阅读说明：本技术 一种高熵环相结构的Ti(C,N)基金属陶瓷及其制备方法 (Ti (C, N) -based metal ceramic with high-entropy ring-phase structure and preparation method thereof ) 是由 熊慧文 周科朝 李志友 于 2020-07-31 设计创作，主要内容包括：本发明公开了一种高熵环相结构的Ti(C,N)基金属陶瓷及其制备方法。所述Ti(C,N)基金属陶瓷的环相结构为高熵碳化物陶瓷,其成份为(Ti,M)(C,N)固溶体；其中M选自ⅣB族、ⅤB族以及ⅥB族金属元素中的三种及以上,同时(Ti,M)(C,N)固溶体中,任意两种金属元素含量摩尔比在0.8～1.2之间。所述Ti(C,N)基金属陶瓷的制备过程中以低温碳热还原法制备纳米碳化物-粘结相复合粉末,代替传统多元添加碳化物,同时通过更高的烧结温度以使得上述碳化物进行充分的溶解析出,以获得高熵碳化物环相结构。本发明所得金属陶瓷具有较常规金属陶瓷更高的硬度和抗高温氧化性能,可提高刀具的表面加工精度和使用寿命,广泛应用于轴承料、切削刀具、模具材料等领域。(The invention discloses Ti (C, N) -based metal ceramic with a high-entropy ring-phase structure and a preparation method thereof. The ring phase structure of the Ti (C, N) -based metal ceramic is high-entropy carbide ceramic, and the components of the Ti (C, N) -based metal ceramic are (Ti, M) (C, N) solid solution; wherein M is selected from three or more of IVB group, VB group and VIB group metal elements, and the molar ratio of any two metal elements in the (Ti, M) (C, N) solid solution is 0.8-1.2. In the preparation process of the Ti (C, N) -based metal ceramic, the nano carbide-binder phase composite powder is prepared by a low-temperature carbothermic method, the traditional multi-element added carbide is replaced, and the carbide is fully dissolved and precipitated through higher sintering temperature, so that a high-entropy carbide ring phase structure is obtained. The metal ceramic obtained by the invention has higher hardness and high-temperature oxidation resistance than the conventional metal ceramic, can improve the surface processing precision of the cutter and prolong the service life, and is widely applied to the fields of bearing materials, cutting cutters, die materials and the like.)

1. A Ti (C, N) -based cermet of high-entropy ring-phase structure, characterized by: the ring phase structure of the Ti (C, N) -based metal ceramic is high-entropy carbide ceramic, and the components of the Ti (C, N) -based metal ceramic are (Ti, M) (C, N) solid solution; wherein M is selected from three or more of IVB group, VB group and VIB group metal elements, and the molar ratio of any two metal elements in the (Ti, M) (C, N) solid solution is 0.8-1.2.

2. A high entropy loop phase structured Ti (C, N) -based cermet according to claim 1, characterized in that: the M is selected from at least three of W, Mo, Ta, Nb, Hf, V and Zr, and comprises W or Mo.

3. A high entropy loop phase structured Ti (C, N) -based cermet according to claim 1, characterized in that: the Ti (C, N) -based metal ceramic comprises the following raw materials in parts by mass: 30-50 parts of Ti (C, N) powder; 35-85 parts of nano carbide-binder phase composite powder and 0.5-1.5 parts of carbon powder B, wherein the nano carbide-binder phase composite powder consists of 30-65 parts of transition metal carbide and 5-20 parts of iron group metal binder phase, and a metal element M in the transition metal carbide is selected from at least three of W, Mo, Ta, Nb, Hf, V and Zr and contains W or Mo.

4. A method of preparing a Ti (C, N) -based cermet of high entropy ring phase structure according to any of claims 1-3, characterized in that: the method comprises the following steps:

step one preparation of nano carbide-binding phase composite powder

Preparing an oxide containing M and an iron group metal oxide according to a designed proportion, adding carbon powder A with a theoretical amount required by complete carbothermic reduction for primary ball milling to obtain primary ball milling powder, drying, sintering in a protective atmosphere to obtain nano carbide-binding phase composite powder,

step two, preparation of green body

Mixing Ti (C, N) powder, carbon powder B and the nano carbide-binding phase composite powder obtained in the step one according to a designed proportion, carrying out secondary ball milling to obtain secondary ball milling powder, drying and granulating the secondary ball milling powder, and carrying out compression molding to obtain a green body,

step three, sintering

And (3) performing first-stage sintering on the green body obtained in the step two in a vacuum environment, then filling mixed gas of argon and nitrogen, performing second-stage sintering under the partial pressure of nitrogen, and finally performing third-stage sintering under the atmosphere of argon.

