Preparation method of high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance

Abstract

The present invention relates to a preparation method of a high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance. The preparation method includes the following steps: S1: preparing high-entropy alloy powder of a single solid solution; S2: mixing and ball-milling 64-70% of titanium carbide powder, 1-6% of niobium carbide powder, 20-24% of iron powder, and 6-10% of high-entropy alloy powder by weight percentage, and then drying and sieving to obtain mixed powder. Among them, the ball-milling molding agent is paraffin, and the ball-milling medium is absolute ethanol; S3: pressing the mixed powder into a shape and then performing sintering treatment. The high-entropy steel-bonded cemented carbide stud obtained through a special sintering process not only has excellent wear resistance and high-temperature performance, but also has good forgeability and weldability.

Description

Technical Field

[0001] The present invention relates to the field of alloy studs, and particularly to a preparation method of a high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance. Background Art

[0002] At present, cemented carbide studs have developed rapidly in fields such as the cement industry, metallurgy, mines, etc. With their rapid development, some problems of cemented carbide studs have also emerged. For example, the existence of problems such as low hardness and poor wear resistance will cause serious wear of the studs during use, reducing their service life. In response to the above problems of the studs, researchers mainly focus on exploring new materials to solve them. The materials used more are cobalt-based alloys. Although such alloys can improve the above defects, they have defects such as high toxicity and poor high-temperature performance. Moreover, when applying the studs to a stud roll, that is, during the manufacturing process of the stud roll, there is a gap between the studs to build a wear-resistant layer on the roll surface to improve the overall wear resistance of the stud roll. However, the weldability between the studs made of cobalt-based alloys and the wear-resistant materials of the wear-resistant layer is poor, resulting in insufficient bonding strength between the studs and the wear-resistant layer, which will further affect the wear resistance of the entire stud roll. Summary of the Invention

[0003] In order to make up for the deficiencies of the prior art, the present invention provides a preparation method of a high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance. The alloy stud prepared by this method not only has good wear resistance and high-temperature hardness, but also has good forgeability and weldability.

[0004] The technical solution adopted by the present invention to solve the above technical problems is:

[0005] A preparation method of a high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance, comprising the following steps:

[0006] S1: Prepare a high-entropy alloy powder of a single solid solution, wherein the elements of the high-entropy alloy powder include aluminum, cobalt, chromium, iron, and nickel;

[0007] S2: According to the weight percentage, mix and ball-mill 64-70% of titanium carbide powder, 1-6% of niobium carbide powder, 20-24% of iron powder, and 6-10% of high-entropy alloy powder, and then dry and screen to obtain a mixed powder. Among them, the ball-milling forming agent is paraffin, and the ball-milling medium is absolute ethanol;

[0008] S3: After compacting the mixed powder into a shape, perform sintering treatment. The sintering process is as follows: First, heat it from room temperature to 296 - 310 °C at a rate of 4.8 - 5.2 °C / min, hold for 5 h, then continue to heat it to 480 - 485 °C at a rate of 0.5 - 0.65 °C / min, hold for 4 h, and then heat it to 820 - 825 °C at a rate of 2.5 - 3 °C / min, hold for 2 h. The hydrogen gas inlet rate is 63 - 66 L / min; Subsequently, in a vacuum atmosphere of <10 MPa, heat it to 1175 - 1185 °C at a heating rate of 1.45 - 1.5 °C / min, hold for 0.5 h, and then continue to heat it to 1364 - 1368 °C at a heating rate of 1.51 - 1.55 °C / min, hold for 0.5 h; Then continue to heat it to 1478 - 1480 °C at a heating rate of 0.94 - 0.96 °C / min, hold for 2 h, and then cool it to room temperature in the furnace to obtain the product.

[0009] 2. The preparation method of the high-entropy steel-bonded hard alloy stud with excellent high-temperature performance and wear resistance according to claim 1, characterized in that in S2, calculated by weight percentage, the raw material components are 67% titanium carbide powder, 3% niobium carbide powder, 22.5% iron powder, and 7.5% high-entropy alloy powder.

[0010] Preferably, in S3, the sintering process is as follows:

[0011] Preferably, in S2, during the ball milling process, the ball-to-material ratio is 10:1, the balls are tungsten carbide balls with a diameter of 6.5 mm, the ball milling speed is 80 r / min, and the ball milling time is 24 h.

