Plasma spraying device

Abstract

To provide a technology capable of enhancing a productivity by suppressing an attachment of a powder to a nozzle.SOLUTION: A plasma spray apparatus includes a nozzle body having a passage for extending gas and a powder in a distributable linear state and a first electrode that is detachably arranged at a tip of the nozzle body, has an ejection nozzle capable of ejecting gas and the powder by communicating with the passage, and a shaft common with a center axis of the nozzle body. The plasma spray apparatus has a second electrode that is arranged outside the first electrode and an axis common with the center axis of the nozzle body. The plasma spray apparatus generates a gas plasma between the first electrode and the second electrode, makes the powder ejected from the ejection nozzle molten by a plasma, and forms a spray coating film by spraying a molten powder to a base material. The inner diameter of the ejection nozzle is larger than the inner diameter of the passage.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a plasma spraying apparatus.

Background Art

[0002] Patent Document 1 discloses a plasma spraying apparatus that ejects high-speed gas and powder from the ejection port of a nozzle, melts the ejected powder by the heat of plasma, and forms a coating of the melted powder on the surface of a substrate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of suppressing powder from adhering to a nozzle and enhancing productivity.

Means for Solving the Problems

[0005] According to one aspect of the present disclosure, there is provided a plasma spraying apparatus including: a cylindrical nozzle body; a cylindrical first electrode detachably provided at the tip of the nozzle body and having an axis common to the central axis of the nozzle body; and a second electrode provided outside the first electrode and having an axis common to the central axis of the nozzle body. The nozzle body and the first electrode have a continuous passage through which gas and powder can flow. The first electrode has an ejection port communicating with the passage and capable of ejecting the gas and the powder. The inner diameter of the ejection port is larger than the inner diameter of the passage. Plasma of the gas is generated between the first electrode and the second electrode, and the powder ejected from the ejection port is configured to be melted by the plasma.

Effects of the Invention

[0006] According to one aspect, it is possible to suppress the adhesion of powder to the nozzle and improve productivity.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0008] Hereinafter, modes for carrying out the present disclosure will be described with reference to the drawings. In each drawing, the same reference numerals are given to the same components, and redundant descriptions may be omitted.

[0009] FIG. 1 is a diagram showing an overall configuration example of a plasma spraying device 1 according to an embodiment. As shown in FIG. 1, the plasma spraying device 1 is a device that ejects powder of a spraying material (hereinafter referred to as "spraying powder R1") toward the surface of a base material W while melting it with plasma, and forms a sprayed film F1 on the surface of the base material W.

[0010] The plasma spraying device 1 includes an ejection unit 10 that ejects the spraying powder R1, a gas supply unit 40 that supplies gas to the ejection unit 10, a cooling unit 60 that cools the ejection unit 10, and a control unit 70 that controls the operation of each component.

[0011] The ejection part 10 includes a cylindrical nozzle 11 and a feeder 20 that supplies the thermal spraying powder R1 into the nozzle 11. Also, the tip side of the ejection part 10 is installed inside the housing part 30 of the plasma spraying device 1.

[0012] The particle size of the thermal spraying powder R1 ejected by the ejection part 10 is, for example, 1 μm to 10 μm. Examples of the thermal spraying powder R1 include fine powders of metals such as copper (Cu), lithium (Li), iron (Fe), aluminum (Al), nickel (Ni), and molybdenum (Mo). Also, the thermal spraying powder R1 may be fine powders of resins such as polyester. Further, the thermal spraying powder R1 may be fine powders of ceramics such as aluminum oxide, yttrium oxide, yttrium fluoride, zirconium oxide, mullite (Al6O 13 Si2), spinel (MgAl2O4), or composite materials of these ceramics.

[0013] The nozzle 11 has a nozzle body 12 extending linearly and an ejection cylinder 15 installed at the tip of the nozzle body 12. The length of the ejection cylinder 15 along the axial direction is shorter than the length of the nozzle body 12 along the axial direction. By making the nozzle body 12 and the ejection cylinder 15 separate members, only the ejection cylinder 15 can be replaced during maintenance of the device and the like.

[0014] The nozzle 11 has a passage 11a inside through which the thermal spraying powder flows. The passage 11a is formed in a perfect circular shape in a cross-sectional view 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. That is, the nozzle body 12 has a main body hole portion 12a that constitutes the passage 11a as its axis, while the ejection cylinder 15 has an ejection hole portion 15a that constitutes the passage 11a as its axis.

[0015] The nozzle body 12 is formed in a cylindrical shape from a metallic material having conductivity or non-conductivity. The nozzle body 12 has a main body hole portion 12a along the central axis. The main body hole portion 12a extends linearly with a constant inner diameter (diameter) along the axial direction of the nozzle body 12. At the tip of the nozzle body 12 (the end on the side of the ejection cylinder 15), a connection communication port 12b is formed which communicates with the main body hole portion 12a and can communicate with the ejection hole portion 15a.

[0016] The ejection cylinder 15 is formed from a metallic material having conductivity and has a slightly thinner cylindrical shape than the nozzle body 12. The ejection hole portion 15a linearly penetrates the axis of the ejection cylinder 15. For this reason, the ejection cylinder 15 has an ejection port 15b that communicates with the ejection hole portion 15a at the tip and a base end opening 15c (see FIG. 2) that communicates with the ejection hole portion 15a at the base end. Further, the ejection cylinder 15 is provided with a flange 16 on the outer peripheral surface on the base end side. The flange 16 detachably engages with an inner convex portion 31 provided in the housing portion 30.

