A diamond composite brazing coating and a method of making the same

Abstract

This invention relates to the field of surface strengthening technology, specifically to a diamond composite brazing coating and its preparation method. The invention first mixes a brazing powder containing a first brazing filler metal powder, diamond abrasive, and flux with an organic binder to form a flexible strip-shaped brazing filler metal. Then, after a first pre-firing process, a porous, pore-fillable skeleton structure is formed. This skeleton structure is then embedded in a filler powder containing a second brazing filler metal powder and a powder binder, and ultrasonic vibration is used to fill the pores. After a second pre-firing process, it is placed on a substrate surface for induction brazing. This method can actively compensate for and repair pore defects caused by the volatilization of the organic binder before brazing, reducing pore residue in the coating after welding, improving the coating's density, surface smoothness, and abrasive bonding stability, and significantly improving the coating's surface quality.

Description

Technical Field

[0001] This invention relates to the field of surface strengthening technology, and more specifically, to a diamond composite brazing coating and its preparation method. Background Technology

[0002] Diamond, with its high hardness, excellent wear resistance, and good thermal conductivity, is often used as a wear-resistant particle on the surface of steel substrates to improve the wear resistance, cutting performance, and service life of workpieces or tools. In existing technologies, diamond is typically brazed to the steel substrate surface using brazing filler metal to form a wear-resistant coating. Some existing technologies, for ease of preparation, forming, handling, and placement, often mix brazing filler metal powder, diamond particles, and organic binders to form pre-fabricated brazing filler metal bodies in sheet, strip, or block form, which are then placed on the steel substrate surface for induction brazing. However, due to the rapid temperature rise and concentrated local temperature during induction heating, the organic binder in the pre-fabricated brazing filler metal body undergoes rapid pyrolysis and volatilization. Especially after the addition of diamond particles to the brazing filler metal, their large solid-phase distribution within the filler metal layer leads to a significant decrease in the overall fluidity of the layer, making it difficult for the gases generated by pyrolysis to escape in time. This results in large pores and voids within or on the surface of the filler metal layer. Some brazing slurries used in coating brazing processes also contain organic components, which can also cause this defect during the brazing process. The aforementioned defects are difficult to eliminate during the subsequent melting, spreading, and solidification process of brazing, resulting in uneven coating surface, increased roughness, and numerous pore defects. This also affects the coating and bonding effect of the brazing filler metal on the steel substrate and diamond particles, thereby reducing the coating's forming quality, wear resistance, and reliability.

[0003] For example, Chinese Patent CN114248209B discloses a diamond-solder composite strip and a process for preparing brazed diamond tools based thereon. While this approach is advantageous for pre-forming and ease of use, it involves pre-formed strips containing organic components directly participating in subsequent brazing. Chinese Patent CN108972387B discloses a method for preparing an induction brazed single-layer diamond grinding wheel, which involves mixing brazing filler metal and pressure-sensitive adhesive to form a brazing filler slurry, coating it onto a steel substrate, arranging diamond particles, and then completing the brazing process through induction heating. Chinese Patent CN106976023B discloses a method for induction heating high-entropy alloy brazing of a single-layer diamond grinding wheel, which involves mixing high-entropy alloy brazing filler metal, pressure-sensitive adhesive, and diamond abrasive particles, coating it onto a substrate surface, and then completing the brazing process through induction heating. All of the above methods contain organic components and diamond particles in the brazing filler layer, and during rapid heating brazing, they all suffer from uneven coating surfaces, increased roughness, and numerous porosity defects.

[0004] To address the aforementioned issues, there is an urgent need to develop a method for preparing diamond composite brazing coatings to reduce coating porosity defects, improve coating smoothness, and enhance forming quality.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The first objective of this invention is to provide a method for preparing a diamond composite brazing coating. The method involves pre-firing at low temperature to volatilize organic matter and form a pore-filling skeleton structure. Then, fine brazing filler powder is used for secondary vibration pore filling, followed by secondary low-temperature pre-firing to achieve solidification. Before induction brazing, the surface and internal pore defects of the brazing filler layer are actively compensated and repaired, thereby improving the density, smoothness and forming quality of the coating.

