In-situ braze coating method of diamond metal composite coating and composite coating

Abstract

The invention relates to the technical field of material surface modification, in particular to an in-situ braze coating method of a diamond metal composite coating and the composite coating. The braze coating method comprises the following steps: S1, preparing a flux-cored wire by taking diamond particles as a flux core component; s2, hollow tungsten electrode electric arc welding is adopted for braze coating, a flux-cored wire is fed through a wire feeding cavity in the center of a hollow tungsten electrode, a Cr welding wire and a Ni welding wire are fed from the two sides of the hollow tungsten electrode in the braze coating direction, the end of the Cr welding wire and the end of the Ni welding wire are located in an electric arc between the annular end face of the electron emission end of the hollow tungsten electrode and the workpiece base body, and the workpiece base body is formed; and inert gas is introduced in the braze coating process to protect the braze coating part. According to the method, the hollow tungsten electrode arc welding is adopted, and the braze coating is carried out through cooperation of coaxial diamond conveying and a double-side wire feeding process, so that the temperature distribution of a molten pool can be optimized, coating metal can be molten, the coating quality is guaranteed, the problem of diamond ablation can be avoided, and the wear resistance of the coating can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of material surface modification, in particular to an in-situ brazing coating method of a diamond metal composite coating and a composite coating. Background Art

[0002] Brazing coating technology is a material surface modification technology that forms a composite coating with high-melting-point hard particles and low-melting-point brazing filler metal by heating. It has the advantages of high metallurgical bonding strength, a wide range of coating thickness, and high coating surface precision. It is widely used in aerospace, agricultural machinery, oil drilling, mining and other fields. Diamond brazing coating technology combines the advantages of traditional brazing coating technology, and uses diamond particles with extremely high hardness, good wear resistance and chemical stability as a reinforcing phase, which greatly improves the wear resistance of the brazing coating. However, traditional brazing coating technology requires the coating to be pre-placed on the surface of the workpiece and then heated for preparation. There are problems such as difficulty in pre-positioning the coating on the surface of complex workpieces and long coating pre-positioning cycles. The improvement in brazing coating efficiency is limited, and it is difficult to meet the high-efficiency brazing coating work of large-sized and complex components.

[0003] Tungsten inert gas welding has the advantages of mature welding technology, strong operability, strong adaptability, etc. It has been maturely applied in engineering and can overcome the problems of complex workpiece coating and long coating pre-setting cycle in traditional brazing coating technology. However, for the diamond wear-resistant particles used in the present invention, the welding arc temperature of traditional tungsten inert gas welding is too high, and diamonds are carbonized or gasified under the action of the arc, which is easy to burn and difficult to effectively transition into the coating.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The first purpose of the present invention is to provide an in-situ brazing coating method for diamond metal composite coating, so as to solve the technical problems that the conventional brazing coating technology is complicated, the workpiece coating is difficult to preset and the preset cycle is long, and the conventional tungsten inert gas shielded welding has high arc temperature and diamond is easy to burn. The method of the present invention adopts hollow tungsten arc welding, and brazing coating is performed by coaxially conveying diamond and cooperating with double-sided wire feeding process, which can optimize the temperature distribution of the molten pool, can completely melt the coating metal, ensure the coating quality, and avoid the diamond ablation problem caused by excessively high arc temperature, and can effectively improve the wear resistance of the coating.

[0006] The second object of the present invention is to provide a composite coating obtained by brazing using the in-situ brazing coating method of the diamond-metal composite coating as described above.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] An in-situ brazing coating method for a diamond-metal composite coating comprises the following steps:

[0009] S1. Diamond particles are used as a core component to make a flux-cored welding wire;

[0010] S2. Use hollow tungsten electrode arc welding to braze coat the surface of the workpiece substrate, feed the flux-cored welding wire through the wire feeding cavity in the center of the hollow tungsten electrode, and feed Cr welding wire and Ni welding wire from both sides of the hollow tungsten electrode along the brazing direction, so that the ends of the Cr welding wire and the Ni welding wire are located in the arc between the annular end face of the electron emitting end of the hollow tungsten electrode and the workpiece substrate, and inert gas is introduced during the brazing process to protect the brazing coating area.

