Cold spray nozzle and cold spray device

Abstract

To provide a nozzle for cold spray that can jet a powder material in a direction intersecting a direction in which a supplied working gas flows and prevent clogging, and to provide a cold spray device.SOLUTION: A nozzle for cold spray includes: a gas introduction port 21 installed so as to be capable of introducing a working gas supplied from a gas supply part 11 into a flow channel; a nozzle contraction part 22 having a flow channel whose internal diameter is formed so as to be smaller than an internal diameter of the gas introduction port 21; a nozzle enlarged part 23 having a flow channel whose internal diameter is enlarged from the upstream toward the downstream from the nozzle contraction part 22; and a powder supply port 24 provided in the nozzle enlarged part 23 so as to be capable of supplying a powder material to the flow channel. The nozzle enlarged part 23 includes a spiral part 23a provided so that the flow channel forms a spiral shape from the upstream toward the downstream. A jetting direction of the powder material from an injection port 23c of a tip of the nozzle enlarged part intersects a horizontal direction relative to a direction in which the working gas flows in the nozzle contraction part 22.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a nozzle for cold spray and a cold spray device. [Background technology]

[0002] Conventionally, the cold spray method has been known as a method for forming a coating on the surface of a substrate. The cold spray method is characterized by being able to form a high-quality coating with a small porosity and no oxidation by colliding powder particles in a solid phase with a substrate at or below the melting temperature, and by having a faster coating speed than the thermal spray method. The present inventors have developed a method for forming a film of a polymer material such as a fluororesin on a substrate using the cold spray method to produce a superhydrophobic coating film (see, for example, Patent Document 1 and Non-Patent Documents 1 to 3). The formed hydrophobic coating film can be used to protect the surface of a pipe, for example.

[0003] In forming a film using the cold spray method, it is important to spray the powder material from a vertical direction against the substrate and collide with it, taking into consideration the film formation efficiency and the adhesion strength of the film. For example, when forming a film on the outer wall of a pipe, a general straight nozzle can be used to spray the powder material from a vertical direction against the outer wall surface of the pipe. However, when forming a film on the inner wall of a pipe, depending on the inner diameter of the pipe, it is difficult to spray the powder material from a vertical direction against the inner wall surface of the pipe with a straight nozzle. Therefore, in order to form a film in a place where it is difficult to spray the powder material from a vertical direction, such as the inner wall of a pipe, a nozzle bent into an L-shape to change the spray direction of the powder material is used (see, for example, Non-Patent Document 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6341505 [Non-patent literature]

[0005] [Non-Patent Document 1] Kazuhiro Ogawa, "Development of Polymer Coatings by Cold Spray Method", Journal of the Japan Welding Society, Vol. 82, No. 8, 2013, pp. 5-8 [Non-Patent Document 2] W. L. Sulen, K. Ravi, C. Bernard, Y. Ichikawa, K. Ogawa, “Deposition Mechanism Analysis of Cold Sprayed Fluoropolymer Coatings and Its Wettability Evaluation”, [online], J. Therm. Spray Technol.,8 June 2020, Internet〈URL : https: / / doi.org / 10.1007 / s11666-020-01059-w〉 [Non-Patent Document 3] K. Ravi, WL Sulen, C. Bernard, Y. Ichikawa, K. Ogawa, “Fabrication of micro- / nano-structured super-hydrophobic fluorinated polymer coatings by cold-spray”, Surf. Coat. Technol., 15 September 2019, Vol. 373, p.17-24 [Non-Patent Document 4] Wen-Ya Li and Chang-Jiu Li, “Optimal Design of a Novel Cold Spray Gun Nozzle at a Limited Space”, Journal of Thermal Spray Technology, September 2005, Volume 14(3), p.391-396 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the L-shaped nozzle described in Non-Patent Document 4, a vortex occurs in the working gas carrying the powder material at the bent position, which causes a biased distribution of the powder material in the working gas or the powder material introduced into the working gas after the vortex is generated, and this can lead to accumulation in the nozzle and cause clogging.