[0007] The second objective of this invention is to provide a diamond composite brazing coating, which is prepared by the above-described method for preparing diamond composite brazing coating.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: A method for preparing a diamond composite brazing coating includes the following steps: S1. A brazing powder containing first brazing filler powder, diamond abrasive and flux is mixed with an organic binder to obtain a mixture, and then made into a flexible strip brazing filler; S2. The strip solder is subjected to a first pre-firing to allow the organic binder to pre-evaporate, forming a porous, fillable skeleton structure, referred to as the first intermediate; S3. The first intermediate is embedded in filler powder and ultrasonically vibrated to fill the holes to obtain the second intermediate; the filler powder includes second brazing filler powder and powder binder, and the powder binder accounts for 0.5%-6% of the mass of the filler powder; S4. The second intermediate is subjected to a second pre-firing to solidify the filler powder with the pore-filling skeleton structure, thereby obtaining a third intermediate; S5. Place the third intermediate on the surface of the substrate and heat it for brazing.

[0009] Preferably, the organic binder accounts for 4%-20% of the mass of the mixture.

[0010] Preferably, the organic binder includes at least one of PVB, PVA, and PIB.

[0011] Preferably, the brazing powder accounts for 80%-96% of the mass of the mixture.

[0012] Preferably, the brazing powder comprises, by weight percentage: 60%-90% of the first brazing filler metal powder, 2%-30% of the diamond abrasive, and 2%-20% of the brazing flux.

[0013] Preferably, the first solder powder includes a first Ni-based solder, which includes at least one of BNi-2, Ni40, Ni55, and F104.

[0014] Preferably, the particle size of the first brazing filler metal powder is 30-400 mesh.

[0015] Preferably, the diamond abrasive has a particle size of 60-200 mesh.

[0016] Preferably, the flux includes at least one of FB105, FB104, and FB102.

[0017] Preferably, the temperature of the first preheating is 250-450℃, and the holding time is 5-60 minutes.

[0018] Preferably, in step S3, the ultrasonic vibration filling frequency is 20-80Hz and the vibration time is 1-10min.

[0019] Preferably, the second brazing filler powder accounts for 94%-99.5% of the mass of the filler powder.

[0020] Preferably, the second solder powder includes a second Ni-based solder, which includes at least one of BNi-2, Ni40, Ni55, and F104.

[0021] Preferably, the particle size of the second brazing filler metal powder is 500-2000 mesh.

[0022] Preferably, the powder binder comprises PVB and / or PVA.

[0023] Preferably, the particle size of the powder binder is 300-800 mesh.

[0024] Preferably, the temperature of the second preheating is 150-300℃, and the holding time is 2-40 minutes.

[0025] Preferably, in step S5, the heating method includes induction heating, first heating to 150-350℃, holding at that temperature for 20-120s, and then heating to the brazing temperature for brazing.

[0026] A diamond composite brazing coating is prepared by the diamond composite brazing coating preparation method described in any one of the foregoing embodiments.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses a first pre-firing process to pyrolyze and volatilize the organic binder in the strip-shaped solder, forming pores, voids, and loose areas on the surface and inside of the solder corresponding to the volatilization path. After the first pre-firing, the organic binder is essentially removed, and the system composed of the solder particles, diamond particles, and flux forms a continuous particle contact skeleton structure. There is mechanical interlocking and mutual friction between the particles, and slight surface diffusion connections exist between the particles at the first pre-firing temperature, thus forming a pore-filling skeleton structure with a certain strength. This structure is then embedded in filler powder and filled using ultrasonic vibration, allowing the filler powder to vibrate and fill the pores. The filler powder is fully filled into the skeleton pores; then, a second pre-firing process is used to solidify the filler powder with the pore-filling skeleton structure, so that the filler powder remains stable after filling the pores and improves the overall strength of the skeleton; then induction brazing is performed; this method can actively compensate and repair pore defects before induction brazing, reduce the residual pores in the coating after welding, improve the density, surface smoothness and abrasive bonding stability of the coating, effectively avoid the pore defects caused by the volatilization of organic binders and the obstruction of air venting and the difficulty in the flow of brazing filler metal caused by the presence of diamond during the traditional induction brazing process, and significantly improve the surface quality of the coating. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a morphology diagram of the diamond composite brazing coating obtained in Example 1 of the present invention; Figure 2 This is a morphology diagram of the diamond composite brazing coating obtained in Comparative Example 1 of the present invention; Figure 3 This is a morphology diagram of the diamond composite brazing coating obtained in Example 3 of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0031] The first aspect of the present invention provides a method for preparing a diamond composite brazing coating, comprising the following steps: S1. A brazing powder containing first brazing filler powder, diamond abrasive and flux is mixed with an organic binder to obtain a mixture, which is then made into a flexible strip brazing filler and cut into the required shape and size. S2. The cut strip of brazing filler metal is preheated to allow the organic binder to evaporate in advance, forming a porous, pore-fillable skeleton structure, referred to as the first intermediate. S3. The first intermediate is embedded in the filler powder and ultrasonically vibrated to fill the holes to obtain the second intermediate; wherein the filler powder includes a second solder powder and a powder binder, and the powder binder accounts for 0.5%-6% of the mass of the filler powder; S4. The second intermediate is pre-fired a second time to solidify the filler powder with the pore-filling skeleton structure, thus obtaining the third intermediate; S5. Place the third intermediate on the surface of the substrate and heat it for brazing.

