阅读说明：本技术 一种无粘结相碳化钨铝硬质合金及其制备方法 (Tungsten carbide aluminum hard alloy without binding phase and preparation method thereof ) 是由 刘建伟 马贤锋 汤华国 赵伟 于 2020-05-20 设计创作，主要内容包括：本发明提供了一种无粘结相碳化钨铝硬质合金的制备方法,包括以下步骤：A)将钨粉、铝粉和碳粉混合后进行高能球磨,得到高活性纳米级混合粉末；B)将所述高活性纳米级混合粉末冷压后进行烧结,得到无粘结相碳化钨铝硬质合金；所述烧结的压力为100～300MPa。本申请以钨粉、铝粉和碳粉为原料,通过高能球磨和活化反应烧结的方式制备了无粘结相型碳化钨铝硬质材料。(The invention provides a preparation method of a binderless tungsten carbide aluminum hard alloy, which comprises the following steps of: A) mixing tungsten powder, aluminum powder and carbon powder, and performing high-energy ball milling to obtain high-activity nanoscale mixed powder; B) sintering the high-activity nano-scale mixed powder after cold pressing to obtain tungsten carbide aluminum hard alloy without binding phase; the sintering pressure is 100-300 MPa. The preparation method takes tungsten powder, aluminum powder and carbon powder as raw materials, and prepares the binderless tungsten carbide aluminum hard material in a high-energy ball milling and activation reaction sintering mode.)

1. A preparation method of tungsten carbide aluminum hard alloy without binding phase comprises the following steps:

A) mixing tungsten powder, aluminum powder and carbon powder, and performing high-energy ball milling to obtain high-activity nanoscale mixed powder;

B) sintering the high-activity nano-scale mixed powder after cold pressing to obtain tungsten carbide aluminum hard alloy without binding phase; the sintering pressure is 100-300 MPa.

2. The preparation method of claim 1, wherein the time of the high-energy ball milling is 4-6 h, and the impact frequency is 400-1500 rpm.

3. The method according to claim 1, wherein the particle size of the highly active nano-sized mixed powder is 0 to 100nm and is not equal to 0.

4. The method according to claim 1 or 3, wherein the particle size of the highly active nanoscale mixed powder is 10 to 20 nm.

5. The preparation method according to claim 1, wherein the molar ratio of the tungsten powder to the aluminum powder to the carbon powder is (1-4): 1: (1-2).

6. The method of claim 1, wherein the high energy ball mill has a 4:1 ball to material ratio.

7. The preparation method according to claim 1, wherein the pressure of the cold pressing is 5-50 MPa.

8. The preparation method according to claim 1, wherein the sintering process is specifically as follows:

after cold pressing, the temperature is raised to the sintering temperature, and after the sintering temperature is reached, the pressure is applied and the temperature is kept.

9. The preparation method according to claim 1, wherein the sintering temperature is 1200-1500 ℃, and the heat preservation time is 2-5 min.

10. A tungsten carbide-aluminum hard alloy without binding phase is prepared from tungsten, aluminum and carbon through high-energy ball grinding, cold pressing and sintering.

Technical Field

The invention relates to the technical field of hard alloy materials, in particular to a tungsten carbide aluminum hard alloy without a bonding phase and a preparation method thereof.

Background

The tungsten aluminum carbide material is a novel hard material developed in recent years, and is a substitutional solid solution formed by partial replacement of tungsten atoms by aluminum atoms, entering tungsten carbide crystal lattices and partially replacing the lattice sites of tungsten. Compared with tungsten carbide, the material has more excellent mechanical property, and is expected to be applied to the aspects of machining tools, dies, rollers, oil well and mine drilling tools, electric contact materials and the like.

Conventional cemented carbides consist of two parts, a hard phase (tungsten carbide, titanium carbide, etc.) and a binder phase (cobalt, nickel, iron, etc.). The material is difficult to sinter without bonding metal and has lower strength and toughness, but the hardness of the material is greatly reduced along with the increase of the content of the bonding metal. How to solve the contradiction becomes a difficult problem for hard material research. Relevant research is reported at home and abroad, and the preparation of the binderless tungsten carbide aluminum sintered body has great significance to the application of tungsten carbide aluminum materials.

Tungsten is a scarce and non-renewable important strategic resource, which is expensive and has limited resources. The efficient utilization of tungsten resources has important significance for the development of related industries. The aluminum is used for partially replacing tungsten, so that the consumption of tungsten resources is saved, and the performance of the material is improved. The conventional cemented carbide is prepared by a powder metallurgy sintering method by adding a binding phase, but the general powder metallurgy method is difficult to sinter for carbide without the binding phase because the melting point is very high.