[0017] The housing portion 30 is formed from a non-conductive resin material. The housing portion 30 fixes the ejection cylinder 15 so that the central axis of the nozzle body 12 and the central axis of the ejection cylinder 15 have a common axis. By fixing the nozzle 11 to the housing portion 30, the axis of the passage 11a is in a state of linearly extending along the vertical direction (up and down direction) of the plasma spraying apparatus 1. Note that the fixing of the ejection cylinder 15 is not limited to the engagement between the flange 16 and the inner convex portion 31, and may be fixed to the housing portion 30 or the nozzle body 12 by appropriate engagement means (screwing, welding, adhesion, etc.).

[0018] The housing portion 30 is in close contact with the outer peripheral surface from the axial middle position to the tip side of the nozzle body 12 and is also in close contact with the outer peripheral surface on the base end side of the ejection cylinder 15 in a state where the nozzle 11 is fixed. The housing portion 30 has a generation space 30a for generating the plasma jet P around the tip side (lower end side) of the ejection cylinder 15. Further, the base end side (upper end side) of the nozzle body 12 protrudes from the upper surface of the housing portion 30.

[0019] The feeder 20 is connected to the proximal end of the nozzle 11 (nozzle body 12) and supplies the spraying powder R1 to the nozzle 11. The feeder 20 includes a container 21 for accommodating the spraying powder R1 and an actuator 22 provided on the container 21. The container 21 is formed, for example, in a bowl shape, and the spraying powder R1 is introduced from the container 21 into the passage 11a when rotational vibration is applied from the actuator 22. As the actuator 22, a motor and a transmission mechanism for transmitting the rotational drive of the motor are applied (both not shown).

[0020] The gas supply unit 40 of the plasma spraying device 1 supplies a plasma generation gas as the first gas to the nozzle 11. The plasma generation gas is a gas for generating plasma and also functions as a carrier gas for transporting the spraying powder R1 in the passage 11a of the nozzle 11. As the plasma generation gas, for example, argon (Ar) gas, nitrogen (N2) gas, helium (He) gas, or a mixed gas thereof can be used. Hereinafter, the case of using Ar gas as the plasma generation gas will be described as an example.

[0021] The gas supply unit 40 has a supply pipe 41 for supplying Ar gas (plasma generation gas). Further, the gas supply unit 40 includes a gas supply source 42, a valve 43, and a mass flow controller (MFC) 44 in order from the upstream to the downstream in the gas flow direction of the supply pipe 41. The gas supply unit 40 supplies Ar gas from the gas supply source 42 based on the opening of the valve 43 and controls the flow rate by the mass flow controller 44 to supply Ar gas at a predetermined flow rate to the passage 11a of the nozzle 11.

[0022] Furthermore, the gas supply unit 40 supplies Ar gas, which is a swirling flow gas as the second gas, to the generation space 30a of the housing unit 30. The gas supply unit 40 has a branch pipe 45 branched from the supply pipe 41 and includes a mass flow controller (MFC) 46 in the branch pipe 45. That is, 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 to circulate Ar gas at a predetermined flow rate through the branch pipe 45.

[0023] The branch pipe 45 is connected to the gas flow path 32 provided in the housing portion 30. The gas flow path 32 extends vertically from the upper part to the lower part of the housing portion 30 and bends horizontally at an intermediate position to communicate with the generation space 30a. The Ar gas supplied by the gas supply unit 40 flows out into the generation space 30a from the horizontal direction, thereby forming a swirling flow around the ejection cylinder 15 in the generation space 30a.

[0024] In FIG. 1, only one supply flow path of the Ar gas introduced into the generation space 30a from the horizontal direction is shown, but a plurality of openings communicating with the gas flow path 32 may be provided along the circumferential direction of the generation space 30a in the housing portion 30.

[0025] The plasma spraying device 1 has a DC power source 51 outside the housing portion 30 and supplies DC power to the cathode electrode 52 (first electrode) and the anode electrode 53 (second electrode) installed in the housing portion 30, thereby generating plasma in the generation space 30a. In the plasma spraying device 1 according to the present embodiment, as the cathode electrode 52, a nozzle 11 (ejection cylinder 15) formed of metal is applied. Further, the housing portion 30 has a metal block 35 that functions as the anode electrode 53 on the inner peripheral surface of the generation space 30a.

[0026] Specifically, the housing portion 30 has a recessed portion 33 and a protruding portion 34 as portions constituting the inner peripheral surface of the generation space 30a. The opening of the gas flow path 32 described above is provided in the recessed portion 33.

[0027] The protruding portion 34 is formed by a metal block 35 and protrudes radially inward from the recessed portion 33. The metal block 35 is formed of a metal material having conductivity. The metal block 35 is formed in a ring shape, and its outer peripheral side is joined to the housing portion 30. The portion surrounded by the metal block 35 serves as a jet passage 35a through which the generated plasma jet P passes. The central axis of the metal block 35 (jet passage 35a), which is the second electrode, has an axis common to the central axis of the nozzle body 12 (nozzle 11). Further, the metal block 35 is formed in a concave shape with an open outer peripheral side in a cross-sectional view, and it is possible to allow a refrigerant such as water to flow through the concave space 35b.

