Arc erosion resistant hard alloy as well as preparation method and application thereof

Abstract

The invention discloses an arc erosion resistant hard alloy and a preparation method and application thereof. The hard alloy comprises 82-88% of WC, 8-12% of Co-Ni-Mn alloy, 1.5-3% of VC, 1-2% of Al2O3 and 0.5-1.5% of TiN, and the mass ratio of Co to Ni to Mn in the Co-Ni-Mn alloy is 6: 3: 1. According to the preparation method, VC, Al2O3 and TiN multi-element strengthening phases are coordinated and complemented, Co-Ni-Mn ternary binding phases are alloyed to resist high-temperature oxidation, and a homogeneous phase preparation process of high-energy wet grinding and segmented sintering is combined, so that the three properties of wear resistance, impact resistance and electric arc resistance of the mold are synergistically improved; the problems that an existing electrode mold is poor in arc erosion resistance, and abrasion resistance and impact resistance are difficult to consider at the same time are solved.

Description

Technical Field

[0001] This invention relates to the field of cemented carbide technology, and more specifically, to an arc-erosion resistant cemented carbide, its preparation method, and its application. Background Technology

[0002] In the electrode processing of new energy lithium batteries and sodium batteries, the electrode mold is the core forming component, directly determining the dimensional accuracy, surface quality, and production efficiency of the electrode. During electrode forming, the mold must withstand high-frequency mechanical impacts, friction, and electrochemical corrosion from the electrode material. Simultaneously, the high-speed stamping process easily generates instantaneous electric arcs due to static electricity accumulation, leading to arc erosion pits on the mold surface, accelerating wear and shortening its service life. As the new energy battery industry develops towards high-rate and thinner designs, electrode forming speeds have increased to 300-500 times / minute, placing higher demands on the arc erosion resistance, wear resistance, and impact resistance of the electrode mold. Existing materials can no longer meet the demands of ultra-high frequency and high reliability production; therefore, it is necessary to develop an electrode mold material that combines strong arc resistance, high wear resistance, and impact resistance.

[0003] Existing electrode molds use tool steel molds, which have low hardness and poor wear resistance, showing significant wear after 500,000 continuous cycles. WC-Co cemented carbide possesses good hardness and wear resistance, giving it an advantage over tool steel in mold materials. However, cemented carbide has lower toughness than tool steel, making it prone to chipping, cracking, or even complete breakage under impact loads, uneven stress, or stress concentration. Furthermore, the Co binder phase in WC-Co cemented carbide is easily oxidized and burned off at the high temperatures of an electric arc, forming a loose and porous oxide layer, accelerating mold failure. Therefore, WC-Co cemented carbide needs further improvements in toughness and arc resistance for use as electrode molds. CN121046673A, concerning a high-hardness tungsten carbide-cobalt cemented carbide and its preparation method, discloses a raw material formulation including 100 parts tungsten carbide powder, 6-20 parts cobalt powder, 0.2-1.3 parts composite sintering aid, 0.5-4 parts wet grinding media, and 0.1-3 parts forming agent. By adding a sintering aid composed of rare earth oxides and cobalt phosphide to the WC-Co raw material, the tungsten carbide-cobalt cemented carbide achieves improved hardness and wear resistance while simultaneously enhancing toughness, breaking the inverse relationship between hardness and toughness and obtaining excellent comprehensive mechanical properties. Although this patent provides a cemented carbide that meets the requirements of hardness, wear resistance, and toughness as a mold material, it still uses a single Co phase as the binder, resulting in weak resistance to arc erosion, which needs further improvement. Furthermore, the intergranular bonding force of WC is weak, making it prone to grain shedding under impact loads, leading to indentation defects on the electrode surface. Summary of the Invention

[0004] The main technical problem to be solved by the present invention is to provide an arc-erosion resistant cemented carbide that addresses the shortcomings of existing electrode mold materials, such as poor resistance to arc erosion and difficulty in achieving both wear resistance and impact resistance.

[0005] Another technical problem solved by the present invention is to provide a method for preparing arc-erosion resistant cemented carbide.

[0006] The present invention also provides its application in electrode molds based on this cemented carbide.

