A rare earth coarse-grained hard alloy and preparation method thereof

Abstract

The invention belongs to the technical field of powder metallurgy, and specifically relates to a rare earth coarse-grained hard alloy and a preparation method thereof. By adding an excessive amount of C, the progress of carbonization is accelerated, the rate and efficiency of carbonization are improved, and the contents of W2C and W phases are reduced. By adding trace Y and Co elements during carbon matching, the Y element is dispersed twice by carbon matching mixing and ball milling of the mixture, which greatly improves the uniformity of the Y element, and the addition of the Co element promotes the growth of WC grains during the carbonization process. WO3 is used to consume excessive free carbon, and the amount of powder added can be greatly reduced compared with the method of using W powder to match free carbon, and WO3 is easy to disperse, which reduces the occurrence of fine grain aggregation, and at the same time strengthens the Co phase, and comprehensively solves the problem of short service life of coarse-grained hard alloy.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy, and specifically relates to a rare earth coarse-grained hard alloy and a preparation method thereof. Background Art

[0002] Cemented carbide is a metal-ceramic composite material made of refractory metal hard compounds as a hard matrix and transition metals as a tough bonding phase through powder metallurgy. Due to the high strength and high toughness of cemented carbide, it has been widely used in oil and gas drilling, geological exploration, mining, rollers, mold materials, cutting tools, wear-resistant parts and other fields, playing a pivotal role in promoting national industrial manufacturing and national economic development.

[0003] Coarse-grained cemented carbide is widely used in mining, especially in drilling, tunneling, road milling tools, and rollers, because of its good thermal conductivity, impact resistance, and fatigue resistance. In production, coarse-grained WC powder is difficult to carbonize due to its large particles. The core of the WC particles is uncarbonized W powder, and the middle is incompletely carbonized W powder. 2 C phase and WC phase on the outside, resulting in a short service life of the product. In addition to changing the performance of WC, in order to improve the performance of cemented carbide products, scientific researchers have made a lot of attempts, such as improving the uniformity of cemented carbide structure, adding alloying elements, surface coating, strengthening treatment and other measures, which have improved the strength and hardness of cemented carbide to a certain extent, but still have not achieved a qualitative breakthrough. At the same time, people have also begun to explore and study rare earth cemented carbide. Studies have shown that the addition of rare earth oxides can refine WC grains, eliminate discontinuously grown coarse grains, increase the content of cubic cobalt phase, and increase the toughness of cemented carbide, which to a certain extent provides new research ideas for the development of cemented carbide. However, in the existing process, it is difficult to uniformly dope rare earth elements, and the coarse-grained WC powder is not completely carbonized and needs to be supplemented with tungsten. The large amount of tungsten supplementation leads to the aggregation and abnormal growth of alloy fine grains, which affects the service life of coarse-grained cemented carbide. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a rare earth coarse-grained cemented carbide and a preparation method thereof.

[0005] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions:

[0006] A method for preparing rare earth coarse-grained cemented carbide, wherein the WC grain size of the cemented carbide is 8.0 to 10.0 μm, comprising the following steps:

[0007] S1. Preparation of coarse-grained WC powder

[0008] Take W powder and C powder, wherein the C powder accounts for 6.50-6.80wt% of the total mass of W+C, take an yttrium source that can provide 0.7-1.0wt% of the Y element that accounts for the total mass of W+C, and take a cobalt source that can provide 0.9-1.2wt% of the Co element that accounts for the total mass of W+C, mix the W powder, C powder, yttrium source, and cobalt source uniformly, and then carbonize to obtain carburized WC;

[0009] S2.Ball milling

[0010] The carbonized WC is crushed by ball milling and then sieved to obtain WC powder;

[0011] S3. Mixture preparation

[0012] Analysis of free carbon content C in WC powder f According to WO 3 and C f The mass ratio of WO is (83.5~85.5):(14.5~16.5) 3 Powder, and according to the composition of WC-Co cemented carbide, WC powder and Co powder are taken and mixed with WO 3 The powders are used as raw material powders and the mixture is obtained after ball milling;

[0013] S4. Alloy sintering

[0014] The green compact formed by pressing the mixed material is placed in a sintering furnace for hot pressing and sintering, and after sintering, the green compact is cooled in the furnace to obtain a rare earth coarse-grained cemented carbide.

