阅读说明：本技术 一种碳纤维-(Ti,V)(C,N)硬质合金及其制备方法 (Carbon fiber- (Ti, V) (C, N) hard alloy and preparation method thereof ) 是由 邹建新 张凤春 周红梅 刘杰慧 李旭勤 喻红梅 鲜勇 于 2019-09-30 设计创作，主要内容包括：本发明公开了一种碳纤维-(Ti,V)(C,N)硬质合金及其制备方法,该硬质合金按重量百分比包括以下组分：Ti<Sub>x</Sub>V<Sub>1-x</Sub>CN粉78％～87％；碳纤维1％～5％；金属粘结剂10％～20％；其中,所述Ti<Sub>x</Sub>V<Sub>1-x</Sub>CN粉中的x取值范围为0.6～0.9。本发明还公开制备方法,包括将配料经过湿法球磨混合、干燥、压制成型、烧结制得硬质合金。本发明硬质合金引入了碳纤维材料,利用碳纤维拔断和拔出的增韧机制来增强硬质合金整体的韧性,针对C纤维增韧后的Ti(C,N)合金材料强度弱化问题,将晶粒细化剂VC作为主相融入Ti(C,N)合金,形成了碳纤维-VC主体相协同增韧补强的强势效应,在冲击韧性上优于钨基硬质合金。(The invention discloses a carbon fiber- (Ti, V) (C, N) hard alloy and a preparation method thereof, wherein the hard alloy comprises the following components in percentage by weight: ti x V 1‑x 78 to 87 percent of CN powder; 1% -5% of carbon fiber; 10% -20% of metal binder; wherein, the Ti x V 1‑x The value range of x in the CN powder is 0.6-0.9. The invention also discloses a preparation method, which comprises the steps of carrying out wet ball milling mixing, drying, press forming and sintering on the ingredients to obtain the hard alloy. The hard alloy of the invention introduces the carbon fiber material, utilizes the toughening mechanism of carbon fiber breaking and pulling out to enhance the toughness of the whole hard alloy, aims at the problem of weakening the strength of the Ti (C, N) alloy material toughened by C fiber,the grain refiner VC is blended into Ti (C, N) alloy as a main phase to form a strong effect of carbon fiber-VC main phase synergistic toughening and reinforcement, and is superior to tungsten-based hard alloy in impact toughness.)

1. A carbon fiber- (Ti, V) (C, N) hard alloy is characterized by comprising the following components in percentage by weight:

Ti_xV_1-x78 to 87 percent of CN powder;

1% -5% of carbon fiber;

10% -20% of metal binder;

wherein, the Ti_xV_1-xThe value range of x in the CN powder is 0.6-0.9.

2. The carbon fiber- (Ti, V) (C, N) cemented carbide of claim 1, wherein the carbon fiber accounts for 1-3% of the total mass of the cemented carbide.

3. The carbon fiber- (Ti, V) (C, N) cemented carbide of claim 2, wherein the carbon fiber accounts for 1.8-2.2% of the total mass of the cemented carbide.

4. The carbon fiber- (Ti, V) (C, N) cemented carbide of claim 1, wherein the carbon fiber has a length of 20 to 1500 microns.

5. The carbon fiber- (Ti, V) (C, N) cemented carbide of claim 4, wherein the carbon fiber has a length of 200-1000 microns.

6. Carbon fiber- (Ti, V) (C, N) cemented carbide according to claim 1, characterized in that the metallic binder is one or more of cobalt, nickel, molybdenum, manganese.

7. Carbon fiber- (Ti, V) (C, N) cemented carbide according to any one of claims 1-6, characterized in that the metal binder is one or a mixture of two of metallic molybdenum and metallic nickel.