[0007] The objective of this invention is achieved through the following technical solution: An arc-erosion resistant cemented carbide comprises the following raw materials: WC 82-88wt%, Co-Ni-Mn alloy 8-12wt%, VC 1.5-3wt%, Al2O3 1-2wt%, and TiN 0.5-1.5wt%; wherein the mass ratio of Co, Ni, and Mn in the Co-Ni-Mn alloy is 6:3:1.

[0008] Furthermore, the arc erosion resistant cemented carbide raw material includes: 85wt% WC, 10wt% Co-Ni-Mn alloy, 2wt% VC, 1.5wt% Al2O3, and 1.5wt% TiN.

[0009] Furthermore, the average grain size of the WC is 0.8-1.5 μm.

[0010] A method for preparing an arc-erosion resistant cemented carbide, comprising the following steps: S1. Raw material mixing; Weigh out WC, Co-Ni-Mn alloy powder, VC, Al2O3, and TiN powder according to the component ratio, add anhydrous ethanol as the grinding medium, and ball mill in a ball mill to obtain a uniform mixed slurry. S2. Powder preparation; The mixed slurry is dried in a vacuum environment at 100-120℃ to remove the grinding media. The dried block material is crushed to obtain alloy powder with good flowability. S3. Compression molding; Alloy powder is loaded into a mold and cold isostatic pressing is used to obtain a mold blank with a density ≥92% by controlling the forming pressure to 180-220MPa and the holding time to 5-8min. S4. Segmented sintering; The mold blank is placed in a vacuum sintering furnace, and the vacuum degree is controlled to be ≥5×10-4Pa. First, the temperature is raised to 600℃ and held for 2 hours to remove the grease. Then, the temperature is raised to 1200℃ and held for 1 hour. Then, the temperature is raised to 1480℃ and held for 3 hours. Finally, the temperature is cooled to room temperature to obtain cemented carbide.

[0011] Furthermore, the ball-to-material ratio during ball milling is 15:1, the rotation speed is 250 r / min, and the wet milling time is 6-8 h.

[0012] Furthermore, the heating rate to 600°C is 5°C / min, the heating rate to 1200°C is 10°C / min, and the heating rate to 1480°C is 3°C / min.

[0013] Furthermore, the cooling process includes first cooling the furnace to 800°C, and then cooling it to room temperature at a rate of 5°C / min.

[0014] Furthermore, the cemented carbide also includes a surface strengthening treatment, the treatment steps of which include: plasma spraying the surface layer of the sintered cemented carbide blank, and then fine grinding it to a surface roughness Ra≤0.1μm to obtain a surface-strengthened cemented carbide.

[0015] Furthermore, the plasma spraying material is WC-12Co nanopowder, and the spraying thickness is 50-100μm.

[0016] The cemented carbide prepared by the above method is used in electrode molds.

[0017] Compared with existing technologies, the beneficial effects are: This invention employs a composite design of "multi-component reinforcing phase synergy + binder phase alloying + homogeneous preparation process". By precisely matching VC, Al2O3 and TiN in a certain proportion, complementary properties are achieved. The Co-Ni-Mn ternary binder phase solves the problem of high-temperature oxidation. Combined with high-energy wet grinding and segmented sintering processes, the three properties of "wear resistance, impact resistance and arc resistance" are synergistically improved under a homogeneous structure. It abandons the traditional single WC-Co structure and takes into account both performance and production efficiency.

[0018] This invention constructs a ternary synergistic strengthening mechanism of "VC grain refinement + Al2O3 corrosion-resistant barrier + TiN toughness enhancement". VC is used to refine WC grains to 0.8-1.5μm, improving basic hardness; Al2O3 forms a dense Al2O3-Co-Mn composite oxide film under high-temperature electric arc to block corrosive media; and TiN is used to form a coherent interface with WC to alleviate stress concentration. The three components are combined in a mass ratio of 1.5-3:1-2:0.5-1.5 to achieve performance balance, resulting in high hardness, high toughness, and corrosion resistance.