[0011] Preferably, the flux core of the flux-cored welding wire comprises the following components by mass percentage: 25%-35% Si powder, 10%-20% Mn powder, 5%-10% B powder, 5%-15% graphite, and 30%-50% diamond particles.

[0012] Preferably, the coating of the flux-cored welding wire is steel coating.

[0013] Preferably, the diamond particles have a particle size of 25-75 μm.

[0014] Preferably, the filling rate of the flux core in the flux-cored welding wire is 60wt%-80wt%.

[0015] Preferably, the coating thickness of the flux-cored welding wire accounts for 1 / 4-2 / 3 of the radius of the flux-cored welding wire.

[0016] Preferably, the diameter of the Cr welding wire is 0.8-2.4 mm.

[0017] Preferably, the diameter of the Ni welding wire is 0.8-2.4 mm.

[0018] Preferably, the wire feeding speed ratio of the Cr welding wire and the Ni welding wire is 1:2-1:6.

[0019] Preferably, the mass ratio of Cr element to Ni element in the coating obtained after brazing is Cr:Ni=1:3.5-14.

[0020] Preferably, the hollow tungsten pole is a variable diameter hollow tungsten pole, and the electron emitting end of the hollow tungsten pole is in a trumpet shape.

[0021] Preferably, the inner diameter of the electron emission end of the hollow tungsten pole is 2.4-6.4 mm.

[0022] Preferably, the welding voltage of the hollow tungsten arc welding is 17-20V, and the welding current is 140-360A.

[0023] Preferably, the welding speed of the hollow tungsten arc welding is 80-120 mm / min.

[0024] Preferably, during the brazing process, the outer ring temperature of the molten pool is 2000-2200°C.

[0025] A composite coating is obtained by brazing using the in-situ brazing coating method for a diamond-metal composite coating described in any one of the aforementioned embodiments.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The method of the invention adopts hollow tungsten electrode arc welding for brazing coating, and diamond particles are made into flux-cored welding wire and fed through a wire feeding cavity in the center of the hollow tungsten electrode. During the brazing coating process, no arc is generated in the center of the tungsten electrode, and the temperature is relatively low, so that the burning of the diamond sent from the center of the tungsten electrode can be avoided. The arc is only generated in the outer circle of the hollow tungsten electrode, and the temperature of the outer circle of the molten pool is relatively high. The high-melting-point Cr welding wire and the Ni welding wire are fed from both sides of the hollow tungsten electrode along the brazing coating direction, and the high-melting-point Cr welding wire and the Ni welding wire are melted by the high temperature generated by the outer circle arc. After the Cr and Ni are melted, they are quickly diffused into the molten pool to form a uniform coating. The method can optimize the temperature distribution of the molten pool through the hollow tungsten electrode arc welding combined with a reasonable wire feeding method, so that the high-melting-point metal can be melted to ensure the brazing coating quality, and the problem that the arc temperature of conventional arc welding is too high and the molten pool temperature is too high and the diamond is easily ablated can be effectively improved, and the wear resistance of the coating and the stability of the coating under extreme working conditions are effectively improved.

[0028] The brazing coating method of the present invention has high production efficiency and process flexibility, and is applicable to workpiece surfaces of various shapes, including planes, curved surfaces and complex three-dimensional structures. Since it can significantly improve the wear resistance of the coating, reduce the energy consumption during the brazing coating process, and has good automatic operability, it has broad application prospects in the fields of aerospace, oil drilling, mining, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A schematic diagram of an in-situ brazing coating method provided by an embodiment of the present invention;

[0031] Figure 2 This is the coating obtained after brazing in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0033] like Figure 1 As shown, the first aspect of the present invention provides an in-situ brazing method for a diamond metal composite coating, comprising the following steps:

[0034] S1. Diamond particles are used as a core component to make a flux-cored welding wire;

[0035] S2. Use hollow tungsten electrode arc welding to braze coat the surface of the workpiece substrate. Feed the flux-cored welding wire through the wire feeding cavity in the center of the hollow tungsten electrode, and feed the Cr welding wire and Ni welding wire from both sides of the hollow tungsten electrode along the brazing direction, so that the ends of the Cr welding wire and the Ni welding wire are located in the arc between the annular end face of the electron emitting end of the hollow tungsten electrode and the workpiece substrate. During the brazing process, inert gas is introduced to protect the brazing area.