[0015] As a preferred embodiment of the method for preparing a rare earth coarse-grained cemented carbide according to the present invention, in step S1, the carbonization is carried out in a medium frequency furnace.

[0016] As a preferred embodiment of the method for preparing a rare earth coarse-grained cemented carbide according to the present invention, in step S1, the yttrium source is yttrium acetate, and the cobalt source is cobalt acetate.

[0017] As a preferred embodiment of the method for preparing a rare earth coarse-grained cemented carbide according to the present invention, wherein: in the step S1, the carbonization temperature is 2100-2300° C., and the carbonization time is 5-15 hours;

[0018] As a preferred embodiment of the method for preparing rare earth coarse-grained cemented carbide described in the present invention, wherein: in the step S2, a sieve with a mesh size of 80 to 100 is used for screening.

[0019] As a preferred embodiment of the method for preparing rare earth coarse-grained cemented carbide described in the present invention, in step S3, the raw material powder, the forming agent and the surfactant are placed in an alcohol medium for ball milling.

[0020] As a preferred embodiment of the method for preparing a rare earth coarse-grained cemented carbide according to the present invention, in the step S3, spray granulation is performed after ball milling to obtain a mixture.

[0021] As a preferred embodiment of the method for preparing a rare earth coarse-grained cemented carbide described in the present invention, in step S4, the sintering process is as follows: the sintering temperature is 1450-1520°C, the pressure is 8-10 MPa, and the holding time is 0.5-2.0 h.

[0022] As a preferred embodiment of the method for preparing a rare earth coarse-grained cemented carbide according to the present invention, in step S4, sintering is performed in a hydrogen atmosphere.

[0023] To solve the above technical problem, according to another aspect of the present invention, the present invention provides the following technical solution:

[0024] A rare earth coarse-grained hard alloy is prepared by adopting the preparation method.

[0025] As a preferred embodiment of the rare earth coarse-grained cemented carbide described in the present invention, the WC grain size of the cemented carbide is 8.0-10.0 μm.

[0026] The beneficial effects of the present invention are as follows:

[0027] The present invention provides a rare earth coarse-grained cemented carbide and a preparation method thereof, so that the rare earth elements are evenly distributed through secondary mixing, the carbonization degree of ultra-coarse WC powder is improved by high carbon content, and WO is used to prepare the rare earth elements. 3 Replacing W powder solves the problem of excessive tungsten supplementation causing fine grain aggregation and abnormal growth of the alloy, and comprehensively solves the problem of short service life of coarse-grained cemented carbide. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0029] Figure 1 This is a picture of WC powder after ball milling and sieving in Example 1 of the present invention;

[0030] Figure 2 This is a picture of cemented carbide A prepared in Example 1 of the present invention;

[0031] Figure 3 This is a picture of WC powder after ball milling and sieving in Comparative Example 1 of the present invention;

[0032] Figure 4 This is a picture of cemented carbide D prepared in Comparative Example 1 of the present invention;

[0033] Figure 5 This is a picture of cemented carbide E prepared in Comparative Example 2 of the present invention;

[0034] Figure 6 This is a picture of cemented carbide F prepared in Comparative Example 3 of the present invention;

[0035] Figure 7 This is a picture of cemented carbide G prepared in comparative example 4 of the present invention. DETAILED DESCRIPTION

[0036] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The main purpose of the present invention is to provide a rare earth coarse-grained cemented carbide and a preparation method thereof, which accelerates the carbonization process by adding excessive C, improves the carbonization rate and efficiency, and reduces W 2 The content of C and W phases; by adding trace Y and Co elements during carbonization, the uniformity of Y element is greatly improved after carbonization mixing and ball milling of the mixture. The addition of Co element promotes the growth of WC grains during the carbonization process; using WO 3 Consuming excess free carbon can greatly reduce the amount of powder added compared to using W powder to match free carbon, and WO 3 It is easy to disperse, reduces the occurrence of fine grain aggregation, and strengthens the Co phase.

