High-wear-resistance hard alloy nozzle and preparation method thereof

Abstract

The invention relates to the field of alloy material forming, and discloses a high-wear-resistance hard alloy nozzle and a preparation method thereof, the hard alloy component is WC as a hard phase, and high hardness and wear resistance are provided. Co is used as a binding phase to enhance the toughness and strength of the alloy. VC / Cr3C2 / ZrC is used as an additive and is used for refining grains, inhibiting WC grain growth and improving the comprehensive performance of the alloy. The high-wear-resistance hard alloy nozzle is prepared through the procedures of wet grinding, spray drying, precise compression molding, partial pressure sintering and the like. By optimizing the hard alloy components and the preparation process, the hard alloy nozzle with high wear resistance, high hardness and excellent mechanical properties is prepared.

Description

Technical Field

[0001] The present invention relates to the field of alloy material forming, and particularly to a high-wear-resistant cemented carbide nozzle and a preparation method thereof. Background Art

[0002] As a core component of high-pressure water jet cleaning, metal surface sandblasting, industrial spraying and other equipment, the service performance of the cemented carbide nozzle directly affects the processing efficiency and quality. In the field of high-pressure water jets, the nozzle needs to withstand high-speed water flows with pressures up to 100 - 300 MPa (flow velocities exceeding 500 m / s), and the fine particles carried in the water cause strong erosion wear on the inner wall of the orifice; in sandblasting operations, high-speed sand grains (30 - 100 m / s) continuously impact the inner surface of the nozzle, forming abrasive wear and fatigue damage; in the spraying scenario, the high-speed spraying of high-temperature molten coating materials not only brings mechanical wear, but may also cause chemical corrosion. The above working conditions pose strict requirements on the nozzle material: it is required to have a high hardness of ≥1600 HV to resist the cutting of abrasive grains, a flexural strength of ≥1500 MPa to withstand high-pressure loads, a fracture toughness of ≥12 MPa·m 1 / 2 to inhibit crack propagation, and at the same time, it is required to have excellent corrosion resistance to cope with complex medium environments.

[0003] Traditional cemented carbide nozzles generally use YJ6X alloy (WC - 6% Co-based alloy), which is prepared by conventional powder metallurgy processes, and the structure is a WC-Co two-phase structure. However, this material has shown significant defects during long-term service:

[0004] Insufficient wear resistance: The WC grain size is about 1.5 - 2.0 μm, and the uniformity of the cobalt phase distribution is poor. Under the impact of high-speed particles, the cobalt binder phase is prone to plastic deformation, resulting in the shedding of WC grains and the formation of abrasive wear grooves. Especially in an environment containing chloride ions or acidic media, the cobalt phase is prone to electrochemical corrosion, which aggravates material loss, leading to an increase in the nozzle orifice diameter and a decrease in jet accuracy. The typical service life is only 50 - 80 hours.

[0005] Imbalance in strength and toughness matching: The traditional preparation process is difficult to control the thickness of the cobalt phase at the WC grain boundaries. The local segregation of the cobalt phase leads to a decrease in hardness, while the cobalt-phase-depleted regions initiate microcrack propagation due to insufficient toughness. Under high-pressure conditions, stress concentration at the nozzle outlet is prone to induce crack initiation, which in turn leads to sudden fracture failure.

[0006] Limitations in corrosion resistance: The cobalt binder phase of the YJ6X alloy has weak resistance to erosion in humid environments, acidic media or molten metals. During long-term service, the corrosive loss of the cobalt phase will damage the WC skeleton structure and accelerate material failure.

[0007] In the prior art, although the performance of the nozzle has been improved by surface PVD coatings (such as TiN, CrC) or structural optimization (such as variable-diameter pore design), the bonding strength between the coating and the substrate is limited and it is easy to peel off under high-pressure impact; the structural improvement cannot fundamentally solve the wear resistance and corrosion resistance problems of the material body. Therefore, in view of the high-efficiency processing requirements under extreme working conditions, it is urgent to develop a new type of cemented carbide nozzle with high hardness, excellent strength and toughness matching, and corrosion resistance, to break through the performance bottleneck of the traditional YJ6X alloy nozzle, and to significantly improve the service life and reliability of the nozzle. Summary of the Invention

[0008] The present invention aims to provide a cemented carbide nozzle with high wear resistance and its preparation method, so as to provide a new type of cemented carbide nozzle with high hardness, excellent strength and toughness matching, and corrosion resistance.

