Plasma and arc combined metallurgical coating preparation system and method

Abstract

The invention discloses a plasma and arc combined metallurgical coating preparation system and method. The preparation system comprises a plasma spray gun, a plasma spraying device and a plasma spraying device, a positive electrode of the first power supply is connected with a nozzle of the plasma spray gun; the positive electrode of the second power supply is connected with the substrate to be sprayed; wherein the negative electrode of the first power supply and the negative electrode of the second power supply are connected with the cathode of the plasma spray gun at the same time; the preparation method comprises the steps that firstly, a nozzle of a plasma spray gun is connected with the positive electrode of a first power source, a to-be-sprayed base body is connected with the positive electrode of a second power source, and the negative electrode of the first power source and the negative electrode of the second power source are connected with the negative electrode of the plasma spray gun at the same time; secondly, nickel-based alloy powder is sprayed to the to-be-sprayed base body through a plasma spray gun; the powder feeding mode adopted by the plasma spray gun is internal powder feeding; and thirdly, after spraying is finished, the sprayed base body is cooled to the room temperature, and the metallurgical coating prepared through plasma combined arc is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of coating preparation, and in particular relates to a plasma combined arc metallurgical coating preparation system and method. Background Art

[0002] At present, surface treatment technology is a surface engineering technology widely used in the fields of machinery manufacturing, aerospace, petroleum, steel, military, etc., which is important for the manufacture of new products and the repair of old products. The coating formed by it has low bonding strength at the interface of substrate / coating, and is mostly mechanically embedded. With the upgrading of equipment and the improvement of overall performance, the development of composite coatings with good bonding performance and metallurgical bonding transition layers that minimize residual stress while providing a certain amount of heat input, such as using a metal phase as a primer and spraying sealing coatings and ceramic materials on it, has important scientific significance and application value in improving the bonding strength at the coating interface, improving the performance of components, and extending the service life of equipment.

[0003] Under widely used surface treatment technologies such as plasma spraying and laser cladding, the coatings obtained can strengthen the surface of workpieces to a certain extent and improve their mechanical and tribological properties, but there are still certain limitations. The coating obtained by plasma spraying is mechanically bonded to the substrate surface, and the bonding between the coating and the substrate is poor. The plasma cladding coating has a large internal residual stress due to excessive heat input, which is easy to cause crack propagation problems. The coating obtained by laser cladding technology has a small application range and is not suitable for cladding the inner wall of holes less than 350mm. In addition, due to the internal crack problem of the coating, the coating material type is greatly limited and the hardness is also low. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a plasma combined arc metallurgical coating preparation system, which can generate a combined arc of a plasma transferred arc and a non-transferred arc, and realize the preparation of a metallurgical coating through the combined arc.

[0005] The present invention also provides a method for preparing a plasma combined arc metallurgical coating, which utilizes a "combined arc" of a plasma transferred arc and a non-transferred arc to heat and melt the sprayed powder to form a metallurgical coating on the surface of a substrate, thereby improving the density, bonding strength and hardness of the metallurgical coating and reducing the residual stress inside the metallurgical coating.

[0006] The technical solution provided by the present invention is:

[0007] A plasma combined arc metallurgical coating preparation system, comprising:

[0008] Plasma spray gun;

[0009] A first power source, the positive electrode of which is connected to the nozzle of the plasma spray gun;

[0010] a second power source, the positive electrode of which is connected to the substrate to be sprayed;

[0011] Wherein, the negative electrode of the first power supply and the negative electrode of the second power supply are simultaneously connected to the cathode of the plasma spray gun.

[0012] Preferably, the first power source is a non-transferred arc power source, and the second power source is a transferred arc power source.

