JPH05125557A - Coating method using laser beam - Google Patents

Abstract

PURPOSE:To coat a member by the laser build-up welding by irradiating a coating material with an introduced laser beam, scanning the coating surface and melting the coating material. CONSTITUTION:A powder or foil coating material C is arranged on the surface of a member W to be coated, and the member W is set in a vacuum chamber 1 under vacuum. The gap between a condensing optical system 3 (laser irradiation head) and the surface to be coated is evacuated by using a suction nozzle 4, a suction hose 9 and a vacuum pump 7, and the material C is irradiated with the laser beam introduced by an optical fiber 8 and the optical system 3. The surface to be coated is scanned by the laser beam to melt the material C, and the surface is coated. The surface can be build-up welded regardless of its size of area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a base material surface of a product requiring abrasion resistance or corrosion resistance with a laser or a ceramic or a hard metal.

[0002]

2. Description of the Related Art In recent years, in accordance with the complexity of various machines and the diversification of usage environment, compounding with materials having various functions has been carried out. A method of coating a material base material surface with a material having matching properties is generally used. Among the coating methods, the method of melting the coating material and depositing it on the surface of the base material by welding tends to obtain a metallurgical bond between the coating material and the base material. In particular, welding using laser or welding build-up has the advantage that welding build-up can also be performed on electrical insulators, such as ceramics, which cannot be welded by arc welding or electron beam welding.

As a conventional coating method using laser welding, there is a coating method using a carbon dioxide laser which can easily generate high energy in the apparatus shown in FIG. The laser processing apparatus shown in FIG. 4 is composed of a combination of an optical device and a vacuum chamber accommodating a workpiece. The optical device 20 includes an oscillator 11 and an optical system (laser irradiation head) 12 that collects laser light oscillated from the oscillator 11.
It consists of and. The focused laser light is shown at 13. On the other hand, a mounting table 15 is disposed in the vacuum chamber 14, and a base material 16 as a member to be coated is mounted on the mounting table 15 with its coating surface facing upward. The coating material 17 is spread almost uniformly on the top. A window 18 made of a glass material such as quartz is provided on the upper surface of the vacuum chamber 14 for introducing the laser light 13.

When the coating material 17 is irradiated with the laser light 13 condensed by the condensing optical system 12 through the window 18 in the laser processing apparatus having the above structure, the coating material 17 is melted and the base material 16 It is coated on the coating surface. In FIG. 4, 19 is an xy moving machine that moves the vacuum chamber 14, and can move the vacuum chamber 14 when the laser beam 13 needs to scan a wide coating surface.

[0005]

However, when a large member, that is, a large area to be coated, is coated with the apparatus shown in FIG. 4, there are the following problems. That is, when the laser light 13 oscillated from the oscillator 11 is guided into the vacuum chamber 14 through the glass window 18, the area of the glass window 18 needs to be almost the same as the coating area, but from the viewpoint of the strength of the glass, the window 18 is required. There is a limit to how large.
For example, when quartz glass, which is the most suitable material for the window glass from the viewpoint of strength and laser beam transparency, is used, even if the window is about 30 cm × 30 cm, the thickness is 30 m.
It must be more than m, but with such a thickness,
There is a limit from the focal length of the optical system. Further, since the member 16 to be coated is moved while being housed in the vacuum chamber 14, the chamber 14 must be made larger according to the size of the member 16 to be coated. It becomes heavy and unrealistic.

Instead of moving the vacuum chamber 14,
It is considered that the optical device 10 is moved to perform scanning, but the member 16 to be coated has a size of 30 cm × 30 cm.
If the size exceeds a certain level, the mechanism for scanning the optical device 10 becomes large-scale and not industrial. Further, instead of moving the vacuum chamber 14, it is conceivable that the mounting table 15 provided in the vacuum chamber 14 is used as a movable table and the member 16 to be coated is attached to the movable table and moved. However, even in this case, the moving distance of the member 16 to be coated increases with the coating area, and the size of the vacuum chamber 14 needs to be twice the moving distance. There is a problem that a large-capacity vacuum exhaust system is required as the vacuum chamber becomes larger.