[0036] The present invention adopts diamond as the core strengthening phase of the coating to improve the wear resistance of the coating, Cr is used to provide the strength of the brazing coating, and Ni is used to improve the wettability and alloying effect of the coating. However, due to the high melting points of Cr and Ni, the required brazing temperature is high, diamond is easily ablated, and the wear resistance of the coating is limited. In view of this problem, the present invention adopts hollow tungsten electrode arc welding for brazing coating. During the brazing coating process, no arc is generated at the center of the tungsten electrode, and the temperature in the middle of the molten pool is relatively low. A flux-cored welding wire containing diamond particles is fed into the middle of the molten pool with a relatively low temperature through a wire feeding cavity in the center of the hollow tungsten electrode to avoid or reduce the diamond ablation phenomenon and ensure the wear resistance of the diamond particles. The arc is only generated at the outer ring of the hollow tungsten electrode, and the temperature of the outer ring of the molten pool is relatively high. A high-melting-point Cr welding wire and a Ni welding wire are fed from both sides of the hollow tungsten electrode along the brazing coating direction, and the high-melting-point Cr welding wire and the Ni welding wire are melted by the high temperature generated by the outer ring arc. After the Cr and Ni are melted, they quickly diffuse into the molten pool to form a uniform coating. The method of the present invention utilizes the characteristic that no arc is generated in the center of the hollow tungsten electrode, designs a reasonable wire feeding method, optimizes the temperature distribution of the molten pool, avoids overheating of the molten pool, thereby reducing the graphitization and carbonization problems of diamond particles and the risk of diamond ablation. At the same time, the arc generated by the outer ring ensures the stability of the molten pool, ensures the quality of the brazing coating, and effectively improves the wear resistance of the composite coating.

[0037] The method of the invention has simple process and high brazing coating efficiency, which can avoid the problems of arc ablation of diamond, molten pool ablation of diamond and non-wear resistance of base material in conventional arc welding, and can solve the shortcomings of brazing coating technology, greatly promote the development of brazing coating technology towards high productivity, and expand the application scope of brazing coating technology.

[0038] In some specific embodiments of the present invention, the flux core of the flux-cored welding wire comprises the following components by mass percentage: 25%-35% Si powder, 10%-20% Mn powder, 5%-10% B powder, 5%-15% graphite powder, and 30%-50% diamond particles.

[0039] The addition of Si powder and Mn powder can promote the formation of brazing alloy, and contribute to deoxidation, prevent the formation of oxides, reduce the graphitization of diamond, and enhance the strength of the brazing coating; B powder can effectively reduce the temperature of the molten pool, control the grain refinement of the coating, and improve the wear resistance of the brazing coating; graphite can mainly absorb oxygen, promote the dispersion of diamond particles, avoid excessive carburization reaction in the molten pool, and react with chromium to form chromium carbide hard phase; diamond particles are the core strengthening phase, and the content of diamond particles generally accounts for 5% to 15% of the total mass of the coating. The Ni welding wire and Cr welding wire fed from both sides react with Si, Mn, B, steel skin and other elements in the flux-cored welding wire to form a brazing alloy matrix, and react with diamond particles to finally achieve a uniform distribution of hard phases such as diamond and chromium carbide, greatly improving the wear resistance of the brazing coating.

[0040] In some embodiments, typically but not limiting, for example, the mass percentage of Si powder in the core can be any value among 25%, 26%, 28%, 30%, 32%, 34%, 35%, or a range consisting of any two values; the mass percentage of Mn powder can be any value among 10%, 12%, 14%, 16%, 18%, 20%, or a range consisting of any two values; the mass percentage of B powder can be any value among 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two values; the mass percentage of graphite powder can be any value among 5%, 7%, 9%, 10%, 12%, 15%, or a range consisting of any two values; the mass percentage of diamond particles can be any value among 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, or a range consisting of any two values.

[0041] In some specific embodiments of the present invention, the coating of the flux-cored welding wire is a steel coating. As an example, the steel coating used may be low-carbon steel (carbon steel with a carbon content of less than 0.25 wt %).