In recent years, extreme methods such as SPS and the like are reported to be adopted for preparation, the process cost is high, and the batch production is difficult. In the prior art, tungsten aluminum carbide without binder phase is prepared by high-pressure sintering, wherein a cubic press is generally adopted for high-pressure sintering, and very high pressure (up to 25GPa) is applied while ceramic powder or a green body with certain density is heated so as to realize pressure sintering of ceramic. As an extreme physical condition, high pressure can effectively change the atomic distance and atomic shell state of a substance, so that a biscuit is rapidly densified, the sintering temperature is reduced, the sintering time is reduced, the density and hardness of a sintered body are increased, and the mechanical properties and the like of the blank are improved. However, high pressure has the following problems, which restrict the development: the high-pressure equipment has obvious limitation on the shape and the size (3-4 mm) of a product block, and becomes a bottleneck problem restricting the development and the application of the technology; due to the structural problem, the vacuum degree and the temperature cannot be guaranteed; the high-pressure sintering method has low product preparation efficiency.

So far, there is no report about the method of directly preparing the binderless tungsten carbide aluminum hard alloy sintered body by using tungsten powder, aluminum powder and carbon powder as raw materials and by an activation reaction sintering method at home and abroad.

Disclosure of Invention

The invention aims to provide a preparation method of tungsten carbide aluminum hard alloy without binding phase.

In view of the above, the present application provides a method for preparing a tungsten carbide aluminum hard alloy without a binder phase, which comprises the following steps:

A) mixing tungsten powder, aluminum powder and carbon powder, and performing high-energy ball milling to obtain high-activity nanoscale mixed powder;

B) sintering the high-activity nano-scale mixed powder after cold pressing to obtain tungsten carbide aluminum hard alloy without binding phase; the sintering pressure is 100-300 MPa.

Preferably, the time of the high-energy ball milling is 4-6 h, and the impact frequency is 400-1500 r/min.

Preferably, the particle size of the high-activity nanoscale mixed powder is 0-100 nm and is not equal to 0.

Preferably, the particle size of the high-activity nanoscale mixed powder is 10-20 nm.

Preferably, the molar ratio of the tungsten powder to the aluminum powder to the carbon powder is (1-4): 1: (1-2).

Preferably, the ball-to-material ratio of the high-energy ball mill is 4: 1.

Preferably, the pressure of the cold pressing is 5-50 MPa.

Preferably, the sintering process specifically comprises:

after cold pressing, the temperature is raised to the sintering temperature, and after the sintering temperature is reached, the pressure is applied and the temperature is kept.

Preferably, the sintering temperature is 1200-1500 ℃, and the heat preservation time is 2-5 min.

The application also provides a tungsten carbide aluminum hard alloy without binding phase, which is obtained by sequentially carrying out high-energy ball milling, cold pressing and sintering on tungsten, aluminum and carbon.

The application provides a preparation method of tungsten carbide aluminum hard alloy, which comprises the steps of mixing tungsten powder, aluminum powder and carbon powder, performing high-energy ball milling to obtain high-activity nanoscale mixed powder, and performing cold pressing and sintering on the mixed powder to obtain the binderless tungsten carbide aluminum hard alloy. In the high-energy ball milling process, the invention not only realizes the uniform mixing of raw materials and the nanoscale refinement of the mixture granularity, obviously increases the powder activation energy, promotes the diffusion of solid ions, induces the chemical reaction to be carried out at a lower temperature, but also greatly improves the powder activity in the high-energy ball milling process, obtains the nanoscale pre-sintered powder with larger surface energy and distortion energy, and improves the particle distribution uniformity and the combination of the interface between tungsten and carbon, thereby realizing the improvement of the powder sintering driving force, better realizing the uniform densification sintering of the mixture in the subsequent sintering process, and preparing the binderless tungsten carbide-aluminum hard alloy without adopting high-pressure sintering. The method for preparing the tungsten carbide aluminum hard alloy without the binding phase has simple process and convenient operation, and does not need to additionally add a binding agent.

Drawings

FIG. 1 is an X-ray diffraction pattern of a cemented tungsten carbide made in example 1 of the present invention.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

In view of the problems caused by high-pressure sintering of tungsten carbide aluminum hard alloy in the prior art, research finds that tungsten powder, aluminum powder and carbon powder are utilized to prepare a binderless tungsten carbide aluminum sintered block at a lower temperature through a high-energy ball milling and activation reaction sintering mode; meanwhile, the tungsten aluminum carbide allows carbon vacancy, so the problem of carbon content in the preparation process of the non-binding phase material is solved easily. Specifically, the embodiment of the invention discloses a preparation method of a binderless tungsten carbide aluminum hard alloy, which comprises the following steps of:

A) mixing tungsten powder, aluminum powder and carbon powder, and performing high-energy ball milling to obtain high-activity nanoscale mixed powder;

B) sintering the high-activity nano-scale mixed powder after cold pressing to obtain tungsten carbide aluminum hard alloy without binding phase; the sintering pressure is 100-300 MPa.

