JP2007216241A - Laser beam peening device and laser beam peening method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam peening device and a laser beam peening method capable of performing the consistent peening on a workpiece placed in a liquid. <P>SOLUTION: The laser beam peening device 1 has a guide body 6 with its incident surface 6b being arranged so as to be in contact with the atmosphere, and its light emitting surface 6c being arranged so as to be in contact with a liquid 2. By guiding laser beams L via the guide body 6, a surface of a workpiece P can be irradiated with the laser beams L without directly passing the laser beam through a liquid surface 2a of the liquid 2 with the workpiece P arranged therein. Thus, the laser beam peening device 1 is capable of irradiating the laser beams L on the workpiece P without being affected by the flicker of the liquid surface 2a or the reflection by the liquid surface 2a, suppressing any fluctuation of the irradiation position and the irradiation intensity of the laser beams L with respect to the workpiece P arranged in the liquid 2, and performing the consistent peening. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser peening apparatus and method for changing the surface characteristics of a workpiece by irradiating the surface of the workpiece with a laser beam.

  Conventionally, shot peening that hardens the surface of the metal used as a workpiece in various fields such as automobile parts such as springs, gears, connecting rods and crankshafts, aircraft related parts such as jet engines and wings, and pressure vessels in chemical plants. Processing is being used. In the shot peening process, hard surfaces such as ceramics are collided with the surface of the work piece at high speed, and the surface of the work piece is hardened by forming a compressive stress portion in which compressive stress remains, In addition, the wear resistance is improved.

  On the other hand, in recent years, development of a laser peening process using a laser beam instead of a hard sphere has progressed. In the laser peening process, high-pressure plasma is generated on the surface of the workpiece by irradiation with a laser beam, and a compressive stress portion is formed on the surface of the workpiece by a reaction when the plasma expands. In this laser peening process, it is possible to form the compressive stress part to a deeper part of the work piece, so that the surface hardening of the work piece and the improvement of the wear resistance can be expected more than the shot peening process. .

As a technique related to such laser peening processing, for example, there is a laser peening method described in Patent Document 1. In this conventional laser peening method, a focused laser beam is irradiated onto a workpiece placed in a liquid such as an electrolytic solution.
JP 7-246483 A

  As described above, when the workpiece is placed in the liquid in the laser peening process, the confinement effect of the plasma generated on the surface of the workpiece due to the action of the inertia of the liquid is increased. There is an advantage in that the formation of the compressive stress portion can be facilitated as compared with the case where it is disposed on the surface. However, in the conventional laser peening method described above, when the laser beam is incident on the liquid from the atmosphere, the irradiation position of the laser beam on the workpiece due to liquid level fluctuations caused by vibrations or the reflection of the laser beam generated on the liquid level. There was a problem that irradiation intensity changed and stable peening treatment could not be performed. Since this becomes more conspicuous as the condensing degree of the laser beam is increased, a technique capable of performing a stable laser peening process on a workpiece placed in a liquid has been desired.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a laser peening apparatus and method capable of performing a stable peening process on a workpiece placed in a liquid. .

  In order to solve the above problems, a laser peening apparatus according to the present invention is a laser peening apparatus that changes the surface characteristics of a workpiece by irradiating the surface of the workpiece placed in a liquid with a laser beam. An incident surface on which the laser beam is incident and an exit surface from which the laser beam is emitted toward the workpiece, and a guide body for guiding the laser beam from the incident surface toward the exit surface. It is arranged outside the liquid, and the emission surface is arranged so as to be in contact with the liquid.

  In this laser peening apparatus, the liquid surface of the liquid on which the workpiece is disposed is directly guided by guiding the laser beam with a guide body in which the incident surface is disposed outside the liquid and the emission surface is disposed in the liquid. The surface of the workpiece can be irradiated with the laser beam without passing through. Therefore, this laser peening apparatus can irradiate the workpiece with the laser beam without being affected by the fluctuation of the liquid level or the reflection on the liquid level, and the irradiation position or irradiation of the laser beam on the workpiece placed in the liquid. Since fluctuations in intensity can be suppressed, stable peening processing can be performed.