[0012] Preferably, in S2, the drying temperature after ball milling is 100 °C, the drying time is 1.5 - 2 h, and a 100-mesh sieve is selected for sieving.

[0013] Preferably, for the titanium carbide and niobium carbide powders: the purity ≥ 99%, and the average particle size is 2 - 5 μm; for the iron powder: the purity ≥ 99.5%, and the particle size is -220 mesh; for the high-entropy alloy powder: the purity ≥ 99%, and the average particle size is 28 μm.

[0014] Preferably, in S1, the preparation method of the high-entropy alloy powder is as follows: Weigh the metal raw materials of aluminum, cobalt, chromium, iron, and nickel according to an equiatomic ratio or a ratio close to equiatomic ratio, then put them into an induction furnace to melt into a liquid. The liquid flows out through the leak hole at the bottom of the atomizing nozzle and meets a high-speed gas stream to be atomized into fine droplets. The atomized droplets quickly solidify into alloy powder in a closed atomizing cylinder.

[0015] Preferably, in the high-entropy alloy powder, the purity of aluminum, cobalt, chromium, iron, and nickel is not less than 99%.

[0016] Preferably, in S3, a hydraulic press is used for pressing, and the pressure is 250 Mpa.

[0017] The present invention adopts the above structure and has the following advantages:

[0018] The high-entropy rigid cemented carbide stud produced by the present invention, which is composed of titanium carbide, niobium carbide, iron, and high-entropy alloy as raw materials and prepared by a specific ratio and sintering process, has excellent wear resistance and high-temperature performance. Among them, the high-temperature hardness, friction coefficient, and wear rate of the stud reach 1128 HV, 0.37, and 3.15×10 -6 mm / N·m respectively. Most of the components in the raw materials of this application are titanium carbide. Titanium is cheaper than tungsten in carbide series materials, and the powder ranked second in terms of raw material quantity is even cheaper. Therefore, compared with the existing tungsten-cobalt alloy, the raw material cost of this application is not high.

[0019] The high-entropy rigid cemented carbide stud produced by the present invention also has good forgeability and weldability, so that when it is applied to the stud roll, it has a strong bonding force with the surfacing wear-resistant layer, which helps to improve the wear resistance of the entire stud roll.

[0020] In summary, the high-entropy rigid cemented carbide stud produced by the present invention has a long service life and a wide application range, and has important guiding significance and application value in the development of studs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the micrograph of the high-entropy alloy powder in Example 1 of the present invention;

[0022] Figure 2 is the XRD pattern of the high-entropy alloy powder in Example 1 of the present invention;

[0023] Figure 3 is the micrograph of the mixed powder after ball milling in Example 1 of the present invention;

[0024] Figure 4 is the XRD pattern of the mixed powder after ball milling in Example 1 of the present invention;

[0025] Figure 5 is the micrograph of the wear morphology of the test sample in Example 1 of the present invention;

[0026] Figure 6 is a partial structural schematic diagram when the stud is applied to the stud roll. DETAILED DESCRIPTION OF THE INVENTION

[0027] To clearly illustrate the technical features of this solution, the present invention will be described in detail below through specific embodiments and in conjunction with its accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0028] Raw material selection: Titanium carbide and niobium carbide powders: purity ≥ 99%, average particle size 2 - 5 μm; iron powder: purity ≥ 99.5%, particle size -220 mesh; high-entropy alloy powder: purity ≥ 99%, average particle size 28 μm; in the high-entropy alloy powder, the purity of aluminum, cobalt, chromium, iron, and nickel is not less than 99%.

[0029] Example 1

[0030] A preparation method of a high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance, comprising the following steps:

[0031] S1: Prepare a high-entropy alloy powder of a single solid solution. Specifically, weigh metal raw materials of aluminum, cobalt, chromium, iron, and nickel according to an equiatomic ratio or close to an equiatomic ratio, then put them into an induction furnace to melt into a liquid. The liquid flows out through the leak hole at the bottom of the atomizing nozzle, meets a high-speed air flow and is atomized into fine droplets. The atomized droplets quickly solidify into alloy powder in a closed atomizing cylinder. The prepared high-entropy alloy powder has a purity greater than 99% and an average particle size of 28 μm. The microstructure of the alloy powder after atomization is shown in Figure 1 , and the XRD diffraction analysis results are shown in Figure 2 .