The invention mainly utilizes high-activity nano tungsten, aluminum and carbon mixed powder to prepare the tungsten carbide aluminum hard alloy without binding phase by a low-temperature rapid reaction pressure auxiliary sintering mode. Specifically, according to the method, tungsten powder, aluminum powder and carbon powder are mixed and then subjected to high-energy ball milling, so that high-activity nanoscale mixed powder is obtained. In this process, in order to avoid the introduction of impurity elements, it is preferable to carry out under a protective gas or vacuum; the particle size of the high-activity nanoscale mixed powder is 0-100 nm, and more specifically 10-20 nm. The molar ratio of the tungsten powder to the aluminum powder to the carbon powder is (1-4): 1: (1-2). The equipment for high-energy ball milling is not particularly limited, and the equipment for high-energy ball milling which is well known to those skilled in the art can be used; in the process of the high-energy ball milling, the anti-forging agent is cancelled, and the carbon powder in the raw materials has the anti-forging function and is a reactant, so that extra impurities cannot be introduced; in the prior art, the addition of the anti-forging agent ensures that the anti-forging agent can be completely removed in the subsequent sintering process without influencing the sintering process of powder; the conventional anti-forging agent can be removed only by drying at low temperature for a long time, and carbon residue is brought in many times to influence the carbon content of powder. The high-energy ball milling time is preferably 4-6 h; the impact frequency of the high-energy ball mill is preferably 400-1500 rpm; the ball material ratio is selected to be 4: 1. the vacuum conditions are not particularly limited in the present invention, and may be those known to those skilled in the art.

According to the invention, the tungsten powder, the aluminum powder and the carbon powder are mixed and then subjected to high-energy ball milling to obtain the nano-scale mixed powder, the carbon powder has finer granularity and more uniform dispersion, and the reaction sintering can be rapidly carried out. In the process, the uniform mixing of the raw materials and the refinement of the mixed powder are realized, the diffusion of solid ions is promoted, and the low-temperature chemical reaction is induced; in the process of high-energy ball milling, the powder activity is greatly improved, the nano powder with larger surface energy and distortion energy is obtained, the particle distribution uniformity and the combination of interfaces among particles are improved, and therefore, the improvement of the powder sintering driving force is realized, and the mixture can be better subjected to uniform densification sintering in the subsequent sintering process. In order to realize the cleanness and good wettability of the interface between the tungsten, carbon and aluminum particles, no other reagent is added as a process control agent such as a forging inhibitor, and the like, and the method is realized by only controlling the ball-to-feed ratio to be 4:1, the carbon powder in the raw material can play the effect of the anti-forging agent. The obtained powder can be sintered in an in-situ interface reaction.

According to the invention, after the high-activity nano-scale mixed powder is obtained, the high-activity nano-scale mixed powder is subjected to cold pressing and then is sintered, and the binderless tungsten carbide aluminum hard alloy is obtained; in the process, the high-activity nanoscale mixed powder is preliminarily formed and then subjected to cold pressing, wherein the pressure of the cold pressing is 5-50 MPa. After cold pressing, rapidly heating to a sintering temperature, pressurizing after reaching the sintering temperature, and preserving heat; the sintering temperature is 1200-1500 ℃, and the heat preservation time is 2-5 min. The high activity of the high-activity nanoscale mixed powder enables subsequent sintering to be carried out without high pressure, and only under 100-300 MPa.

The sintering process is not particularly limited in the present invention, and may be a sintering process known to those skilled in the art. The method comprises the step of sintering the mixture in a protective gas or vacuum atmosphere to obtain the binderless tungsten carbide aluminum hard alloy. In the reaction sintering process, the invention provides a new contact surface and solid phase diffusion in the crystal grains through the random movement of reactants to realize the homogenization of the alloy, promote the combination and bonding between the particles and realize the densification and sintering of the powder. After the binderless tungsten aluminum carbide is obtained by sintering, the binderless tungsten aluminum carbide is preferably polished for convenient subsequent detection and application, and the method and the condition for polishing are not particularly limited and meet the national standard.

The invention uses tungsten powder, aluminum powder and carbon powder, uses high-energy ball milling to prepare nano-grade tungsten powder, aluminum powder and carbon powder mixed powder, and uses the concentrated heat release in the reaction process, the concentrated release of the surface energy of the high-activity nano powder and the like as the sintering driving force of tungsten aluminum carbide without binding phase; the mixed powder is ball-milled to a nano state by adopting high-energy ball milling, the powder has high activity, the sintering temperature can be greatly reduced, and the mixed powder can be rapidly sintered at a lower temperature and a lower pressure; in the sintering process, the crystal grains grow up slightly, and the mechanical property of the material is improved. Compared with the tungsten-aluminum alloy powder and carbon mixed powder, the tungsten powder, aluminum powder and carbon powder are adopted, the preparation cost is lower, and meanwhile, the mixed powder has higher activity and is more beneficial to reaction sintering.

For further understanding of the present invention, the following examples are provided to illustrate the preparation method of the binderless tungsten carbide aluminum hard alloy of the present invention, and the scope of the present invention is not limited by the following examples.

Table 1 examples raw material recipe data table