[0013] A plasma combined arc metallurgical coating preparation method, using the plasma combined arc metallurgical coating preparation system, comprises the following steps:

[0014] Step 1, connecting the nozzle of the plasma spray gun to the positive electrode of the first power supply, connecting the substrate to be sprayed to the positive electrode of the second power supply, and connecting the negative electrode of the first power supply and the negative electrode of the second power supply to the cathode of the plasma spray gun at the same time;

[0015] Step 2: spraying nickel-based alloy powder onto the substrate to be sprayed using a plasma spray gun;

[0016] Wherein, the powder feeding method adopted by the plasma spray gun is internal powder feeding;

[0017] Step 3: After spraying, the sprayed substrate is cooled to room temperature to obtain a metallurgical coating prepared by plasma combined arc.

[0018] Preferably, before step 1, the method further includes pre-treating the substrate to be sprayed, the method being:

[0019] After the substrate to be sprayed is roughened by sandblasting, it is cleaned with anhydrous ethanol.

[0020] Preferably, when the nickel-based alloy powder is NiCr powder, the particle size of the NiCr powder is 15 μm to 45 μm.

[0021] Preferably, when the nickel-based alloy powder is NiAl powder, the particle size of the NiAl powder is 75 μm to 250 μm.

[0022] Preferably, in step 2, the distance between the nozzle of the plasma spray gun and the substrate to be sprayed is 15 to 45 mm.

[0023] Preferably, in step 2, the spray angle of the plasma spray gun is 90°, and the scanning speed is 80 cm / min to 500 cm / min.

[0024] Preferably, in step 2, argon is used as the main gas with a flow rate of 20 L / min to 50 L / min and an operating pressure of 0.8 MPa to 1.5 MPa.

[0025] The beneficial effects of the present invention are:

[0026] The plasma combined arc metallurgical coating preparation system provided by the present invention can generate a combined arc of a plasma transferred arc and a non-transferred arc, and realizes the preparation of the metallurgical coating through the combined arc.

[0027] The plasma combined arc metallurgical coating preparation method provided by the present invention is applicable to a wide range of material systems, and can be applied to the spraying of powders that do not undergo self-exothermic reactions, and can also be applied to powders that undergo self-exothermic reactions.

[0028] The plasma combined arc metallurgical coating preparation method provided by the present invention combines the advantages of transfer type and non-transfer type plasma arc, and can make the surface temperature of the substrate higher than that of plasma spraying, so that the bonding performance of the coating is better; compared with the plasma cladding coating, the preparation of the combined arc cladding coating increases the distance between the spray gun and the substrate on the basis of ensuring the stability of the arc, and the heat input of the substrate is smaller, the residual stress of the prepared coating is reduced, cracking is not easy to occur, and the substrate is not easy to deform. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the plasma combined arc metallurgical coating preparation system described in the present invention.

[0030] Figure 2 (a) is a particle size distribution diagram of the NiCr alloy powder used in Example 1 of the present invention.

[0031] Figure 2 (b) is a microscopic morphology of the NiCr alloy powder used in Example 1 of the present invention.

[0032] Figure 3 (a) is a cross-sectional morphology of the plasma combined arc NiCr coating prepared in Example 1 of the present invention.

[0033] Figure 3 (b) is a schematic diagram of EDS spectrum analysis of the plasma combined arc NiCr coating prepared in Example 1 of the present invention.

[0034] Figure 4 (a) is a particle size distribution diagram of the NiAl alloy powder used in Example 2 of the present invention.

[0035] Figure 4 (b) is a microscopic morphology image of the NiAl alloy powder used in Example 2 of the present invention.

[0036] Figure 5 (a) is a cross-sectional morphology of the plasma combined arc NiAl coating prepared in Example 2 of the present invention.

[0037] Figure 5(b) is a schematic diagram of EDS energy spectrum analysis of the plasma combined arc NiAl coating prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0039] like Figure 1 As shown, the present invention provides a plasma combined arc metallurgical coating preparation system, comprising: a plasma spray gun; a first power supply, whose positive electrode is connected to the nozzle of the plasma spray gun; a second power supply, whose positive electrode is connected to the substrate to be sprayed; wherein the negative electrode of the first power supply and the negative electrode of the second power supply are simultaneously connected to the cathode of the plasma spray gun.

