WO2015096684A1

WO2015096684A1 - Method for microwave cladding of cuw alloy on cu substrate surface

Info

Publication number: WO2015096684A1
Application number: PCT/CN2014/094576
Authority: WO
Inventors: 江开勇; 张际亮; 王霏; 王小伟
Original assignee: 华侨大学
Priority date: 2013-12-25
Filing date: 2014-12-23
Publication date: 2015-07-02
Also published as: CN103882423B; CN103882423A

Abstract

Provided is a method for microwave cladding of a CuW alloy on a Cu substrate surface. A method combining powder metallurgy and microwave heating technology is used to achieve good welding of a CuW alloy coating layer and a Cu substrate. The Cu substrate and the CuW alloy coating layer are fused to one another, and a good bonding effect is achieved. The time required for microwave welding is short, and the obtained CuW alloy coating layer has high hardness and good wear resistance.

Description

Method for microwave cladding CuW alloy on surface of Cu substrate

Technical field

The invention relates to the field of microwave welding, in particular to a microwave welding machine for metal materials.

Background technique

Cu has been widely used in industrial production because of its good electrical conductivity (second only to Ag), but Cu has poor ductility, low hardness, and poor surface wear resistance, which has limitations in some applications. In the traditional industry, Cu is mixed with other metals to prepare alloys to improve the hardness and surface wear resistance of Cu. However, the cost of preparing the alloy is high, and a large amount of other metals mixed with Cu will lower the physical properties of Cu itself.

The coating technology is applied to the surface of the Cu substrate, so that the surface of the Cu substrate is provided with an alloy coating, which not only increases the hardness and wear resistance of the surface of the Cu substrate, but also does not destroy the physical properties of the Cu matrix itself. However, the traditional coating technology requires long welding time, the joint strength between the alloy coating and the substrate is not strong, the alloy coating density is not high, the alloy coating is not uniform, and the coating technology is restricted in Cu. Application on the substrate.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method for microwave cladding CuW alloy on the surface of a Cu substrate, shortening the sintering time, increasing the density of the alloy coating layer and the uniformity of the alloy coating layer, and improving the wear resistance of the coating layer. .

In order to solve the above technical problems, the present invention provides a micro surface on a Cu substrate. The method of wave cladding CuW alloy adopts a combination of powder metallurgy and microwave heating technology, and the main steps are as follows:

a. Cu powder with particle size ≤25μm, W powder with particle size ≤2μm are mixed according to the ratio of Cu85--95, W15--5 and added with anhydrous alcohol to stir evenly;

b. Put the Cu and W powder into the ball mill tank, vacuum the ball mill tank, and then fill the protective gas, then ball mill according to the ball milling speed 300r/min--400r/min and the ball milling time 6h-10h to obtain the CuW alloy powder. ;

c. Surface cleaning of the surface of the Cu substrate, mainly including degreasing, pickling, and drying;

d. The CuW alloy powder is pressed together with the Cu matrix, and the pressure is set to 20 MPa by cold pressing, and the pressure is maintained for 2 minutes;

e. setting the reference temperature of the microwave welding to the melting temperature of the low melting matrix material Cu;

f. When performing the microwave welding, the Cu substrate is placed in a heat preservation bucket and a preheating material is added for mixing heating, and the heating rate is controlled;

g. After the microwave heating is finished, the Cu substrate is insulated, and the holding time is set to 5 min - 15 min.

h. The sintering environment in the microwave welding process is a protective atmosphere sintering environment.

Preferably, the microwave frequency is 2.45 GHz.

Preferably, the shielding gas is argon.

Preferably, the protective atmosphere sintering environment is a high purity argon sintering environment.

Preferably, the degreasing process is specifically: charging the Cu substrate into a container containing acetone and then washing in an ultrasonic cleaner for 20 minutes.

Preferably, the pickling process is specifically: placing the degreased Cu matrix into a container Concentrated hydrochloric acid was added at a concentration of 15% at the same time, and after eroding for 2 minutes, it was rinsed with a large amount of water. The Cu substrate was blown dry and then washed in absolute ethanol for 10 minutes to ensure that the Cu substrate was sufficiently clean and dehydrated.

Preferably, the drying process is specifically: placing the degreased and pickled Cu substrate in a vacuum drying oven, adding silica gel as a desiccant, drying at 100 ° C for 60 minutes, and then placing the vacuum. Store at room temperature.

Preferably, the preheating material is SiC.

