CN115142040B - Diamond film with high welding strength and preparation method and application thereof - Google Patents

Abstract

The invention discloses a diamond film with high welding strength and its preparation method and application. The diamond film includes metal carbide particles, a diamond layer and diamond grains, wherein protruding metal carbide particles are arranged on the lower surface of the diamond layer, and the metal carbide particles are partially embedded in the diamond layer; Protruding diamond grains are arranged on the upper surface of the diamond layer, and the diamond grains grow integrally with the diamond layer. The present invention adopts the hot wire chemical vapor deposition method, which can simply embed carbide into the lower surface of the diamond layer. At the same time, by changing the applied bias voltage in the later stage of deposition, the structure of the diamond growth surface can be reasonably controlled to obtain a convex surface that grows integrally with the diamond layer. diamond grains. When the diamond film is used for brazing, it can form effective bonding, significantly improve the welding strength during brazing, and the preparation method is simple, which is conducive to industrial application.

Description

A diamond film with high welding strength and its preparation method and application

Technical field

The invention belongs to the field of surface processing film material preparation, and specifically relates to a diamond film with high welding strength and its preparation method and application.

Background technique

Diamond is a special type of elemental carbon whose crystal structure belongs to the equiaxed face-centered cubic system. The connecting bonds between carbon atoms in diamond are hybrid covalent bonds with high binding force, stability and directionality. The unique crystal structure gives diamond the highest hardness among natural substances (Mohs hardness is 10), the highest elastic modulus, the lowest compression coefficient, and excellent wear resistance, corrosion resistance and chemical stability. The fracture stress of diamond is as high as 40*10 ³ MPa, and plastic flow does not occur before fracture. Diamond with excellent physical and mechanical properties is an ideal material for making hard and brittle material processing tools. It is widely used in drill bits, sawing tools, abrasive tools, etc. for processing hard and brittle materials such as cemented carbide, engineering ceramics, optical glass, semiconductor materials, and granite. A wide range of grinding tools and other important super-hard wear-resistant surfaces. Diamond film materials play an important role in this field.

In order to facilitate the use of diamond film materials, it is usually necessary to use brazing technology to weld the diamond film to the surface of the substrate. However, diamond brazing has the following significant problems: First, for thick diamond films, in order to ensure the strength of diamond, the grown diamond must be highly dense, so the brazing material cannot penetrate into the diamond structure, making it difficult to achieve diamond brazing. The second is that the solder has poor wettability to diamond and it is difficult to form chemical bonds, resulting in a significant lack of diamond welding strength and the diamond film is easily peeled off from the substrate. Therefore, how to improve the welding strength between the diamond film and the substrate is an urgent problem to be solved.

Contents of the invention

Aiming at the existing problem of low welding strength between diamond and matrix, the present invention provides a diamond film with high welding strength and its preparation method and application. There are metal tungsten carbide protrusions and diamond protrusions on the two surfaces of the diamond film respectively, which can form an effective bond when brazing with the metal substrate, significantly improving the welding strength during brazing, and the preparation method is simple, which is conducive to industrialization application.

In order to solve the above technical problems, the present invention adopts the following technical solutions:

A diamond film with high welding strength is provided, including metal carbide particles, a diamond layer and diamond grains, wherein protruding metal carbide particles are arranged on the lower surface of the diamond layer, and the metal carbide particles are partially embedded in the diamond film. In the diamond layer, protruding diamond grains are arranged on the upper surface of the diamond layer, and the diamond grains and the diamond layer are grown integrally.

According to the above solution, the particle size of the metal carbide particles is micron level.

According to the above solution, the carbide is at least one of silicon carbide, tungsten carbide, titanium carbide or tantalum carbide. The difference in carbide type makes no difference in diamond growth and final brazing and subsequent use performance.

According to the above solution, the convex diamond grains are isolated from each other, and the exposed crystal plane is (100).

According to the above solution, the surface of the convex diamond grains is also covered with a layer of silicon carbide or titanium carbide.