[0038] According to one aspect of the present invention, the present invention provides the following technical solution:

[0039] A method for preparing rare earth coarse-grained cemented carbide, wherein the WC grain size of the cemented carbide is 8.0 to 10.0 μm, comprising the following steps:

[0040] S1. Preparation of coarse-grained WC powder

[0041] Take W powder and C powder, wherein the C powder accounts for 6.50-6.80wt% of the total mass of W+C, take an yttrium source that can provide 0.7-1.0wt% of the Y element that accounts for the total mass of W+C, and take a cobalt source that can provide 0.9-1.2wt% of the Co element that accounts for the total mass of W+C, mix the W powder, C powder, yttrium source, and cobalt source uniformly, and then carbonize to obtain carburized WC;

[0042] S2.Ball milling

[0043] The carbonized WC is crushed by ball milling and then sieved to obtain WC powder;

[0044] S3. Mixture preparation

[0045] Analysis of free carbon content C in WC powder f According to WO 3 and C f The mass ratio of WO is (83.5~85.5):(14.5~16.5) 3 Powder, and according to the composition of WC-Co cemented carbide, WC powder and Co powder are taken and mixed with WO 3 The powders are used as raw material powders and the mixture is obtained after ball milling;

[0046] S4. Alloy sintering

[0047] The green compact formed by pressing the mixed material is placed in a sintering furnace for hot pressing and sintering, and after sintering, the green compact is cooled in the furnace to obtain a rare earth coarse-grained cemented carbide.

[0048] Preferably, in step S1, carbonization is carried out in a medium frequency furnace; the yttrium source is yttrium acetate, and the cobalt source is cobalt acetate; the carbonization temperature is 2100-2300°C, and the carbonization time is 5-15h; specifically, the proportion of C powder to the total mass of W+C can be, for example but not limited to, any one of 6.50wt%, 6.55wt%, 6.60wt%, 6.65wt%, 6.70wt%, 6.75wt%, 6.80wt% or a range between any two of them; the proportion of Y element to the total mass of W+C can be, for example but not limited to, 0.7wt%, 0.75wt%, 0.8wt%, 0.85wt%, 0.9wt%, 0.95wt%, 1.0wt% or more. any one of or the range between any two of; the proportion of Co element to the total mass of W+C can be, for example but not limited to, any one of 0.9wt%, 0.95wt%, 1.0wt%, 1.05wt%, 1.1wt%, 1.15wt%, 1.2wt% or the range between any two; the carbonization temperature can be, for example but not limited to, any one of 2100°C, 2150°C, 2200°C, 2250°C, 2300°C or the range between any two; the carbonization time can be, for example but not limited to, any one of 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or the range between any two;

[0049] Preferably, in step S2, 80-100 mesh sieve is used for sieving.

[0050] Preferably, in step S3, the raw material powder, the forming agent, and the surfactant are placed in an alcohol medium for ball milling, and then spray granulation is performed after ball milling to obtain a mixed material. 3 and C f The mass ratio may be, for example but not limited to, any one of 83.5:16.5, 84:16, 84.5:15.5, 85:15, 85.5:14.5 or a range between any two thereof;

[0051] Preferably, in step S4, the sintering process is: sintering temperature is 1450-1520°C, pressure is 8-10MPa, and holding time is 0.5-2.0h; sintering is carried out in a hydrogen atmosphere. Specifically, the sintering temperature can be, for example but not limited to, any one of 1450°C, 1460°C, 1470°C, 1480°C, 1490°C, 1500°C, 1510°C, 1520°C, or a range between any two of them; the pressure can be, for example but not limited to, any one of 8MPa, 8.5MPa, 9MPa, 9.5MPa, 10MPa, or a range between any two of them; the holding time can be, for example but not limited to, any one of 0.5h, 1.0h, 1.5h, 2.0h, or a range between any two of them;

[0052] According to another aspect of the present invention, the present invention provides the following technical solution:

[0053] A rare earth coarse-grained cemented carbide is prepared by the above preparation method, wherein the WC grain size of the cemented carbide is 8.0-10.0 μm. Preferably, the WC grain size of the cemented carbide is 8.5-10.0 μm; further preferably, the WC grain size of the cemented carbide is 9.0-10.0 μm.

