JP2003213398A - Plasma spraying equipment - Google Patents

Abstract

(57) Abstract: The present invention relates to a plasma spraying apparatus for modifying the surface of a material, which facilitates adaptation to various conditions and increases economic efficiency. SOLUTION: This is a thermal spraying apparatus for performing thermal spraying by means of a plasma arc 3, wherein an air blocking chamber 25 covering from the tip of the thermal spraying torch 9 to the vicinity of a substrate 1 is attached to the thermal spraying torch 9 and the chamber 25 is thermally sprayed. The torch 9 is configured to be able to expand and contract in the axial direction.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a plasma spray apparatus for modifying the surface of a material.

[0002]

2. Description of the Related Art Conventionally, metal spraying and cermet spraying have been widely used for imparting corrosion resistance to machine products and members of large structures such as industrial machines and marine structures. Here, FIG. 3 is a schematic cross-sectional view showing a thermal spray coating formed by thermal spraying in the atmosphere, but as shown in the drawing, generally, pores 24 are formed in the unbonded portions between the thermal spray particles 4 in these thermal spray coatings 2. Exists. In such pores 24, the sprayed particles 4 are oxidized by air entrainment during spraying, an oxide film 23 is formed around the sprayed particles 4, and the oxide film 23 is taken into the coating film 2 as it is and each sprayed particle 4 is formed. It occurs when the gap between them becomes large. In addition to the above, fumes generated by melting of the particles 4 are attached to the thermal spray particles 4 and taken into the coating 2, or fumes attached to the surface of the coating 2 are taken into the coating 2 when they are stacked. As a result, the pores 24 are generated.

When such pores 24 reach the surface of the metal material (base material) 1, open pores are formed and become penetration defects. When such penetrating defects occur, the corrosive liquid or the like in the use environment penetrates and the base material 1 corrodes, causing problems such as cracking of the film 2 and peeling of the film 2. Note that the more pores 24, the higher the frequency of defect generation. In order to prevent such penetrating defects, it is necessary to prevent the spray particles in flight from combining with oxygen in the atmosphere, to sufficiently melt the spray particles, and to suppress the fumes generated by the melting of the spray particles. This is very important.

In view of such a point, the inventors of the present invention have
Japanese Patent Application No. 2000-9494 (Japanese Patent Application Laid-Open No. 2001-20035)
In 4), a thermal spraying device as shown in FIG. 2 was proposed.
In this technique, the thermal spray torch 9 has a cooling mechanism (cooling passage) 1
A small chamber 5 for shutting off air having 2 is attached, and the chamber 5 from the tip of the thermal spray torch 9 to the vicinity of the substrate 1 is
Covered with.

Then, the inflow of air from the outside is restricted by the small chamber 5, and an inert gas is allowed to flow from the auxiliary gas reservoir 8. As a result, the mixture of oxygen into the plasma arc 3 is reduced / prevented to prevent the spray particles from being oxidized, and the distance between the small chamber 5 and the base material 1 is set to 2 to 2.
The separation of 20 mm has the effect of stably discharging the fumes accumulated in the small chamber 5 to the outside of the small chamber 5, and can reduce the fume concentration in the small chamber 5 to reduce the porosity of the thermal spray coating 2. You can

[0006]

By the way, since there is of course an appropriate distance between the thermal spray torch and the base material, in order to spray various types of thermal spray particles under various conditions under optimal conditions, There is a problem that different chambers corresponding to the conditions are required. Further, although thermal spraying under appropriate conditions requires trial and error, there is a problem that it takes time and labor when various chambers are replaced.

On the other hand, it is necessary to flow a large amount of inert gas in order to reduce the mixing of air, but this has a problem of increasing running costs. The present invention was devised in view of such problems, and an object thereof is to provide a thermal spraying device that facilitates adaptation to various conditions and enhances economic efficiency.

[0008]

For this reason, the plasma spraying apparatus of the present invention according to claim 1 is a spraying apparatus for spraying by a plasma arc, wherein the spraying torch has a portion from the tip of the spraying torch to the vicinity of the substrate. A chamber for shutting off air is attached, and the chamber is configured to be expandable and contractable in the axial direction of the thermal spray torch.

