JPH02290959A - Plasma spraying device - Google Patents

Abstract

PURPOSE:To effectively carry out plasma spraying by observing the density of the particles of thermal spraying material passing through plasma with a laser beam and providing a means for determining the optimum amt. of a carrier gas using the observed value. CONSTITUTION:The diameter of a laser beam 26 is increased by a laser beam expanding device of convex lenses 21 and 22, and a plasma jet 15 is irradiated with the laser beam 26. The beam 26 is controlled by a condensing device 23, the scattered light is cut at the focus point by an aperture 24, and the light intensity is measured by a light receiving sensor 25. The light intensity is attenuated when the thermal spraying material 18 flies in the plasma jet 15. The attenuation factor is measured by the sensor 25 and stored in a signal intake device 27. The signal is then transformed in an Abelian transformer 29 to clear the number distribution density of the particles of the material 18 in the plasma jet 15. The amt. of the carrier gas for the material is controlled using the result, and the number density of the particles of the material flying in the plasma jet 15 is maximized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention observes the particle number density distribution of the sprayed material in the plasma jet, and adjusts the amount of carrier gas of the sprayed material so that the sprayed material is concentrated in the center of the plasma jet. The present invention relates to a plasma spraying device that controls.

[Prior Art] Generally, plasma spraying is known as a method for coating metal, ceramic, or cermet to give wear resistance, heat resistance, and corrosion resistance to the surface of component materials, and is described in "Industrial Heating J Vol. 25 , No. 5, P8 to P14. Plasma spraying is usually carried out in the manner described later using the apparatus configuration shown in Fig. 5. In Fig. 5, 1 indicates plasma spraying. The gun body is mainly composed of a cathode (hereinafter referred to as a tungsten electrode) 2, an anode (hereinafter referred to as a water-cooled copper electrode) 3, a plasma gas supply port 4, and thermal spray material supply ports 5 and 6.The tungsten electrode 2 and The water-cooled copper electrode 3 is electrically separated by an insulator 7, and the tungsten electrode 2 is connected to the negative electrode of a DC power source 8, and the water-cooled copper electrode 3 is connected to the positive electrode. 9 is a plasma gas (usually argon, helium , hydrogen, nitrogen, etc.) and supplies it to the plasma gas supply port. 10 and 12 are airtight hoppers for storing thermal spraying materials, and 1l and 13 are gas cylinders for storing thermal spraying materials, respectively. This is a carrier gas (Ar, etc.) cylinder for supplying to the port 5.6.

In the apparatus described in (d), first, plasma gas is supplied from the plasma gas cylinder 9 through the plasma gas supply port 4, and a plasma arc is generated between the tungsten electric V52 and the water-cooled copper electric cell 3 by the DC power supply 8. Through heat exchange between this arc and the plasma gas, it becomes Plasma Ciet 15, a plasma spray gun! Spray more. Base material to be sprayed 1
In step 4, the sprayed surface is subjected to blasting or the like in advance, and then installed at a predetermined position. Thereafter, the thermal spraying material in the hoppers 10, 12 is transferred from the thermal spraying material supply ports 5, 6 to the conveying gas cylinders 11, 13.
The gas is supplied to the plasma jet 15 and sprayed onto the base material I4 to be thermally sprayed to form a thermally sprayed coating 19.

In order to achieve satisfactory thermal spray coating quality,
It is necessary for the thermal spraying material introduced from the thermal spraying material supply ports 5 and 6 to fly through the center of the plasma jet and to have enough time to melt. This is because the temperature of the plasma jet decreases rapidly toward the periphery of the plasma jet.
- This is because the thermal spray material flying in the peripheral area cannot be melted within the time it takes to reach the base material to be sprayed, and is deposited unmelted on the base material to be sprayed, degrading the quality of the coating.

Further, the flow rate of the plasma gas used for thermal spraying, the mixing ratio of argon and helium or argon and hydrogen used in the plasma gas, and the input power differ depending on the thermal spraying material. This is because the density and speed of the plasma jet differ, so the way the sprayed material enters will also differ depending on each condition. Therefore, if the amount of carrier gas is too large, the sprayed material will pass through the plasma jet, and if it is too small, it will not be able to enter the plasma jet and will be repelled.

Therefore, up until now, the amount of carrier gas for the thermal spraying material has been varied based on experience in accordance with the conditions of the plasma gas flow rate, mixing ratio, and input power, which differ for each thermal spraying material, and in relation to the quality of the thermally sprayed coating. The optimum amount of carrier gas was determined. In order to determine the optimum amount of carrier gas, sample spraying was required several times, and the coating shape and coating quality were inspected after each sample spraying.

[Problems to be Solved by the Invention] In the above-mentioned thermal spraying method, each time a sample is sprayed to determine the optimum amount of carrier gas, the process from preparing the base material to be sprayed to inspecting the shape of the sprayed target and the coating quality after thermal spraying is carried out. It will take several days to complete the process. Therefore, there is a problem in that the labor and cost required for sample thermal spraying, which is performed several times before actual thermal spraying, becomes large.

