JPH0450381B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a thermal spraying method and apparatus for improving the functionality of a material surface using a laser. The apparatus of the present invention can be used for thermal spraying to improve the functionality of the surface of a material using a metal or non-metal as a thermal spraying material. Thermal spraying is a well-known technical term in which the coating material is continuously heated and melted, and then dispersed by a jet air stream to atomize and fly, spraying fine particles widely and evenly over the surface to be coated. It comes from two words: melting and jetting. <Conventional technology> In recent years, there has been a trend in material development to develop new materials that seek functionality. Not only metals, but also polymers and ceramics fall into this category. On the other hand, in terms of processing technology, from the standpoint of resource conservation, emphasis is placed on surface (treatment) processing technology that processes only the surface of the material and imparts functionality. Thermal spraying technology can be applied to various surfaces (treatments)
It has recently attracted attention as one of the simplest processing techniques. Until now, various thermal spraying methods such as gas thermal spraying, plasma thermal spraying, and wire bombardment spraying have been developed, and research is being conducted toward their practical application. However, in either method, the thermal spray materials that can be applied are limited, and the reliability of the adhesion between the sprayed film and the object to be sprayed is not sufficient. The development of thermal spraying methods and thermal spraying equipment that achieve a certain degree of adhesion will be an important future research topic. <Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a practically excellent method for easily creating a sprayed film with reliable adhesion. An object of the present invention is to provide a thermal spraying method and a thermal spraying apparatus. <Means for Solving the Problems> The laser thermal spraying method of the present invention directs the laser beam toward the surface to be thermally sprayed using a condensing lens protected by a protective gas, at a point in front of the surface to be thermally sprayed, at a distance corresponding to the spraying distance. By converging on the position, creating a high energy density area,
Continuously feeding a wire or powder of a thermal spray material sent from a separate introduction part separated from the introduction part of the protective gas for the lens to the high energy density part,
There, the gas is liquefied at high temperature one after another, and high-pressure gas is injected toward the surface to be thermally sprayed from the injection port on the outer periphery of the laser beam just before reaching the high-energy density part.
The high-temperature liquefied material is blown off in the high-energy density area, atomized, and then sprayed onto the surface to be thermally sprayed, which is heated by the laser beam that has been converged and diffused. The attachment distance was set to the distance that the atomized and flying liquefied material would reach before solidifying. In one embodiment, the spraying material is a metal, and the injection gas is appropriately reactive or non-reactive with respect to the metal, and the metal is free from oxides, nitrides, etc. due to chemical reactions in the spraying atmosphere. It is also proposed that a non-metal sprayed film can be produced. The laser thermal spraying apparatus of the present invention is a chamber that encloses the irradiation side of the laser beam condensing lens, except for the main nozzle at the beam exit that surrounds the laser beam just before the narrowed convergence part, and the connection part for introducing lens protective gas. Thermal spraying material is continuously fed from the outside of the thermal spraying tube to the sealed thermal spraying tube, a high-pressure gas nozzle opened toward the thermal spraying direction on the outer periphery of the main nozzle of the thermal spraying tube, and the laser beam converging section. feeding a lens protective gas into the thermal spray tube and causing it to flow out from the main nozzle, injecting high pressure gas from the high pressure gas nozzle to atomize and fly the thermal spray material liquefied at high temperature in the laser beam converging section; The method is characterized in that the laser beam is sprayed from the laser beam converging part onto the surface to be thermally sprayed, which is heated by the laser beam which is spread out after convergence at a distance that the atomized and flying liquefied material reaches before solidifying. . Another laser thermal spraying apparatus of the present invention is a chamber that surrounds the irradiation side of the laser beam condensing lens, and includes a main nozzle at the beam exit that surrounds the laser beam