[0007] The present invention has been made in light of these problems, and aims to provide a cold spray nozzle and cold spray device that can spray powder material in a direction intersecting the flow direction of the supplied working gas and prevent clogging. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the cold spray nozzle of the present invention is a cold spray nozzle attached to a gas supply unit that supplies a working gas at a temperature lower than the melting point of a powder material, and configured to spray the powder material from a nozzle orifice together with the working gas, and is characterized in that the nozzle has a flow path for flowing the working gas, a gas inlet connected to the gas supply unit and capable of introducing the working gas supplied from the gas supply unit into the flow path, a nozzle contraction section formed downstream of the gas inlet such that an inner diameter of the flow path is smaller than an inner diameter of the gas inlet, a nozzle expansion section provided downstream of the nozzle contraction section such that the inner diameter of the flow path gradually increases from the nozzle contraction section from upstream to downstream, and having an injection port at a tip of the flow path on the downstream side, and a powder supply port provided in the nozzle expansion section such that the powder material can be supplied to the flow path, the nozzle expansion section has a spiral section provided so that the flow path forms a spiral from upstream to downstream, and the injection direction of the powder material from the injection port is configured to intersect a direction parallel to the flow direction of the working gas in the nozzle contraction section.

[0009] The cold spray nozzle according to the present invention is used for forming a coating of a powder material on the surface of a substrate such as a pipe by a cold spray method. The cold spray nozzle according to the present invention can spray the powder material from the nozzle together with the working gas by supplying the powder material from the powder supply port to a working gas that is supplied from a gas supply section to a flow path via a gas inlet and passes from a nozzle contraction section to a nozzle expansion section and is sprayed from the nozzle port.

[0010] The cold spray nozzle according to the present invention is configured such that the spray direction of the powder material from the spray port intersects with a direction parallel to the flow direction of the working gas in the nozzle contraction section via a helical section provided so that the flow path forms a helical shape from upstream to downstream, and the powder material can be sprayed in a direction intersecting with the flow direction of the working gas supplied from the gas inlet. Compared with a nozzle having an L-shaped or other bend, the cold spray nozzle according to the present invention can change the flow direction of the working gas while allowing it to flow smoothly due to the helical section, thereby suppressing the generation of vortexes and preventing clogging due to the powder material.

[0011] The cold spray nozzle according to the present invention can spray powder material in a direction intersecting the flow direction of the working gas supplied from the gas inlet, and therefore can efficiently form a coating even in a place where it is difficult to spray powder material from a vertical direction using a linear nozzle. The cold spray nozzle according to the present invention may be configured using a commercially available Laval nozzle. In this case, for example, a spiral part may be formed on the tip side of the nozzle contraction part of the Laval nozzle, or a spiral part may be attached to the tip of the Laval nozzle. In addition, the nozzle expansion part may have an inner diameter of the flow path that increases continuously from the upstream to the downstream, or may increase in a stepwise manner.

[0012] In the cold spray nozzle according to the present invention, the powder material may be any material that can be used in the cold spray method, such as metal particles, polymer particles, etc. When the powder material is made of polymer particles, it is preferable that the powder material is made of a powder containing hydrophobic fluororesin particles, ultra-high molecular weight polyethylene (UHMWPE), polyimide (PI), etc. Examples of the fluororesin include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), fluorinated ethylene propylene (FEP), ethylene copolymer of tetrafluoroethylene (ETFE), ethylene copolymer of chlorotrifluoroethylene (ECTFE), perfluoroalkoxy (PFA), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), Nafion (registered trademark), fluoroethylenevinylether (FEVE), semicrystalline three-component terpolymers of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, and the like. terpolymer (THV), Teflon (registered trademark) AF, Cytop (registered trademark), Hyflon (registered trademark), etc.

