WC grain hard alloy generating Ni3Al in situ and its preparation method

Abstract

The present application relates to the technical field of hard alloy, aiming at the problems of the prepared Ni3Al adhesive phase WC-based hard alloy, such as the pores in the sintering process, and further causing the low strength and poor corrosion resistance of the alloy, a WC grain hard alloy for in-situ generation of Ni3Al is provided, which comprises 0.01-0.1% boron, 0.5-5% aluminum nitride, 5-20% cobalt, 5-20% nickel, 0.5-3% chromium carbide, and the balance is tungsten carbide in terms of mass fraction. The present application can spheroidize WC grains through the synergistic effect of boron and aluminum nitride, that is, spherical WC grains are formed, which can reduce the stress concentration caused by the sharp prism angle of the grains, thereby ensuring the high-temperature oxidation resistance, corrosion resistance and wear resistance of the alloy material, and can also have high high-temperature fatigue failure resistance.

Description

Technical Field

[0001] This invention relates to the field of cemented carbide technology, and more specifically, to a WC grain cemented carbide with in-situ Ni3Al formation and its preparation method. Background Technology

[0002] WC-Co-Ni based cemented carbide is characterized by high strength, high hardness, and corrosion resistance, and is widely used in the manufacture of cutting tools, roller rings, and seals. However, during the production of WC-Co-Ni based cemented carbide, when the operating temperature rises, the high-temperature stress causes deformation of the binder phase in the alloy material. Once the hard phase loses the support of the binder phase, it is easily detached, causing damage to the WC-Co-Ni based cemented carbide. This directly affects product quality and leads to reduced production efficiency and increased production costs.

[0003] To address the aforementioned issues, a common approach is to use high-temperature resistant material components to strengthen the binder phase, thereby achieving better high-temperature resistance. Materials with extensive research include γ'-phase Ni3Al. Ni3Al intermetallic compounds exhibit a positive temperature effect, meaning their yield strength increases significantly with rising temperature. Furthermore, Ni3Al intermetallic compounds possess excellent oxidation and corrosion resistance.

[0004] Currently, vacuum hot pressing sintering is the main method for preparing Ni3Al-reinforced binder phase WC-based cemented carbides. For example, patent CN106498257A provides a method for in-situ generation of cemented carbides containing a Ni3Al binder phase. This involves first preparing a composite binder phase of Ni(OH)2 coated with AlN and a composite hard phase of Ni(OH)2 coated with WC, then mixing them and subjecting them to ball milling, filtration, and drying before pressing and sintering. Specifically, Ni(OH)2 is converted to Ni in a low-temperature Ar / H2 atmosphere, and vacuum sintering at high temperature causes Ni to react with AlN to form Ni3Al. However, while this method avoids the formation of intermetallic compounds such as W-Al in the early stages of sintering, which could degrade alloy properties, it requires separate processing of raw materials. The process is complex and difficult to control, with a long, challenging, and costly production flow, making it difficult to promote and apply in actual industrial production.

[0005] For example, patent CN102383021A also provides a WC-Co cemented carbide with a Ni3Al-reinforced binder phase and its preparation method. It uses Ni and Al powders as raw materials, utilizing the exothermic nature of the Ni-Al combination reaction. After melting Ni, Al, and their intermetallic compounds, Ni3Al and NiAl are rapidly generated, and NiAl further reacts with Ni to form Ni3Al. This method uses readily available raw materials and has a simple process. However, during the Al-Ni mixing reaction, diffusion imbalance is prone to occur, resulting in sintering porosity, which reduces the strength of the WC-based cemented carbide and also affects its corrosion resistance. Summary of the Invention

[0006] The technical problem to be solved by this invention:

[0007] Existing methods for preparing Ni3Al binder phase WC-based cemented carbides often result in porosity and other issues during sintering due to limitations in the preparation process and raw material properties in actual industrial production. This leads to problems such as low alloy strength and poor corrosion resistance.

[0008] The technical solution adopted in this invention is as follows:

[0009] This invention provides an in-situ Ni3Al-generated WC grain cemented carbide, comprising, by mass fraction, 0.01-0.1% boron, 0.5-5% aluminum nitride, 5-20% cobalt, 5-20% nickel, 0.5-3% chromium carbide, with the balance being tungsten carbide.