5. A method of preparing a Ti (C, N) -based cermet of high entropy ring phase structure as claimed in claim 4, wherein: in the first step, the first ball milling is wet ball milling, the medium of the first ball milling is absolute ethyl alcohol, and the ball-to-material ratio is 10-30: 1, the ball milling time is 24-48 h.

6. A method of preparing a Ti (C, N) -based cermet of high entropy ring phase structure as claimed in claim 4, wherein: in the first step, the sintering temperature is 1200-1400 ℃, and the sintering time is 2-5 h.

7. A method of preparing a Ti (C, N) -based cermet of high entropy ring phase structure as claimed in claim 4, wherein: in the second step, the second ball milling is wet ball milling, the ball milling medium of the second ball milling is absolute ethyl alcohol, and the ball-to-material ratio is 8-15: and 1, simultaneously doping 1-2 wt% of paraffin as a forming agent in the ball milling process.

8. A method of preparing a Ti (C, N) -based cermet of high entropy ring phase structure as claimed in claim 4, wherein: in the third step, the temperature of the first-stage sintering is 1000-1200 ℃, and the time of the first-stage sintering is 3-5 hours.

9. A method of preparing a Ti (C, N) -based cermet of high entropy ring phase structure as claimed in claim 4, wherein: in the third step, the temperature of the second-stage sintering is 1300-1350 ℃, the time of the second-stage sintering is 2-5 h, and the nitrogen partial pressure is 500-1000 Pa.

In the second step, in the mixed gas, according to the volume ratio, argon: the nitrogen is 5-8: 2-5.

10. A method of preparing a Ti (C, N) -based cermet of high entropy ring phase structure as claimed in claim 4, wherein: in the third step, the temperature of the third-stage sintering is 1500-1600 ℃, the time of the third-stage sintering is 1-3 hours, and the air pressure is 1-5 MPa;

and in the third step, after the second-stage sintering heat preservation is finished, vacuumizing is firstly carried out, the temperature is raised to the third-stage sintering heat preservation temperature point in the vacuum atmosphere, and then argon is introduced.

Technical Field

The invention belongs to the technical field of ceramic material preparation, and particularly relates to a Ti (C, N) -based metal ceramic material with a high-entropy ring-phase structure and a preparation method thereof.

Background

The Ti (C, N) -based cermet is a hard composite material with Ti (C, N) as main ceramic phase and Fe-Co-Ni and other Fe-group metals as metal binding phase. In order to improve the sintering activity and the ceramic-metal interface bonding strength of Ti (C, N) -based cermet, a part (10-30) wt% of secondary carbide is often added in raw materials, wherein tungsten carbide and molybdenum carbide are taken as main materials, and a small amount (3-5) wt% of tantalum carbide or niobium carbide is added in the raw materials, so that the Ti (C, N) -based cermet has good mechanical strength and high-temperature creep resistance.

Compared with the existing harder alloys of Ti (C, N) -based metal ceramics, the strength and the thermal shock resistance are poor, but the friction coefficient is low, the red hardness and the hardness are high, so the application field of the material mainly aims at the semi-finishing or the finishing of steel materials such as stainless steel, cast iron and the like. However, the conventional Ti (C, N) -based cermet has the following problems during service: (1) the heat caused by the rapid cutting rate in the fine machining or semi-fine machining process causes the oxidation of metal and ceramic phases, and the surface machining precision is reduced; (2) the metal cutting material cut at high temperature is easy to stick to the metal ceramic, so that the surface hardness and the wear resistance of the cutter are reduced; (3) the ceramic coating on the surface of the cutter can effectively improve the problems, but the process and the cost are increased. Based on this, the hardness and high-temperature oxidation resistance of the ceramic phase are improved, and the advantages of Ti (C, N) -based cermet as a semi-finished/finished steel material can be further exerted.

The high-entropy ceramic is a multi-principal-element single-phase solid solution formed by metal cation components with the molar ratio of 5 or more. Compared with the traditional carbide, the high-entropy carbide ceramic has ultrahigh hardness, wear resistance and more excellent oxidation resistance. The high-entropy carbide is reported for the first time in 2018, and the development time of the high-entropy carbide is short, but the high-entropy carbide attracts wide attention.

Disclosure of Invention

The invention aims to provide a Ti (C, N) -based cermet with a high-red hardness, excellent wear resistance and oxidation resistance and a high-entropy ring-phase structure and a preparation method thereof, aiming at the problem that in the prior art, the hardness and the surface machining precision of the Ti (C, N) -based cermet are reduced due to the oxidation of a hardness surface layer material during high-temperature cutting.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

the invention relates to Ti (C, N) -based metal ceramic with a high-entropy ring phase structure, which is high-entropy carbide ceramic with a (Ti, M) (C, N) solid solution as a component; wherein M is selected from three or more of IVB group, VB group and VIB group metal elements, and the molar ratio of any two metal elements in the (Ti, M) (C, N) solid solution is 0.8-1.2.