A method for preparing the above-mentioned diamond film with high welding strength is provided, which specifically includes the following steps:

1) Spread the carbide particles evenly on the surface of the refractory metal plate, and then use the hot wire chemical vapor deposition method to grow a diamond film on the surface;

2) In the later stage of diamond film growth, the structure of the diamond film is changed by changing the bias voltage. Before changing the bias voltage, make sure that a positive bias voltage relative to the hot wire is applied to the metal plate for more than 4 hours to allow the diamond film to grow. The exposed crystal faces on the surface are mainly (111); then a negative bias voltage is applied relative to the hot wire, and the negative bias voltage is maintained for 2-5 hours to form isolated diamond convex crystals with exposed crystal faces (100). particles; that is, a diamond film with high welding strength is obtained.

The present invention rationally controls the structure of the diamond growth surface by changing the applied bias voltage in the later stage of deposition: when the exposed diamond surface is (100), isolated convex grains are easily formed in the early stage, but when the growth time is long, the distance between the grains They will be connected together and the degree of convexity will be reduced; when the exposed surface is (111), the grains will be closely connected to each other due to the formation of twins. Apply a positive bias voltage so that the exposed crystal face on the diamond film growth surface is dominated by (111); then apply a negative bias voltage, which is conducive to the rapid growth of the (111) face. The results obtained under positive bias conditions in the previous stage A large number of exposed (111) crystal faces will rapidly grow to form a large number of isolated diamond convex grains with exposed crystal faces (100).

According to the above solution, in step 1), the refractory metal plate is a molybdenum plate or a tungsten plate, and the material has no effect on the growth of diamond.

According to the above scheme, in step 1), the carbide particles are evenly spread on the surface of the refractory metal plate. The specific steps are:

Pure carbide particles are ultrasonically dispersed in an organic solvent, and evenly spread on the refractory metal plate by spin coating, and the organic solvent is evaporated.

According to the above scheme, in step 1), the process parameters of the hot wire chemical vapor deposition method are: the proportion of hydrocarbons is 1-5%, the proportion of argon and hydrogen is 0-20%; the pressure in the cavity is 1-8kPa; the hot wire power is adjusted , keep the temperature of the refractory metal plate between 700-1150°C, and the deposition time depends on the thickness of the diamond film.

According to the above solution, in step 2), the positive bias voltage is 30-250V; the negative bias voltage is 30-200V.

According to the above solution, step 2) also includes, after obtaining the diamond convex crystal grains, introducing silicon source gas or titanium source gas to form silicon carbide or titanium carbide that is closely combined with the diamond on the diamond surface.

Preferably, the silicon source gas is SiH ₄ or SiCl ₄ and the titanium source gas is TiCl ₄ .

Preferably, the amount of silicon source gas or titanium source gas introduced is 1-10% of the amount of carbon source introduced.

Preferably, after the silicon source gas or titanium source gas is introduced, deposition is continued for 0.5-1 hour.

An application of the diamond film with high welding strength in brazing is provided.

The beneficial effects of the present invention are as follows:

1. The present invention provides a diamond film with high welding strength. The carbide particles on the lower surface are embedded in the diamond film and closely connected with the diamond. When brazing, the carbide and solder have good wettability and can Form an effective connection; at the same time, there are gaps between the diamond protruding grains on the diamond growth surface. During brazing, the solder can enter the gap and effectively wrap the diamond protruding grains to form a tight connection; therefore, the two surfaces of the obtained diamond film are The metal matrix can form an effective bond during brazing, thereby improving the welding strength during brazing.

2. The present invention adopts the hot wire chemical vapor deposition method, which can simply embed carbide into the lower surface of the diamond layer. At the same time, by applying a positive bias voltage in the later stage of deposition, the exposed crystal plane on the growth surface of the diamond film is (111). Mainly, a negative bias voltage is then applied to accelerate the growth rate of the (111) face of the diamond film, thereby forming diamond protruding grains that are isolated from each other and have an exposed crystal face of (100); this method is achieved by simply changing the hot wire chemical vapor deposition According to the process conditions of the method, the metal carbide particles on the lower surface of the diamond layer and the diamond grains on the upper surface can be convex, which significantly enhances the bonding strength between diamond and welding matrix.

3. In order to further enhance the interaction between the diamond growth surface and the solder, a small amount of titanium and silicon-containing substances can be introduced into the reaction gas at the end of the diamond growth to form carbides on the diamond surface, and the solder can enhance the carbides. The combination of wettability and tight wrapping of the diamond protrusions further increases weld strength.

Description of the drawings

Figure 1 is a schematic structural diagram of a diamond film obtained in an embodiment of the present invention.