[0042] In some specific embodiments of the present invention, the particle size of the diamond particles is 25-75 μm, for example, it can be any point value among 25 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 75 μm or a range value consisting of any two point values; and ensure that the particles are uniform and there are no obvious cracks or damage on the surface. If the particle size of the diamond particles is too small, the specific surface area is large, the contact area with the molten pool is large, and there are many defects caused by the reaction; if the diamond particles are too large, they are easy to gather on the surface of the coating and difficult to be evenly dispersed inside the coating, and the coating has a weak holding force on the diamond particles, and the diamonds are easy to fall off; if the diamond particle size is too large or too small, it will affect the wear resistance of the coating.

[0043] In some specific embodiments of the present invention, the particle size of Si powder, Mn powder, B powder and graphite powder is 80-200 mesh. For example, each raw material powder can be independently selected from any point value of 80 mesh, 100 mesh, 120 mesh, 140 mesh, 160 mesh, 180 mesh, 200 mesh or a range value consisting of any two point values.

[0044] In some specific embodiments of the present invention, the filling rate of the flux core in the flux-cored welding wire (the mass percentage of the flux core in the flux-cored welding wire) is 60wt%-80wt%, for example, it can be any point value among 60wt%, 65wt%, 70wt%, 75wt%, 80wt% or a range value composed of any two point values.

[0045] In some specific embodiments of the present invention, the coating thickness of the flux-cored welding wire accounts for 1 / 4-2 / 3 of the radius of the flux-cored welding wire. For example, it can be any point value among 1 / 4, 1 / 3, 1 / 2, 3 / 5, 2 / 3, or a range value consisting of any two point values.

[0046] In some specific embodiments of the present invention, the coating thickness of the flux-cored welding wire is 0.4-1.0 mm, for example, it can be any point value among 0.4 mm, 0.6 mm, 0.8 mm, and 1.0 mm, or a range value consisting of any two point values; the diameter of the flux-cored welding wire is 1.2-3.2 mm, for example, it can be any point value among 1.2 mm, 1.6 mm, 2.0 mm, 2.4 mm, 2.8 mm, and 3.2 mm, or a range value consisting of any two point values.

[0047] In some specific embodiments of the present invention, the diameter of the Cr welding wire used is 0.8-2.4 mm, for example, it can be any point value among 0.8 mm, 1.0 mm, 1.2 mm, 1.6 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.4 mm, or a range value consisting of any two point values.

[0048] In some specific embodiments of the present invention, the diameter of the Ni welding wire used is 0.8-2.4 mm, for example, it can be any point value among 0.8 mm, 1.0 mm, 1.2 mm, 1.6 mm, 1.8 mm, 2.0 mm, 2.2 mm, 2.4 mm, or a range value consisting of any two point values.

[0049] In some specific embodiments of the present invention, the Cr welding wire is a pure Cr wire.

[0050] In some specific embodiments of the present invention, the Ni welding wire is a pure Ni wire.

[0051] In some specific embodiments of the present invention, the wire feeding speed ratio of the Cr welding wire and the Ni welding wire is 1:2-1:6, for example, it can be any point value among 1:2, 1:3, 1:4, 1:5, 1:6 or a range value consisting of any two point values.

[0052] The wire feeding speed can be set according to the required mass ratio of Cr and Ni elements in the coating. For example, when the wire diameters of Cr welding wire and Ni welding wire are 0.8-2.4mm, the wire feeding speeds of Cr welding wire and Ni welding wire are usually controlled at 1:2-1:6. The wire feeding speed can also be flexibly adjusted according to the thickness requirements of the brazing coating and the distribution of diamond particles to ensure the stability of the molten pool and the quality of the coating.

[0053] The wire diameter and wire feeding speed of the Cr welding wire and the Ni welding wire are controlled mainly to control the mass ratio of the Cr element and the Ni element in the coating. In some specific embodiments of the present invention, the mass ratio of the Cr element and the Ni element in the coating obtained after brazing is Cr:Ni=1:3.5-14. For example, the mass ratio of the Cr element and the Ni element in the coating can be any point value among 1:3.5, 1:5, 1:8, 1:10, 1:12, 1:14 or a range value consisting of any two point values.

[0054] The present invention adopts a double-sided wire feeding process, and by adjusting the wire feeding speed, the molten pool temperature and metal composition can be accurately controlled, thereby avoiding the phenomenon of overheating of the molten pool and further reducing the graphitization and carbonization problems of diamond particles.

