Super coarse grain high toughness cemented carbide and method for producing the same

Abstract

The application provides a kind of super coarse grain high toughness hard alloy and its preparation method, belongs to alloy technical field.The preparation method includes: according to tungsten carbide 88%~94%, cobalt powder 6%~12%, molybdenum carbide 0.01%~0.2%, chromium carbide 0.01%~0.1% of weight percentage of raw material batching;Carbon content is 4.69%~5.77% of total mass of raw material;Cobalt powder, molybdenum carbide and chromium carbide are mixed and dry ground;Paraffin, tungsten carbide and alcohol are added for wet grinding;Spray drying, pressing and sintering are carried out in turn.The application adds trace amounts of chromium carbide and molybdenum carbide, only retains the solid solution strengthening effect of chromium carbide and molybdenum carbide on the binder phase and the modification effect on WC / Co interface, ensures the high toughness of super coarse grain hard alloy;Combined with specific grinding process, the problem of mutual contradiction, difficult to reconcile and low cobalt phase strength leading to tungsten carbide grain peeling in hard alloy is solved.

Description

Technical Field

[0001] This invention belongs to the field of alloy technology, and specifically relates to an ultra-coarse-grained high-toughness cemented carbide and its preparation method. Background Technology

[0002] Ultra-coarse-grained cemented carbide typically refers to cemented carbide with an average WC grain size greater than 6 micrometers. Due to its excellent toughness, thermal shock resistance, and wear resistance, this type of cemented carbide is well-suited for continuous operations under extreme conditions such as alternating hot and cold temperatures and alternating soft and hard conditions. However, as global resources extend into deeper and harder rock formations, the market is placing higher demands on the comprehensive performance of ultra-coarse-grained cemented carbide in the face of unpredictable and complex working conditions and ever-increasing requirements for construction efficiency.

[0003] Hardness and toughness are two key indicators for evaluating the performance of ultra-coarse-grained cemented carbide. These two properties often exhibit an inverse relationship, making them difficult to reconcile. In mining and tunneling, however, it is desirable for ultra-coarse-grained cemented carbides to possess both high hardness and high toughness to ensure construction efficiency and the normal operation of the carbide teeth, preventing abnormal wear and fracture failures under special working conditions.

[0004] To simultaneously improve the hardness and toughness of cemented carbide, scholars both domestically and internationally have conducted extensive research. CN119287238A discloses a method for improving the grain morphology of WC to toughen cemented carbide. This method, by weight percentage, comprises the following components: 0.5%–5% molybdenum carbide, 10%–15% cobalt, 0.5%–3% chromium carbide, with the balance being WC; the ball-to-material ratio is 3:1–5:1, and the ball milling time is 18–32 hours. The method aims to toughen the cemented carbide by improving the grain morphology of WC. However, this method is not suitable for ultra-coarse cemented carbide. Excessive chromium and molybdenum carbide inhibit grain growth and refine the grains, thereby reducing the alloy's toughness, which contradicts the initial goal of high toughness in ultra-coarse cemented carbide. Furthermore, an excessively high ball-to-material ratio and ball milling time will excessively break down the WC, making it difficult to prepare ultra-coarse cemented carbide.

[0005] Therefore, there is an urgent need to develop a formulation and optimized preparation method suitable for ultra-coarse-grained cemented carbide, so as to improve the toughness of the alloy without reducing its hardness, thereby meeting the performance requirements of ultra-coarse-grained cemented carbide under complex working conditions. Summary of the Invention

[0006] In view of this, the present invention provides an ultra-coarse-grained high-toughness cemented carbide and its preparation method, aiming to solve at least one technical problem in the background art.

[0007] This invention is implemented as follows: The first aspect of this invention provides a method for preparing an ultra-coarse-grained, high-toughness cemented carbide, the method comprising the following steps: S1. Prepare raw materials according to the following weight percentages: tungsten carbide 88%~94%, cobalt powder 6%~12%, molybdenum carbide 0.01%~0.2%, and chromium carbide 0.01%~0.1%; adjust the carbon content to 4.69%~5.77% of the total mass of raw materials. S2, cobalt powder, molybdenum carbide and chromium carbide are mixed and dry-milled; S3. Add paraffin, tungsten carbide and alcohol to the dry-milled mixture and perform wet milling; S4. After wet grinding, spray drying, pressing and molding and sintering are carried out in sequence.