  Moreover, it is preferable that the guide body further includes a reflection surface that reflects the laser beam incident from the incident surface to the emission surface. In this case, the guide body can have a function as a reflection mirror for changing the path of the laser beam, and the apparatus configuration can be simplified.

  Moreover, it is preferable that the reflecting surface is curved with a predetermined curvature. In this case, in addition to the function as a reflecting mirror, the guide body can have a function of condensing the laser beam, and the apparatus configuration can be further simplified.

  The guide body preferably has a graded refractive index distribution. In this case, the guide body can have a function as a condensing lens, and the apparatus configuration can be simplified.

  Further, an antireflection film is preferably formed on the incident surface. In this case, the reflection loss of the laser beam on the incident surface can be reduced, so that the efficiency of the peening process can be improved.

  Moreover, it is preferable that a photocatalytic functional film is formed on the emission surface. In this way, it is possible to automatically clean the exit surface, which is easily contaminated by being disposed in the liquid, by the photocatalytic function.

  The laser peening method according to the present invention is a laser peening method for changing the surface characteristics of a workpiece by irradiating the surface of the workpiece placed in a liquid with a laser beam, Has a light incident surface, and a laser beam is emitted toward the workpiece, and a guide body for guiding the laser beam from the light incident surface toward the light emission surface is disposed outside the liquid. A step of arranging the emission surface in contact with the liquid, a step of emitting a laser beam incident on the incidence surface from the emission surface into the liquid via the guide body, and irradiating the surface of the workpiece with the laser beam; It is characterized by having.

  In this laser peening method, the liquid surface of the liquid on which the workpiece is disposed is directly guided by guiding the laser beam with a guide body in which the incident surface is disposed outside the liquid and the output surface is disposed in the liquid. The surface of the workpiece can be irradiated with the laser beam without passing through. Therefore, in this laser peening method, the workpiece can be irradiated with a laser beam without being affected by fluctuations in the liquid level or reflection on the liquid level, and the irradiation position and irradiation of the laser beam on the workpiece placed in the liquid. Since fluctuations in intensity can be suppressed, stable peening processing can be performed.

  As described above, according to the laser peening apparatus and method of the present invention, a stable peening process can be performed on a workpiece placed in a liquid.

  Hereinafter, preferred embodiments of a laser peening apparatus and method according to the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram showing a laser peening apparatus according to a first embodiment of the present invention. A laser peening apparatus 1 shown in FIG. 1 is an apparatus for performing a process of curing the surface of a workpiece P at a processing site of the workpiece P such as an aircraft turbine blade or a shroud weld of a reactor pressure vessel. is there.

  The laser peening apparatus 1 includes a bottomed container 3 filled with a liquid 2, a light source 4 that emits a laser beam L, a light guide optical system 5 that shapes the laser beam L emitted from the light source 4, and a light guide optical system. And a guide body 6 that guides the laser beam L shaped by 5 and emits it toward the processing region.

  For example, pure water is used for the liquid 2 that fills the bottomed container 3. At the bottom of the bottomed container 3, for example, an XY stage (not shown) that can be driven in the horizontal direction is provided, and the workpiece P is placed substantially horizontally on the XY stage in the liquid 2. The

As the light source 4, a pulse laser that emits a laser beam L having a wavelength that is less affected by the liquid filling the bottomed container 3 is used. When pure water is used as the liquid 2, for example, an Nd-YAG laser having a wavelength of 1064 nm or a second harmonic having a wavelength of 532 nm is used. The peak power of the laser beam L is set to be, for example, 1 to several tens GW / cm ^{2 on} the surface of the workpiece P.

  The light guide optical system 5 includes a collimator lens 10 that converts the laser beam L emitted from the light source 4 into a parallel beam, a reflection mirror 11 that reflects the parallel laser beam L toward the bottomed container 3, and a parallel beam. A condensing lens 12 that condenses the luminous laser beam L.

  The guide body 6 is an optical component having a main body portion 6a formed in a cylindrical shape from a material having low light absorption with respect to the laser beam L, such as borosilicate glass or quartz glass. One end surface of the main body 6a is an incident surface 6b on which the laser beam L traveling to the bottomed container 3 side through the light guide optical system 5 is incident. An antireflection film 13 for reducing the reflection loss of the laser beam L is formed on the incident surface 6b.