[0010] Preferably, the grain size of tungsten carbide is 5-15 μm.

[0011] Preferably, the total mass of cobalt and nickel accounts for 10-40 wt% of the total mass of the alloy.

[0012] The above-mentioned method for preparing in-situ Ni3Al-generated WC grain cemented carbide includes the following steps:

[0013] S1 Weigh the raw materials according to the specified amount, mix and wet grind, dry, sieve, and press into a compact;

[0014] S2 places the compact into a vacuum sintering furnace, heats it, and performs dewaxing sintering to obtain WC grain cemented carbide with in-situ Ni3Al formation.

[0015] Preferably, in step S1, during wet milling, the ball mill speed is controlled at 60-80 r / min and the ball milling time is 20-40 h.

[0016] Preferably, the ball-to-material ratio is controlled to be 2-5:1.

[0017] Preferably, in step S2, the dewaxing and sintering process is as follows: first heat to 380-420℃ and hold for a period of time, then continue to heat to 1400-1500℃ for sintering.

[0018] Preferably, the heat preservation time is 20-40 minutes and the sintering time is 1-4 hours.

[0019] Preferably, after the heat preservation is completed, the mixture is transferred to a vacuum environment, then argon gas is introduced, and then sintering is carried out.

[0020] Preferably, when argon gas is introduced, the ambient pressure is controlled at 1-5 MPa.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention provides an in-situ generated Ni3Al WC grain cemented carbide and its preparation method, which can be used in applications requiring high ambient temperatures or high wear resistance and high-temperature strength. Specifically, boron and aluminum nitride are used as alloying raw materials because: this invention has found that when boron and Al in aluminum nitride combine, their synergistic effect can spheroidize the WC grains, forming spherical WC grains. This reduces stress concentration caused by the sharp prismatic angles of the grains, thereby ensuring the high-temperature oxidation resistance, corrosion resistance, and wear resistance of the alloy material, while also maintaining high high-temperature fatigue failure resistance.

[0023] In detail, boron and aluminum nitride are generated in situ, causing the γ'-phase Ni3Al to be dispersed in the Co-Ni binder phase. This effectively avoids the porosity caused by Al during sintering, resulting in a uniform binder phase distribution, high alloy densification, good corrosion resistance, and excellent high-temperature oxidation and fatigue resistance. Furthermore, by controlling the relative content of Al and B during the preparation process, Al and B form intermetallic compounds. This process improves the morphology of WC grains, making them more spherical. This reduces stress concentration caused by the angle between the triangular prism faces of the grains, lowers the driving force for crack propagation, and provides resistance to fatigue failure at high temperatures. Attached Figure Description

[0024] Figure 1 This is a metallographic structure diagram of the in-situ generated Ni3Al WC grain hard alloy in Example 1;

[0025] Figure 2 The metallographic structure diagram of the WC-Co-Ni cemented carbide in Comparative Example 1 is shown.

[0026] Figure 3 The image shows the HAADF-STEM microstructure of the selected area of ​​WC grain cemented carbide in Example 1.

[0027] Figure 4The image shows the HAADF-STEM microstructure of the selected area of ​​the WC-Co-Ni cemented carbide in Comparative Example 1. Detailed Implementation

[0028] 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 below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0029] This invention provides an in-situ Ni3Al-generated WC grain cemented carbide, comprising, by mass fraction, 0.01-0.1% boron, 0.5-5% aluminum nitride, 5-20% cobalt, 5-20% nickel, 0.5-3% chromium carbide, with the balance being WC;

[0030] The tungsten carbide has a grain size range of 5-15 μm, preferably 8-12 μm; the total mass of cobalt and nickel accounts for 10-40% of the total mass of the alloy.

[0031] The present invention also provides a method for preparing the above-mentioned in-situ Ni3Al-generated WC grain cemented carbide, comprising the following steps:

[0032] (1) Batching and pressing:

[0033] According to the proportion of each raw material component, mix and wet grind to obtain a uniform premix. After drying and sieving through a 30-50 mesh sieve, the premix is ​​pressed into a compact with a pressing pressure of 5-10 MPa and a holding pressure of 8-12 seconds.