[0008] Furthermore, in S1, the Fisher particle sizes of the tungsten carbide, cobalt powder, molybdenum carbide, and chromium carbide are 27μm~35μm, 1.0μm~1.5μm, 1.5μm~2.5μm, and <1μm, respectively.

[0009] Furthermore, in S2, the dry grinding time is 30 min to 120 min, the grinding medium for dry grinding is a tungsten cobalt alloy grinding rod, the diameter of the grinding medium is 10 mm to 13 mm, and the mass of the grinding medium is 1.8 times to 3.5 times the total mass of the raw materials.

[0010] Furthermore, in S3, the wet milling time is 5h~15h, the amount of alcohol added is 180mL / kg~350mL / kg of raw material, and the amount of paraffin added is 2%~2.2% of the total mass of raw material.

[0011] Furthermore, in S4, the sintering temperature is 1430℃~1500℃, and the sintering time is 2h~3h.

[0012] The second aspect of the present invention provides an ultra-coarse-grained high-toughness cemented carbide, which is prepared by the aforementioned method for preparing an ultra-coarse-grained high-toughness cemented carbide.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention, by adding trace amounts of chromium carbide and molybdenum carbide, retains only the solid solution strengthening effect of chromium carbide and molybdenum carbide on the binder phase and the modification effect on the WC / Co interface, without negatively affecting the growth of WC grains, thus ensuring the high toughness of the ultra-coarse-grained cemented carbide. Combined with a specific grinding process, it solves the problems of the contradiction and difficulty in reconciling hardness and toughness in cemented carbide, as well as the problem that the low strength of the cobalt phase easily leads to the spalling of tungsten carbide grains. Thus, it achieves improved toughness without sacrificing hardness, enabling it to work stably under normal or special working conditions such as mining, rock drilling, and tunnel boring machines, and extending the service life of the alloy.

[0014] 2. This invention effectively solves the agglomeration of chromium carbide and molybdenum carbide by pre-grinding chromium carbide, molybdenum carbide and cobalt powder and by a specific ball milling process, improves the uniformity of their distribution in cobalt powder and alloy, effectively enhances the solid solution strengthening effect of chromium carbide and molybdenum carbide on the cobalt phase, and improves the bonding strength of WC / Co interface.

[0015] 3. By rationally controlling the carbon content of the raw materials, this invention avoids the generation of brittle phases, fully utilizes the performance of cemented carbide, and improves the density and performance consistency of the alloy.

[0016] 4. This invention achieves a two-way improvement in the strength and toughness of the cobalt phase by solid solution strengthening of the cobalt phase in ultra-coarse-grained cemented carbide. It effectively avoids the occurrence of severe wear caused by insufficient cobalt phase strength in ultra-coarse-grained cemented carbide under extreme working conditions, which leads to premature peeling of WC grains and aggravated wear, as well as the occurrence of alloy fracture due to insufficient toughness. It achieves a balance between hardness and toughness in ultra-coarse-grained cemented carbide and extends the service life of the alloy. Attached Figure Description

[0017] Figure 1 Metallographic image of the alloy prepared in Example 1 of this invention; Figure 2 Metallographic image of the alloy prepared in Example 2 of this invention; Figure 3 Metallographic image of the alloy prepared in Example 3 of this invention; Figure 4 Metallographic diagram of the alloy prepared in Comparative Example 1 of this invention; Figure 5 Metallographic diagram of the alloy prepared in Comparative Example 2 of this invention; Figure 6 Metallographic image of the alloy prepared in Comparative Example 3 of this invention; Figure 7 Metallographic diagram of the alloy prepared in Comparative Example 4 of this invention; Figure 8 Metallographic image of the alloy prepared in Comparative Example 5 of this invention; Figure 9 This is a metallographic image of the alloy prepared in Comparative Example 6 of this invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] Example 1 A method for preparing an ultra-coarse-grained, high-toughness cemented carbide includes the following steps: S1. Take tungsten carbide (93.076wt%) with a Fisher's Squared Size (FSSS) of 28μm, cobalt powder (6wt%) with an FSSS of 1.0μm, molybdenum carbide (0.03wt%) with an FSSS of 1.5μm, and chromium carbide (0.02wt%) with an FSSS of 0.8μm for raw material preparation, and adjust the total carbon of the raw materials to 5.71% by adding tungsten powder with an FSSS of 1.0μm (0.874wt%).