Preferably, the heat preservation barrel is an alumina fiber heat preservation barrel.

Preferably, when Cu, W powder of 85% Cu and 15% W mixed arrangement is used, the optimal microwave welding parameters of the Cu, W powder and Cu matrix are: welding temperature 880 ° C, heating rate 15 ° C / min, Holding time 15min.

A Cu-clad CuW alloy coated Cu substrate obtained by the method of microwave cladding CuW alloy on the surface of a Cu substrate, wherein the CuW alloy coating has a bonding strength with the Cu matrix of 50.85 MPa, the CuW alloy The surface hardness of the coating is up to 257 HV.

In summary, the method for microwave cladding CuW alloy on the surface of Cu substrate successfully achieves good welding of CuW alloy coating and Cu matrix, and Cu matrix and CuW alloy coating are fused together, and have good bonding effect. The time required for microwave welding is short, and the obtained CuW alloy coating has high hardness and good wear resistance.

DRAWINGS

Figure 1 is a schematic view of a microwave heating apparatus used in the experiment of the present invention.

2 is a diagram showing the energy spectrum analysis of a sample microwave welding section in an embodiment of the present invention.

3 is a photograph of a pore of a microwave welded sample in an embodiment of the present invention, wherein:

(a) is the interior of the CuW alloy coating (b) is the surface of the CuW alloy coating

4 is a schematic view showing a measurement point of a sample section and a microhardness distribution diagram according to an embodiment of the present invention, wherein:

(a) is a schematic diagram of the measurement point (b) is a microhardness distribution map

FIG. 5 is a schematic diagram of a sample loading model and a loading test according to an embodiment of the present invention.

FIG. 6 is a schematic view showing the three-dimensional surface morphology of a CuW alloy coating and a Cu matrix fracture according to an embodiment of the present invention.

FIG. 7 is a schematic view showing the relationship between the wear rate of the CuW alloy coating and the time according to the embodiment of the present invention.

Figure 8 is a graph showing the effect of surface hardness on wear of a CuW alloy coating in an embodiment of the present invention.

detailed description

The invention is further illustrated by the following figures and examples.

The electrolytic copper powder with particle size ≤25μm is sieved by the test sieve, and the tungsten powder prepared by the hydrogen reduction method is prepared, and the component powder is arranged according to the mass fraction of 85% Cu and 15% W (wherein the particle size of Cu powder is ≤25 μm, the particle size of W powder is ≤2 μm) . In order to make the powder evenly mixed, a certain amount of anhydrous alcohol was added and stirred uniformly, followed by wet grinding in a variable frequency planetary ball mill. The invention adopts a speed-adjustable planetary ball mill, and uses a quenched steel ball as a ball grinding medium, wherein the small ball is 50×φ5, the large ball is 10×φ18, and the ball mass ratio is 17:1. In the ball milling, the ball mill can be vacuumed first, and then argon gas is used as a shielding gas to avoid oxidation of Cu and W powder during ball milling. The ball milling speed was 400 r/min and the ball milling time was 10 h. After the ball milling was completed, the CuW alloy powder was placed in a vacuum drying oven and dried at a temperature of 80 ° C and a drying time of 4 h.

The quality of the surface pretreatment of Cu matrix will directly affect the adsorption force of CuW alloy coating and Cu substrate surface, which plays an important role in the successful implementation of subsequent microwave welding and welding quality. Therefore, it is necessary to clean the surface of the Cu substrate before pressing the CuW alloy powder, including steps such as degreasing, pickling, and drying. The Cu substrate test piece was first placed in a container containing acetone and then placed in an ultrasonic cleaner for 20 minutes. The cleaned Cu substrate was placed in a container while adding concentrated hydrochloric acid at a concentration of 15%, and after eroding for 2 minutes, it was rinsed with a large amount of water. The Cu substrate was blown dry and then washed in absolute ethanol for 10 minutes to ensure that the sample was sufficiently clean and dehydrated. After pickling, a large amount of micropores are generated on the surface of the Cu matrix, which increases the surface area of the Cu matrix to a certain extent, and contributes to the mechanical locking ability, thereby promoting the bonding of the CuW alloy coating to the Cu matrix. Finally, the treated Cu substrate was placed in a vacuum drying oven, and silica gel was added as a desiccant, and dried at 100 ° C for 60 minutes, and then stored in a vacuum at room temperature.

