JP5284774B2 - Plasma spraying device with particle acceleration nozzle and plasma spraying method - Google Patents

Description

  The present invention relates to a plasma spraying apparatus with a particle accelerating nozzle and a plasma spraying method capable of forming a dense coating by accelerating the flight speed of molten particles in a plasma jet.

  Plasma spraying uses a high-temperature, high-speed plasma flame as a heat source, so even a material with a high melting point can be easily melted and sprayed onto the surface of the base material. Can be formed on the surface.

  FIG. 9 is an explanatory view showing a state in which a film is formed on the surface of a substrate by a conventional plasma spraying apparatus.

  In the figure, a plasma spraying device (plasma gun) 50 has an anode 50a and a cathode 50b made of a copper alloy and tungsten, and these electrodes are connected to a DC power source (not shown). Further, cooling water is supplied to each of the anode 50a and the cathode 50b so as to be protected from a high temperature plasma flame.

  50 c is a supply port for supplying, for example, high-pressure argon gas Ar as a plasma gas, and 50 d is a port for supplying the powder raw material M.

  The plasma flame generated in the plasma generation chamber is converged by the nozzle portion 50e and ejected as a high-temperature, high-speed plasma jet. Colliding to form a film L.

  However, there are many voids of about 5 to 10 μm in the internal structure of the coating L formed by the conventional plasma spraying apparatus 50, and these voids have a considerable influence on the degradation of the coating performance.

  Therefore, a plasma spraying apparatus that can form a denser film with less voids by further accelerating the flight speed of molten particles has been studied.

  As an acceleration nozzle for accelerating the flight speed of the molten particles, for example, an acceleration nozzle provided with an injection port on the inner wall in the circumferential direction of the nozzle hole and configured to inject a high-speed gas flow in a substantially cylindrical shape toward the nozzle tip side Is known (see Patent Document 1).

  10A and 10B show the configuration of the acceleration nozzle. FIG. 10A is a sectional view of the nozzle, and FIG. 10B is an enlarged view of a portion S in FIG.

  In both figures, the accelerating nozzle 60 introduces a carrier gas into the nozzle inlet portion 60a, and the introduced carrier gas passes through the throat portion 60b with a narrowed inner diameter, thereby causing a high-speed mainstream gas flow. Gs is formed, the melted material is atomized by the mainstream gas flow Gs, and the atomized particles are ejected from the nozzle outlet portion 60c.

  Moreover, the acceleration nozzle 60 is comprised from the multistage nozzle which connected several ring-shaped components 61a-61j to the nozzle center axis direction.

  Reference numeral 60d denotes a shield gas supply path penetrating each of the ring-shaped parts 61a to 61i, and the shield gas supply path 60d communicates with an annular passage 60e provided at a connecting portion of the ring-shaped parts 61a to 61j. Each annular passage 60e further communicates with an annular slit (injection port) T formed in the inner wall of the nozzle.

  The slits T are annularly opened in the inner wall step portions of the connected upstream ring-shaped part 61a and downstream ring-shaped part 61b, and are provided in a plurality of stages in the cylinder axis direction of the acceleration nozzle 60. Thereby, the cylindrical shield gas flow SGs is formed around the mainstream gas flow Gs, and the flight speed of the particles can be accelerated.

Therefore, if the plasma jet is the mainstream gas flow Gs and a part of the carrier gas is supplied as the shield gas SGs from the plurality of slits T arranged around the plasma jet, the flight speed of the particles is increased and the plasma jet is increased. The effect of extending the high temperature region of the plasma jet should be obtained.
JP 2008-80323 A

  However, the acceleration nozzle is connected to the nozzle tip of the plasma spraying apparatus, and in order to increase the speed of the molten particles while preventing the adhesion of the molten particles to the inner wall of the nozzle, a huge amount of shielding gas is required. Use of an inert gas as the gas is not practical from the viewpoint of cost.

  Therefore, it is conceivable to use a gas other than the inert gas. In this case, however, a new problem of lowering the temperature of the plasma jet occurs.

  In addition, it is difficult to control the supply of the powder raw material for the plasma spraying device located on the upstream side of the acceleration nozzle because the powder raw material needs to be introduced into the center of the plasma jet using a carrier gas at a pressure higher than the current state. There is a problem of becoming. Further, when the pressure of the carrier gas is increased, there is a problem that the plasma jet is biased and particles adhere to the inner wall of the acceleration nozzle.