[0032] In step S1, when preparing flexible strip solder, if the organic binder used is solid, an appropriate amount of solvent needs to be added; if the organic binder used is liquid, an appropriate amount of solvent can be selectively added or no solvent can be added as needed, as long as the solder can be prepared into a strip solder; as an example, the solvent used includes at least one of ethanol, isopropanol, and water.

[0033] This invention uniformly mixes diamond into the first brazing filler powder, which helps to achieve uniform distribution and stable embedding of diamond in the brazing filler layer. This avoids the problems of interface discontinuity and uneven abrasive distribution caused by the layered preparation system of preparing brazing filler first and then coating diamond in the traditional process. In addition, this invention adds flux to the brazing filler powder, which removes the oxide film on the surface of Ni-based brazing filler and substrate during brazing, improves interfacial activity, promotes brazing filler flow and fills pores, and improves the brazing filler spreading problem caused by the presence of diamond.

[0034] This invention mixes brazing powder and organic binder to form a flexible strip brazing filler metal that can be cut into sheets or blocks. This facilitates the preparation of prefabricated brazing filler metal bodies of different shapes and thicknesses according to the brazing requirements of the substrate, which is helpful for brazing irregular workpieces and is especially suitable for brazing scenarios with large coating thickness requirements.

[0035] Furthermore, addressing the issue of large pore defects in the coating caused by the decomposition and volatilization of organic components during rapid heating brazing in existing processes, leading to a decline in coating quality, this invention pre-heats the strip-shaped brazing filler metal before brazing. This pre-decomposes the first binder and creates pores, forming a pore-filling skeleton structure. Then, ultrasonic vibration is used to fully fill the pores of the skeleton, followed by a second pre-heating for low-temperature solidification. This actively compensates for and repairs the pore defects caused by the volatilization of the organic binder, effectively reducing pore defects in the brazed coating and improving coating quality. The specific working mechanism is as follows: During the first pre-firing process, the strip-shaped solder expands and cracks due to the pyrolysis and volatilization of the organic binder. After the organic binder has largely volatilized, pores, voids, and loose areas corresponding to the volatilization path are formed on the surface and inside of the strip-shaped solder, thus forming a pore-fillable skeleton structure (first intermediate) with pore characteristics, providing channels and space for subsequent ultrasonic vibration pore filling. After the first pre-firing, the system composed of the first solder particles, diamond particles, and flux can form a continuous particle contact skeleton structure. There is mechanical interlocking and mutual friction between the particles, and there is slight surface diffusion connection between the particles at the first pre-firing temperature. Therefore, the formed pore-fillable skeleton structure has a certain strength.

[0036] Then, the pore-fillable skeleton structure is embedded in a filler powder composed of a second brazing filler powder and a small amount of powder binder. High-frequency ultrasonic vibration is used to fill the pores, allowing the filler powder to fully fill the voids in the pore-fillable skeleton structure under vibration. The small amount of powder binder mainly serves as a temporary bond. During the second pre-firing, the powder binder softens and produces a bonding effect. After cooling, the second brazing filler powder and the pore-fillable skeleton structure are solidified together, improving the overall structural strength of the skeleton after filling and ensuring that it is not easily broken during packaging, transportation, and operation, and that the filler powder is not easily detached. This step can actively compensate for and repair the void defects caused by the volatilization of organic binder before the final induction brazing, reducing the void residue in the post-weld coating, improving the coating's density, surface smoothness, and abrasive bonding stability. It effectively avoids the void defects caused by binder volatilization and the presence of diamond leading to obstructed venting and difficulty in brazing filler material flow during traditional induction brazing, significantly improving the coating quality. Compared to the entire third intermediate, the filler powder filling the pores of the skeleton is a small amount, and the powder binder accounts for only 0.5%-6% of the filler powder content. Therefore, the binder introduced for filling the pores is trace relative to the third intermediate, far lower than the content of organic binder in step S1. During the brazing process, it has little impact on the coating quality. Before brazing, the organic binder is removed by the first pre-firing, and then the filler powder is used to fill the pores and solidification is achieved by the second pre-firing. This process can actively compensate for and repair pore defects, effectively improving the coating's forming quality, bonding strength, and wear resistance.