[0013] In the cold spray nozzle according to the present invention, the nozzle expansion part may have any angle between the spray direction of the powder material from the nozzle orifice and the direction parallel to the flow direction of the working gas in the nozzle contraction part, but it is preferable that the angle is such that the powder material can be sprayed in a direction approximately perpendicular to the surface of the target of cold spray. For example, the nozzle expansion part may be configured so that the spray direction of the powder material from the nozzle orifice intersects approximately perpendicularly with the direction parallel to the flow direction of the working gas in the nozzle contraction part. In this case, in particular, the nozzle expansion part can be inserted into the inside of a pipe to spray the powder material from a direction perpendicular to the inner wall surface of the pipe, and a coating can be efficiently formed on the inner wall of the pipe. In this case, the nozzle expansion part does not need to have the spray direction of the powder material from the nozzle orifice form exactly 90 degrees with respect to the flow direction of the working gas in the nozzle contraction part, and may have an angle in the range of, for example, 80 degrees to 100 degrees.

[0014] In the cold spray nozzle according to the present invention, it is preferable that the nozzle expansion section has a direct flow section connected to the downstream side of the helical section so that the flow path smoothly continues from the helical section, and the powder supply port is provided in the direct flow section. In this case, since only the working gas flows through the helical section, it is possible to prevent the powder material from clogging the helical section. In addition, it is possible to suppress the generation of a vortex in the flow of the working gas at the boundary between the helical section and the direct flow section. Therefore, it is possible to prevent the powder material introduced from the powder supply port of the direct flow section from clogging the direct flow section due to the influence of the vortex. In addition, the direct flow section can control the injection direction. It is preferable that the powder supply port is provided upstream of the direct flow section, close to the helical section, in order to increase the injection speed and temperature of the powder material during injection.

[0015] In the cold spray nozzle according to the present invention, it is preferable that the powder material is made of polymer particles having a diameter of 20 μm to 45 μm, the gas supply unit is configured to supply the working gas to the gas inlet at a pressure of 0.4 MP to 0.8 MP, and the helical unit has a length of one helix of 40 mm to 60 mm, a diameter of the helix of 40 mm to 60 mm, and a length along the central axis of the helix of 120 mm to 140 mm. In this case, the injection speed and temperature of the powder material injected from the injection port can be particularly increased, and the film formation efficiency can be improved.

[0016] The cold spray device according to the present invention is characterized by having the cold spray nozzle according to the present invention and the gas supply unit.

[0017] Since the cold spray device of the present invention has the cold spray nozzle of the present invention, it is possible to spray powder material in a direction intersecting the flow direction of the working gas supplied from the gas supply unit to the cold spray nozzle, and to prevent the powder material from clogging the cold spray nozzle. Effect of the Invention

[0018] According to the present invention, it is possible to provide a cold spray nozzle and a cold spray device that can spray powder material in a direction intersecting the flow direction of the supplied working gas and prevent clogging. [Brief description of the drawings]

[0019] [Figure 1] 1A and 1B are a side view and a rear view, respectively, showing a cold spray device according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a side view showing a conventional cold spray device using a straight nozzle. [Diagram 3]2A and 2B are graphs showing the relationship between particle diameter and particle velocity of the powder material and the relationship between particle diameter and particle temperature of the powder material, respectively, as a result of simulations performed when the spiral diameter D (MCD) of the spiral portion of the cold spray device shown in FIG. 1 is changed. [Figure 4] 2A and 2B are graphs showing the relationship between particle diameter and particle velocity of the powder material and the relationship between particle diameter and particle temperature of the powder material, which are simulation results when the length L(AP) of one period of the spiral of the spiral part of the cold spray device shown in FIG. 1 is changed. [Diagram 5] 2A and 2B are graphs showing the relationship between particle diameter and particle velocity of the powder material and the relationship between particle diameter and particle temperature of the powder material, respectively, as a result of simulations performed when the position of the powder supply port of the cold spray device shown in FIG. 1 is changed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 3 to 5 show a cold spray nozzle and a cold spray device according to an embodiment of the present invention. As shown in FIG. 1, the cold spray device 10 has a gas supply unit 11 and a nozzle 12 for cold spray.