Figure 2 is a cross-sectional photograph of the diamond film obtained in the embodiment of the present invention, in which there are gaps between the diamond protrusions, and the exposed surfaces of the protrusions are (100) crystal planes.

Detailed ways

The technical solution of the present invention will be further explained below through specific examples.

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Add titanium carbide powder to absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate. Spin-coat the titanium carbide dispersion evenly on the refractory metal plate. After drying, put it into the hot wire chemical in vapor deposition equipment.

2) Turn on the hot wire chemical vapor deposition device to prepare the diamond film. The carbon sources used to prepare diamond are gases such as methane and ethane or liquids such as acetone, methanol, ethanol, etc., and the carrier gas is hydrogen to speed up the deposition rate of the diamond film. , to improve the quality of the diamond film, a certain amount of argon gas can also be introduced at the same time. The conditions for diamond deposition are: the proportion of carbon and hydrogen is 1-5%, and the proportion of argon and hydrogen is 0-20%; the pressure in the cavity during diamond deposition is 1-8kPa; the temperature of the refractory metal plate is maintained at 700-1150 by adjusting the power of the hot wire. ℃, the deposition time depends on the thickness of the diamond film;

3) In the later stage of diamond film growth, the structure of the diamond film is changed by changing the bias voltage. Before changing the bias voltage, make sure that a positive bias voltage relative to the hot wire is applied to the metal plate for more than 4 hours. The bias voltage is 30-250V; then apply a negative bias voltage relative to the hot wire, maintain the negative bias voltage for 2-5 hours, and the negative bias voltage is 30-200V.

When it is necessary to further enhance the welding strength by forming carbides on the diamond growth surface, SiH ₄ , TiCl ₄ , SiCl ₄ , etc. can be introduced during the last 0.5-1 hour of diamond film growth to grow silicon carbide that is closely combined with diamond on the diamond surface. Or titanium carbide, the amount of titanium or silicon introduced is about 1-10% of the amount of carbon introduced, and the deposition process conditions remain unchanged.

Example 1:

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Spin-coat titanium carbide evenly on the refractory metal plate, dry it and place it in a hot wire chemical vapor deposition device. The specific method of spin coating is: add 1g of titanium carbide powder to 100ml of absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate, and complete spin coating at a rotation speed of 500 rpm;

2) Turn on the hot wire chemical vapor deposition device, evacuate to 8kPa, and then introduce 100 sccm of hydrogen, 3 sccm of methane, and 10 sccm of argon;

3) Adjust the power to 8kW, keep the temperature stable at around 700°C, and continue growing for 150 hours;

4) Apply a positive bias voltage of 30V to the refractory metal plate for 8 hours;

5) Then change the bias voltage to a negative bias voltage of 30V to grow diamond protruding grains, continue for 2 hours, close the device, and obtain a diamond film with high welding strength.

When Ag-Cu-Ti solder is used to weld the lower surface of the diamond film to cemented carbide, the average shear strength of the joint is 47MPa; when Ag-Cu-Ti solder is used to weld the growth surface of the diamond film to cemented carbide, The average shear strength of the joints is 51MPa respectively; when the growth surface is a non-grown diamond protrusion, when the diamond film growth surface is welded to the cemented carbide using Ag-Cu-Ti solder, the average shear strength of the joints is 33MPa. .

Example 2:

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Spin-coat titanium carbide evenly on the refractory metal plate, dry it and place it in a hot wire chemical vapor deposition device. The specific method of spin coating is: add 1g of titanium carbide powder to 100ml of absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate, and complete spin coating at a rotation speed of 500 rpm;

2) Turn on the hot wire chemical vapor deposition device, evacuate to 5kPa, use hydrogen as the carrier gas to blow acetone into the cavity, the inflow volume of acetone is 5 sccm, the hydrogen flow rate is 100 sccm, and then 20 sccm argon gas is introduced;

3) Adjust the power to keep the temperature stable at around 1150°C and continue growing for 100 hours;

4) Apply a positive bias voltage of 30V to the refractory metal plate for 4 hours;

5) Then change the bias voltage to a negative bias voltage of 30V, continue for 3 hours, turn off the hot wire device, and obtain a diamond film with high welding strength.