[0032] S2: According to the weight percentage, mix 67% of titanium carbide powder, 3% of niobium carbide powder, 22.5% of iron powder, and 7.5% of high-entropy alloy powder for ball milling treatment, and then dry and screen to obtain a mixed powder. Among them, the ball milling molding agent is paraffin, the ball milling medium is anhydrous ethanol, the ball-to-material ratio is 10:1, the balls are tungsten carbide balls with a diameter of 6.5 mm, the ball milling speed is 80 r / min, the ball milling time is 24 h, the drying temperature after ball milling is 100 °C, the drying time is 1.5 - 2 h, and a 100-mesh sieve is selected for screening. The microstructure of the obtained mixed powder is shown in Figure 3 , and the XRD diffraction analysis results are shown in Figure 4 .

[0033] S3: Press the mixed powder into a shape under a pressure of 250 Mpa with a hydraulic press, and then conduct sintering treatment. The sintering process is as follows: First, heat it to 300 °C at a rate of 5 °C / min and hold for 5 h. Then continue to heat it to 480 °C at a rate of 0.6 °C / min and hold for 4 h. Next, heat it to 820 °C at a rate of 2.8 °C / min and hold for 2 h. During the above process, hydrogen is introduced to remove wax, which can be completely removed, and the hydrogen introduction rate is 65 L / min. Subsequently, in a vacuum atmosphere of <10 MPa, heat it to 1180 °C at a heating rate of 1.5 °C / min and hold for 0.5 h. Then continue to heat it to 1365 °C at a heating rate of 1.54 °C / min and hold for 0.5 h. This process is the solid-phase sintering stage. Continue to heat it to 1480 °C at a heating rate of 0.96 °C / min and hold for 2 h. This process is the liquid-phase sintering stage. Finally, cool it to room temperature with the furnace, and it is obtained.

[0034] The high-entropy steel-bonded cemented carbide stud involved below is named HCR stud, and the high-entropy alloy powder obtained in S1 is abbreviated as HEA for convenience of description.

[0035] Visually, the surface of the prepared HCR stud has no cracks, indicating its good forgeability.

[0036] Taking the stud with the following dimensions (height 40 mm, spherical top SR8, bottom fillet R5) as an example, the performance of the HCR stud (experimental sample) prepared in this embodiment is tested, and the stud prepared by the existing sintering process is used as Comparative Sample 1 to test its performance. The existing sintering process is as follows: Heat the temperature to 290 °C and hold for 7.5 h. Then continue to heat it to 330 °C and hold for 1.5 h. Heat it to 400 °C and hold for 2.5 h. Then heat it to 480 °C and hold for 5 h, and conduct a 1-h hydrogen removal treatment; Heat it to 1330 °C for vacuum sintering and hold for 3 h. Finally, heat it to 1420 °C and hold for 1.5 h.

[0037] The test method is as follows: Polish the stud specimen to a mirror surface and measure it with a high-temperature Vickers hardness test system (model ZD-HVZHT-30). During the hardness test, the load is 1 Kg and the pressure holding time is 10 s. The high-temperature hardness is measured after holding at 800 °C for 10 minutes. To reduce experimental errors and ensure accuracy, 8 experimental tests are conducted for each sample, and the results are averaged. Use a reciprocating friction and wear testing machine to test the wear resistance of the stud; the counter-sample for abrasion is Si3N4 ball, the applied load is 70 N, the sliding frequency is 5 Hz / s, the stroke length is 6 mm, and the test time for each sample is 30 min. Observe the microstructure and wear morphology through a scanning electron microscope, and use a three-dimensional optical surface profiler (model Contour-GT-K1) to measure the three-dimensional morphology and wear volume (V) of the wear marks on the specimen; the wear rate (W) calculation formula is: Where W is the wear rate, V is the wear volume, and F p is the applied load, and L is the sliding distance. The flexural strength is measured by a three-point bending test using a universal testing machine (model AGS-X5KN), with a span of 15 mm. The samples are obtained by wire cutting and have dimensions of 20 mm * 5 mm * 2 mm. The formula for calculating the fracture toughness (KIC) of the specimen is as follows: Where HV30 is the Vickers hardness at a load of 30 kg (N / mm2), and li is the crack length starting from the corners of the indentation (mm). The test results are shown in Table 1, and the wear morphology of the HCR stud in Example 1 is shown in Figure 5 .

