CN112680646B - Preparation method of TiC-based metal ceramic with high-entropy alloy binder phase - Google Patents

Abstract

The invention relates to the field of powder metallurgy and multi-principal element high-entropy alloy materials, in particular to a method for preparing a metal-ceramic composite material with a high-entropy alloy binding phase. The TiC-based cermet material with high-entropy alloy binder phase prepared by the invention is characterized in that the binder phase is high-entropy alloy NiCoCrMoWTi, and the mole fraction of each component is Ni: 30.0-35.0%, Co: 10.0-35.0% , Cr: 5.0~20.0%, Mo: 5.0~20.0%, W: 5.0~15.0%, Ti: 5.0~35.0%, the sum of the mole fractions of each component is 100%. The TiC-based cermet with the high-entropy alloy binding phase prepared by the invention has higher strength, hardness, wear resistance and oxidation resistance, and the TiC ceramic phase is precipitated in-situ during the preparation process, so as to refine the sintering The grain size of the body, the interface between the binder phase and the hard phase of the sintered body have a coherent relationship.

Description

Preparation method of TiC-based cermet with high-entropy alloy binder phase

technical field

The invention relates to the fields of mechanical processing and powder metallurgy, in particular to a preparation method of a TiC-based cermet with a high-entropy alloy binding phase.

Background technique

As a new type of multi-principal alloy material, high-entropy alloys have simple body-centered or face-centered solid solution structures. High-entropy alloys have high entropy values that ordinary alloys do not have, so high-entropy alloys have excellent mechanical properties that ordinary alloys do not have, including high hardness, high strength, good ductility, excellent wear resistance and corrosion resistance. Wait.

TiC-based cermet materials are composed of two phases, a hard phase and a binder phase. The binder phase is usually a Ni or Co-based solid solution alloy, which is the plastic-ductile structural unit of the cermet material. The traditional preparation method of cermet sintered body is to mix ceramic powder and metal element powder in proportion and then ball milling; ceramic powder has high hardness, so in the process of mixing ball milling, a large part of the impact energy of the grinding ball is absorbed and further refined. ; The degree of work hardening of metal powder during ball milling is not high. The binder phase in the cermet sintered body is a metal solid solution formed by the dissolution and diffusion of solute elements in the binder phase metal solvent during the solid phase and liquid phase sintering stages. The dissolution, precipitation and diffusion of solute elements in the solvent will produce some intermediate process chemical reactions. The control of intermediate process chemical reactions and their influence on the final structure can usually only be inferred theoretically. Therefore, the final sintering performance and mechanical properties of powder metallurgy products are important Control becomes more complex.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention provides a preparation method for a TiC-based cermet with a high-entropy alloy binder phase.

Scheme of the present invention:

A TiC-based cermet material with a high-entropy alloy binding phase, the material includes a hard phase and a binding phase, the binding phase is a high-entropy alloy, and the binding phase component is Ni-Co-Cr-Mo- W—Ti; the chemical formula of the hard phase is (Ti, M)C and (Ti, M)(C, N), wherein M is selected from the combination of one or more of W, Mo, and Cr.

Preferably, the molar fraction of each component of the binder phase is Ni: 30.0-35.0%, Co: 10.0-35.0%, Cr: 5.0-20.0%, Mo: 5.0-20.0%, W: 5.0-15.0%, Ti: 5.0~35.0%; the sum of the mole fractions of each component is 100%.

Preferably, the raw materials of the hard phase include: one or more combinations of TiC, Ti(C, N), (Ti, W)C, Mo ₂ C powder, and Cr ₃ C ₂ powder.

Preferably, the raw material components of the cermet material, in terms of mass percentage, include 20-36 wt.% of the binder phase powder and 64-80 wt.% of the ceramic powder.

The method for preparing the TiC-based cermet material is as follows: using a high-energy ball milling method to prepare a high-energy-storage bonding phase alloy mixed powder, and then mixing with the ceramic powder to prepare a cermet mixed material.