When Ag-Cu-Ti solder is used to weld the lower surface of the diamond film to cemented carbide, the average shear strength of the joint is 45MPa; when Ag-Cu-Ti solder is used to weld the growth surface of the diamond film to cemented carbide, The average shear strength of the joints is 55MPa respectively; when the growth surface is made of diamond convex grains that have not grown, and Ag-Cu-Ti solder is used to weld the diamond film growth surface to cemented carbide, the average shear strength of the joints are respectively is 32MPa.

Example 3:

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Spin-coat titanium carbide evenly on the refractory metal plate, dry it and place it in a hot wire chemical vapor deposition device. The specific method of spin coating is: add 1g of titanium carbide powder to 100ml of absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate, and complete spin coating at a rotation speed of 500 rpm;

2) Turn on the hot wire chemical vapor deposition device, evacuate to 1kPa, and then introduce 100sccm of hydrogen, 1sccm of ethane, and 20sccm of argon;

3) Adjust the power to keep the temperature stable at around 900°C, apply a positive bias voltage of 50V, and continue growing for 100 hours;

4) Then change the bias voltage to a negative bias voltage of 60V for 2 hours;

5) While maintaining the same process, pass in 10 sccm of silane gas for 1 hour, close the device, and obtain a diamond film with high welding strength.

When Ag-Cu-Ti solder is used to weld the lower surface of the diamond film to cemented carbide, the average shear strength of the joint is 49MPa; when Ag-Cu-Ti solder is used to weld the growth surface of the diamond film to cemented carbide, The average shear strength of the joints is 58MPa respectively; when the growth surface is a non-grown diamond protrusion, when the diamond film growth surface is welded to the cemented carbide using Ag-Cu-Ti solder, the average shear strength of the joints is 31MPa. .

Example 4:

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Spin-coat titanium carbide evenly on the refractory metal plate, dry it and place it in a hot wire chemical vapor deposition device. The specific method of spin coating is: add 1g of titanium carbide powder to 100ml of absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate, and complete spin coating at a rotation speed of 500 rpm;

2) Turn on the hot wire chemical vapor deposition device, evacuate to 7kPa, and then introduce 200 sccm of hydrogen and 5 sccm of methane;

3) Adjust the power to keep the temperature stable at around 700°C and continue growing for 200 hours;

4) Apply a positive bias voltage of 50V to the refractory metal plate for 10 hours;

5) Then change the bias voltage to a negative bias voltage of 50V, continue for 2 hours, close the device, and obtain a diamond film with high welding strength.

When Ag-Cu-Ti solder is used to weld the lower surface of the diamond film to cemented carbide, the average shear strength of the joint is 46MPa; when Ag-Cu-Ti solder is used to weld the growth surface of the diamond film to cemented carbide, The average shear strength of the joints is 53MPa respectively; when the growth surface is a non-grown diamond protrusion, when the diamond film growth surface is welded to the cemented carbide using Ag-Cu-Ti solder, the average shear strength of the joints is 32MPa. .

Example 5:

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Spin-coat titanium carbide evenly on the refractory metal plate, dry it and place it in a hot wire chemical vapor deposition device. The specific method of spin coating is: add 1g of titanium carbide powder to 100ml of absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate, and complete spin coating at a rotation speed of 500 rpm;

2) Turn on the hot wire chemical vapor deposition device, evacuate to 4kPa, use hydrogen as the carrier gas to blow the methanol in the ice bath into the cavity, the input volume of methanol is 4ml/min, the total flow rate of hydrogen is 200sccm, and then pass in 18sccm of argon;

3) Adjust the power to keep the temperature stable at around 1000°C and continue growing for 300 hours;

4) Apply a positive bias voltage of 80V to the refractory metal plate for 4 hours;

5) Then change the bias voltage to a negative bias voltage of 80V, continue for 4 hours, turn off the hot wire device, and obtain a diamond film with high welding strength.

When Ag-Cu-Ti solder is used to weld the lower surface of the diamond film to cemented carbide, the average shear strength of the joint is 49MPa; when Ag-Cu-Ti solder is used to weld the growth surface of the diamond film to cemented carbide, The average shear strength of the joints is 58MPa respectively; when the growth surface is a non-grown diamond protrusion, when the diamond film growth surface is welded to the cemented carbide using Ag-Cu-Ti solder, the average shear strength of the joints is 34MPa. .