  The present invention has been made in consideration of the problems in the conventional plasma spraying as described above, and the first object is to increase the flight speed while preventing adhesion of particles melted in the plasma spraying to the inner wall of the nozzle, A second object of the present invention is to provide a plasma spraying apparatus with a particle acceleration nozzle and a plasma spraying method capable of improving the coating performance, and a second object is to introduce a powder raw material into the plasma jet without biasing the plasma jet and An object of the present invention is to provide a plasma spraying apparatus with a particle acceleration nozzle and a plasma spraying method that can prevent particles from adhering to the inner wall.

The first aspect of the present invention that achieves the above object is to supply a powder raw material as a thermal spray raw material, in a plasma spraying apparatus for forming a film,
An acceleration nozzle connected to a nozzle portion of a plasma gun for injecting the plasma jet;
The accelerating nozzle has a nozzle hole whose inner diameter continuously or stepwise expands toward the tip, and injects a substantially cylindrical shield gas toward the tip of the accelerating nozzle on the inner circumferential wall of the nozzle hole. An injection port is formed to
The injection ports are provided in a plurality of stages in the central axis direction of the nozzle hole, and gas supply passages for supplying gas to the injection ports of the respective stages are individually provided, and at least the most upstream side injection in the plasma jet injection direction. It is a plasma spraying apparatus with a particle accelerating nozzle configured to supply an inert gas or a gas containing an inert gas as a main component to the gas supply path leading to the mouth.

  In the plasma spraying apparatus, it is preferable to provide a powder raw material supply path for supplying the powder raw material to the plasma jet via a carrier gas between the plasma gun and the acceleration nozzle.

  Further, a pair of the powder raw material supply paths can be provided on both sides of the nozzle hole in a direction substantially orthogonal to the central axis of the nozzle hole, and arranged on a line extending radially from the center of the nozzle hole at an equal angle. It can also be set up.

  Moreover, if the said acceleration nozzle is comprised from what connected the some ring-shaped components from which an internal diameter differs in the cylinder shape, the said injection port can be opened cyclically | annularly in the level | step-difference part of the said adjacent ring-shaped component.

  Moreover, it is preferable to form a gas flow deflecting portion for directing the gas flow substantially parallel to the central axis of the acceleration nozzle at the inner peripheral end of the ring-shaped component.

In the second embodiment of the present invention, a gas is supplied to an arc generated between electrodes to form a plasma gas, and a powder raw material is supplied to a plasma jet in which the plasma gas is converged to spray the object to be processed. In the plasma spraying method,
An acceleration nozzle having a nozzle hole whose inner diameter is continuously or stepwise expanded toward the tip is connected to the nozzle portion of the plasma gun for injecting the plasma jet,
Gas is injected from a plurality of injection holes provided in a plurality of stages in the central axis direction of the nozzle hole, and an inert gas or a gas containing an inert gas as a main component is cylindered from at least the most upstream injection port in the plasma jet injection direction. Spray
In the plasma spraying method, a shield gas flow is formed around a plasma jet ejected from the plasma gun, and molten particles passing through the nozzle holes are accelerated.

  In the plasma spraying method, it is preferable to supply a powder raw material through a carrier gas from a powder raw material supply path provided between the plasma gun and the acceleration nozzle.

  Further, the powder is disposed from a powder raw material supply path provided in a pair on both sides of the nozzle hole in a direction substantially orthogonal to the central axis of the nozzle hole or on a line extending radially at an equal angle from the center of the nozzle hole. The powder raw material can be supplied to the plasma jet from a raw material supply path.

  The plasma spraying in the present invention includes both atmospheric pressure plasma spraying performed at atmospheric pressure and reduced pressure plasma spraying performed in a reduced pressure environment.

  Examples of the gas supplied to the gas supply path of the acceleration nozzle of the present invention include oxygen, compressed air, hydrogen, carbon dioxide gas, inert gas such as argon, nitrogen, helium, or a mixed gas thereof.

  Moreover, the gas which has inert gas as a main component shows the gas which contains 1-30% of hydrogen gas by volume percent in inert gas, for example.

  In the present invention, the powder raw material includes metal materials, ceramics, cermets, polymer materials and the like.

  In the present invention, the powder raw material supplied to the plasma jet is not limited to the case of supplying the same kind of material, but also includes the mixed supply of different materials. In addition, for example, a case where a metal material is supplied and then ceramics is supplied, and the type of material is changed over time to be supplied.

  According to the plasma spraying apparatus with a particle acceleration nozzle and the plasma spraying method of the present invention, it is possible to improve the coating performance by accelerating the flight speed of the particles melted in the plasma spraying.

  Further, the powder raw material can be introduced into the plasma jet without biasing the plasma jet to prevent particles from adhering to the inner wall of the nozzle.

  Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.