[0021] The gas supply unit 11 has a gas supply port 11a and is provided so as to be able to supply a working gas having a temperature lower than the melting point of the powder material for cold spray from the gas supply port 11a to the nozzle 12 for cold spray.

[0022] The cold spray nozzle 12 has a flow path extending from one end to the other end for flowing the working gas supplied from the gas supply unit 11. The cold spray nozzle 12 has a gas inlet 21, a nozzle narrowing section 22, a nozzle enlarging section 23, and a powder supply port 24. The cold spray nozzle 12 is attached to the gas supply unit 11 with the gas inlet 21 connected to the gas supply port 11a so that the gas inlet 21 and the gas supply port 11a of the gas supply unit 11 communicate with each other.

[0023] The gas inlet 21 communicates with the flow path and is provided so that the working gas supplied from the gas supply unit 11 can be introduced into the flow path. The nozzle narrowing section 22 is provided downstream of the gas inlet 21. The nozzle narrowing section 22 is formed so that the inner diameter of the flow path is smaller than the inner diameter of the gas inlet 21.

[0024] The nozzle expansion section 23 is provided downstream of the nozzle reduction section 22, and has a spiral section 23a, a direct flow section 23b, and an injection port 23c. The spiral section 23a is provided so that the flow path forms a spiral shape from upstream to downstream. The direct flow section 23b is provided so that the flow path forms a straight line, and is connected to the downstream side of the spiral section 23a so that the flow path smoothly continues from the spiral section 23a. The injection port 23c is provided at the tip of the direct flow section 23b and at the tip of the flow path. The nozzle expansion section 23 is provided so that the inner diameter of the flow path gradually increases from the nozzle reduction section 22 from upstream to downstream.

[0025] The powder supply port 24 is provided in the direct flow portion 23b of the nozzle enlarged portion 23. A supply pipe 25 for supplying the powder material is connected to the powder supply port 24, and the powder material from the supply pipe 25 can be supplied to the flow path.

[0026] The cold spray nozzle 12 is configured to inject the powder material supplied from the powder supply port 24 from the nozzle outlet 23c together with the working gas supplied from the gas supply unit 11. The cold spray nozzle 12 is configured to accelerate the working gas supplied to the flow path from the gas inlet 21 by passing the working gas from the nozzle contraction section 22 through the nozzle expansion section 23, and then inject it from the nozzle outlet 23c. The cold spray nozzle 12 is configured to change the direction of the flow path at the spiral section 23a, so that the injection direction of the powder material from the nozzle outlet 23c intersects with a direction parallel to the flow direction of the working gas in the nozzle contraction section 22.

[0027] In a specific example shown in FIG. 1, the cold spray nozzle 12 is configured so that the direction of injection of the powder material from the injection port 23c is approximately perpendicular to the direction parallel to the flow direction of the working gas in the nozzle contraction section 22. The cold spray nozzle 12 is configured using a commercially available Laval nozzle, and a spiral section 23a and a straight section 23b are attached to the tip of the Laval nozzle. The nozzle expansion section 23 is configured so that the inner diameter of the flow path is constant in the spiral section 23a, and the inner diameter of the flow path is continuously increased from upstream to downstream in the upstream part of the spiral section 23a and the straight section 23b. The nozzle expansion section 23 may not have the straight section 23b, but may have an injection port 23c at the downstream end of the spiral section 23a, and may have a powder supply port 24 in the spiral section 23a.

