阅读说明：本技术 具有高熵合金粘结相的TiC基金属陶瓷的制备方法 (Preparation method of TiC-based metal ceramic with high-entropy alloy binder phase ) 是由 石增敏 王杨洋 张大勇 杨蔚华 方子帆 于 2020-12-03 设计创作，主要内容包括：本发明涉及粉末冶金和多主元髙熵合金材料领域,特别涉及制备具有髙熵合金粘结相的金属陶瓷复合材料的方法。本发明制备的具有高熵合金粘结相的TiC基金属陶瓷材料,其特征在于粘结相为高熵合金NiCoCrMoWTi,各组元的摩尔分数为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%,各组元的摩尔分数之和为100%。本发明所制备的具有高熵合金粘结相的TiC基金属陶瓷具有更高的强度、硬度、耐磨性和抗氧化性能,制备工艺过程中有TiC陶瓷相的原位析出,从而细化烧结体的晶粒度,烧结体的粘结相和硬质相之间的界面具有共格关系。(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 binder phase. The TiC-based metal ceramic material with the high-entropy alloy binding phase is characterized in that the binding 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%, and the sum of the mole fractions of all the components is 100%. The TiC-based metal ceramic with the high-entropy alloy binder phase has higher strength, hardness, wear resistance and oxidation resistance, and the TiC ceramic phase is precipitated in situ in the preparation process, so that the grain size of a sintered body is refined, and the interface between the binder phase and the hard phase of the sintered body has a coherent relationship.)

1. A TiC-based metal ceramic material with a high-entropy alloy binder phase is characterized in that: 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.

2. TiC-based cermet material with high entropy alloy binder phase according to claim 1, characterized in that: 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.

3. Alloy with high entropy according to claim 1The TiC-based cermet material with the binder phase is characterized in that the hard phase comprises the following raw materials: TiC, Ti (C, N), (Ti, W) C, Mo₂C powder and Cr powder₃C₂One or more combinations of powders.

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

5. A method of preparing a TiC-based cermet material as claimed in any one of claims 1 to 4, characterized in that said method comprises: preparing high-energy storage bonding phase alloy mixed powder by adopting a high-energy ball milling method, and then mixing the high-energy storage bonding phase alloy mixed powder with ceramic powder to prepare a metal ceramic mixture;

the high-energy ball milling method comprises the following steps: the planetary ball milling process comprises the following steps of (8-12): 1, adopting absolute ethyl alcohol as a dispersion medium, wherein the alcohol-material ratio is (30-35): 100 (L/kg), 225-300 r/min of rotation speed and 60-72 hours of ball milling time.

6. The method of claim 5, comprising the steps of:

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;

and finishing the preparation of the TiC-based metal ceramic material.

7. The method of claim 6, wherein: 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.

8. The method of claim 6, wherein: the shape of the mixture obtained in the step 1) is sheet alloy mixed powder.

9. The method of claim 6, wherein: 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): 100, the rotating speed is 211-225 r/min, and the ball milling time is 24-36 hours.

10. The method of claim 6, wherein: 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。

Technical Field

The invention relates to the field of machining and powder metallurgy, in particular to a preparation method of TiC-based metal ceramic of a high-entropy alloy binder phase.

Background

The high-entropy alloy is used as a novel multi-principal-element alloy material and has a simple solid solution structure with a body center or a face center. The high-entropy alloy has a high-entropy value which is not possessed by common alloys, so that the high-entropy alloy has excellent mechanical properties which are not possessed by common alloys, including high hardness, high strength, good ductility, excellent wear resistance, excellent corrosion resistance and the like.

The TiC-based metal ceramic material consists of a hard phase and a binder phase. The binding phase is usually Ni or Co-based solid solution alloy, and is a plastic-toughness structural unit of the cermet material. The traditional preparation method of the metal ceramic sintered body is to ball mill ceramic powder and metal simple substance powder after being mixed according to a proportion; the ceramic powder has high hardness, so that a great part of impact energy of grinding balls is absorbed in the process of mixing and ball milling and further refined; the metal powder does not work harden to a high degree during ball milling. The binder phase in the sintered cermet body is a metal solid solution formed by dissolution and diffusion of solute elements in the binder phase metal solvent in the solid phase and liquid phase sintering stages. The dissolution, precipitation and diffusion of solute elements in a solvent can generate a plurality of chemical reactions in the intermediate process, and the control of the chemical reactions in the intermediate process and the influence of the chemical reactions on the final structure can only be theoretically deduced, so the control on the final sintering performance and the mechanical performance of the powder metallurgy product becomes more complex.