1 Configuration of Thermal Spraying Device with Particle Acceleration Nozzle FIG. 1 shows the configuration of a plasma thermal spraying device with a particle acceleration nozzle according to the present invention (hereinafter abbreviated as “particle acceleration thermal spraying device”).

  In the figure, a particle acceleration thermal spraying apparatus 1 includes a plasma gun 3 that generates plasma and jets a plasma jet from a plasma gun nozzle portion 2, an attachment component (connection component) 4 provided at the tip of the plasma gun 3, and the attachment. It is mainly composed of an acceleration nozzle 5 provided at the tip of the component 4.

  Hereinafter, the configuration of each unit will be described in detail.

1.1 Attachment Part The attachment part 4 is provided with powder raw material supply paths 6 and 6 for feeding the powder raw material M into the plasma jet F via a carrier gas.

  These powder raw material supply paths 6 and 6 are provided so as to face both the upper and lower sides of the nozzle hole H in a direction substantially orthogonal to the central axis C of the acceleration nozzle 5, and the powder raw material M from two directions with respect to the plasma jet F. To supply.

  If the powder raw material is supplied via the carrier gas only from one direction orthogonal to the plasma jet F as in the conventional powder raw material supply method, the plasma jet F is likely to be biased, and adhesion of the molten particles to the inner wall of the nozzle is caused. To increase.

  On the other hand, if the powder raw material M is supplied from two opposite directions as in the powder raw material supply paths 6 and 6 of the present embodiment, and the supply amount is halved, the carrier gas is supplied. Therefore, the amount of bias of the plasma jet F can be reduced. Thereby, adhesion of the molten particles to the nozzle inner wall can be reduced.

  In addition, although the structure which supplies the powder raw material M from two opposing directions was demonstrated in this embodiment, the powder raw material M can also be supplied from two or more directions. For example, a powder raw material supply path is disposed on a line extending radially at an equal angle from the center of the nozzle hole H in a direction substantially orthogonal to the nozzle hole H, and the powder raw material M is supplied from a plurality of directions toward the center of the plasma jet F. You can also

1.2 Accelerating nozzle The accelerating nozzle 5 is configured to form a cylindrical shield gas flow around the plasma jet F passing through the nozzle hole H. The accelerating nozzle 5 includes a cylindrical main body portion 5a and an inner portion of the main body portion 5a. It is mainly comprised from the nozzle part 5b arrange | positioned at the circumference side.

  The nozzle part 5b has a plurality of ring-shaped parts 5c to 5f, and the plasma jet F passes through the centers thereof.

  Each ring-shaped component 5c to 5f is connected in the direction of the central axis C of the acceleration nozzle 5, and is made of a metal ring that is the first stage on the most upstream side in the injection direction of the plasma jet F (direction of arrow B). The part 5c is arranged, and the ring-shaped part 5d that is the second stage, the ring-shaped part 5e that is the third stage, and the ring-shaped part 5f that is the fourth stage are arranged in order toward the downstream side.

  The nozzle end 5g which is located on the most downstream side in the nozzle portion 5b and is the fifth stage is constituted by a part of the main body portion 5a.

Between the adjacent ring-shaped parts 5c and 5d, 5d and 5e, 5e and 5f, and between the ring-shaped parts 5f and the nozzle end 5g, slits (injection ports for injecting compressed air) toward the injection direction of the plasma jet F, respectively. ) T _{1 to} T ₄ are formed in an annular shape, and the slits T _{1 to} T ₄ are connected to the communication passage 5 i and the gas supply passage 5 j from the compressed air supply ports 5 h and 5 h provided in a pair in the main body 5 a. through ～5M, so that the gas SG ₁ is supplied.

In this embodiment, compressed air is used as the gas SG ₁ , and the supply conditions are, for example, a pressure of 0.5 MPa and a flow rate of ³ Nm ³ / min.

The gas SG ₁ supplied to the gas supply passage 5j~5m is not limited to one, may be composed of a plurality of types. For example, an inert gas or a gas containing an inert gas as a main component can be supplied to the gas supply path 5j, and compressed air can be supplied to the remaining gas supply paths 5k to 5m.

  Further, an inert gas or a gas containing an inert gas as a main component can be supplied to a plurality of gas supply paths among the gas supply paths 5j to 5m, and compressed air can be supplied to the remaining gas supply paths.

  Further, an inert gas or a gas containing an inert gas as a main component can be supplied to all the gas supply paths of the gas supply paths 5j to 5m.

  Further, oxygen, hydrogen, carbon dioxide gas or the like can be used instead of compressed air.

  Furthermore, a mixed gas obtained by mixing the compressed air and an inert gas (or a gas containing an inert gas as a main component) can be supplied.