[0028] Next, the operation will be described. The cold spray device 10 can form a coating of powder material on the surface of a substrate such as a pipe by a cold spray method using the cold spray nozzle 12. The cold spray nozzle 12 is configured such that the spray direction of the powder material from the spray port 23c intersects with a direction parallel to the flow direction of the working gas in the nozzle reduction section 22 via the helical section 23a, which is provided so that the flow path forms a helical shape from upstream to downstream, and can spray the powder material in a direction intersecting with the flow direction of the working gas supplied from the gas inlet 21. Compared to a nozzle having a bend such as an L-shape, the cold spray nozzle 12 can change the flow direction of the working gas while smoothly flowing it by the helical section 23a, thereby suppressing the generation of vortexes and preventing clogging by the powder material.

[0029] The cold spray nozzle 12 can spray the powder material in a direction intersecting the flow direction of the working gas supplied from the gas inlet 21, and therefore can efficiently form a coating even in places where it is difficult to spray the powder material in a perpendicular direction using a linear nozzle. In particular, the cold spray nozzle 12 is configured to spray the powder material in a direction intersecting approximately perpendicularly to the flow direction of the working gas supplied from the gas inlet 21, and can be inserted into a pipe to spray the powder material in a perpendicular direction to the inner wall surface of the pipe, thereby efficiently forming a coating on the inner wall of the pipe.

[0030] In the cold spray nozzle 12, the powder supply port 24 is provided in the direct flow section 23b, so that only the working gas flows through the helical section 23a, and clogging of the powder material in the helical section 23a can be prevented. In addition, because the flow path smoothly continues from the helical section 23a to the direct flow section 23b, it is possible to suppress the generation of a vortex in the flow of the working gas at the boundary between the helical section 23a and the direct flow section 23b. Therefore, it is possible to prevent the powder material introduced from the powder supply port 24 of the direct flow section 23b from clogging the direct flow section 23b due to the influence of the vortex.

[0031] [simulation] A three-dimensional numerical simulation was performed to investigate the behavior of the working gas and powder material for the cold spray apparatus 10 shown in Fig. 1. For comparison, a similar three-dimensional numerical simulation was performed for a conventional cold spray apparatus 50 using a straight nozzle 51 shown in Fig. 2. As shown in Fig. 2, the cold spray apparatus 50 also uses a Laval nozzle, and the gas supply section 11 of the cold spray apparatus 10 to the gas inlet 21, nozzle contraction section 22, and the upstream section of the nozzle expansion section 23 (position S in Fig. 2) of the cold spray apparatus 10 have the same configuration and shape as the cold spray apparatus 10.

[0032] In the simulation, the effects of the mean coil diameter D (MCD) and the length of one period of the spiral L (Axial pitch: AP) of the spiral portion 23a (range S to E in FIG. 1) of the cold spray nozzle 12 of the cold spray device 10 shown in FIG. 1 on the speed and temperature of the powder material were investigated. The effects of the position of the powder supply port 24 were also investigated.

[0033] In the simulation, the length of the spiral portion 23a of the cold spray device 10 shown in Fig. 1 along the central axis of the spiral was 140 mm, the length from the downstream end of the spiral portion 23a (position E in Fig. 1) to the nozzle orifice 23c (length of the direct current portion 23b) was 60 mm, the inner diameter of the flow path in the nozzle reduction portion 22 was 2 mm, the inner diameter of the flow path in the spiral portion 23a was 4 mm, and the inner diameter of the nozzle orifice 23c was 4.9 mm. In the simulation, calculations were performed for the combinations of D and L shown in Table 1. In addition, in order to prevent the powder material from clogging the spiral portion 23a, the position of the powder supply port 24 was set downstream of the spiral portion 23a, and the distance from the downstream end of the spiral portion 23a (position E in Fig. 1) was changed to 2 mm, 6 mm, and 10 mm, and calculations were performed.

[0034] [Table 1]

[0035] 2, the length from the upstream part of the nozzle expansion section 52 (position S in FIG. 2) to the nozzle outlet 53 was 120 mm, the inner diameter of the flow path at the nozzle contraction section 54 was 2 mm, the inner diameter of the flow path at the upstream part of the nozzle expansion section 52 (position S in FIG. 2) was 4 mm, and the inner diameter of the nozzle outlet 53 was 4.8 mm. The position of the powder supply port 55 was fixed to the upstream part of the nozzle expansion section 52.