Further, in the plasma spraying apparatus of the present invention according to claim 2, in the structure according to claim 1, an air flow curtain for forming an air flow curtain between the chamber and the base material at an end of the chamber. It is characterized in that a forming means is provided. Further, the plasma spraying apparatus of the present invention according to claim 3 is characterized in that, in the configuration according to claim 2, the air flow curtain is formed by air.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION A plasma spraying apparatus according to an embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic sectional view showing the overall structure. Reference numeral 9 in the drawing indicates a thermal spray torch. Inside the thermal spray torch 9, a plurality of small-diameter plasma generation flow paths 14 are provided, and these plasma generation flow paths 14 are the mixing flow paths 13.
It is supposed to meet at.

A powder supply port 10 is formed inside the thermal spray torch 9, and the tip of the powder supply port 10 is connected to the inside of the mixing channel 13. Therefore,
At the time of thermal spraying, the plasmas of the respective plasma generation channels 14 merge in the mixing channel 13, and the thermal spray powder 11 is supplied to the central portion of the plasma of the mixing channel 13 through the powder supply port 10. There is. As a result, the spray particles 4 are ejected from the mixing channel 13 toward the base material 1 to form the spray flame (plasma arc) 3. Further, the spray particles 4 are heated and melted in the plasma arc 3 and solidified after colliding with the base material 1 to form the spray coating 2.

By the way, as shown in FIG.
A small chamber 5 is fitted in the chamber so as to cover the entire circumference of the tip side of the thermal spray torch 9, and the plasma arc 3 generated during thermal spraying is shielded from the atmosphere by the small chamber 5. A part of the small chamber 5 is fitted on the outer periphery of the thermal spray torch 9 and integrated with the thermal spray torch 9.

Around the inner circumference of the small chamber 5, a substantially ring-shaped (doughnut-shaped) auxiliary gas reservoir 8 is provided so as to surround the mixing flow passage 13 of the thermal spray torch 9. A gas supply port 8a for supplying auxiliary gas from the outside is formed in the auxiliary gas reservoir 8, and a plurality of auxiliary gas injection ports 7 are provided on the surface of the auxiliary gas reservoir 8 in the direction of the substrate 1.
Are formed. With such a configuration, the auxiliary gas 6 supplied from the above-mentioned auxiliary gas supply port 8a.
However, the auxiliary gas is ejected from the auxiliary gas ejection port 7 toward the substrate 1. The auxiliary gas 6 is, for example, nitrogen gas, argon gas, or a mixture of these gases.

Further, as shown in the figure, the auxiliary gas ejection port 7
Is formed so as to be inclined with respect to the central axis of the thermal spray torch 9,
The auxiliary gas 6 is jetted out at a predetermined angle (for example, 5 to 30 °) with respect to the central axis (that is, the plasma central axis).
It is set to squirt from. Further, the auxiliary gas 6 is jetted (spouted) from the auxiliary gas jet port 7 at a flow velocity which is 1 to 3 times the flow velocity of the plasma flow.

On the other hand, a cylindrical sliding chamber 20 is provided on the inner periphery of the small chamber 5 on the substrate 1 side. The sliding chamber 20 is provided so as to be slidable in the axial direction with respect to the small chamber, and can be arbitrarily fixed within a slidable range. That is,
The chamber 25 composed of the small chamber 5 and the sliding chamber 20 has a telescopic mechanism that can expand and contract in the axial direction of the thermal spray torch 9. This allows
Even when the distance between the base material 1 and the thermal spray torch 9 changes, the distance between the end portion of the chamber 20 and the base material 1 can be made constant.

An air flow curtain forming means 26 is provided on the front end side of the slide chamber 20 (the base material side, that is, the right side in the drawing). The air flow curtain forming means 26 forms an air flow curtain between the chamber 25 and the substrate 1 to prevent air from flowing into the chamber 25. More specifically, an air pocket 21 is provided on the outer periphery of the slide chamber 20 on the tip side. The air reservoir 21 is provided with an air supply port 24 for supplying high pressure air into the air reservoir 21 from the outside, and an air injection slit for injecting the air supplied from the air supply port 24 as shown in the drawing. 22 is formed. The air injection slit 22 is a slit formed on the circumference and is set so that the opening direction thereof forms a predetermined angle (for example, 60 to 80 °) with respect to the substrate 1.