[0054] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0055] Example 1

[0056] A method for preparing rare earth coarse-grained cemented carbide comprises the following steps:

[0057] S1. Preparation of coarse-grained WC powder

[0058] Take W powder and C powder, wherein the C powder accounts for 6.80wt% of the total mass of W+C, take yttrium acetate that can provide 0.8wt% of the Y element that accounts for the total mass of W+C, and take cobalt acetate that can provide 1.0wt% of the Co element that accounts for the total mass of W+C, mix the W powder, C powder, yttrium source, and cobalt source evenly, and then place them in a medium frequency furnace for carbonization to obtain carbonized WC; the carbonization temperature is 2300°C, and the carbonization time is 10h;

[0059] S2.Ball milling

[0060] The carbonized WC is crushed by ball milling and then sieved through 80 mesh to obtain WC powder. Figure 1 As shown in the figure, WC has a coarse particle size and is completely carbonized, without any W or W inside. 2 Phase C;

[0061] S3. Mixture preparation

[0062] Analysis of free carbon content C in WC powder f 0.52wt%, according to WO 3 and C f Prepare WO with a mass ratio of 83.5:16.5 3 Powder, and take WC powder and Co powder according to the composition of YG8 cemented carbide, and mix with WO 3 The raw powder, the forming agent and the surfactant are placed in an alcohol medium for ball milling, and then spray granulation is performed after ball milling to obtain a mixed material;

[0063] S4. Alloy sintering

[0064] The green compact formed by pressing the mixture is placed in a sintering furnace for hot pressing sintering. The sintering process is as follows: sintering temperature is 1520°C, pressure is 8MPa, holding time is 1.0h, and sintering is carried out in a hydrogen atmosphere. After sintering, the green compact is cooled in the furnace to obtain a rare earth coarse-grained cemented carbide A such as Figure 2 As shown, the sample has high density, coarse WC grains, an average grain size of 8.0-10.0 μm, and a uniform organizational structure.

[0065] Example 2

[0066] A method for preparing rare earth coarse-grained cemented carbide comprises the following steps:

[0067] S1. Preparation of coarse-grained WC powder

[0068] Take W powder and C powder, wherein the C powder accounts for 6.50wt% of the total mass of W+C, take yttrium acetate that can provide 0.7wt% of the Y element that accounts for the total mass of W+C, and take cobalt acetate that can provide 1.2wt% of the Co element that accounts for the total mass of W+C, mix the W powder, C powder, yttrium source, and cobalt source evenly, and then place them in a medium frequency furnace for carbonization to obtain carbonized WC; the carbonization temperature is 2100°C, and the carbonization time is 15h;

[0069] S2.Ball milling

[0070] The carbonized WC is crushed by ball milling and then sieved through a 100-mesh sieve to obtain WC powder;

[0071] S3. Mixture preparation

[0072] Analysis of free carbon content C in WC powder f 0.49wt%, according to WO3 and C f Prepare WO with a mass ratio of 85.5:13.5 3 Powder, and take WC powder and Co powder according to the composition of YG8 cemented carbide, and mix with WO 3 The raw powder, the forming agent and the surfactant are placed in an alcohol medium for ball milling, and then spray granulation is performed after ball milling to obtain a mixed material;

[0073] S4. Alloy sintering

[0074] The pressed green sheet formed by the mixture is placed in a sintering furnace for hot pressing sintering. The sintering process is as follows: sintering temperature is 1450°C, pressure is 10MPa, holding time is 2.0h, and sintering is carried out in a hydrogen atmosphere. After sintering, the green sheet is cooled in the furnace to obtain rare earth coarse-grained cemented carbide B. The sample has high density, coarse WC grains, an average grain size of 8.0-10.0μm, and a uniform organizational structure.

