阅读说明：本技术 一种梯度硬质合金及其制备方法 (Gradient hard alloy and preparation method thereof ) 是由 邹爱忠 王水龙 王海龙 黄星 王永生 于 2020-07-11 设计创作，主要内容包括：本发明公开了一种梯度硬质合金及其制备方法,采用少量活化剂锌粉作为载体,加入到碳化钨和钴粉中,混合均匀,高温下部分进行锌熔法,在Zn粉与Co粉接触界面,Zn粉和少量Co粉形成包裹Co粉的Co-Zn液体合金,在表面张力的作用下,Co粉向内移动,从外向内逐渐增加。其工艺操作简单,容易控制,可实现工业化生产,制备的硬质合金性能好。(The invention discloses a gradient hard alloy and a preparation method thereof, wherein a small amount of activating agent zinc powder is used as a carrier and added into tungsten carbide and cobalt powder, the mixture is uniformly mixed, a part is subjected to a zinc melting method at high temperature, at a contact interface of Zn powder and Co powder, the Zn powder and a small amount of Co powder form a Co-Zn liquid alloy wrapping the Co powder, and under the action of surface tension, the Co powder moves inwards and gradually increases from outside to inside. The process is simple to operate and easy to control, industrial production can be realized, and the prepared hard alloy has good performance.)

1. The preparation method of the gradient hard alloy is characterized by comprising the following steps of:

(1) adding a small amount of zinc powder into tungsten carbide and cobalt powder to prepare a mixture with the cobalt content of 8 percent, the zinc content of more than 0 and less than 5 percent and the total carbon content of 5.3 to 5.8 percent, wet grinding and mixing, and spray drying and granulating;

(2) pre-sintering at 700-950 ℃ to ensure that Co is distributed in a gradient manner from inside to outside, and then rapidly cooling to obtain a solid phase alloy;

(3) and (3) sintering the solid phase alloy obtained in the step (2) at high temperature in vacuum, removing zinc, and cooling to obtain the gradient hard alloy.

2. The method for preparing a gradient hard alloy according to claim 1, wherein tungsten carbide with a Fisher's particle size of 1.0-4.0 μm, cobalt powder with a particle size of 1.0-3.0 μm, and zinc powder with a particle size of 1.0-5.0 μm are selected in the step (1).

3. The preparation method of the gradient hard alloy according to claim 2, wherein the alloy cylinder, the wet grinding medium and the forming agent are added into the mixed material, and the mixture is subjected to wet grinding and mixing for 6-40h under the conditions that the ball-to-material ratio is 1-5:1 and the liquid-to-material ratio is 0.2-0.4L/kg.

4. A method of making a gradient cemented carbide according to claim 3 characterised in that the particle size obtained by spray drying granulation is 60-150 μm.

5. The method for preparing the gradient hard alloy according to claim 4, wherein in the step (2), the spray particles are firstly pressed into a spherical tooth product, then the spherical tooth product is placed into a low-pressure sintering furnace for sintering, the presintering temperature is 700-.

6. The method for preparing a gradient hard alloy as claimed in claim 5, wherein the step (3) comprises vacuum sintering the cooled solid phase alloy, heating to 900-.

7. A gradient cemented carbide with a cobalt content increasing from the outside to the inside prepared by the method according to any one of claims 1-6.

Technical Field

The invention belongs to the innovation of powder metallurgy hard alloy production technology, can be industrialized and can generate considerable economic benefit.

Background

The hard alloy is a composite material prepared by using high-hardness and difficult-to-dissolve metal carbide powder as a hard phase and using metals such as CO, Ni and the like as a bonding phase through a traditional powder metallurgy method, has the characteristics of strong comprehensive performances such as wear resistance, strength, toughness and the like, and is widely applied to the fields of cutting tools, petroleum drilling, wear-resistant parts and the like. With the development of the current science and technology, the requirements of market end users on the use cost and the efficiency of hard alloy are higher and higher, the traditional hard alloy is difficult to meet the requirements of high hardness and high toughness, in the hard alloy material, the hardness and the toughness are a pair of spear shields, and the premise is to reduce the toughness while improving the hardness, so that a lot of experts have provided a gradient material for improving the hardness and the toughness, and the gradient hard alloy is mostly researched by a component gradient, namely, bonding metals Co and Ni are distributed and increased from outside to inside in the product.