  The other end surface of the main body 6a is an emission surface 6c from which the laser beam L guided by the main body 6a is emitted toward the workpiece P. A photocatalytic functional film 14 made of, for example, titanium oxide is formed on the emission surface 6c. The guide body 6 is held by a holding member (not shown) in a state where the exit surface 6c side of the main body 6a is immersed in the liquid 2, the entrance surface 6b is disposed so as to be in contact with the atmosphere, and the exit surface 6c is The liquid 2 is disposed in contact with the liquid 2.

  Next, the operation of the laser peening apparatus 1 having the above-described configuration will be described.

  First, a laser beam L is emitted from the light source 4 substantially parallel to the liquid surface 2 a of the liquid 2 in the bottomed container 3. The emitted laser beam L is reflected to the bottomed container 3 side while being collimated and condensed by the light guide optical system 5 and enters the incident surface 6 b of the guide body 6. The laser beam L is guided by the main body 6a of the guide body 6, and is emitted from the emission surface 6c into the liquid 2 without directly passing through the liquid surface 2a of the liquid 2 in the bottomed container 3, and is processed. The surface of the object P is irradiated.

  When the laser beam L is irradiated, as shown in FIG. 2, the surface of the workpiece P is instantly evaporated by the high peak power of the laser beam L, and high-pressure plasma is generated on the surface of the workpiece P.・ Expands. At this time, the surface of the workpiece P is plastically deformed by the reaction when the high-pressure plasma expands, and the compressive stress portion 15 having a depth of about 1.0 mm from the surface of the workpiece P is formed. Thereafter, the XY stage on which the workpiece P is placed is scanned and the compressive stress portion 15 is sequentially formed in a desired region on the surface of the workpiece P, whereby the peening process of the workpiece P is completed. .

  As described above, the laser peening apparatus 1 includes the guide body 6 that is disposed so that the incident surface 6b is in contact with the atmosphere and that the exit surface 6c is in contact with the liquid 2, and this guide body. By guiding the laser beam L through 6, the surface of the workpiece P can be irradiated with the laser beam L without directly passing the liquid surface 2 a of the liquid 2 on which the workpiece P is disposed. Therefore, in the laser peening apparatus 1, the workpiece P can be irradiated with the laser beam L without being affected by the fluctuation of the liquid surface 2 a or the reflection at the liquid surface 2 a, and the workpiece P placed in the liquid 2 can be irradiated. Since fluctuations in the irradiation position and irradiation intensity of the laser beam L can be suppressed, stable peening processing can be performed.

  An antireflection film 13 is formed on the incident surface 6 b of the guide body 6. For example, when pure water is used as the liquid 2, the reflectance when the laser beam L is directly incident on the liquid surface 2a is about 2%. On the other hand, the reflectance of the laser beam L at the incident surface 6 b of the guide body 6 is reduced to about 0.5% by the antireflection film 13. In addition, the reflectance of the laser beam L at the exit surface 6c of the guide body 6 is about 0.4% even without an antireflection film. Therefore, by causing the laser beam L to enter the liquid 2 through the guide body 6, the reflection loss of the laser beam L can be reduced by about 1%. As a result, the irradiation intensity of the laser beam L with respect to the workpiece P can be increased, and the efficiency of the peening process can be improved.

  Furthermore, a photocatalytic functional film 14 is formed on the exit surface 6 c of the guide body 6. For this reason, the emission surface 6c that is easily contaminated by being disposed in the liquid 2 can be automatically cleaned by the photocatalytic function.

  As a modification of the present embodiment, the main body portion 6d of the guide body 6 is formed by a rod lens having a graded refractive index distribution with a cylindrical axis as a central axis, like a laser peening apparatus 1A shown in FIG. May be. In this case, in addition to having the same effect as that of the above-described embodiment, the guide body 6 can have a function as a condensing lens. Therefore, the condensing lens 12 can be omitted in the light guiding optical system 5. This makes it possible to simplify the device configuration.

[Second Embodiment]
Next, a second embodiment of the laser peening apparatus according to the present invention will be described. The present embodiment is different from the first embodiment in which the guide body 6 is configured only by the main body portion 6a in that the guide body 6 is configured by the main body portion 6e and the cylindrical portion 6f. Is common to the first embodiment.