The CuW alloy powder and the Cu matrix were pressed together by cold pressing method. The Cu substrate was placed in the center of the mold by a 769YP-24B powder tableting machine, and a small amount of CuW powder was placed on the Cu substrate to make the pressure reach 20 MPa, and the pressure was maintained. 2 minutes. The CuW alloy coating layer has a thickness of about 200-500 μm. For the welding of dissimilar metals, a large pressure can reduce or prevent the pores, and promote the micro-plastic deformation of the welding surface to achieve the purpose of tight joints, and promote the activation of the welding interface atoms and increase the atomic diffusion speed. However, when the pressure is too large, it may cause deformation of the welded Cu matrix.

Microwave welding uses high-vacuum microwave high-temperature experimental furnace, microwave frequency 2.45GHz, most The large output power is 3KW, and the temperature range of the infrared thermometer is 450°C-2250°C. The system can control the heating rate according to the set temperature profile. The cold pressed Cu substrate is placed in a crucible, and the crucible is placed in a structure of a wrapped alumina fiber thermal insulation barrel, and a small piece of SiC is added for mixing heating. It is kept at a high temperature for a certain period of time to facilitate atomic migration and improve interface bonding strength.

Welding temperature is the most important method parameter for microwave welding. In a certain temperature range, the higher the temperature, the better the plasticity of the CuW alloy powder, the faster the diffusion process, and the higher the welding strength obtained. Therefore, a higher welding temperature should be used as much as possible, but too high a temperature causes problems such as grain coarsening, composition change or even melting of the Cu matrix. Therefore, the melting temperature of the low melting base material Cu is selected as the microwave welding reference temperature.

Rapid heating is one of the important features that distinguishes microwave heating technology from traditional heating technology. At the same time, the thermodynamic and kinetic characteristics of the sintered body are accompanied by changes in the rate of temperature increase. Therefore, it is necessary to select a suitable heating rate. When the heating rate is too high, the Cu matrix exhibits thermal instability such as cracking and bulging.

The longer the holding time, the more sufficient the material to diffuse, which is beneficial to increase the bonding strength. However, for the pressed Cu matrix, the soldering temperature is generally higher than the recrystallization temperature. When the holding time is too long, the crystal grains in the soldering surface region are excessively grown, resulting in a decrease in mechanical properties. In the actual welding process, the holding time can be changed within a larger range of experience, and then gradually optimized.

In this embodiment, the orthogonal welding scheme is used to determine the preferred welding method parameters: the Cu matrix is sintered in a protective atmosphere of high purity argon gas, wherein the welding temperature is selected from 850 ° C, 880 ° C and 920 ° C; the heating rate is 15 ° C / min, respectively. 20 ° C / min and 25 ° C / min; The interval is 5 min, 10 min and 15 min. The experimental results show that the preferred combination of welding parameters is welding temperature 880 ° C, heating rate 15 ° C / min, holding time 15 min.

The data analysis of the CuW alloy coating prepared above is carried out below:

(1) Microstructure of CuW alloy coating

Through energy spectrum analysis of the test piece, it was found that after microwave sintering, the sample produced only single-phase copper, single-phase tungsten, and no oxide was produced. It is indicated that the microwave sintering method of the present invention can achieve oxidation-free soldering, as shown in FIG.

Microwave heating material is a kind of body heating method, that is, the material is heated by the internal self, and the heat is transferred from the inside to the outside. During the heating and heating process, the temperature inside the material is always higher than the surface of the material. Figure 3 shows the metallographic micrograph of the surface of the CuW alloy coating and the interior of the CuW alloy coating after microwave welding. It can be seen from the figure that there are holes in the CuW alloy coating, and the internal pores of the CuW alloy coating are fine and uniform. The surface of the CuW alloy coating has more micropores and is relatively disorderly distributed. This indicates that microwave welding can achieve homogenization of the central structure of the CuW alloy coating.

(2) Surface hardness of CuW alloy coating

90% Cu, 10% W and 95Cu, 5% W were placed into two CuW alloy powders according to the ball milling speed of 300r/min, 350r/min, ball milling time of 6h, 8h, and CuW alloy coating was prepared according to the above steps. A comparison of the aforementioned 85% Cu, 15% W CuW alloy powder.