Further, the laser welding build-up can be carried out in the atmosphere, but if it is carried out in the atmosphere, air is entrained or adsorbed gas generated from the member to be coated causes
Pore-like defects such as blowholes are likely to occur in the coating layer. If it is done under vacuum, of course, air entrapment,
Since it is easy to remove the adsorbed gas, the number of pore-like defects may be small, and even if some pore-like defects occur, most of the defects are so-called closed pores that do not communicate with the surface.
There is no problem when used as it is, and there is no problem when pores appear on the surface by finishing the coated surface by cutting or grinding. Therefore, when coating with a laser, it is desirable to perform the coating in a vacuum, but in the apparatus shown in FIG. 4, the temperature of the window 18 rises because the laser light 13 irradiates the object to be coated through the window 18 for a long time. To do. Therefore,
When the irradiation time becomes long, it is necessary to cool the window 18. Further, there is also a problem that the glass of the window 18 is soiled by the scattered particles generated from the melting portion of the member to be coated.

The present invention has been made in view of the above circumstances. A first object of the present invention is to obtain a beautiful coating layer with few pore defects regardless of the size of the coating area. It is to provide a coating method. A second object is to provide a coating method which is free from pore defects and can obtain an extremely dense coating layer.

[0009]

According to a coating method using a laser of the present invention, a member to be coated having a powdery or foil-shaped coating material disposed on a coating surface is set under vacuum, and the member under vacuum is collected. While evacuating between the optical optical system and the coating surface, irradiating the coating material with laser light introduced by an optical fiber and the condensing optical system, and scanning the laser light on the coating surface, The coating surface is coated while melting the coating material.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an embodiment of a laser processing apparatus for carrying out the coating method of the present invention, and FIG. 2 is an enlarged view of the vicinity of the coating portion of FIG. In FIG. 1, reference numeral 1 denotes a vacuum chamber having a space inside which is evacuated to a predetermined degree of vacuum and having a transparent glass window 1a on its side wall. In the vacuum chamber 1, a base material W which is a member to be coated is provided.
A fixed base 2 for fixedly supporting the
That is, the laser irradiation head 3 and the suction nozzle 4 are connected to the base material W.
A triaxial slider device 5 for positioning and moving is arranged.

The triaxial slider device 5, as shown in FIG.
A front-rear moving slider 5 that is moved on a rail 5a installed on the bottom of the vacuum chamber 1 in a direction perpendicular to the plane of the drawing.
b, a vertical movement slider 5 which is moved in the vertical direction in the drawing along a support shaft vertically provided on the longitudinal movement slider 5b.
c, a horizontal movement slider 5d attached to the vertical movement slider 5c and moved in the left-right direction in the figure, and arranged outside the vacuum chamber 1 for driving and controlling the sliders 5b, 5c, 5d. The control operation device does not. A laser irradiation head 3 and a suction nozzle 4 for sucking scattered particles generated from a molten portion of the base material W at the time of processing, which will be described later, are attached to the tip portion of the left and right moving slider 5d as shown in the figure. ..

Outside the vacuum chamber 1, a YAG laser oscillator 6 for oscillating YAG laser light and a vacuum pump 7 are provided.
And are arranged. Then, the YAG laser light emitted from the YAG laser oscillator 6 is guided to the laser irradiation head 3 in the vacuum chamber 1 by the silica optical fiber 8, and the suction nozzle 4 in the vacuum chamber 1 passes through the suction hose 9. And is connected to the vacuum pump 7.

As shown in FIG. 2, the laser irradiation head 3 has a bottomed cylindrical head body 3a having an opening on the lower side and a focusing lens (condensing lens) 3b mounted inside the head body 3a.
The output end of the optical fiber 8 is connected to the upper surface of the head main body 3a, and is attached to the tip of the left and right moving slider 5d by a mounting bracket (not shown).

The head body 3a of the laser irradiation head 3
2, a suction tube to which a suction hose 9 is connected is provided on the side surface, and a cylindrical outer cylinder 4a having an upper end peripheral portion protruding inward from the upper end, and an outer cylinder 4a. A suction nozzle 4 having an inner cylindrical body 4b, which is provided on the inner side of the inner cylindrical body 4b and whose upper end is joined to the upper end peripheral portion of the outer cylindrical body 4a and whose diameter is reduced toward the distal end side, is attached.