On the other hand, between the attachment part 4 and the ring-shaped parts 5c, a gas supply passage 5n are provided for supplying gas SG ₂ mainly composed of inert gas or an inert gas, the gas supply passage 5n slits ( The most upstream injection port) T ₀ communicates with an inert gas or a gas containing an inert gas as a main component and is injected into the accelerating nozzle 5 from the slit T ₀ .

  In the following description, a case where argon gas as an inert gas is supplied to the gas supply path 5n will be described.

In the above structure, when accelerating the particles, first, a small argon gas SG ₂ heat capacity relative to the air surrounding the plasma jet F in the upstream side of the accelerating nozzle is supplied as the first shield gas, air entrainment by stabilizing the plasma jet F by preventing a temperature drop of the plasma jet, then used for example compressed air SG ₁ as the second shielding gas only purpose of accelerating the molten particles, thereby, the argon gas only This makes it possible to reduce the consumption of inert gas while obtaining the same acceleration effect as in the case of accelerating particles.

  Further, in each of the ring-shaped parts 5c to 5f, the nozzle hole diameter of the downstream ring-shaped part is formed larger than that of the upstream ring-shaped part, and the slit T is formed using a step generated by the difference in the hole diameter. Secured. In this manner, by gradually expanding the nozzle hole diameter toward the downstream side, it is possible to simultaneously move the nozzle inner wall away from a region where a large amount of molten particles are flying.

Even if the compressed air SG ₁ is supplied from one slit T into the accelerating nozzle 5, if the gas and the particles move for a certain distance, the particles are eventually caused by the disturbance present in the accelerating nozzle 5. It spreads near the inner wall of the house.

Therefore, in the acceleration nozzle 5 of the present embodiment, the acceleration nozzle 5 is configured by connecting a plurality of ring-shaped parts 5c to 5f, and each of the ring-shaped parts 5c to 5f and the ring-shaped parts 5f and the nozzle end 5g is connected. each compressed air SG ₁ from the slit T formed in the portion, jetted to the acceleration nozzle 5 in the nozzle central axis C substantially parallel to the direction, the injection of compressed air SG _1, repeated to a length required for acceleration of the particles Is going.

The interval for supplying compressed air SG ₁ to the acceleration nozzle 5 is determined by the thickness of the ring-shaped parts 5c to 5f, it can usually be selected within a range of 5 to 20 mm.

  For example, if particles adhere to the inner wall of the accelerating nozzle 5, replace with a thin ring-shaped part, and if no particles adhere, adjust the thickness to increase the thickness of the ring-shaped part. Can do.

  The length of the accelerating nozzle 5 necessary for accelerating the particles needs to be changed depending on the spraying material, the supply method thereof, or the gas flow rate in the accelerating nozzle 5, but by changing the number of connected ring-shaped parts. The length of the acceleration nozzle 5 can be adjusted relatively easily.

  In the present embodiment, as described above, the length of the acceleration nozzle 5 can be adjusted by a simple method of changing the number of connected ring-shaped parts, so that it is not necessary to remanufacture the entire acceleration nozzle 5 each time. There are advantages.

  Further, during the maintenance, the accelerating nozzle 5 needs to be disassembled and cleaned. However, since the accelerating nozzle 5 of this embodiment can be disassembled in units of ring-shaped parts, any part of the accelerating nozzle 5 can be cleaned. The time required can be greatly reduced.

It described 1.3 shielding method for supplying supply method compressed air SG ₁ and argon gas SG ₂ gas.

An accelerating nozzle within 5, the plasma gas, compressed air SG _1, so that the state of equilibrium argon gas SG _2, to control the supply of compressed air SG ₁ and argon gas SG _2, compressed air SG ₁ is communicating passage through 5i and the gas supply passage 5J～5m, it is branched to the passage between the between the adjacent ring-shaped parts 5c~5f and ring-shaped part 5f and the nozzle end 5g, is jetted from the slit _T 1 through T _4.

Also, the argon gas SG _2, fed directly into the gas supply passage 5n between the attachment part 4 and the ring-shaped parts 5c, is jetted from the slit T _0.

1.4 Ring-shaped parts Since the ring-shaped parts 5c to 5f have basically the same configuration, the structure will be described below as a representative of the ring-shaped part 5e.

In FIG. 2, the gas flow deflecting portion 5s has a ring-shaped part 5e whose inner peripheral edge on the downstream side protrudes in a jaw shape, and further downstream beyond the upstream end face 5f 'of the adjacent ring-shaped part 5f. by being extended in to form an annular slit T _3. That is, the gas flow deflection part 5s is compressed air SG ₁ and functions as approach section for parallel supply and a nozzle central axis C.