[0036] In the three-dimensional numerical simulation, commercially available software "ANSYS Fluent 2020 R2 (manufactured by ANSYS)" was used. In the simulation, the pressure of the working gas supplied from the gas supply unit 11 at the gas inlet 21 was 0.5 MPa and the temperature was 623 K. In addition, the boundary pressure at the injection port 23c was 1 atmosphere, and the pressure at the powder supply port 24 was 1.2 atmosphere. The nozzle inner wall and the surface of the substrate to be injected included in the simulation were insulated and non-slip. In addition, in the cold spray apparatus 50 shown in FIG. 2, the conditions were the same as those of the cold spray apparatus 10 shown in FIG. 1, except that the pressure at the powder supply port 55 was 1 atmosphere.

[0037] In the simulation, the powder material was a polymer resin called perfluoroalkoxy fluororesin (PFA). The particle diameter of the powder material was assumed to be the same for all powder materials, and was varied in the range of 13 μm to 63 μm. The initial position of the powder material was uniformly distributed on the input surface. The initial speed of the powder material was 0 m / s, and the temperature was 300 K. The physical properties of the PFA used in the simulation are shown in Table 2.

[0038] [Table 2]

[0039] In the simulation, the working gas was air, and the ideal gas equation of state was used to consider compressibility. To evaluate the effect of turbulence in the flow field, the conservation of mass, momentum, and energy were used as governing equations. A coupling method with second-order discrete accuracy was used to evaluate the steady flow flow field. A pressure-based solution and a standard k-ε turbulence model were used. The behavior of the powder material was analyzed using the Dispersed Phase Modeling (DPM) method. Since the volume ratio of the powder material to the gas was less than 10%, the effect of the powder material on the flow field was ignored. Although the Biot number of the polymer particles of the powder material flowing inside the nozzle was 1 or more, the temperature gradient of the particles was not considered, and only the average temperature of the particles was considered.

[0040] In the simulation, 2 million polyhedral elements were used for the cold spray nozzle 12 shown in Figure 1, and 1.7 million polyhedral elements were used for the linear nozzle shown in Figure 2. Five boundary layers were introduced on the inner wall of the nozzle and the substrate, and the elements were divided into independent rectangular prism elements with an increase rate of 1.1. The simulation was performed with residuals of continuity, velocity, k (turbulent kinetic energy), and ε (turbulent dispersion rate) of 10 -3 The energy residual converges to a smaller value than 10 -6 The process was terminated when it converged to a value smaller than .

[0041] In the simulation, the distance between the nozzle 23c of each nozzle and the surface of the substrate was set to 10 mm, and the particle velocity and temperature of the powder material sprayed from the nozzle 23c when it reached the surface of the substrate were calculated.

[0042] [Simulation results: Effect of the spiral diameter D of the spiral portion 23a] Simulations were performed by setting the length L (AP) of one period of the spiral of the spiral portion 23a of the cold spray nozzle 12 shown in Fig. 1 to 60 mm, setting the position of the powder supply port 24 to 2 mm from the downstream end of the spiral portion 23a (position E in Fig. 1), and changing the spiral diameter D (MCD) of the spiral portion 23a. The results of the simulations are shown in Fig. 3. For comparison, Fig. 3 also shows the simulation results of a conventional straight nozzle 51 shown in Fig. 2.

[0043] As shown in Fig. 3(a), it was confirmed that the cold spray nozzle 12 had a slower particle speed at the time of reaching the substrate for all particle diameters compared to the straight nozzle 51. This is believed to be because the cold spray nozzle 12 has a longer flow path length and a larger friction loss compared to the straight nozzle 51. It was also confirmed that the smaller the spiral diameter D, the slower the particle speed.