[0020] S2. Add cobalt powder, molybdenum carbide and chromium carbide to a ball mill and dry grind them together with the grinding media for 40 minutes. The grinding media is a tungsten cobalt alloy grinding rod with a diameter of 13 mm. The mass of the grinding media is 1.8 times the total amount of raw materials, that is, the ball-to-material ratio is 1.8:1.

[0021] S3. After dry grinding, paraffin wax is added while the ball mill is rotating. After the paraffin wax is added, tungsten carbide and alcohol are added sequentially for wet grinding. The wet grinding time is 13 hours, the amount of alcohol added is 180 mL / kg of raw material, and the amount of paraffin wax added is 2% of the total mass of raw material.

[0022] S4. After wet grinding, spray drying and pressing are carried out; finally, the pressed product is sintered at a temperature of 1450℃ for 2 hours to obtain ultra-coarse cemented carbide.

[0023] The metallographic features of the ultra-coarse cemented carbide produced in this embodiment are as follows: Figure 1 As shown, the tungsten carbide particles are relatively uniform in size, with an average grain size of 6.5 μm. There are no abnormally large or excessively refined grains. The cobalt phase is uniformly distributed. The alloy hardness HV10 is 1112, and the fracture toughness is 21.8 MPa·m. 1 / 2 .

[0024] Example 2 A method for preparing an ultra-coarse-grained, high-toughness cemented carbide includes the following steps: S1. Take tungsten carbide with FSSS of 30μm (91.807wt%), cobalt powder with FSSS of 1.2μm (8wt%), molybdenum carbide with FSSS of 1.8μm (0.05wt%), and chromium carbide with FSSS of 0.7μm (0.05wt%) for raw material preparation, and add pure carbon black (0.093wt%) to adjust the total carbon of the raw materials to 5.73%.

[0025] S2. Add cobalt powder, molybdenum carbide and chromium carbide to a ball mill and dry grind them together with the grinding media for 60 minutes. The grinding media is a tungsten-cobalt alloy grinding rod with a diameter of 13 mm. The mass of the grinding media is 2.5 times the total mass of the raw materials, that is, the ball-to-material ratio is 2.5:1.

[0026] S3. After dry grinding, paraffin wax is added while the ball mill is rotating. After the paraffin wax is added, tungsten carbide and alcohol are added sequentially for wet grinding. The wet grinding time is 11 hours, the amount of alcohol added is 250 mL / kg of raw material, and the amount of paraffin wax added is 2.2% of the total mass of raw material.

[0027] S4. After wet grinding, spray drying and pressing are carried out; then the pressed product is sintered at a temperature of 1470℃ for 2 hours to obtain ultra-coarse cemented carbide.

[0028] The metallographic features of the ultra-coarse cemented carbide produced in this embodiment are as follows: Figure 2 As shown, the tungsten carbide particles are relatively uniform in size, with an average grain size of 7.1 μm. There are no abnormally large or excessively refined grains. The cobalt phase is uniformly distributed. The alloy hardness HV10 is 1075, and the fracture toughness is 22.5 MPa·m. 1 / 2 .

[0029] Example 3 A method for preparing an ultra-coarse-grained, high-toughness cemented carbide includes the following steps: S1. Take tungsten carbide (89.616wt%) with FSSS of 33μm, cobalt powder (10wt%) with FSSS of 1.5μm, molybdenum carbide (0.08wt%) with FSSS of 2.1μm, and chromium carbide (0.06wt%) with FSSS of 0.6μm for raw material preparation, and add pure carbon black (0.244wt%) to adjust the total carbon of the raw materials to 5.75%.

