High-performance hard alloy ball tooth and preparation method thereof

Abstract

The invention discloses a high-performance hard alloy ball tooth and a preparation method thereof, and belongs to the technical field of hard alloy materials. The method comprises the following steps: firstly, respectively preparing a superfine WC-Co spray material and an ultra-coarse WC-Co spray material, then mixing the two spray materials according to a mass ratio of (1.5-2.5): (7.5-8.5) to obtain composite powder, and finally, carrying out compression molding and sintering to obtain the hard alloy ball tooth. According to the invention, through the mixing design of the double-granularity spraying materials, the ultrafine WC grains are coated and grown on the surfaces of the coarse and large WC grains by utilizing the dissolution-precipitation effect of the ultrafine WC grains in a cobalt phase in the sintering process, and finally a metallographic structure with round and full grain morphology and strong binding force is formed. The problem that impact toughness and wear resistance of a traditional hard alloy button cannot be considered at the same time due to sharp edges and corners of WC crystal grains and poor binding force is effectively solved, and the prepared button has high hardness and high toughness at the same time and is particularly suitable for underground mine down-the-hole drilling operation under complex geological conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cemented carbide material, in particular to a high-performance cemented carbide ball tooth and a preparation method thereof. BACKGROUND

[0002] The cemented carbide ball tooth is a key component of a down-the-hole drill, and its performance directly determines the service life and mining efficiency of the drill. In the complex and changeable underground mine geological environment, the rock is soft and hard at different times, which puts high requirements on the comprehensive performance of the cemented carbide ball tooth. The traditional cemented carbide ball tooth is usually prepared by mixing tungsten carbide (WC) raw material with a single particle size and cobalt (Co) powder, and then through wet grinding, spray drying, pressing forming and sintering processes.

[0003] The cemented carbide prepared by this traditional method has the following inherent defects: first, the WC grain size distribution in the metallographic structure is uneven, and the grain outline is clear and sharp. Second, when cobalt, as the binder phase, is combined with these sharp WC grains, the binding force is insufficient, and there are micro stress concentration points. When the ball tooth impacts hard rock, if the hardness of the alloy is simply increased to improve wear resistance, the impact toughness will decrease significantly, leading to brittle fracture of the ball tooth; if the toughness is ensured, the wear resistance is insufficient, and the ball tooth will quickly wear in hard rock. The fundamental failure mechanism is that when the external mechanical force impacts, the stress starts to spread from the sharp grain corners, the binding force between the WC grains is poor, leading to rapid failure and fragmentation of the material, thereby greatly shortening the service life of the drill. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art and provide a high-performance cemented carbide ball tooth and a preparation method thereof. The method adjusts the morphology and distribution of WC grains through special powder design and sintering process, obtains a metallographic structure with round WC grains and strong binding force, and thus significantly improves the impact toughness and wear resistance of the ball tooth.

[0005] The present application provides a preparation method of a high-performance cemented carbide ball tooth, comprising the following steps:

[0006] S1, preparing ultra-fine spray material: mixing WC powder with an average particle size of 0.4-0.8 microns and Co powder with an average particle size of 0.6-1.0 microns in a mass ratio of (92-94):(6-8), adding a forming agent and a wet grinding medium, and preparing ultra-fine spray material by wet grinding and spray drying;

[0007] S2, preparing ultra-coarse spray material: mixing WC powder with an average particle size of 4.0-7.0 microns and Co powder with an average particle size of 0.6-1.0 microns in a mass ratio of (92-94):(6-8), adding a forming agent and a wet grinding medium, and preparing ultra-coarse spray material by wet grinding and spray drying;

[0008] S3, mixing: the superfine spray material prepared in step S1 and the super coarse spray material prepared in step S2 are mixed in a mass ratio (1.5-2.5):(7.5-8.5) to obtain a composite powder;

[0009] S4, pressing and sintering: the composite powder is pressed and sintered in a vacuum environment to obtain the hard alloy ball tooth.

[0010] Further, in step S1, the average particle size of the WC powder is 0.6 microns, and the average particle size of the Co powder is 0.8 microns; in step S2, the average particle size of the WC powder is 6 microns, and the average particle size of the Co powder is 0.8 microns.

[0011] Further, in steps S1 and S2, the forming agent is PEG4000, and the addition amount is 1.8-2.2% of the total mass of the WC and Co powders in the corresponding step.

[0012] Further, in steps S1 and S2, the wet grinding medium is anhydrous alcohol; in step S1, the solid-liquid mass ratio of anhydrous alcohol to solid raw material is 0.35-0.45, and in step S2, the solid-liquid mass ratio of anhydrous alcohol to solid raw material is 0.20-0.30.

[0013] Further, in step S1, the wet grinding time is 44-52 hours, and in step S2, the wet grinding time is 20-24 hours.

[0014] Further, in step S3, the mixing is carried out in a mixer, and the mixing time is 1 hour.

[0015] Further, in step S4, the final temperature of the sintering is 1350-1450°C.

[0016] The application also provides a high-performance hard alloy ball tooth prepared by the above method.

