JP7232452B2 - Plating film surface modification method and apparatus - Google Patents

Description

The present invention relates to a surface modification method and apparatus for modifying a plating film by irradiating laser light.

2. Description of the Related Art Conventionally, a plating film is formed by plating in order to improve the durability of the surface of a material such as a metal material. Unlike electroplating, electroless plating has been applied to various materials because a uniform plating film can be formed simply by immersion in a plating bath. A representative example of the electroless plating film is a nickel (Ni) plating film containing phosphorus (P) (hereinafter referred to as “Ni—P plating film”). It is known that crystallization proceeds by lowering , and the hardness of the plating film is increased to improve durability such as wear resistance.

It is also known that the hardness of the plating film is improved by subjecting the plating film to surface treatment such as heat treatment. It is described that the surface hardening treatment is performed by surface treatment such as polishing treatment, shot blasting treatment, laser beam treatment, or high-frequency induction heating treatment. In addition, Patent Document 3 describes a surface modification method for improving the hardness of the plating film by suppressing the influence of heating on the material by locally heat-treating the surface of the plating film by irradiating it with a laser beam. .

Japanese Patent No. 3066798 Retable 98/31849 JP 2017-222922 A

In the Ni—P plating film, the hardness of the plating film can be improved by reducing the phosphorus content of the plating film, but the obtained hardness is up to about 700 HV in Vickers hardness, which is sufficient. difficult to obtain.

When surface treatment such as heat treatment is performed, a sufficient Vickers hardness of about 900 HV can be obtained by heat treatment at a heating temperature of 400 ° C. for about 1 hour. Depending on the material on which is formed, heating causes distortion as an effect of annealing, and adverse effects such as a decrease in tensile strength due to a decrease in hardness of the material itself occur.

Further, in Patent Document 3, heating is performed from the surface of the plated film by irradiating a laser beam, thereby increasing the hardness of the plated film and suppressing the thermal effect on the material. However, the hardness of the surface layer of the material is reduced by about 10%, and there is a problem that the material is thermally affected by the irradiation of the laser beam.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method and apparatus for modifying the surface of a plated film, which can increase the surface hardening of the plated film and suppress the decrease in the hardness of the surface of the material.

The method for modifying the surface of a plating film according to the present invention uses a pulse laser with a pulse width of 1 μs to 200 μs for a plating film having a thickness of 1 μm to 30 μm formed on a hardened surface of a material made of steel. is irradiated to harden the surface of the plating film to a hardness of 900 Hv or more, and the hardness of the material surface is maintained at 700 Hv or more. Further, the irradiation amount of the pulse laser is set so that the fluence is 0.01 J/cm ² to 2.0 J/cm ² . Further, the material is surface-hardened by carburizing or quenching, and the plated film is formed by electroless plating.

A sliding member according to the present invention is a sliding member in which a hardened surface of a main body made of steel is formed with a plated film having a thickness of 1 μm to 30 μm, and the surface of the main body has a hardness of 700 Hv or more, The surface hardness of the plating film is 900 Hv or more.

The apparatus for modifying the surface of a plating film according to the present invention modifies a plating film having a thickness of 1 μm to 30 μm formed on a hardened surface of a steel material by irradiating it with a laser beam. A surface modification apparatus comprising: a light source unit that emits a pulsed laser having a pulse width of 1 μs to 200 μs; and a laser beam emitted from the light source unit having a fluence of 0.01 J/ cm ² to 2.0 J/cm ² to harden the surface of the plating film to a hardness of 900 Hv or more and control the hardness of the surface of the material to be maintained at 700 Hv or more. there is Further, the irradiation control unit controls irradiation by moving the surface of the material relative to the irradiation region.

By providing the above configuration, the present invention can locally heat-treat the plated film by irradiating a pulsed laser beam, suppressing the influence of heating on the material and improving the hardness of the plated film. becomes possible.