  That is, in the laser peening apparatus 20 according to the second embodiment, as shown in FIG. 4, the guide body 6 includes a cylindrical portion 6 f formed in a hollow cylindrical shape with a metal such as aluminum, and one end of the cylindrical portion 6 f. It is comprised by the flat main-body part 6e fixed liquid-tightly. The guide body 6 is held by a holding member (not shown) in a state in which one end side of the cylindrical portion 6f to which the main body portion 6e is fixed is immersed in the liquid 2. Accordingly, the main body 6e is disposed at a position deeper than the liquid surface 2a of the liquid 2. The incident surface 6 b of the main body 6 e is disposed so as to be in contact with the atmosphere inside the cylindrical portion 6 f, and the emission surface 6 c is disposed so as to be in contact with the liquid 2.

  Also in this laser peening apparatus 20, since the laser beam L does not directly pass through the liquid surface 2a of the liquid 2 due to the guide of the laser beam L through the guide body 6, the fluctuation of the liquid surface 2a and the reflection on the liquid surface 2a are prevented. The workpiece P can be irradiated with the laser beam L without being affected. Thereby, since the fluctuation | variation of the irradiation position and irradiation intensity | strength of the laser beam L with respect to the to-be-processed object P arrange | positioned in the liquid 2 can be suppressed, it becomes possible to perform the stable peening process.

  Further, in this laser peening apparatus 1, since the optical path length of the laser beam L passing through the main body 6e of the guide body 6 can be reduced, the irradiation position and irradiation intensity of the laser beam L with respect to the workpiece P disposed in the liquid 2 Fluctuations can be effectively suppressed, and a more stable peening process can be performed.

[Third Embodiment]
Subsequently, a third embodiment of the laser peening apparatus according to the present invention will be described. This embodiment is different from the first embodiment in which the reflecting surface 6g is not provided in that the reflecting surface 6g is provided on one end side of the guide body 6.

  That is, in the laser peening apparatus 30 according to the third embodiment, as shown in FIG. 5, the main body portion 6a of the guide body 6 is formed in a prismatic shape, and the side surface on one end side of the main body portion 6a becomes the incident surface 6b. The other end surface of the main body 6a is an emission surface 6c. In addition, an inclined surface that is inclined at about 45 ° with respect to the incident surface 6b is formed on one end side of the main body 6a. This inclined surface causes the laser beam L incident on the incident surface 6b to be directed toward the emission surface 6c. It is a reflective surface 6g that totally reflects toward it. And the guide body 6 is hold | maintained by the holding member (not shown) in the state in which the one end side of the main-body part 6a was immersed in the liquid 2, the entrance plane 6b is arrange | positioned so that air | atmosphere may be contacted, and the output surface 6c It arrange | positions so that the liquid 2 may be contact | connected.

  Also in this laser peening apparatus 30, since the laser beam L does not pass directly through the liquid surface 2a of the liquid 2 by the guide of the laser beam L through the guide body 6, the fluctuation of the liquid surface 2a and the reflection at the liquid surface 2a are prevented. The workpiece P can be irradiated with the laser beam L without being affected. Thereby, since the fluctuation | variation of the irradiation position and irradiation intensity | strength of the laser beam L with respect to the to-be-processed object P arrange | positioned in the liquid 2 can be suppressed, it becomes possible to perform the stable peening process.

  Further, in the laser peening apparatus 30, since the guide body 6 can have a function as a reflection mirror that changes the path of the laser beam L, the reflection mirror 11 can be omitted from the light guide optical system 5. The configuration can be simplified.

  As a modification of the present embodiment, the reflection surface 6g of the main body 6a of the guide body 6 may be a curved surface that curves with a predetermined curvature, as in a laser peening apparatus 30A shown in FIG. In this case, the guide body 6 can have a function of condensing the laser beam L in addition to the function as a reflection mirror. Thereby, in the light guide optical system 5, it is possible to omit both the reflection mirror 11 and the condenser lens 12, and the apparatus configuration can be further simplified. The curved surface is not limited to one having a constant curvature, and may be a material whose curvature changes continuously, such as a parabolic surface.