[0017] Further, the WC grain morphology in the metallographic structure of the high-performance hard alloy ball tooth is round, and the superfine WC grains are coated and grown on the surface of the super coarse WC grains through the dissolution-precipitation mechanism in the sintering process.

[0018] The application has the following advantages:

[0019] (1) By the "double particle size spray material mixing" process, the pre-prepared superfine and super coarse WC-Co spray dry materials are mixed in a specific ratio, which changes the traditional single particle size material system, creates a prerequisite for realizing the ideal "dissolution-precipitation" mechanism in the sintering process, and realizes the active design and accurate control of the final product metallographic structure.

[0020] (2) In the sintering process, the WC particles in the ultra-fine grain spray material are preferentially dissolved in the cobalt phase liquid phase due to their high surface activity, and then precipitate and grow on the surface of the undissolved, more stable ultra-coarse WC particles; this process is driven by the surface tension of the liquid phase cobalt, and the WC grains formed finally have a round shape and blunt corners, effectively eliminating the micro stress concentration points caused by sharp grain corners in the traditional process, greatly enhancing the binding force between the WC grains and between the WC grains and the cobalt phase, effectively passivating and dispersing external impact energy, thereby significantly improving the impact toughness and anti-fracture ability of the ball tooth;

[0021] (3) The present application constructs a composite structure with round coarse WC grains as the skeleton and strong and tough cobalt phase as the firm connection, which on the one hand ensures the high hardness and excellent wear resistance of the material through the coarse grain skeleton, and on the other hand, through the round grain morphology and enhanced phase boundary binding force, the material is endowed with extremely high impact toughness, so that the prepared ball tooth has both high hardness and high toughness, solving the technical bottleneck that the ball tooth is either not wear-resistant or easily broken when working in complex hard rock strata;

[0022] (4) The cemented carbide ball tooth of the present application has an ultra-long service life and stable working performance when used in downhole drilling, especially in hard rock or soft and hard alternating strata in underground mines. This effectively reduces the replacement frequency and downtime of the drill bit, not only improves the drilling efficiency, but also greatly reduces the comprehensive mining cost, and the economic benefit is significant. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of the micro-morphology of the ultra-coarse spray material prepared by the present application.

[0024] Figure 2 is a schematic diagram of the micro-morphology of the uniform composite powder formed after mixing the ultra-fine and ultra-coarse spray materials in the present application.

[0025] Figure 3 is a metallographic structure photo of the cemented carbide prepared by using the conventional single ultra-coarse particle spray material.

[0026] Figure 4 is a metallographic structure photo of the cemented carbide prepared by using the mixed composite spray material of the present application. DETAILED DESCRIPTION

[0027] The present application will be described in detail below in conjunction with the drawings and specific examples, but the scope of protection of the present application is not limited thereto.

[0028] Example 1

[0029] The present embodiment provides a preparation method of a high-performance cemented carbide ball tooth, and the specific steps are as follows:

[0030] S1, preparing ultra-fine spray material:

[0031] WC powder with average particle size of 0.6 microns (mass ratio 94%) and cobalt powder with average particle size of 0.8 microns (mass ratio 6%) were put into a 300L wet mill, and 2% of the total mass of the powder was added as a molding agent PEG4000 and wet milling medium anhydrous alcohol (purity 99%), and the solid-liquid mass ratio was controlled at 0.4. After ball milling for 48 hours, the material was unloaded, spray dried and granulated to prepare an ultra-fine spray material.

[0032] S2, preparing ultra-coarse spray material:

[0033] WC powder with average particle size of 6.0 microns (mass ratio 94%) and cobalt powder with average particle size of 0.8 microns (mass ratio 6%) were put into a 300L wet mill, and 2% of the total mass of the powder was added as a molding agent PEG4000 and wet milling medium anhydrous alcohol (purity 99%), and the solid-liquid mass ratio was controlled at 0.25. After ball milling for 22 hours, the material was unloaded, spray dried and granulated to prepare an ultra-coarse spray material, the micro-morphology of which is shown in Figure 1 .

[0034] S3, mixing:

[0035] The ultra-fine spray material prepared in step S1 and the ultra-coarse spray material prepared in step S2 were put into a 600L mixer in a mass ratio of 2:8, mixed for 1 hour, and the two materials were uniformly mixed to form a composite powder, the micro-morphology of which is shown in Figure 2 .

[0036] S4, pressing and sintering:

[0037] The composite powder was pressed into a ball tooth green body, and then sintered: first de-waxed under positive pressure, then vacuum sintering, partial pressure sintering and pressure sintering in sequence to obtain a hard alloy ball tooth.

[0038] During vacuum sintering of the composite powder, tungsten carbide and tungsten dissolved in the cobalt phase solid solution increased with increasing temperature, about 4% at 1000°, about 10% at 1340°, and about 35% at the final sintering temperature. The ultra-fine grain WC has strong activation energy, and the activated grain gradually dissolves in the liquid phase cobalt, and precipitates on the unsolved coarse grain WC, causing WC grain recrystallization and growth. The grown grain is round in shape due to surface tension, and the binding force between WC grains is enhanced, thereby prolonging the material failure time.