just before the narrowed convergence part, a lens protective gas connection, and A thermal spray tube that is sealed except for the powder connection, a partition wall that divides the thermal spray tube into a lens protection gas chamber and a powder supply chamber and has a laser beam passage in the center, and a main nozzle of the thermal spray tube. A high-pressure gas nozzle on the outer periphery that opens toward the thermal spraying direction, and a device that continuously feeds thermal spray material powder on a carrier gas from the powder connection section to the laser beam convergence section via the powder supply chamber. , sending a protective gas into the lens protective gas chamber from the connecting part and causing it to flow out from the main nozzle, and injecting high-pressure gas from the high-pressure gas nozzle to atomize and fly the high-temperature liquefied thermal spray material in the laser beam converging section. , the laser beam is sprayed from the laser beam converging part onto the surface to be thermally sprayed which is heated by the laser beam which is spread after convergence at a distance that the atomized and flying liquefied material reaches before solidifying. do. As an embodiment of these welding apparatuses, the thermal spraying tube may have a thermal spraying atmosphere protection tube that can be attached to and removed from the thermal spraying tube. <Function> As a result of extensive research into thermal spraying methods and thermal spraying equipment suitable for obtaining thermal sprayed films with excellent adhesion, the inventors have found that the most important thermal spraying conditions, the high temperature of the thermal spraying material, This is possible by using a laser beam that is an energy density beam, and
The inventors have discovered that by adjusting the atmosphere, it is also possible to nonmetalize metals that have been activated at high temperatures by laser, and have completed the present invention based on this knowledge. That is, the present invention converges a laser beam with a condensing lens, irradiates it onto a metal or non-metallic wire as a thermal spraying material, and melts the tip of the metal or non-metallic wire that is continuously fed. Thermal spraying powder of metal or inorganic material is fed to the convergence part of the light beam, heated, and the pressure of the gas blown toward the object to be sprayed is used to melt the wire or to heat and blow off the molten spraying powder. This makes it possible to thermally spray the surface of the object to be thermally sprayed which is heated by the laser beam that has been diffused after convergence, and to make the metal wire or metal powder non-metallic by adjusting the atmosphere, thereby making it possible to form a non-metallic thermal sprayed film. (Embodiment) FIG. 1 is an embodiment of the laser thermal spraying apparatus of the present invention, and is a schematic diagram of a dual-purpose apparatus that can use either wire or powder as the thermal spraying material. A laser beam guided from a laser generator' is converged using a condensing lens fixed to a lens holder'. The lens holder' is integrated with a thermal spraying cylinder, which will be described later, through a threaded portion, and by changing the fixed position of the lens holder, the position of the focal point of the laser beam can be moved. Since the condensing lens is fixed via an O-ring, it prevents leakage of lens protection gas, which will be described later, and protects the condensing lens from heat transmitted via the thermal spray nozzle and the like.
The thermal spray tube has a lens protective gas connection part 7a for introducing the gas coming from the lens protection gas supply device 7a', a powder and carrier gas connection part 7a for introducing the powder and its carrier gas coming from the powder supply device 7a', and a high-pressure gas supply device. The main nozzle serves as an outlet for the laser beam as well as ejects the lens protection gas, powder and its carrier gas, and the high-pressure gas nozzle ejects the high-pressure gas. 5 is partitioned by a partition wall 5a into a lens protection gas chamber 6a and a powder supply chamber 8a, and the center of the main nozzle is located on the optical axis of the condenser lens. In Figure 1, the high pressure gas nozzle is
In this example, the high-pressure gas flows along the optical axis of the laser. This is a feature of the laser thermal spraying according to the present invention that is not found in other thermal spraying methods. Instead of using this high-pressure gas nozzle, it is also possible to provide a separate nozzle outside the thermal spray nozzle and spray the gas by jetting the gas from this nozzle. The lens protective gas filling the upper part of the partition wall 5a prevents powder etc. from adhering to the lens. Outside the main nozzle, there is a wire feeding tip or powder feeding device 7 that guides the wire fed from the wire feeding device' to the laser beam.