It is an object of the present invention to solve these problems and provide an apparatus that can perform plasma spraying extremely efficiently and at low cost.

[Means for Solving the Problems] In order to achieve the above object, the present invention is constructed as follows. That is, 1. In a thermal spraying device that injects thermal spraying material into the plasma jet using a carrier gas, and then laminates the thermal spraying material melted by the heat of the plasma on the surface of the base material, a laser oscillator is installed on one side facing the plasma jet. and a laser beam expanding device, and on the opposite side, a laser beam focusing device, an aperture at its focal position, a light receiving sensor behind the aperture, and a signal acquisition device and an Abelian conversion device. Plasma spray equipment.

2. In a thermal spraying device that injects thermal spraying material using a carrier gas during a plasma jet and laminates the thermal spraying material melted by the heat of the plasma on the surface of a base material, a laser oscillator is installed on one side facing the plasma jet, laser beam expander,
A half mirror is installed, and a total reflection mirror is installed on the opposite side.
A laser beam focusing device is provided at the passing position of the laser beam that is reflected by the total reflection mirror and then bent by the half mirror, an aperture is provided at the focal point of the laser beam, and a light receiving sensor is provided behind the aperture, as well as a signal acquisition device and an Abelian transformer. A plasma spraying device characterized by being equipped with a device.

3. Using the observed particle density distribution of the sprayed material in a thermal spraying device that injects the sprayed material with a carrier gas during a plasma jet and laminates the sprayed material melted by the heat of the plasma on the surface of the base material, 3. The plasma spraying apparatus according to item 1 or 2 above, further comprising a control device for controlling the amount of carrier gas for the thermal spraying material at node A.

It is.

[Sakukawa] Therefore, the operation of the present invention will be explained using FIGS. 1 and 2. That is, the laser beam 26 generated by the laser oscillator 20 is expanded in its direct meridian by a laser beam expansion device while remaining parallel, and then irradiated onto the plasma jet.

The laser beam that has passed through the plasma jet is transmitted either as it is or after being reflected by the total reflection mirror 30 and the half mirror 3l, it is focused by a laser beam focusing device, and is scattered by an aperture 24 installed at the focal point position, which causes measurement errors. The light is cut off, and the light intensity is measured by the light receiving sensor 25. When the thermal spray material X8 is flying in the plasma jet 15, the laser beam 15 is blocked by the thermal spray material and its light intensity is attenuated. This attenuation rate is measured by the light receiving sensor 25, stored in the signal acquisition device 27, and then subjected to Abelian transformation in the Abelian transformation device 29, thereby clarifying the particle number density distribution of the sprayed material in the plasma jet. Using the results, the amount of carrier gas for the sprayed material is controlled so that the particle number density distribution of the sprayed material is maximized at the center of the plasma jet. Alternatively, the amount of carrier gas is controlled by a combination of the control device 28 and the flow control valves 16 and 17 so that the particle number density of the sprayed material in the central portion of the plasma jet is maximized.

[Example] An example of implementation of the present invention will be described below based on the drawings.

In FIG. 1, a laser beam 26 emitted from a laser oscillator 20 is expanded in diameter to a diameter greater than the cross-sectional area of the plasma jet while remaining a parallel beam by a laser beam expansion device that combines a convex lens 21 and a convex lens 22. Here, the laser oscillator 20 may be continuous oscillation or pulse oscillation. Further, the laser beam enlarging device may be a single lens, a single mirror, or a combination thereof, as long as the diameter of the parallel beam is expanded to be larger than the cross-sectional diameter of the plasma jet. For example, if the average cross-sectional area of the plasma jet is 20+++ m, the diameter of the laser beam is 30 m, so that measurements can be made even if the cross-sectional area varies.
m or more is desirable.

The expanded laser beam passes through the plasma jet 15 and is focused by a convex lens 23, which is a laser beam focusing device. The laser beam focusing device may be a single lens, a single mirror, or a combination thereof. At the focal position of the convex lens 23, a laser beam 26 made of thermal spray material is placed.
An aperture 24 is installed to block the scattered light from affecting the measured values. Here, the aperture 24 is a thin metal plate with a matte black surface and a via hole with a diameter of about 1 mm in the center. Abacha-2
The intensity of the laser beam that has passed through the sensor 4 is converted into an electrical signal by the light receiving sensor 25 and stored in the signal acquisition device 27. This light receiving sensor 25 may be of any type as long as it converts light intensity into an electrical signal.