[0009] To achieve the above object, the present invention adopts the following technical solution: A cemented carbide nozzle with high wear resistance is made of tungsten carbide as the hard phase, cobalt as the binder phase, and vanadium carbide, chromium carbide, and zirconium carbide as additives, having a hardness greater than HV30 1900, a flexural strength greater than 3500 Mpa, and a fracture toughness greater than or equal to 11.5 MPa·m^1 / 2.

[0010] Preferably, as an improvement, in its components, by mass, it contains 85-92 parts of tungsten carbide, 6-10 parts of cobalt, 0.3-1 part of vanadium carbide, 0.5-1.5 parts of chromium carbide, and 0.2-0.8 part of zirconium carbide.

[0011] Preferably, as an improvement, by mass, it contains 86-89 parts of tungsten carbide, 8-9 parts of cobalt, 0.8-1.2 parts of vanadium carbide, 0.8-1.2 parts of chromium carbide, and 0.3-0.7 part of zirconium carbide.

[0012] A preparation method of a cemented carbide nozzle with high wear resistance is used to prepare a cemented carbide nozzle with high wear resistance as described above, including:

[0013] A. Batching, weighing WC, Co, VC, Cr3C2 and ZrC powders according to the ratio;

[0014] B. Wet grinding, using alcohol or water as the grinding medium to wet grind the raw materials, and the wet grinding time is 24-48 hours;

[0015] C. Spray drying, spray drying the wet-ground slurry;

[0016] D. Precision pressing and forming, using precision pressing to form the nozzle blank;

[0017] E. Sintering, sintering the nozzle blank after dewaxing.

[0018] Preferably, as an improvement, in the wet grinding step, PEG is first dissolved in water, then the solution is mixed with alcohol and wet-ground with the raw materials. The mass ratio of the raw materials, alcohol, water, and PEG is 1000:276:20:15 - 25.

[0019] Preferably, as an improvement, during the spray drying process, the drying temperature is controlled at 170 - 190 °C at the inlet and 90 - 100 °C at the outlet. The air flow velocity during the drying process is 120 - 140 m / s for the atomizing air flow and 1.2 - 1.4 m / s for the drying air flow.

[0020] Preferably, as an improvement, during the precision pressing forming process, the mold accuracy is controlled at ±0.02 mm, the pressing accuracy is ±0.02 mm, and the pressing pressure is 100 - 200 MPa.

[0021] Preferably, as an improvement, during the sintering process, the nozzle blank is first dewaxed in a hydrogen atmosphere at room temperature to 600 °C, then subjected to partial pressure sintering in the temperature range of 1280 - 1420 °C with the pressure controlled at 2000 Pa, and then subjected to low-pressure sintering under a pressure of 4 - 6 MPa.

[0022] The cemented carbide nozzle of the present invention uses tungsten carbide as the hard phase to provide high hardness and wear resistance, cobalt as the binder phase to enhance the toughness and strength of the alloy, and vanadium carbide / chromium carbide / zirconium carbide as additives to refine the grains, inhibit the growth of WC grains, and zirconium carbide improves the wear resistance and the comprehensive performance of the alloy.