  The present invention is not limited to the above embodiment. For example, the liquid 2 filling the bottomed container 3 is not limited to pure water, and for example, oil or various solvents with low flammability may be used. The absorption efficiency of the workpiece P with respect to the laser beam L varies depending on the type of the liquid 2 (or the type of the solvent constituting the liquid 2). For example, when the material of the surface of the workpiece P is aluminum, the absorption efficiency of the workpiece P with respect to the laser beam L compared to the case of using pure water as the liquid 2 by using oil as the liquid 2. Can be improved by about 10%.

  Further, the light source 4 is not limited to the Nd-YAG laser, and an ultraviolet wavelength laser such as an excimer laser can also be used. In this case, it is preferable that the guide body 6 is formed of a material having a small light absorbability with respect to ultraviolet light, such as calcium fluoride or magnesium fluoride.

  Furthermore, the relative scanning of the irradiation position of the laser beam L with respect to the workpiece P is not limited to the XY stage as described above. For example, as shown in FIG. 7, the incident surface 6b of the main body 6a of the guide body 6 is inclined with respect to the emission surface 6c, and the laser beam L is directed toward the workpiece P from a position shifted from the center of the emission surface 6c. And the relative rotation of the irradiation position of the laser beam L on the workpiece P is performed by combining the rotation of the guide body 6 and the scanning of the XY stage (or the angle scanning of the reflection mirror 11). Also good.

  In addition, as shown in FIG. 8, a plurality of rollers 18 are arranged at the bottom of the bottomed container 3, and the workpiece P is slid on the rollers 18 so as to pass the irradiation position of the laser beam L. Good. In this case, a plurality of workpieces P can be continuously peened. In addition, when the workpiece P is slid in the liquid 2, the liquid surface 2a fluctuates. However, in each of the above-described embodiments, the laser beam L is incident on the liquid 2 through the guide body 6. The influence of fluctuation 2a can be avoided and stable peening processing can be performed.

It is a figure which shows the laser peening apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the state of the to-be-processed object at the time of a peening process. It is a figure which shows the modification of the laser peening apparatus shown in FIG. It is a figure which shows the laser peening apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the laser peening apparatus which concerns on 3rd Embodiment of this invention. It is a figure which shows the modification of the laser peening apparatus shown in FIG. It is a figure which shows the laser peening apparatus which concerns on the modification of this invention. It is a figure which shows the laser peening apparatus which concerns on another modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A, 20, 30, 30A ... Laser peening apparatus, 2 ... Liquid, 6 ... Guide body, 6b ... Incident surface, 6c ... Outgoing surface, 6g ... Reflective surface, 13 ... Antireflection film, 14 ... Photocatalytic functional film , L: Laser beam, P: Work piece.

Claims (7)

A laser peening apparatus that changes the surface characteristics of a workpiece by irradiating the surface of the workpiece placed in a liquid with a laser beam,
An incident surface on which the laser beam is incident, and an emission surface on which the laser beam is emitted toward the workpiece, and a guide body for guiding the laser beam from the incident surface toward the emission surface,
The laser peening apparatus according to claim 1, wherein the incident surface is disposed outside the liquid, and the emission surface is disposed in contact with the liquid.   The laser peening apparatus according to claim 1, wherein the guide body further includes a reflection surface that reflects the laser beam incident from the incident surface with respect to the emission surface.   The laser peening apparatus according to claim 2, wherein the reflection surface is curved with a predetermined curvature.   2. The laser peening apparatus according to claim 1, wherein the guide body has a graded refractive index distribution.   The laser peening apparatus according to any one of claims 1 to 4, wherein an antireflection film is formed on the incident surface.   6. The laser peening apparatus according to claim 1, wherein a photocatalytic functional film is formed on the emission surface. A laser peening method for changing the surface characteristics of a workpiece by irradiating the surface of the workpiece placed in a liquid with a laser beam,
A guide body having an incident surface on which the laser beam is incident and an emission surface on which the laser beam is emitted toward the workpiece, and guiding the laser beam from the incident surface toward the emission surface, A step of disposing the incident surface outside the liquid and the exit surface in contact with the liquid;
And a step of emitting the laser beam incident on the incident surface from the exit surface into the liquid via the guide body and irradiating the surface of the workpiece with the laser beam. Laser peening method.

Images