Such a circular slit _{T 3,} between the adjacent ring-shaped parts 5c to 5f, and (see slits _T 1 through T ₄ in FIG. 1) formed in the respective between the nozzle end 5g.

Accordingly, the compressed air SG ₁ that each compressed air supply port 5h, supplied from 5h, the direction of the gas stream by flowing through the passage D is formed in a hook shape by the ring-shaped part 5f and the adjacent gas flow deflecting part 5s There is changed to the nozzle center axis C direction, and is ejected from the slit T ₃ in the acceleration nozzle 5.

  Moreover, the diameter of the through-hole formed in the center of ring-shaped components 5c-5f is comprised so that it may become large in steps toward the injection direction B (refer FIG. 1), and each ring-shaped components 5c- When 5f is connected, the said through-hole becomes the shape which spreads forward.

  FIG. 3 shows another cross section of the particle accelerated spraying apparatus 1.

  In the figure, the same components as those in FIG.

Argon gas supply port 5q the accelerating nozzle 5, 5q is provided, argon gas SG ₂ is adapted to be supplied.

Specifically, the argon gas feed port 5q, argon gas SG ₂ supplied to 5q, through the communication passage 5r, flows through the gas supply passage 5n between the attachment part 4 and the first stage of the ring-shaped parts 5c, the first stage It is adapted to eject the argon gas SG ₂ from the slit T ₀ on the upstream side of the ring-shaped parts 5c.

  The argon gas supply port 5q, the communication path 5r, and the gas supply path 5n function as a gas supply path for supplying an inert gas or a gas containing an inert gas as a main component.

  Note that a gas flow deflecting portion 4a having the same shape as the gas flow deflecting portion 5s of the ring-shaped component is also formed at the peripheral portion of the through hole through which the plasma jet F passes in the attachment component 4.

  Moreover, in the said embodiment, although the nozzle was comprised by connecting two or more ring-shaped components of the same thickness, the thing of different thickness can also be mixed and connected.

  Moreover, although the acceleration nozzle 5 of the said embodiment was comprised with the divergent nozzle which an internal diameter expands in steps toward a nozzle exit, it can also be comprised with the divergent nozzle which expands continuously. In this case, by arranging a large number of injection ports at the circumferential position of the inner wall of the nozzle, the compressed air is injected substantially in parallel with the nozzle central axis and toward the downstream side.

2 Spraying Method Using Particle Accelerated Spraying Device Next, a spraying method of the particle accelerating spraying device 1 having the above configuration will be described with reference to FIGS. 1 and 3.

Accelerating compressed air SG ₁ supplied from the compressed air supply port 5h, a high velocity gas stream from each slit _T 1 through T ₄ of between between each ring-shaped part 5c to 5f, and a ring-shaped part 5f and the nozzle end 5g thereby injected into the nozzle 5, the argon gas SG ₂ supplied from the argon gas supply port 5q, injects the acceleration nozzle 5 from the slit T ₀ between the attachment part 4 and the first stage ring part 5c. Thereby, high speed shielding gas flow covering the inner wall of the nozzle with a mixed stream of compressed air SG ₁ and an argon gas SG ₂ is formed.

  In order to obtain the effect of preventing the adhesion of particles to the inner wall of the nozzle, it is necessary to sufficiently accelerate the particles. For this purpose, a large amount of inert gas is consumed. On the other hand, in the configuration using compressed air together as in the present embodiment, the consumption gas can be reduced.

  On the other hand, the powder raw material M is supplied from the powder raw material supply paths 6 and 6 through the carrier gas, and the supply amount (one direction) is halved from the two opposing directions with respect to the plasma jet F injected from the plasma gun 3. The powder raw material M is charged in a case where the charging amount when charging from only is set to 1). Thereby, the bias of the plasma jet is suppressed, and adhesion of particles to the inner wall of the nozzle can be prevented.

  The particles melted in the plasma jet F further pass through the accelerating nozzle 5 so that the particle flight speed is not attenuated without adhering to the inner wall of the nozzle, and is injected from the outlet of the accelerating nozzle 5. As a result, the molten particles are further accelerated to supersonic speed, and as a result, the molten particles collide with the substrate surface (not shown) at high speed to form a film.

2.1 Particle Velocity Distribution FIG. 4 is a graph comparing the particle velocity obtained by the particle acceleration thermal spraying apparatus 1 of the present embodiment and the particle velocity obtained by a plasma gun having a conventional configuration.

  The horizontal axis indicates the distance from the tip of the plasma gun nozzle (the same applies when the acceleration nozzle is attached to the plasma gun), and the vertical axis indicates the particle velocity. The average particle diameter of the powder raw material is 6 μm.