[0023] The present invention realizes the precise matching of high wear resistance and mechanical properties by coordinately regulating the microstructure and composition distribution of cemented carbide through multiple processes: during batching, the oxygen content of WC, Co, VC, Cr3C2, and ZrC powders is precisely controlled, and the interfacial bonding state between the binder phase (Co) and the hard phase (WC) is adjusted through the oxygen-carbon balance to avoid decarburization or carburization defects; during wet milling, water acts as a solvent for PEG to form a stable dispersion system, ensuring the uniform mixing of multi-component powders in an alcohol medium. At the same time, the oxygen content of the original powders is regulated by the physicochemical action between water and the metal / carbide surface, inhibiting Co oxidation and promoting the hydroxylation of the WC grain surface, providing uniform raw materials for subsequent sintering; spray drying forms spherical powders with good fluidity by quickly evaporating the slurry through controlling the temperature range of 170 - 190°C at the inlet and 90 - 100°C at the outlet and the atomizing air flow of 120 - 140 m / s, avoiding PEG decomposition and powder agglomeration; precision pressing is carried out with a die precision of ±0.02 mm and a pressure of 100 - 200 MPa to form the blank, ensuring uniform blank density and shape precision, and reducing the sintering shrinkage deviation; during the sintering stage, the hydrogen dewaxing process from room temperature to 600°C removes PEG and reduces trace oxides, and the partial pressure sintering (1280 - 1420°C, 2000 Pa) controls the volatilization of the cobalt phase to optimize the thickness of the grain boundary cobalt layer, and the low-pressure sintering (4 - 6 MPa) eliminates pores and promotes the close combination of WC grains and the Co phase, finally forming a high-performance alloy with refined WC grains (≤1μm), uniform distribution of the cobalt phase, and a relative density ≥99.5%. VC and Cr3C2 synergistically inhibit the coarsening of WC grains, and ZrC enhances the grain boundary strength through dispersion strengthening. Combined with process regulation, the hardness > HV30 1900, the flexural strength > 3500 MPa, and the fracture toughness ≥ 11.5 MPa·m 1 / 2 to achieve the performance balance and meet the wear resistance requirements of extreme working conditions such as high-pressure erosion and sandblasting.

[0024] In practical applications, the high-wear-resistance cemented carbide nozzles prepared by the present invention are applicable to fields such as high-pressure water jet, sandblasting, and spraying, and are especially suitable for long-term use in high-wear and high-corrosion environments.

[0025] The advantages of the present invention include:

[0026] 1. Improved component uniformity and performance stability. In traditional processes, component segregation easily occurs during batching and mixing, resulting in unstable alloy performance. The present invention ensures the uniform distribution of WC, Co, VC, Cr3C2, and ZrC powders through precise batching and wet milling processes, making the performance of each part of the alloy more consistent. In actual use, this component uniformity enables uniform wear of each part of the nozzle during operation, extends the overall service life of the nozzle, and reduces premature failure caused by local performance differences.

[0027] 2. Precise regulation of oxygen content and carbon content. In traditional processes, it is difficult to precisely control the oxygen content and carbon content, which easily leads to decarburization or carburization of the alloy, affecting the microstructure and properties of the alloy. In the present invention, by controlling the oxygen content of raw materials and the role of water during batching and wet grinding, and the participation of hydrogen during sintering, precise regulation of the carbon content of the alloy is achieved. The precise carbon content regulation enables the binder phase and the hard phase to be in the optimal proportion and performance state, improving the hardness, toughness, and wear resistance of the alloy. In the application of high-pressure water jet cutting, the cutting efficiency of the nozzle prepared by the present invention is 15%-20% higher than that of traditional nozzles, and at the same time, the cutting accuracy is also significantly improved.

[0028] 3. Improvement of powder quality and forming accuracy. Traditional drying and forming processes are prone to problems such as powder agglomeration and low forming accuracy. The spray drying process of the present invention prepares powders with good fluidity and uniform particle size by precisely controlling the temperature and air flow rate, avoiding powder agglomeration. The precision pressing forming process ensures the density and shape accuracy of the nozzle blank, and the die accuracy and pressing accuracy reach ±0.02 mm, greatly improving the forming accuracy. The good powder quality and forming accuracy result in high dimensional accuracy and good surface finish of the sintered nozzle, reducing subsequent processing steps, improving production efficiency, and enhancing the market competitiveness of the product.

[0029] 4. Alloy densification and enhancement of mechanical properties. It is difficult to achieve sufficient densification of the alloy in traditional sintering processes, resulting in more pores in the alloy and poor mechanical properties. The combination of partial pressure sintering and low-pressure sintering processes in the present invention effectively controls the volatilization of the cobalt phase, eliminates pores, and enables the relative density of the alloy to reach more than 99.5%, which is 1%-2% higher than that of traditional processes. At the same time, the mechanical properties such as the hardness, flexural strength, and fracture toughness of the alloy are also significantly improved. Under harsh working conditions such as high-pressure sandblasting, the nozzle prepared by the present invention can withstand higher pressure and impact force, and the wear rate is 30%-40% lower than that of traditional nozzles, and the service life is extended by 1-2 times. Detailed implementation methods

[0030] The following is a further detailed description through specific implementation methods:

[0031] Example 1. A high-wear-resistant cemented carbide nozzle is made of tungsten carbide as the hard phase, cobalt as the binder phase, and vanadium carbide, chromium carbide, and zirconium carbide as additives. It has a hardness greater than HV30 1900, a flexural strength greater than 3500 Mpa, and a fracture toughness greater than or equal to 11.5 MPa·m^1 / 2. In its components, by mass fraction, it contains 85-92 parts of tungsten carbide, 6-10 parts of cobalt, 0.3-1 part of vanadium carbide, 0.5-1.5 parts of chromium carbide, and 0.2-0.8 parts of zirconium carbide.