[0055] In some specific embodiments of the present invention, the horizontal angle between the wire feeding direction of the Cr welding wire and the Ni welding wire and the brazing coating direction is between 30° and 75°. Within this range, wire feeding is easier to operate and the wire feeding amount is convenient to control.

[0056] In some specific embodiments of the present invention, the inner diameter of the electron emitting end of the hollow tungsten electrode is 2.4-6.4 mm, for example, it can be any point value among 2.4 mm, 3 mm, 4.0 mm, 5.0 mm, 6.0 mm, and 6.4 mm, or a range value consisting of any two point values; if the inner diameter of the electron emitting end is too small, the core temperature is too high, and the diamond is easily ablated; if the inner diameter of the electron emitting end is too large, the core temperature is too low, and the flux-cored wire is difficult to melt.

[0057] In some specific embodiments of the present invention, the hollow tungsten electrode used for hollow tungsten electrode arc welding is a variable diameter hollow tungsten electrode, and the electron emitting end of the hollow tungsten electrode is in a trumpet shape, the purpose of which is to match the inner diameter of the hollow tungsten electrode wire feeding cavity with the size of the flux-cored welding wire, while increasing the inner diameter of the hollow tungsten electrode electron emitting end, reducing the temperature at the center of the tungsten electrode, and reducing the risk of diamond ablation.

[0058] In some specific embodiments of the present invention, the hollow tungsten electrode is far away from one end of the workpiece substrate ( Figure 1 The outer diameter of the upper end in the middle is 3-4mm, the inner diameter is 1.4-3.4mm, the outer diameter of the electron emission end is 4-8mm, and the inner diameter is 2.4-6.4mm.

[0059] In some specific embodiments of the present invention, the welding voltage of hollow tungsten arc welding is 17-20V, for example, it can be any point value among 17V, 18V, 19V, 20V or a range value consisting of any two point values; the welding current is 140-360A, for example, it can be any point value among 140A, 150A, 180A, 220A, 260A, 300A, 320A, 360A or a range value consisting of any two point values. If the welding voltage and current are too high, the arc temperature is too high, and the diamond is easy to ablate; if the welding voltage and current are too low, the arc temperature is too low, and the high melting point metal component is difficult to melt; therefore, the welding voltage and current need to be reasonably controlled.

[0060] In some specific embodiments of the present invention, the welding speed of the hollow tungsten arc welding is 80-120 mm / min, for example, it can be any point value among 80 mm / min, 90 mm / min, 100 mm / min, 110 mm / min, 120 mm / min, or a range value consisting of any two point values.

[0061] In some specific embodiments of the present invention, during the brazing process, the outer ring temperature of the molten pool is 2000-2200°C, for example, it can be any point value among 2000°C, 2050°C, 2100°C, 2150°C, 2200°C, or a range value consisting of any two point values; if the outer ring temperature is too high, the center temperature of the molten pool will increase, and the diamond will be easily ablated; if the outer ring temperature is too low, the Cr welding wire and the Ni welding wire will be difficult to melt.

[0062] In some specific embodiments of the present invention, after the brazing coating is completed, the steps of cooling and coating trimming are also included.

[0063] In some specific embodiments of the present invention, the cooling method is to cool naturally to room temperature to avoid excessive stress or cracking in the coating caused by rapid cooling.

[0064] In some specific embodiments of the present invention, coating finishing is to finish the possible defects on the brazing coating surface, and the finishing can be performed by grinding, laser finishing or mechanical processing to ensure that the coating surface is flat and smooth without obvious defects.

[0065] A second aspect of the present invention provides a composite coating obtained by brazing using the in-situ brazing coating method for a diamond-metal composite coating described in any one of the aforementioned embodiments.

[0066] The following is a detailed description of some embodiments of the present invention in conjunction with specific examples. The raw materials used in the examples can be purchased from the market unless otherwise specified.