  In the particle velocity characteristic G1 of the conventional plasma gun, the particle velocity is 570 m / sec at a distance of 70 mm from the tip of the plasma gun nozzle, but the particle velocity decreases to 525 m / sec at a distance of 90 mm.

  In order to obtain a finer film than the conventional plasma gun, in this embodiment, the target value of the particle velocity was set to 600 to 650 m / sec, and the thermal spraying experiment was performed.

  As a result, in the specific G2 according to the present embodiment, the particle acceleration effect of 732 m / sec, which greatly exceeds the target value, was obtained at a position 85 mm from the tip of the plasma gun nozzle.

  Furthermore, a particle acceleration effect of 721 m / sec was obtained even at a position of 105 mm from the plasma gun nozzle tip, and a particle acceleration effect exceeding the target value was obtained at a particle velocity of 666 m / sec at a position of 135 mm from the plasma gun nozzle tip. .

Thus, while suppressing the consumption of the inert gas by a combination of compressed air SG ₁ and an argon gas SG ₂ as a shielding gas, speed of particle velocity has been achieved.

3 Film performance
3.1 Cu coating cross-sectional structure Next, in order to suppress the air entrainment in the plasma jet as much as possible and investigate the influence on the film performance by accelerating the particles, first, the cross-sectional structure of the sprayed coating was observed.

  FIG. 5 (a) shows the cross-sectional structure of the coating when Cu is used as a powder raw material by an external supply method and sprayed using a conventional plasma gun, and FIG. 5 (b) shows the particle accelerated spraying of this embodiment. The film cross-sectional structure when Cu is sprayed by an apparatus is shown.

  In each figure, the left side of the film cross-sectional structure obtained by analyzing the micro observation photograph of the deposit shows the magnification of 200 times and the right side shows the magnification of 1500 times. The average particle diameter of the powder raw material is 30 μm.

  In the conventional thermal spraying, the surface after thermal spraying is discolored black due to oxidation, and as shown in (a) in the figure, the cross-sectional structure includes oxides (see a in the figure) and voids (in the figure). , B)).

  On the other hand, in the thermal spraying according to the present embodiment, the appearance after thermal spraying is very little oxidized and the surface is light brown. Further, as shown in FIG. 4B, the cross-sectional structure has no oxide involvement and very few voids.

  Thus, it was confirmed that the Cu coating formed according to the present embodiment has less oxide entanglement than the conventional Cu coating, and an oxidation inhibiting effect can be obtained.

  In the above embodiment, the case where the inert gas is used so that the reaction between the powder raw material and the atmospheric gas is suppressed inside the accelerating nozzle has been described. However, the powder raw material and the gas are actively reacted chemically. For this purpose, a gas active against the powder raw material can be introduced into the accelerating nozzle.

  Specifically, a powder raw material and a reactive gas (or a mixed gas of an inert gas and a reactive gas) are introduced into an acceleration nozzle, and the reactive gas concentration is changed to change the powder raw material and the reactive gas. By controlling the chemical reaction, a film having the desired composition can be formed.

  For example, using titanium powder raw material, using argon as an inert gas and nitrogen as a reactive gas, respectively, and changing the reactive gas concentration includes a soft and highly ductile titanium film and titanium nitride. A hard titanium film can be formed.

  Moreover, if the reactive gas concentration is continuously changed during thermal spraying, a film whose hardness changes continuously in the thickness direction can be formed.

3.2 Cross-sectional structure of alumina film FIG. 6 is a diagram comparing the cross-sectional structures of an alumina film formed by a conventional apparatus and an alumina film formed by the present embodiment.

  FIG. 4A shows a conventional alumina film in which powder raw materials are supplied by an external supply method, and FIG. 4B shows an alumina film according to the present embodiment.

  As shown in FIG. 6 (a), the alumina film formed by the conventional apparatus has a porosity of 10% or more, and since there are many gaps between particles, it is estimated that the bonding force is weak. Further, when the dielectric breakdown voltage was measured, it was less than 1 kVDC when the film thickness was 200 μm.

  On the other hand, in the alumina film according to the present embodiment, the porosity remains at 2 to 4%, and there are only small pores of about 1 to 2 μm. Further, when the dielectric breakdown voltage was measured, it was 10 kVDC or more when the film thickness was 200 μm, and it was confirmed that the film performance was superior to the conventional film.

3.3 Abrasion Test Results FIG. 7 is a graph comparing the wear resistance of the alumina film by the conventional apparatus and the wear resistance of the alumina film according to this embodiment.

  The graph shows the results of a suga-type wear test for evaluating abrasive wear. The horizontal axis represents the average particle diameter of alumina used as a powder raw material, and the vertical axis represents the total amount of wear.