[0037] In some implementations, typically but not limitingly, for example, the mass percentage of the powder binder in the filler powder in step S3 can be any one of 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, or a range of any two of these values; preferably 1%-4%.

[0038] In some specific embodiments of the present invention, the mass percentage of the organic binder in the mixture in step S1 is 4%-20%, for example, it can be any one value or a range of any two values ​​from 4%, 6%, 8%, 10%, 12%, 15%, 18%, 20%; preferably 8%-15%.

[0039] In some specific embodiments of the present invention, the organic binder used in step S1 includes at least one of PVB (polyvinyl butyral), PVA (polyvinyl alcohol), and PIB (polyisobutylene).

[0040] In some specific embodiments of the present invention, the mass percentage of brazing powder in the mixture in step S1 is 80%-96%, for example, any one value or any two values ​​from 80%, 85%, 90%, 92%, 96%; preferably 85%-92%.

[0041] In some specific embodiments of the present invention, the brazing powder, by mass percentage, comprises: 60%-90% first brazing filler metal powder, 2%-30% diamond abrasive, and 2%-20% flux. Typically, but not limitingly, for example, the mass percentage of the first brazing filler metal powder in the brazing powder can be any one value or a range of any two values ​​from 60%, 70%, 80%, and 90%; the mass percentage of the diamond abrasive can be any one value or a range of any two values ​​from 2%, 5%, 10%, 15%, 20%, 25%, and 30%, preferably 5%-25%; and the mass percentage of the flux can be any one value or a range of any two values ​​from 2%, 5%, 10%, 15%, and 20%, preferably 5%-15%.

[0042] In some specific embodiments of the present invention, the first solder powder includes a first Ni-based solder, which includes at least one of BNi-2, Ni40, Ni55, and F104.

[0043] In some specific embodiments of the present invention, the particle size of the first brazing filler metal powder is 30-400 mesh, for example, it can be any one value or a range of any two values ​​among 30 mesh, 60 mesh, 100 mesh, 200 mesh, 300 mesh, and 400 mesh; preferably 60-300 mesh.

[0044] In some specific embodiments of the present invention, the particle size of the diamond abrasive is 60-200 mesh. For example, it can be any one value or a range of any two values ​​among 60 mesh, 80 mesh, 100 mesh, 120 mesh, 150 mesh, and 200 mesh.

[0045] In some specific embodiments of the present invention, the flux used includes at least one of FB105, FB104, and FB102.

[0046] In some specific embodiments of the present invention, the temperature of the first pre-firing is 250-450°C, for example, it can be any one value or a range of any two values ​​among 250°C, 300°C, 350°C, 400°C, and 450°C, preferably 300-400°C; the holding time is 5-60 min, for example, it can be any one value or a range of any two values ​​among 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min, preferably 20-40 min. As an example, the first pre-firing is carried out in a vacuum furnace or a vacuum drying oven. The purpose of the first pre-firing is to decompose and volatilize the organic binder, forming a porous, fillable skeleton structure with a certain strength, providing open channels for the subsequent filling of filler powder.

[0047] In some specific embodiments of the present invention, in step S3, the vibration frequency of the ultrasonic vibration filling is 20-80Hz, for example, it can be any one value or a range of any two values ​​among 20Hz, 40Hz, 60Hz, and 80Hz; the vibration time is 1-10min, for example, it can be any one value or a range of any two values ​​among 1min, 3min, 5min, 8min, and 10min; ultrasonic vibration can disperse and fill the filling powder, promote the filling powder to enter the open pores, and improve the efficiency of the filling powder filling the fillable pore skeleton.

[0048] In some specific embodiments of the present invention, the mass percentage of the second brazing filler powder in step S3 is 94%-99.5%, for example, it can be any one value or a range of any two values ​​from 94%, 96%, 98%, 99%, 99.5%; preferably 96%-99%; the main component of the filler powder is the second brazing filler powder, and by filling the surface and internal pores of the fillable hole skeleton with brazing filler powder, the hole defects can be actively compensated and repaired.