A powder feeding nozzle 7b is provided which guides the powder sent from b' and its carrier gas to the laser beam. FIG. 1 illustrates a case in which thermal spraying is performed downward in the atmosphere using a wire feeding tip, and the object to be thermally sprayed, which will be described later, moves. The method of installing the wire feeding chip is to place the wire at the position where it is fed toward the optical axis, and the angle between the wire and the optical axis is
When spraying downward at an angle of 90 degrees or less as shown in Figure 1, it is desirable to fix the wire so that it points downward as much as possible, but the energy density when the tip of the wire is irradiated with the laser beam is It is necessary to consider parameters such as the moving speed of the object to be sprayed, the thickness of the sprayed film, the wire feeding speed, and the diameter of the wire, and fix the wire feeding tip according to the spraying conditions. There is a need. Regarding the installation of the powder feeding nozzle 7b when using powder without using a wire,
The installation method is the same as the wire feeding tip. The principle of thermal spraying using a wire is that the tip of the wire is heated and melted by a laser beam converging with high energy density, and then the gas ejected from a high-pressure gas nozzle sprays droplets toward the object to be sprayed. , to obtain a sprayed film. The wire that is blown away as droplets is continuously replenished from the wire feeder'.
By changing the moving speed of the object to be sprayed, etc., a sprayed film of arbitrary thickness can be obtained. The energy density of the laser beam that reaches the object to be thermally sprayed can be adjusted arbitrarily by changing the distance between the main nozzle and the object to be thermally sprayed, and the laser output. It is also possible to increase the degree of adhesion between the object and the sprayed film. If a metal is used as the wire and an inert gas such as argon is used as the lens protection gas and high pressure gas, a metal sprayed film with the same composition as the wire can be obtained.If oxygen, nitrogen, etc. are used instead of the inert gas, a sprayed metal film can be obtained. Since the molten metal reacts with oxygen, nitrogen, etc. to produce compounds, a sprayed film having a composition of oxides, nitrides, etc. of the metals can be obtained. If the thermal spraying device is installed in an atmosphere chamber and thermal spraying is performed in an inert atmosphere or nitrogen atmosphere, the thermal spraying of metal or its metal nitride will be completed. The principle of the thermal spraying method using powder is the same as that using a wire, but the powder can be fed from the powder feeding nozzle 7b and from the powder connecting part 7a provided on the thermal spray tube, either simultaneously or independently. can be done. The carrier gas for powder feeding is the same as the high pressure gas. As the powder, both metal powder and non-metal powder can be used, and it is also possible to obtain a non-metal (oxide, nitride, etc.) sprayed film using metal powder by the method described above. In addition, when the thermal spraying material is fed only from the outside of the thermal spraying tube, the powder connection part 7a, the partition wall 5a, and the powder supply chamber 8a may be omitted. FIG. 2 is an example of a thermal spraying atmosphere protection tube attached to the tip of a thermal spraying nozzle, which is adapted to thermal spraying using a simple flat wire. During thermal spraying, most of the air in the thermal spray atmosphere protection tube can be exhausted by using the same types of gases as the lens protective gas and high-pressure gas and blowing out these gases just before thermal spraying. FIG. 3 is an example of thermal spraying using wire and powder simultaneously in the atmosphere. Next, an example of experimental data is shown. The base material refers to the material to be thermally sprayed.

【table】

[Table] In terms of thermal spraying technology, high-temperature liquefied thermal spraying material is atomized evenly in a mist-like manner using a propellant gas and then blown away.
It is important to weld the particles to the sprayed surface, and figures 4 to 6 show the conditions for uniform atomization. Fourth
The figure shows the range of conditions for uniform atomization (curve) when the pure titanium wire shown in the table above is thermally sprayed using argon high-pressure gas, with laser outputs of 3Kw and 4Kw, and the wire feed speed on the horizontal axis and the high-pressure gas pressure on the vertical axis. upper side). FIG. 5 similarly shows the respective regions of laser outputs 2, 3, and 4 when a titanium wire is thermally sprayed with nitrogen gas. Figure 6 shows the case of thermal spraying using oxygen gas, and in this case, the laser output is 2~
This shows that even if it changes to 4Kw, it will be in the same area. <Effects of the Invention> The present invention has demonstrated for the first time in the world that industrial thermal spraying using a laser is possible. The high energy density part of the laser converged by a condensing lens makes it easier and more accurate to control the temperature and area compared to the heat source of conventional gas spraying and plasma spraying.
