JPS60187360A - Plasma spray gun - Google Patents

Abstract

PURPOSE:To raise the temp. of sprayed plasma particles sufficiently and to accelerate the particles by providing a feeding hole of the material to be sprayed communicating with a plasma space and extending prallelly to the direction of plasma jet, to a cathode. CONSTITUTION:A hole 206 for feeding a material to be sprayed penetrating from one end of the hole through the cathode 201 and opening at a plasma space 202 with another end of the hole extending in the parallel direction to the plasma jet through a conductor 208 and opening at a side of a hopper for the material to be sprayed, is formed in the axial center of a conductor 208. By this constitution, particles to be sprayed are sent to a space adjacent to a position generating plasma jet, therefore, the particles are heated to sufficiently high temp. and accelerated to aquire high energy.

Description

[Detailed description of the invention]

The present invention relates to an improvement in a plasma spray gun, and more specifically, it increases the energy of spray particles in a plasma jet and enables uniform spraying. A method of forming a film by plasma spraying various metal materials, non-metal materials, or a mixture thereof in order to impart corrosion resistance, wear resistance, heat resistance, or heat insulation to the surfaces of various plants, prime movers, and machinery parts. has been adopted. In order to form a high-quality thermal spray coating using the plasma spraying method, it is necessary to increase the total energy of the spray particles of the plasma jet, make them uniform, increase the adhesion between the surface of the workpiece and the spray coating, and increase the bonding force of the spray particles. It is necessary to form a thermal spray coating with high durability. The principle of construction of a plasma spray gun is to eject plasma generated by supplying electric power between a cathode and an anode disposed through a certain plasma space to the outside of the plasma space as a plasma jet, and to eject the plasma into the plasma jet. The spray material is supplied to heat and accelerate the spray particles to emit high-energy spray particles. The structure of the conventional plasma spray gun 100 constructed based on this principle is as shown in FIG. An annular anode 103 is disposed in the plasma space 102.
A passage 104 for ejecting the generated plasma to the outside of the entire space 102 is provided at the tip thereof, and a gas supply passage 105 for supplying working gas from a gas supply source (not shown) to the plasma space 102 is provided. An internal thermal spray material supply hole 106 communicating in a direction perpendicular to a passage 104 through which a plasma jet is ejected is provided, and an external thermal spray material supply pipe 107 is provided at the tip of the annular anode 103 in a direction perpendicular to the through passage 104. There is. A cathode-side electrical conductor 108 is fixed in the extending direction of the rod-shaped cathode 101 , and the outer periphery of the cathode-side electrical conductor 108 is supported by an insulator 109 and electrically insulated from the annular anode 103 . One end is connected to an insulator 109. Furthermore, a cooling water inlet 110 and an outlet 111 are formed on the outer surface of the annular anode 103 and the cathode-side conductor 108, respectively. It is connected to a cooling water circulation path 112 formed within the cathode side conductor 108. When performing plasma spraying using the plasma spray gun 100 having the above structure, cooling water is flowed from the cooling water inlet 110 to the discharge port 111 through the cooling water circulation path 112 to the plasma spray gun 100f: At the same time as cooling, A gas supply source (not shown) is connected to the space 1 via a gas supply path 105.
A working gas (Ar, He, or N! gas or a mixture thereof is used, and H. is added in some cases) is introduced into the 02. Next, the annular anode 103 is connected to the DC power source (not shown).
While applying a positive voltage to the rod-shaped cathode 101 and a negative voltage to the rod-shaped cathode 101,