[0028] The plasma spraying apparatus 1 having the above configuration supplies DC power from a DC power source 51 to the nozzle 11 (cathode electrode 52) and the metal block 35 (anode electrode 53). Thereby, a discharge occurs between the cathode electrode 52 and the anode electrode 53 to promote the ionization of the Ar gas, and plasma can be generated in the generation space 30a.

[0029] The cooling unit 60 includes a chiller unit 61, a refrigerant outflow pipe 62 for discharging the refrigerant from the chiller unit 61, and a refrigerant inflow pipe 63 for returning the refrigerant to the chiller unit 61. Further, the cooling unit 60 is provided with a valve 64 and a flow meter (FM) 65 in the refrigerant outflow pipe 62, and a valve 66 in the refrigerant inflow pipe 63.

[0030] The refrigerant outflow pipe 62 and the refrigerant inflow pipe 63 are connected to a refrigerant flow path 67 formed in the housing portion 30. The refrigerant flow path 67 communicates with a nozzle cooling space 67a that circulates outside the nozzle body 12 and the concave space 35b of the metal block 35. The refrigerant supplied from the chiller unit 61 to the refrigerant outflow pipe 62 flows into the refrigerant flow path 67 of the housing portion 30, passes through the nozzle cooling space 67a and the concave space 35b in the housing portion 30, and flows out to the refrigerant inflow pipe 63, thereby returning to the chiller unit 61. Thereby, the cooling unit 60 can adjust the temperature of the housing portion 30 during plasma generation.

[0031] Further, the plasma spraying device 1 may include a magnetic field generating unit (not shown) that generates a magnetic field in the generation space 30a. The magnetic field generating unit can be configured, for example, by arranging a ring-shaped permanent magnet or an electromagnet at the same height position as the metal block 35.

[0032] The control unit 70 of the plasma spraying device 1 is a control computer having one or more processors, a memory, an input / output interface, and an electronic circuit. The one or more processors are a combination of one or more of a CPU, an ASIC, an FPGA, a circuit composed of a plurality of discrete semiconductors, etc. The memory includes a volatile memory and a non-volatile memory (a storage medium such as a computer storage medium, a flexible disk, a compact disk, a hard disk, a magneto-optical disk, a memory card), and stores a program in the non-volatile memory.

[0033] The control unit 70 controls each component of the plasma spraying device 1 by the processor executing the program in the memory to perform plasma spraying, and forms a sprayed film F1 on the surface of the base material W disposed opposite to the jet passage 35a at a position separated from the housing portion 30. Note that the plasma spraying device 1 may perform spraying while moving the base material W, or may perform spraying while moving the nozzle 11. When performing spraying while moving the base material W, for example, spraying is performed while moving a stage (not shown) on which the base material W is placed in the horizontal direction. When performing spraying while moving the nozzle 11, for example, the housing portion 30 is fixed to an arm movable in the horizontal direction, and spraying is performed while moving the housing portion 30 in the horizontal direction by the arm.

[0034] And the plasma spraying device 1 according to the present embodiment can suppress the adhesion of the molten spraying powder R1 to the inner wall of the ejection cylinder 15 of the electrode structure 80 composed of the nozzle 11 (ejection cylinder 15) as the cathode electrode 52 and the metal block 35 as the anode electrode 53 during plasma spraying. Hereinafter, the configuration of this electrode structure 80 will be described.

[0035] FIG. 2 is a side cross-sectional view showing an enlarged view of the electrode structure 80 of FIG. 1. As shown in FIG. 2, the ejection cylinder 15, which is one of the electrode structures 80, has its axially proximal end fitted into the housing portion 30 while its tip from the axial middle is exposed to the generation space 30a.

[0036] The dimension of the axial length L (total length) of the ejection cylinder 15 is preferably set in the range of, for example, 7 mm to 15 mm, and is 10 mm in this embodiment. Further, 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 portion 30 to the tip of the ejection cylinder 15) is preferably set at a ratio of, for example, 1 / 2 to 4 / 5 with respect to the axial length L of the ejection cylinder 15.

[0037] The outer peripheral surface 17 of the ejection cylinder 15 has the above-described flange 16 at the proximal end. Further, the outer peripheral surface 17 includes a body outer peripheral surface 171 having an outer diameter (diameter) smaller than that of the flange 16 on the tip side (lower side) than the flange 16, and a tip outer peripheral surface 172 that is continuous with the tip of the body outer peripheral surface 171 and has a gradually decreasing outer diameter toward the tip direction.

[0038] The body outer peripheral surface 171 extends with a constant outer diameter (in a direction parallel and linear to the axial direction in a cross-sectional view) along the axial direction of the ejection cylinder 15. The dimension of the outer diameter of the body outer peripheral surface 171 depends on the size of the ejection cylinder 15, but is preferably set in the range of, for example, 4 mm to 8 mm, and is 6 mm in this embodiment.

[0039] This body outer peripheral surface 171 constitutes most of the outer peripheral surface 17 of the ejection cylinder 15. The axial length of the body outer peripheral surface 171 is preferably set at a ratio of, for example, 2 / 3 to 9 / 10 with respect to the axial length L of the ejection cylinder 15.