[0067] Example 1

[0068] S1. Preparation of flux-cored welding wire

[0069] In terms of mass percentage, the core composition is 26% Si powder, 16% Mn powder, 6% B powder, 10% graphite powder and 42% diamond particles, wherein the particle size of the diamond particles is 50 μm, and the particle sizes of the Si powder, Mn powder, B powder and graphite powder are all 109 μm;

[0070] A flux-cored welding wire with a diameter of 2.0 mm was prepared using low carbon steel as a coating, the coating thickness was 0.6 mm, and the filling rate of the flux core was 75 wt %.

[0071] S2. Hollow tungsten arc welding is used to braze and coat the surface of the workpiece substrate

[0072] The workpiece substrate is 65Mn steel, and the tungsten electrode used is a variable diameter hollow tungsten electrode. The outer diameter of the upper end (the end away from the workpiece substrate) is 4mm, the inner diameter is 3.0mm, and the outer diameter of the lower end (electron emission end) is 6mm, and the inner diameter is 5.0mm; inert gas is used for protection during the brazing and coating process, and the flux-cored wire is fed from the wire feeding cavity in the center of the hollow tungsten electrode, and the wire feeding speed is 40cm / min. A Cr welding wire with a diameter of 1.2mm is fed from the front side along the brazing and coating direction, and the wire feeding speed is 20cm / min. A Ni welding wire with a diameter of 1.2mm is fed from the back side along the brazing and coating direction. The wire feeding speed ratio of the Cr welding wire and the Ni welding wire is 1:6, the welding current is 150A, the arc voltage is 18V, and the welding speed is 100mm / min. During the brazing and coating process, the temperature of the outer circle of the molten pool is 2100℃; after the brazing and coating is completed, it is naturally cooled to room temperature, and the resulting coating is as shown Figure 2 As shown, the black phase is diamond particles, the coating is uniform, and the diamond particles are not severely carbonized or gasified.

[0073] Example 2

[0074] S1. Preparation of flux-cored welding wire

[0075] In terms of mass percentage, the core composition is 32% Si powder, 12% Mn powder, 9% B powder, 7% graphite powder and 40% diamond particles, wherein the particle size of the diamond particles is 25 μm, and the particle sizes of the Si powder, Mn powder, B powder and graphite powder are all 75 μm;

[0076] A flux-cored welding wire with a diameter of 1.6 mm was prepared using low carbon steel as a coating, the coating thickness was 0.4 mm, and the filling rate of the flux core was 60 wt%.

[0077] S2. Hollow tungsten arc welding is used to braze and coat the surface of the workpiece substrate

[0078] The workpiece substrate is 65Mn steel, and the tungsten electrode used is a variable diameter hollow tungsten electrode. The outer diameter of the upper end (the end away from the workpiece substrate) is 3mm, the inner diameter is 2.0mm, and the outer diameter of the lower end (electron emission end) is 4mm, and the inner diameter is 2.4mm; inert gas is used for protection during the brazing and coating process, and the flux-cored wire is fed from the wire feeding cavity in the center of the hollow tungsten electrode at a wire feeding speed of 30cm / min. A Cr welding wire with a diameter of 1.0mm is fed from the front side along the brazing and coating direction at a wire feeding speed of 20cm / min. A Ni welding wire with a diameter of 2.0mm is fed from the back side along the brazing and coating direction. The wire feeding speed ratio of the Cr welding wire and the Ni welding wire is 1:3, the welding current is 260A, the arc voltage is 17V, and the welding speed is 80mm / min. During the brazing and coating process, the temperature of the outer circle of the molten pool is 2000℃; after the brazing and coating is completed, it is naturally cooled to room temperature. The resulting coating is uniform and there is no obvious damage to the diamond particles.

[0079] Example 3

[0080] S1. Preparation of flux-cored welding wire

[0081] In terms of mass percentage, the core composition is 29% Si powder, 13% Mn powder, 7% B powder, 9% graphite powder and 42% diamond particles, wherein the particle size of the diamond particles is 75 μm, and the particle sizes of the Si powder, Mn powder, B powder and graphite powder are all 180 μm;

[0082] A flux-cored welding wire with a diameter of 3.0 mm was prepared using low carbon steel as a coating, the coating thickness was 1.0 mm, and the filling rate of the flux core was 80 wt%.