In the invention, the hard phase structure of the Ti (C, N) -based cermet is a ring core structure, the ring core structure is composed of a black core phase and a ring phase wrapping the black core phase, wherein the black core phase is Ti (C, N), and the ring phase is composed of an inner ring phase and an outer ring phase which have the same components.

Preferably, M is selected from at least three of W, Mo, Ta, Nb, Hf, V and Zr, and comprises W or Mo.

In a preferred scheme, the Ti (C, N) -based cermet comprises the following raw materials in parts by mass: 30-50 parts of Ti (C, N) powder; 35-85 parts of nano carbide-binder phase composite powder and 0.5-1.5 parts of carbon powder B, wherein the nano carbide-binder phase composite powder consists of 30-65 parts of transition metal carbide and 5-20 parts of iron group metal binder phase, and a metal element M in the transition metal carbide is selected from at least three of W, Mo, Ta, Nb, Hf, V and Zr and contains W or Mo.

The invention relates to a preparation method of Ti (C, N) -based metal ceramic with a high-entropy ring-phase structure, which comprises the following steps:

step one preparation of nano carbide-binding phase composite powder

Preparing an oxide containing M and an iron group metal oxide according to a designed proportion, adding carbon powder A with a theoretical amount required by complete carbothermic reduction for primary ball milling to obtain primary ball milling powder, drying, sintering in a protective atmosphere to obtain nano carbide-binding phase composite powder,

step two, preparation of green body

Mixing Ti (C, N) powder, carbon powder B and the nano carbide-binding phase composite powder obtained in the step one according to a designed proportion, carrying out secondary ball milling to obtain secondary ball milling powder, drying and granulating the secondary ball milling powder, and carrying out compression molding to obtain a green body,

step three, sintering

And (3) performing first-stage sintering on the green body obtained in the step two in a vacuum environment, then filling mixed gas of argon and nitrogen, performing second-stage sintering under the partial pressure of nitrogen, and finally performing third-stage sintering under the atmosphere of argon.

In a preferred scheme, in the first step, the first ball milling is wet ball milling, the medium of the first ball milling is absolute ethyl alcohol, and the ball-to-material ratio is 10-30: 1, the ball milling time is 24-48 h.

In the preferred scheme, in the step one, the sintering temperature is 1200-1400 ℃, and the sintering time is 2-5 h.

In the preferred scheme, in the second step, the second ball milling is wet ball milling, the ball milling medium of the second ball milling is absolute ethyl alcohol, and the ball-to-material ratio is 8-15: and 1, simultaneously doping 1-2 wt% of paraffin as a forming agent in the ball milling process.

In the preferable scheme, in the second step, the drying mode is vacuum drying, the drying temperature is 60-80 ℃, and the drying time is 4-24 hours.

In the preferable scheme, in the third step, the temperature of the first-stage sintering is 1000-1200 ℃, and the time of the first-stage sintering is 3-5 hours.

In the preferable scheme, in the third step, the temperature of the second-stage sintering is 1300-1350 ℃, the time of the second-stage sintering is 2-5 h, and the nitrogen partial pressure is 500-1000 Pa.

Preferably, in the second step, in the mixed gas, the ratio by volume of argon: the nitrogen is 5-8: 2-5.

In the preferable scheme, in the third step, the sintering temperature of the third section is 1500-1600 ℃, the sintering time of the third section is 1-3 h, and the air pressure is 1-5 MPa.

In the preferred scheme, in the third step, after the second-stage sintering heat preservation is completed, firstly vacuumizing is performed, the temperature is raised to the third-stage sintering heat preservation temperature point in the vacuum atmosphere, and then argon is introduced, wherein the air pressure is 1-5 MPa.

It can be seen that in the present invention, the sintering procedure in the present invention is: in a vacuum environment, firstly heating to 1000-1200 ℃, carrying out solid phase sintering and heat preservation for 3-5 h, then heating to 1300-1350 ℃, simultaneously filling a mixed gas of argon and nitrogen, wherein the nitrogen partial pressure is 500-1000 Pa, the heat preservation time in the reaction stage is 2-5 h, then pumping away the mixed gas, and then carrying out subsequent vacuum sintering, wherein the vacuum degree in the vacuum environment is 5-100 Pa, when the sintering temperature is raised to the final heat preservation temperature, introducing high-purity argon, the pressure is 1-5 MPa, the sintering temperature is 1500-1600 ℃, and the heat preservation time is 1-3 h.