[0040] The tip outer peripheral surface 172 has a tapered shape that becomes smaller in diameter toward the tip direction, making the tip of the ejection cylinder 15 tapered. Due to this tip outer peripheral surface 172, the outer diameter of the tip of the ejection cylinder 15 is 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 to a ratio of 1 / 2 to 5 / 6 with respect to the outer diameter of the body outer peripheral surface 171. The dimension of the outer diameter of the tip of the ejection cylinder 15 is preferably in the range of 3 mm to 5 mm, and is 4 mm in this embodiment.

[0041] Note that 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 plasma discharge. The outer peripheral surface 17 does not necessarily have the tapered tip outer peripheral surface 172. For example, it may have a configuration with a rounded corner between the tip of the ejection cylinder 15.

[0042] 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 portion 12a) of the connection communication port 12b of the nozzle main body 12. The ejection cylinder 15 is attached to the housing portion 30 such that the base end opening 15c and the connection communication port 12b coincide.

[0043] The ejection cylinder 15 has, on the inside, an inner peripheral surface 18 that constitutes the ejection hole portion 15a. The inner peripheral surface 18 includes a base end inner peripheral surface 181 whose inner diameter gradually decreases from the base end opening 15c toward the tip direction, a body inner peripheral surface 182 (first inner peripheral surface) that is continuous with the base end inner peripheral surface 181 and has a constant inner diameter in the axial direction, and a tip inner peripheral surface 183 (second inner peripheral surface) that is continuous with the body inner peripheral surface 182 and whose inner diameter increases (gradually increases) toward the tip direction. That is, the passage 11a provided in the nozzle 11 may be configured such that the inner peripheral surface constituting the passage 11a expands or contracts along the vertical direction. Even in this case, the axis of the passage 11a extends linearly.

[0044] The proximal end inner peripheral surface 181 forms a proximal end opening 15c at the proximal end. The proximal end inner peripheral surface 181 has a tapered shape that becomes smaller in diameter toward the distal end, thereby gradually narrowing the ejection hole portion 15a. The axial length of the proximal end inner peripheral surface 181 is longer than the axial length (thickness) of the flange 16.

[0045] The barrel inner peripheral surface 182 has a proximal end that is continuous with the distal end of the proximal end inner peripheral surface 181 and extends axially along a constant inner diameter φib (diameter) from this proximal end. The inner diameter φib of this barrel inner peripheral surface 182 is smaller than the inner diameter of the main body hole portion 12a of the nozzle main body 12 (= the inner diameter φia of the proximal end opening 15c). The inner diameter φib of this barrel inner peripheral surface 182 forms a portion with the minimum diameter in the linearly extending passage 11a. That is, the ejection cylinder 15 can increase the flow rates of the thermal spraying powder R1 and the Ar gas by the proximal end inner peripheral surface 181 and the barrel inner peripheral surface 182. For example, the inner diameter φib of the barrel inner peripheral surface 182 is preferably set at a ratio of 2 / 3 to 9 / 10 of the inner diameter of the main body hole portion 12a. As the dimension of the inner diameter φib of the barrel inner peripheral surface 182, for example, it is preferably in the range of 2 mm to 4 mm, and in this embodiment, it is 3 mm.

[0046] The axial length of the barrel inner peripheral surface 182 is longer than the axial length of the proximal end inner peripheral surface 181 and the axial length of the distal end inner peripheral surface 183. The axial length of the barrel inner peripheral surface 182 is preferably set at a ratio of 1 / 2 to 4 / 5 with respect to the axial length L of the ejection cylinder 15, for example. The axial position of the proximal end of the barrel inner peripheral surface 182 and the axial position of the proximal end of the barrel outer peripheral surface 171 (the boundary with the flange 16) do not have to coincide, and may coincide.

[0047] The tip inner peripheral surface 183 has a base end connected to the tip of the body inner peripheral surface 182 (the end on the side of the ejection port 15b), and exhibits a tapered shape that becomes larger in diameter from this base end toward the tip end, thereby widening the ejection hole portion 15a. And the tip inner peripheral surface 183 forms the ejection port 15b by the edge of the foremost end of the ejection cylinder 15 (hereinafter, the edge forming the ejection port 15b is referred to as the ejection port forming edge 183f). That is, the nozzle 11 has the ejection port 15b at the foremost end of the ejection cylinder 15, and the passage 11a (the main body hole portion 12a, the ejection hole portion 15a) communicates with this ejection port 15b.

[0048] The inner diameter φic of the ejection port forming edge 183f (the ejection port 15b) is larger than the inner diameter φib of the body inner peripheral surface 182 that constitutes a part of the passage 11a. Therefore, the ejection port 15b of the nozzle 11 expands with respect to the body inner peripheral surface 182 on the back side and in the vicinity of the ejection port 15b. As a result, the wall thickness in the vicinity of the ejection port forming edge 183f becomes thinner. For example, the inner diameter ic of the ejection port 15b may be set to 1.1 to 1.5 times the inner diameter φib. Further, the inner diameter φic of the ejection port 15b is set to be equal to or greater than the inner diameter φia of the main body hole portion 12a of the nozzle main body 12. The dimension of the inner diameter φic of the ejection port 15b is, for example, preferably in the range of 2.2 mm to 5 mm, and is 3.6 mm in this embodiment. As described above, since the outer diameter of the tip of the ejection cylinder 15 is 4 mm, the tip of the ejection cylinder 15 comes to have a ring-shaped end face with a width of 0.2 mm.