[0019] This invention employs a 6:3:1 Co-Ni-Mn ternary binder phase to replace the traditional pure Co binder phase. The Mn element lowers the sintering temperature to 1480℃ and improves the wettability of TiN with WC, while the Ni element enhances the interfacial bonding between the binder phase and the hard phase. Simultaneously, the composite oxide film formed synergistically by Mn and Co reduces the high-temperature oxidation rate by more than 10%, solving the problem of binder phase burn-off under electric arc conditions.

[0020] In this invention, the sintering activities of the multi-component components differ greatly. TiN and WC have poor wettability, and sintering temperatures that are too low easily lead to the formation of grain boundary pores; while temperatures that are too high cause abnormal growth of WC grains (>2μm), resulting in a decrease in hardness. Therefore, this invention adopts a sintering process of "low-temperature degreasing - medium-temperature preheating - high-temperature slow firing - gradient cooling". Degreasing is carried out completely at 600℃ for 2 hours, stress is eliminated by preheating at 1200℃ for 1 hour, slow firing at 1200-1480℃ at 3℃ / min promotes solid solution, densification is achieved by holding at 1480℃ for 3 hours, and cooling at 800℃ at 5℃ / min avoids thermal stress cracking, precisely controlling the WC grain size to around 1.0μm. Attached Figure Description

[0021] Figure 1 A schematic diagram of the microstructure of the cemented carbide prepared in Example 1; Figure 2 Etching pattern of the cemented carbide prepared in Example 1; Figure 3 Etching pattern of the cemented carbide prepared in Example 2; Figure 4 Etching pattern of the cemented carbide prepared in Example 3; Figure 5 Etching pattern of the cemented carbide prepared in Comparative Example 1; Figure 6 The etching pattern is for the cemented carbide prepared in Comparative Example 2. Detailed Implementation

[0022] The following examples further explain and clarify the invention, but the specific examples do not limit the invention in any way.

[0023] Example 1 This embodiment provides an arc-erosion resistant cemented carbide, the raw material composition of which includes: 85wt% WC, 10wt% Co-Ni-Mn alloy, 2wt% VC, 1.5wt% Al2O3, and 1.5wt% TiN. The average grain size of WC is 1.0μm, and the mass ratio of Co-Ni-Mn is 6:3:1.

[0024] The preparation steps include: S1. Premixing: Al2O3 and TiN are mixed in a 1:1 ratio, a small amount of ethanol is added to prepare a composite powder, and ultrasonically dispersed for 30 min; S2. Raw material mixing: Al2O3 and TiN composite powder are mixed with WC, Co-Ni-Mn alloy powder and VC. Anhydrous ethanol is added as the grinding medium and placed in a ball mill. The ball-to-material ratio is controlled at 15:1, with φ10mm coarse balls:φ5mm fine balls at a ratio of 2:1. The mixture is wet-milled at 250r / min for 7h to achieve a 95% uniformity of the dispersion of the reinforcing phase, resulting in a uniform mixed slurry.

[0025] S3. Powder preparation: The mixed slurry is vacuum dried at 110℃ to remove the grinding media. The dried block material is crushed and passed through a 200-mesh sieve to obtain alloy powder with good flowability. The alloy powder has a flowability ≥18s / 50g. Before grinding, the present invention premixes light-density Al2O3 and TiN to form a composite powder, which is then mixed with WC and a binder phase. During wet grinding, a strong shearing force is generated by a high speed of 250 r / min to suppress particle sedimentation. Combined with 200 mesh sieve to remove agglomerates, the distribution deviation of each component is ensured to be ≤5%.

[0026] S4. Pressing and Molding: The alloy powder is loaded into the mold, and a cold isostatic pressing process is adopted. The cold isostatic pressing is controlled at 200MPa and held for 6 minutes to ensure uniform density of the billet, resulting in a molded billet with a density of 6.8g / cm³. 3 .