Preferably, the following steps are included:

1) Ball milling Co, Cr, Ni, Mo, W and Ti powders according to molar ratio to obtain a high energy storage alloy mixture;

2) The alloy mixture and ceramic powder obtained in 1) are batched and ball-milled to further obtain a cermet mixture;

3) The cermet mixture is pressed to obtain a green compact;

4) The compact is fired into a vacuum sintering furnace;

5) Cooling after sintering;

The preparation of TiC-based cermet material is completed.

Preferably, carbon powder with a molar fraction of 2.8-8.6% is added to the bonding phase alloy mixture in the step 1) to deoxidize and in-situ precipitate TiC and its composite carbides during the sintering process.

Preferably, the step 1) adopts a planetary ball milling process, the ratio of ball to material is (8~12): 1, anhydrous ethanol is used as the dispersion medium, and the ratio of alcohol to material is (30~35): 100 (L/kg) , the speed is 225~300r/min, and the ball milling time is 60~72 hours.

Preferably, the morphology of the mixture obtained in the step 1) is a flake-shaped high-energy alloy mixed powder with high work hardening characteristics. The morphology of the obtained mixture is a flake active alloy mixed powder with high work hardening characteristics (the half-width of the XRD diffraction peak of the obtained mixed powder is significantly broadened, which is specifically described in Example 1).

Preferably, the step 2) adopts wet ball milling, the ratio of ball to material is (5~7): 1, anhydrous ethanol is used as the dispersion medium, the ratio of alcohol to material is (60~70): 100, and the rotation speed is 211~225r/ min, the ball milling time is 24 to 36 hours. The binder phase powder undergoes strong plastic deformation and work hardening during the ball milling process. The energy input of the ball milling increases the energy storage of the mixed powder, and some solid solutions are formed during the ball milling process.

Preferably, the step 4) adopts a vacuum liquid phase sintering process, the sintering temperature is 1370-1400°C, and the vacuum degree during the sintering process is 10 ^-1 -10 ^-3 Pa.

The present invention firstly adopts the planetary ball milling method to prepare high-energy bonding phase alloy powder, and the high-energy plastic metal mixed powder further increases energy storage and entropy value during the mixing process of cermet materials, so as to prepare high-entropy alloy bonding phase alloy powder. The TiC-based cermet, the preparation method can greatly promote the sintering properties of the cermet material, reduce the sintering temperature, save energy and reduce the loss of sintering equipment. At the same time, fine-grained composite carbide particles are formed in-situ during sintering, which can reduce the grain size of the material. And due to the high content of solute elements in the binder phase alloy, it can inhibit the dissolution of the hard phase in the binder phase and promote the formation of the composite carbide hard phase, making the design process of the volume fraction and mechanical properties of the cermet two-phase more accurate. , the sintering process is also more controllable. The sintered body prepared by this process has a higher combination of mechanical properties.

The molar ratio of each element in the binder phase alloy is between 5% and 35%. The preparation method can better improve the sintering properties and final mechanical properties of the sintered body. The structure of the obtained sintered body is a typical cermet structure without defects such as pores. As shown in Figure 1, the hard phase particles have a typical core-shell structure, and the hard phase contains two types: "white core-gray shell" and "white core-grey shell" Black core-white shell" hard phase. The quality of the preparation process is stable.

Beneficial effects of the present invention:

1. The present invention prepares the high-entropy alloy binder phase mixture powder by the planetary ball milling method, and the binder phase alloy mixture powder has high energy storage and work hardening characteristics, thereby greatly improving the sintering performance of the cermet sintered body , reduce the sintering temperature, is a more energy-saving preparation process.

2. The cermet powder prepared by the present invention can form a large number of fine "white core-grey shell" hard phase particles in situ during the sintering process, which promotes the refinement of the hard phase particles of the sintered body.

3. The cermet material with the high-entropy alloy binder phase prepared by the present invention has a higher mechanical property combination of hardness, flexural strength and fracture toughness.

Description of drawings

Fig. 1 is the SEM structure of the cermet sintered body of Example 1;

Fig. 2 is the SEM morphology of the highly work-hardened state binder phase powder of Example 1;

Fig. 3 is the XRD pattern of the binder phase mixture powder of Example 1;

Fig. 4 is the XRD pattern of the cermet sintered body of Example 1;

5 is an EBSD orientation diagram of the cermet sintered body of Example 1, and an inverse pole diagram of a hard phase and a binder phase.

