JPS62282662A - Gas tunnel-type plasma thermal spraying device - Google Patents

Abstract

PURPOSE:To form a thermally sprayed film by sending a gas at a high flow rate tangentially into a cylindrical vessel to generate a high-speed vortex, forming a gas tunnel on the axis of the vessel, and effectively utilizing high- temp. and high-pressure thermally sprayed particles. CONSTITUTION:Respective electrodes are connected to a DC electric power source PS1 in a plasma jet gun A consisting of a torch center electrode 10 and a torch nozzle 2. The torch nozzle 2 using the same electrode as the gun A and a gas diverter nozzle electrode 3 are connected to a DC power source PS2 in a plasma jet generator B to generate a gas tunnel-type plasma jet 7. When the powder of ceramics, etc., is supplied from the center of the center electrode 10 of the gun A, thermally sprayed particles 8a are accelerated in the gas tunnel-type plasma jet 7 on the axis to an extremely high velocity. A high-quality thermally sprayed film having high adhesion and airtightness is thus formed.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention Unpublished II relates to a plasma spraying apparatus. The phenomenon in which a film is formed on a metal or metal object by colliding high-temperature molten particles at high speed with the object is called thermal spraying. Heat sources such as combustible gas flames, explosions, and plasma jets are used to obtain these high-temperature, high-velocity thermal spray particles, and thermal spray apparatuses using each of these are commercially available. Among them, plasma spraying using a plasma jet as a heat source! The setting is particularly suitable for producing high-temperature molten particles and for producing shells of ceramics, waxes, and inorganic materials having a high melting point.

However, with conventional plasma spraying equipment, there are various problems with the quality of the sprayed coating using particles with a high melting point such as ceramics. At present, there are problems such as poor adhesion between the skin and the 1Q substrate, and no significant improvement in quality can be expected.

The reason for this is thought to be that it is extremely difficult to supply the spray particles to the center of the plasma jet, and therefore the heat of the plasma cannot be used effectively to melt the spray particles.

However, the excellent characteristics of fine ceramics, such as heat resistance, corrosion resistance, and electromagnetic properties, allow them to meet the new demands of cutting-edge technology. Engineering/Space engineering/
The application of plasma spraying to composite (ceramics and metals) surface processing technology in harsh environments in various fields such as electronics and marine development is expected to increase significantly.

In the uninvention, the following problems can be solved by using a portex gas tunnel (or gas tunnel) to effectively reduce the Ql thermal spray particles from the plasma jet and by increasing the speed of the thermal spray particles. In addition, the second objective is to improve the quality of thermal sprayed coatings by using high-temperature thermal spraying particles by increasing the output of plasma jet using Kastunnel.

;kJj;, when a cylindrical container is tangentially filled with gas at a constant flow rate, and a high-speed vortex is generated by the action of the gas diverter nozzle, a low-pressure part (gas tunnel) is formed in the axis of the container. This is an application of the principle of The configuration of the gas tunnel type plasma jet is as follows:
d shown in FIG. One of the major differences from conventional plasma spraying equipment is that the spraying material (powder, solid cup, etc.) can be supplied from the direction of the central axis of the torch. Therefore, the heat from the plasma jet can be effectively transferred to the sprayed particles, and the sprayed particles can be produced at an ultra-high speed.

A gas tunnel (
6) In addition to gas manifestation, the shape and size of the gas diverter nozzle (3) determines its properties (pressure, area, etc.)
is determined. Therefore, in the present invention, the shape and size of the nozzle can be set in the cylinder by replacing the nozzle, so that it can immediately correspond to any experimental conditions. Furthermore, in addition to rare gases such as argon and helium, nitrogen, oxygen, air, etc. can be used as the working gas of gas tunnel 11/ (7) Raw 6, and the atmosphere can be easily changed.