In the invention, in order to enable the obtained ring phase structure to be high-entropy carbide ceramic, in the sintering process, firstly, a sample needs to be subjected to solid phase stage heat preservation at the temperature of (1000-1200 ℃) in the temperature rising process for 1-3 h so as to remove residual adsorbed oxygen on the surface of nano powder; the temperature in the solid phase sintering process (1300-1350) DEG C is nitriding protective atmosphere, wherein the nitrogen partial pressure is controlled to be 500-1000 Pa, the step can reduce the formation tendency of an inner ring phase before liquid phase sintering, and the grain size at a high temperature stage is refined; and then, high-temperature sintering is carried out at 1500-1600 ℃, after the high-temperature sintering temperature is reached, low-pressure sintering is carried out in a high-purity argon atmosphere of 1-5 MPa so as to prevent the binder phase from losing too fast at high temperature, and the Ti (C, N) -based cermet provided by the invention can be obtained after cooling.

In the invention, the temperature of the third-stage sintering is higher than that of the conventional metal ceramic, so that the carbide is sufficiently dissolved and precipitated to obtain a high-entropy carbide ring phase structure.

The principle and the advantages are as follows:

the high-entropy carbide ceramic is a multi-principal-element single-phase carbide solid solution formed by a plurality of metal cation components with nearly equal molar ratios. However, even if the carbide raw material components are accurately prepared, during the formation of the ring phase structure, the solid solution components deviate from the high-entropy equilibrium state components during the dissolution and precipitation process due to inconsistent solubility of each carbide in the binder phase.

Based on the method, on one hand, the nano carbide-binding phase composite powder is prepared by a low-temperature carbothermic method, and replaces the traditional multi-element added carbide, so that the effects of high reaction activity and diffusion mass transfer rate can be obtained, and the formation of a high-entropy ring phase structure is induced.

On the other hand, in the sintering process, 0.5-1.5 wt% of free carbon (carbon component B) is added, and heat preservation is carried out for a long time (3-5 h) in the solid phase sintering stage, so that surface adsorption oxygen in the high-activity composite powder is removed, and a sintering crystal grain interface is purified; and the subsequent solid-phase reaction requires sintering in nitriding atmosphere, so that the forming trend of an inner ring phase before liquid-phase sintering is reduced, the driving force of particle growth caused by high-temperature sintering (the sintering temperature is higher than that of the traditional sintering) is relieved, and the grain size of the high-entropy ring-phase structure metal ceramic is refined.

Compared with the traditional Ti (C, N) -based cermet, the high-entropy ring-phase-structure Ti (C, N) -based cermet material provided by the invention has a high-entropy ring-phase structure, the component design of the high-entropy ring-phase Ti (C, N) -based cermet material needs to be established on a component system of the conventional cermet, and the key point is that good wettability, better mechanical property and thermodynamic stability of a ceramic phase and a metal phase are considered, the carbon thermal reduction method is utilized to prepare composite powder of nano secondary carbide and a binder phase, and the solid solution reaction of the multi-component carbide is induced by the high-temperature metal liquid phase accelerated diffusion mass transfer process. Specifically, the formation of the structure is to use secondary carbide with high reactivity and binder phase powder to replace the traditional carbide adding mode, and based on the high-temperature liquid phase sintering (1500-1600 ℃) process, promote equimolar secondary carbide and partially dissolved Ti (C, N) to carry out dissolution and precipitation reaction, and then carry out nucleation growth on the surface of the residual Ti (C, N) particles to form a high-entropy ring phase structure with a nearly equimolar ratio.

The metal ceramic prepared by the method of the invention has the following effects:

the Ti (C, N) -based metal ceramic material provided by the invention has higher hardness (HRA 92-95), good bending resistance (sigma b 1500-2400 MPa) and better air atmosphere oxidation resistance (the weight gain rate is less than 3.0 x 10 at 100h under 800℃)^-6g·mm^-2) And high temperature hardness (HRA 88-92 at 800 ℃), and when used as a cutting tool, the surface machining precision is high and the machining stability is good;

the cermet does not need a ceramic coating, the service performance and the service life of the cermet can be ensured due to excellent wear resistance and oxidation resistance, the cost is saved, and the production efficiency is improved;

the annular phase structure of the metal ceramic is more stable in thermodynamics, so that the core phase component and the interface structure of the metal ceramic are good, the grain growth rate is lower than that of a conventional product, the metal ceramic is easy to sinter at a higher temperature, and the uniform and fine tissue is kept.

In a word, the Ti (C, N) cermet material has better wear resistance, red hardness and longer service life, and the oxidation resistance and the red hardness of the cermet material are greatly improved on the basis of keeping higher toughness. Can be widely applied to the fields of bearing materials, cutting tools, die materials and the like, and has very wide market prospect.

Drawings

FIG. 1 is an SEM image of a Ti (C, N) -based cermet of a high-entropy cyclic phase structure in example 1.

FIG. 2 is an SEM image of a Ti (C, N) -based cermet of a high-entropy cyclic phase structure in example 3.

Fig. 3 is an SEM image of the conventional Ti (C, N) -based cermet in comparative example 1.

Detailed Description