[0075] Example 3

[0076] A method for preparing rare earth coarse-grained cemented carbide comprises the following steps:

[0077] S1. Preparation of coarse-grained WC powder

[0078] Take W powder and C powder, wherein the C powder accounts for 6.65wt% of the total mass of W+C, take yttrium acetate that can provide 1.0wt% of the Y element that accounts for the total mass of W+C, and take cobalt acetate that can provide 0.9wt% of the Co element that accounts for the total mass of W+C, mix the W powder, C powder, yttrium source, and cobalt source evenly, and then place them in a medium frequency furnace for carbonization to obtain carbonized WC; the carbonization temperature is 2200°C, and the carbonization time is 5h;

[0079] S2.Ball milling

[0080] The carbonized WC was crushed by ball milling and then sieved through 80 mesh to obtain WC powder;

[0081] S3. Mixture preparation

[0082] Analysis of free carbon content C in WC powder f 0.53wt%, according to WO 3 and C f Prepare WO with a mass ratio of 84.5:15.5 3 Powder, and take WC powder and Co powder according to the composition of YG8 cemented carbide, and mix with WO 3 The raw powder, the forming agent and the surfactant are placed in an alcohol medium for ball milling, and then spray granulation is performed after ball milling to obtain a mixed material;

[0083] S4. Alloy sintering

[0084] The pressed green sheet formed by the mixture is placed in a sintering furnace for hot pressing sintering. The sintering process is as follows: the sintering temperature is 1490°C, the pressure is 10MPa, the holding time is 0.5h, and the sintering is carried out in a hydrogen atmosphere. After sintering, the green sheet is cooled with the furnace to obtain rare earth coarse-grained cemented carbide C. The sample has high density, coarse WC grains, an average grain size of 8.0-10.0μm, and a uniform organizational structure.

[0085] Comparative Example 1

[0086] The difference from Example 1 is that

[0087] In step S1, C powder accounts for 6.13wt% of the total mass of W+C.

[0088] The carbonized WC is crushed by ball milling and then sieved through 80 mesh to obtain WC powder. Figure 3 As shown in the figure, the WC particle core has obvious W or W due to incomplete carbonization. 2 C phase, and there are defects; the hard alloy D is obtained as Figure 4 As shown, the sample has high density, the average grain size of WC grains reaches 6.0-7.5 μm, and the organizational structure is uniform.

[0089] Comparative Example 2

[0090] The difference from Example 1 is that

[0091] In step S1, the carbonization temperature is 1800°C.

[0092] Get carbide E as Figure 5 As shown, the sample has high density, the average grain size of WC grains reaches 5.0-7.0 μm, and the organizational structure is uniform.

[0093] Comparative Example 3

[0094] The difference from Example 1 is that

[0095] In step S1, the Y element is added in the form of yttrium sulfate.

[0096] Get carbide F as Figure 6 As shown, the sample has type A pores, the average grain size of WC grains reaches 8.0-10.0 μm, and the organizational structure is uniform.

[0097] Comparative Example 4

[0098] The difference from Example 1 is that

[0099] In step S1, yttrium acetate and cobalt acetate are not added.

[0100] Get carbide G as Figure 7As shown, the WC grains in this sample grew abnormally, with the average grain size of WC grains reaching 6.0-7.5 μm, and individual grains reaching 20-25 μm.

[0101] Comparative Example 5

[0102] The difference from Example 1 is that

[0103] In step S3, the free carbon content in WC powder is not analyzed. 3 Powder was changed to W powder;

[0104] The obtained cemented carbide H has fine grain aggregation and abnormal growth of WC grains. The average grain size of WC grains reaches 8.0-10.0 μm, and some grains reach 30-35 μm.

[0105] Comparative Example 6

[0106] The difference from Example 1 is that

[0107] In step S4, the sintering temperature is 1410°C.

[0108] The obtained cemented carbide I has good density, uniform structure and an average grain size of WC grains reaching 6-7 μm.

