JPH03107447A - Plasma thermal spraying method - Google Patents

Abstract

PURPOSE:To eliminate unmolten particles in a thermal spraying material and to form a thermally sprayed film having an excellent adhesive property by forming the cathode of a plasma torch to a hollow shape and passing a laser beam therein at the time of forming the molten film of the thermal spraying material onto the surface of a material to be treated by a plasma thermal spraying method. CONSTITUTION:A high voltage is impressed between an anode 3 and a cathode 4 to convert a high-velocity gas to plasma while the gas is ejected to a gaseous plasma passage 2 between the anode 3 and cathode 4 of the plasma thermal spraying torch 1. The powder of the thermal spraying material is supplied from an outlet 6 provided in the torch body 1 and is melted by the plasma. The powder of the thermal spraying material is then thermal sprayed to the surface of the material to be treated. The unmolten powder exists in a part of the thermal spraying material powder in this case and impairs the adhesive property of the thermally sprayed film, thereby generating defects, such as peeling and cracking, in the thermally sprayed film. The laser beam is, therefore, passed in an optical fiber 9 from a laser oscillator 8, is passed in the hollow part of the cathode 4 and is condensed by a condenser lens 10. The melting of the thermal spraying powder 12 by a plasma flame 11 is intensified by this laser beam, by which the powder is completely melted. The thermally sprayed film which has the high adhesive property and is free from the cracking and peeling is stably formed on the surface of the material to be treated.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a plasma spraying method.

[Conventional technology]

In the conventional plasma spraying method, a voltage is applied while flowing high-speed gas between the cathode and anode in the torch to create a plasma.
This is a method of supplying thermal spray material in the form of powder, wire, etc. into this plasma, melting the thermal spray material, and spraying the material at high speed to coat the object to be thermally sprayed.

However, in such a conventional plasma spraying method, as shown in the explanatory diagram of FIG.
In order to supply the thermal spray material 12, the material 12 is not completely melted, and some unmelted powder 16 is mixed with the molten powder 15 in a solid state and is sprayed onto the object to be sprayed. If the molten powder 16 is present, it not only causes defects in the film itself, but also causes pores to remain around the molten powder, causing cracks and peeling of the film.

[Problem to be solved by the invention]

The present invention was proposed in view of these circumstances, and
An object of the present invention is to provide a plasma spraying method that eliminates unmelted particles of a thermal spray material during thermal spraying, eliminates defects such as cracks and peeling of the coating, and improves performance such as adhesion of the coating.

[Means to solve the problem]

To this end, the present invention provides a method for melting and spraying material by a plasma flame generated between an anode and a cathode of a plasma spray torch. The method is characterized by heating and melting the sprayed material using plasma flame and laser light.

[Effect]

In the plasma spraying method of the present invention, the laser beam introduced into the cathode hollow portion acts as an auxiliary heat source to completely melt the sprayed material, and the unmelted sprayed material that cannot be completely melted by the plasma flame is heated to a high temperature. Laser light with energy density is irradiated to completely melt the sprayed material. By completely melting the sprayed material through cooperative heating between plasma flame and laser light, defects such as pores in the coating are eliminated, and defects such as cracking and peeling of the coating are prevented, and the adhesion, density, etc. of the coating are improved. performance is improved.

〔Example〕

An embodiment of the plasma gas passage of the present invention will be explained with reference to the drawings. Fig. 1 is a longitudinal cross-sectional view showing a thermal spraying torch for carrying out the method of the present invention, Fig. 2 is a longitudinal cross-sectional view showing the thermal spraying situation of the method of the present invention, FIG. 3 is an explanatory diagram of the melted state of the thermal spray material in the same as above.

In FIG. 1, a torch main body 1 has an axial inner cavity formed in a plasma gas passage 2 and an anode 3 at the tip thereof, and a hollow cathode 4 disposed in the plasma gas passage 2. It is inserted from the proximal end. Torch body
A thermal spraying material passage 5 is bored in the torch body 1 and the cathode 4 has a cooling water passage 7, the tip of which opens at the anode 3 portion as a thermal spraying material outlet 6.

