TiWC2 reinforced YT15 hard alloy and preparation method thereof

Abstract

The invention discloses a TiWC2 reinforced YT15 hard alloy and a preparation method thereof, and relates to the technical field of hard alloy preparation, the method comprises the following steps: TiC powder, WC powder and carbon black powder as raw materials are sintered, crushed and ball-milled in a nitrogen atmosphere, then WC powder, Co powder, TiC powder and carbon black as raw materials are ball-milled and mixed, the two materials are mixed, and the TiWC2 reinforced YT15 hard alloy is obtained. The preparation method comprises the following steps: adding absolute ethyl alcohol and paraffin as process control agents, drying, carrying out compression molding, sintering in a pressure sintering furnace, and forming TiWC2 and (Ti (C, N)) phases in the YT15 hard alloy in the sintering process to obtain the TiWC2 reinforced YT15 hard alloy. According to the YT15 hard alloy prepared through the method, the hardness, the fracture toughness, the density, the thermal stability and the machining performance of the YT15 hard alloy are remarkably improved, and therefore the comprehensive performance of the YT15 hard alloy is optimized.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, specifically to a TiWC2-reinforced YT15 cemented carbide and its preparation method. Background Technology

[0002] YT15, a tungsten-titanium-cobalt cemented carbide (WC-TiC-Co), contains 15% titanium carbide, exhibiting high hardness (≥91 HRA) and excellent wear resistance. It is suitable for semi-finishing and finishing of carbon steel and alloy steel, performing particularly well in continuous cutting scenarios. Compared to YG-type cemented carbides, the addition of titanium carbide in YT15 reduces its affinity with steel during high-speed cutting, decreasing built-up edge formation and thus improving surface finish. However, YT15 is relatively brittle and has poor impact resistance, making it unsuitable for interrupted cutting or high-impact load conditions (such as casting machining). Furthermore, its high-temperature resistance is limited; it is prone to oxidation and softening at high temperatures, leading to shortened tool life.

[0003] TiWC2 possesses both metallic and ceramic properties, such as high hardness (HRA 88 and above), high wear resistance, corrosion resistance, and high temperature resistance. It also exhibits self-lubricating properties, has a relatively low density (approximately one-third that of carbide systems), and is easy to process and shape, making it suitable for high-temperature protective coatings, nuclear sealing components, and other fields. However, current TiWC2 synthesis is limited by existing preparation techniques, requiring a large amount of raw materials and involving complex processes. Furthermore, the synthesis process easily generates impurity phases (such as TiC), and the resulting alloys cannot be well integrated with cemented carbides. Therefore, composite processing is necessary to improve its performance.

[0004] Due to the contradiction between the high wear resistance of YT15 cemented carbide and its insufficient brittleness and temperature resistance, the above problems can be partially solved by introducing a TiWC2 reinforcing phase. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a TiWC2-reinforced YT15 cemented carbide and its preparation method. By uniformly generating TiWC2 inside the YT15 cemented carbide and filling it with nitrogen gas, titanium carbonitride (Ti(C,N)) is generated. The TiWC2 and the introduced nitrogen gas are introduced into the YT15 cemented carbide system as composite reinforcing phases to play a role in interface strengthening. The layered structure of TiWC2 can alleviate stress concentration and improve the fracture toughness of the cemented carbide.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: A method for preparing TiWC2-reinforced YT15 cemented carbide, the method being completed according to the following steps: S1. Take equimolar amounts of cemented carbide TiC powder, WC powder, and carbon black powder, mix and ball-mill them under vacuum, then sinter them in a sintering furnace and fill them with nitrogen gas, the volume of which accounts for 10%-20% of the sintering furnace; then crush them with an airflow crusher and ball-mill them into powder again. S2, Weigh WC powder, Co powder and TiC powder and add them to a ball mill jar for ball milling and mixing. Add carbon black powder during the ball milling process to adjust the carbon content in the raw materials. S3, by mass percentage, takes 4.2~5.4 wt% of the powder obtained in S1 and 94.6~95.8 wt% of the mixed powder obtained in S2, adds them to a ball mill jar for ball milling and mixing, and adds 1.8~2.4 wt% of anhydrous ethanol and paraffin as process control agents, with the mass ratio of anhydrous ethanol to paraffin being 1:1; S4, spray dry the mixed powder obtained in S3 to obtain the mixed powder; S5. The dried mixed powder is pressed into shape and sintered in a pressure sintering furnace at a sintering temperature of 1550~1650℃ for 2~3h. TiWC2 is synthesized through the alloy composite reaction during the sintering process, and TiWC2-reinforced YT15 cemented carbide is obtained.