[0030] S2. Add cobalt powder, molybdenum carbide and chromium carbide to a ball mill and dry grind them together with the grinding media for 60 minutes. The grinding media are tungsten cobalt alloy grinding rods with a diameter of 13 mm. The mass of the grinding media is 3.2 times the total amount of raw materials, that is, the ball-to-material ratio is 3.2:1.

[0031] S3. After dry grinding, paraffin wax is added while the ball mill is rotating. After the paraffin wax is added, tungsten carbide and alcohol are added sequentially for wet grinding. The wet grinding time is 9 hours, the amount of alcohol added is 320 mL / kg of raw material, and the amount of paraffin wax added is 2.1% of the total mass of raw material.

[0032] S4. After wet grinding, spray drying and pressing are carried out. The pressed product is then sintered at a temperature of 1490℃ for 2.5 hours to obtain ultra-coarse cemented carbide.

[0033] The metallographic features of the ultra-coarse cemented carbide produced in this embodiment are as follows: Figure 3As shown, the tungsten carbide particles are relatively uniform in size, with an average grain size of 7.5 μm. There are no abnormally large or excessively refined grains. The cobalt phase is uniformly distributed. The alloy hardness HV10 is 1067, and the fracture toughness is 23.7 MPa·m. 1 / 2 .

[0034] Comparative Example 1 A method for preparing an ultra-coarse-grained, high-toughness cemented carbide includes the following steps: S1. Take tungsten carbide (93.15wt%) with FSSS of 28μm and cobalt powder (6wt%) with FSSS of 1.0μm for raw material preparation, and add tungsten powder (0.85wt%) with FSSS of 1.0μm to adjust the total carbon of the raw materials to 5.71%.

[0035] S2. Add cobalt powder to a ball mill and dry grind it together with the grinding media for 40 minutes. The grinding media is a tungsten-cobalt alloy grinding rod with a diameter of 13 mm. The mass of the grinding media is 1.8 times the total mass of the raw materials, i.e., the ball-to-material ratio is 1.8:1.

[0036] S3. After dry grinding, paraffin wax is added while the ball mill is rotating. After the paraffin wax is added, tungsten carbide and alcohol are added sequentially for wet grinding. The wet grinding time is 13 hours, the amount of alcohol added is 180 mL / kg of raw material, and the amount of paraffin wax added is 2% of the total mass of raw material.

[0037] S4. After wet grinding, spray drying and pressing are carried out; then the pressed product is sintered at a temperature of 1450℃ for 2 hours to obtain ultra-coarse cemented carbide.

[0038] The only difference between this comparative example and Example 1 is that molybdenum carbide and chromium carbide were not added, resulting in a decrease in the hardness and fracture toughness of the alloy.

[0039] The metallographic features of the ultra-coarse hard alloy prepared in this comparative example are as follows: Figure 4 As shown, the tungsten carbide particles are relatively uniform in size, with an average grain size of 6.7 μm. The cobalt phase is uniformly distributed, but the alloy hardness HV10 is 1083 and the fracture toughness is 20.9 MPa·m. 1 / 2 .

[0040] Comparative Example 2 A method for preparing an ultra-coarse-grained, high-toughness cemented carbide includes the following steps: S1. Prepare materials by taking tungsten carbide with FSSS of 30μm, cobalt powder with FSSS of 1.2μm, molybdenum carbide with FSSS of 1.8μm, and chromium carbide with FSSS of 0.7μm. The mass percentage of tungsten carbide with FSSS of 30μm is 91.807%, the mass percentage of cobalt powder with FSSS of 1.2μm is 8%, the mass percentage of molybdenum carbide with FSSS of 1.8μm is 0.05%, and the mass percentage of chromium carbide with FSSS of 0.7μm is 0.05%. Add pure carbon black (0.093wt%) to adjust the total carbon of the mixture to 5.73%.

[0041] S2. Paraffin wax, cobalt powder, molybdenum carbide, chromium carbide, tungsten carbide, and alcohol are sequentially added to a ball mill and wet-milled with grinding media. The grinding media are tungsten-cobalt alloy grinding rods with a diameter of 13 mm. The mass of the grinding media is 2.5 times the total mass of the raw materials, i.e., the ball-to-material ratio is 2.5:1. The amount of alcohol added is 250 mL / kg of raw materials, and the amount of paraffin wax added is 2.2% of the total mass of the raw materials. The wet milling time is 11 hours.