[0049] In some specific embodiments of the present invention, the second solder powder includes a second Ni-based solder, which includes at least one of BNi-2, Ni40, Ni55, and F104.

[0050] In some specific embodiments of the present invention, the particle size of the second brazing filler powder is smaller than that of the first brazing filler powder. Using coarse powder to create holes first and then using fine powder to fill them results in better performance and can improve the overall density and uniformity of the pre-made brazing filler body.

[0051] In some specific embodiments of the present invention, the particle size of the second brazing filler metal powder is 500-2000 mesh. For example, it can be any one value or a range of any two values ​​among 500 mesh, 600 mesh, 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh; preferably, it is 600-1500 mesh.

[0052] In some specific embodiments of the present invention, the powder binder includes PVB and / or PVA.

[0053] In some specific embodiments of the present invention, the particle size of the powder binder is 300-800 mesh, for example, it can be any one value or a range of any two values ​​among 300 mesh, 400 mesh, 500 mesh, 600 mesh, 700 mesh and 800 mesh.

[0054] In some specific embodiments of the present invention, the second pre-firing temperature is 150-300℃, for example, it can be any one value or a range of any two values ​​among 150℃, 200℃, 250℃, and 300℃, preferably 200-250℃; the holding time is 2-40 min, for example, it can be any one value or a range of any two values ​​among 2 min, 10 min, 20 min, 30 min, and 40 min, preferably 10-20 min. The purpose of the second pre-firing is to soften the powder binder and generate a bonding effect, so that the second solder powder and the through-hole skeleton structure can be solidified at low temperature, locking in the filler powder, improving the overall structural strength, and facilitating transportation and storage.

[0055] In some specific embodiments of the present invention, the heating method in step S5 includes induction heating, first heating to 150-350°C, for example, any one value or a range of any two values ​​among 150°C, 200°C, 250°C, 300°C, and 350°C; holding at this temperature for 20-120 seconds, for example, any one value or a range of any two values ​​among 20 seconds, 40 seconds, 60 seconds, 80 seconds, 100 seconds, and 120 seconds; and then first evaporating at a low temperature. The remaining small amount of organic matter is removed, and then the mixture is heated to the brazing temperature for brazing. For example, both the first and second brazing filler powders are nickel-based filler metals, and the brazing temperature is 800-1100℃, for example, any value from 800℃, 900℃, 1000℃, and 1100℃, or a range of any two values. The holding time is 10-90s, for example, any value from 10s, 30s, 60s, and 90s, or a range of any two values. This invention removes the organic binder beforehand and fills the resulting voids with brazing filler metal. Then, it heats in stages, first using low-temperature volatilization to evaporate a small amount of residual organic matter, preventing rapid volatilization or the formation of carbon slag inside due to insufficient volatilization, while also promoting overall temperature uniformity. Subsequently, it is heated to the brazing temperature, where the flux promotes the flow and spread of the brazing filler metal, filling any small voids that may result from the volatilization of residual organic matter later. This multi-process synergy significantly reduces voids in the coating and improves the surface quality of the coating.

[0056] A second aspect of the present invention provides a diamond composite brazing coating, which is prepared by the diamond composite brazing coating preparation method described in any one of the foregoing embodiments.

[0057] The following detailed description of some embodiments of the present invention is provided in conjunction with specific application examples. Unless otherwise specified, all raw materials used in the embodiments can be obtained commercially available.

[0058] Example 1 S1. A brazing coating powder is obtained by mixing nickel-based brazing filler powder (BNi-2, 150 mesh), diamond abrasive (80-100 mesh), and flux (FB105), wherein the mass fraction of BNi-2 is 75%, the mass fraction of diamond abrasive is 15%, and the mass fraction of FB105 is 10%. The brazing powder and PVA are mixed in a ratio of 90% and 10% by mass, respectively, to obtain a mixture. An appropriate amount of water is added and kneaded into a bonding brazing filler metal, which is then made into sheets as needed. S2. Place the sheet-like adhesive brazing filler metal into a vacuum furnace and preheat it at 350°C for 30 minutes. Remove it to obtain the first intermediate. S3. Mix 98wt% of BNi-2 brazing filler powder (1000 mesh) and 2wt% of PVB powder (500 mesh) evenly to obtain filler powder. Embed the first intermediate into a vibrating groove containing filler powder and perform ultrasonic vibration to fill the hole at a vibration frequency of 60Hz for 5 minutes to obtain the second intermediate. S4. The second intermediate is placed in a muffle furnace for a second pre-calcination, and held at 200°C for 15 minutes to obtain the third intermediate; S5: Place the third intermediate on the substrate to be brazed and heat it by induction heating. First, heat it to 250-300℃ and hold it for 40 seconds to volatilize a small amount of residual organic matter; then heat it to 1000-1100℃ and hold it for 30 seconds, and then cool it to obtain a diamond composite brazing coating with good surface quality.

