CN114277298A

CN114277298A - Graphene/nano Al adding method2O3WC-Co hard alloy of particles and preparation method

Info

Publication number: CN114277298A
Application number: CN202011036524.8A
Authority: CN
Inventors: 孙兰; 苏武丽; 范洪远
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2020-09-27
Filing date: 2020-09-27
Publication date: 2022-04-05
Anticipated expiration: 2040-09-27
Also published as: CN114277298B

Abstract

The invention relates to a graphene/nano Al-added material₂O₃WC-Co hard alloy of particles and a preparation method thereof belong to the technical field of high-performance hard alloy preparation. The added graphene oxide/nano Al₂O₃The WC-Co hard alloy of the composite particles uses the following raw materials and the preparation method: mixing nano Al₂O₃Preparing a colloidal solution, adding the colloidal solution into the graphene oxide suspension, and ultrasonically mixingQuickly freezing after 1-3h, and performing vacuum freeze drying to obtain the graphene oxide/nano Al₂O₃The composite particles of (3) are then added to the WC-Co powder. The final mixed powder consisted of: co: 6-11wt% of graphene oxide/nano Al₂O₃The composite powder of (a): 0.05 to 0.2 weight percent, and the balance of WC powder. Mechanically mixing the mixed powder for 10min-24h at a rotation speed of 30-1400rmin^‑1(ii) a Then, the WC-Co hard alloy is prepared by cold press molding and sintering, wherein the sintering temperature is 1300-. The WC-Co hard alloy with excellent performance can be prepared by the method, and is convenient for large-scale industrial application and production.

Description

Graphene/nano Al adding method2O3WC-Co hard alloy of particles and preparation method

Technical Field

The invention belongs to the field of high-performance new materials, and provides a method for improving the performance of WC-Co hard alloy, which can simultaneously improve the hardness, strength and toughness of the WC-Co hard alloy.

Background

Cemented carbide is widely used for wear-resistant parts and structural parts, plungers for high-pressure vessels, hydraulic cylinders, precision rolls, synthetic diamond hammers, rolls for wire rolling mills, and the like, because of its high hardness, high wear resistance, high-temperature corrosion resistance, and excellent toughness, and therefore, it is extremely important in the fields of machinery, metallurgy, cutting tools, precision instruments, military industry, and the like. In fact, despite the good mechanical properties of cemented carbides, conventional cemented carbides fail to meet the requirements of both high hardness and high toughness, due to the combined effect of the binder phase and the grain size. For example, WC-6Co cemented carbide with low cobalt content has high hardness, relatively low strength and low toughness. The preparation and application technology of high-performance cutters and tools and dies is always one of common key technologies developed in modern manufacturing industry. In addition, with the rapid development of the industries such as electronics, precision machining, medicine, aerospace and the like in recent years, the performance of the common WC-Co hard alloy can not completely meet the requirements for improving the machining efficiency and solving the problems of difficult material machining, precision mold manufacturing and the like. Therefore, how to obtain cemented carbide with high hardness, high strength and high toughness has become an important research direction for many researchers.

The influence of the current additives on the performance of the hard alloy is disclosed by a plurality of scientists in many aspects, such as the additive can improve the wear resistance, the impact resistance, the high-temperature performance, the cutting performance and the like of the alloy. Therefore, the research on the cemented carbide containing various additives is one of the development directions of the cemented carbide in the future.