[0027] S5. Segmented sintering: Place the mold blank into a vacuum sintering furnace, controlling the vacuum level at 8×10. -4 Pa was sintered according to the following curve: The temperature was increased from room temperature to 600℃ at a rate of 5℃ / min, and held for 2 hours for degreasing. Then, the temperature was increased from 600℃ to 1200℃ at a rate of 10℃ / min, and held for 1 hour. Next, the temperature was increased from 1200℃ to 1480℃ at a rate of 3℃ / min, and held for 3 hours. After being cooled from 1480℃ to 800℃ in the furnace, the temperature was further cooled to room temperature at a rate of 5℃ / min to obtain the cemented carbide billet.

[0028] S6. Surface strengthening: The surface of the sintered cemented carbide blank is subjected to plasma spraying. The plasma spraying material is WC-12Co nanopowder with a particle size of 50nm and a thickness of 80μm. After spraying, the surface is finely ground with a diamond grinding wheel until the surface roughness is Ra=0.08μm to obtain the finished electrode mold.

[0029] Example 2 This embodiment provides an arc-erosion resistant cemented carbide, the raw material composition of which includes: 88wt% WC, 8wt% Co-Ni-Mn alloy, 2.5wt% VC, 1.0wt% Al2O3, and 0.5wt% TiN. The average grain size of WC is 0.8μm, and the mass ratio of Co-Ni-Mn is 6:3:1.

[0030] The preparation steps include: S1. Premixing: Al2O3 and TiN are mixed in a 1:1 ratio, a small amount of ethanol is added to prepare a composite powder, and ultrasonically dispersed for 30 min; S2. Raw material mixing: Al2O3 and TiN composite powder is mixed with WC, Co-Ni-Mn alloy powder and VC. Anhydrous ethanol is added as the grinding medium and placed in a ball mill. The ball-to-material ratio is controlled at 15:1, with φ10mm coarse balls:φ5mm fine balls at a ratio of 2:1. The mixture is wet-milled at 250r / min for 8 hours to obtain a uniform mixed slurry.

[0031] S3. Powder preparation: The mixed slurry is vacuum dried at 110℃ to remove the grinding media. The dried block material is crushed and passed through a 200-mesh sieve to obtain alloy powder with good flowability. The alloy powder has a flowability ≥18s / 50g. S4. Pressing and molding: The alloy powder is loaded into the mold and cold isostatic pressing is used. The cold isostatic pressing is controlled at 220MPa and held for 5 minutes to obtain the mold blank.

[0032] S5. Segmented sintering: Place the mold blank into a vacuum sintering furnace, controlling the vacuum level at 8×10. -4 Pa was sintered according to the following curve: The temperature was increased from room temperature to 600℃ at a rate of 5℃ / min, and held for 2 hours for degreasing. Then, the temperature was increased from 600℃ to 1200℃ at a rate of 10℃ / min, and held for 1 hour. Next, the temperature was increased from 1200℃ to 1460℃ at a rate of 3℃ / min, and held for 3 hours. After being cooled from 1480℃ to 800℃ in the furnace, the temperature was further cooled to room temperature at a rate of 5℃ / min to obtain the cemented carbide billet.

[0033] S6. Surface strengthening: The surface of the sintered cemented carbide blank is subjected to plasma spraying. The plasma spraying material is WC-12Co nanopowder with a particle size of 50nm and a thickness of 80μm. After spraying, the surface is finely ground with a diamond grinding wheel until the surface roughness is Ra=0.08μm to obtain the finished electrode mold.

[0034] Example 3 This embodiment provides an arc-erosion resistant cemented carbide, the raw material composition of which includes: 82wt% WC, 12wt% Co-Ni-Mn alloy, 1.5wt% VC, 2.0wt% Al2O3, and 1.5wt% TiN. The average grain size of WC is 1.5μm, and the mass ratio of Co-Ni-Mn is 6:3:1.

[0035] The preparation steps include: S1. Premixing: Al2O3 and TiN are mixed in a 1:1 ratio, a small amount of ethanol is added to prepare a composite powder, and ultrasonically dispersed for 30 min; S2. Raw material mixing: Al2O3 and TiN composite powder are mixed with WC, Co-Ni-Mn alloy powder and VC. Anhydrous ethanol is added as the grinding medium and placed in a ball mill. The ball-to-material ratio is controlled at 15:1, with φ10mm coarse balls:φ5mm fine balls at a ratio of 2:1. The mixture is wet-milled at 250r / min for 6 hours to obtain a uniform mixed slurry.