Example 6:

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Spin-coat titanium carbide evenly on the refractory metal plate, dry it and place it in a hot wire chemical vapor deposition device. The specific method of spin coating is: add 1g of titanium carbide powder to 100ml of absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate, and complete spin coating at a rotation speed of 500 rpm;

2) Turn on the hot wire chemical vapor deposition device, evacuate to 3kPa, and then introduce 300 sccm of hydrogen, 15 sccm of methane, and 30 sccm of argon;

3) Adjust the power to 1.2KW, keep the temperature stable at around 1100°C, and continue growing for 8 hours;

4) Apply a positive bias voltage of 100V to the refractory metal plate for 8 hours;

5) Then change the bias voltage to a negative bias voltage of 200V for 4 hours;

6) Pour in 30 sccm TiCl ₄ gas for 0.5 hours, close the device, and obtain a diamond film with high welding strength.

Example 7:

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Spin-coat titanium carbide evenly on the refractory metal plate, dry it and place it in a hot wire chemical vapor deposition device. The specific method of spin coating is: add 1g of titanium carbide powder to 100ml of absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate, and complete spin coating at a rotation speed of 500 rpm;

2) Turn on the hot wire chemical vapor deposition device, evacuate to 6kPa, and then introduce 300 sccm of hydrogen, 10 sccm of methane, and 10 sccm of argon;

3) Adjust the power to 10kW, keep the temperature stable at around 800°C, and continue growing for 5 hours;

4) Apply a positive bias voltage of 120V to the refractory metal plate for 3 hours;

5) Then change the bias voltage to a negative bias voltage of 120V, continue for 3 hours, close the device, and obtain a diamond film with high welding strength.

When Ag-Cu-Ti solder is used to weld the lower surface of the diamond film to cemented carbide, the average shear strength of the joint is 43MPa; when Ag-Cu-Ti solder is used to weld the growth surface of the diamond film to cemented carbide, The average shear strength of the joints is 64MPa respectively; when the growth surface is a non-grown diamond protrusion, when the diamond film growth surface is welded to the cemented carbide using Ag-Cu-Ti solder, the average shear strength of the joints is 31MPa. .

Example 8:

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Spin-coat titanium carbide evenly on the refractory metal plate, dry it and put it into a hot wire chemical vapor deposition device. The specific method of spin coating is: add 1g of titanium carbide powder to 100ml of absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate, and complete spin coating at a rotation speed of 500 rpm;

2) Turn on the hot wire chemical vapor deposition device, evacuate to 7kPa, use hydrogen as the carrier gas to blow the ethanol in the ice bath into the cavity, the inflow volume of ethanol is 4sccm, the hydrogen flow rate is 150sccm, and then 15sccm of argon gas is introduced ;

3) Adjust the power to 1.1KW, keep the temperature stable at around 1100°C, and continue growing for 6 hours;

4) Apply a positive bias voltage of 50V to the refractory metal plate for 4 hours;

5) Then change the bias voltage to a negative bias voltage of 200V, continue for 4 hours, turn off the hot wire device, and obtain a diamond film with high welding strength.

When Ag-Cu-Ti solder is used to weld the lower surface of the diamond film to cemented carbide, the average shear strength of the joint is 46MPa; when Ag-Cu-Ti solder is used to weld the growth surface of the diamond film to cemented carbide, The average shear strength of the joints is 52MPa respectively; when the growth surface is a non-grown diamond protrusion, when the diamond film growth surface is welded to the cemented carbide using Ag-Cu-Ti solder, the average shear strength of the joints is 32MPa. .

Example 9:

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Spin-coat titanium carbide evenly on the refractory metal plate, dry it and place it in a hot wire chemical vapor deposition device. The specific method of spin coating is: add 1g of titanium carbide powder to 100ml of absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate, and complete spin coating at a rotation speed of 500 rpm;

2) Turn on the hot wire chemical vapor deposition device, evacuate to 4kPa, and then introduce 250 sccm of hydrogen, 10 sccm of methane, and 20 sccm of argon;

3) Adjust the power to keep the temperature stable at around 1000°C and continue growing for 100 hours;

4) Apply a positive bias voltage of 150V to the refractory metal plate for 6 hours;

5) Then change the bias voltage to a negative bias voltage of 150V for 5 hours;

6) Pour in 15 sccm SiCl ₄ gas for 0.8 hours, close the device, and obtain a diamond film with high welding strength.