[0007] Preferably, the particle size of TiC powder and WC powder in S1 is 3μm~44μm, and the particle size of carbon black powder is 20μm~44μm.

[0008] Preferably, the sintering temperature in S1 is 2000-2200℃, and the sintering time is 2-3h.

[0009] Preferably, the process parameters for airflow crushing in S1 are: crushing pressure of 8-10 mbar and classifier wheel speed of 1000-1200 r / min.

[0010] Preferably, the particle size of the powder produced by ball milling again in step S1 is 20μm~30μm.

[0011] Preferably, in S2, the Fisher particle size of WC is 1.2μm~1.6μm, the particle size of Co is 1.6μm~2μm, and the particle size of TiC is 10μm~44μm.

[0012] Preferably, the mass ratio of WC powder, Co powder, and TiC powder in S2 is 80:6:14, and the mass ratio of carbon black powder to Co powder is (0.1-0.2):1.

[0013] Preferably, in S1, S2 and S3, the ball milling parameters are: the process is carried out in a vacuum environment, the ball milling speed is 200~300 rpm, and the ball milling time is 6~12h.

[0014] Preferably, the spray drying temperature in S4 is 200-300℃, and the spraying rate is 10-20m / s.

[0015] Another object of the present invention is to provide a TiWC2-reinforced YT15 cemented carbide, which is prepared by the above-described method for preparing TiWC2-reinforced YT15 cemented carbide.

[0016] The interactions between elements and the formation mechanism of TiWC2 in this invention are as follows: 1. Element interactions and reaction pathways During the sintering process, the TiC powder, WC powder, and carbon black powder in the raw materials undergo a solid-state reaction at high temperature. The specific reaction pathway is as follows: TiC (providing Ti and C) reacts directly with WC and carbon black powder at high temperature (2000-2200℃) to generate TiWC2: TiC + WC → TiWC2. Introducing carbon black powder and nitrogen, some TiC combines with C and nitrogen to form the impurity phase Ti(C,N): 2TiC + 2N2 → Ti(C,N).

[0017] 2. Microscopic enhancement mechanisms of elements (1) The layered structure of TiWC2 relieves stress concentration. TiWC2 is a layered MAX phase material. Its strong interlayer bonding interface can absorb crack propagation energy through interlayer slip, thereby dispersing local stress and significantly improving the fracture toughness of the material.

[0018] (2) Ti(C,N) inhibits crack propagation The high toughness of the byproduct Ti(C,N) hinders further crack propagation and forms a synergistic reinforcing effect with TiWC2.

[0019] (3) The promoting effect of Co binder phase Co, as a metallic binder phase, forms a liquid phase during sintering, promoting the diffusion of Ti, W, and C atoms and ensuring uniform reaction. Simultaneously, Co fills grain boundary pores, improving the alloy's density and thermal stability.

[0020] 3. Element ratio and performance regulation rules: The volume fraction of N2 (10%-20%) directly controls the amount of Ti(C,N) generated. Excess carbon black can adjust the proportion of TiWC2 generated. The ratio of the two needs to be balanced to achieve the best performance.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1. The preparation method of the present invention uniformly generates TiWC2 inside YT15 cemented carbide through in-situ reaction, avoiding the problem of excessive impurity phases in traditional methods.

[0022] 2. During the composite reaction of the alloy, the generated impurity phase is Ti(C,N), with a content of about 0.1~0.9wt%. Introducing TiWC2 and a small amount of Ti(C,N) as composite reinforcing phases into the YT15 cemented carbide system plays a role in interface strengthening. The layered structure of TiWC2 can alleviate stress concentration, while Ti(C,N) can inhibit crack propagation. The two work together to improve the fracture toughness of cemented carbide.