[0040] The present invention also provides a plasma combined arc metallurgical coating preparation method, and the plasma combined arc metallurgical coating preparation system is used to prepare the coating. The specific implementation process is as follows.

[0041] 1. Pre-treat the surface of the substrate to be sprayed.

[0042] The pretreatment method is: roughening the substrate to be sprayed by sandblasting, and then cleaning it with anhydrous ethanol.

[0043] Wherein, the matrix material is low carbon steel, preferably Q235 steel.

[0044] 2. Fix the substrate to be sprayed on the platform, connect the nozzle of the plasma spray gun to the positive electrode of the first power supply, connect the substrate to be sprayed to the positive electrode of the second power supply, and connect the negative electrode of the first power supply and the negative electrode of the second power supply to the cathode of the plasma spray gun at the same time.

[0045] Among them, the first power supply is a non-transferred arc power supply for generating a non-transferred arc voltage and a non-transferred arc current; the second power supply is a transferred arc power supply for generating a transferred arc voltage and a transferred arc current.

[0046] A plasma spray gun is used to spray nickel-based alloy powder onto the substrate to be sprayed; the nickel-based alloy powder can be non-reactive nickel-based alloy powder (such as NiCr alloy powder) or nickel-based alloy powder with self-exothermic reaction performance (such as NiAl alloy powder), and the dust collector is turned on during the spraying process.

[0047] The plasma combined arc metallurgical coating preparation method provided by the present invention adopts an internal powder feeding method. Under the action of the non-transferred arc, the powder begins to heat inside the spray gun, and then is heated and melted by the plasma arc during flight, and hits the substrate at a certain speed. In this way, the particles are in a molten or semi-molten state before hitting the substrate, and collide with the substrate close to the liquid phase metal to form a liquid-liquid mixture, which is more uniform than the solid-liquid mixture of solid particles and the substrate metal, so that the coating obtained after the mixed liquid phase solidifies tends to be more dense and uniform, and the coating is more closely combined with the substrate, tending to be metallurgical.

[0048] The distance between the substrate and the spray gun (nozzle) in the plasma combined arc metallurgical coating preparation method provided by the present invention is different from that in plasma cladding and plasma spraying. In the plasma spraying operation, the spraying distance is about 100mm; in the plasma cladding process, the distance between the substrate and the spray gun is relatively close, less than 15mm; while in the plasma combined arc technology operation, the distance is greater than 15mm, generally less than 45mm, that is, the distance between the nozzle of the plasma spray gun and the substrate to be sprayed is 15-45mm. The surface temperature of the substrate using the plasma combined arc metallurgical coating preparation method is lower than that of plasma cladding. Although the surface of the substrate will also be melted, the substrate is mostly heated to a just softened liquid state. Particles with a certain temperature and speed form a micro-metallurgical bond with the surface of the substrate. The substrate will not be deformed due to excessive heat input, and the phenomenon of droplet splashing when the particles hit the substrate is avoided; while the surface temperature of the substrate of plasma spraying is lower than that of the plasma combined arc metallurgical coating preparation method, the heat input to the substrate is small, and the coating is mechanically bonded to the substrate surface. Therefore, the plasma combined arc technology combines the metallurgical bonding characteristics of plasma cladding technology and the advantages of non-transferred arc heating of plasma spraying technology. By controlling a certain operating distance, high heat input is avoided, residual stress in the coating is reduced, and particles are prevented from forming droplets when they hit the substrate.

[0049] 3. After spraying is completed, the sprayed substrate (workpiece) is naturally cooled to room temperature in the air to obtain a plasma combined arc metallurgical coating.

[0050] Preferably, the particle size of the NiCr powder is 15 μm to 45 μm.

[0051] Preferably, the particle size of the NiAl powder is 75 μm to 250 μm.