[7] Spark discharge is generated between the annular anode 103 and the rod-shaped cathode 101 due to high-frequency electrolytic corrosion. Due to this spark discharge, a plasma arc is generated between the anode 103 and the cathode 101 due to the DC voltage applied between the negative and positive electrodes. At the point when this plasma arc occurs, the supply of high frequency voltage is stopped. A plasma arc generated between the anode 103 and the cathode 101 fills the space 102 with high-temperature, high-pressure plasma gas, and a high-temperature, high-pressure plasma jet is ejected from the through passage 104 . Further, when the spray material supply hole 106 or the supply pipe 107 is fed into the plasma jet from a spray material material hopper (not shown), the fed spray particles are sprayed particles 113 (high energy spray particles) or 114 (low energy spray particles). thermal spray particles)
As a result, the temperature is rapidly raised, accelerated, and radiated onto the surface of the coating member 115. As described above, in the conventional plasma spray gun 100, the supply port for the spray powder is relatively close to the end of the plasma jet nozzle 104, and the spray powder supply direction is perpendicular to the flow of the plasma jet. Some of the spray particles fed into the jet are supplied to the center of the plasma and emitted onto the high-energy beam member 115 surface, but other spray particles are deviated from the center of the plasma jet. , the plasma jet is emitted in a direction that deviates significantly from the flow direction of the plasma jet without being sufficiently heated or accelerated. This phenomenon in which the spray particles are separated from the center of the plasma jet and are not sufficiently heated and accelerated occurs in the same way for spray particles supplied from the internal spray material supply hole and the external spray material supply pipe. It is. As described above, the conventional plasma spray gun [00] supplies the spray material from a direction perpendicular to the flow direction of the plasma jet, so some of the spray material particles are supplied to a part away from the center of the plasma jet. There was a tendency for the thermal spray particles to collide and adhere to the surface of the target member 115 without being sufficiently heated and accelerated. For this reason, the adhesion between the front cover film and the surface of the coating member and the mutual bonding force between the sprayed particles in the lateral film are made low, and the durability of the heat treatment film is reduced. This was a major practical problem as it weakened the resistance of the film to peeling. The present invention has been devised to eliminate the above-mentioned drawbacks in plasma spray guns, and the spray material particles are supplied as far as possible to the center of the plasma jet stream, so that the spray particles are sufficiently heated and accelerated. The purpose is to provide a plasma spray gun with a structure. In order to achieve this purpose, a voltage is applied between the cathode and anode of the plasma spray gun of the present invention, which are disposed through a certain plasma space, and the generated plasma is sent out of the plasma space as a plasma jet. In a plasma spray gun that emits high-energy spray particles by supplying the spray material into the plasma jet to raise the temperature and accelerate the spray particles, the cathode is in communication with the plasma space [7, and in a direction parallel to the plasma jet. It is characterized in that it is provided with an extending thermal spray material feed hole. Next, one embodiment of the present invention will be described. As shown in FIG. 3, the plasma spray gun 200 of the embodiment has a plasma spray gun 200 that is connected to the outer periphery of a cathode 201 via a plasma space 202.
A claw, 4Q annular anode 203 is arranged concentrically with the cathode 201 as the central axis, and at the tip of the plasma space 202,
A through passage 204 is provided for jetting the generated plasma outward from the space 202, and a gas supply passage 205 is provided for supplying working gas from a supply source (not shown) into the plasma space 202. The cathode 201 has a tip portion made of tungsten or a tungsten alloy, and a cathode-side conductor 20 made of copper or copper alloy at the end opposite to the protrusion inside the plasma space 202 of the cathode 201.
8 is fixed, and the outer periphery of the cathode side conductor 208 is covered with an insulator 20.
Supported by 9. Further, the insulator 209 is an annular anode 20
3, and the cathode 201 and the annular anode 20
It serves to electrically insulate between 3 and 3. Further, a cooling water inlet 210 is provided on the outer peripheral surface of the annular anode 203.
a and an outlet 211a are provided, and these inlet 210a
The discharge port 211a is connected to a cooling water circulation path 212a formed in the peripheral wall surface of the annular anode 2030. Further, a cooling water inlet 21 is provided on the outside of the cathode side conductor 20a.
0b and a discharge port 211b are provided, and the conductor 208
A cooling water circulation path 212b is provided in the wall body and connects to a cooling water inlet 210b and an outlet 211b.
At the axis of 08, there are sprayed material particles whose one end passes through the cathode 201 and opens into the plasma space 202, and whose other end extends inside the conductor in a direction parallel to the plasma jet and opens toward a sprayed material hopper (not shown). 206 is formed. Further, the cathode 201 and the anode 203 are respectively connected to a DC power source and a high frequency source (not shown). When plasma spraying is performed using the plasma spray gun 200 having the above structure, (1) Cooling water is first flowed from the cooling water inlets 210a and 210b through the cooling water circulation channels 212 & and 212b, respectively, to the discharge ports 211a and 211b, and then plasma spraying is performed. While cooling the gun 200, the gas supply hole 205
A working gas (Ar 1He, N, gas, or a mixture thereof is used, and H8 may be added in some cases) is introduced into the space 202 from a gas supply source that is not shown throughout. @ Next, the annular anode 2 is connected to the DC power source (not shown).
A positive voltage is applied to the annular anode 203 and a negative voltage is applied to the cathode 201, and the annular anode 203 and the cathode 201 are applied from a high frequency power source (not shown).