[0049] The axial length of the tip inner peripheral surface 183 is not particularly limited, and is, for example, set to a ratio of 1 / 10 to 1 / 2 with respect to the axial length L of the ejection cylinder 15. That is, by setting the base end position of the tip inner peripheral surface 183 to be in the range from the axial intermediate position of the ejection cylinder 15 to the tip end, it is possible to suppress a change in the flow of the Ar gas due to making the tip inner peripheral surface 183 too long. Further, by setting the base end position of the tip inner peripheral surface 183 to be more than 1 / 10 of the axial length L of the ejection cylinder 15 away from the ejection port 15b, it is possible to secure a range in which the tip-side meat portion 19a of the ejection cylinder 15 becomes thin. Note that the axial position of the base end of the tip inner peripheral surface 183 and the axial position of the base end of the tip outer peripheral surface 172 do not have to coincide, and may coincide.

[0050] The inclination angle θ (taper angle) of the tip inner peripheral surface 183 with respect to the extending direction of the inner peripheral surface 182 of the barrel is set in the range of, for example, 1° to 45°, although it depends on the axial length of the tip inner peripheral surface 183 and the inner diameter φic of the ejection port 15b.

[0051] The tip of the ejection cylinder 15 has an ejection port 15b with an inner diameter φic larger than the inner diameter φib, thereby expanding the ejection hole 15a radially outward and suppressing the adhesion of the thermal spraying powder R1 to the tip inner peripheral surface 183. Further, due to the ejection port 15b with a large inner diameter φic, the wall thickness of the tip side wall portion 19a of the ejection cylinder 15 between the tip outer peripheral surface 172 and the tip inner peripheral surface 183 becomes significantly thinner than the wall thickness of the barrel side wall thickness 19b between the barrel outer peripheral surface 171 and the barrel inner peripheral surface 182. For this reason, the tip of the ejection cylinder 15 is likely to have its temperature increased by the heat of the plasma.

[0052] Also, one of the electrode structures 80, the metal block 35, has its outer peripheral portion on the radially outer side fixed to the housing portion 30, and thus, as described above, the jet passage 35a is disposed in the generation space 30a. The proximal end side of the passage inner peripheral surface 36 constituting the jet passage 35a of the metal block 35 is formed as a tapered surface 361 that decreases (gradually decreases) along the tip direction (the ejection direction of the plasma jet P). Further, the proximal end of the tapered surface 361 is formed as a rounded corner 362 and is continuous with the proximal end surface 37 of the metal block 35.

[0053] The electrode structure 80 causes a discharge in the gap 80a therebetween by arranging the ejection cylinder 15 and the metal block 35 in proximity to each other. Specifically, the tip (ejection port 15b) of the ejection cylinder 15 is positioned ahead of the base end surface 37 of the metal block 35, thereby entering 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 (overlap each other). In particular, for the ejection cylinder 15 according to the present embodiment, the entire outer peripheral surface 172 and inner peripheral surface 183 of the tip are positioned ahead of the base end surface 37 of the metal block 35. Thereby, plasma of Ar gas can be generated by the discharge between the tip of the ejection cylinder 15 and the base end of the metal block 35. Note that the electrode structure 80 may arrange the tip of the ejection cylinder 15 on the base end side of the base end surface 37 of the metal block 35 (a structure in which the cathode electrode 52 does not overlap the anode electrode 53 may also be used).

[0054] The gap 80a between the ejection cylinder 15 and the metal block 35 becomes a space for generating plasma in the electrode structure 80. The interval D of the gap 80a (the minimum distance between the outer peripheral surface 172 of the tip and the inner peripheral surface 36 of the passage) depends on the shape of the electrode structure 80, but for example, it is preferably set in the range of 1.0 mm to 3.0 mm. In the present embodiment, it is 1.02 mm. If the interval D is less than 1.0 mm, the metal block 35 may be worn away and the plasma may become unstable. If the interval D exceeds 3.0 mm, the discharge position of the plasma may become unstable.

[0055] The plasma spraying apparatus 1 according to the present embodiment is basically configured as described above, and its operation and effects will be described below.

[0056] FIG. 3 is an explanatory diagram showing the periphery of the nozzle 11. As shown in FIG. 3, under the control of the control unit 70, the plasma spraying apparatus 1 supplies the spraying powder R1 to the passage 11a in the nozzle 11 by the feeder 20 while supplying Ar gas (plasma generating gas) by the gas supply unit 40. Further, the plasma spraying apparatus 1 forms a swirling flow of Ar gas in the generation space 30a by allowing the Ar gas to flow out from the gas supply unit 40 into the generation space 30a through the gas flow path 32.

[0057] Furthermore, the control unit 70 of the plasma spraying apparatus 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, by the swirling flow of the Ar gas flowing, the generated plasma can be ejected in the vertical direction toward the base material W. The control unit 70 supplies a refrigerant to the refrigerant flow path 67 of the housing part 30 by the cooling unit 60. Thereby, the nozzle body 12 and the metal block 35 heated by plasma spraying are cooled. On the other hand, since the ejection cylinder 15 is located at a position away from the refrigerant flow path 67, a high temperature state is maintained.