8. A method for preparing carbon fiber- (Ti, V) (C, N) cemented carbide according to any one of claims 1 to 6, characterized in that it essentially comprises the following steps:

step 1, mixing Ti in proportion_xV_1-xPerforming wet ball milling on CN powder, carbon fiber and a metal adhesive, uniformly mixing, and drying to obtain a mixture;

step 2, pressing and forming the mixture obtained in the step 1 to obtain a formed biscuit;

and 3, sintering the formed biscuit prepared in the step 2 in a vacuum hot-pressing sintering furnace, controlling the pressure in the hot-pressing sintering furnace to be 15GPa-20GPa, the sintering temperature to be 1350 ℃ to 1600 ℃, and the sintering time to be 30min to 60min, thus obtaining the carbon fiber- (Ti, V) (C, N) hard alloy after sintering.

9. The method for preparing carbon fiber- (Ti, V) (C, N) cemented carbide according to claim 8, wherein the sintering temperature is 1450 ℃ to 1550 ℃.

10. The method for preparing carbon fiber- (Ti, V) (C, N) cemented carbide according to claim 8, wherein the sintering time is 40-50 min.

Technical Field

The invention relates to the technical field of hard alloy processing, in particular to carbon fiber- (Ti, V) (C, N) hard alloy and a preparation method thereof.

Background

The cemented carbide can be divided into two major categories, one is tungsten-based cemented carbide (WC), which is the mainstream of cemented carbide at home and abroad, and the other is titanium-based cemented carbide (TiC or TiCN), which is also called cermet. The hard alloy has extremely high hardness, strength, wear resistance and corrosion resistance, is known as 'industrial teeth', is widely applied to the fields of tools, cutters, molds, drilling tools and the like, and is an important component element which cannot be lacked in intelligent manufacturing. However, tungsten resources in China are gradually exhausted, cost is saved and increased, and tungsten is saved and replaced, which becomes the first major thing of the hard alloy industry. Meanwhile, in the field of high-end titanium-based hard alloy materials, the unique gap exists between the Sandvik company in Sweden and the Kenn metal company, the Israel Oncar (Oscar) company and the like, the domestic technology has a large gap, China has to import a large amount of materials every year, and the development of the domestic intelligent manufacturing industry is severely restricted. The solution to the problem is not based on the following two approaches, namely, the improvement of the service efficiency and the service life of the existing tungsten-based hard alloy and the development of the titanium-based hard alloy to replace the tungsten-based hard alloy.

Titanium-based cemented carbide (TiC or TiCN), also known as cermet. Since TiC is found to be applicable to tool and die cemented carbide materials, a large number of basic and application studies have been conducted at home and abroad by adding (non) alloying elements, changing the preparation process, selecting cheap (high-quality) raw materials, subdividing the application field and the like, in view of the improvement of mechanical properties and physical properties and the reduction of manufacturing cost. TiC is a steel gray crystal with metallic luster, and its excellent properties make it the most preferred cemented carbide material to replace WC. Ti (C, N) -based metal ceramics are developed on the basis of TiC-based metal ceramics.

In the application and research and development process of the existing titanium-based hard alloy, Ti (C, N) becomes the mainstream material of the titanium-based hard alloy and is mainly applied to cutter cutting materials. The Ti (C, N) base hard alloy cutter has better wear resistance, size precision and surface quality than the workpiece processed by WC or TiC base hard alloy cutter. Nevertheless, the impact toughness of Ti (C, N) is still significantly inferior to that of tungsten-based cemented carbide, especially the resistance to plastic deformation, and thus the application field is severely limited, which has become a key obstacle for widely replacing tungsten-based cemented carbide with titanium-based cemented carbide. Therefore, the development of new materials for the high-toughness titanium-based hard alloy tool and die is urgent, and the method has great significance for the development of equipment manufacturing industry in China.

Disclosure of Invention

The invention aims to: aiming at the problems that the hardness and the strength of the titanium-based hard alloy in the prior art can be comparable with those of tungsten-based alloy, but the impact toughness of the titanium-based alloy is not as good as that of the tungsten-based hard alloy, so that the tungsten-based hard alloy is difficult to replace by the titanium-based hard alloy.