Plasma jet gun torch center electrode (cathode, 1
0) The arc generated between the torch nozzle (anode, 2) is ejected from this nozzle as a plasma jet (7), but when it enters the low-pressure gas tunnel (6), it is rapidly accelerated and its length increases. Increase significantly. In addition, the high-speed thermal pinch effect of the gas diverter nozzle (3) reduces the diameter of the plasma jet but contributes to its temperature -(-H. In addition to this function, it can be used in electrodes in the present invention, and the output of the plasma jet can be significantly increased.

For this reason, when this gas tunnel type plasma jet is applied to thermal spraying, it is extremely expensive compared to conventional plasma spraying equipment. It is possible to obtain high-velocity thermal spray particles. Therefore, by using the present invention, it is possible to significantly improve the quality of the sprayed coating, and it is also possible to spray high melting point ceramics, which has been difficult to do with conventional plasma spraying equipment.

The invention will be explained in detail by means of the illustrated embodiment (FIG. 1). ■ is a plasma jet gun, which is composed of a torch center (10) and a torch nozzle (2).
Each electrode is connected to a direct current 71 [PSl. In addition, ■ is a gas tunnel type plasma jet generator, in which a DC power supply PS2 is connected between the torch nozzle (2), which shares the electrode with ■, and the gas diverter nozzle electrode (3). The supply of ceramic powder that can generate a plasma jet (7) differs from the conventional method by making a hole (hollow cathode type) in the center of the torch center electrode (10) of the plasma spraying/nod gun described in ■, and then inserting the shaft from there. Supplying direction. At this time, the ceramic spray particles (8a) supplied from the powder supply port (9) of the plasma jet gun are transferred to the gas tunnel type plasma jet (
7) It is accelerated inside and becomes very fast. At the same time, the time for heating by plasma becomes longer and the temperature becomes higher. On the other hand, unmelted thermal spray particles (8b) located away from the axis at low speed and low temperature are removed by the centrifugal force of the PIl flow.

Therefore, compared to conventional plasma spraying equipment, the width of the sprayed coating on the material under the same spraying conditions is reduced by more than 10% a, while the thickness of the sprayed coating (18) is increased by 100%. . In addition, regarding the quality of the sprayed coating, the number of pores is significantly reduced, the adhesion and airtightness at the interface are improved, and the hardness is also significantly increased.

Figure 2 shows the characteristics of the Vickers hardness (Hv) of the alumina film when the plasma spraying equipment input P (kW) was changed from 22kW to 43kW. In this case, the spraying distance was 1
00m field. When the input is 22 kW, the uniform hardness of the coating is Hv=900, so the hardness increases as the input increases, and at 43 kW't', Hv=1200 is reduced by 1. This value is the value Hv obtained with conventional thermal spray equipment.
= 800, and has good results in terms of wear resistance and the like.

Figure 3 shows the hardness characteristics of the alumina film when the spraying distance L (mm) is changed. In this case, the input power is 22kW.
It is. When the spraying distance is 100mm, Hv=900, but as the distance approaches, the hardness increases, and when the distance is 80mm
, Hv=1000 is obtained. As described above, the present invention makes it possible to thermally spray ceramics with a much smaller input (approximately 20 kW) compared to conventional plasma spraying equipment (30 kW), and it is possible to improve the quality of the thermally sprayed coating. . Further, for other types of powder (ceramics such as titania and zirconia), a high value of 200 or more in Vickers hardness can be obtained compared to the conventional skin W2 hardness. For example, for the powder of (alumina + 40% titania), Hv: 800 was obtained, whereas the conventional value was Hv = 600.

In addition, it is possible to thermally spray alumina powder with a fine particle size (5 microns or less), which has been difficult with conventional plasma spraying equipment.

Further, the present invention allows the gas tunnel generating section to be attached to a wide variety of conventional plasma spraying equipment very easily, and the same effects as described above can be obtained.

