JP7715465B2 - Plasma spraying equipment - Google Patents

Description

This disclosure relates to a plasma spraying device.

Patent Document 1 discloses a plasma spraying device that ejects high-speed gas and powder from a nozzle outlet, melts the ejected powder with plasma heat, and forms a coating of the molten powder on the surface of a substrate.

JP 2018-78054 A

This disclosure provides technology that can prevent powder from adhering to the nozzle, thereby increasing productivity.

According to one aspect of the present disclosure, there is provided a plasma spraying device comprising: a cylindrical nozzle body; a cylindrical first electrode detachably attached to the tip of the nozzle body and having a common axis with the central axis of the nozzle body; and a second electrode attached to the outside of the first electrode and having a common axis with the central axis of the nozzle body; the nozzle body and the first electrode have continuous passages through which gas and powder can flow, and the first electrode has an outlet that communicates with the passage and can eject the gas and powder, the inner diameter of the outlet being larger than the inner diameter of the passage; and the plasma spraying device is configured to generate plasma of the gas between the first electrode and the second electrode, and melt the powder ejected from the outlet with the plasma.

According to one aspect, it is possible to prevent powder from adhering to the nozzle, thereby increasing productivity.

1 is a diagram showing an example of the overall configuration of a plasma spraying apparatus according to an embodiment. FIG. 2 is an enlarged side cross-sectional view showing the electrode structure of FIG. 1 . FIG. 2 is an explanatory diagram showing the periphery of the nozzle in FIG. 1 . FIG. 1 is an explanatory diagram illustrating a nozzle used in an evaluation experiment of plasma spraying. 1 is a graph showing the transition of feeder pressure in an evaluation experiment of plasma spraying. FIG. 6(a) is a vertical cross-sectional view of a jetting cylinder according to a first modified example, and FIG. 6(b) is a vertical cross-sectional view of a jetting cylinder according to a second modified example.

The following describes embodiments of the present disclosure with reference to the drawings. In each drawing, identical components are designated by the same reference numerals, and duplicate descriptions may be omitted.

Figure 1 shows an example of the overall configuration of a plasma spraying device 1 according to an embodiment. As shown in Figure 1, the plasma spraying device 1 is an apparatus that sprays a powder of a thermal spray material (hereinafter referred to as "thermal spray powder R1") onto the surface of a substrate W while melting it with plasma, thereby forming a thermal sprayed film F1 on the surface of the substrate W.

The plasma spraying device 1 includes a spraying section 10 that sprays spray powder R1, a gas supply section 40 that supplies gas to the spraying section 10, a cooling section 60 that cools the spraying section 10, and a control section 70 that controls the operation of each component.

The spraying unit 10 includes a cylindrical nozzle 11 and a feeder 20 that supplies thermal spray powder R1 into the nozzle 11. The tip of the spraying unit 10 is installed within the housing 30 of the plasma spraying device 1.

The particle size of the thermal spray powder R1 ejected from the ejection part 10 is, for example, 1 μm to 10 μm. Examples of the thermal spray powder R1 include fine powders of metals such as copper (Cu), lithium (Li), iron (Fe), aluminum (Al), nickel (Ni), and molybdenum (Mo). The thermal spray powder R1 may also be a fine powder of a resin such as polyester. The thermal spray powder R1 may also be a fine powder of a ceramic such as aluminum oxide, yttrium oxide, yttrium fluoride, zirconium oxide, mullite (Al ₆ O ₁₃ Si ₂ ), or spinel (MgAl ₂ O ₄ ), or a composite material of these ceramics.

The nozzle 11 has a nozzle body 12 that extends linearly and an ejection cylinder 15 that is attached to the tip of the nozzle body 12. The axial length of the ejection cylinder 15 is shorter than the axial length of the nozzle body 12. By constructing the nozzle body 12 and the ejection cylinder 15 as separate components, the nozzle 11 allows for the ejection cylinder 15 to be replaced independently during device maintenance, etc.

The nozzle 11 has an internal passage 11a through which the thermal spray powder flows. The passage 11a is formed in a perfect circle when viewed in a cross section perpendicular to the axial direction of the nozzle 11, and extends from the base end of the nozzle body 12 to the tip of the ejection cylinder 15. In other words, the nozzle body 12 has a main body hole 12a that forms the passage 11a at its axis, while the ejection cylinder 15 has an ejection hole 15a that forms the passage 11a at its axis.

The nozzle body 12 is cylindrical and made of a conductive or non-conductive metal material. The nozzle body 12 has a body hole 12a along its central axis. The body hole 12a extends linearly along the axial direction of the nozzle body 12 with a constant inner diameter. A connection port 12b is formed at the tip of the nozzle body 12 (the end on the ejection cylinder 15 side) and is connected to the body hole 12a and can also be connected to the ejection hole 15a.

The ejection cylinder 15 is made of a conductive metal material and has a cylindrical shape that is slightly thinner than the nozzle body 12. The ejection hole 15a passes linearly through the axis of the ejection cylinder 15. Therefore, the ejection cylinder 15 has an ejection port 15b at its tip that communicates with the ejection hole 15a, and a base end opening 15c (see Figure 2) at its base end that communicates with the ejection hole 15a. The ejection cylinder 15 also has a flange 16 on the outer circumferential surface on the base end side. The flange 16 releasably engages with an inner protrusion 31 provided inside the housing 30.