[0034] The wet grinding medium is hexane, the ball milling speed is 60-80 r / min, the grinding media is Φ5-8mm alloy rod, the ball-to-material ratio is 2-5:1, and the ball milling time is 20-40 h.

[0035] (2) Dewaxing and sintering:

[0036] The compact is placed in a sintering furnace under a vacuum environment of 1-5MPa and dewaxed for sintering to obtain a high-temperature resistant spherical WC grain cemented carbide with in-situ Ni3Al formation.

[0037] The dewaxing and sintering process is as follows: first, hold at 380-420℃ for 20-40 minutes, then place in a vacuum environment, heat to 1400-1500℃, fill with argon gas to an ambient pressure of 1-5MPa, and sinter for 1-4 hours.

[0038] <Example>

[0039] Example 1

[0040] Weigh out 0.05% boron, 2.5% aluminum nitride, 10% cobalt, 10% nickel, 2% chromium carbide, and 75.45% tungsten carbide with a grain size of 12 μm, respectively, by mass fraction.

[0041] Mix the above raw materials, add ethane to the solids in the grinding container, put in a Φ6.35mm alloy rod as the grinding media, control the ball-to-material ratio to be 3.5:1, adjust the ball mill speed to 70r / min, and wet grind for 30min;

[0042] The refined premix obtained after wet milling is dried to completely remove moisture, passed through a 40-mesh sieve, and then pressed into a compact by holding the pressure at 8MPa for 10s.

[0043] The compact was placed in a vacuum sintering furnace at 3 MPa and heated to about 400°C for 30 minutes. Then, the compact was placed in a vacuum environment and argon gas was introduced until the ambient pressure was 3 MPa. The temperature was then increased to about 1450°C and sintered at 1400-1500°C for 2.5 hours.

[0044] Example 2

[0045] Weigh out 0.05% boron, 2.5% aluminum nitride, 10% cobalt, 10% nickel, 2% chromium carbide, and 75.45% tungsten carbide with a grain size of 12 μm, respectively, by mass fraction.

[0046] Mix the above raw materials, add ethane to the solids in the grinding container, put in a Φ6.35mm alloy rod as the grinding media, control the ball-to-material ratio to be 3.5:1, adjust the ball mill speed to 70r / min, and wet grind for 30min;

[0047] The refined premix obtained after wet milling is dried to completely remove moisture, passed through a 40-mesh sieve, and then pressed into a compact by holding the pressure at 8MPa for 10s.

[0048] The compact was placed in a vacuum sintering furnace at 3 MPa and heated to about 380°C for 30 minutes. Then the compact was placed in a vacuum environment and argon gas was introduced until the ambient pressure was 3 MPa. The temperature was then increased to about 1490°C and sintered at 1490±10°C for 2.5 hours.

[0049] Example 3

[0050] Weigh out 0.05% boron, 2.5% aluminum nitride, 10% cobalt, 10% nickel, 2% chromium carbide and 75.45% tungsten carbide with a grain size of 5 μm by mass fraction.

[0051] Mix the above raw materials, add ethane to the solids in the grinding container, put in a Φ6.35mm alloy rod as the grinding media, control the ball-to-material ratio to be 3.5:1, adjust the ball mill speed to 70r / min, and wet grind for 30min;

[0052] The refined premix obtained after wet milling is dried to completely remove moisture, passed through a 40-mesh sieve, and then pressed into a compact by holding the pressure at 8MPa for 10s.

[0053] The compact was placed in a vacuum sintering furnace at 3 MPa and heated to about 420°C for 30 minutes. Then the compact was placed in a vacuum environment and argon gas was introduced until the ambient pressure was 3 MPa. The temperature was then increased to about 1410°C and sintered for 2.5 hours within the range of 1410±10°C.

[0054] <Comparative Example>

[0055] Comparative Example 1

[0056] Weigh out 10.3% cobalt, 10.3% nickel, 2% chromium carbide, and 77.4% tungsten carbide with a grain size of 12 μm, respectively, by mass fraction.

[0057] Mix the above raw materials, add ethane to the solids in the grinding container, put in a Φ6.35mm alloy rod as the grinding media, control the ball-to-material ratio to be 3.5:1, adjust the ball mill speed to 70r / min, and wet grind for 30min;

[0058] The refined premix obtained after wet milling is dried to completely remove moisture, passed through a 40-mesh sieve, and then pressed into a compact by holding the pressure at 8MPa for 10s.