[0032] Example 2. The difference between this example and Example 1 is only that, by mass parts, it contains 86 - 89 parts of tungsten carbide, 8 - 9 parts of cobalt, 0.8 - 1.2 parts of vanadium carbide, 0.8 - 1.2 parts of chromium carbide, and 0.3 - 0.7 parts of zirconium carbide.

[0033] Example 3. A method for preparing a high - wear - resistant cemented carbide nozzle, which is used to prepare a high - wear - resistant cemented carbide nozzle of Example 1 or Example 2, includes:

[0034] Batching. Weigh WC, Co, VC, Cr3C2, and ZrC powders according to the ratio; ensure the uniform distribution of each component. Control the oxygen content of the raw materials to regulate the carbon content of the alloy and ensure that the binder phase and hard phase are within the optimal range.

[0035] Wet grinding. Put the batch into a ball mill for wet grinding. Use alcohol or water as the grinding medium to wet - grind the raw materials. First, dissolve PEG in water, then mix the solution with alcohol and wet - grind it with the raw materials. The mass ratio of raw materials, alcohol, water, and PEG is 1000:276:20:15 - 25, and the wet - grinding time is 24 - 48 hours to ensure that the powders are fully mixed and reach the required particle size. The role of water here is to fully dissolve peg and at the same time regulate the oxygen content of the original powder.

[0036] Spray drying. Spray - dry the wet - ground slurry. Control the drying temperature to be 170 - 190℃ at the inlet and 90 - 100℃ at the outlet. The air flow velocity during the drying process is 120 - 140m / s for the atomizing air flow and 1.2 - 1.4m / s for the drying air flow to ensure the uniform drying of the powders and good fluidity.

[0037] Precision pressing forming. Use the precision pressing method to form the nozzle blank. Control the mold accuracy to be ±0.02mm and the pressing accuracy to be ±0.02mm, and the pressing pressure to be 100 - 200Mpa to ensure that the density and shape of the blank meet the requirements.

[0038] Sintering. First, dewax the nozzle blank in a hydrogen atmosphere from room temperature to 600℃ to remove organic additives such as PEG and at the same time adjust the carbon content of the alloy. Then carry out partial - pressure sintering in the temperature range of 1280 - 1420℃, with the pressure controlled at 2000Pa. Control the volatilization of the cobalt phase of the alloy during the sintering process through partial - pressure to adjust the alloy microstructure. Then carry out low - pressure sintering under a pressure of 4 - 6MPa to further densify the alloy and improve its mechanical properties.

[0039] The present invention realizes the precise matching of high wear resistance and mechanical properties by coordinately regulating the microstructure and composition distribution of cemented carbide through multiple processes: during batching, the oxygen content of WC, Co, VC, Cr3C2, and ZrC powders is precisely controlled, and the interfacial bonding state between the binder phase (Co) and the hard phase (WC) is adjusted through oxygen-carbon balance to avoid decarburization or carburization defects; during wet grinding, water acts as a solvent for PEG to form a stable dispersion system, ensuring the uniform mixing of multi-component powders in an alcohol medium. At the same time, the oxygen content of the original powders is regulated by the physicochemical action between water and the metal / carbide surface, inhibiting Co oxidation and promoting the hydroxylation of the WC grain surface to provide uniform raw materials for subsequent sintering; spray drying forms spherical powders with good fluidity by quickly evaporating the slurry through controlling the temperature range of 170 - 190 °C at the inlet and 90 - 100 °C at the outlet and the atomization air flow of 120 - 140 m / s, avoiding PEG decomposition and powder agglomeration; precision pressing is carried out with a die precision of ±0.02 mm and a pressure of 100 - 200 MPa to ensure uniform blank density and shape precision, reducing sintering shrinkage deviation; during the sintering stage, the PEG is removed and trace oxides are reduced during the hydrogen dewaxing process from room temperature to 600 °C. The partial pressure sintering (1280 - 1420 °C, 2000 Pa) controls the cobalt phase volatilization to optimize the thickness of the cobalt layer at the grain boundary, and the low-pressure sintering (4 - 6 MPa) eliminates pores and promotes the close combination of WC grains and the Co phase, finally forming a high-performance alloy with refined WC grains (≤1 μm), uniform distribution of the cobalt phase, and a relative density ≥99.5%. VC and Cr3C2 synergistically inhibit the coarsening of WC grains, and ZrC enhances the grain boundary strength through dispersion strengthening. Combined with process regulation, the hardness > HV30 1900, the flexural strength > 3500 MPa, and the fracture toughness ≥11.5 MPa·m 1 / 2 to achieve a performance balance and meet the wear resistance requirements of extreme working conditions such as high-pressure erosion and sandblasting.