Graphene has excellent physical and chemical properties in the aspects of force, heat, light, electricity, magnetism and the like and has a unique two-dimensional structure, and the graphene becomes a research hotspot in the field of domestic and foreign materials. The toughness of the graphene ceramic composite material can be obviously improved due to the excellent physical and chemical properties of the graphene ceramic composite material; the nano alumina has huge potential in a plurality of special fields requiring low density, high rigidity, high hardness, chemical inertness and good high-temperature performance, and the doping of a small amount of nano alumina is beneficial to improving the sintering density, the bending strength and the fracture toughness of the zirconia ceramic. However, graphene has a large specific surface area and is easily agglomerated, and the addition of graphene to a matrix adversely reduces the performance. Compared with graphene, graphene oxide is easy to disperse in water due to oxygen-containing functional groups, so that the phenomenon of graphene agglomeration can be solved if graphene oxide and nano-alumina are respectively formed into colloidal solutions and then form composite particles through electrostatic interaction, and the particles are added into an alloy matrix to play a role in enhancing graphene oxide and nano-alumina. The principle of the electrostatic action is that the graphene oxide colloidal solution is electronegative, the nano-alumina colloidal solution is positively charged, and the positively charged alumina particles in the mixed solution are precipitated on the negatively charged graphene oxide, so that the contact between graphene oxide lamella is blocked, and the graphene oxide is well dispersed. And drying the final mixed solution to obtain the dispersed graphene oxide/nano-alumina composite particles. Therefore, when the graphene oxide/nano-alumina composite particles are added to the WC-Co hard alloy, the mechanical property of the WC-Co hard alloy is more excellent than that of the WC-Co hard alloy.

Disclosure of Invention

The content of the invention is that the WC-Co hard alloy is prepared by adding a certain content of graphene oxide/nano-alumina composite powder, the problem of alloy decarburization is solved, WC crystal grains are inhibited from growing, the alloy is highly densified, and the hardness, strength and toughness of the WC-Co hard alloy are further improved.

The invention relates to a preparation method of WC-Co hard alloy added with graphene oxide/nano-alumina composite particles. Preparing nano alumina (20 nm-100 nm) into an alumina colloidal solution, adding the alumina colloidal solution into the graphene oxide suspension, carrying out ultrasonic mixing for 1-3h, then carrying out quick freezing, and carrying out vacuum freeze drying to obtain the graphene oxide/nano alumina composite particles. Then preparing the WC-Co hard alloy added with the graphene oxide/nano-alumina composite particles. The mixed powder comprises the following components: co: 6-10wt%, graphene oxide/nano-alumina composite powder: 0.05-0.2wt%, balance grain size WC (less than 5 μm); weighing the mixed powder according to the weight percentage, and then carrying out mechanical alloying treatment, wherein the ball milling time is 10min-48h, and the rotating speed of the ball mill is 30-1400rmin^-1(ii) a The ball-material ratio is 5:1-20:1, and the addition amount of the ball-milling medium is 5-10mm higher than the surface of the ball-powder; cold-pressing the mixed powder to form a preform with the density of 50-70%, sintering to prepare WC-Co hard alloy containing graphene, wherein the sintering temperature is 1300-1450 ℃, the sintering pressure is 0-60MPa, the sintering time is 5-120min, and air cooling is carried out to room temperature; and then carrying out low-pressure sintering treatment on the obtained sample, wherein the treatment pressure is 5-10 MPa. The WC-Co hard alloy with excellent performance can be prepared by the method.

Several powder particles are subjected to a mechanical alloying (high energy ball milling) operation prior to the powder forming, and the mechanical alloying (high energy ball milling) equipment may be a planetary ball mill, a stirred ball mill, and a vibratory ball mill. The mechanical alloying (high energy ball milling) can be dry type or wet type, the dry type ball milling is carried out under protective atmosphere, the wet type ball milling is mixed by organic liquid, and the organic liquid comprises ethanol, acetone, petroleum ether and the like. By the mechanical alloying (high energy ball milling) treatment, the raw material powder particles can be deformed, broken, and recombined, and the specific surface area and internal defects of the powder particles can be increased, thereby increasing the activation energy of the raw material powder particles, thereby promoting sintering and improving the performance of the sintered body. Specifically, the added powder can be fully and uniformly mixed, and larger aggregates in the superfine WC powder can be reduced. Mechanical alloying equipment such as planetary ball mills, stirring ball mills, and vibration ball mills can meet the above requirements. The protective atmosphere in the dry ball milling and the organic liquid in the wet ball milling can prevent the oxidation and adverse reaction of the raw material powder particles in the ball milling process.