[0059] The compact was placed in a vacuum sintering furnace at 3 MPa and heated to about 400°C for 30 minutes. Then, the compact was placed in a vacuum environment and argon gas was introduced until the ambient pressure was 3 MPa. The temperature was then increased to about 1450°C and sintered at 1400-1500°C for 2.5 hours.

[0060] Comparative Example 2

[0061] Weigh out 0.05% boron, 2.5% aluminum, 10% cobalt, 10% nickel, 2% chromium carbide and 75.45% tungsten carbide with a grain size of 12 μm by mass fraction.

[0062] Mix the above raw materials, add ethane to the solids in the grinding container, put in a Φ6.35mm alloy rod as the grinding media, control the ball-to-material ratio to be 3.5:1, adjust the ball mill speed to 70r / min, and wet grind for 30min;

[0063] The refined premix obtained after wet milling is dried to completely remove moisture, passed through a 40-mesh sieve, and then pressed into a compact by holding the pressure at 8MPa for 10s.

[0064] The compact was placed in a vacuum sintering furnace at 3 MPa and heated to about 400°C for 30 minutes. Then, the compact was placed in a vacuum environment and argon gas was introduced until the ambient pressure was 3 MPa. The temperature was then increased to about 1450°C and sintered at 1400-1500°C for 2.5 hours.

[0065] Comparative Example 3

[0066] Weigh out 0.01% boron, 8% aluminum nitride, 10% cobalt, 10% nickel, 2% chromium carbide, and 69.99% tungsten carbide with a grain size of 10 μm, respectively, by mass fraction.

[0067] Mix the above raw materials, add ethane to the solids in the grinding container, put in a Φ6.35mm alloy rod as the grinding media, control the ball-to-material ratio to be 3.5:1, adjust the ball mill speed to 70r / min, and wet grind for 30min;

[0068] The refined premix obtained after wet milling is dried to completely remove moisture, passed through a 40-mesh sieve, and then pressed into a compact by holding the pressure at 8MPa for 10s.

[0069] The compact was placed in a vacuum sintering furnace at 3 MPa and heated to about 400°C for 30 minutes. Then, the compact was placed in a vacuum environment and argon gas was introduced until the ambient pressure was 3 MPa. The temperature was then increased to about 1450°C and sintered at 1400-1500°C for 2.5 hours.

[0070] Comparative Example 4

[0071] Weigh out 0.5% boron, 0.5% aluminum nitride, 10% cobalt, 10% nickel, 2% chromium carbide, and 77% tungsten carbide with a grain size of 3 μm, respectively, by mass fraction.

[0072] Mix the above raw materials, add ethane to the solids in the grinding container, put in a Φ6.35mm alloy rod as the grinding media, control the ball-to-material ratio to be 3.5:1, adjust the ball mill speed to 70r / min, and wet grind for 30min;

[0073] The refined premix obtained after wet milling is dried to completely remove moisture, passed through a 40-mesh sieve, and then pressed into a compact by holding the pressure at 8MPa for 10s.

[0074] The compact was placed in a vacuum sintering furnace at 3 MPa and heated to about 400°C for 30 minutes. Then, the compact was placed in a vacuum environment and argon gas was introduced until the ambient pressure was 3 MPa. The temperature was then increased to about 1450°C and sintered at 1400-1500°C for 2.5 hours.

[0075] <Experimental Example>

[0076] Samples: Examples 1-3, Comparative Examples 1-4

[0077] (1) Metallographic structure

[0078] like Figure 1 This is a metallographic structure diagram of the in-situ generated Ni3Al WC grain hard alloy in Example 1. Figure 2 This is a metallographic structure diagram of the WC-Co-Ni cemented carbide in Comparative Example 1. Figure 3 The image shows the HAADF-STEM microstructure of the selected area of ​​the WC grain cemented carbide in Example 1. Figure 4 The image shows the HAADF-STEM microstructure of a selected area of ​​the WC-Co-Ni cemented carbide in Comparative Example 1. The comparison reveals that Example 1, based on Comparative Example 1, introduces aluminum nitride and boron, through... Figure 3 and Figure 4 The comparison shows that Figure 3 The formation of precipitated phases was observed in the medium-transmission dark field, and Figure 4 The absence of precipitates indicates that the WC grain cemented carbide in Example 1 can generate Ni3Al precipitates in situ, ultimately altering the microstructure of tungsten carbide. The tungsten carbide grains change from the prismatic shape of Comparative Example 1 (e.g., ...). Figure 2 (as shown) transforms into the passivation morphology of Example 1 (e.g.) Figure 1 As shown in the figure, after the tungsten carbide grains are passivated, the stress concentration is reduced compared to the original sharp prism face angles, which improves the fatigue toughness of the alloy.

