size distribution of the product.

2. A grain size gradient alloy according to claim 1, characterized in that: In the step 2, the ball material is an alloy cylinder, and the liquid material refers to anhydrous alcohol.

3. A grain size gradient alloy according to claim 1, characterized in that: In the step 3, the particle size of the prepared mixture is 60-150 μm.

4. The grain size gradient alloy according to claim 1, characterized in that: In the step 4, argon gas is introduced during sintering at a flow rate of 8-18 liters / minute.

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