[0023] 3. The YT15 cemented carbide prepared by the method of the present invention has significantly improved hardness, fracture toughness, density, thermal stability and machinability, thereby optimizing its overall performance. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1 The preparation steps of 4.8wt% TiWC2 reinforced YT15 cemented carbide are as follows: S1. Take a 1:1 molar ratio of cemented carbide TiC powder and WC powder, both with a particle size of 20 μm. Mix and ball-mill them under vacuum. Add carbon black powder with a particle size of 30 μm during ball milling. Then sinter in a sintering furnace at 2100℃ for 2.5 h, and purge with nitrogen gas, the volume of which is 0.15 of the sintering furnace. Then crush them using an airflow crusher at a crushing pressure of 10 mbar and a classifying wheel speed of 1100 r / min. Ball mill them again to obtain powder with a particle size of 30 μm. S2, weigh WC powder, Co powder and TiC powder in a mass ratio of 80:6:14 and add them to a ball mill jar for ball milling and mixing. During the ball milling process, carbon black powder is added. The mass ratio of carbon black powder to Co powder is 0.15:1 to adjust the carbon content in the raw materials. The Fisher particle size of WC is 1.4μm, the particle size of Co is 1.8μm, and the particle size of TiC is 27μm. S3, by mass percentage, takes 4.8 wt% of the powder obtained from S1 and 95.2 wt% of the mixed powder obtained from S2, and adds them to a ball mill jar for ball milling and mixing. Add 1.8~2.4 wt% of anhydrous ethanol and paraffin as process control agents, with the mass ratio of anhydrous ethanol to paraffin being 1:1. S4. Spray dry the mixed powder obtained in S3 at a spray drying temperature of 250℃ and a spraying rate of 15m / s to obtain the mixed powder. S5. The dried mixed powder is pressed into shape and sintered in a pressure sintering furnace at a sintering temperature of 1600℃ for 2.5h. TiWC2 is synthesized through the alloy composite reaction during the sintering process, and TiWC2-reinforced YT15 cemented carbide is obtained.

[0026] In the above process, the ball milling parameters are as follows: the process is carried out in a vacuum environment, the ball milling speed is 250 rpm, and the ball milling time is 9 hours.

[0027] Example 2 4.2wt% TiWC2 reinforced YT15 cemented carbide The difference between Example 2 and Example 1 is that in step S3, 4.2 wt% of the total mass of cemented carbide obtained in S1 and 95.8 wt% of the total mass of cemented carbide obtained in S2 are added to a ball mill jar for ball milling and mixing.

[0028] Example 3 5.4wt% TiWC2 reinforced YT15 cemented carbide The difference between Example 3 and Example 1 is that in step S3, 5.4 wt% of the mixed powder obtained in S1 and 94.6 wt% of the mixed powder obtained in S2 of the total mass of cemented carbide are taken and added to a ball mill jar for ball milling and mixing.

[0029] Example 4 The difference between Example 4 and Example 1 is that, in step S1, the volume of nitrogen gas accounts for 0.1% of the sintering furnace volume.

[0030] Example 5 The difference between Example 5 and Example 1 is that, in step S1, the volume of nitrogen gas accounts for 0.2 of the sintering furnace.

[0031] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that nitrogen is not introduced in step S1.

[0032] Comparative Example 2 Preparation of YT15 cemented carbide 14 wt% TiC powder (particle size 20 μm), 80 wt% WC powder, and 6 wt% Co powder were added to a ball mill jar for vacuum ball milling. 2.1 wt% anhydrous ethanol and paraffin were added as process control agents. The ball milling speed was 250 rpm, and the milling time was 9 hours. After ball milling, the mixture was spray-dried at 250℃. The mixture was then pressed into shape and placed in a pressure sintering furnace for sintering at 1600℃ for 2.5 hours to obtain YT15 cemented carbide.