Maximizes instantaneous heating power. Because of this high instantaneous heating power, the viscosity of the liquefied portion of the material is low, resulting in a more homogeneous spray with fewer waves than in any conventional thermal spraying method. Since the surface to be thermally sprayed is also heated by the convergent and then diffused laser beam, the thermally sprayed material is completely welded. The present invention also opens the door to utilizing chemical reactions during the spray flight by appropriately selecting the spray material and the propellant gas. The thermal spraying apparatus of the present invention injects a protective gas in front of the lens and blows it out together with the laser beam from the outlet of the thermal spray tube as the most effective and reliable means of preventing the laser beam focusing lens from being exposed to high heat and adhesion of molten particles. I succeeded with a simple configuration. In other thermal spraying equipment, when sending powder material to a high energy density area via a thermal spraying tube, the thermal spraying tube is divided into a lens protection gas chamber and a powder supply chamber, separated by a partition wall to ensure lens protection. .

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a thermal spraying apparatus using a laser according to the present invention, and FIG. 2 is a schematic explanatory diagram of a thermal spraying apparatus that enables thermal spraying on a simple plane in a variable atmosphere. FIG. 3 is a schematic illustration of thermal spraying using wire and powder simultaneously in the atmosphere. Figures 4, 5, and 6 are diagrams showing conditions for uniform atomization when the same pure titanium wire is thermally sprayed by changing the high-pressure gas to argon, nitrogen, and oxygen, respectively. In the drawings, denotes a laser beam, a condensing lens, 'a lens holder, a thermal spray tube, a connection part for lens protection gas, 7a a connection part for powder and its carrier gas, a connection part for high pressure gas,
is the main nozzle, is the high-pressure gas nozzle, is the wire feeding nozzle, and is the thermal spray atmosphere protection tube.

Claims (1)

[Claims] 1. Laser beams directed toward the surface to be thermally sprayed are converged at a position in front of the surface to be thermally sprayed and separated by the spraying distance using a condensing lens protected by a protective gas, thereby converging the laser beam toward a high energy density area. A wire or powder of thermal spray material is continuously fed from a separate introduction section separated from the introduction section for the lens protective gas to the high energy density section, where it is liquefied at a high temperature one after another. , A high-pressure gas is injected toward the sprayed surface from an injection port on the outer periphery of the laser beam just before it reaches the high-energy density part, and the material liquefied at high temperature in the high-energy density part is blown away and atomized into flight. hand,
Spray onto the surface to be thermally sprayed which is heated by the laser beam that is diffused after convergence, and set the spraying distance from the high energy density part to the surface to be thermally sprayed to the distance that the atomized and flying liquefied material reaches before solidifying. A laser spraying method characterized by the following. 2. The laser thermal spraying method according to claim 1, wherein the thermal spraying material is a metal, and the injection gas is appropriately reactive or non-reactive with respect to the metal. 3. The laser thermal spraying method according to claim 2, wherein the thermal spraying material is a metal, and the metal can form a non-metal sprayed film such as an oxide or nitride through a chemical reaction in the thermal spraying atmosphere. 4 A chamber that encloses the irradiation side of the laser beam condensing lens, and is sealed except for the main nozzle at the light exit that surrounds the laser beam just before the narrowed converging part, the lens protective gas connection, and the powder supply connection. a partition wall having a laser beam passage in the center, which divides the thermal spraying tube into two into a lens protection gas chamber and a powder supply chamber; The high-pressure gas nozzle opened at
a device for continuously feeding the thermal spray material powder on a carrier gas to the laser beam converging section; and a device for continuously feeding the thermal spraying material from the outside of the thermal spray tube to the laser beam converging section; A protective gas is sent into the chamber from the connection part and flows out from the main nozzle, and high-pressure gas is injected from the high-pressure gas nozzle to atomize and fly the high-temperature liquefied thermal spray material in the laser beam convergence section, thereby converging the laser beam. A laser thermal spraying device is characterized in that the sprayed surface is heated by a laser beam that is diffused after converging at a distance that the atomized liquefied material reaches before solidifying. 5. The laser thermal spraying apparatus according to claim 4, wherein the thermal spraying cylinder has a thermal spraying atmosphere protection cylinder which is detachable.