The housing 30 is made of a non-conductive resin material. The housing 30 secures the ejection cylinder 15 so that the central axis of the nozzle body 12 and the central axis of the ejection cylinder 15 are coaxial. By securing the nozzle 11 to the housing 30, the axis of the passage 11a extends linearly along the vertical direction (up-down direction) of the plasma spraying device 1. Note that the method of securing the ejection cylinder 15 is not limited to engagement between the flange 16 and the inner protrusion 31; it may be secured to the housing 30 or the nozzle body 12 by any suitable engagement means (screw engagement, welding, adhesive, etc.).

When the nozzle 11 is fixed, the housing 30 is in close contact with the outer peripheral surface of the nozzle body 12 from the axial midpoint to the tip end, and is also in close contact with the outer peripheral surface of the base end of the ejection cylinder 15. The housing 30 has a generation space 30a for generating a plasma jet P around the tip end (lower end) of the ejection cylinder 15. Furthermore, the base end (upper end) of the nozzle body 12 protrudes from the top surface of the housing 30.

The feeder 20 is connected to the base end of the nozzle 11 (nozzle body 12) and supplies the thermal spray powder R1 to the nozzle 11. The feeder 20 includes a container 21 that stores the thermal spray powder R1 and an actuator 22 attached to the container 21. The container 21 is formed, for example, in a bowl shape, and feeds the thermal spray powder R1 from the container 21 into the passage 11a when rotational vibration is applied from the actuator 22. The actuator 22 may be a motor and a transmission mechanism that transmits the rotational drive of the motor (both not shown).

The gas supply unit 40 of the plasma spraying apparatus 1 supplies a plasma generating gas as a first gas to the nozzle 11. The plasma generating gas is a gas for generating plasma and also functions as a carrier gas for carrying the thermal spray powder R1 in the passage 11a of the nozzle 11. Examples of the plasma generating gas that can be used include argon (Ar) gas, nitrogen (N ₂ ) gas, helium (He) gas, and mixtures of these gases. The following description will be given taking the example of using Ar gas as the plasma generating gas.

The gas supply unit 40 has a supply pipe 41 for supplying Ar gas (plasma generating gas). The gas supply unit 40 also includes, in order from upstream to downstream in the gas flow direction of the supply pipe 41, a gas supply source 42, a valve 43, and a mass flow controller (MFC) 44. The gas supply unit 40 supplies Ar gas from the gas supply source 42 when the valve 43 is open, and controls the flow rate using the mass flow controller 44, thereby supplying a predetermined flow rate of Ar gas to the passage 11a of the nozzle 11.

Furthermore, the gas supply unit 40 supplies Ar gas, a gas for swirling flow, as the second gas to the generation space 30a of the housing unit 30. The gas supply unit 40 has a branch pipe 45 branching from the supply pipe 41, and the branch pipe 45 is equipped with a mass flow controller (MFC) 46. In other words, when the gas supply unit 40 supplies Ar gas from the gas supply source 42 based on the opening of the valve 43, the mass flow controller 46 controls the flow rate, thereby circulating the Ar gas at a predetermined flow rate through the branch pipe 45.

The branch pipe 45 is connected to a gas flow path 32 provided within the housing 30. The gas flow path 32 extends vertically from the top to the bottom of the housing 30, bending horizontally midway to communicate with the generation space 30a. The Ar gas supplied by the gas supply unit 40 flows horizontally into the generation space 30a, forming a swirling flow around the ejection cylinder 15 within the generation space 30a.

Note that while Figure 1 shows only one supply flow path for Ar gas introduced laterally into the generation space 30a, the housing 30 may be provided with multiple openings communicating with the gas flow path 32 along the circumferential direction of the generation space 30a.

The plasma spraying device 1 has a DC power supply 51 outside the housing 30, and generates plasma within the generation space 30a by supplying DC power to a cathode electrode 52 (first electrode) and an anode electrode 53 (second electrode) installed in the housing 30. The plasma spraying device 1 according to this embodiment uses a nozzle 11 (ejection cylinder 15) made of metal as the cathode electrode 52. The housing 30 also has a metal block 35 on the inner surface of the generation space 30a that functions as the anode electrode 53.

Specifically, the housing 30 has a recess 33 and a protrusion 34 that form the inner circumferential surface of the generation space 30a. The recess 33 is provided with an opening for the gas flow path 32 described above.

The protruding portion 34 is formed by a metal block 35 and protrudes radially inward beyond the recessed portion 33. The metal block 35 is made of a conductive metal material. The metal block 35 is formed in a ring shape, and its outer periphery is joined to the housing portion 30. The area surrounded by the metal block 35 forms a jet passage 35a through which the generated plasma jet P passes. The central axis of the metal block 35 (jet passage 35a), which serves as the second electrode, is coaxial with the central axis of the nozzle body 12 (nozzle 11). In addition, in a cross-sectional view, the metal block 35 is formed in a concave shape with an open outer periphery, allowing a refrigerant such as water to flow through the concave space 35b.