Disclosure of Invention

In order to solve the technical problems, the invention provides a preparation method of TiC-based metal ceramic with a high-entropy alloy binder phase.

The scheme of the invention is as follows:

a TiC-based metal ceramic material with a high-entropy alloy binding phase comprises a hard phase and a binding phase, wherein the binding phase is a 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.

Preferably, the mole 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 all the components is 100 percent.

Preferably, the starting materials for the hard phase include: TiC, Ti (C, N), (Ti, W) C, Mo₂C powder and Cr powder₃C₂One or more combinations of powders.

Preferably, the raw material components of the cermet material comprise, by mass, 20-36 wt.% of binder phase powder and 64-80 wt.% of ceramic powder.

The method for preparing the TiC-based metal ceramic material comprises the following steps: the high-energy-storage bonding phase alloy mixed powder is prepared by adopting a high-energy ball milling method and then is mixed with ceramic powder to prepare a metal ceramic mixture.

Preferably, the method comprises the following steps:

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;

and finishing the preparation of the TiC-based metal ceramic material.

Preferably, carbon powder with the mole fraction of 2.8-8.6% is added into the bonding phase alloy mixture in the step 1), and TiC and composite carbide thereof are deoxidized and precipitated in situ in the sintering process.

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

Preferably, the morphology of the mixture obtained in the step 1) is flaky high-energy alloy mixed powder with high work hardening characteristics. The morphology of the obtained mixture is the flaky active alloy mixed powder with high work hardening characteristics (the half-peak width of the XRD diffraction peak of the obtained mixed powder is obviously widened, and the specific description in the embodiment 1 is included).

Preferably, the step 2) adopts wet ball milling, and the ball-to-material ratio is (5-7): 1, adopting absolute ethyl alcohol as a dispersion medium, wherein the alcohol-material ratio is (60-70): 100, the rotating speed is 211-225 r/min, and the ball milling time is 24-36 hours. The bonding phase powder is subjected to strong plastic deformation and work hardening in the ball milling process, the energy storage of the mixed powder is increased due to the input of ball milling energy, and a part of solid solution is formed in the ball milling process.

Preferably, 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。

According to the invention, firstly, the high-energy bonding phase alloy powder is prepared by adopting a planetary ball milling method, and the energy storage and entropy value of the high-energy plastic metal mixed powder are further improved in the material mixing process of the metal ceramic material so as to prepare the TiC-based metal ceramic with the high-entropy alloy bonding phase. Meanwhile, fine-particle composite carbide particles are formed in situ in the sintering process, so that the grain size of the material can be reduced. And because the solute element content in the bonding phase alloy is high, the dissolution of the hard phase in the bonding phase can be inhibited, and the formation of the composite carbide hard phase is promoted, so that the design process of the volume fraction and the mechanical property of the two phases of the metal ceramic is more accurate, and the sintering process is more controllable. The sintered body prepared by the process method has higher mechanical property combination.

The mixing molar ratio of each element in the bonding phase alloy is 5-35%. The preparation method well improves the sintering performance and the final mechanical property of the sintered body. The obtained sintered body has a typical cermet structure and no defects such as pores, and as shown in fig. 1, hard phase particles have a typical core-shell structure, and the hard phase comprises two types: the "white core-gray shell" and the "black core-white shell" hard phases. The quality of the preparation process is stable.

The invention has the beneficial effects that:

1. the high-entropy alloy binder phase mixture powder is prepared by a planetary ball milling method, has high energy storage and work hardening characteristics, greatly improves the sintering performance of the metal ceramic sintered body, reduces the sintering temperature, and is a more energy-saving preparation process.

2. The metal ceramic powder prepared by the invention can form a large amount of fine 'white core-gray shell' hard phase particles in situ in the sintering process, and the refinement of the hard phase particles of the sintered body is promoted.

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

Drawings

FIG. 1 is an SEM structure of a sintered cermet body of example 1;

FIG. 2 is an SEM morphology of the high work hardened binder phase powder of example 1;

FIG. 3 is an XRD pattern of the binder phase mixture powder of example 1;

FIG. 4 is an XRD spectrum of the cermet sintered body of example 1;

FIG. 5 is an EBSD orientation chart of the cermet sintered body of example 1, and an inverse pole chart of the hard phase and the binder phase.

Detailed Description

The invention is further illustrated by the following examples, but the scope of the invention as claimed is not limited to the scope of the examples.