[0058] In the passage 11a of the nozzle 11, the spraying powder R1 is carried by the movement of the Ar gas and flows linearly in the order of the nozzle body 12 and the ejection cylinder 15. In the inner peripheral surface 182 of the body of the ejection cylinder 15, the ejection hole 15a is narrowed, so that the flow rates of the spraying powder R1 and the Ar gas increase. On the other hand, in the tip inner peripheral surface 183 of the ejection cylinder 15, the ejection hole 15a expands toward the ejection port 15b. This tapered tip inner peripheral surface 183 eliminates the place where the spraying powder R1 stays (for example, the corner part), and can stably eject the spraying powder R1 from the ejection cylinder 15.

[0059] Therefore, the ejection cylinder 15 can suppress the adhesion of the spraying powder R1 to the inner peripheral surface 183 of the tip and smoothly eject the spraying powder R1. Even if the spraying powder R1 adheres to the edge 183f of the ejection port formation, the edge 183f with the widened inner diameter of the ejection port 15b can avoid the blockage of the ejection hole 15a.

[0060] In addition, the tip-side wall portion 19a of the ejection cylinder 15 is thinned by the tip outer peripheral surface 172 and the tip inner peripheral surface 183, so that it can be easily heated by the plasma and reach a high temperature of about 3000 °C, for example. As a result, it becomes more difficult for the spraying powder R1 to adhere to the tip of the ejection cylinder 15. In particular, since the tip-side of the ejection hole 15a is widened by the tip inner peripheral surface 183, the flow rate of the Ar gas on the passage 11a side decreases, and the plasma easily enters the ejection hole 15a. Therefore, the temperature of the tip-side wall portion 19a of the ejection cylinder 15 rises more easily, and the effect of promoting the melting of the spraying powder R1 is obtained.

[0061] The spraying powder R1 flowing through the ejection cylinder 15 is melted by the heat of the plasma while being ejected from the ejection port 15b. As a result, the spraying powder R1 passes through the jet passage 35a of the metal block 35 as the plasma jet P and is ejected from the tip of the jet passage 35a toward the surface of the base material W, thereby forming the sprayed film F1 on the surface of the base material W. Since there are no lumps associated with the adhesion of the spraying powder R1 in the plasma jet P, the plasma spraying apparatus 1 can accurately form the sprayed film F1.

[0062] FIG. 4 is an explanatory diagram illustrating a nozzle when an evaluation experiment of plasma spraying is performed. (a) shows the case where the ejection cylinder 15 according to the present embodiment is applied, and (b) shows the case where the ejection cylinder 90 according to the reference example is applied. The ejection cylinder 90 according to the reference example has the same flange 91 and outer peripheral surface 92 as the flange 16 and outer peripheral surface 17 of the ejection cylinder 15, as shown in FIG. 4(b). Therefore, the interval D of the gap 80a between the ejection cylinder 90 and the metal block 35 is the same.

[0063] On the other hand, the inner peripheral surface 93 of the ejection cylinder 90 forming the ejection hole 90a has a base-end inner peripheral surface 931 and a barrel inner peripheral surface 932 with the same diameter as the base-end inner peripheral surface 181 and the barrel inner peripheral surface 182 of the ejection cylinder 15, but the barrel inner peripheral surface 932 extends to the ejection port 90b. In other words, in the ejection cylinder 90, the inner diameter of the ejection port 90b remains constant from the barrel inner peripheral 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.

[0064] In the evaluation experiment, for each of the ejection cylinder 15 and the ejection cylinder 90, the same evaluation machine is used and plasma spraying is performed under the same process conditions. In the process conditions, the pressure inside the processing container housing the plasma spraying device 1 is set to 20 [kPa], the current supplied by the DC power supply 51 is set to 400 [A], and the flow rate of the Ar gas by the gas supply unit 40 is set to 8 / 18 [sLm]. Also, as the spraying powder R1 used in the evaluation experiment, a mixed powder of yttrium fluoride (YF3) and yttrium oxide (Y2O3) is applied, and the target supply amount of the spraying powder R1 is set to 0.3 [g / min]. The implementation period of the plasma spraying in the evaluation experiment is 60 minutes.

[0065] Regarding the ejection cylinder 90 according to the reference example shown in FIG. 4(b), after the plasma spraying, the weight of the ejection cylinder 90 increased by 0.0318 g. That is, it can be said that the spraying powder R1 adhered to the ejection cylinder 90.

[0066] On the contrary, regarding the ejection cylinder 15 according to the present embodiment shown in FIG. 4(a), after the plasma spraying, the weight of the ejection cylinder 15 decreased by 0.0054 g. That is, it can be said that almost no spraying powder R1 adhered to the ejection cylinder 15. The decrease in weight occurring in the ejection cylinder 15 is presumed to be due to the erosion of the ejection cylinder 15 by the plasma. Note that the film formation rate and the supply rate of the plasma spraying were substantially the same results when the ejection cylinder 15 was applied and when the ejection cylinder 90 was applied. Therefore, it was confirmed that the ejection cylinder 15 according to the present embodiment can also perform film formation at the same speed as the ejection cylinder 90 according to the reference example.

[0067] FIG. 5 is a graph showing the change in the feeder pressure in the evaluation experiment of plasma spraying, where the horizontal axis represents time and the vertical axis represents the 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 point ta in the graph of FIG. 5 is the timing when the spraying powder R1 is replenished to the feeder 20.