Detailed ways

The present invention will be further described below in conjunction with the embodiments, but the claimed scope of the present invention is not limited to the scope expressed by the embodiments.

Example 1

A preparation method of a TiC-based cermet material with a high-entropy alloy binder phase, comprising the following steps:

1) It is the preparation of high energy storage alloy mixture: Ni powder, Co powder, Cr powder, Mo powder, Ti powder, W powder, carbon powder and other raw materials are used, and the molar fraction of the configuration materials is Ni: 30%, Co: 30 %, Cr: 10%, Mo: 10%, W: 5%, Ti: 15% of the mixture, an additional 3.8% mole fraction of carbon powder is added to the mixture to remove oxygen in the mixture and promote the sintering process. In-situ precipitation of titanium carbide and its composite carbide; using absolute ethanol as the dispersion medium, the amount of absolute ethanol is the ratio of alcohol to material ratio of 30:100, YG8 cemented carbide balls are grinding balls, and the ratio of ball to material is 30:100. 10:1; mixing on a planetary ball mill, rotating speed 280r/min, time 60h;

2) Add ceramic powder to the mixture twice, and configure the material mass fraction as follows: ceramic powder 78wt.%, high-energy alloy mixed powder 22wt.%; secondary addition of absolute ethanol to prepare alcohol-to-material ratio of 70: The ratio of 100; mix the materials on a planetary ball mill, the speed is 210r/min, the time is 36h, and the mixed slurry is dried in an oven at 80 °C to obtain a cermet mixed powder;

3) The cermet mixed powder is pressed and formed under a certain pressure (160MPa);

4) The compact is placed in a vacuum carbon tube furnace for vacuum sintering. The vacuum degree in the furnace below 1000°C is 4.0×10 ^-2 Pa; above 1000°C, the staged sintering process is adopted, and the secondary heat preservation is performed at 1280°C and 1350°C respectively, and the holding time is 90min and 20min respectively; sintering The temperature is 1390°C for 60min;

5) Then the furnace is cooled to room temperature, and the vacuum degree in the cooling stage is 1.0×10 ^-3 ~1.0×10 ^-2 Pa.

Figure 1 shows the high-magnification SEM structure of the cermet sintered body. From the figure, it can be found that a large number of fine "white core-grey shell" hard phase particles appear in the matrix. Figure 2 shows the SEM morphology of the flake alloy mixture obtained in this example. It can be seen that the metal mixture undergoes a series of behaviors such as relatively severe plastic deformation, work hardening, welding and fracture during the ball milling process. The mixture formed a flat powder. The alloy mixture was mixed for 30min as the initial raw material and the phase of the mixture after mixing for 60h was subjected to XRD analysis, and the phase XRD pattern was shown in Figure 3. Compared with the initial raw materials, the diffraction peaks of the metal components were significantly broadened after mixing for 60 hours, and the diffraction peaks of some metals disappeared, which proved that some solid solution alloys had been formed during the ball milling process. The half-widths of the (110) _Mo diffraction peak at a diffraction angle of 40.5° and the (002) _Co diffraction peak at 44.8° are broadened by 203% and 261%, respectively, indicating that the alloy powder undergoes severe work hardening during the ball milling process. . Due to the input of the collision energy of the grinding ball, the metal bonding phase undergoes severe plastic deformation and work hardening to form a flat powder, which greatly improves the energy storage and surface energy of the powder. Therefore, a lower sintering temperature can be used in the subsequent sintering process. . Figure 4 shows the XRD pattern of the cermet sintered body, which proves that the sintered body consists of two phases: a TiC hard phase and a Ni-based binder phase, both of which have a face-centered cubic lattice structure. Figure 5 shows the EBSD orientation distribution diagram of the cermet sintered body and the inverse pole diagram of the TiC hard phase and the Ni-based bonding phase. It can be seen that the core-shell structure of the hard phase is in a completely coherent relationship. The orientation distribution of the hard phase and the binder phase is mainly concentrated in [101], that is, there is a high coherence relationship between the two, which is further confirmed by TEM and high resolution.