The air jetted from the slit 22 causes the substrate 1 and the sliding chamber 20.
An air curtain (air curtain) 23 serving as an airflow curtain is formed between and. Also,
The air curtain 23 formed in this way blocks the inflow of air from between the sliding chamber 20 and the base material 1 and prevents the spray particles 4 from being oxidized.

The thermal spraying apparatus according to one embodiment of the present invention is
Since it is configured as described above, at the time of thermal spraying, the small chamber 5 is first fitted to the thermal spray torch 9, and the sliding chamber 20 is adjusted by adjusting the distance between the end of the sliding chamber 20 and the base material 1 to a predetermined distance. Fix it. Then, when the thermal spraying is performed in this state, the thermal spray powder 11 supplied through the powder supply port 10 is supplied to the mixing flow path 13,
The spray particles 4 are ejected from the mixing channel 13 toward the base material, and the plasma arc 3 is formed. This spray torch 9
The thermal spray powder 4 is mixed in the central part of the plasma arc 3 ejected from the plasma arc 3, and the thermal spray powder 4 is heated and melted by the high temperature plasma arc 3 to form the thermal spray coating 2 on the surface of the base material 1. . Further, a part of the melted sprayed powder 4 becomes fumes and floats in the chamber 25.

By the way, generally, the mixing of the outer peripheral portion of the plasma arc 3 and the surrounding gas reaches the central portion as the distance from the jet port of the thermal spray torch 9 increases. Therefore,
If oxygen is contained in the surrounding fluid, even if the central part of the plasma arc 3 is separated from the thermal spray torch 9, the thermal spray powder 4 having a high temperature reacts with oxygen to oxidize the thermal spray powder 4. After contacting and solidifying the base material 1, it becomes an oxide film of the spray particles 4 and the properties of the spray film deteriorate (see FIG. 3).

On the other hand, in the plasma spraying apparatus of the present invention, the expandable chamber 25 including the small chamber 5 and the sliding chamber 20 is provided in the spraying torch 9 in order to prevent the formation of an oxide film. Free circulation is prevented. Further, the distance between the base material 1 and the sliding chamber 20 may be set to an optimum value determined by the sprayed powder 4, base material properties, fume generation amount and spraying conditions. This setting is easy because the sliding chamber 20 is slidable.

Further, the auxiliary gas reservoir 8 in the small chamber 5 is supplied with the auxiliary gas 6, and the auxiliary gas 6 is ejected from the auxiliary gas injection port 7 substantially uniformly in the circumferential direction. The auxiliary gas 6 is nitrogen gas, argon gas, or a mixture thereof, and is used for the small chamber 5 and the sliding chamber 2.
It flows into the space partitioned by 0 and surrounds the plasma arc 3. By thus filling the chamber 5 with the auxiliary gas 6, the plasma arc 3 is protected by the auxiliary gas 6 and the formation of an oxide film is prevented as much as possible, and the mixing of oxygen into the plasma arc 3 is reduced to a minimum. Will be done.

Further, the auxiliary gas 6 together with the fumes floating in the chamber 25, the sliding chamber 20 and the substrate 1
Is discharged from between. Further, in the center portion of the chamber 25, the plasma arc 3 and the auxiliary gas 6 collide with the base material 1 and then are deflected in the outer peripheral direction to slide in the sliding chamber 20.
And the base material 1 flow out. Since the flow velocity at this time is high, the inside of the chamber 25 has a negative pressure with respect to the atmosphere. For this reason, the atmosphere is more likely to flow into the sliding chamber 20 from the vicinity of the end portion thereof. However, in the present invention, the air curtain 23 is formed to block the inflow of the atmosphere and prevent the air from flowing into the chamber 25. .