[0068] As shown in FIG. 5, the feeder pressure of the ejection cylinder body 90 according to the reference example (see the two-dot chain line in FIG. 5) has been increasing since about 20 minutes after the start of plasma spraying. That is, the ejection hole 90a of the ejection cylinder body 90 is blocked. Also, the feeder pressure of the ejection cylinder body 90 continues to increase particularly after 30 minutes have passed, indicating that the blockage of the ejection hole 90a is progressing.

[0069] On the other hand, the feeder pressure of the ejection cylinder body 15 according to the present embodiment (see the solid line in FIG. 5) hardly increases even as time passes. Therefore, it can be seen that the ejection hole 15a of the ejection cylinder body 15 does not become blocked even if plasma spraying is continued.

[0070] Note that the nozzle 11 (ejection cylinder body 15) of the plasma spraying device 1 according to the present disclosure can take various modified forms. Hereinafter, with reference to FIGS. 6(a) and 6(b), modified forms of the ejection cylinder body 15 will be described.

[0071] The inner peripheral surface 18A of the ejection cylinder body 15A according to the first modified form shown in FIG. 6(a) has a tip inner peripheral surface 183A that extends radially outward with respect to the body inner peripheral surface 182, and this tip inner peripheral surface 183A has a (non-tapered) shape that extends to the ejection port 15b with a constant inner diameter φic. That is, the tip inner peripheral surface 183A is continuous with the body inner peripheral surface 182 via a stepped end surface 184. Even with such a configuration having the tip inner peripheral surface 183A, the ejection cylinder body 15A can widen the inner diameter φic at the tip of the ejection hole 15a and make the tip-side wall portion 19a thin. Therefore, the ejection cylinder body 15A can obtain the same effects as the above-described ejection cylinder body 15.

[0072] In the second modification shown in FIG. 6(b), the inner peripheral surface 18B of the ejection cylinder 15B has a tip inner peripheral surface 183B that expands in an arc shape radially outward in a cross-sectional view along the axial direction. Even with such a configuration having the tip inner peripheral surface 183B, the ejection cylinder 15B can have a thin tip-side wall portion 19a and obtain the same effects as the above-described ejection cylinder 15.

[0073] The technical idea and effects of the present disclosure described in the above embodiments will be described below.

[0074] One aspect of the present disclosure is a plasma spraying apparatus 1, which includes a cylindrical nozzle body 12, a first electrode (ejection cylinders 15, 15A, 15B) that is detachably provided at the tip of the nozzle body 12 and has an axis common with the central axis of the nozzle body 12, and a second electrode (metal block 35) that is provided outside the first electrode and has an axis common 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. The first electrode has an ejection port 15b that communicates with the passage 11a and can eject gas and powder. The inner diameter φic of the ejection port 15b is larger than the inner diameter φib of the passage 11a. A plasma of gas is generated between the first electrode and the second electrode, and the powder ejected from the ejection port 15b is configured to be melted by the plasma.

[0075] According to the above, in the plasma spraying apparatus 1, since the inner diameter φic of the ejection port 15b is larger than the inner diameter φib of the passage 11a, it becomes difficult for the spraying powder R1 to accumulate on the tip inner peripheral surface 183, and the spraying powder R1 can be stably ejected from the ejection port 15b. In particular, since the inner diameter φic of the ejection port 15b is large, the tip of the first electrode (ejection cylinders 15, 15A, 15B) becomes thin and is likely to heat up, so that the adhesion of the spraying powder R1 can be further suppressed. As a result, the plasma spraying apparatus 1 can reduce the frequency of maintenance and replacement of the first electrode, and as a result, can improve productivity.

[0076] Further, the first electrode (the ejection cylinders 15, 15A, 15B) has a first inner peripheral surface (the inner peripheral surface 182 of the cylinder part) extending parallel to the axial direction of the first electrode, and a second inner peripheral surface (the inner peripheral surface 183 of the tip) whose inner diameter increases radially outward from the end on the ejection port 15b side of the first inner peripheral surface toward the ejection port 15b. Thereby, the plasma spraying apparatus 1 can suppress the adhesion of the spraying powder R1 to the tip inner peripheral surface 183 while suppressing the generation of turbulent flow in the spraying powder R1 and the gas.

[0077] Further, the second inner peripheral surface (the inner peripheral surface 183 of the tip) has a tapered shape in which the inner diameter increases gradually radially outward from the end on the ejection port 15b side of the first inner peripheral surface (the inner peripheral surface 182 of the cylinder part) toward the ejection port 15b. Thereby, the plasma spraying apparatus 1 can spray the spraying powder R1 more smoothly.

[0078] Further, the inclination angle θ of the second inner peripheral surface (the inner peripheral surface 183 of the tip) with respect to the first inner peripheral surface (the inner peripheral surface 182 of the cylinder part) is set in the range of 1° to 45°. Thereby, the plasma spraying apparatus 1 can sufficiently secure the formation range of the tip inner peripheral surface 183 and stably raise the temperature of the tip of the first electrode (the nozzle 11) by plasma.

[0079] Further, the axial length of the second inner peripheral surface (the inner peripheral surface 183 of the tip) is 1 / 2 or less of the axial length of the first electrode (the ejection cylinders 15, 15A, 15B). Thereby, the plasma spraying apparatus 1 can sufficiently suppress the adhesion of the spraying powder R1 to the ejection cylinder 15.