It is explanatory drawing which shows the result of having analyzed using the finite element method about the heat processing by irradiation of a laser beam. It is explanatory drawing which shows the result of having analyzed using the finite element method about the heat processing by irradiation of a laser beam. It is explanatory drawing which shows the result of having analyzed using the finite element method about the heat processing by irradiation of a laser beam. This is an example using a device that scans and irradiates a material surface with a laser beam. This is an example using a device that irradiates a laser beam while rotating a material. This is an example using a device that scans and irradiates a laser beam while rotating a material.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments according to the present invention will be described in detail. It should be noted that the embodiments described below are preferred specific examples for carrying out the present invention, and thus various technical limitations are made, but the present invention is particularly limited in the following description. These forms are not intended to be limiting unless specified.

The material is not particularly limited as long as it is a metal material that can be plated, but it is suitable for materials that need to be finished with high hardness, such as machine parts and tools. For example, materials such as machine structural steel such as chromium molybdenum steel, tool steel such as carbon tool steel, special purpose steel such as high carbon chromium bearing steel, and cast iron such as gray cast iron. For such materials, surface hardening treatments such as carburizing and quenching are performed, but further heat treatment after surface treatment is susceptible to deterioration of strength and deformation of the material, so it should be avoided as much as possible. desirable. It is also effective for materials that have a low melting point such as aluminum and are prone to deformation such as distortion.

The plating film to be formed on the surface of the material is not particularly limited as long as it can be formed on the surface of the metal material by plating. preferred. In particular, a Ni—P plating film containing Ni as a main component is preferable because the hardness can be increased by a laser beam. The film thickness of the plated film is preferably 1 μm to 30 μm.

Moreover, the hardness of the plating film can be increased by compounding a carbon material in the plating film. Carbon materials include, for example, carbon microparticles such as nanodiamonds, carbon nanotubes, and fullerenes. Such a carbon material can be added to the plating solution in advance and incorporated into the plating film by plating. Moreover, a carbon material can be compounded by preparing a coating liquid containing a carbon material and coating the formed plating film. The hardness of the plated film made by combining such a carbon material can be further improved by irradiating with a laser beam.

The laser beam to be irradiated onto the plated film can be irradiated using a laser irradiation device capable of oscillating known pulsed laser beams such as fiber laser, YAG laser, CO ₂ laser, and high-power semiconductor laser. It is necessary to set the pulse width to an appropriate value so as to limit the depth range in which the film is thermally affected and the substrate surface is not thermally affected. By irradiating a plated film with a thickness of 1 μm to 30 μm with a laser beam with a pulse width of 1 μs to 200 μs, the plated film is evenly heated and hardened while suppressing the thermal effect on the material. can be done. Specifically, by hardening the hardness of the plating film surface to 900Hv or more and maintaining the hardness of the material surface to 700Hv or more, it is possible to harden the plating film by heating and suppress the influence of heat on the material. becomes.

1 to 3 are explanatory diagrams showing the results of analysis of heat treatment by laser light irradiation using the finite element method. Publicly known software (COMSOL manufactured by Keisoku Engineering Co., Ltd.) was used for the model calculation used in the finite element method. As a condition setting for the model, a laser pulse is incident on the center of a disk model with a diameter of 10 mm and a thickness of 1 mm, which is rotationally symmetric around the beam center axis, and the maximum temperature reached on the surface of the plating film is about 800°C, the melting point of the plating film. was analyzed by setting the laser output to .

FIG. 1 shows an example of irradiation with a laser beam having a pulse width of 500 μs , and the laser was set to have an average output of 150 W and a repetition frequency of 200 Hz. FIG. 1(a) shows the temperature distribution in the depth direction immediately after one pulse is incident, and FIG. 1(b) shows the temperature distribution in the surface and depth directions immediately after irradiation. FIG. 1(c) is a graph showing the temperature change in the depth direction at the center of the irradiation region, showing the transition of the temperature change with elapsed time (milliseconds) from the start of irradiation.