When Ag-Cu-Ti solder is used to weld the lower surface of the diamond film to cemented carbide, the average shear strength of the joint is 45MPa; when Ag-Cu-Ti solder is used to weld the growth surface of the diamond film to cemented carbide, The average shear strength of the joints is 56MPa respectively; when the growth surface is a non-grown diamond protrusion, when the diamond film growth surface is welded to the cemented carbide using Ag-Cu-Ti solder, the average shear strength of the joints is 32MPa. .

Example 10:

A method for preparing a diamond film with high welding strength is provided, including the following steps:

1) Spin-coat titanium carbide evenly on the refractory metal plate, dry it and place it in a hot wire chemical vapor deposition device. The specific method of spin coating is: add 1g of titanium carbide powder to 100ml of absolute ethanol, and after ultrasonic dispersion, drop it on the refractory metal plate, and complete spin coating at a rotation speed of 500 rpm;

2) Turn on the hot wire chemical vapor deposition device, evacuate to 5kPa, and then introduce 300 sccm of hydrogen, 15 sccm of methane, and 15 sccm of argon;

3) Adjust the power to keep the temperature stable at around 750°C and continue growing for 100 hours;

4) Apply a positive bias voltage of 200V to the refractory metal plate for 5 hours;

5) Then change the bias voltage to a negative bias voltage of 200V, continue for 2 hours, close the device, and obtain a diamond film with high welding strength.

When Ag-Cu-Ti solder is used to weld the lower surface of the diamond film to cemented carbide, the average shear strength of the joint is 49MPa; when Ag-Cu-Ti solder is used to weld the growth surface of the diamond film to cemented carbide, The average shear strength of the joints is 54MPa respectively; when the growth surface is a non-grown diamond protrusion, when the diamond film growth surface is welded to the cemented carbide using Ag-Cu-Ti solder, the average shear strength of the joints is 31MPa. .

Claims (9)

1. A diamond film with high welding strength, characterized in that it includes metal carbide particles, a diamond layer and diamond grains, wherein the lower surface of the diamond layer is provided with protruding metal carbide particles, and the metal carbide The particles are partially embedded in the diamond layer; protruding diamond grains are arranged on the upper surface of the diamond layer, and the diamond grains and the diamond layer are grown integrally. 2. The diamond film according to claim 1, characterized in that the particle size of the metal carbide is micron level; the carbide is at least one of silicon carbide, tungsten carbide, titanium carbide or tantalum carbide. 3. The diamond film according to claim 1, characterized in that the protruding diamond grains are isolated from each other, and the exposed crystal face is (100). 4. The diamond film according to claim 1, characterized in that the surface of the convex diamond grains is also covered with a layer of silicon carbide or titanium carbide. 5. A method for preparing a diamond film with high welding strength according to any one of claims 1 to 4, characterized in that it specifically includes the following steps: 1) Spread the carbide particles evenly on the surface of the refractory metal plate, and then use the hot wire chemical vapor deposition method to grow a diamond film on the surface; 2) In the later stage of diamond film growth, the structure of the diamond film is changed by changing the bias voltage. First, ensure that a positive bias voltage relative to the hot wire is applied to the metal plate for more than 4 hours, so that the exposed crystal plane on the diamond film growth surface Mainly (111); then apply a negative bias relative to the hot wire, maintain the negative bias for 2-5 hours, and form isolated diamond convex grains with an exposed crystal face of (100), which is the welding strength High diamond film. 6. The preparation method according to claim 5, characterized in that in step 1), the carbide particles are evenly spread on the surface of the refractory metal plate, and the specific steps are: Pure carbide particles are ultrasonically dispersed in an organic solvent, and evenly spread on the refractory metal plate by spin coating, and the organic solvent is evaporated. 7. The preparation method according to claim 5, characterized in that in step 2), the positive bias voltage is 30-250V; the negative bias voltage is 30-200V. 8. The preparation method according to claim 5, characterized in that step 2) further includes, after obtaining the diamond convex grains, introducing silicon source gas or titanium source gas to form and Diamond-tightly bonded silicon carbide or titanium carbide. 9. Application of the diamond film with high welding strength according to any one of claims 1 to 4 in brazing.