At present, the preparation method of the gradient hard alloy has a plurality of patent reports, including a carburizing method, a layered compression forming method and a melt infiltration method of the university of Utah, Sweden and United states. The carburizing method mainly controls the different solubility of carbon in the alloy, so that the formed cobalt has different distribution, the process is complex and difficult to control, and industrial production is not easy to form; the layering pressing method is easy to homogenize, difficult to form gradient and easy to deform the alloy; the melt infiltration method needs to immerse the alloy into the melt at high temperature, so that the energy consumption is high, the gradient is not easy to control, and the existing preparation methods of the gradient alloy are complex in process, difficult to control and difficult to form industrial production.

The invention content is as follows:

the invention aims to provide a gradient hard alloy which is simple and feasible, is easy to control and can form industrialization and a preparation method thereof.

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

a preparation method of gradient hard alloy comprises the following steps:

(1) adding a small amount of zinc powder into tungsten carbide and cobalt powder to prepare a mixture with the cobalt content of 8 percent, the zinc content of more than 0 and less than 5 percent and the total carbon content of 5.3 to 5.8 percent, wet grinding and mixing, and spray drying and granulating;

(2) pre-burning at 700-950 ℃ to ensure that Co is distributed in a gradient manner from inside to outside, then rapidly cooling to obtain solid phase alloy, and keeping the gradient distribution state of Co;

(3) and (3) sintering the solid phase alloy obtained in the step (2) at high temperature in vacuum, removing zinc, and cooling to obtain the gradient hard alloy.

Specifically, tungsten carbide with a Fisher's particle size of 1.0-4.0 μm, cobalt powder with a particle size of 1.0-3.0 μm and zinc powder with a particle size of 1.0-5.0 μm are selected in the step (1).

Further, adding the alloy cylinder, a wet grinding medium and a forming agent into the mixture, and carrying out wet grinding and mixing for 6-40h under the conditions that the ball-to-material ratio is 1-5:1 and the liquid-to-material ratio is 0.2-0.4L/kg. Preferably, the wet grinding medium is absolute alcohol, and the forming agent is No. 56 paraffin.

Further, the particle size obtained by spray drying granulation is 60-150 μm.

Specifically, the spray particles are firstly pressed into a spherical tooth product in the step (2), then the spherical tooth product is placed into a low-pressure sintering furnace for sintering, the presintering temperature is 700-950 ℃, the pressure is 1-6MPa, the heat preservation time is 30-180min, the argon flow is 10-15L/min, the power is cut off, and the spherical tooth product is cooled to the normal temperature.

And (3) sintering the cooled solid phase alloy in vacuum, heating to 900-.

The cobalt content of the hard alloy prepared by the method is distributed in an increasing way from outside to inside.

The method adopts a small amount of activating agent zinc powder as a carrier, adds the activating agent zinc powder into tungsten carbide and cobalt powder, uniformly mixes the components, partially carries out a zinc melting method at high temperature, forms Co powder-Zn liquid alloy wrapping the Co powder at a contact interface of the Zn powder and the Co powder, and moves inwards under the action of surface tension to gradually increase from outside to inside. The activator has the function that when the sintering temperature reaches the eutectic temperature of the activator and cobalt powder, a liquid phase begins to appear, the liquid phase of the activator wets a cobalt solid phase, the liquid phase moves to the surface of cobalt particles by virtue of capillary pressure, the surface of the cobalt particles is provided with a thin layer of liquid phase, the thin layer of liquid phase is like a lubricant, the friction resistance between the cobalt powder particles and between the cobalt powder and tungsten carbide particles is rapidly reduced, due to the action of surface tension, the liquid tries to reduce the free energy of the surface of gas and liquid, the cobalt powder particles move to a tighter direction, the original uniform distribution structure is changed, cobalt shrinks towards the middle, the tungsten carbide particles are not moved, so that the cobalt distribution is gradually increased from outside to inside (in the product detection performance, the center hardness is low, the edge hardness is high, the cobalt content is increased and distributed from outside to inside), and finally the activator is removed, the invention utilizes the mechanism to, the process is simple to operate, easy to control and capable of realizing industrial production, and the prepared hard alloy has good performance.

Drawings

FIG. 1 is a spectrum of the gradient cemented carbide prepared in example 1.

Fig. 2 is an energy spectrum of the cemented carbide prepared in comparative example 1.

FIG. 3 is a spectrum of the gradient cemented carbide prepared in example 2.

Detailed Description

The invention is further illustrated by the following specific examples and figures: