CN111876643A - A kind of preparation method of high strength and toughness WC-Fe-Ni cemented carbide - Google Patents

Abstract

The invention belongs to the field of hard alloy preparation, and discloses a preparation method of high-toughness WC-Fe-Ni hard alloy. Preparing mixed powder, then ball-milling, drying, sieving, filling into a graphite die and prepressing for molding; putting the obtained sample communicated with a graphite mold into a vibration sintering furnace, wherein the atmosphere in the furnace is vacuum or inert atmosphere, firstly applying constant pressure of 30-50 MPa to the sample, simultaneously heating to the sintering temperature of 1300-1320 ℃, and when the sintering temperature is reached, switching the constant pressure into vibration pressure for vibration sintering, wherein the average value of the vibration pressure is 30-50 MPa, the vibration amplitude of the vibration pressure is 10-50 MPa, the vibration frequency is 1-10 Hz, and the vibration sintering is carried out for 0.25-1 h; after the vibration sintering is finished, the vibration pressure is switched to constant pressure again, the heating is stopped, the furnace is cooled, and when the temperature in the vibration sintering furnace is reduced to 600-1000 ℃, the vibration sintering furnace is removedKeeping the pressure constant, and continuously and naturally cooling to room temperature along with the furnace to prepare the high-strength and high-toughness WC-Fe-Ni hard alloy. The hardness of the high-toughness WC-Fe-Ni hard alloy prepared by the invention is larger than or equal to 1900 MPa, and the fracture toughness is larger than or equal to 12.01 MPa.m^1/2。

Description

A kind of preparation method of high strength and toughness WC-Fe-Ni cemented carbide

technical field

The invention belongs to the technical field of hard alloy preparation, in particular to a preparation method of a high-strength and tough WC-Fe-Ni hard alloy.

Background technique

WC-Fe-Ni cemented carbide has a wide range of raw materials, low cost, low environmental pollution, and high hardness, wear resistance and corrosion resistance. Therefore, WC-Fe-Ni cemented carbide has important application prospects in the fields of cutting tools, oil and mining drilling tools, precision molds and wear-resistant parts. However, for traditional WC-Fe-Ni cemented carbides, the hardness and toughness are contradictory, and if one of the properties is to be improved, the other must be sacrificed, which greatly limits the application of the cemented carbide.

In order to solve the contradiction between the hardness and toughness of cemented carbide, and to prepare high-strength and tough WC-Fe-Ni cemented carbide, researchers have carried out a lot of research and found that the preparation of gradient structure cemented carbide, twin-crystal structure cemented carbide, ultra-fine / Both nanocrystalline cemented carbide and coated structure cemented carbide can obtain materials with both high hardness and toughness to a certain extent. However, the above several methods have cumbersome preparation process, complicated operation process and high production cost; the other is to prepare coated cemented carbide, but its production process requirements are strict, the equipment investment is huge, and the production cost is high, which limits the high strength Large-scale industrial application of tough cemented carbide.

In view of the above situation, in order to further expand the application of WC-Fe-Ni cemented carbide, especially for high-end applications, it is urgent to develop a new preparation method for high-strength and tough WC-Fe-Ni cemented carbide, which not only has high It has high hardness and high fracture toughness, and is suitable for industrial production.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a preparation method of a high-strength and tough WC-Fe-Ni cemented carbide.

To achieve the above object, the technical scheme adopted by the present invention is as follows:

A preparation method of high-strength and tough WC-Fe-Ni cemented carbide:

(1) Using WC powder, Fe powder, and Ni powder as raw materials to prepare mixed powder, then ball-milled, dried, sieved, and put into a graphite mold for pre-compression molding;