A spark discharge is generated between the Due to this spark discharge,
A plasma arc is generated between the anode 203 and the cathode 201 due to the DC voltage applied between the negative and positive electrodes. At a certain point when a plasma arc occurs, the supply of high-frequency voltage is stopped. The space 202 is filled with high-temperature, high-pressure plasma due to the plasma arc generated on the anode 203 and cathode 201 sides, and a high-temperature, high-pressure plasma jet is ejected from the through passage 204 . Furthermore, when the sprayed material IX is supplied from a sprayed material hopper (not shown) into the sprayed material particles 206, this sprayed material is heated and accelerated by the plasma jet from the plasma arc jet 1fjM2o4, and is radiated onto the surface of the coating member 215. Ru. Using the plasma spray gun 200 of the above embodiment (hereinafter referred to as "one embodiment gun") and the plasma spray gun 100 of the conventional structure shown in FIG. 1 (hereinafter referred to as "conventional gun"),
When plasma spray particles are emitted from each, the results shown in FIGS. 4 and 5 are obtained when characteristic diagrams of the velocity distribution of the spray particles in a direction perpendicular to the flow direction of the plasma jet are shown. The characteristic diagrams in FIGS. 4 and 5 represent the average speed (m 7 seconds) at spraying distances of 100 m and 150 m, respectively. Comparative measurements were made in the following cases. ■ Current meter uses an Ar laser with a wavelength of 0.5145μ, a laser beam intersection angle of 3.49 deg, and an interference fringe spacing of 8.448p.
Measured in m. [Yes] Thermal spraying Plasma arc current: 800A Plasma arc voltage = 35V Working gas: Ar(50)/wig) 10He(20)/m
)■Thermal spray powder ZrO! Powder (particle size: 10-40μm) or 8ONi-2Or powder (particle size: 40-1oopm) However, curves a-1゜a-■ and b in Figures 4 and 5
-1 and b-1 are plasma spray guns 20 of the embodiments, respectively.
The spray powder to be fed into the plasma jet in the plasma spray gun 100 shown in FIG.
This is a characteristic curve obtained when the product shown in -1 is used. Table-■ From the characteristic diagrams in Figures 4 and 5, it can be seen that when the example gun is used, the flight speed of the sprayed particles is improved compared to when the conventional gun is used, and the velocity distribution in the orthogonal direction of the plasma jet flow is improved. It can be seen that it has become uniform. This tendency is due to the fact that the spray material fed into the plasma jet contains ZRO, powder and 80
Similar results can be obtained not only when using Ni-20Cr powder but also when using other thermal spray materials. Furthermore, the covering member is made of 18Cr-8Ni stainless steel (φ
15
According to the same condition, the 8ONi-20Cr film was 0.3 I
After thermal spraying to II thickness, KZrO,
-8% Y, 03 film was sprayed to a thickness of 0.611 on a test piece.
Figure 6 shows the results of a repeated thermal cycle test between room temperature and 1.000°C. In FIG. 6, the vertical axis shows the number of repetitions, and the horizontal axis shows the type of test piece. Group a-III uses the example gun, and group b-[1 uses the conventional gun. Indicate the case. Among the characteristic curves, a characteristic curve with an arrow at the top indicates that there was no abnormality at all during that number of thermal cycles,
Items with an "X" mark indicate that cracks have occurred in the thermal sprayed coating due to that number of thermal cycles, and items with a [mu] mark indicate that the thermal sprayed coating has peeled off due to that number of thermal cycles. . As can be seen from FIG. 6, the heat-cycle cracking and peeling resistance of the thermal sprayed coating formed with the example gun is far superior to that of the conventional gun. As is clear from the above description, the plasma spray gun according to the present invention has the following advantages: (1) The spray material is fed into the jet in parallel with the plasma jet flow, so that it flies in a direction away from the center of the plasma jet flow. Thermal spray particles are extremely reduced. ■ Since the thermal spray particles are sent into the space close to the plasma jet generation part, the thermal spray particles are sufficiently heated and accelerated and are emitted as high-energy spray particles, so that the thermal spray on the surface of the target member 215 is reduced. There are almost no unmelted particles in the coating9, and the adhesion between the coating member 215 and the thermal spray coating is high. Furthermore, the bonding strength between the sprayed particles forming the thermal sprayed coating was high, and the variation in adhesion and interparticle bonding force could be significantly reduced, making it possible to form a thermal sprayed coating of excellent quality.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the structure of a conventional plasma spray gun.
Figure 2 is an explanatory diagram showing the flight state of particles emitted from the plasma spray gun in Figure 1, Figure 3 is a sectional view showing the structure of the plasma spray gun of the embodiment, and Figures 4 and 5 are 6 is a characteristic diagram showing the velocity distribution of spray particles emitted from the plasma spray gun of the embodiment and the conventional plasma spray gun, and FIG. 6 shows the heat of the sprayed coating formed by the plasma spray gun of the embodiment and the conventional plasma spray gun. FIG. 3 is a characteristic diagram showing cycle test results. In the drawing, 100... Conventional plasma spray gun, 200... Plasma spray gun of the example, 101.201... Cathode, 102.202... Plasma space, 15- 103.203... Anode , 104.204...Plasma jet ejection passage, 105.205...Working gas supply path, 06 108.208...Cathode side conductor, 109.209...Insulator, 112.212a, 212b ---Cooling water circulation path, patent applicant: Mitsubishi Heavy Industries, Ltd. Sub-agent Patent attorney: Shibu Mitsuishi (and 1 other person) 161

Claims (1)

[Claims] Electric power is supplied between a cathode and an anode arranged through a certain plasma space, the generated plasma is ejected from the plasma jet as a plasma jet, and a molar substance is supplied into the plasma jet so that it can be ejected. A plasma spray gun that heats and accelerates particles and emits high-energy spray particles, characterized in that the cathode is provided with a spray material feed hole that communicates with the plasma space and extends in a direction parallel to the plasma jet. Plasma spray gun