[0042] S3. After wet grinding, spray drying and pressing are carried out. The pressed product is then sintered at a temperature of 1470℃ for 2 hours to obtain ultra-coarse cemented carbide.

[0043] The only difference between this comparative example and Example 2 is that the dry grinding step was omitted, and instead, cobalt powder, molybdenum carbide and chromium carbide were added to the ball mill and wet-milled together with the grinding media; the hardness and fracture toughness of the alloy produced were slightly reduced.

[0044] The metallographic features of the ultra-coarse cemented carbide prepared in this comparative example are as follows: Figure 5 As shown, the tungsten carbide particles are relatively uniform in size, without abnormal growth or excessive grain refinement. The average grain size is 7.3 μm. The cobalt phase is uniformly distributed. The alloy hardness HV10 is 1062, and the fracture toughness is 22.1 MPa·m. 1 / 2 .

[0045] Comparative Example 3 A method for preparing an ultra-coarse-grained, high-toughness cemented carbide includes the following steps: S1. Take tungsten carbide (89.118wt%) with a Fisher's Squared Size (FSSS) of 33μm, cobalt powder (10wt%) with an FSSS of 1.5μm, molybdenum carbide (0.08wt%) with an FSSS of 2.1μm, and chromium carbide (0.6wt%) with an FSSS of 0.6μm for raw material preparation, and add pure carbon black (0.202wt%) to adjust the total carbon of the raw materials to 5.75%.

[0046] S2. Add cobalt powder, molybdenum carbide and chromium carbide to a ball mill and dry grind them together with the grinding media for 60 minutes. The grinding media is a tungsten cobalt alloy grinding rod with a diameter of 13 mm. The mass of the grinding media is 3.2 times the total mass of the raw materials, that is, the ball-to-material ratio is 3.2:1.

[0047] S3. After dry grinding, paraffin wax is added while the ball mill is rotating. After the paraffin wax is added, tungsten carbide and alcohol are added sequentially for wet grinding. The wet grinding time is 9 hours, the amount of alcohol added is 320 mL / kg of raw material, and the amount of paraffin wax added is 2.1% of the total mass of raw material.

[0048] S4. After wet grinding, spray drying and pressing are carried out. The pressed product is then sintered at a temperature of 1490℃ for 2.5 hours to obtain ultra-coarse cemented carbide.

[0049] The only difference between this comparative example and Example 3 is that the amount of chromium carbide is increased from 0.06wt% to 0.6wt%, and the tungsten carbide content is reduced accordingly. The results show that the fracture toughness of the alloy prepared in this comparative example is significantly reduced.

[0050] The metallographic features of the ultra-coarse cemented carbide prepared in this comparative example are as follows: Figure 6 As shown, the tungsten carbide particles are uneven in size, with an average grain size of 5.3 μm. The WC grains are significantly refined and have extremely irregular morphology, increasing the alloy's brittleness. The alloy's hardness (HV10) is 1183, and its fracture toughness is 18.73 MPa·m. 1 / 2 .

[0051] Comparative Example 4 A method for preparing an ultra-coarse-grained, high-toughness cemented carbide, comprising the following steps: S1. Take tungsten carbide (93.932wt%) with a Fisher's Squared Score (FSSS) of 28μm, cobalt powder (6wt%) with an FSSS of 1.0μm, molybdenum carbide (0.03wt%) with an FSSS of 1.5μm, and chromium carbide (0.02wt%) with an FSSS of 0.8μm for raw material preparation, and add pure carbon black (0.018wt%) to adjust the total carbon of the raw materials to 5.78%.

[0052] S2. Add cobalt powder, molybdenum carbide and chromium carbide to a ball mill and dry grind them together with the grinding media for 40 minutes. The grinding media are tungsten-cobalt alloy grinding rods with a diameter of 13 mm. The mass of the grinding media is 1.8 times the total mass of the raw materials, i.e., the ball-to-material ratio is 1.8:1.