The plasma spraying device 1 having the above configuration supplies DC power from the DC power supply 51 to the nozzle 11 (cathode electrode 52) and the metal block 35 (anode electrode 53). This generates a discharge between the cathode electrode 52 and the anode electrode 53, promoting ionization of the Ar gas and generating plasma in the generation space 30a.

The cooling section 60 includes a chiller unit 61, a refrigerant outlet pipe 62 that discharges the refrigerant from the chiller unit 61, and a refrigerant inlet pipe 63 that returns the refrigerant to the chiller unit 61. The cooling section 60 also includes a valve 64 and a flow meter (FM) 65 on the refrigerant outlet pipe 62, and a valve 66 on the refrigerant inlet pipe 63.

The refrigerant outlet pipe 62 and the refrigerant inlet pipe 63 are connected to a refrigerant flow path 67 formed within the housing 30. The refrigerant flow path 67 is connected to a nozzle cooling space 67a that runs around the outside of the nozzle body 12 and to the recessed space 35b in the metal block 35. The refrigerant supplied from the chiller unit 61 to the refrigerant outlet pipe 62 flows into the refrigerant flow path 67 of the housing 30, passes through the nozzle cooling space 67a and the recessed space 35b within the housing 30, and flows out into the refrigerant inlet pipe 63, returning to the chiller unit 61. This allows the cooling unit 60 to adjust the temperature of the housing 30 during plasma generation.

The plasma spraying device 1 may also be equipped with a magnetic field generating unit (not shown) that generates a magnetic field in the generation space 30a. The magnetic field generating unit may be configured, for example, by placing a ring-shaped permanent magnet or electromagnet at the same height as the metal block 35.

The control unit 70 of the plasma spraying device 1 is a control computer having one or more processors, memory, input/output interfaces, and electronic circuits. The one or more processors are one or a combination of a CPU, ASIC, FPGA, and circuits consisting of multiple discrete semiconductors. The memory includes volatile memory and non-volatile memory (storage media such as computer storage media, flexible disks, compact disks, hard disks, magneto-optical disks, and memory cards), and programs are stored in the non-volatile memory.

The control unit 70 controls each component of the plasma spraying device 1 by having the processor execute the program in the memory, thereby performing plasma spraying and forming a sprayed film F1 on the surface of the substrate W positioned opposite the jet passage 35a at a position away from the housing unit 30. The plasma spraying device 1 may perform spraying while moving the substrate W or while moving the nozzle 11. When performing spraying while moving the substrate W, for example, spraying is performed while moving a stage (not shown) on which the substrate W is placed in the horizontal direction. When performing spraying while moving the nozzle 11, for example, spraying is performed while the housing unit 30 is fixed to an arm that can move horizontally, and the housing unit 30 is moved horizontally by the arm.

The plasma spraying device 1 according to this embodiment has an electrode structure 80 consisting of a nozzle 11 (ejection cylinder 15) serving as a cathode electrode 52 and a metal block 35 serving as an anode electrode 53, which is capable of suppressing adhesion of molten spray powder R1 to the inner wall of the ejection cylinder 15 during plasma spraying. The configuration of this electrode structure 80 will be described below.

Figure 2 is an enlarged side cross-sectional view of the electrode structure 80 of Figure 1. As shown in Figure 2, the ejection cylinder 15, which is one part of the electrode structure 80, has its axial base end fitted into the housing 30, while its axial midpoint to tip is exposed to the generation space 30a.

The axial length L (total length) of the ejection cylinder 15 may be set, for example, in the range of 7 mm to 15 mm, and in this embodiment is set to 10 mm. Furthermore, the axial length of the portion of the ejection cylinder 15 exposed to the generation space 30a (the region from the end face of the housing 30 to the tip of the ejection cylinder 15) may be set, for example, at a ratio of 1/2 to 4/5 of the axial length L of the ejection cylinder 15.

The outer peripheral surface 17 of the ejection cylinder 15 has the flange 16 described above at its base end. The outer peripheral surface 17 also includes a body outer peripheral surface 171 that is closer to the tip (lower side) of the flange 16 and has a smaller outer diameter (diameter) than the flange 16, and a tip outer peripheral surface 172 that is connected to the tip of the body outer peripheral surface 171 and whose outer diameter gradually decreases toward the tip.

The body outer surface 171 extends with a constant outer diameter along the axial direction of the ejection cylinder 15 (linearly and parallel to the axial direction in a cross-sectional view). The outer diameter of the body outer surface 171 depends on the size of the ejection cylinder 15, but may be set, for example, in the range of 4 mm to 8 mm, and is set to 6 mm in this embodiment.

This body outer surface 171 constitutes the majority of the outer surface 17 of the ejection cylinder 15. The axial length of the body outer surface 171 may be set, for example, at a ratio of 2/3 to 9/10 of the axial length L of the ejection cylinder 15.

The tip outer peripheral surface 172 has a tapered shape that reduces in diameter toward the tip, giving the tip of the ejection cylinder 15 a tapered shape. This tip outer peripheral surface 172 makes the outer diameter of the tip of the ejection cylinder 15 smaller than the outer diameter of the body outer peripheral surface 171. For example, the outer diameter of the tip of the ejection cylinder 15 may be set at a ratio of 1/2 to 5/6 of the outer diameter of the body outer peripheral surface 171. The outer diameter of the tip of the ejection cylinder 15 may be in the range of 3 mm to 5 mm, and in this embodiment is set to 4 mm.