[0052] As a preferred embodiment, argon is used as the main gas with a pressure of 0.8 to 1.5 MPa and a flow rate of 20 to 50 L / min; hydrogen is used as the auxiliary gas with a pressure of 0.8 to 1.3 MPa and a flow rate of 0 to 15 L / min.

[0053] As a preferred embodiment, the non-transferred arc voltage is 30-50V, and the transferred arc voltage is 85-180V.

[0054] As a preferred embodiment, the non-transferred arc current is 180-350A, and the transferred arc current is 30-80A.

[0055] As a preferred embodiment, air is used as the powder feeding gas, the powder feeding gas pressure is 0.05-1 MPa, the powder feeding gas flow rate is 2-15 L / min, and the powder feeding rate is 5-30 g / min.

[0056] As a preference, the scanning speed of the plasma spray gun is 80 cm / min to 500 cm / min.

[0057] As a preference, the spray angle of the plasma spray gun is 90°, and the spray angle is the angle between the plasma jet and the surface of the substrate.

[0058] The gas flow rate of plasma cladding technology is relatively small, and it is directly transported to the substrate molten pool under the action of plasma non-transferred arc; while the gas flow rate of plasma spraying is about 100L / min; the gas flow rate used in the plasma combined arc metallurgical coating preparation method provided by the present invention is relatively large compared with plasma cladding, and relatively small compared with plasma spraying, which is 20-50L / min. Under this airflow, the powder particles have a certain speed and melting degree before reaching the substrate, and then collide with the substrate micro-molten pool that is heated and melted under the action of the transferred arc and mix with it.

[0059] The specific spraying parameters are shown in Table 1.

[0060] Table 1 Spraying parameters of metallurgical coating prepared by plasma combined arc

[0061]

[0062] Example 1

[0063] Pre-treat the surface of the substrate to be sprayed to remove stains and oil stains on the surface.

[0064] The substrate (workpiece) to be sprayed is fixed on the platform and kept horizontally parallel to the moving direction of the spray gun; the NiCr coating is sprayed on the surface of the workpiece using a plasma combined arc metallurgical coating preparation system.

[0065] The substrate (workpiece) is made of Q235 steel, the spray powder is made of alloy powder NiCr, the particle size is 15-45μm, the powder particle size distribution and microscopic morphology are as follows: Figure 2 The specific spraying parameters are shown in Table 2.

[0066] After spraying is completed, wait for the substrate (workpiece) to cool naturally to room temperature.

[0067] Table 2 Parameters of NiCr coating prepared by plasma combined arc

[0068]

[0069] Example 2

[0070] Pre-treat the surface of the substrate to be sprayed to remove stains and oil stains on the surface.

[0071] The substrate (workpiece) to be sprayed is fixed on the platform and kept horizontally parallel to the moving direction of the spray gun; the NiCr coating is sprayed on the surface of the workpiece using a plasma combined arc metallurgical coating preparation system.

[0072] The substrate (workpiece) is made of Q235 steel, the spray powder is made of alloy powder NiAl, the particle size is 75 to 250 μm, the powder particle size distribution and microscopic morphology are as follows: Figure 4 The specific spraying parameters are shown in Table 3.

[0073] After spraying is completed, wait for the substrate (workpiece) to cool naturally to room temperature.

[0074] Table 3 Parameters of NiAl coating prepared by plasma combined arc

[0075]

[0076] The chemical composition of the Q235 low carbon steel used in Examples 1-2 is shown in Table 4.