[0039] Comparative Example

[0040] The traditional single particle size method is used to prepare the hard alloy ball tooth: WC powder with an average particle size of 6.0 microns (94% by mass) and cobalt powder with an average particle size of 0.8 microns (6% by mass) are put into a wet mill, 2% of the total mass of the powder is added as a molding agent PEG4000 and an appropriate amount of anhydrous alcohol, and after ball milling, spray drying and pressing, the same sintering process conditions as in Example 1 are used for sintering to obtain the traditional hard alloy ball tooth.

[0041] Figure 3 The metallographic structure of the hard alloy obtained in Comparative Example 1 is shown in the figure. As can be seen from the figure, the WC grain outline is clear, the corners are sharp, the grain size distribution is uneven, and the cobalt phase filling bonding state has obvious stress concentration points.

[0042] Figure 4 The metallographic structure of the hard alloy obtained in Example 1 is shown in the figure. As can be seen from the figure, through the special process of the application, the WC grain morphology has changed significantly, the grain outline is round and full, the surface of the coarse WC grain is covered and grown by the dissolved-out WC phase, the grains are tightly bonded, the cobalt phase is uniformly distributed, and the micro stress concentration points are effectively eliminated.

[0043] The performance test results of the two kinds of hard alloy ball teeth show that the hard alloy ball tooth prepared in Example 1 has significantly improved impact toughness while maintaining high hardness. Compared with the ball tooth prepared by the traditional method, the service life is increased by about 30% under the same underground mine downhole drilling operation conditions, especially in the complex rock stratum with alternating soft and hard, showing excellent impact resistance and wear resistance.

[0044] The above is only an example and description of the structure of the application, and those skilled in the art can make various modifications or supplements or use similar methods to replace the described specific embodiments, as long as they do not deviate from the concept of the application, which should belong to the protection scope of the application.

Claims

1. A method for preparing high-performance cemented carbide ball teeth, characterized in that, Includes the following steps: S1. Preparation of ultrafine spray material: WC powder with an average particle size of 0.4 to 0.8 micrometers and Co powder with an average particle size of 0.6 to 1.0 micrometers are mixed at a mass ratio of (92 to 94): (6 to 8), a molding agent and a wet grinding medium are added, and the mixture is wet-milled and spray-dried to obtain ultrafine spray material; S2. Preparation of ultra-coarse spray material: WC powder with an average particle size of 4.0 to 7.0 micrometers and Co powder with an average particle size of 0.6 to 1.0 micrometers are mixed at a mass ratio of (92 to 94): (6 to 8), a molding agent and a wet grinding medium are added, and ultra-coarse spray material is obtained by wet grinding and spray drying. S3. Mixing: The ultrafine spray material obtained in step S1 and the ultracoarse spray material obtained in step S2 are mixed at a mass ratio of (1.5~2.5):(7.5~8.5) to obtain composite powder; S4. Pressing and Sintering: After pressing the composite powder into shape, sintering is carried out in a vacuum environment to obtain the cemented carbide ball teeth.

2. The method for preparing a high-performance cemented carbide ball tooth according to claim 1, characterized in that, In step S1, the average particle size of WC powder is 0.6 micrometers and the average particle size of Co powder is 0.8 micrometers; in step S2, the average particle size of WC powder is 6 micrometers and the average particle size of Co powder is 0.8 micrometers.

3. The method for preparing a high-performance cemented carbide ball tooth according to claim 1, characterized in that, In steps S1 and S2, the molding agent is PEG4000, and its addition amount is 1.8 to 2.2% of the total mass of WC and Co powder in the corresponding steps.

4. The method for preparing a high-performance cemented carbide ball tooth according to claim 1, characterized in that, In steps S1 and S2, the wet grinding medium is anhydrous alcohol; in step S1, the solid-liquid mass ratio of anhydrous alcohol to solid raw material is 0.35 to 0.45, and in step S2, the solid-liquid mass ratio of anhydrous alcohol to solid raw material is 0.20 to 0.

30.

5. The method for preparing a high-performance cemented carbide ball tooth according to claim 4, characterized in that, The wet grinding time in step S1 is 44 to 52 hours, and the wet grinding time in step S2 is 20 to 24 hours.

6. The method for preparing a high-performance cemented carbide ball tooth according to claim 1, characterized in that, In step S3, the mixing is carried out in a mixer for 1 hour.

7. The method for preparing a high-performance cemented carbide ball tooth according to claim 1, characterized in that, In step S4, the final sintering temperature is 1350℃~1450℃.

8. A high-performance cemented carbide ball tooth prepared by any one of claims 1 to 7.

9. The high-performance cemented carbide ball tooth according to claim 8, characterized in that, The WC grains in its metallographic structure have rounded morphology, and the ultrafine WC grains are coated and grown on the surface of the ultracoarse WC grains through the dissolution-precipitation mechanism during the sintering process.

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