The shape (including dimensions) of the tip outer peripheral surface 172 may be appropriately designed based on the smooth flow of the swirling flow of Ar gas formed in the generation space 30a and the stability of the plasma discharge. The outer peripheral surface 17 does not have to have a tapered tip outer peripheral surface 172; for example, it may have a rounded corner between it and the tip of the ejection cylinder 15.

On the other hand, the diameter (inner diameter φia) of the base end opening 15c of the ejection cylinder 15 is set to be the same as the diameter (inner diameter of the main body hole 12a) of the connection communication port 12b of the nozzle main body 12. The ejection cylinder 15 is attached to the housing 30 so that this base end opening 15c and the connection communication port 12b are aligned.

The ejection cylinder 15 has an inner circumferential surface 18 on the inside that constitutes the ejection hole 15a. The inner circumferential surface 18 includes a base-end inner circumferential surface 181 whose inner diameter gradually decreases from the base-end opening 15c toward the tip, a barrel inner circumferential surface 182 (first inner circumferential surface) that is continuous with the base-end inner circumferential surface 181 and has a constant inner diameter in the axial direction, and a tip inner circumferential surface 183 (second inner circumferential surface) that is continuous with the barrel inner circumferential surface 182 and has an inner diameter that gradually increases toward the tip. In other words, the passage 11a provided within the nozzle 11 may be configured so that the inner circumferential surface that constitutes the passage 11a expands or contracts in diameter along the vertical direction. Even in this case, the axis of the passage 11a will still extend linearly.

The base end inner circumferential surface 181 forms the base end opening 15c at the base end. The base end inner circumferential surface 181 has a tapered shape that decreases in diameter toward the tip, gradually narrowing the ejection hole portion 15a. The axial length of the base end inner circumferential surface 181 is longer than the axial length (thickness) of the flange 16.

The barrel inner circumferential surface 182 has a base end that connects to the tip of the base-end inner circumferential surface 181 and extends axially from this base end with a constant inner diameter φib (diameter). The inner diameter φib of the barrel inner circumferential surface 182 is smaller than the inner diameter of the main body bore 12a of the nozzle body 12 (= the inner diameter φia of the base-end opening 15c). The inner diameter φib of the barrel inner circumferential surface 182 forms the smallest diameter portion of the linearly extending passage 11a. In other words, the base-end inner circumferential surface 181 and the barrel inner circumferential surface 182 of the ejection cylinder 15 can increase the flow rate of the thermal spray powder R1 and Ar gas. For example, the inner diameter φib of the barrel inner circumferential surface 182 may be set to a ratio of 2/3 to 9/10 of the inner diameter of the main body bore 12a. The inner diameter φib of the barrel inner circumferential surface 182 may be, for example, in the range of 2 mm to 4 mm, and in this embodiment is 3 mm.

The axial length of the barrel inner circumferential surface 182 is longer than the axial length of the base end inner circumferential surface 181 and the axial length of the tip inner circumferential surface 183. The axial length of the barrel inner circumferential surface 182 may be set, for example, at a ratio of 1/2 to 4/5 of the axial length L of the ejection cylinder 15. The axial position of the base end of the barrel inner circumferential surface 182 and the axial position of the base end of the barrel outer circumferential surface 171 (the boundary with the flange 16) may or may not coincide.

The tip inner circumferential surface 183 has a base end that connects to the tip of the body inner circumferential surface 182 (the end on the ejection port 15b side), and tapers from this base end toward the tip, widening the ejection port 15a. The tip inner circumferential surface 183 forms the ejection port 15b with the edge at the very tip of the ejection cylinder 15 (hereinafter, the edge forming the ejection port 15b is referred to as the ejection port forming edge 183f). In other words, the nozzle 11 has the ejection port 15b at the very tip of the ejection cylinder 15, and the passage 11a (main body hole 12a, ejection port 15a) communicates with this ejection port 15b.

The inner diameter φic of the nozzle-forming edge 183f (spout 15b) is larger than the inner diameter φib of the barrel inner circumferential surface 182, which forms part of the passage 11a. Therefore, the nozzle 11's nozzle 15b is enlarged relative to the barrel inner circumferential surface 182 near and behind the nozzle 15b. This results in a thinner wall near the nozzle-forming edge 183f. For example, the inner diameter ic of the nozzle 15b may be set to 1.1 to 1.5 times the inner diameter φib. Furthermore, the inner diameter φic of the nozzle 15b is set to be equal to or greater than the inner diameter φia of the main body bore 12a of the nozzle body 12. The inner diameter φic of the nozzle 15b may be, for example, in the range of 2.2 mm to 5 mm, and is set to 3.6 mm in this embodiment. As mentioned above, the outer diameter of the tip of the ejection cylinder 15 is 4 mm, so the tip of the ejection cylinder 15 has a ring-shaped end surface with a width of 0.2 mm.