Next, a method of coating using the laser processing apparatus having the above structure will be described. The member to be coated, that is, the base material W, which can utilize the method of the present invention includes, for example, refractory metals such as steel, aluminum, copper, titanium and molybdenum, or ceramics such as alumina.

The coating material C is placed on the surface of the base material W to be coated. As the coating material C, powder or foil having a thickness of about 200 to 300 μm is used. The material of the coating material C is the base material W
It is appropriately selected depending on the characteristics to be imparted to. For example, ceramics are used when heat resistance or corrosion resistance is desired. In addition, stellite, cemented carbide, T
Alloys and metals used for hard facing such as iC-Ni; ceramics such as alumina; and metals in which ceramics are dispersed are also used as the coating material.

As a method for disposing the coating material C on the coating surface of the base material W, the coating material C may be simply sprinkled on the coating surface, but it is temporarily fixed to the base material W with an organic adhesive. Preferably. As a temporary fixing method, for example, a coating material mixed with an adhesive to form a paste is applied to the coated surface, or the adhesive is applied to the coated surface in advance and then the coating material is sprayed. There is a method.

Base material W on which the coating material C is arranged
Is placed on the fixed base 2 in the vacuum chamber 1 of the laser processing apparatus shown in FIG. Then, the inside of the vacuum chamber 1 is evacuated by a vacuum pump (not shown). When the inside of the vacuum chamber 1 reaches a predetermined degree of vacuum, the YAG laser light LB emitted from the YAG laser oscillator 6 is guided to the laser irradiation head 3 by the optical fiber 8 and is applied to the coating material C on the base material W. When the coating area is large, the laser irradiation head 3 is held on the triaxial slider device 5 on the coating surface for scanning. In FIG. 1 and FIG. 2, the coating layer C and the coating material C melted and piled up on the base material W are shown by C '. During the laser irradiation and scanning, the coating surface and the laser irradiation head 3 are evacuated all the time.

The conditions of laser irradiation in the above coating method, that is, the focal position of laser light, irradiation power, scanning speed, scanning interval, etc.
It is appropriately selected depending on the type of coating material. For example, when a YAG laser is used as the laser light, the focus position of the laser light is ± 1 mm from the surface of the base material, the irradiation power is 100 to 500 W, the scan speed corresponding to this power is 1 to 20 mm / sec, and the scan interval is 0.5 to 1.5 mm is the standard condition.

As described above, in the coating method of the present invention, since laser irradiation is not performed through the glass window as in the conventional case, it is not necessary to prepare a glass window according to the size of the coating area. Therefore, since the conventional problem associated with scanning the laser irradiation head according to the size of the coating area does not occur, welding overlay using a laser is possible regardless of the size of the coating area.

Further, in the coating method of the present invention, since the coating surface and the laser irradiation head are continuously evacuated during the irradiation of the laser beam LB, the particles scattered from the molten portion of the base material W are heated by the laser irradiation. Even if M is generated or a gaseous substance or mist is generated from the organic substance contained in the adhesive used for temporary fixing, these are exhausted to the outside of the vacuum system by the suction nozzle 4. Therefore, the scattered particles M generated
Since the lens 3b and the like provided inside the laser irradiation head 3 are not contaminated by the mist or the like, the laser light can be continuously irradiated.

Although the base material used in the apparatus of FIG. 1 was plate-shaped, the coating method of the present invention can also be used to coat columnar members. When coating on a cylindrical base material,
As shown in FIG. 3, the base material W wound with the coating material C is attached and fixed to a rotary jig (not shown), and the base material W is rotated while the laser irradiation head 3 is mounted on the axis of the base material W. Scan in the direction. In FIG. 3, reference numeral 10 indicates a trace of the laser beam LB scanned. When the cylindrical base material W is used, it is preferable to temporarily fix the coating material C to the coating surface with an adhesive or the like.