[0033] The cemented carbide obtained in the above five implementation examples and one comparative example was subjected to XRD analysis and compositional analysis using a fixed-target X-ray diffractometer (PANalytical XPert PRO MPD). The compositional analysis results of the cemented carbide and the raw material ratio are shown in Table 1, and the properties are shown in Table 2. Table 1. Composition analysis results and raw material ratio of cemented carbide

[0034] Table 2 Properties of cemented carbide

[0035] The data in Tables 1 and 2 show that as the nitrogen content increases, the Ti(C,N) content in the alloy increases, and the fracture toughness (KIC ≥ 14 MPa·m¹ / ²) also significantly improves. The hardness of the alloy remains relatively stable, and the bending strength remains at or above 1760 MPa, confirming the dominant role of TiWC2 in the reaction process. In contrast, Comparative Example 1 (no nitrogen addition) showed no Ti(C,N) formation, and Comparative Example 2, without nitrogen or pretreatment, showed no TiWC2 or Ti(C,N) formation, and its fracture toughness and bending strength properties deteriorated significantly.

[0036] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0037] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing TiWC2-reinforced YT15 cemented carbide, characterized in that, The specific steps are as follows: S1. Take equimolar amounts of cemented carbide TiC powder, WC powder, and carbon black powder, mix and ball-mill them under vacuum, then sinter them in a sintering furnace and fill them with nitrogen gas, the volume of which accounts for 10%-20% of the sintering furnace; then crush them with an airflow crusher and ball-mill them into powder again. S2, Weigh WC powder, Co powder and TiC powder and add them to a ball mill jar for ball milling and mixing. Add carbon black powder during the ball milling process to adjust the carbon content in the raw materials. S3, by mass percentage, takes 4.2~5.4 wt% of the powder obtained in S1 and 94.6~95.8 wt% of the mixed powder obtained in S2, adds them to a ball mill jar for ball milling and mixing, and adds 1.8~2.4 wt% of anhydrous ethanol and paraffin as process control agents. S4, spray dry the mixed powder obtained in S3 to obtain the mixed powder; S5. The dried mixed powder is pressed into shape and sintered in a pressure sintering furnace with nitrogen gas. The sintering temperature is 1550~1650℃ and the sintering time is 2~3h. TiWC2 is synthesized through the alloy composite reaction during the sintering process to obtain TiWC2 reinforced YT15 cemented carbide.

2. The method for preparing TiWC2-reinforced YT15 cemented carbide according to claim 1, characterized in that, The particle size of TiC powder and WC powder in S1 is 3μm~44μm, and the particle size of carbon black powder is 20μm~44μm.

3. The method for preparing TiWC2-reinforced YT15 cemented carbide according to claim 1, characterized in that, The sintering temperature in S1 is 2000-2200℃, and the sintering time is 2-3h.

4. The method for preparing TiWC2-reinforced YT15 cemented carbide according to claim 1, characterized in that, The process parameters for airflow crushing in S1 are: crushing pressure of 8-10 mbar and classifier speed of 1000-1200 r / min.

5. The method for preparing TiWC2-reinforced YT15 cemented carbide according to claim 1, characterized in that, The particle size of the powder produced by ball milling again in S1 is 20μm~30μm.

6. The method for preparing TiWC2-reinforced YT15 cemented carbide according to claim 1, characterized in that, In S2, the Fisher particle size of WC is 1.2μm~1.6μm, the particle size of Co is 1.6μm~2μm, and the particle size of TiC is 10μm~44μm.

7. The method for preparing TiWC2-reinforced YT15 cemented carbide according to claim 1, characterized in that, The mass ratio of WC powder, Co powder, and TiC powder in S2 is 80:6:14, and the mass ratio of carbon black powder to Co powder is (0.1-0.2):

1.

8. The method for preparing TiWC2-reinforced YT15 cemented carbide according to claim 1, characterized in that, In S1, S2 and S3, the ball milling parameters are: the process is carried out in a vacuum environment, the ball milling speed is 200~300 rpm, and the ball milling time is 6~12 h.

9. The method for preparing TiWC2-reinforced YT15 cemented carbide according to claim 1, characterized in that, The spray drying temperature in S4 is 200-300℃, and the spraying rate is 10-20m / s.

10. A TiWC2-reinforced YT15 cemented carbide, characterized in that, The YT15 cemented carbide reinforced with TiWC2 was prepared using the method described in any one of claims 1-9.

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