[0036] S3. Powder preparation: The mixed slurry is vacuum dried at 110℃ to remove the grinding media. The dried block material is crushed and passed through a 200-mesh sieve to obtain alloy powder with good flowability. The alloy powder has a flowability ≥18s / 50g. S4. Pressing and Molding: The alloy powder is loaded into the mold, and a cold isostatic pressing process is adopted. The cold isostatic pressing is controlled at 200MPa and held for 6min to obtain the mold blank with a density of 6.8g / cm³. 3 .

[0037] S5. Segmented sintering: Place the mold blank into a vacuum sintering furnace, controlling the vacuum level at 8×10. -4 Pa was sintered according to the following curve: The temperature was increased from room temperature to 600℃ at a rate of 5℃ / min, and held for 2 hours for degreasing. Then, the temperature was increased from 600℃ to 1200℃ at a rate of 10℃ / min, and held for 1 hour. Next, the temperature was increased from 1200℃ to 1480℃ at a rate of 2℃ / min, and held for 4 hours. After being cooled from 1480℃ to 800℃ in the furnace, the temperature was further cooled to room temperature at a rate of 5℃ / min to obtain the cemented carbide billet.

[0038] S6. Surface strengthening: The surface of the sintered cemented carbide blank is subjected to plasma spraying. The plasma spraying material is WC-12Co nanopowder with a particle size of 50nm and a thickness of 80μm. After spraying, the surface is finely ground with a diamond grinding wheel until the surface roughness is Ra=0.08μm to obtain the finished electrode mold.

[0039] Comparative Example 1 This comparative example provides a WC-Co alloy, the composition of which includes 90wt% WC and 10wt% Co. The preparation steps include: S1. Mix WC and Co powders, add anhydrous ethanol as the grinding medium, and wet grind in a ball mill for 7 hours to obtain a uniform mixed slurry.

[0040] S2. The mixed slurry is vacuum dried at 110℃ to remove the grinding media. The dried block material is crushed and passed through a 200-mesh sieve to obtain alloy powder. S3. The alloy powder is loaded into a mold and cold isostatic pressing is used to obtain a mold blank. The mold blank is then placed in a vacuum sintering furnace and heated from room temperature to 1450°C, and held at that temperature for 2 hours. After cooling to room temperature, a cemented carbide blank is obtained.

[0041] Comparative Example 2 This comparative example provides a cemented carbide whose composition includes: 87wt% WC, 10wt% Co, and 3wt% VC.

[0042] The preparation steps include: S1. Raw material mixing: Mix WC, Co powder, and VC, add anhydrous ethanol as grinding medium, put it into a ball mill, control the ball-to-material ratio to be 15:1, where the ratio of φ10mm coarse balls to φ5mm fine balls is 2:1, wet grind at 250r / min for 7h to obtain a uniform mixed slurry.

[0043] S2. Powder preparation: The mixed slurry is vacuum dried at 110℃ to remove the grinding media. The dried block material is crushed and passed through a 200-mesh sieve to obtain alloy powder with good flowability. The alloy powder has a flowability ≥18s / 50g. S3. Pressing and Molding: The alloy powder is loaded into the mold, and a cold isostatic pressing process is adopted. The cold isostatic pressing is controlled at 200MPa and held for 6min to obtain the mold blank with a density of 6.8g / cm³. 3 .

[0044] S4. Segmented sintering: Place the mold blank into a vacuum sintering furnace, controlling the vacuum level at 8×10⁻⁶. -4 Pa was sintered according to the following curve: The temperature was increased from room temperature to 600℃ at a rate of 5℃ / min, and held for 2 hours for degreasing. Then, the temperature was increased from 600℃ to 1200℃ at a rate of 10℃ / min, and held for 1 hour. Next, the temperature was increased from 1200℃ to 1480℃ at a rate of 3℃ / min, and held for 3 hours. After being cooled from 1480℃ to 800℃ in the furnace, the temperature was further cooled to room temperature at a rate of 5℃ / min to obtain the cemented carbide billet.