[0038] Table 1 Experimental data of the studs prepared in Example 1 and Comparative Example 1

[0039]

[0040] From the results in Table 1, it can be seen that the HCR stud prepared in Example 1 has excellent room temperature and high temperature properties. In particular, its room temperature hardness can reach 1811 HV, and its high temperature hardness at 800 °C can reach 1128 HV. One of the reasons for the excellent high temperature hardness of the HCR stud is the addition of HEA in combination with other components. There are two reasons for HEA to affect the high temperature hardness: First, the effect of temperature on the hardness of cemented carbide is generally related to its own dislocation slip. The stacking fault energy of HEA in the HCR stud is relatively low, which is relatively easy to form twins and relatively difficult to slip. However, there is an active slip system in the stressed area, and the stacking fault energy of dislocations in the slip system is relatively high. The HEA binder will hinder its slip movement. Second, the HEA grains are irregular and have wrinkles, which will hinder the slip when the HCR stud is stressed. Moreover, HEA has high temperature softening resistance, and the addition of HEA will improve the overall high temperature softening resistance of the new HCR stud.

[0041] The HCR stud prepared in Example 1 also has excellent wear resistance, and the wear rate at room temperature reaches 3.15×10 - 6 mm / N·m. The wear resistance of the HCR stud is related to its hardness and grain size. The HCR stud has high hardness, and high hardness can effectively support the grains, thereby reducing the breakage and shedding of the grains, and thus improving the wear resistance. Moreover, the HCR stud has fine grains, and fine grains have excellent microcrack resistance, which can increase the interfacial bonding strength between the hard phase and the binder phase and reduce the shedding of the grains. Therefore, the new HCR stud has excellent wear resistance.

[0042] From the performance results of Example 1 and Comparative Sample 1, it can be seen that compared with the HCR stud prepared by the existing process, Example 1 has great advantages in terms of performance such as room temperature hardness, high temperature hardness, fracture toughness, flexural strength, friction coefficient, wear rate, etc.

[0043] Examples 2 - 8

[0044] The HCR studs of Examples 2 - 8 were prepared by adjusting the component ratios according to the preparation method of Example 1, where Examples 6 - 8 were comparative experiments outside the ratio range of this application. Some properties of Examples 2 - 8 were tested by the testing method of Example 1, and the test results are shown in Table 2.

[0045] Table 2 Experimental data of the studs prepared in Examples 2 - 8

[0046]

[0047] From Examples 2 - 8 in Table 2, it can be seen that the studs obtained by the sintering process of this application within a certain ratio range of this application have great advantages in terms of room temperature hardness, high temperature hardness, fracture toughness, flexural strength, friction coefficient, wear rate, etc. For the HCR studs obtained by the sintering process of this application outside the ratio range of this application, the properties such as room temperature hardness, high temperature hardness, and wear rate have all decreased significantly. Specifically, by comparing Example 2 and Example 7, it can be seen that replacing niobium carbide with titanium carbide and adding it to the raw materials will reduce some properties of the stud, especially properties such as high temperature hardness, fracture toughness, flexural strength, wear rate, etc. From Examples 5 and 8, it can be seen that adding too much niobium carbide to replace part of titanium carbide in the raw materials will also reduce some properties of the stud, especially properties such as high temperature hardness, flexural strength, wear rate, etc. Thus, it can be seen that niobium carbide is not the more the better in the raw materials. In summary, based on the ratio range of this application, the studs prepared by the method of this application have great advantages in various properties.

[0048] The studs prepared by this application also have good weldability. As Figure 6 shown, when the stud 1 is applied to the stud roller, it can be well welded with the surfacing wear-resistant layer 2, and there is a strong bonding force between the two, which helps to improve the wear resistance of the entire stud roller.

[0049] The above specific implementation manners cannot be used as a limitation to the protection scope of the present invention. For those skilled in the art of this technology, any alternative improvement or transformation made to the implementation manners of the present invention falls within the protection scope of the present invention. Where the present invention is not described in detail, it is all well-known technology in this technical field.