The base material (hereinafter referred to as a coating member) on which the coating layer C'is formed in this manner is compared with a coating member obtained by laser welding deposition or welding deposition by another method in the atmosphere. In addition, there are few pore-like defects such as blowholes. However, by the above method, even if a coating member with few pore-like defects is obtained, by slightly finishing the coating surface by cutting or grinding, the slightly contained pore-like defects appear on the surface, It may not be usable. In such a case, it is preferable to apply HIP treatment to the obtained coated member. That is, the obtained coating member was placed in a HIP device and exposed to a high temperature equal to or higher than the recrystallization temperature of the base material or the coating material for a predetermined time in an atmosphere of an inert gas such as high-pressure argon, so that the coating member remained immediately after coating. Defects can be removed. It should be noted that, in a coating member in which pore-like defects are connected to the surface in the coating layer, the defects cannot be crushed and removed even by the gas pressure. Therefore, it is preferable to reduce such defects during welding build-up.

In the case where HIP treatment is performed after coating, when a metal foil having a thickness of 10 μm or more and having no pore defects is used as the coating material, the metal foil as the coating material is not necessarily welded on the entire coating surface. May be. For example, if only the outer peripheral surface of the foil is welded and the base material and the foil are kept vacuum and airtight from the outside, they are finally joined on the entire coating surface in the HIP processing step. Therefore, unless it is necessary to form the entire coated surface with the texture produced by welding,
You may HIP the coating member which welded only the outer peripheral surface.

[Specific Example] Example 1; 100 mm × 200 mm × 15 m as a base material
m SS steel plate, WC-1 as coating material
Cemented carbide powder of 0% Co was used. One side of the base material is ground, and a coating material having a thickness of 0.5 to 1.
It was sprayed to 0 mm and set in the YAG laser processing apparatus shown in FIG. About 0.01 To in the vacuum chamber
After evacuating to rr, a YAG pulse laser of about 200 W was scanned at 2 mm / sec and a scan interval of 1 mm to scan an area of 80 × 180 mm while further evacuating from a suction nozzle attached below the laser irradiation head.
The obtained coating member was cut, and its cross section was ground and polished to examine the presence or absence of pore-like defects, and it was found that minute holes of 5 μm or less were scattered, which is good as a weld overlay of this kind. Met.

Example 2; 60 × 60 × 2.5 as a base material
A mm2 molybdenum plate was used, and alumina powder (average particle size: 0.5 μm) having a purity of 99.9% was used as a coating material. The coating material was dispersed in a pressure-sensitive adhesive prepared by dissolving methyl cellulose in isopropanol, and then placed on one surface of the base material by brushing. After drying the applied adhesive mixture coating material,
It was set in the YAG laser processing apparatus shown in (1) and coated in the same manner as in Example 1.

Since the coefficient of expansion of molybdenum was not so different from that of alumina, the coating member obtained did not have a large warp. In addition, cross-sectional observation of the pore state of the coating layer revealed that there were slight pores of 10 μm or less, but it was very beautiful as a whole.

Example 3 As a base material, an outer diameter of 20 mm finished by cutting to a surface roughness Rmax of 1.8 μm or less
The S45C steel rod of was used. Amorphous soft magnetic material foil 26 having a width of 15 mm and a thickness of 30 μm as a coating material
05-S2 (manufactured by Allied Corporation) was used. An amorphous soft magnetic material foil as a coating material was temporarily fixed to the coating surface of the degreased base material with a cyanoacrylate-based adhesive (trade name: Aron Alpha). The base material on which the foil was temporarily fixed was attached and fixed to a rotary jig and set in the laser processing apparatus of FIG. After the inside of the vacuum chamber was evacuated, laser light was emitted while rotating the base material as shown in FIG. 3 and further vacuuming from the suction nozzle attached below the laser irradiation head. The laser irradiation conditions were such that a cylindrical surface having a width of about 10 mm was scanned for 12 rounds at a scan interval of 1 mm. When the coating portion of the obtained coating member was observed by X-ray diffraction, an amorphous phase was retained.

Example 4; The coating member obtained in Example 1 was set in a HIP device, and the temperature was set to 1100 ° C. and 1000
HIP treatment was performed for 1 hour at kgf / cm ² . When the cross-section of the coated member after the treatment was observed, it was confirmed that the pore-like defects scattered before the HIP treatment disappeared by almost 100% and a dense coating layer was obtained.