Example 1

A preparation method of TiC-based metal ceramic material with high-entropy alloy binder phase comprises the following steps:

1) the preparation method comprises the following steps of: adopting raw materials such as Ni powder, Co powder, Cr powder, Mo powder, Ti powder, W powder, carbon powder and the like, and preparing the material with the molar fraction of Ni: 30%, Co: 30%, Cr: 10%, Mo: 10%, W: 5%, Ti: 15 percent of mixture, wherein carbon powder with the mole fraction of 3.8 percent is additionally added into the mixture to remove oxygen in the mixture and promote in-situ precipitation of titanium carbide and composite carbide thereof in the sintering process; adopting absolute ethyl alcohol as a dispersion medium, wherein the dosage of the absolute ethyl alcohol is 30: 100, the YG8 hard alloy ball is a grinding ball, and the ratio of the ball to the material is 10: 1; mixing materials on a planetary ball mill at the rotating speed of 280r/min for 60 h;

2) adding ceramic powder into the mixture for the second time, and preparing the mixture into the following materials in percentage by mass: 78wt.% of ceramic powder, higher than 22wt.% of energy alloy mixed powder; and (3) preparing an alcohol-material ratio of 70 by adding absolute ethyl alcohol for the second time: a ratio of 100; mixing materials on a planetary ball mill at the rotating speed of 210r/min for 36h, mixing the slurry, and drying in an oven at the temperature of 80 ℃ to obtain metal ceramic mixed powder;

3) pressing the metal ceramic mixed powder into a shape under certain pressure (160 MPa);

4) and putting the pressed compact into a vacuum carbon tube furnace for vacuum sintering. The vacuum degree in the furnace is 4.0 multiplied by 10 below 1000 DEG C^-2Pa; performing secondary heat preservation at 1280 ℃ and 1350 ℃ by adopting a segmented sintering process at the temperature of more than 1000 ℃, wherein the heat preservation time is 90min and 20min respectively; keeping the sintering temperature at 1390 ℃ for 60 min;

5) then furnace cooling to room temperature, the vacuum degree in the cooling stage is 1.0 × 10^-3~1.0×10^-2Pa。

FIG. 1 is a high power SEM structure of a sintered cermet body from which it can be seen that a large number of fine "white core-gray shell" hard phase particles are present in the matrix. Fig. 2 shows the SEM morphology of the sheet alloy mixture obtained in this example, which shows that the metal mixture undergoes severe plastic deformation, work hardening, welding, fracture, and other series of actions during the ball milling process, and the mixture forms flat powder. XRD analysis was performed on the alloy mixture as the initial raw material when mixed for 30min and the phase of the mixture after 60h mixing, and the XRD pattern of the phase is shown in FIG. 3. Compared with the initial raw materials after mixing for 60h, the diffraction peaks of the metal components are obviously broadened, and the diffraction peaks of part of metals disappear, so that part of solid solution alloy is formed in the ball milling process. Diffraction angle at 40.5 ° (110)_MoDiffraction peak and (002) at 44.8 °_CoThe half-widths of the diffraction peaks are wide respectively203% and 261% were changed, and it was found that the alloy powder was strongly work hardened during the ball milling. Because of the input of the collision energy of the grinding balls, the metal bonding phase is severely plastically deformed and processed and hardened to form flat powder, the energy storage and the surface energy of the powder are greatly improved, and therefore, the sintering forming at lower sintering temperature can be carried out in the subsequent sintering process. Fig. 4 gives the XRD pattern of the sintered cermet body, demonstrating that the sintered body consists of two phases: TiC hard phase and Ni-based binding phase, both of which are face-centered cubic lattice structures. FIG. 5 shows an EBSD orientation distribution diagram of a cermet sintered body and an inverse diagram of a TiC hard phase and a Ni-based binder phase, and it can be seen that the core-shell structure of the hard phase is completely coherent, and the orientation distribution of the hard phase and the binder phase in the selected diagram is mainly concentrated on [101 ]]I.e., a higher coherent relationship between the two, which is further confirmed in TEM and high resolution.