  The spraying distance was 70 mm.

  As shown in the characteristic G3, in the film formed using alumina having an average particle diameter of 6 μm, the total wear amount was 38.2 mg in the film by the conventional apparatus, but the film according to the present embodiment has the characteristic G4. Thus, the total amount of wear was reduced to 17.6 mg, and the improvement of the film performance was confirmed.

  When alumina having an average particle size of 20 μm is used, there is almost no difference in the total amount of wear between the coating by the conventional apparatus and the coating by the present embodiment. It is presumed that the inter-bond strength increases.

  Also, when alumina was sprayed with an average particle diameter of 6 μm and sprayed at a spraying distance of 50 mm, the total wear amount was reduced to 11.8 mg (see point c in the white triangle symbol in the figure), making it more wear resistant. It was confirmed that an excellent film was obtained.

  In the figure, point d shows the wear resistance of a film formed by a conventional apparatus using alumina having an average particle diameter of 3 μm as a reference example, and the substrate was exposed after 400 times of friction.

  On the other hand, the total amount of wear of the film formed by this embodiment was reduced to 11 mg (see point e in the graph), and it was confirmed that a film with more excellent wear resistance was obtained.

3.4 Dielectric Breakdown Voltage Measurement Results FIG. 8 shows a film formed by supplying powder material from one direction and spraying with a conventional apparatus, and a film formed by supplying and spraying powder material from two directions in this embodiment. It is the graph which compared the dielectric breakdown voltage.

  In the graph, the horizontal axis represents the spray distance, and the vertical axis represents the dielectric breakdown voltage value.

  The sprayed film thickness was 200 μm.

  In the figure, characteristics G5 to G7 are obtained by measuring the dielectric breakdown voltage when alumina having an average particle diameter of 10 μm is used as the spray material and the spray distance is changed. The dielectric breakdown voltage value (average value) was 9.38 (G5), 10.11 (G6), and 10.11 (G7) kVDC, and particles adhered to the inner wall of the nozzle during spraying.

  Characteristics G8 and G9 are obtained by measuring the dielectric breakdown voltage when using alumina having an average particle diameter of 20 μm and changing the spraying distance. Dielectric breakdown voltage values (average values) are 8.93 (G8) and 8.61 (G9) kVDC, and although the breakdown voltage value is lower than that of a film using alumina having an average particle diameter of 10 μm, thermal spraying is performed. At times, no adhesion of particles to the inner wall of the nozzle was observed.

  In order to form a dense film, it is desirable to use a particle size smaller than an average particle size of 20 μm, more preferably an average particle size of less than 10 μm as a powder raw material. Accordingly, when alumina having an average particle diameter of 6 μm was used and sprayed at a spray distance of 75 mm, the dielectric breakdown voltage value (average value) was 8.11 (G10), but there was adhesion to the inner wall of the nozzle. .

  Each of the above characteristics G5 to G10 is obtained by supplying the powder raw material from one direction.

  On the other hand, in the method of spraying by supplying the powder raw material from two opposing directions of this embodiment, the dielectric breakdown voltage value (average value) that exceeds the dielectric breakdown voltage of the film formed by the conventional apparatus is 11.48 (G11 ) KVDC was obtained, and no adhesion of particles to the inner wall of the nozzle was observed.

  In addition, although the said embodiment demonstrated the structure which supplies a powder raw material from two opposing directions, it can also supply along the central axis C of not only this but a nozzle.

  The plasma spraying apparatus includes a spray gun configured to generate a plasma jet from three electrodes. When mounting the accelerating nozzle of the present invention on the spray gun having such a configuration, the powder raw material is introduced from the vicinity of the center of the plurality of electrodes in the same direction as the jet direction of the plasma jet, and the molten particles can be accelerated by the accelerating nozzle. it can.