The axial length of the tip inner circumferential surface 183 is not particularly limited and is set, for example, to a ratio of 1/10 to 1/2 of the axial length L of the ejection cylinder 15. In other words, by setting the base end position of the tip inner circumferential surface 183 in the range from the axial middle position of the ejection cylinder 15 to the tip, changes in the flow of Ar gas caused by making the tip inner circumferential surface 183 too long can be suppressed. Furthermore, by setting the base end position of the tip inner circumferential surface 183 away from the ejection port 15b by more than 1/10 of the axial length L of the ejection cylinder 15, a range in which the tip-side wall portion 19a of the ejection cylinder 15 is thin can be ensured. Note that the axial position of the base end of the tip inner circumferential surface 183 and the axial position of the base end of the tip outer circumferential surface 172 do not have to coincide, but may coincide.

The inclination angle θ (taper angle) of the tip inner circumferential surface 183 relative to the extension direction of the body inner circumferential surface 182 depends on the axial length of the tip inner circumferential surface 183 and the inner diameter φic of the nozzle 15b, but is set, for example, in the range of 1° to 45°.

The tip of the ejection cylinder 15 has an ejection port 15b with an inner diameter φic larger than the inner diameter φib, which widens the ejection hole 15a radially outward and suppresses adhesion of the thermal spray powder R1 to the tip inner circumferential surface 183. Furthermore, due to the large inner diameter φic of the ejection port 15b, the thickness of the tip side wall portion 19a of the ejection cylinder 15 between the tip outer circumferential surface 172 and the tip inner circumferential surface 183 is significantly thinner than the thickness of the barrel side wall portion 19b between the barrel outer circumferential surface 171 and the barrel inner circumferential surface 182. This makes it easier for the temperature of the tip of the ejection cylinder 15 to rise due to the heat of the plasma.

The metal block 35, one of the electrode structures 80, has its radially outer peripheral portion fixed to the housing 30, thereby locating the jet passage 35a in the generation space 30a, as described above. The base end of the passage inner surface 36 that constitutes the jet passage 35a of the metal block 35 is formed into a tapered surface 361 that decreases (gradually decreases) in the tip direction (the direction in which the plasma jet P is ejected). The base end of the tapered surface 361 is formed into a rounded corner 362 and is continuous with the base end surface 37 of the metal block 35.

The electrode structure 80 positions the ejection cylinder 15 and the metal block 35 in close proximity to each other, generating a discharge in the gap 80a between them. Specifically, the tip (ejection port 15b) of the ejection cylinder 15 is located further forward than the base end face 37 of the metal block 35, thereby extending into the jet passage 35a inside the metal block 35. In other words, in a cross-sectional view along the axial direction of the electrode structure 80, the ejection port 15b of the cathode electrode 52 and the anode electrode 53 overlap each other. In particular, the entire tip outer peripheral surface 172 and tip inner peripheral surface 183 of the ejection cylinder 15 according to this embodiment are located further forward than the base end face 37 of the metal block 35. This allows for the generation of Ar gas plasma by discharge between the tip of the ejection cylinder 15 and the base end of the metal block 35. In addition, the electrode structure 80 may be configured so that the tip of the ejection cylinder 15 is positioned closer to the base end than the base end surface 37 of the metal block 35 (the cathode electrode 52 may not overlap the anode electrode 53).

The gap 80a between the ejection cylinder 15 and the metal block 35 is the space in which plasma is generated in the electrode structure 80. The distance D of the gap 80a (the minimum distance between the tip outer surface 172 and the passage inner surface 36) depends on the shape of the electrode structure 80, but is preferably set in the range of 1.0 mm to 3.0 mm, for example, and is set to 1.02 mm in this embodiment. If the distance D is less than 1.0 mm, the metal block 35 may be scraped, causing the plasma to become unstable. If the distance D exceeds 3.0 mm, the plasma discharge position may become unstable.

The plasma spraying device 1 according to this embodiment is basically configured as described above, and its effects will be explained below.

Figure 3 is an explanatory diagram showing the periphery of the nozzle 11. As shown in Figure 3, under the control of the control unit 70, the plasma spraying apparatus 1 supplies spray powder R1 to the passage 11a within the nozzle 11 using the feeder 20, while supplying Ar gas (plasma generating gas) using the gas supply unit 40. The plasma spraying apparatus 1 also forms a swirling flow of Ar gas in the generation space 30a by flowing Ar gas from the gas supply unit 40 through the gas flow path 32 into the generation space 30a.

Furthermore, the control unit 70 of the plasma spraying device 1 applies DC power from the DC power supply 51 to the ejection cylinder 15 (cathode electrode 52) and the metal block 35 (anode electrode 53). As a result, plasma is generated in the gap 80a between the ejection cylinder 15 and the metal block 35. At this time, the swirling flow of Ar gas causes the generated plasma to be sprayed vertically toward the substrate W. The control unit 70 supplies refrigerant to the refrigerant flow path 67 of the housing unit 30 via the cooling unit 60. This cools the nozzle body 12 and metal block 35, which have been heated by plasma spraying. Meanwhile, the ejection cylinder 15 is maintained at a high temperature because it is located away from the refrigerant flow path 67.