The sintering comprises one, two or three of normal pressure sintering, decompression or vacuum sintering, pressure sintering, hot pressing, hot isostatic pressing, spark plasma sintering, electric spark sintering and microwave sintering. The WC-Co hard alloy can be prepared by the method; sintering is carried out under a protective atmosphere, which is vacuum, argon, hydrogen, nitrogen, decomposed ammonia, or the like. The oxidation and adverse reaction of the powder in the sintering process can be prevented by adopting the protective atmosphere.

The invention has the advantages that the graphene oxide has excellent physical and chemical properties and unique two-dimensional structure in the aspects of force, heat, light, electricity, magnetism and the like as the graphene oxide, and the nano aluminum oxide has great potential in a plurality of special fields requiring low density, high rigidity, high hardness, chemical inertness and good high-temperature performance. The composite particles are formed by skillfully utilizing the characteristic that the electrical properties of the two colloidal solutions are opposite, so that the purpose of dispersing the graphene oxide is achieved, the excellent performances of the two colloidal solutions are fully exerted, the strength, the toughness and the wear resistance of the WC-Co hard alloy are further improved, the service life of the WC-Co hard alloy can be greatly prolonged compared with the common WC-Co hard alloy, and the industrial application prospect is wide.

Detailed Description

The following describes embodiments of the present invention. These embodiments are merely examples provided to enhance understanding of the present invention, and of course, should not be construed as limiting the present invention. The scope of the invention should be measured in the claims. The embodiments can be variously modified without departing from the gist of the present invention. This should be understood by those skilled in the art.

Example 1:

preparing raw materials: mixing the components in a volume ratio of 1: 1 weighing alpha-Al₂O₃Powder (20 nm) and few-layer graphene oxide powder (400 nm), untreated alpha-Al₂O₃Introducing into a beaker, adding distilled water to make the solution concentration 5 × 10^-3g/ml, and adjusting the pH value to be about 3.33 by using 1mol/L HCl solution, and carrying out ultrasonic treatment for 2 hours to form a colloid. And simultaneously dispersing graphene oxide powder in distilled water, and performing ultrasonic treatment for 5 hours to form colloid. And mixing the two colloids, performing ultrasonic treatment for 1h, performing rapid freezing by using liquid nitrogen, and finally treating in a vacuum freeze dryer for 24h to obtain the graphene oxide/nano-alumina composite particles after drying. Furthermore, WC powder having a particle size of 2 μm and pure WC powder having a particle size of 1 μm were preparedAnd (3) Co powder.

According to the mass ratio of WC powder, Co powder and graphene oxide/nano-alumina composite powder of 93.95: 6: the raw material powder is put into a small ball milling tank according to the proportion of 0.05, and alcohol is added as a ball milling medium. And (3) taking WC-Co hard alloy balls as grinding balls, wherein the ball material ratio is 20:1, and performing wet rolling ball milling for 24 hours at the rotating speed of 30 r/min. And discharging after the ball milling is finished. Scouring the abrasive material by 99.99 percent alcohol, and filtering by adopting screens with different particle sizes; the de-alcoholized mass was placed in an oven and baked at 90 ℃ for about 30min until completely dry. Mixing the prepared natural rubber and gasoline solution into the material, stirring and drying. After drying, cold press forming is carried out. And then placing the pressed compact into a vacuum sintering furnace for sintering, firstly heating to about 400 ℃, and preserving heat for 1h to ensure degumming. Heating to 1230 deg.C for 30min in 2h, heating to 1440 deg.C for sintering in 1h, keeping the temperature for 2h, and air cooling to room temperature. The hardness of the prepared sample is 92.5HRA, the bending strength is 2280MPa, and compared with the hard alloy without adding graphene powder under the same condition, the hardness, the bending strength and the fracture toughness of the prepared sample are improved to some extent, and the grain size is smaller. Then, the obtained sample is subjected to low-pressure sintering treatment, the treatment pressure is 5MPa, the pores of the obtained sample completely disappear, the strength is up to 2540MPa, and the fracture toughness is up to 11.65MPa m^1/2The comprehensive performance is greatly improved.