Therefore, the invention provides a carbon fiber- (Ti, V) (C, N) hard alloy and a preparation method thereof. The hard alloy not only keeps the original high strength performance of the titanium-based hard alloy, but also is superior to the tungsten-based hard alloy in impact toughness, and the preparation method is simple.

In order to achieve the purpose, the invention provides the following technical scheme:

a carbon fiber- (Ti, V) (C, N) hard alloy comprises the following components in percentage by weight:

Ti_xV_1-x78 to 87 percent of CN powder;

1% -5% of carbon fiber;

10% -20% of metal binder;

wherein, the Ti_xV_1-xThe value range of x in the CN powder is 0.6-0.9.

The carbon fiber has the outstanding performances of high strength, low density, high modulus and the like, and also has the characteristics of high temperature resistance (can be used at 2000 ℃), acid resistance, small thermal expansion coefficient, anisotropy, high thermal conductivity (about 10-140 w/(m.k)), small friction coefficient, good electrical conductivity and the like. The carbon fiber composite material is a novel solid material, and is formed by taking carbon fibers as a reinforcement and carbon, resin, ceramic and metal as matrixes. The carbon fiber composite material has the advantages of low density, high specific modulus, high specific strength, high thermal stability, good high-temperature performance and designability. Due to the excellent performance of the carbon fiber composite material, the carbon fiber composite material is widely applied to the fields of aviation, stealth, electromagnetic shielding, biology, building engineering, transportation, sports equipment and the like. The carbon fiber reinforced ceramic-based composite material has good chemical, physical and mechanical properties and is widely concerned by researchers at home and abroad.

According to the invention, the carbon fiber material is introduced, the toughness of the whole hard alloy is enhanced by utilizing a toughening mechanism of carbon fiber breaking and pulling, the idea of the traditional trace additive is broken by aiming at the problem of weakening the strength of the Ti (C, N) alloy material toughened by the C fiber, a grain refiner VC is taken as a main phase and is blended into the Ti (C, N) alloy, the bending strength and the hardness of the material are improved by refining grains, the strong potential effect of carbon fiber-VC main body synergistic toughening and reinforcement is formed, and the carbon fiber- (Ti, V) (C, N) hard alloy which is superior to the tungsten-based hard alloy in impact toughness is prepared.

Further, the carbon fiber accounts for 1% -3% of the total mass of the hard alloy. Preferably, the carbon fiber accounts for 1.8-2.2% of the total mass of the hard alloy. Preferably, the carbon fibers account for 2.0% of the total mass of the cemented carbide. The toughness of the whole hard alloy can be enhanced by utilizing a toughening mechanism of carbon fiber breaking and pulling. Experiments prove that the carbon fiber content is increased from 1 wt.% to 3 wt.%, the hard alloy has higher bending strength and fracture toughness, the change trends of the hard alloy are the same, the hard alloy gradually decreases after reaching the optimal value in the first rising trend, and the total performance of the hard alloy is the best at the addition amount ranging from 1.8% to 2.2%. The improvement of fracture toughness is mainly because the carbon fiber absorbs the energy of the crack tip so as to hinder the extension of the crack, and meanwhile, the extraction and bridging action of the carbon fiber increases the energy consumed when the crack is expanded. When the content of the fiber is too large, the bonding force between grain boundaries is low, and thus the fracture toughness is decreased.

Further, the length of the carbon fiber is 20 to 1500 micrometers, and preferably, the length of the carbon fiber is 200 to 1000 micrometers. Preferably, the carbon fibers have a length of 200 to 500 micrometers. The short carbon fiber has obvious toughening effect, and the fiber breaking and pulling out are the main toughening mechanism of the composite material. When the length is less than 200 microns, the length of the carbon fiber is limited to have certain influence on the fiber breaking effect, so that the toughness strength cannot be greatly increased, the length is too long, the fiber breaking and pulling-out effect can be influenced on the contrary by excessive overlapping of the carbon fiber in the hard alloy, and the overall toughness of the hard alloy is reduced.