(2) Put the sample obtained after the pre-press molding in step (1) into a vibration sintering furnace connected to the graphite mold. The atmosphere in the furnace is a vacuum or an inert atmosphere. First, a constant pressure of 30-50 MPa is applied to the sample, and at the same time, the temperature is raised to sintering. The temperature is 1300~1320℃. When the sintering temperature is reached, the constant pressure is switched to the vibration pressure for vibration sintering. The average value of the vibration pressure is 30~50 MPa, the vibration amplitude of the vibration pressure is 10~50 MPa, and the vibration frequency is 1~10 Hz. , Vibration sintering for 0.25~1 h;

(3) After the vibration sintering is over, switch the vibration pressure to a constant pressure again, stop the heating, and cool with the furnace. When the temperature in the vibration sintering furnace drops to 600~1000 °C, remove the constant pressure and continue to follow The furnace is naturally cooled to room temperature to obtain high-strength and tough WC-Fe-Ni cemented carbide.

Preferably, in step (1), the particle size of the WC powder is 1-1.5 μm, and the particle size of the Fe powder and Ni powder is 1-2 μm; in the mixed powder, the content of the WC powder is 70-99.5 wt %, and the Fe/ The mass ratio of Ni is 1~3.

Preferably, in step (1), the pressure of the pre-press forming is 5-20 MPa.

Preferably, in step (1), the ball milling speed is 120-150 rpm, the ball-milling time is 15-24 h, and stainless steel balls with a diameter of 6-12 mm are added during the ball-milling process, and the mass ratio of the balls is (3-5) : 1, add 200~350 mL of absolute ethanol per 1 kg of mixed powder as the ball milling medium.

Preferably, in step (1), the drying is vacuum drying, and the temperature of vacuum drying is 40-60 °C and the time is 2-8 h.

Preferably, in step (1), pass through a 60-100 mesh sieve.

Preferably, in step (2), the temperature is raised to the sintering temperature at a heating rate of 2-8 °C/min.

Compared with the prior art, the beneficial effects of the present invention are:

(1) Only vibration pressure is applied during the preparation and sintering of high-strength and tough WC-Fe-Ni cemented carbide. Compared with conventional high-strength and tough cemented carbide, no additional additional procedures are required, and the process is simple, which is conducive to large-scale production, while reducing high-strength Production cost of tough cemented carbide;

(2) The preparation method can significantly reduce the sintering temperature, shorten the sintering time, reduce the residual pores in the material, inhibit the growth of grains, and prepare a cemented carbide material with high strength and high toughness;

(3) The hardness of the prepared high-strength and tough WC-Fe-Ni cemented carbide is ≧ 1900 MPa, and the fracture toughness is ≧ 12.01 MPa.m ^1/2 . The comprehensive performance of the developed high-strength and tough cemented carbide is better than that of the traditional process.

Description of drawings

1 is an SEM image of the WC-Fe-Ni cemented carbide prepared in Example 1.

FIG. 2 is an SEM image of the WC-Fe-Ni cemented carbide prepared in Example 2. FIG.

3 is a SEM image of the WC-Fe-Ni cemented carbide prepared in Comparative Example 1.

4 is an SEM image of the WC-Fe-Ni cemented carbide prepared in Comparative Example 2.

Detailed ways

The present invention will be further described below with reference to specific embodiments. It should be understood that the following examples are only used to illustrate the present invention and not to limit the scope of the present invention.

The vibration sintering furnace in the following examples was purchased from the multi-field coupling experimental system of Chengdu Yifeide Material Technology Co., Ltd., and the model is OPS-2020.

Example 1

In this embodiment, a WC-Fe-Ni cemented carbide with a binder phase content of 10 wt.% is selected, and the steps are as follows:

(1) Using WC powder (particle size of 1 μm), Fe powder (particle size of 1 μm) and Ni powder (particle size of 1 μm) as raw materials, the content of WC powder is 90 wt%, and the mass of Fe/Ni is The ingredients with a ratio of 3 require the preparation of mixed powder. The weighed mixed powder is put into a planetary ball mill for ball milling. The ball milling speed is 120 rpm, and the ball milling time is 24 h. During the ball milling process, stainless steel balls with a diameter of 8 mm are added. The mass ratio of the material was 3:1, and 300 mL of absolute ethanol was added to each 1 kg of mixed powder as the ball milling medium;