When the thermal spray material 1B is introduced into the plasma jet 15, the thermal spray material 18 blocks light and the laser beam intensity is attenuated. Since the amount of attenuation is correlated with the density of the sprayed material and the distance traveled, the longer the laser beam passes through a place where the density of the sprayed material is high, the greater the attenuation rate of the laser light intensity becomes. FIG. 3(b) shows the measurement results before and after introducing the thermal spray material 18 into the plasma jet 15. Using the measured attenuation rate of the laser light intensity, the Abelian transformation device 29 converts the observed quantity 1 (when a certain physical quantity ε(r) has rotational symmetry and is a function of only the radius r, y
) to obtain the original ε('), the particle number density distribution of the thermal spray material as shown in FIG. 4 is obtained. Using this result, the amount of carrier gas is manually adjusted so that the particle number density at the center of the plasma jet is maximized. Alternatively, this result is taken into the control device 28 and the flow control valve 1
6. The amount of carrier gas is adjusted by issuing an opening/closing signal to 17, and the particle number density in the central part of the plasma is controlled to be maximum.

As a method of irradiating the plasma jet laser beam, a method using a total reflection mirror 30 and a half mirror 3l, as shown in FIG. 2, may be used. Specifically, the laser beam 26 emitted from the laser oscillator 20 passes through the convex lens 2I.
A laser beam expanding device that combines a convex lens 22 and a laser beam enlarges the diameter of the collimated light to be larger than the absolute volume of the plasma jet, transmits through the half mirror 31, irradiates the plasma jet 15, and then faces the plasma jet. After being reflected by the placed total reflection mirror, it is further reflected by a half mirror, and focused by a convex lens 23, which is a laser beam focusing device. Here, when a half mirror is irradiated with light, half of the amount of light is reflected by the irradiated surface and the remaining half is transmitted through the irradiated surface.

An aperture 24 is installed at the focal point of the convex lens 23, and the intensity of the laser beam passing through the aperture 24 is converted into an electrical signal by a light receiving sensor 25 and stored in a No. 8 intake device 27. The stored signal is Abelian transformed in an Abelian transformation device 29 to obtain a particle number density distribution of the thermal spray material. Using this result, the amount of carrier gas is manually adjusted to maximize the particle number density in the center of the plasma jet. Or import this result into the control device 28,
Flow control valve +6. The amount of carrier gas is adjusted by sending an opening/closing signal to l7, and the particle number density in the central part of the plasma is controlled to be maximum.

[Effects of the Invention] Due to the configuration of the present invention as explained above, it has become possible to observe the particle density of the thermal spray material flying in the plasma and determine the optimum amount of carrier gas using that value. . This eliminated the need to prepare the sprayed base material for sample thermal spraying and inspect the coating shape and quality after thermal spraying, which had previously been done several times, resulting in cost and labor savings.

[Brief explanation of drawings]

FIGS. 1 and 2 show an embodiment of the present invention. Figure 3 (a
) is a plan view of the measurement system, and (b) is the measurement result. FIG. 4 is a graph showing the particle number density distribution calculated by Abelian transformation. FIG. 5 is a diagram illustrating the conventional plasma spraying method. 1... thermal spray gun, 2... tungsten electrode, 3...
・Water-cooled copper electrode, 4... Plasma gas supply port, 5, 6.
... Thermal spray material supply port, 7... Insulator, 8... DC power supply, 9... To plasma gas bomb, 10. 12...
Thermal spray material popper 11, +3... Carrier gas cylinder, 1
4... Base material to be thermally sprayed, 15... Plasma jet, 1
6. 17...Flow control valve, 18...Thermal spray material, 19.
...Thermal spray coating, 2o...Laser oscillator, 2+, 22.
23... Lens, 24... Aperture, 25...
・Light receiving sensor, 26... Laser beam, 27...
Signal acquisition device, 28... Control device, 29... Abelian conversion device, 3o... Total reflection mirror, 31... Half mirror

Claims (1)

[Claims] 1. In a thermal spraying device that injects thermal spraying material into a plasma jet using a carrier gas, and then laminates the thermal spraying material melted by the heat of the plasma on the surface of a base material, a device facing the plasma jet is used. A laser oscillator and a laser beam expansion device are installed on one side, and a laser beam focusing device and an aperture at its focal position and a light receiving sensor are installed behind the aperture on the other side, as well as a signal acquisition device and an Abelian transformation device. A plasma spraying device characterized by: 2. In a thermal spraying device that injects thermal spraying material using a carrier gas into a plasma jet and then laminates the thermal spraying material, which is melted by the heat of the plasma, on the surface of the base material, a laser beam is installed on one side facing the plasma jet. Oscillator, laser beam expander,
A half mirror is installed, and a total reflection mirror is installed on the opposite side.
A laser beam focusing device is provided at the passing position of the laser beam that is reflected by the total reflection mirror and then bent by the half mirror, an aperture is provided at the focal point of the laser beam, and a light receiving sensor is provided behind the aperture, as well as a signal acquisition device and an Abelian transformer. A plasma spraying device characterized by being equipped with a device. 3. Using the observed particle density distribution of the sprayed material in a thermal spraying device that injects the sprayed material with a carrier gas into a plasma jet and then layers the sprayed material, which is melted by the heat of the plasma, on the surface of the base material. 3. The plasma spraying apparatus according to claim 1, further comprising a control device for adjusting the amount of carrier gas for the spraying material.