The surface of three microwave-welded CuW alloy coatings was measured by Vickers hardness method (HV1.96). Five points were uniformly taken near each sampling point on the surface of the CuW alloy coating layer, and the average value was obtained. The hardness value of this point. The measurement results are shown in Fig. 4. From the Cu matrix to the CuW alloy coating, the microhardness is remarkably improved. Which is located at the joint The two points B and C have the highest hardness. In addition, the hardness of the CuW alloy coating increases as the W content increases, and the maximum value is 257 HV.

(3) CuW alloy coating bond strength.

The invention adopts the improved press-in method to evaluate the bonding strength between the CuW alloy coating and the Cu matrix, that is, the wedge-shaped loading method, as shown in FIG. The wedge loading method refers to placing a wedge-shaped indenter on the wedge-shaped slit of the sample (the position of the wedge-shaped slit is generally set at the junction of the coating and the substrate) while keeping the center line of the wedge-shaped indenter coincident with the interface of the coating substrate, and then A static load is applied to the indenter to cause the sample to crack along the interface of the coating and the substrate. According to the boundary conditions of the force of the sample during the loading process, the bond strength formula of the interface between the coating and the substrate can be obtained.

A set of five CuW alloy coatings obtained according to the parameters of the above-mentioned optimal welding method were taken for shear strength test, and the average value of the five test results was about 40 MPa. It can be seen from Fig. 6 that while the CuW alloy coating is sheared off, the Cu matrix surface layer is also sheared off with the CuW alloy coating, and the Cu matrix has pits. The measured maximum pit depth can reach 135.3μm, which is about 1/3 of the thickness of the coating. The maximum pit area can reach 20mm ² , which is about 1/5 of the total area of the solder coating. From this, it can be determined that the CuW alloy coating and the Cu matrix have achieved metallurgical bonding.

(4) Abrasion resistance

In this embodiment, the wear amount of the CuW alloy coating in the unit wear time is measured by the weight loss method, and the mass change of the Cu matrix is measured, thereby obtaining the wear amount and the wear rate of the CuW alloy coating. The wear rate is calculated as follows:

Where m' - wear rate;

m ₁ - the mass of the Cu matrix before one test;

m ₂ - Cu matrix mass after one test.

Referring to Fig. 7, it can be concluded from the figure that in the running-in phase, due to the large roughness of the friction surface, the actual contact surface in the friction process appears as partial contact point contact, and the adhesion caused by friction is serious, so the wear rate of the CuW alloy coating is higher. Big. As the running-in progresses, some of the contact points gradually flatten, the friction surface roughness value gradually decreases, the contact area increases, and the wear rate gradually decreases, creating conditions for the stable wear phase. When entering the stable wear settlement, the wear rate tends to be stable, and the wear amount per unit time tends to be stable.

Referring to Fig. 8, by measuring the wear amount of the CuW alloy coating per unit time on the surface of the CuW alloy coating, it can be seen that the surface hardness of the CuW alloy coating is higher during the running-in phase, and the wear amount per unit time. The less the wear resistance, the better. At the same time, the wear resistance of each position is far greater than the wear resistance of Cu.

In summary, the present invention uses a combination of powder metallurgy and microwave heating technology to achieve microwave welding of a CuW alloy coating on a Cu substrate. Through the metallographic microstructure analysis of the sample, the hardness of the CuW alloy coating, the bonding strength of the CuW alloy coating and the Cu matrix, and the wear resistance of the CuW alloy coating were evaluated, and the following main conclusions were obtained:

(1) Successfully achieve good welding of CuW alloy coating and Cu matrix, Cu matrix and CuW alloy coating are fused together and have good bonding effect; welding period is 40min, which is only 10% of conventional copper-based material diffusion welding; CuW The hardness of the alloy coating is 2.5 times the hardness of the Cu matrix. The welding rule of Cu-15%W alloy coating and Cu matrix was tested by orthogonal test, and the optimal welding method parameters were obtained, namely, welding temperature was 880 °C, heating rate was 15 °C/min, and holding time was 15 min. The hardness of the welded sample is the largest, the hardness at the interface of the CuW alloy coating and the Cu matrix is 258 HV, and the surface hardness of the CuW alloy coating is 240 HV.

(2) The maximum bond strength of the CuW alloy coating to the Cu matrix was 50.89 MPa by testing the shear strength of the samples prepared under different welding conditions. While the CuW alloy coating was cut off, the Cu matrix surface was also sheared off with the CuW alloy coating, and the Cu matrix was pitted. The measured maximum pit depth can reach 135.3μm, which is about 1/3 of the thickness of the coating. The maximum pit area can reach 20mm ² , which is about 1/5 of the total area of the solder coating. The well-welded CuW alloy coating combines well with the Cu matrix.