[0083] S2. Hollow tungsten arc welding is used to braze and coat the surface of the workpiece substrate

[0084] The workpiece substrate is 65Mn steel, and the tungsten electrode used is a variable diameter hollow tungsten electrode. The outer diameter of the upper end (the end away from the workpiece substrate) is 4mm, the inner diameter is 3.4mm, and the outer diameter of the lower end (electron emission end) is 8mm, and the inner diameter is 6.0mm. Inert gas is used for protection during the brazing and coating process. The flux-cored welding wire is fed from the wire feeding cavity in the center of the hollow tungsten electrode at a wire feeding speed of 50cm / min. A Cr welding wire with a diameter of 1.0mm is fed from the front side along the brazing and coating direction at a wire feeding speed of 20cm / min. A Ni welding wire with a diameter of 1.5mm is fed from the back side along the brazing and coating direction. The wire feeding speed ratio of the Cr welding wire and the Ni welding wire is 1:5.5. The welding current is 300A, the arc voltage is 19V, and the welding speed is 120mm / min. During the brazing and coating process, the temperature of the outer circle of the molten pool is 2200℃. After the brazing and coating is completed, it is naturally cooled to room temperature. The diamond particles are evenly distributed on the surface of the workpiece after the brazing and coating treatment, and there is no obvious damage.

[0085] Comparative Example 1

[0086] The difference between Comparative Example 1 and Example 1 is that conventional solid tungsten inert gas shielded welding is used for brazing coating, Cr in an amount equal to that of the Cr welding wire used and Ni in an amount equal to that of the Ni welding wire used are mixed with Si powder, Mn powder, B powder, graphite powder and diamond particles and added to the flux-cored welding wire as flux core components, and during the brazing coating process, the wire is fed from the front side along the brazing coating direction; the other process conditions are the same as Example 1. Since the solid tungsten inert gas shielded welding molten pool temperature is relatively high, diamond ablation is relatively serious and wear resistance is reduced.

[0087] Comparative Example 2

[0088] Comparative Example 2 is similar to Example 1, except that the Cr welding wire and the Ni welding wire do not use the double-side wire feeding process, and directly mix equal amounts of Cr and Ni as flux core components with Si powder, Mn powder, B powder, graphite powder, and diamond particles to form a flux cored welding wire, and feed the flux cored welding wire into the molten pool from the wire feeding cavity at the center of the hollow tungsten electrode, and the other process conditions are the same as Example 1. Due to the low temperature in the middle of the molten pool, Cr and Ni cannot be completely melted, the coating quality is poor, and the wear resistance is significantly reduced.

[0089] Comparative Example 3

[0090] Comparative Example 3 is similar to Comparative Example 2, except that the welding current is 365A, the arc voltage is 21V, and the other process conditions are the same as those of Comparative Example 2. After the current and voltage increase, the temperature in the middle of the molten pool increases, Cr and Ni can be melted, but the diamond ablation is more serious, and the wear resistance is still poor.

[0091] Comparative Example 4

[0092] Comparative Example 4 is similar to Example 1, except that the inner diameter of the lowermost end of the variable diameter hollow tungsten electrode is 7 mm, and the outer diameter is 10 mm, and the other process conditions are the same as those of Example 1. When the welding current and arc voltage remain unchanged, the temperature of the outer ring of the molten pool remains basically unchanged, but due to the excessive inner diameter of the bottom end of the tungsten electrode, the center temperature is too low, the flux-cored wire is not completely melted, the coating quality is poor, and the wear resistance is significantly reduced.

[0093] Comparative Example 5

[0094] Comparative Example 5 is similar to Example 1, except that the inner diameter of the lowermost end of the variable diameter hollow tungsten electrode is 2.2 mm, the outer diameter is 3 mm, and the other process conditions are the same as those of Example 1. When the welding current and arc voltage remain unchanged, the temperature of the outer circle of the molten pool remains basically unchanged, but the center temperature is too high due to the small inner diameter of the bottom end of the tungsten electrode, the diamond is severely ablated, and the wear resistance is still poor.

[0095] Comparative Example 6

[0096] Comparative Example 6 is similar to Example 1, except that the welding current is 380A, the arc voltage is 25V, and the other process conditions are the same as those of Example 1. When the inner diameter of the bottom end of the tungsten electrode remains unchanged, the temperature in the middle of the molten pool is too high due to the excessively high welding current and arc voltage, resulting in severe diamond ablation and poor wear resistance.