(2) After ball milling and mixing, the slurry was put into a vacuum drying oven and dried at a temperature of 60 °C for 8 h. The dried mixed powder was sieved under an 80-mesh screen, and the sieved mixed powder was put into Pre-press molding in a graphite mold under a pressure of 5 MPa;

(3) Put the sample together with the graphite mold into the vibration sintering furnace. The atmosphere in the furnace is vacuum, and the vacuum degree is maintained at 1.0×10 ^-3 Pa. The heating rate rises to the sintering temperature of 1300 °C;

(4) When the sintering temperature is reached, the static constant pressure is immediately switched to the dynamic vibration pressure, where the median value of the vibration pressure is 40 MPa, the amplitude of the vibration pressure is 10 MPa, the vibration frequency is 5 Hz, and the vibration sintering time is 1 h. ;

(5) After the vibration sintering is over, switch the dynamic vibration pressure to the static constant pressure again, stop the heating, and cool with the furnace. When the temperature in the vibration sintering furnace drops to 600 °C, start to slowly remove the static constant pressure to The pressure is 0, and continue to cool naturally to room temperature with the furnace to obtain WC-Fe-Ni cemented carbide.

Figure 1 is the SEM image of the prepared WC-Fe-Ni cemented carbide. The grain size of WC is 0.60 μm measured from the image, there is no obvious void in the structure, and the density is close to 100%.

Example 2

The difference from Example 1 is that in step (4), the amplitude of the vibration pressure is 20 MPa, and the others are the same as in Example 1.

Figure 2 is the SEM image of the prepared WC-Fe-Ni cemented carbide. The grain size of WC is 0.58 μm measured from the image, there is no obvious void in the structure, and the density is close to 100%.

Comparative Example 1

The difference from Example 1 is that in step (4), the amplitude of the vibration pressure is 5 MPa, and the others are the same as in Example 1.

Figure 3 is the SEM image of the prepared WC-Fe-Ni cemented carbide. The grain size of WC is 0.61 μm measured from the image, there is no obvious void in the structure, and the density is close to 100%.

Comparative Example 2

In this example, WC-Fe-Ni cemented carbide with a binder phase content of 10 wt.% is selected. The steps are as follows:

(1) Using WC powder (particle size of 1 μm), Fe powder (particle size of 1 μm) and Ni powder (particle size of 1 μm) as raw materials, according to WC powder as 90 wt%, Fe/Ni mass ratio The mixed powder was prepared for the component requirements of 3. The weighed mixed powder was put into a planetary ball mill for ball milling. The ball milling speed was 120 rpm, and the ball milling time was 24 h. During the ball milling process, stainless steel balls with a diameter of 8 mm were added. The mass ratio of the material was 3:1, and 300 mL of absolute ethanol was added to each 1 kg of mixed powder as the ball milling medium;

(2) After ball milling and mixing, the slurry was put into a vacuum drying oven and dried at a temperature of 60 °C for 8 h. The dried mixed powder was sieved under an 80-mesh screen, and the sieved mixed powder was put into Pre-press molding in a graphite mold under a pressure of 5 MPa;

(3) Put the sample together with the graphite mold into the vibration sintering furnace, the atmosphere in the furnace is vacuum, the vacuum degree is maintained at 1.0 × 10 ^-3 Pa, and a static constant pressure of 40 MPa is applied to the sample, and at the same time, the temperature is 8 °C/min. The heating rate was increased to the sintering temperature of 1300 °C; when the sintering temperature was reached, the static constant pressure was maintained for 1 h;

(4) After the heat preservation is over, the heating stops and cools with the furnace. When the temperature in the vibrating sintering furnace drops to 600 °C, the static constant pressure is slowly removed until the pressure is 0, and the furnace continues to cool to room temperature naturally. , obtained WC-Fe-Ni cemented carbide.