[0080] Further, the inner diameter φib of the passage 11a formed by the first inner peripheral surface (the inner peripheral surface 182 of the cylinder part) is smaller than the inner diameter φia of the inner peripheral surface constituting the passage 11a of the nozzle body 12. Thereby, the plasma spraying apparatus 1 can increase the flow rate of the spraying powder R1 and the gas on the first inner peripheral surface.

[0081] In addition, the inner diameter φic of the ejection port 15b is set in the range of 1.1 to 2 times the inner diameter φib of the passage 11a formed by the first inner peripheral surface (the inner peripheral surface 182 of the barrel portion). Thereby, the ejection port 15b of the first electrode (the ejection cylinders 15, 15A, 15B) can be sufficiently widened, and it is possible to avoid the powder R1 for spraying melted by plasma spraying from blocking the ejection port 15b.

[0082] In addition, the first electrode (the ejection cylinders 15, 15A, 15B) is the cathode electrode 52, and the second electrode (the metal block 35) is the anode electrode 53. Thereby, the plasma spraying device 1 can generate plasma between the first electrode and the second electrode.

[0083] In addition, the first electrode (the ejection cylinders 15, 15A, 15B) has an outer peripheral surface (the tip outer peripheral surface 172) whose outer diameter decreases radially inward toward the ejection port 15b. Thereby, the plasma spraying device 1 can make the tip of the first electrode thinner, and can promote the temperature rise.

[0084] In addition, the outer peripheral surface (the tip outer peripheral surface 172) has a tapered shape whose outer diameter decreases radially inward toward the ejection port 15b. Thereby, the plasma generated between the first electrode and the second electrode can smoothly move to the ejection port 15b side of the first electrode.

[0085] In addition, the second electrode (the metal block 35) has a space (the jet passage 35a) through which the powder ejected from the ejection port 15b passes, and the ejection port 15b of the first electrode (the nozzle 11) and the second electrode overlap each other. Thereby, the plasma spraying device 1 can bring the first electrode and the second electrode closer together, and it becomes possible to appropriately control the plasma generation position.

[0086] The plasma spraying apparatus according to the embodiment disclosed this time is illustrative in all respects and not restrictive. The embodiment can be modified and improved in various forms without departing from the scope and gist of the appended claims. The matters described in the above plurality of embodiments can also adopt other configurations within a non - conflicting range, and can be combined within a non - conflicting range.

Explanation of Reference Numerals

[0087] 1 Plasma spraying apparatus 11 Nozzle 11a Passage 12 Nozzle body 15, 15A, 15B Ejection cylinder 15b Ejection port 172 Tip outer peripheral surface 182 Cylindrical inner peripheral surface 183, 183A, 183B Tip inner peripheral surface 19a Tip - side wall thickness 35 Metal block 35a Jet passage 52 Cathode electrode 53 Anode electrode 80 Electrode structure R1 Spraying powder

Claims

1. A plasma spraying device, comprising: a cylindrical nozzle body; a cylindrical first electrode detachably provided at the tip of the nozzle body and having an axis common to the central axis of the nozzle body; a second electrode provided outside the first electrode and having an axis common to the 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 communicating with the passage and capable of ejecting the gas and the powder; the outer diameter of the tip of the first electrode installed at the tip of the nozzle body is smaller than the outer diameter of the outer peripheral surface of the body portion of the first electrode extending with a constant outer diameter along the axial direction of the first electrode; the inner diameter of the ejection port forming edge forming the ejection port by the edge of the foremost end of the first electrode is larger than the inner diameter of the inner peripheral surface of the body portion constituting at least a part of the passage of the first electrode on the base end side of the ejection port forming edge; configured to generate plasma of the gas between the first electrode and the second electrode and melt the powder ejected from the ejection port by the plasma; the first electrode has a base end inner peripheral surface whose inner diameter gradually decreases from the base end opening toward the tip direction, and the inner peripheral surface of the body portion of the first electrode extends with a constant inner diameter along the axial direction from the base end inner peripheral surface and has an inner diameter smaller than the inner diameter of the inner peripheral surface constituting at least a part of the passage of the nozzle body; a plasma spraying device.

2. The tip inner peripheral surface extending from the tip of the body portion inner peripheral surface to the ejection port forming edge has a tapered shape in which the inner diameter gradually increases radially outward toward the ejection port forming edge, The plasma spraying device according to Claim 1.

3. The inclination angle of the tip inner peripheral surface with respect to the extending direction of the body portion inner peripheral surface is set in the range of 1° to 45°, The plasma spraying device according to Claim 2.

4. The axial length of the tip inner peripheral surface is 1 / 2 or less of the axial length of the first electrode, The plasma spraying device according to Claim 2 or 3.

5. The inner diameter of the ejection port forming edge is set in the range of 1.1 times to 2 times the inner diameter of the body portion inner peripheral surface, The plasma spraying device according to any one of Claims 1 to 4.

6. The first electrode is a cathode electrode, The second electrode is an anode electrode, The plasma spraying device according to any one of Claims 1 to 5.

7. The outer peripheral surface of the tip of the first electrode is tapered such that the outer diameter gradually decreases radially inward toward the ejection port, relative to the outer peripheral surface of the body portion of the first electrode. The plasma spraying apparatus according to any one of claims 1 to 6.

8. The second electrode has a space through which the powder ejected from the ejection port passes. The ejection port 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.

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