[0097] Comparative Example 7

[0098] Comparative Example 7 is similar to Example 1, except that the welding current is 120A, the arc voltage is 15V, and the other process conditions are the same as those of Example 1. Since the welding current and arc voltage are too low, the welding wire is difficult to melt, the brazing coating quality is very poor, and the wear resistance is significantly reduced.

[0099] Test example

[0100] The coatings obtained by brazing in each embodiment and each comparative example were subjected to wear tests respectively. The wear tests were carried out in accordance with the JBT-7705-16995 standard. The weight loss during the wear test for 1 hour was tested under a pressure of 70 N. The test results are shown in Table 1.

[0101] Table 1

[0102]

[0103] It can be seen from the data in Table 1 that, under the same test conditions, compared with Comparative Examples 1 and 2, the wear resistance of the coatings prepared in Examples 1-3 is higher than that of the coatings obtained by traditional solid tungsten electrode welding and hollow tungsten electrode welding without double-sided wire feeding. Compared with Comparative Examples 3-7, the tungsten electrode inner diameter and voltage and current settings of Examples 1-3 are more reasonable, and higher quality coatings can be obtained.

[0104] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. An in-situ brazing coating method for a diamond metal composite coating, characterized in that: The following steps are involved: S1. Diamond particles are used as a core component to make a flux-cored welding wire; S2. Use hollow tungsten electrode arc welding to braze coat the surface of the workpiece substrate, feed the flux-cored welding wire through the wire feeding cavity in the center of the hollow tungsten electrode, and feed Cr welding wire and Ni welding wire from both sides of the hollow tungsten electrode along the brazing direction, so that the ends of the Cr welding wire and the Ni welding wire are located in the arc between the annular end face of the electron emitting end of the hollow tungsten electrode and the workpiece substrate, and inert gas is introduced during the brazing process to protect the brazing coating area.

2. The in-situ brazing coating method of the diamond metal composite coating according to claim 1, characterized in that: Contains at least one of the following characteristics: (1) The flux core of the flux cored welding wire comprises the following components by mass percentage: 25%-35% Si powder, 10%-20% Mn powder, 5%-10% B powder, 5%-15% graphite, and 30%-50% diamond particles; (2) The coating of the flux-cored welding wire is steel coating; (3) The particle size of the diamond particles is 25-75 μm; (4) The filling rate of the flux core in the flux cored welding wire is 60wt% to 80wt%.

3. The in-situ brazing coating method of the diamond metal composite coating according to claim 1, characterized in that: The coating thickness of the flux-cored welding wire accounts for 1 / 4-2 / 3 of the radius of the flux-cored welding wire.

4. The in-situ brazing coating method of the diamond metal composite coating according to claim 1, characterized in that: Contains at least one of the following characteristics: (1) The diameter of the Cr welding wire is 0.8-2.4 mm; (2) The diameter of the Ni welding wire is 0.8-2.4 mm; (3) The wire feeding speed ratio of the Cr welding wire and the Ni welding wire is 1:2-1:6; (4) The mass ratio of Cr element to Ni element in the coating obtained after brazing is Cr:Ni=1:3.5-14.

5. The in-situ brazing coating method of the diamond metal composite coating according to claim 1, characterized in that: The hollow tungsten pole is a variable diameter hollow tungsten pole, and the electron emission end of the hollow tungsten pole is in a trumpet shape.

6. The in-situ brazing coating method of the diamond metal composite coating according to claim 1, characterized in that: The inner diameter of the electron emission end of the hollow tungsten pole is 2.4-6.4 mm.

7. The in-situ brazing coating method of the diamond metal composite coating according to claim 1, characterized in that: The welding voltage of the hollow tungsten arc welding is 17-20V, and the welding current is 140-360A.

8. The in-situ brazing coating method of the diamond metal composite coating according to claim 1, characterized in that: The welding speed of the hollow tungsten arc welding is 80-120 mm / min.

9. The in-situ brazing coating method of the diamond metal composite coating according to claim 1, characterized in that: During the brazing process, the outer ring temperature of the molten pool is 2000-2200°C.

10. A composite coating, characterized in that: The diamond-metal composite coating is obtained by brazing using the in-situ brazing method of any one of claims 1 to 9.

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