[0053] S3. After dry grinding, paraffin wax is added while the ball mill is rotating. After the paraffin wax is added, tungsten carbide and alcohol are added sequentially for wet grinding. The wet grinding time is 13 hours, the amount of alcohol added is 180 mL / kg of raw material, and the amount of paraffin wax added is 2% of the total mass of raw material.

[0054] S4. After wet grinding, spray drying and pressing are carried out. The pressed product is then sintered at a temperature of 1450℃ for 2 hours to obtain ultra-coarse cemented carbide.

[0055] The only difference between this comparative example and Example 1 is that the total carbon content of the raw materials was adjusted from 5.71% to 5.78%, resulting in a sharp decrease in the fracture toughness of the alloy.

[0056] The metallographic features of the ultra-coarse cemented carbide prepared in this comparative example are as follows: Figure 7 As shown, the alloy undergoes carburizing, producing a brittle phase. The alloy hardness (HV10) is 1176, and the fracture toughness is 18.3 MPa·m. 1 / 2 .

[0057] Comparative Example 5 The only difference between this comparative example and Example 3 is that the amount of molybdenum carbide is increased from 0.08wt% to 0.6wt%, and the tungsten carbide content is reduced accordingly. All other steps and conditions are the same as in Example 3.

[0058] The metallographic features of the ultra-coarse cemented carbide prepared in this comparative example are as follows: Figure 8 As shown, the tungsten carbide particles are uneven in size; the alloy hardness HV10 is 1197, and the fracture toughness is 18.95 MPa·m. 1 / 2 .

[0059] Comparative Example 6 The only difference between this comparative example and Example 3 is that the ball-to-material ratio in S3 is adjusted from 3.2:1 to 4:1; the wet milling time is increased from 9h to 18h; and the other steps and conditions are the same as in Example 3.

[0060] The metallographic features of the ultra-coarse cemented carbide prepared in this comparative example are as follows: Figure 9 As shown, the WC grains are severely fragmented; the alloy hardness HV10 is 1269, and the fracture toughness is 17.23 MPa·m. 1 / 2 The toughness of the alloy decreases sharply.

[0061] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing an ultra-coarse-grained, high-toughness cemented carbide, characterized in that, The preparation method includes the following steps: S1. Prepare raw materials according to the following weight percentages: tungsten carbide 88%~94%, cobalt powder 6%~12%, molybdenum carbide 0.01%~0.2%, and chromium carbide 0.01%~0.1%; adjust the carbon content to 4.69%~5.77% of the total mass of raw materials. S2, cobalt powder, molybdenum carbide and chromium carbide are mixed and dry-milled; S3. Add paraffin, tungsten carbide and alcohol to the dry-milled mixture and perform wet milling; S4. After wet grinding, spray drying, pressing and molding and sintering are carried out in sequence.

2. The method for preparing an ultra-coarse-grained high-toughness cemented carbide according to claim 1, characterized in that, In S1, the Fisher particle sizes of the tungsten carbide, cobalt powder, molybdenum carbide, and chromium carbide are 27μm~35μm, 1.0μm~1.5μm, 1.5μm~2.5μm, and <1μm, respectively.

3. The method for preparing an ultra-coarse-grained high-toughness cemented carbide according to claim 1, characterized in that, In S2, the dry grinding time is 30 min to 120 min, the grinding medium for dry grinding is a tungsten cobalt alloy grinding rod, the diameter of the grinding medium is 10 mm to 13 mm, and the mass of the grinding medium is 1.8 times to 3.5 times the total mass of the raw material.

4. The method for preparing an ultra-coarse-grained high-toughness cemented carbide according to claim 1, characterized in that, In S3, the wet milling time is 5h~15h, the amount of alcohol added is 180mL / kg~350mL / kg of raw material, and the amount of paraffin added is 2%~2.2% of the total mass of raw material.

5. The method for preparing an ultra-coarse-grained high-toughness cemented carbide according to claim 1, characterized in that, In S4, the sintering temperature is 1430℃~1500℃, and the sintering time is 2h~3h.

6. A coarse-grained, high-toughness cemented carbide, characterized in that, It is prepared by the preparation method of an ultra-coarse-grained high-toughness cemented carbide according to any one of claims 1-5.

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