Figure 4 is the SEM image of the prepared WC-Fe-Ni cemented carbide. The grain size of WC is 0.69 μm measured from the image, the structure is coarse, there is no obvious cavity, and the density is close to 100%.

The WC-Fe-Ni cemented carbides prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 were tested for hardness and fracture toughness. The properties of the examples and the comparative examples are obtained by testing in the same experimental method, and the mechanical properties of the examples and the comparative examples are shown in Table 1 below.

It can be seen from Table 1 that compared with traditional sintering (Comparative Example 2), when the amplitude of the vibration pressure is 5 MPa (Comparative Example 1), the hardness of the material is significantly improved, but the fracture toughness of the material is not significantly improved. When ≥10 MPa (Example 1 and Example 2), the hardness and fracture toughness of the material are significantly improved, and a cemented carbide with high strength and toughness can be prepared.

Claims (7)

1. A preparation method of high-strength and high-toughness WC-Fe-Ni hard alloy is characterized by comprising the following steps:

(1) preparing mixed powder by using WC powder, Fe powder and Ni powder as raw materials, then carrying out ball milling, drying and sieving after ball milling, and filling the ball-milled powder into a graphite die for prepressing molding;

(2) putting a sample obtained after the pre-pressing forming in the step (1) into a vibration sintering furnace, wherein the atmosphere in the furnace is vacuum or inert atmosphere, firstly applying constant pressure of 30-50 MPa to the sample, simultaneously heating to the sintering temperature of 1300-1320 ℃, and when the sintering temperature is reached, switching the constant pressure into vibration pressure for vibration sintering, wherein the average value of the vibration pressure is 30-50 MPa, the vibration amplitude of the vibration pressure is 10-50 MPa, the vibration frequency is 1-10 Hz, and the vibration sintering is carried out for 0.25-1 h;

(3) and after the vibration sintering is finished, switching the vibration pressure to constant pressure again, stopping heating, cooling along with the furnace, removing the constant pressure when the temperature in the vibration sintering furnace is reduced to 600-1000 ℃, and naturally cooling to room temperature along with the furnace continuously to prepare the high-strength and high-toughness WC-Fe-Ni hard alloy.

2. The method for preparing the high-toughness WC-Fe-Ni hard alloy as claimed in claim 1, wherein the method comprises the following steps: in the step (1), the grain diameter of WC powder is 1-1.5 μm, and the grain diameters of Fe powder and Ni powder are 1-2 μm; in the mixed powder, the content of WC powder is 70-99.5 wt%, and the mass ratio of Fe/Ni is 1-3.

3. The method for preparing the high-toughness WC-Fe-Ni hard alloy as claimed in claim 1, wherein the method comprises the following steps: in the step (1), the pressure of the pre-pressing forming is 5-20 MPa.

4. The method for preparing the high-toughness WC-Fe-Ni hard alloy as claimed in claim 1, wherein the method comprises the following steps: in the step (1), the ball milling speed is 120-150 rpm, the ball milling time is 15-24 hours, stainless steel balls with the diameter of 6-12 mm are added in the ball milling process, the mass ratio of ball materials is (3-5): 1, and 200-350 mL of absolute ethyl alcohol is added into every 1 kg of mixed powder as a ball milling medium.

5. The method for preparing the high-toughness WC-Fe-Ni hard alloy as claimed in claim 1, wherein the method comprises the following steps: in the step (1), the drying is vacuum drying, the temperature of the vacuum drying is 40-60 ℃, and the time is 2-8 hours.

6. The method for preparing the high-toughness WC-Fe-Ni hard alloy as claimed in claim 1, wherein the method comprises the following steps: in the step (1), sieving the mixture by a sieve of 60-100 meshes.

7. The method for preparing the high-toughness WC-Fe-Ni hard alloy as claimed in claim 1, wherein the method comprises the following steps: in the step (2), the temperature is increased to the sintering temperature at the temperature increase speed of 2-8 ℃/min.

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