An optical fiber 9 connected to a laser oscillator 8 is connected to the rear end of the cathode 4.
A condensing lens 10 is disposed near the connection portion inside.

To explain the thermal spraying situation using such a thermal spray torch with reference to Figs. 2 and 3, a voltage is applied while flowing high-speed gas from the plasma gas passage 2 between the cathode 4 and the anode 3 to form a plasma. When carrying out thermal spraying by continuously supplying the powder spray material 12 into the plasma flame 11 and blowing it away with high-velocity gas, the laser beam 13 focused by the condenser lens 10 passes through the optical fiber 9 from behind and is directed into the plasma flame 11. and irradiates the thermal spray material 12 to obtain a flying powder 14.

At this time, as shown in FIG. 3, the thermal spray material 12 supplied from the tip of the torch body 1 is heated by the high-temperature plasma flame 11 and at the same time by the laser beam 13, and is completely heated by both heat sources. It becomes molten powder 15 in a molten state and flies away.

Further, since the laser beam 13 is irradiated from the same axis as the plasma flame 11, the entire thermal spray material 12 is irradiated with the laser beam 13, and complete melting of the thermal spray material 12 is effectively and reliably performed.

If the laser beam 13 is irradiated from a direction perpendicular to the plasma flame 11, the sprayed material 12 will fly while spreading, and the laser beam 13 will not irradiate the entire flying powder because the powder on the irradiation side will be in the shadow. .

Although this embodiment shows the case where the thermal spray material 12 is a powder, the same construction is possible with a wire-shaped material.

Further, although the focal position of the laser beam 13 is shown to be connected within the plasma flame 11, it may be in front of the plasma flame 11.
The appropriate value is determined by the laser output, wavelength, type of thermal spray material 12, etc.

Thus, according to this plasma spraying method, the spraying material 12
It is now possible to fly in a completely molten state,
Flying powder 14 that flew in a completely molten state and collided with the object to be sprayed
The material will sufficiently wet and spread on the surface of the material to be sprayed, thereby increasing its adhesion to the material and eliminating pores in the abrasive coating, resulting in cracking and peeling of the coating. Defects such as these are eliminated, and the film performance is improved.

[Effects of the Invention] In short, according to the present invention, the anode of a plasma spray torch,
When performing thermal spraying by melting the spraying material with the plasma flame generated between the cathodes, the above-mentioned cathode is made into a hollow shape, and a laser beam is guided from behind in the same axis direction as the plasma flame into the hollow part, and the plasma flame and laser beam are used to spray the material. By heating and melting the abrasive material, we can obtain a plasma spraying method that eliminates unmelted particles of the thermal spray material during thermal spraying, eliminates defects such as cracking and peeling of the coating, and improves the performance of the coating such as adhesion. Invention is an extremely useful industry.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view showing a cutting torch for carrying out the method of the present invention in an embodiment of the plasma spraying method of the present invention, Fig. 2 is a longitudinal cross-sectional view showing the thermal spraying situation of the method of the present invention, and Fig. 3 is the same as above. FIG. 3 is an explanatory diagram of the molten state of the thermal spray material. FIG. 4 is an explanatory diagram of the molten state of the thermal spray material in the conventional method. 1... Torch body, 2... Plasma gas passage, 3...
...Anode, 4...Cathode, 5...Sprayed material passage, 6.
... Thermal spraying material outlet, 7... Cooling water passage, 8... Laser oscillator, 9... Optical fiber, 10... Condensing lens, 11... Plasma flame, 12... Thermal spraying material, 1
3... Laser light, 14... Flying powder, 15...
Melted powder, 16... unmelted powder.

Claims (1)

[Claims] When performing thermal spraying by melting the spray material with the plasma flame generated between the anode and cathode of a plasma spray torch, the cathode is made hollow and a laser beam is guided into the hollow part from behind in the same direction as the plasma flame. A plasma spraying method characterized by heating and melting a spraying material with laser light.