[0077] Table 4 Chemical composition of Q235 low carbon steel

[0078] chemical composition C Mn Si S P content / % 0.15～0.22 0.3～0.65 ≤0.35 ≤0.050 0.045

[0079] like Figure 3 As shown, the cross-sectional SEM micromorphology and EDS spectrum analysis of the NiCr coating prepared on the Q235 substrate in Example 1 show that a partial transition is formed at the interface between the coating and the substrate, resulting in a corresponding metallurgical bond. In addition, during the bonding strength test, there is no cracking between the coating and the substrate, and the bonding strength between the layers inside the coating can reach 54MPa, which is higher than the 30MPa of the coating produced by plasma spraying technology. Figure 5 As shown, the metallurgical bonding between the NiAl coating prepared in Example 2 and the substrate interface is more obvious, and the bonding strength between the internal layers of the NiAl coating of Example 2 can reach 50 MPa compared to the coating bonding strength of 40 MPa by plasma spraying technology. This shows that the technology proposed in the present invention can form NiCr coatings and NiAl coatings with good metallurgical bonding, further proving the feasibility of the present invention.

[0080] Compared with the plasma cladding technology, the plasma combined arc metallurgical coating preparation method provided by the present invention has a greater distance between the coating substrate and the spray gun, and has a smaller thermal impact on the substrate on the basis of forming a metallurgical bond; compared with plasma spraying, the gas flow rate is low, the power is low, the interface between the coating and the substrate is metallurgically bonded, the bonding strength is good, and the energy utilization rate is higher. The composite coating obtained by the plasma combined arc metallurgical coating preparation method provided by the present invention is dense, has good bonding strength, high hardness, and small residual stress inside the coating, which greatly reduces the cracking tendency of the coating and improves the wear resistance of the coating.

[0081] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A plasma combined arc metallurgical coating preparation system, characterized in that: include: Plasma spray gun; A first power source, the positive electrode of which is connected to the nozzle of the plasma spray gun; a second power source, the positive electrode of which is connected to the substrate to be sprayed; Wherein, the negative electrode of the first power supply and the negative electrode of the second power supply are simultaneously connected to the cathode of the plasma spray gun.

2. The plasma combined arc metallurgical coating preparation system according to claim 1, characterized in that: The first power source is a non-transferred arc power source, and the second power source is a transferred arc power source.

3. A plasma combined arc metallurgical coating preparation method, using the plasma combined arc metallurgical coating preparation system as described in any one of claims 1-2, characterized in that: The steps include: Step 1, connecting the nozzle of the plasma spray gun to the positive electrode of the first power supply, connecting the substrate to be sprayed to the positive electrode of the second power supply, and connecting the negative electrode of the first power supply and the negative electrode of the second power supply to the cathode of the plasma spray gun at the same time; Step 2: spraying nickel-based alloy powder onto the substrate to be sprayed using a plasma spray gun; Wherein, the powder feeding method adopted by the plasma spray gun is internal powder feeding; Step 3: After spraying, the sprayed substrate is cooled to room temperature to obtain a metallurgical coating prepared by plasma combined arc.

4. The method for preparing a plasma combined arc metallurgical coating according to claim 3, characterized in that: Prior to step 1, the substrate to be sprayed is pretreated by: After the substrate to be sprayed is roughened by sandblasting, it is cleaned with anhydrous ethanol.

5. The method for preparing a plasma combined arc metallurgical coating according to claim 4, characterized in that: When the nickel-based alloy powder is NiCr powder, the particle size of the NiCr powder is 15 μm to 45 μm.

6. The method for preparing a plasma combined arc metallurgical coating according to claim 4 or 5, characterized in that: When the nickel-based alloy powder is NiAl powder, the particle size of the NiAl powder is 75 μm to 250 μm.

7. The method for preparing a plasma combined arc metallurgical coating according to claim 6, characterized in that: In the step 2, the distance between the nozzle of the plasma spray gun and the substrate to be sprayed is 15 to 45 mm.

8. The method for preparing a plasma combined arc metallurgical coating according to claim 7, characterized in that: In the step 2, the spray angle of the plasma spray gun is 90°, and the scanning speed is 80 cm / min to 500 cm / min.

9. The method for preparing a plasma combined arc metallurgical coating according to claim 8, characterized in that: In the step 2, argon is used as the main gas, with a flow rate of 20L / min to 50L / min and an operating pressure of 0.8MPa to 1.5MPa.

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