Further, the metal binder is one or more of cobalt, nickel, molybdenum, chromium and manganese.

Preferably, the bonding metal is one or a mixture of two of metal molybdenum and metal nickel, preferably, the bonding metal is metal molybdenum and metal nickel, the metal molybdenum accounts for 4-8% of the total mass of the hard alloy, and the metal nickel accounts for 6-12% of the total mass of the hard alloy.

Further, said Ti_xV_1-xThe value of x in the CN powder is 0.75-0.85.

The invention also provides a preparation method of the carbon fiber- (Ti, V) (C, N) hard alloy.

The preparation method of the carbon fiber- (Ti, V) (C, N) hard alloy mainly comprises the following steps:

step 1, mixing Ti according to a proportion_xV_1-xAnd performing wet ball milling on CN powder, carbon fiber and a metal adhesive, uniformly mixing, and drying to obtain a mixture.

And 2, pressing and forming the mixture obtained in the step 1 to obtain a formed biscuit.

And 3, sintering the formed biscuit prepared in the step 2 in a vacuum hot-pressing sintering furnace, controlling the pressure in the hot-pressing sintering furnace to be 15-20 GPa, the sintering temperature to be 1350-1550 ℃, and the sintering time to be 25-70 min, and sintering to obtain the carbon fiber- (Ti, V) (C, N) hard alloy.

The invention uses Ti_xV_1-xCN powder is used as a hard phase, carbon fiber is used as an additive, bonding metal is used as a bonding agent, the materials are uniformly mixed and dried through wet ball milling, then the mixture is pressed and formed, and finally the hard alloy is obtained after vacuum sintering. The method is simple and convenient to operate.

And (4) reference of periodicals: chenmin, Xiao Xuan, ren Jie, et al.Ti_xV_1-xMicrostructure and mechanical properties of CN-based cermet [ J ]]The mechanical engineering material 2016,40(5):31-34.

Further, the value of x is Ti of 0.6-0.9_xV_1-xThe preparation method of the CN powder comprises the following steps:

step a, Ti with the value of x being 0.6-0.9_xV_1-xAtomic ratio of CN powder ammonium metavanadate (NH) was weighed₄VO₃) Titanium dioxide (TiO)₂) And uniformly mixing the graphite powder in a mixer to obtain a mixed material.

And step b, pressing and forming the mixture obtained in the step a in a hydraulic press to obtain a pressed blank.

Step c, placing the pressed blank obtained in the step b into a tubular furnace, introducing nitrogen, carrying out carbothermic reduction reaction, controlling the reaction temperature to 1530-1600 ℃, and the reaction time to be 1.5-2 h, and finally obtaining Ti_xV_1-xCN solid solution powder.

Step d, Ti obtained in the step c_xV_1-xCrushing and screening CN solid solution powder to obtain Ti_xV_1-xAnd (3) CN powder.

Further, said Ti_xV_1-xThe value of x in the CN powder is 0.75-0.85.

Further, the length of the carbon fiber is 20 to 1500 micrometers, and preferably, the length of the carbon fiber is 200 to 1000 micrometers. Preferably, the carbon fibers have a length of 200 to 500 micrometers. The short carbon fiber has obvious toughening effect, and the fiber breaking and pulling out are the main toughening mechanism of the composite material. When the length is less than 200 microns, the length of the carbon fiber is limited to have certain influence on the fiber breaking effect, so that the toughness strength cannot be greatly increased, the length is too long, the fiber breaking and pulling-out effect can be influenced on the contrary by excessive overlapping of the carbon fiber in the hard alloy, and the overall toughness of the hard alloy is reduced.

Further, the wet ball milling equipment is a rolling ball mill or a stirring ball mill.

Furthermore, the hard alloy balls are added during the wet ball milling process, so that the materials are mixed more fully and uniformly.

Further, the mass ratio of the ball materials is 3-8: 1. The larger the mass ratio of the ball to the material is, the larger the contact area of the ball and the material is, and the higher the ball milling efficiency is.