In this case, the position of the powder supply port does not matter whether it is inside or outside the electrode nozzle. An example is shown in FIG. This is a conventional plasma spray gun (internal feeding method')
A gas tunnel generator configured by (1), (2), and (3) is coaxially attached to the front surface of the anode nozzle of (17). In this case as well, thermal spray particles can be obtained at extremely high temperatures and high speeds, and the quality of the thermal spray coating can be significantly improved.

Plasma jet (7) sprayed from the thermal spray gun (17)
is accelerated in the gas tunnel (6) on the axis and at the same time is strongly constrained by the vortex flow of velocity ρ:. As a result, the diameter of the plasma jet decreases and its length increases significantly. At this time, the spray particles (8
In a), the speed becomes very high, and the heating time from the plasma becomes long, resulting in a high temperature. On the other hand, low-speed, low-temperature, unmelted thermal spray particles (8b) located away from the axis are removed by the centrifugal force of the vortex. For this reason, conventional plasma melting! )t 9 Wl, the width of the sprayed coating was greatly reduced and its thickness was significantly increased. In addition, the quality of the sprayed coating (porosity, adhesion and airtightness at the interface, hardness) is improved. In this case, an even stronger effect can be obtained by applying a high voltage between the torch nozzles (2) and (3) to make the gas tunnel type plasma jet gain over the conventional plasma torch.

As described above, in the present invention, the quality of the sprayed coating can be formed by effectively utilizing high-temperature and high-velocity spray particles, so that not only can the quality of the sprayed coating be significantly improved, but also the quality of the sprayed coating can be significantly improved. This makes it possible to thermally spray high-melting point ceramics, which was difficult to do with other methods.

Further, the production of a fine ceramic foil film according to the present invention can easily provide a new composite material with high performance that can replace fine ceramics obtained by conventional firing or the like.

Literature l) Araguchi l, Kobayashi; patent pending, 1983-132783
"High-output plasma jet generator" 2) Araguchi], Kobayashi: Kishi revision pending, 1980-23719
5r sleeve supply type dog output plasma jet generator

[Brief explanation of the drawing]

Uninvented implementation! Figure 2 shows the dependence of the Vickers hardness of the alumina film on the thermal spray plasma manual labor, and Figure 3 shows the dependence of the hardness on the spraying distance. ing. Moreover, FIG. 4 is a drawing when the present invention is applied to a conventional device. 1. Eddy current generating nozzle (1 insulation material) 2. Torch nozzle (anode) 3. Customized pattern nozzle ('iti M) 4.
Nozzle operator Lugu 5, vortex chamber 6, gas tunnel 7, plasma jet (Kast/Nel type) 8a,
Thermal sprayed particles 8b heated and accelerated Thermal sprayed particles 9 shifted from the center axis Powder supply port 10 Torch center electrode 11, Powder supply device 12, Working gas inlet 13, Insulating material 14, Attachment flange 15, Spacer (insulating material) 16, Pa/fton O-ring 17, Plasma spray can 18, Thermal spray coating 19, Material 20, Cooling gas person ``! 21, Cooling person ``J Hv, Vickers hardness P: Plasma spray equipment input (kW) L: Spraying distance M (mm)

Claims (5)

[Claims] (1) Plasma spraying equipment that uses a method of generating a gas tunnel on the axis of a spray plasma jet torch using high-speed vortices (2) The plasma spraying device according to item 1, which is capable of supplying the spraying material (powder, solid rod, etc.) from the direction of the central axis of the torch. (3) Plasma spraying equipment according to paragraphs 1 and 2, in which all kinds of gases, including chemically reactive gases, can be used as the working gas, and the atmosphere is variable. (4) Plasma spraying equipment according to items 1, 2, and 3, which uses replaceable gas diverter nozzles of various shapes as electrodes to create a high-output plasma jet. (5) A plasma spraying device in which a gas tunnel generating device having the functions of the first, second, third, and fourth items is combined with various conventional thermal spraying devices such as plasma and gas flame.