[0040] The above are only examples of the present invention, and specific technical solutions and / or common knowledge such as characteristics well known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application shall be subject to the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. A high wear-resistant cemented carbide nozzle, characterized in that: It is made by using tungsten carbide as the hard phase, cobalt as the binder phase, and vanadium carbide, chromium carbide, and zirconium carbide as additives, and has a hardness greater than HV30 1900, a flexural strength greater than 3500 Mpa, and a fracture toughness greater than or equal to 11.5 MPa·m^1 / 2.

2. A highly wear-resistant cemented carbide nozzle according to claim 1, characterized in that: In its components, by mass fraction, it contains 85 - 92 parts of tungsten carbide, 6 - 10 parts of cobalt, 0.3 - 1 part of vanadium carbide, 0.5 - 1.5 parts of chromium carbide, and 0.2 - 0.8 parts of zirconium carbide.

3. The high-wear-resistant cemented carbide nozzle according to claim 2, wherein: By mass fraction, it contains 86 - 89 parts of tungsten carbide, 8 - 9 parts of cobalt, 0.8 - 1.2 parts of vanadium carbide, 0.8 - 1.2 parts of chromium carbide, and 0.3 - 0.7 parts of zirconium carbide.

4. A preparation method of a high-wear-resistant cemented carbide nozzle, which is used to prepare a high-wear-resistant cemented carbide nozzle as described in any one of claims 1-3, and is characterized in that: It includes: A. Batching, weighing WC, Co, VC, Cr3C2, and ZrC powders according to the proportion; B. Wet grinding, using alcohol or water as the grinding medium to wet grind the raw materials, and the wet grinding time is 24 - 48 hours; C. Spray drying, spray drying the wet - ground slurry; D. Precision pressing and forming, using the precision pressing method to form the nozzle blank; E. Sintering, sintering the nozzle blank after dewaxing.

5. A highly wear-resistant cemented carbide nozzle and a preparation method thereof according to claim 5, characterized in that: In the wet - grinding step, first dissolve PEG in water, then mix the solution with alcohol and wet - grind it with the raw materials. The mass ratio of the raw materials, alcohol, water, and PEG is 1000:276:20:15 - 25.

6. A high-wear-resistant cemented carbide nozzle according to claim 6 and a preparation method thereof, characterized in that: During the spray - drying process, control the drying temperature at 170 - 190 °C at the inlet and 90 - 100 °C at the outlet, and the air - flow speed during the drying process is 120 - 140 m / s for the atomizing air - flow and 1.2 - 1.4 m / s for the drying air - flow.

7. A highly wear-resistant cemented carbide nozzle and its preparation method according to claim 7, characterized in that: During the precision - pressing and forming process, control the mold accuracy at ±0.02 mm, the pressing accuracy at ±0.02 mm, and the pressing pressure at 100 - 200 MPa.

8. A high wear-resistant cemented carbide nozzle and a preparation method thereof according to claim 8, characterized in that: During the sintering process, first dewax the nozzle blank in a hydrogen atmosphere from room temperature to 600 °C, then carry out partial - pressure sintering in the temperature range of 1280 - 1420 °C, control the pressure at 2000 Pa, and then carry out low - pressure sintering under a pressure of 4 - 6 MPa.