In the passage 11a of the nozzle 11, the thermal spray powder R1 is carried by the movement of the Ar gas and flows linearly through the nozzle body 12 and the ejection cylinder 15 in that order. At the inner circumferential surface 182 of the body of the ejection cylinder 15, the ejection hole 15a is narrowed, increasing the flow rate of the thermal spray powder R1 and Ar gas. In contrast, at the inner circumferential surface 183 at the tip of the ejection cylinder 15, the ejection hole 15a widens toward the ejection port 15b. This tapered inner circumferential surface 183 at the tip eliminates areas where the thermal spray powder R1 can accumulate (e.g., corners), allowing the thermal spray powder R1 to be ejected stably from the ejection cylinder 15.

As a result, the ejection cylinder 15 can suppress adhesion of the thermal spray powder R1 to the tip inner surface 183, allowing the thermal spray powder R1 to be ejected smoothly. Even if the thermal spray powder R1 adheres to the ejection port forming edge 183f, the ejection port forming edge 183f, which has an enlarged inner diameter of the ejection port 15b, can prevent clogging of the ejection hole portion 15a.

Furthermore, because the tip-side wall portion 19a of the ejection cylinder 15 is thin-walled due to the tip outer peripheral surface 172 and tip inner peripheral surface 183, it is easily heated by the plasma, reaching a high temperature of, for example, approximately 3000°C. This makes it even more difficult for the thermal spray powder R1 to adhere to the tip of the ejection cylinder 15. In particular, because the tip side of the ejection hole portion 15a is widened by the tip inner peripheral surface 183, the flow rate of Ar gas on the passage 11a side decreases, making it easier for the plasma to enter the ejection hole portion 15a. As a result, the temperature of the tip-side wall portion 19a of the ejection cylinder 15 rises even more easily, which has the effect of promoting melting of the thermal spray powder R1.

The thermal spray powder R1 that flows through the ejection cylinder 15 is melted by the heat of the plasma as it is ejected from the ejection port 15b. As a result, the thermal spray powder R1 passes through the jet passage 35a of the metal block 35 as a plasma jet P and is ejected from the tip of the jet passage 35a toward the surface of the substrate W, forming a thermal spray film F1 on the surface of the substrate W. Because the plasma jet P does not contain any clumps of the thermal spray powder R1, the plasma spraying device 1 can form the thermal spray film F1 with high precision.

Figure 4 is an explanatory diagram illustrating an example of a nozzle used in an evaluation experiment of plasma spraying, where (a) shows the case where the ejection cylinder 15 according to this embodiment is applied, and (b) shows the case where the ejection cylinder 90 according to the reference example is applied. As shown in Figure 4(b), the ejection cylinder 90 according to the reference example has a flange 91 and outer peripheral surface 92 that are the same as the flange 16 and outer peripheral surface 17 of the ejection cylinder 15. Therefore, the distance D of the gap 80a between the ejection cylinder 90 and the metal block 35 is the same.

On the other hand, the inner surface 93 of the ejection cylinder 90, which forms the ejection hole portion 90a, has a base end inner surface 931 and a barrel inner surface 932 that are the same diameter as the base end inner surface 181 and barrel inner surface 182 of the ejection cylinder 15, but the barrel inner surface 932 extends to the ejection port 90b. In other words, the inner diameter of the ejection port 90b of the ejection cylinder 90 remains constant from the barrel inner surface 932. Therefore, the tip side wall portion 94a of the ejection cylinder 90 is formed thicker than the tip side wall portion 19a of the ejection cylinder 15.

In the evaluation experiments, the same evaluation machine was used for each of the ejection cylinder 15 and the ejection cylinder 90, and plasma spraying was performed under the same process conditions. The process conditions were: the pressure in the processing vessel housing the plasma spraying apparatus 1 was 20 kPa, the current supplied by the DC power supply 51 was 400 A, and the flow rate of Ar gas from the gas supply unit 40 was 8/18 sLm. The spray powder R1 used in the evaluation experiments was a mixed powder of _yttrium fluoride ( _YF3 ) and yttrium oxide ( _Y2O3 ), and the target supply rate of the spray powder R1 was set to 0.3 g/min. The plasma spraying duration in the evaluation experiments was 60 minutes.

The weight of the ejection cylinder 90 according to the reference example shown in Figure 4(b) increased by 0.0318 g after plasma spraying. In other words, it can be said that the spray powder R1 adhered to the ejection cylinder 90.

In contrast, the weight of the ejection cylinder 15 according to this embodiment shown in Figure 4(a) decreased by 0.0054 g after plasma spraying. In other words, it can be said that almost no thermal spray powder R1 adhered to the ejection cylinder 15. The weight loss of the ejection cylinder 15 is presumed to be due to abrasion of the ejection cylinder 15 by the plasma. The plasma spray deposition rate and supply rate were approximately the same when the ejection cylinder 15 was used and when the ejection cylinder 90 was used. Therefore, it was confirmed that the ejection cylinder 15 according to this embodiment can also perform deposition at the same speed as the ejection cylinder 90 according to the reference example.

Figure 5 is a graph showing the change in feeder pressure during a plasma spraying evaluation experiment, with the horizontal axis representing time and the vertical axis representing feeder pressure. The feeder pressure is the pressure (negative pressure) applied to the feeder 20 from the passage 11a of the nozzle 11. Note that the time ta in the graph of Figure 5 is the timing when the feeder 20 is replenished with thermal spray powder R1.