[0045] S5. Surface strengthening: The surface of the sintered cemented carbide blank is subjected to plasma spraying treatment. The plasma spraying material is WC-12Co nanopowder with a particle size of 50nm and a thickness of 80μm. After spraying, the surface is finely ground with a diamond grinding wheel until the surface roughness is Ra=0.08μm to obtain the finished electrode mold.

[0046] The performance of the cemented carbide in the examples and comparative examples was tested, and the test results are shown in Table 1 below: Table 1

[0047] As shown in the table above, compared to traditional WC-Co alloys and cemented carbides with a single reinforcing phase (VC), the present invention employs a compositional design that combines synergistic reinforcing phases and binder phase alloying, resulting in significant improvements in hardness, strength, and toughness. In particular, the cemented carbides described in this invention exhibit excellent resistance to arc erosion.

[0048] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A hard alloy resistant to arc erosion, characterized in that, Its raw materials include: WC 82-88wt%, Co-Ni-Mn alloy 8-12wt%, VC 1.5-3wt%, Al2O3 1-2wt%, TiN 0.5-1.5wt%; in the Co-Ni-Mn alloy, the mass ratio of Co, Ni and Mn is 6:3:

1.

2. The arc-erosion resistant cemented carbide according to claim 1, characterized in that, Its raw materials include: 85wt% WC, 10wt% Co-Ni-Mn alloy, 2wt% VC, 1.5wt% Al2O3, and 1.5wt% TiN.

3. The arc-erosion resistant cemented carbide according to claim 1 or 2, characterized in that, The average grain size of the WC is 0.8-1.5 μm.

4. A method for preparing an arc-erosion resistant cemented carbide, characterized in that, The preparation steps include: S1. Raw material mixing; Weigh out WC, Co-Ni-Mn alloy powder, VC, Al2O3, and TiN powder according to the component ratio, add anhydrous ethanol as the grinding medium, and ball mill in a ball mill to obtain a uniform mixed slurry. S2. Powder preparation; The mixed slurry is dried in a vacuum environment at 100-120℃ to remove the grinding media. The dried block material is crushed to obtain alloy powder with good flowability. S3. Compression molding; Alloy powder is loaded into a mold and cold isostatic pressing is used to obtain a mold blank with a density ≥92% by controlling the forming pressure to 180-220MPa and the holding time to 5-8min. S4. Segmented sintering; The mold blank is placed in a vacuum sintering furnace, and the vacuum degree is controlled to be ≥5×10-4Pa. First, the temperature is raised to 600℃ and held for 2 hours to remove the grease. Then, the temperature is raised to 1200℃ and held for 1 hour. Then, the temperature is raised to 1480℃ and held for 3 hours. Finally, the temperature is cooled to room temperature to obtain cemented carbide.

5. The method for preparing the arc-erosion resistant cemented carbide according to claim 4, characterized in that, The ball-to-material ratio during ball milling is 15:1, the rotation speed is 250 r / min, and the wet milling time is 6-8 h.

6. The method for preparing the arc-erosion resistant cemented carbide according to claim 4, characterized in that, The heating rate to 600℃ is 5℃ / min, the heating rate to 1200℃ is 10℃ / min, and the heating rate to 1480℃ is 3℃ / min.

7. The method for preparing the arc-erosion resistant cemented carbide according to claim 4, characterized in that, The cooling process includes first cooling the furnace to 800°C, and then cooling it to room temperature at a rate of 5°C / min.

8. The method for preparing the arc-erosion resistant cemented carbide according to claim 4, characterized in that, The cemented carbide also includes surface strengthening treatment, the treatment steps of which include: plasma spraying the surface layer of the sintered cemented carbide blank, and then fine grinding it to a surface roughness Ra≤0.1μm to obtain surface-strengthened cemented carbide.

9. The method for preparing the arc-erosion resistant cemented carbide according to claim 4, characterized in that, The plasma spraying material is WC-12Co nanopowder, with a spraying thickness of 50-100μm.

10. The cemented carbide prepared by the method according to any one of claims 4-9, characterized in that, The cemented carbide is used in electrode molds.

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