It is sectional drawing which shows the structure of the particle acceleration spraying apparatus which concerns on this invention. It is principal part sectional drawing explaining the shape of the gas flow deflection | deviation part in the ring-shaped components shown in FIG. It is the FIG. 1 equivalent view which shows another cross section of the particle | grain accelerated spraying apparatus which concerns on this invention. It is the graph which compared the particle flight speed by the particle acceleration thermal spraying apparatus of this embodiment, and the particle flight speed by a conventional apparatus. (a) is the film | membrane cross-sectional structure | tissue formed with the conventional apparatus, (b) is the film | membrane cross-sectional structure | tissue formed with the particle | grain accelerated spraying apparatus of this embodiment. (a) is a cross-sectional structure explaining the porosity of the film formed by the conventional apparatus, and (b) is a cross-sectional structure explaining the porosity of the film formed by the particle accelerated spraying apparatus of the present embodiment. It is the graph which compared the abrasion resistance of the alumina film by this embodiment, and the alumina film by a conventional apparatus. It is the graph which compared the dielectric breakdown voltage value by the unidirectional powder raw material supply system by a conventional apparatus, and the bi-directional powder raw material supply system by this embodiment. It is explanatory drawing explaining the thermal spraying principle by the conventional plasma spraying apparatus. (a) is sectional drawing which shows the structure of the conventional acceleration nozzle, (b) is the S section enlarged view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Particle acceleration spray apparatus 2 Plasma gun nozzle part 3 Plasma gun 4 Attachment part 4a Gas flow deflection | deviation part 5 Acceleration nozzle 5a Main body part 5b Nozzle part 5c-5f Ring-shaped part 5g Nozzle end 5h Compressed air supply port 5i Communication path 5j-5m Gas Supply path 5n Gas supply path 5q Argon gas supply port 6 Powder raw material supply path 5r Communication path 5s Gas flow deflection unit F Plasma jet SG ₁ Compressed air SG ₂ Argon gas T ₀ , T _{1 to} T ₄ slit (injection port)

Claims (8)

In a plasma spraying apparatus for forming a film by supplying a powder raw material as a thermal spraying raw material,
Having an acceleration nozzle which is connected to the nozzle of the plasma gun that injects flop plasma jet,
The accelerating nozzle has a nozzle hole whose inner diameter continuously or stepwise expands toward the tip, and injects a substantially cylindrical shield gas toward the tip of the accelerating nozzle on the inner circumferential wall of the nozzle hole. An injection port is formed to
The injection ports are provided in a plurality of stages in the central axis direction of the nozzle hole, and gas supply passages for supplying gas to the injection ports of the respective stages are individually provided, and at least the most upstream side injection in the plasma jet injection direction. An inert gas or a gas containing an inert gas as a main component is supplied to the gas supply path that communicates with the mouth, and at least of the above-described jet ports other than the most upstream jet port, A plasma spraying apparatus with a particle acceleration nozzle, wherein compressed air, oxygen, hydrogen, or carbon dioxide gas is supplied to the gas supply path leading to one of the injection ports.   The plasma spraying apparatus with a particle acceleration nozzle according to claim 1, wherein a powder raw material supply path for supplying the powder raw material to the plasma jet via a carrier gas is provided between the plasma gun and the acceleration nozzle.   The powder raw material supply path is disposed on a pair of sides of the nozzle hole in a direction substantially orthogonal to the central axis of the nozzle hole, or on a line extending radially at an equal angle from the center of the nozzle hole. The plasma spraying apparatus with a particle acceleration nozzle as described.   The acceleration nozzle is formed by connecting a plurality of ring-shaped components having different inner diameters in a cylindrical shape, and the injection port is annularly opened at a step portion of the adjacent ring-shaped component. The plasma spraying apparatus with a particle acceleration nozzle of any one of Claims 1.   The plasma spraying apparatus with a particle acceleration nozzle according to claim 4, wherein a gas flow deflecting portion for directing the gas flow substantially parallel to a central axis of the acceleration nozzle is formed at an inner peripheral side end of the ring-shaped component. . In a plasma spraying method in which a gas is supplied to an arc generated between electrodes to form a plasma gas, a powder raw material is supplied to a plasma jet in which the plasma gas is converged, and sprayed onto a processing target.
An acceleration nozzle having a nozzle hole whose inner diameter is continuously or stepwise expanded toward the tip is connected to the nozzle portion of the plasma gun for injecting the plasma jet,
Gas is injected from a plurality of injection holes provided in a plurality of stages in the central axis direction of the nozzle hole, and an inert gas or a gas containing an inert gas as a main component is cylindered from at least the most upstream injection port in the plasma jet injection direction. And injecting compressed air, oxygen, hydrogen, or carbon dioxide in a cylindrical shape from at least one of the above-mentioned injection ports other than the most upstream injection port in the direction of plasma jet injection And
A plasma spraying method characterized by forming a shield gas flow around a plasma jet ejected from the plasma gun and accelerating molten particles passing through the nozzle hole.   The plasma spraying method of Claim 6 which supplies a powder raw material via a carrier gas from the powder raw material supply path provided between the said plasma gun and the said acceleration nozzle.   A pair of powder raw material supply paths provided on both sides of the nozzle hole in a direction substantially perpendicular to the central axis of the nozzle hole and arranged on a line extending radially from the center of the nozzle hole at an equal angle. The plasma spraying method according to claim 7, wherein the powder raw material is supplied to the plasma jet.