As described above, according to the plasma spraying apparatus of the present invention, the spraying torch 9 is provided with the simple structure in which the chamber 25 which can be expanded and contracted in the axial direction is provided.
And the substrate 1 regardless of the distance between the chamber 25 and the substrate 1.
It becomes possible to keep a constant distance between and, and it becomes possible to easily adapt to various spraying conditions. Further, by forming an air curtain between the chamber 25 and the base material 1, it is possible to prevent the invasion of the atmosphere into the chamber 25 and prevent the sprayed particles 4 from being oxidized. Then, there is an advantage that the properties of the thermal spray coating 2 are significantly improved. Furthermore, since the inflow of the atmosphere into the chamber 25 can be prevented, the flow rate of the auxiliary gas 6 can be reduced correspondingly, and the cost can be reduced (that is, the economical efficiency can be increased).

Further, by forming the air flow curtain formed on the outer circumference of the chamber 25 with inexpensive air, there is an advantage that the atmosphere blocking effect can be obtained without increasing the cost. The invention of the present application is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention. For example, in the above embodiment, the case where the airflow curtain 23 is formed of air has been described, but the airflow curtain may be formed of another fluid. Further, any structure may be applied to the expansion / contraction mechanism between the small chamber 5 and the sliding chamber 20. Further, the small chamber 5 and the sliding chamber 20 may be provided with a cooling mechanism such as a cooling passage. This cooling passage prevents heating due to high temperature heat during thermal spraying.

[0025]

As described in detail above, according to the plasma spraying apparatus of the present invention as set forth in claim 1, an air blocking chamber for covering the spraying torch tip to the vicinity of the substrate is attached to the spraying torch, and Due to the configuration that the chamber is expandable and contractable in the axial direction of the thermal spray torch,
The distance between the chamber and the base material can be kept constant regardless of the distance between the thermal spray torch and the base material, and there is an advantage that adaptation to various spraying conditions is facilitated.

According to the plasma spraying apparatus of the present invention as set forth in claim 2, in addition to the structure as set forth in claim 1, an air flow curtain forming means for forming an air flow curtain is provided between the chamber and the substrate. With such a configuration, there is an advantage that the invasion of the atmosphere into the chamber can be prevented and the oxidation of the spray particles can be prevented. This also has the advantage of significantly improving the properties of the sprayed coating. Further, there is an advantage that the flow rate of the auxiliary gas can be reduced and the cost can be reduced.

According to the plasma spraying apparatus of the third aspect of the present invention, in addition to the configuration of the second aspect, the cost is increased by forming the air flow curtain on the outer periphery of the chamber with inexpensive air. There is an advantage that the air cutoff effect can be obtained without inviting.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the overall configuration of a plasma spraying apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of a conventional plasma spraying apparatus.

FIG. 3 is a schematic sectional view showing a thermal spray coating formed by a conventional thermal spray device.

[Explanation of symbols]

1 base material 2 Thermal spray coating 3 plasma arc 4 Thermal spray particles 5 Small chamber 6 auxiliary gas 7 Auxiliary gas injection port 8 Auxiliary gas pool 9 Thermal spray torch 10 Powder supply port 11 Thermal spray powder 13 mixing channel 14 Plasma arc flow path 20 sliding chambers 21 Air puddle 22 Air injection slit 23 Air curtain 24 Air supply port 25 chambers 26 Air flow curtain forming means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiromi Etsumi             4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima Mitsubishi             Heavy Industry Co., Ltd. Hiroshima Laboratory (72) Inventor Yasuyuki Kobayashi             4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima Mitsubishi             Heavy Industry Co., Ltd. Hiroshima Laboratory (72) Inventor Manabu Nagata             Hiroshima Prefecture Mihara City Itozakicho 5007 Mitsubishi Heavy Industries             Paper and printing machinery division F-term (reference) 4K031 DA03 EA01 EA10

Claims (3)

[Claims] 1. A thermal spraying apparatus for performing thermal spraying by a plasma arc, wherein a chamber for air cutoff covering from the thermal spray torch tip to the vicinity of a substrate is attached to the thermal spray torch, and the chamber is a shaft of the thermal spray torch. A plasma spraying device, which is configured to be capable of expanding and contracting in the direction. 2. The plasma spraying apparatus according to claim 1, wherein an air flow curtain forming means for forming an air flow curtain between the chamber and the substrate is provided at an end of the chamber. . 3. A plasma spray apparatus according to claim 2, wherein the air flow curtain is formed by air.