Through image analysis, the volume fractions of the hard phase and the bonding phase are respectively 85.8 percent and 14.2 percent, and the volume proportion of the hard phase 'white core-gray shell' hard phase particles is 5.7 percent; the average grain size of the sintered body was 0.56 μm. The molar contents of elements in the binding phase formed by the energy spectrum analysis are respectively Co: 30.5%, Cr: 9.3%, Ni: 33.4%, Mo: 9.4%, W: 3.6%, Ti: 13.8 percent. The mole fraction of carbide-forming elements is reduced compared to the binder phase alloy starting material composition. Therefore, TiC in the bonding phase is precipitated in situ in the sintering process, and Mo, W and Cr are diffused to the TiC precipitated in situ and original hard phase particles to form composite carbide. The mechanical property indexes of the obtained sintered body are as follows: hardness 1735HV, bending strength 1856MPa and fracture toughness K_IC10.6MPa·m^1/2。

Example 2

The ingredient combinations, compounding methods, preparation processes and sintering routes of example 1 were used. In example 2, firstly, the preparation of the binder phase mixture does not adopt a secondary addition manner of the ceramic powder, i.e., the addition manner of directly adding the ceramic powder into the binder phase wet material in the step 2 of example 1 is not adopted. But a mode of drying and sieving in an oven at 80 ℃ for standby after obtaining the bonding phase alloy mixed slurry. And then further preparing the following materials in percentage by mass: 78wt.% ceramic powder, 22wt.% reactive alloy powder mix, cermet mix; the mixing method of the mixture was the same as in example 1.

Through analysis, the shapes of the alloy mixture and the metal ceramic mixture after ball milling are not clearly distinguished. The metallographic structure of the sintered body and the scanned structure were free from formation of other phases, and were typical of the two-phase structure of cermet, and the structure was the same as that obtained in example 1. The volume fraction of the two phases and the volume proportion of the hard phase particles of the "white core-gray shell" hard phase are similar to those of the examples. The mechanical property indexes of the sintered body are as follows: hardness 1695HV, bending strength 1944MPa, fracture toughness K_IC11.1MPa·m^1/2. Compared with the embodiment 1, the adjustment of the mixing route and the drying process of the alloy mixed slurry have certain softening effect on the work hardening of the mixed material, but have no obvious influence on the mechanical property of the metal ceramic sintered body, the hardness of the sintered body is slightly reduced, and the transverse rupture strength and the fracture toughness are slightly increased.

Example 3

Changing the mixture ratio of the binding phase mixture, and preparing materials with the molar fraction of Ni: 35.0%, Co: 10.0%, Cr: 5.0%, Mo: 13.0%, W: 7.0%, Ti: 30.0 percent of mixture, and carbon powder with the mole fraction of 8.0 percent is additionally added into the mixture. The metal ceramic mixture comprises the following components in percentage by mass: 68wt.% of ceramic powder and 32wt.% of high energy storage alloy mixed powder. The mixing process and the sintering route are the same as those of the example 1, and the mixing time is prolonged to 72 hours.

After analysis, the morphology characteristics of the alloy mixture after the ball milling process are still in a flat shape, the particle size of the mixture tested by using the laser particle sizer is not changed much compared with that of the mixture in example 1, and the plastic deformation, work hardening, welding and fracture of the alloy mixture reach a balanced state after the ball milling time is 60. No new phase was found to form after phase analysis by XRD. The metallographic structure and the scanned structure of the obtained sintered body had no other phase, and were a two-phase structure typical of cermets. Through image analysis, the volume fractions of the hard phase and the bonding phase are 77.8 percent and 22.2 percent respectively; the volume proportion of hard phase particles of hard phase 'white core-gray shell' is 7.8%; average grain size of sintered bodyThe average grain size was 0.41 μm, which was finer than that in example 1, and it was found that much titanium carbide was precipitated in the binder phase. The molar contents of elements in the binding phase formed by the energy spectrum analysis are respectively Ni: 36.8%, Ti: 29.3%, Co: 18.1%, Cr: 3.5%, Mo: 7.8%, W: 4.6 percent. The mechanical property indexes of the obtained sintered body are as follows: hardness 1625HV, bending strength 2356MPa, fracture toughness K_IC12.7MPa·m^1/2。

It can be seen that although the mass fraction of hard phase carbide in the cermet mixture is reduced, TiC can be precipitated in situ and form composite carbide during sintering, and the volume fraction of hard phase in the sintered body is higher than the theoretical calculated volume fraction value of 81.8%, which proves the in-situ precipitation process of TiC during sintering again. The increase in the volume fraction of the binder phase improves the flexural strength and fracture toughness.

The above-described embodiments are merely preferred embodiments of the present invention, and should not be construed as limiting the present invention, and the scope of the present invention is defined by the claims, and equivalents including technical features described in the claims. I.e., equivalent alterations and modifications within the scope hereof, are also intended to be within the scope of the invention.