The image analysis shows that the volume fractions of the hard phase and the binder phase are 85.8% and 14.2%, respectively, and the volume fraction of the hard phase "white core-grey shell" hard phase particles is 5.7%; the average crystallinity of the sintered body. The particle size was 0.56 μm. The molar contents of elements in the binder phase formed by energy spectrum analysis are Co: 30.5%, Cr: 9.3%, Ni: 33.4%, Mo: 9.4%, W: 3.6%, Ti: 13.8%. The mole fraction of carbide-forming elements is reduced compared to the binder phase alloy raw material composition. It can be seen that TiC in the binder phase precipitates in-situ during the sintering process, and Mo, W, and Cr diffuse to the in-situ precipitated TiC and the original hard phase particles to form composite carbides. The mechanical property indexes of the obtained sintered body are: hardness 1735HV, flexural strength 1856MPa, fracture toughness K _IC 10.6MPa·m ^1/2 .

Example 2

The component combination, mixing method, preparation process and sintering route of Example 1 were adopted. In Example 2, the second step of adding ceramic powder is not used in the preparation of the binder phase mixture, that is, the method of directly adding the ceramic powder to the binder phase wet material in the second step of Example 1 is not used. Instead, the mixed slurry of the binder phase alloy is obtained and then dried in an oven at 80°C and sieved for use. Then, it is further configured into a metal-ceramic mixture with a material mass fraction of 78 wt.% of the ceramic powder and 22 wt.% of the active alloy mixed powder; the mixing method of the mixture is the same as that of Example 1.

After analysis, the morphology of the alloy mixture and the cermet mixture after ball milling is not clearly different. The metallographic structure and scanning structure of the sintered body have no other phases, and are typical two-phase structures of cermets, which are the same as those obtained in Example 1. The image analysis shows that the volume fraction of the two phases and the volume ratio of the hard phase "white core-grey shell" hard phase particles are similar to those in the examples. The mechanical properties of the sintered body are as follows: hardness 1695HV, flexural strength 1944MPa, fracture toughness K _IC 11.1MPa·m ^1/2 . Compared with Example 1, the adjustment of the mixing route and the drying process of the alloy mixed slurry have a certain softening effect on the work hardening of the mixture, but have no significant effect on the mechanical properties of the cermet sintered body. The hardness decreased slightly, and the transverse fracture strength and fracture toughness increased slightly.

Example 3

Change the ratio of the binder phase mixture, and configure the molar ratio of the materials as Ni: 35.0%, Co: 10.0%, Cr: 5.0%, Mo: 13.0%, W: 7.0%, Ti: 30.0% mixture, mixture Add an additional 8.0% mole fraction of toner. The mass fraction of the metal-ceramic mixture is as follows: a mixture of 68 wt.% ceramic powder and 32 wt.% high-energy-storage alloy mixed powder. The mixing process and sintering route are the same as those in Example 1, and the mixing time is extended to 72h.

After analysis, the morphology of the alloy mixture after the ball milling process is still flat, and the particle size of the mixture tested by the laser particle size analyzer has little change compared with Example 1. The plastic deformation, work hardening, welding and fracture of the material reach an equilibrium state. Phase analysis by XRD found no new phase formed. The metallographic structure and scanning structure of the obtained sintered body also have no other phase formation, which is a typical two-phase structure of cermet. The image analysis shows that the volume fractions of the hard phase and the binder phase are 77.8% and 22.2%, respectively; the volume fraction of the hard phase "white core-grey shell" particles is 7.8%; the average crystallinity of the sintered body is 7.8%. The grain size is 0.41 μm, the average grain size is further refined than that of Example 1, and it can be seen that there is a lot of titanium carbide precipitation in the binder phase. The molar contents of elements in the binder phase formed by energy spectrum analysis are Ni: 36.8%, Ti: 29.3%, Co: 18.1%, Cr: 3.5%, Mo: 7.8%, W: 4.6%. The mechanical properties of the obtained sintered body are as follows: hardness 1625HV, flexural strength 2356MPa, fracture toughness K _IC 12.7MPa·m ^1/2 .