Claims

1. A preparation method of a high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance, characterized in that, It includes the following steps: S1: Prepare high-entropy alloy powder of a single solid solution, where the elements of the high-entropy alloy powder include aluminum, cobalt, chromium, iron, and nickel; S2: By weight percentage, mix and ball-mill 64 - 70% titanium carbide powder, 1 - 6% niobium carbide powder, 20 - 24% iron powder, and 6 - 10% high-entropy alloy powder, and then dry and screen to obtain mixed powder. Among them, the ball-milling forming agent is paraffin, and the ball-milling medium is absolute ethanol; S3: After pressing the mixed powder into shape, perform sintering treatment. The sintering process is as follows: First, heat it at a rate of 4.8 - 5.2 °C / min to 296 - 310 °C, hold for 5 h, continue to heat at a rate of 0.5 - 0.65 °C / min to 480 - 485 °C, hold for 4 h, then heat at a rate of 2.5 - 3 °C / min to 820 - 825 °C, hold for 2 h, and the hydrogen inlet rate is 63 - 66 L / min; Subsequently, in a vacuum atmosphere under the condition of a pressure less than 10 MPa, heat it at a rate of 1.45 - 1.5 °C / min to 1175 - 1185 °C, hold for 0.5 h, and continue to heat at a rate of 1.51 - 1.55 °C / min to 1364 - 1368 °C, hold for 0.5 h; Then continue to heat at a rate of 0.94 - 0.96 °C / min to 1478 - 1480 °C, hold for 2 h, and cool it to room temperature in the furnace to obtain the product.

2. The preparation method of the high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance according to claim 1, characterized in that, In S2, by weight percentage, the raw material components are 67% titanium carbide powder, 3% niobium carbide powder, 22.5% iron powder, and 7.5% high-entropy alloy powder.

3. The preparation method of the high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance according to claim 1, characterized in that, In S3, the sintering process is as follows: First, heat it at a rate of 5 °C / min to 300 °C, hold for 5 h, continue to heat at a rate of 0.6 °C / min to 480 °C, hold for 4 h, then heat at a rate of 2.8 °C / min to 820 °C, hold for 2 h, and the hydrogen inlet rate is 65 L / min; Subsequently, heat it at a rate of 1.5 °C / min to 1180 °C, hold for 0.5 h, and continue to heat at a rate of 1.54 °C / min to 1365 °C, hold for 0.5 h; Continue to heat at a rate of 0.96 °C / min to 1480 °C, hold for 2 h, and cool it to room temperature in the furnace to obtain the product.

4. The preparation method of the high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance according to claim 1, characterized in that, In S2, during the ball-milling treatment, the ball-to-material ratio is 10:1, the balls are tungsten carbide balls with a diameter of 6.5 mm, the ball-milling speed is 80 r / min, and the ball-milling time is 24 h.

5. The preparation method of the high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance according to claim 1, characterized in that, In S2, the drying temperature after ball-milling treatment is 100 °C, the drying time is 1.5 - 2 h, and a 100-mesh sieve is selected for screening.

6. The preparation method of the high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance according to claim 1, characterized in that, Titanium carbide and niobium carbide powders: purity ≥ 99%, average particle size is 2 - 5 μm; iron powder: purity ≥ 99.5%, particle size - 220 mesh; high-entropy alloy powder: purity ≥ 99%, average particle size is 28 μm.

7. The preparation method of the high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance according to claim 1, characterized in that, In S1, the preparation method of the high-entropy alloy powder is as follows: Weigh the metal raw materials of aluminum, cobalt, chromium, iron, and nickel according to an equal atomic ratio or a ratio close to an equal atomic ratio, then put them into an induction furnace to melt into a liquid. The liquid flows out through the leak hole at the bottom of the atomizing nozzle and meets a high-speed gas stream to be atomized into fine droplets. The atomized droplets quickly solidify into alloy powder in a closed atomizing cylinder.

8. The preparation method of the high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance according to claim 1 or 6, characterized in that, In the high-entropy alloy powder, the purities of aluminum, cobalt, chromium, iron, and nickel are all not less than 99%.

9. The preparation method of the high-entropy steel-bonded cemented carbide stud with excellent high-temperature performance and wear resistance according to claim 1, characterized in that, In S3, a hydraulic press is used for pressing, and the pressure is 250 Mpa.

Images