As shown in Figure 5, the feeder pressure of the ejection cylinder 90 in the reference example (see the two-dot chain line in Figure 5) begins to rise approximately 20 minutes after the start of plasma spraying. In other words, the ejection holes 90a of the ejection cylinder 90 are becoming clogged. Furthermore, the feeder pressure of the ejection cylinder 90 continues to rise especially after 30 minutes have passed, indicating that the ejection holes 90a are becoming increasingly clogged.

In contrast, the feeder pressure of the ejection cylinder 15 according to this embodiment (see the solid line in Figure 5) hardly increases over time. Therefore, it can be seen that the ejection holes 15a of the ejection cylinder 15 do not become clogged even if plasma spraying is continued.

The nozzle 11 (ejection cylinder 15) of the plasma spraying device 1 according to the present disclosure can be modified in various ways. Below, modified examples of the ejection cylinder 15 are described with reference to Figures 6(a) and 6(b).

The inner circumferential surface 18A of the ejection cylinder 15A according to the first modified example shown in FIG. 6(a) has a tip inner circumferential surface 183A that extends radially outward relative to the body inner circumferential surface 182. However, this tip inner circumferential surface 183A has a constant inner diameter φic that extends to the ejection port 15b (non-tapered). In other words, the tip inner circumferential surface 183A is continuous with the body inner circumferential surface 182 via a stepped end surface 184. Even with this configuration having a tip inner circumferential surface 183A, the ejection cylinder 15A can widen the inner diameter φic at the tip of the ejection hole portion 15a, thereby thinning the tip-side wall portion 19a. Therefore, the ejection cylinder 15A can achieve the same effects as the above-described ejection cylinder 15.

The inner circumferential surface 18B of the ejection cylinder 15B according to the second modified example shown in Figure 6(b) has a tip inner circumferential surface 183B that extends radially outward in an arc shape when viewed in cross section along the axial direction. Even with a configuration having such a tip inner circumferential surface 183B, the ejection cylinder 15B can achieve the same effect as the above-described ejection cylinder 15 by making the tip side wall portion 19a thin-walled.

The technical concepts and effects of the present disclosure described in the above embodiments are described below.

One aspect of the present disclosure is a plasma spraying device (1) comprising a cylindrical nozzle body (12), a first electrode (ejection cylinder (15, 15A, 15B) detachably mounted to the tip of the nozzle body (12) and having a common axis with the central axis of the nozzle body (12), and a second electrode (metal block (35)) mounted outside the first electrode and having a common axis with the central axis of the nozzle body (12). The nozzle body (12) and the first electrode have a continuous passage (11a) through which gas and powder can flow, and the first electrode has an ejection port (15b) that communicates with the passage (11a) and can eject the gas and powder. The inner diameter (φic) of the ejection port (15b) is larger than the inner diameter (φib) of the passage (11a). A gas plasma is generated between the first electrode and the second electrode, and the powder ejected from the ejection port (15b) is melted by the plasma.

As described above, in the plasma spraying device 1, the inner diameter φic of the nozzle 15b is larger than the inner diameter φib of the passage 11a, making it difficult for the spray powder R1 to accumulate on the tip inner surface 183, and allowing the spray powder R1 to be stably sprayed from the nozzle 15b. In particular, the large inner diameter φic of the nozzle 15b makes the tip of the first electrode (spraying cylinder 15, 15A, 15B) thin-walled and more easily heated, further suppressing adhesion of the spray powder R1. As a result, the plasma spraying device 1 can reduce the frequency of maintenance and replacement of the first electrode, ultimately increasing productivity.

The first electrode (ejection cylinder 15, 15A, 15B) has a first inner circumferential surface (body inner circumferential surface 182) that extends parallel to the axial direction of the first electrode, and a second inner circumferential surface (tip inner circumferential surface 183) whose inner diameter increases radially outward from the end of the first inner circumferential surface on the ejection port 15b side toward the ejection port 15b. This allows the plasma spraying device 1 to suppress adhesion of the spraying powder R1 to the tip inner circumferential surface 183 while suppressing turbulence in the spraying powder R1 and gas.

The second inner peripheral surface (tip inner peripheral surface 183) also has a tapered shape in which the inner diameter gradually increases radially outward from the end of the first inner peripheral surface (body inner peripheral surface 182) on the nozzle 15b side toward the nozzle 15b. This allows the plasma spraying device 1 to spray the thermal spray powder R1 even more smoothly.

In addition, the inclination angle θ of the second inner circumferential surface (tip inner circumferential surface 183) relative to the first inner circumferential surface (body inner circumferential surface 182) is set in the range of 1° to 45°. This allows the plasma spraying device 1 to ensure a sufficient area for forming the tip inner circumferential surface 183, allowing the plasma to stably heat the tip of the first electrode (nozzle 11).

In addition, the axial length of the second inner peripheral surface (tip inner peripheral surface 183) is less than half the axial length of the first electrode (ejection cylinder 15, 15A, 15B). This allows the plasma spraying device 1 to sufficiently suppress adhesion of the spraying powder R1 to the ejection cylinder 15.

Furthermore, the inner diameter φib of the passage 11a formed by the first inner circumferential surface (body inner circumferential surface 182) is smaller than the inner diameter φia of the inner circumferential surface that constitutes the passage 11a of the nozzle body 12. This allows the plasma spraying device 1 to increase the flow rate of the spray powder R1 and gas at the first inner circumferential surface.