[0044] It was also confirmed that the particle velocity was maximum when the particle diameter was 23 μm, regardless of the size of the spiral diameter D, and the particle velocity decreased as the particle diameter increased. This is believed to be because the inertia increases with increasing particle diameter, and the acceleration of the particles by the working gas decreases. It was also confirmed that the particle velocity was smaller when the particle diameter was 13 μm than when the particle diameter was 23 μm, regardless of the size of the spiral diameter D. This is believed to be because the particles have smaller inertia, and are affected by the sudden deceleration of the working gas near the substrate.

[0045] As shown in Fig. 3(b), it was confirmed that the particle temperature of the cold spray nozzle 12 decreases as the particle diameter increases, regardless of the size of the spiral diameter D, and decreases by a maximum of 100 K or more. This is believed to be because the volume and surface area of ​​the particles increase with an increase in particle diameter, and it takes time to reach a predetermined temperature. It was also confirmed that when the particle diameter is large, the particle temperature is higher than that of the straight nozzle 51.

[0046] [Simulation results: Effects of the length L of one period of the spiral of the spiral portion 23a] Simulations were performed by setting the spiral diameter D (MCD) of the spiral portion 23a of the cold spray nozzle 12 shown in Fig. 1 to 40 mm, setting the position of the powder supply port 24 to 2 mm from the downstream end of the spiral portion 23a (position E in Fig. 1), and changing the length L (AP) of one period of the spiral of the spiral portion 23a. The results of the simulations are shown in Fig. 4. For comparison, the figure also shows the simulation results of a conventional straight nozzle 51 shown in Fig. 2.

[0047] As shown in Fig. 4(a), it was confirmed that the cold spray nozzle 12, like Fig. 3(a), had a slower particle speed at the time of reaching the substrate for any particle diameter compared to the straight nozzle 51. It was also confirmed that the particle speed became slower as the length L of one period of the spiral became longer.

[0048] In addition, it was confirmed that the particle velocity was maximum when the particle diameter was 23 μm, and the particle velocity decreased as the particle diameter increased, as in Figure 3(a), regardless of the length L of one period of the spiral. It was also confirmed that the particle velocity was smaller when the particle diameter was 13 μm than when the particle diameter was 23 μm, regardless of the length L of one period of the spiral.

[0049] As shown in Figure 4(b), it was confirmed that, in the cold spray nozzle 12, regardless of the length L of one cycle of the spiral, the particle temperature decreases as the particle diameter increases, as in Figure 3(b), and decreases by a maximum of 100 K or more. It was also confirmed that when the particle diameter is large, the particle temperature is higher than that of a linear nozzle. It was also confirmed that the particle temperature is slightly higher when the length L of one cycle of the spiral is longer.

[0050] From the results of Figures 3(a) and 4(a), in order to increase the particle velocity and improve the film formation efficiency, it is better to increase the spiral diameter D of the spiral portion 23a or to decrease the length L of one period of the spiral. Specifically, it is preferable that the length L of one period of the spiral is 40 mm to 60 mm and the spiral diameter D is 40 mm to 60 mm. In particular, it is preferable that the diameter of the powder material made of polymer particles is 20 μm to 45 μm.

[0051] In addition, from the results of Figures 3(b) and 4(b), the diameter D of the spiral of the spiral portion 23a and the length L of one period of the spiral have almost no effect on the particle temperature, and it can be said that in order to increase the particle temperature and improve the film formation efficiency, it is better to make the particle diameter of the powder material smaller. For example, it can be said that the diameter of the powder material made of polymer particles is preferably 10 μm to 45 μm. From the above results, in order to increase the particle speed and improve the film formation efficiency, and to increase the particle temperature and improve the film formation efficiency, it is preferable that the diameter of the powder material made of polymer particles is 20 μm to 45 μm.

[0052] [Simulation results: Effect of the position of the powder supply port 24] Simulations were performed for the cold spray nozzle 12 shown in Fig. 1 with a spiral diameter D (MCD) of 40 mm, a length of one spiral period L (AP) of 40 mm, and the position of the powder supply port 24 changed to 2 mm, 6 mm, and 10 mm from the downstream end of the spiral portion 23a (position E in the figure). The results of the simulation are shown in Fig. 5.