Example 2:

mixing the components in a volume ratio of 1: 2 weighing alpha-Al₂O₃Powder (20 nm) and few-layer graphene oxide powder (400 nm), untreated alpha-Al₂O₃Introducing into a beaker, adding distilled water to make the solution concentration 5 × 10^-3g/ml, and adjusting the pH value to about 3.33 by using 1mol/L HCl solution, and carrying out ultrasonic treatment for 1 hour to form a colloid. And simultaneously dispersing graphene oxide powder in distilled water, and performing ultrasonic treatment for 5 hours to form colloid. And mixing the two colloids, performing ultrasonic treatment for 1h, performing rapid freezing by using liquid nitrogen, and finally treating in a vacuum freeze dryer for 24h to obtain the graphene oxide/nano-alumina composite particles after drying. WC powder having a particle size of 0.2 μm and pure Co powder having a particle size of 1 μm were prepared.

According toThe mass ratio of WC powder, Co powder and graphene oxide/nano-alumina composite powder is 89.8:10:0.2, the raw material powder is put into a small ball milling tank, and alcohol is added as a ball milling medium. WC-Co hard alloy balls are used as grinding balls, and the rotating speed of the ball mill is 1400rmin^-1(ii) a The ball-material ratio is 10:1, the adding amount of the ball-milling medium is 5-10mm higher than the surface of the ball-powder, and three-dimensional vibration high-energy ball milling is adopted for 10 min. And after the ball milling is finished, discharging, filtering by using a screen, and baking for about 30min at the temperature of 90 ℃ until the mixture is completely dried. And putting the dried powder into a graphite die, sintering in a discharge plasma sintering furnace, applying pressure of 40MPa, heating at a speed of 100 ℃/min to about 400 ℃, and keeping the temperature for 5min to remove impurities such as moisture and the like. Then heating to 1300 ℃ and preserving the temperature for 10min, and then cooling to room temperature by water. The prepared sample is fully compact, the hardness is 90.7HRA, and the bending strength is 2720 MPa. Then, the obtained sample is subjected to low-pressure sintering treatment, the treatment pressure is 8MPa, the obtained strength reaches 2890MPa, and the fracture toughness reaches 17.3MPa m^1/2The comprehensive performance is greatly improved.

The above-described embodiments are merely examples provided to enhance understanding of the present invention, and various modifications may be made. For example, the sintering method used in the above embodiment may be replaced with hot press sintering, hot isostatic pressing, microwave sintering, or the like, and the same or similar effects as those of the above embodiment can be obtained.

Claims

1. A WC-Co hard alloy added with graphene oxide/nano-alumina composite particles and a preparation method thereof are characterized in that: preparing nano alumina (20 nm-100 nm) into an alumina colloidal solution, adding the alumina colloidal solution into a graphene oxide suspension, performing ultrasonic mixing for 1-3h, then performing quick freezing, performing vacuum freeze drying to obtain graphene oxide/nano alumina composite particles, then adding the composite particles into WC-Co powder, and finally mixing the powder components: co: 6-11wt%, graphene oxide/nano-alumina composite powder: 0.05-0.2wt%, balance WC powder with grain size less than 5 μm; weighing the mixed powder according to the weight percentage, and then mechanically mixing the powder for 10min to 24h at the rotating speed of 30 to 1400rmin^-1(ii) a The ball-material ratio is 5:1-20:1, the WC-Co hard alloy is prepared by cold press molding and sintering the mixed powder, the sintering temperature is 1300-; the WC-Co hard alloy with excellent performance and stability can be prepared by the method.

2. The method of claim 1, wherein: the equipment for mechanically mixing the mixed powder particles is a planetary ball mill, a stirring ball mill or a vibration ball mill; the ball milling is dry ball milling or wet ball milling, and the dry ball milling is carried out in a protective atmosphere; the wet ball milling is carried out by mixing organic liquid, wherein the organic liquid comprises ethanol, acetone, petroleum ether or hexane.

3. The method of claim 1, wherein: the sintering method comprises 1-3 of normal pressure sintering, low pressure or vacuum sintering, pressure sintering, hot pressing, hot isostatic pressing, spark plasma sintering, electric spark sintering and microwave sintering.