(3) The wear resistance of the welded CuW coating was evaluated. The friction factor decreased with the increase of the rotational speed. At the initial stage of wear, the wear rate of the CuW alloy coating was larger. When entering the stable wear stage, the wear rate tends to Stable; the higher the surface hardness of the CuW alloy coating, the better the wear resistance; since the CuW alloy coating is prepared by powder metallurgy, the CuW alloy coating has a certain porosity and can be applied to the work with self-lubricating friction requirements. condition.

The above embodiments are merely illustrative of the principles of the invention and are not the only embodiments of the invention. The above embodiments are not to be considered as limiting the scope of the invention. Modifications and variations are possible by those skilled in the art in the <RTIgt; The specific scope of protection shall be subject to the claims.

Industrial applicability

The invention adopts a combination of powder metallurgy and microwave heating technology to achieve good welding of the CuW alloy coating and the Cu matrix, and the Cu matrix and the CuW alloy coating are fused together.

Claims

A method for microwave cladding CuW alloy on the surface of a Cu substrate, the main steps of which are:

a. Cu powder with particle size ≤25μm, W powder with particle size ≤2μm are mixed according to Cu85%--99%, W15%--1%, and added with anhydrous alcohol to stir evenly;

b. Put the Cu and W powder into the ball mill tank, vacuum the ball mill tank, and then fill the protective gas, then ball mill according to the ball milling speed 300r/min--400r/min and the ball milling time 6h-10h to obtain the CuW alloy powder. ;

c. Surface cleaning of the surface of the Cu substrate, mainly including degreasing, pickling, and drying;

d. The CuW alloy powder is pressed together with the Cu matrix, and the pressure is set to 20 MPa by cold pressing, and the pressure is maintained for 2 minutes;

e. setting the reference temperature of the microwave welding to the melting temperature of the low melting matrix material Cu;

f. When performing the microwave welding, the Cu substrate is placed in a heat preservation bucket and a preheating material is added for mixing heating, and the heating rate is controlled;

g. After the microwave heating is finished, the Cu substrate is insulated, and the holding time is set to 5 min - 15 min;

h. The sintering environment in the microwave welding process is a protective atmosphere sintering environment.
A method of microwave cladding a CuW alloy on a surface of a Cu substrate according to claim 1, wherein said microwave frequency is 2.45 GHz.
A method of microwave cladding a CuW alloy on a surface of a Cu substrate according to claim 1, wherein the shielding gas is argon.
A method of microwave cladding a CuW alloy on a Cu substrate surface according to claim 1, wherein the protective atmosphere sintering environment is a high purity argon sintering environment.
The method for microwave cladding a CuW alloy on a Cu substrate surface according to claim 1, wherein the degreasing process is specifically: loading the Cu substrate into a container containing acetone, and then placing the ultrasonic cleaner Wash in 20 minutes.
The method for microwave cladding a CuW alloy on a surface of a Cu substrate according to claim 1, wherein the pickling process is specifically: placing the degreased Cu matrix into a container while adding a concentration of 15% The concentrated hydrochloric acid was etched for 2 minutes and then rinsed with a large amount of water; the Cu substrate was blown dry and then washed in absolute ethanol for 10 minutes to ensure that the Cu substrate was sufficiently clean and dehydrated.
The method for microwave cladding CuW alloy on the surface of a Cu substrate according to claim 1, wherein the drying process is specifically: placing the degreased and pickled Cu substrate in a vacuum drying oven. At the same time, silica gel was added as a desiccant, and dried at 100 ° C for 60 minutes, and then stored in a vacuum chamber at room temperature.
A method of microwave cladding a CuW alloy on a Cu substrate surface according to claim 1, wherein the preheating material is SiC.
A method of microwave cladding CuW alloy on a Cu substrate surface according to claim 1, wherein the heat preservation barrel is an alumina fiber heat preservation barrel.
A method of microwave cladding CuW alloy on a surface of a Cu substrate according to claim 1, wherein when Cu, W powder is mixed with 85% Cu and 15% W, the Cu, W powder and Cu are used. The microwave welding parameters of the substrate are: welding temperature 880 ° C, heating rate 15 ° C / min, holding time 15 min.
A Cu-clad CuW alloy-coated Cu substrate obtained by the method of claim 1, wherein the CuW alloy coating layer has a thickness of 200 to 500 μm.