[0059] Example 2 S1. A brazing powder is prepared by mixing nickel-based brazing filler powder (BNi-2, 150 mesh), diamond abrasive (80-100 mesh), and flux (FB105), wherein the mass fraction of BNi-2 is 65%, the mass fraction of diamond abrasive is 20%, and the mass fraction of FB105 is 15%. The brazing powder and PVB are mixed in a ratio of 88% and 12% by mass, respectively, to obtain a mixture. An appropriate amount of ethanol is added and kneaded into a bonding brazing alloy, which is then formed into sheets as needed. S2. Place the sheet-like adhesive brazing filler metal into a vacuum furnace and preheat it at 400°C for 40 minutes. Then remove it to obtain the first intermediate. S3. Mix 97wt% BNi-2 (1000 mesh) and 3wt% PVB powder (500 mesh) evenly to obtain filler powder. Embed the first intermediate into a vibrating trough containing the filler powder and perform ultrasonic vibration to fill the pores at a vibration frequency of 40Hz for 5 minutes to obtain the second intermediate. S4. The second intermediate is placed in a muffle furnace for a second pre-calcination, and held at 250°C for 10 minutes to obtain the third intermediate; S5: Place the third intermediate on the substrate to be brazed and heat it by induction heating. First, heat it to 300-350℃ and hold it for 40 seconds to volatilize a small amount of residual organic matter; then heat it to 950-1050℃ and hold it for 60 seconds, and then cool it to obtain a diamond composite brazing coating with good surface quality.

[0060] Example 3 Example 3 is similar to Example 1, except that in step S5, the brazing is performed by directly heating to the brazing temperature using induction heating, and all other conditions are the same as in Example 1.

[0061] Due to the rapid or insufficient evaporation of the remaining small amount of binder, a small amount of carbon slag is formed inside, resulting in a generally poor surface quality of the diamond composite brazing coating.

[0062] Comparative Example 1 Comparative Example 1 is similar to Example 1, except that steps S2, S3 and S4 are not performed, and the sheet-like brazing filler metal obtained in step S1 is directly placed on the substrate in step S5 for brazing; all other conditions are the same as in Example 1.

[0063] The organic binder expands during heating and evaporates in the form of smoke. After the organic binder has evaporated, there are obvious pores left by evaporation on the surface and inside of the brazing filler layer. During brazing, because the pores caused by the evaporation of the binder are not compensated in advance, and the solid phase diamond causes poor flow and spreading of the brazing filler, the brazing filler is difficult to fill the large number of pore defects caused by the evaporation of the organic binder through the flow and spreading under the action of the flux alone. As a result, the surface quality of the diamond composite brazing coating is poor.

[0064] Comparative Example 2 Comparative Example 2 is similar to Example 1, except that steps S3 and S4 are not performed. Instead, the first intermediate obtained in step S2 is directly placed on the substrate in step S5 for brazing. All other conditions are the same as in Example 1.

[0065] Because the existing voids and defects are not compensated and the solid diamond causes poor flow and spreading of the brazing filler metal, the brazing filler metal is unable to fill the large number of voids and defects caused by the volatilization of the organic binder through flow and spreading under the action of flux alone, resulting in poor surface quality of the diamond composite brazing coating.

[0066] Comparative Example 3 Comparative Example 3 is similar to Example 1, except that in step S3, ultrasonic vibration was not used to fill the holes, but only manual shaking was used; all other conditions are the same as in Example 1.

[0067] Due to insufficient filling of the pores, voids and defects still exist. Furthermore, the solid diamond leads to poor flow and spreading of the brazing filler metal. Under the action of flux alone, the brazing filler metal is unable to fill the remaining numerous pores and defects through flow and spreading, resulting in a generally poor surface quality of the diamond composite coating.