[0053] As shown in Fig. 5(a), when the particle diameter is 33μm or more, the particle velocity is higher when the powder supply port 24 is located at 2mm, which is closer to the spiral portion 23a, than when it is located at 6mm or 10mm, and the particle velocity is also higher at 6mm than when it is located at 10mm. This is believed to be because the path length over which the particles are accelerated by the working gas becomes longer the further upstream the particles are injected into the flow path. It was also confirmed that when the powder supply port 24 is located at 2mm, the particle velocity decreases as the particle diameter increases when the particle diameter is 23μm or more, and when the powder supply port 24 is located at 6mm or 10mm, the particle velocity decreases as the particle diameter increases in all particle diameter ranges.

[0054] As shown in Fig. 5(b), it was confirmed that the particle temperature decreased as the particle diameter increased, regardless of the position of the powder supply port 24, decreasing by a maximum of 100 K or more. In addition, it was confirmed that when the position of the powder supply port 24 was 2 mm, the heating time by the working gas was longer, and therefore the particle temperature was slightly higher than at other positions.

[0055] From the results shown in FIG. 5, it can be said that in order to increase the ejection speed and temperature of the powder material during ejection, it is better to provide powder supply port 24 at a position upstream of direct current portion 23b and closer to spiral portion 23a. [Explanation of symbols]

[0056] 10 Cold spray equipment 11 Gas supply section 11a Gas supply port 12 Cold spray nozzle 21 Gas inlet 22 Nozzle reduction section 23 Nozzle expansion section 23a Spiral part 23b DC section 23c injection port 24 Powder supply port 25 Supply pipe 50 (conventional) cold spray equipment 51 Straight nozzle 52 Enlarged part of nozzle 53 Nozzle 54 Nozzle reduction section 55 Powder supply port

Claims

1. A cold spray nozzle attached to a gas supply unit that supplies a working gas having a temperature lower than the melting point of a powder material, and configured to spray the powder material together with the working gas from a spray port, A flow path for flowing the working gas; a gas inlet port connected to the gas supply unit and capable of introducing the working gas supplied from the gas supply unit into the flow path; a nozzle reduction section in which an inner diameter of the flow passage is smaller than an inner diameter of the gas inlet downstream of the gas inlet; a nozzle expansion section provided downstream of the nozzle contraction section such that an inner diameter of the flow passage gradually increases from the nozzle contraction section toward the downstream side, the nozzle expansion section having the injection port at a tip of the flow passage on the downstream side; a powder supply port provided in the nozzle expansion portion so as to be capable of supplying the powder material to the flow path; The nozzle expansion section has a spiral section in which the flow path is spirally formed from the upstream to the downstream, and the direction of injection of the powder material from the injection port is configured to intersect with a direction parallel to the flow direction of the working gas in the nozzle contraction section. A cold spray nozzle.

2. 2. The cold spray nozzle according to claim 1, wherein the nozzle expansion section is configured so that the direction of ejection of the powder material from the nozzle outlet is perpendicular to a direction parallel to the flow direction of the working gas in the nozzle contraction section.

3. the nozzle expansion section has a direct flow section connected to a downstream side of the helical section so that the flow path smoothly continues from the helical section, The powder supply port is provided in the direct current portion.

3. A nozzle for cold spray according to claim 1 or 2.

4. The gas supply unit is configured to supply the working gas to the gas inlet at a pressure of 0.4 MPa to 0.8 MPa; The helical portion has a length of one period of the helix of 40 mm to 60 mm, a diameter of the helix of 40 mm to 60 mm, and a length along the central axis of the helix of 120 mm to 140 mm. A nozzle for cold spray according to any one of claims 1 to 3.

5. A cold spray device comprising: the cold spray nozzle according to any one of claims 1 to 4; and the gas supply unit.

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