Further, the rotating speed of the wet ball milling is 150r.min^-1-500r.min^-1Preferably, the rotation speed of the wet ball milling is 300r.min^-1-500r.min^-1。

Further, the medium for wet ball milling in step 1 is one or more of absolute ethyl alcohol, acetone and hexane. The addition of the medium prevents agglomeration of the powder material during the ball milling process.

Further, the equipment for pressing and forming the mixture in the step 2 is a hydraulic press.

Further, in the step 2, the pressure of the compression molding is 150MPa-350 MPa.

Preferably, the sintering temperature is 1450-1550 ℃, and preferably, the sintering temperature is 1500 ℃. When the sintering temperature is lower than 1450 ℃, the driving force is relatively small, the atoms are difficult to move, the liquid phase has relatively weak capacity of filling gaps among solid particles, so that the structure is relatively loose, a large number of bubbles cannot be discharged, the binding force among the particles is relatively poor, the compactness is relatively low, and the corresponding mechanical property is relatively low. With the increase of sintering temperature, the atoms are caused to move rapidly due to the increase of mass transfer coefficient of the atoms, air holes are further discharged, the contact between crystal grains is gradually changed from point contact to surface contact, the bonding force between the particles becomes strong, in addition, the flowing of the metal binder is accelerated, the filling of pores is facilitated, and the density is improved. However, when the sintering temperature is higher than 1500 ℃, the diffusion rate is accelerated, the dissolution-precipitation process is accelerated, and the growth of crystal grains is caused, so that the mechanical property is also reduced.

Preferably, the sintering time is 40min to 50 min. Preferably, the sintering time is 45 min. With the properly prolonged sintering time, the liquid phase formed by the metal binder is gradually increased, and the sliding and rearrangement of the crystal grains are gradually sufficient, so that the compactness of the hard alloy material is improved. When the sintering time reaches a certain period of time, the size of the crystal grains becomes significantly large, and the mechanical properties are reduced due to the coarse crystal grains. With the extension of sintering time, the coarsening phenomenon of the crystal grains of the carbon fiber- (Ti, V) (C, N) hard alloy is serious, and the performance of the composite material is reduced by the coarse crystal grains.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. the carbon fiber- (Ti, V) (C, N) hard alloy provided by the invention introduces the carbon fiber material, utilizes a toughening mechanism of carbon fiber breaking and pulling out to enhance the integral toughness of the hard alloy, overcomes the functional limitation of adding Mo, W, Ta, V, Nb and other alloy elements in the prior art, obviously improves the flexibility of the Ti (C, N) base hard alloy widely used in the field of equipment manufacturing and production at present, and improves the anti-edge-jumping capability of functional processing appliances.

2. The carbon fiber- (Ti, V) (C, N) hard alloy provided by the invention solves the problem of weakening strength of a Ti (C, N) alloy material toughened by C fibers, breaks through the idea of the traditional trace additive, and fuses a grain refining agent VC into the Ti (C, N) alloy as a main phase, so that the finally obtained chopped C fiber- (Ti, V) (C, N) hard alloy keeps inherent high strength performance and meets the requirement of high strength mechanical performance of an intelligent manufacturing and processing device.

3. The invention uses Ti_xV_1－xCN powder is used as a hard phase, carbon fiber is used as an additive, bonding metal is used as a binder, the materials are uniformly mixed and dried through wet ball milling, and then the mixture is pressed and formed to obtain a formed crude product of the hard alloy.

4. The fracture toughness of the carbon fiber- (Ti, V) (C, N) hard alloy provided by the invention reaches 13.5 MPa.m^1/2The hardness is above 14GPa, the bending strength is above 900MPa, and a solid foundation is laid for development and application of the die device for intelligent manufacturing.

Drawings

FIG. 1 shows a preparation process of the carbon fiber- (Ti, V) (C, N) hard alloy of the invention.

Detailed Description

The present invention will be described in detail with reference to fig. 1.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.