[0068] Test case The forming quality of the diamond composite brazing coating in each embodiment and comparative example was observed, and its wear resistance was tested. The test standard was JB / T7705-1995—dry sand / rubber wheel method. The test results are shown in Table 1.

[0069] Table 1

[0070] Depend on Figure 1 , Figure 2 , Figure 3 As shown in Table 1, the diamond composite brazing coatings in Examples 1 and 2 exhibited good forming quality and excellent wear resistance. In Example 3, the forming quality and wear resistance decreased compared to the examples because the residual organic matter was not volatilized at low temperature before the heating brazing process. Comparative Example 1, which did not remove the organic binder beforehand and fill the resulting voids, showed significantly poorer coating forming quality and a marked decrease in wear resistance. Comparative Example 2, although the organic binder was removed beforehand, did not fill the resulting voids, resulting in a significant decrease in coating forming quality and wear resistance. Comparative Example 3, which used manual shaking to insufficiently fill voids, also showed a noticeable decrease in coating forming quality and wear resistance compared to the examples.

[0071] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a diamond composite brazing coating, characterized in that, Includes the following steps: S1. A brazing powder containing first brazing filler powder, diamond abrasive and flux is mixed with an organic binder to obtain a mixture, and then made into a flexible strip brazing filler; S2. The strip solder is subjected to a first pre-firing to allow the organic binder to pre-evaporate, forming a porous, fillable skeleton structure, referred to as the first intermediate; S3. The first intermediate is embedded in filler powder and ultrasonically vibrated to fill the holes to obtain the second intermediate; the filler powder includes second brazing filler powder and powder binder, and the powder binder accounts for 0.5%-6% of the mass of the filler powder; S4. The second intermediate is subjected to a second pre-firing to solidify the filler powder with the pore-filling skeleton structure, thereby obtaining a third intermediate; S5. Place the third intermediate on the surface of the substrate and heat it for brazing.

2. The method for preparing the diamond composite brazing coating according to claim 1, characterized in that, It meets at least one of the following characteristics: (1) The organic binder accounts for 4%-20% of the mass of the mixture; (2) The organic binder includes at least one of PVB, PVA and PIB.

3. The method for preparing the diamond composite brazing coating according to claim 1, characterized in that, It meets at least one of the following characteristics: (1) The brazing powder accounts for 80%-96% of the mass of the mixture; (2) By mass percentage, the brazing powder comprises: 60%-90% of the first brazing filler powder, 2%-30% of the diamond abrasive, and 2%-20% of the brazing flux; (3) The first solder powder includes a first Ni-based solder, which includes at least one of BNi-2, Ni40, Ni55, and F104; (4) The particle size of the first brazing filler metal powder is 30-400 mesh; (5) The particle size of the diamond abrasive is 60-200 mesh; (6) The flux includes at least one of FB105, FB104, and FB102.

4. The method for preparing the diamond composite brazing coating according to claim 1, characterized in that, The temperature of the first preheating is 250-450℃, and the holding time is 5-60 minutes.

5. The method for preparing the diamond composite brazing coating according to claim 1, characterized in that, In step S3, the ultrasonic vibration filling frequency is 20-80Hz and the vibration time is 1-10min.

6. The method for preparing the diamond composite brazing coating according to claim 1, characterized in that, It meets at least one of the following characteristics: (1) The second brazing filler powder accounts for 94%-99.5% of the total mass of the filler powder; (2) The second solder powder includes a second Ni-based solder, which includes at least one of BNi-2, Ni40, Ni55, and F104; (3) The particle size of the second brazing filler metal powder is 500-2000 mesh.

7. The method for preparing the diamond composite brazing coating according to claim 1, characterized in that, It meets at least one of the following characteristics: (1) The powder binder includes PVB and / or PVA; (2) The particle size of the powder binder is 300-800 mesh.

8. The method for preparing the diamond composite brazing coating according to claim 1, characterized in that, The second preheating temperature is 150-300℃, and the holding time is 2-40 minutes.

9. The method for preparing the diamond composite brazing coating according to claim 1, characterized in that, In step S5, the heating method includes induction heating, first heating to 150-350℃, holding at that temperature for 20-120s, and then heating to the brazing temperature for brazing.

10. A diamond composite brazing coating, characterized in that, The diamond composite brazing coating was prepared using the method described in any one of claims 1-9.

Images