[0109] Example 1, Example 3, Comparative Example 3, Comparative Example 5, prepared samples A, C, F, H and commercially available YG8 samples were installed on the 813A excavation trolley for excavation experiments. Nine samples were installed in each experiment, and 30 consecutive holes were drilled in the tungsten mine, each with a depth of 3.6 meters. The test results are as follows:

[0110] sample Test Results A All 9 samples can continue to be used normally, with the maximum wear height of 1.38mm. C All 9 samples can continue to be used normally, with the maximum wear height of 1.46mm. F Three were cracked, and six could continue to be used normally. The maximum wear height of the usable samples was 3.12 mm. H 4 were cracked, 5 could continue to be used normally, and the maximum wear height of the usable samples was 4.50 mm. YG8 3 were cracked, 2 were severely worn, 4 could continue to be used, and the maximum wear height of the usable samples was 4.84mm.

[0111] The present invention accelerates the carbonization process by adding excessive C, thereby increasing the carbonization rate and efficiency and reducing W 2 The content of C and W phases; by adding trace Y and Co elements during carbonization, the uniformity of Y element is greatly improved after carbonization mixing and ball milling of the mixture. The addition of Co element promotes the growth of WC grains during the carbonization process; using WO 3 Consuming excess free carbon can greatly reduce the amount of powder added compared to using W powder to match free carbon, and WO 3 It is easy to disperse, reducing the occurrence of fine grain aggregation, while strengthening the Co phase, comprehensively solving the problem of short service life of coarse-grained cemented carbide.

[0112] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing rare earth coarse-grained cemented carbide, characterized in that: The WC grain size of the cemented carbide is 8.0-10.0 μm, comprising the following steps: S1. Preparation of coarse-grained WC powder Take W powder and C powder, wherein the C powder accounts for 6.50-6.80wt% of the total mass of W+C, take a yttrium source that can provide 0.7-1.0wt% of the Y element that accounts for the total mass of W+C, and take a cobalt source that can provide 0.9-1.2wt% of the Co element that accounts for the total mass of W+C, mix the W powder, C powder, yttrium source and cobalt source evenly, and then carbonize them to obtain carbonized WC; the yttrium source is yttrium acetate, and the cobalt source is cobalt acetate; the carbonization temperature is 2100-2300°C, and the carbonization time is 5-15h; S2.Ball milling The carbonized WC is crushed by ball milling and then sieved to obtain WC powder; S3. Mixture preparation Analysis of free carbon content C in WC powder f , according to WO3 and C f The mass ratio of WC-Co cemented carbide is (83.5-85.5): (14.5-16.5) to prepare WO3 powder, and take WC powder and Co powder according to the composition of WC-Co cemented carbide, and use them together with WO3 powder as raw material powder, and obtain a mixture after ball milling; S4. Alloy sintering The green compact formed by pressing the mixture is placed in a sintering furnace for hot pressing sintering. The sintering process is as follows: the sintering temperature is 1450-1520°C, the pressure is 8-10MPa, the holding time is 0.5-2.0h, and the sintering is carried out in a hydrogen atmosphere; after sintering, the green compact is cooled in the furnace to obtain a rare earth coarse-grained cemented carbide.

2. The method for preparing rare earth coarse-grained cemented carbide according to claim 1, characterized in that: In the step S1, carbonization is performed in a medium frequency furnace.

3. The method for preparing rare earth coarse-grained cemented carbide according to claim 1, characterized in that: In step S2, 80-100 mesh sieve is used for sieving.

4. The method for preparing rare earth coarse-grained cemented carbide according to claim 1, characterized in that: In the step S3, the raw material powder, the forming agent and the surfactant are placed in an alcohol medium for ball milling.

5. The method for preparing rare earth coarse-grained cemented carbide according to claim 1, characterized in that: In the step S3, spray granulation is performed after ball milling to obtain a mixed material.

6. A rare earth coarse-grained cemented carbide prepared by the preparation method according to any one of claims 1 to 5, wherein the WC grain size of the cemented carbide is 8.0-10.0 μm.

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