[0079] (2) Material properties

[0080] The alloy products prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests to determine their strength, hardness, and other relevant material properties. The test results were recorded and summarized in Table 1 below:

[0081] Table 1. Material property test results of different WC alloy samples

[0082] Comparison items Bending strength (MPa) Hardness (HRC) <![CDATA[Alloy density (g / cm 3 )]]> Conventional grain size (μm) Example 1 2663 82.6 13.33 2.1 Example 2 2681 82.6 13.32 2.1 Example 3 2577 84.9 13.28 1.1 Comparative Example 1 2438 77.9 13.56 2.1 Comparative Example 2 2311 81.7 13.27 2.1 Comparative Example 3 2478 81.9 13.02 2.0 Comparative Example 4 2266 81.0 13.42 1.1

[0083] As shown in Table 1 above, compared with Comparative Examples 1-4, Examples 1-3 have significantly higher overall bending strength and hardness, while maintaining comparable alloy density and grain size. This indicates that the WC alloy and its preparation method proposed in this invention can improve the problems of low strength and poor durability caused by the large number of pores in existing Ni3Al bonded tungsten carbide hard alloys.

[0084] The cemented carbide samples prepared in Example 1 and Comparative Example 1 were used to determine their performance at a high temperature of 800℃. The results are summarized in Table 2 below:

[0085] Table 2. High-temperature material performance test results of different samples

[0086] Comparison items Test temperature (°C) Bending strength (MPa) Qualitative flexural modulus (MPa) Shear stress (MPa) Example 1 800 1731 18203 42.9 Comparative Example 1 800 1437 14660 37.1

[0087] As shown in Table 2 above, although the bending strength of the WC grain cemented carbide in Example 1 is lower than that in the room temperature environment under high temperature conditions, it still exhibits significantly higher bending strength, qualitative bending modulus, and shear stress than the WC-Co-Ni cemented carbide in Comparative Example 1. This indicates that the WC grain cemented carbide provided by this invention, through the improvement of raw materials, yields a cemented carbide that can generate Ni3Al in situ, with a smaller decrease in mechanical properties at high temperatures and superior mechanical properties under high temperature conditions.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing WC grain cemented carbide with in-situ Ni3Al formation, characterized in that, By mass fraction, it includes 0.01-0.1% boron, 0.5-5% aluminum nitride, 5-20% cobalt, 5-20% nickel, 0.5-3% chromium carbide, with the balance being tungsten carbide; the grain size of tungsten carbide is 5-15 μm; Includes the following steps: S1 Weigh the raw materials according to the specified amount, mix and wet grind, dry, sieve, and press into a compact; S2 The compact is placed in a vacuum sintering furnace, heated, and dewaxed for sintering. The dewaxing process is as follows: first, heat to 380-420℃ and hold for 20-40 minutes. After holding, transfer to a vacuum environment, then introduce argon gas. When introducing argon gas, control the ambient pressure to 1-5 MPa, and then continue to heat to 1400-1500℃ for sintering. The sintering time is 1-4 hours to obtain WC grain cemented carbide with in-situ Ni3Al formation.

2. The method for preparing in-situ Ni3Al WC grain cemented carbide according to claim 1, characterized in that, The total mass of cobalt and nickel accounts for 10-40 wt% of the total mass of the alloy.

3. The method for preparing in-situ Ni3Al WC grain cemented carbide according to claim 1, characterized in that, In step S1, during wet grinding, the ball mill speed is controlled at 60-80 r / min, and the ball milling time is 20-40 h.

4. The method for preparing in-situ Ni3Al WC grain cemented carbide according to claim 3, characterized in that, The ball-to-material ratio should be controlled at 2-5:1.

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