It can be seen that although the mass fraction of hard phase carbides in the cermet mixture decreases, due to the in-situ precipitation of TiC and the formation of composite carbides during sintering, the volume fraction of hard phase in the sintered body is 81.8% higher than the theoretically calculated volume fraction value. , again demonstrating the in-situ precipitation process of TiC during sintering. The increase in the volume fraction of the binder phase improves the flexural strength and fracture toughness.

The above-mentioned embodiments are only the preferred technical solutions of the present invention, and should not be regarded as limitations of the present invention. The protection scope of the present invention should be based on the technical solutions described in the claims, including the equivalents of the technical features in the technical solutions described in the claims. The alternative is protection scope. That is, equivalent replacements and improvements within this scope are also within the protection scope of the present invention.

Claims (5)

1. A preparation method of TiC-based metal ceramic material with high-entropy alloy binder phase is characterized by comprising the following steps: the material comprises a hard phase and a binding phase, wherein the binding phase is high-entropy alloy, and a component of the binding phase is Ni-Co-Cr-Mo-W-Ti; the chemical formulas of the hard phase are (Ti, M) C and (Ti, M) (C, N), wherein M is selected from one or more of W, Mo and Cr; the mole fraction of each component of the binding phase is Ni: 30.0-35.0%, Co: 10.0-35.0%, Cr: 5.0-20.0%, Mo: 5.0-20.0%, W: 5.0-15.0%, Ti: 5.0-35.0%; the sum of the mole fractions of all the components is 100 percent; the raw materials of the hard phase include: TiC, Ti (C, N), (Ti, W) C, Mo₂C powder and Cr powder₃C₂One or more combinations of powders;

the method comprises the following steps: the preparation method comprises the following steps of preparing high-energy storage bonding phase alloy mixed powder by adopting a high-energy ball milling method, and mixing the high-energy storage bonding phase alloy mixed powder with ceramic powder to prepare a metal ceramic mixture:

1) mixing Co, Cr, Ni, Mo, W and Ti powder according to a molar ratio, and carrying out ball milling to obtain a high energy storage alloy mixture;

2) mixing the alloy mixture obtained in the step 1) with ceramic powder, and performing ball milling to further obtain a metal ceramic mixture;

3) pressing the metal ceramic mixture to obtain a pressed blank;

4) firing and forming the pressed compact in a vacuum sintering furnace;

5) cooling after sintering;

completing the preparation of the TiC-based metal ceramic material;

the step 1) adopts a planetary ball milling process, and the ball-material ratio is (8-12): 1, adopting absolute ethyl alcohol as a dispersion medium, wherein the alcohol-material ratio is (30-35): 100L/kg, the rotating speed is 225-300 r/min, and the ball milling time is 60-72 hours;

and (2) adding carbon powder with the mole fraction of 2.8-8.6% into the bonding phase alloy mixture in the step 1), and deoxidizing and in-situ precipitating TiC and composite carbide thereof in the sintering process.

2. A TiC-based cermet material with high-entropy alloy binder phase as claimed in claim 1, wherein the cermet material comprises 20-36 wt.% binder phase powder and 64-80 wt.% ceramic powder.

3. A method for preparing TiC-based cermet material with high entropy alloy binder phase as claimed in claim 1, characterized by: the shape of the mixture obtained in the step 1) is sheet alloy mixed powder.

4. A method for preparing TiC-based cermet material with high entropy alloy binder phase as claimed in claim 1, characterized by: and 2) ball milling by a wet method is adopted, and the ball-material ratio is (5-7): 1, adopting absolute ethyl alcohol as a dispersion medium, wherein the alcohol-material ratio is (60-70): 100L/kg, the rotating speed of 211-225 r/min and the ball milling time of 24-36 hours.

5. A method for preparing TiC-based cermet material with high entropy alloy binder phase as claimed in claim 1, characterized by: the step 4) adopts a vacuum liquid phase sintering process, the sintering temperature is 1370-1400 ℃, and the vacuum degree in the sintering process is 10^-1~10^-3Pa。

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