The inner diameter φic of the spray nozzle 15b is set to a range of 1.1 to 2 times the inner diameter φib of the passage 11a formed by the first inner circumferential surface (body inner circumferential surface 182). This ensures that the spray nozzle 15b of the first electrode (spray cylinder 15, 15A, 15B) is sufficiently wide, preventing the spray powder R1 melted by plasma spraying from clogging the spray nozzle 15b.

The first electrode (ejection cylinder 15, 15A, 15B) is a cathode electrode 52, and the second electrode (metal block 35) is an anode electrode 53. This allows the plasma spraying device 1 to generate plasma between the first and second electrodes.

In addition, the first electrode (ejection cylinder 15, 15A, 15B) has an outer peripheral surface (tip outer peripheral surface 172) whose outer diameter decreases radially inward toward the ejection port 15b. This allows the plasma spraying device 1 to make the tip of the first electrode even thinner, accelerating temperature rise.

In addition, the outer peripheral surface (tip outer peripheral surface 172) has a tapered shape in which the outer diameter gradually decreases radially inward toward the nozzle 15b. This allows the plasma generated between the first and second electrodes to move smoothly toward the nozzle 15b of the first electrode.

The second electrode (metal block 35) also has a space (jet passage 35a) through which the powder ejected from the nozzle 15b passes, and the nozzle 15b of the first electrode (nozzle 11) and the second electrode overlap. This allows the plasma spraying device 1 to bring the first and second electrodes closer together, making it possible to appropriately control the position where the plasma is generated.

The plasma spraying apparatus according to the embodiments disclosed herein is illustrative in all respects and not limiting. The embodiments may be modified and improved in various ways without departing from the spirit and scope of the appended claims. The features described in the above multiple embodiments may be configured differently and may be combined within the scope of the accompanying claims.

1 Plasma spraying device 11 Nozzle 11a Passage 12 Nozzle body 15, 15A, 15B Jet cylinder 15b Jet port 172 Tip outer peripheral surface 182 Body inner peripheral surface 183, 183A, 183B Tip inner peripheral surface 19a Tip side wall portion 35 Metal block 35a Jet passage 52 Cathode electrode 53 Anode electrode 80 Electrode structure R1 Spray powder

Claims (8)

A plasma spraying apparatus comprising:
A cylindrical nozzle body;
a cylindrical first electrode detachably provided at the tip of the nozzle body and having an axis common with the central axis of the nozzle body;
a second electrode provided outside the first electrode and having an axis common with a central axis of the nozzle body,
the nozzle body and the first electrode have a continuous passage through which gas and powder can flow, and the first electrode has an ejection port that communicates with the passage and is capable of ejecting the gas and the powder,
an outer diameter of a tip of the first electrode installed at the tip of the nozzle body is smaller than an outer diameter of an outer peripheral surface of a body portion of the first electrode, the outer diameter of the outer peripheral surface extending at a constant outer diameter along the axial direction of the first electrode;
an inner diameter of an ejection port forming edge that forms an ejection port by a distal end edge of the first electrode is larger than an inner diameter of an inner circumferential surface of a body portion that forms at least a part of the passage of the first electrode on a base end side of the ejection port forming edge ,
a plasma of the gas is generated between the first electrode and the second electrode, and the powder injected from the injection port is melted by the plasma ;
the first electrode has a base end inner circumferential surface whose inner diameter gradually decreases from a base end opening toward a tip end, and the barrel inner circumferential surface of the first electrode extends from the base end inner circumferential surface along the axial direction with a constant inner diameter, and has an inner diameter smaller than the inner diameter of an inner circumferential surface of the nozzle body that forms at least a part of the passage;
Plasma spraying equipment. a tip inner circumferential surface extending from a tip of the body inner circumferential surface to the ejection port forming edge has a tapered shape in which an inner diameter gradually increases radially outward toward the ejection port forming edge ;
The plasma spray apparatus of claim 1 . The inclination angle of the tip inner peripheral surface with respect to the extension direction of the trunk inner peripheral surface is set in the range of 1° to 45°.
The plasma spraying apparatus of claim 2 . the axial length of the tip inner circumferential surface is equal to or less than half the axial length of the first electrode;
4. The plasma spraying apparatus according to claim 2 or 3 . The inner diameter of the nozzle forming edge is set in the range of 1.1 to 2 times the inner diameter of the inner peripheral surface of the body portion .
The plasma spraying apparatus according to any one of claims 1 to 4 . the first electrode is a cathode electrode,
the second electrode is an anode electrode;
The plasma spraying apparatus according to any one of claims 1 to 5 . an outer circumferential surface of the first electrode at a tip end thereof relative to the outer circumferential surface of the trunk portion has a tapered shape in which an outer diameter thereof gradually decreases radially inward toward the jet port;
The plasma spraying apparatus according to any one of claims 1 to 6 . the second electrode has a space through which the powder ejected from the ejection port passes,
the nozzle of the first electrode and the second electrode overlap each other in a cross-sectional view along the axial direction of the electrode structure ;
The plasma spraying apparatus according to any one of claims 1 to 7 .