Example 5: The coating member obtained in Example 2 (having a coating layer thickness of about 0.2 mm) was treated with HI.
Set on P device, 1350 ℃, 1000kgf / cm
HIP treatment was performed at ² for 1 hour. The coated member after the treatment was cut, the cut surface was polished, and the state of the pores of the cut surface was observed with an optical microscope. Porosity remained within about 20 μm from the surface, but the porosity-like defects scattered inside the coating layer before HIP treatment were almost 100%.
It was confirmed that it disappeared and a dense coating layer was obtained.

Example 6; The coating member obtained in Example 3 (having a coating layer thickness of about 0.2 mm) was treated with HI.
Set on P device, 550 ℃, 2200kgf / cm ²
Then, HIP treatment was performed for 20 minutes. With respect to the coated member after the treatment, no remarkable change was visually observed. The hardness was not significantly changed before and after the HIP treatment, but the mechanical properties of the S45C heat-treated material were almost maintained.

Next, an impact test was conducted on the ten coated members. Only one coating member had the coating layer peeled off by impact. HI
An impact test was conducted on the coated member not subjected to the P treatment under the same conditions as above.
The individual coating layers were peeled off. In addition, the HIP treatment conditions are the same as those of ordinary iron-based materials (1100 ° C., 1000 kgf
/ Cm ² for 1 hour), the coating member treated instead of 8 peeled the coating layer out of 10. In addition, the coating member treated under normal HIP conditions is
As a result of line diffraction observation, the amorphous layer was hardly retained, Fe ₃ C was partially detected, and the elongation property of the base material S45C was remarkably deteriorated.

[0033]

According to the coating method of the present invention, even a member to be coated having a large coating area can be coated by laser welding. Therefore, even with a coating material such as ceramics, which has been conventionally impossible to be overlaid by welding by arc welding or electron beam welding, it is possible to be overlaid by welding regardless of the size of the area to be coated.

Further, since the coating method using the laser of the present invention is performed in a vacuum, the amount of pore-like defects is extremely small as compared with the coating member obtained by the working in the atmosphere. Moreover, since laser irradiation is performed while a vacuum is drawn between the coating surface and the condensing optical system, even if scattered particles or organic gas is generated from the base material or the coating material, the coating is not affected.

Further, if the coating material is temporarily fixed with an adhesive, not only a simple flat surface coating but also a curved surface can be coated, and the range of target materials that can be coated is expanded. Furthermore, when the coating member obtained by the method of the present invention is subjected to HIP treatment, even if the pore-like defect remains in the coating member, it is almost completely eliminated and an extremely dense coating layer is obtained.

Therefore, in response to the demand for composite parts by coating, which has been in increasing demand in recent years, the method of the present invention provides a ceramic-coated part excellent in wear resistance,
It seems that it will occupy an important position as a manufacturing technology for ceramics-coated parts having a solid electrically insulating coating or corrosion-resistant parts. Further, the present invention expands the field of application of laser processing technology and leads to the development of laser equipment.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view of an example of a laser processing apparatus for carrying out a coating method of the present invention.

FIG. 2 is a diagram for explaining a laser irradiation head and a suction nozzle shown in FIG.

FIG. 3 is a diagram for explaining an example of a coating method when a cylindrical member to be coated is used.

FIG. 4 is an explanatory diagram of a configuration of a conventional laser processing apparatus.

[Explanation of symbols]

 1 Vacuum Chamber 3 Laser Irradiation Head 3b Focusing Lens 4 Suction Nozzle 5 Triaxial Slider Device 6 YAG Laser Oscillator 7 Vacuum Pump 8 Optical Fiber W Coated Material C Coating Material

Claims (3)

[Claims] 1. A coated member having a powdery or foil-shaped coating material arranged on a coating surface is set under vacuum, and while evacuating between the condensing optical system and the coating surface under vacuum, Irradiating the coating material with laser light introduced by an optical fiber and the condensing optical system, and scanning the coating material with the laser light to coat the coating surface while melting the coating material. And a coating method using a laser. 2. The coating method using a laser according to claim 1, wherein the coating material is preliminarily fixed to the coating surface by an organic adhesive before the laser irradiation. .. 3. A coating method using a laser, which comprises subjecting the coating member coated with the coating material by the method according to claim 1 or 2 to hot isostatic pressing.