It can be seen that in irradiation with a laser beam having a pulse width of 500 μs, the surface is rapidly heated during the irradiation of the laser beam, and after the irradiation of the laser beam is completed, the heat is transferred inside and cooled. The region heated to 400° C. or higher immediately after irradiation extends to a depth of 33 μm from the surface, and it can be seen that the heat affects the material deeper than the plating film with a thickness of 4 μm. The maximum temperature at the interface between the plating film and the material reaches 510°C, and the thermal effect on the material is increasing.

FIG. 2 shows an example of irradiation with a laser beam having a pulse width of 1 μs, with an average output of 400 W and a repetition frequency of 100 kHz. FIG. 2(a) shows the temperature distribution in the depth direction immediately after one pulse is incident, and also shows a partially enlarged view near the irradiation surface. FIG. 2(b) shows the temperature distribution in the surface and depth directions immediately after irradiation. FIG. 2(c) is a graph showing the temperature change in the depth direction at the center of the irradiation region, showing the transition of the temperature change with elapsed time (microseconds) from the start of irradiation.

In irradiation with a laser beam with a pulse width of 10 μs, heating during irradiation and cooling after irradiation can be confirmed as in the case of a laser beam with a pulse width of 500 μs. It is shown that the depth of the region is within 1 μm, which is significantly shallower than that in the case of irradiation with a laser beam having a pulse width of 500 μs . In this case, the maximum temperature reached at a depth of 4 μm, which is the interface between the plating film and the material, is 80° C., indicating that the thermal effect on the material is greatly reduced. Moreover, the plated film can be sufficiently heat-treated, and the hardness of the surface of the plated film can be increased.

FIG. 3 shows an example of irradiation with a laser beam having a pulse width of 0.04 μsec, with an average output of 400 W and a repetition frequency of 100 kHz. FIG. 3(a) shows the temperature distribution in the depth direction immediately after one pulse is incident, and also shows a partially enlarged view near the irradiated surface. FIG. 3(b) shows the temperature distribution in the surface and depth directions immediately after irradiation. FIG. 3(c) is a graph showing the temperature change in the depth direction at the center of the irradiation region, showing transition of the temperature change with elapsed time (nanoseconds) from the start of irradiation.

When irradiated with a laser beam having a pulse width of 0.04 μs, the region heated to 400° C. or higher is within 0.2 μm from the surface, and the boundary surface between the plating film and the material is 4 μm deep. The maximum reaching temperature is 20°C. Therefore, although there is almost no thermal influence on the material, the heating of the plated film is insufficient and it is difficult to sufficiently increase the hardness.

It is desirable that the amount of laser light irradiation heats the plating film to increase its hardness and suppresses the influence of heating of the material, and it is necessary to set an optimum value according to the output of the laser. Specifically, for a plated film with a film thickness of 1 μm to 30 μm, the irradiation dose is set so that the fluence is 0.01 J/cm ² to 2.0 J/cm ² , thereby ablating the surface of the plated film. It is possible to evenly heat and harden the plated film without causing any such phenomena as above, and without exerting a thermal influence on the material.

A plating film surface modification apparatus that performs such irradiation control includes a light source unit that emits a pulse laser with a pulse width of 1 μs to 200 μs, and a laser beam emitted from the light source unit to a predetermined irradiation area. Irradiation controlled so that the hardness of the plating film surface is hardened to 900Hv or more and the hardness of the material surface is maintained at 700Hv or more by irradiating with an irradiation amount that gives a fluence of 0.01 J/cm ² to 2.0 J/cm ² . and a control unit. The irradiation control unit controls the irradiation by moving the material surface relative to the irradiation area, making it possible to adjust the heat accumulation state of the plating film according to the average irradiation amount (irradiation density) that accompanies the movement. , the surface modification treatment can be finely controlled according to the heat dissipation state of the plating film.

4 to 6 are schematic configuration diagrams relating to a surface modification apparatus for a plated film. FIG. 4 shows an example using a device that scans and irradiates a material surface with a laser beam. A well-known laser irradiation device 10 is used as a light source, and a galvanometer scanner 11 and an optical adjustment unit 12 are provided as an irradiation control unit. The galvanometer scanner 11 serving as a moving part passes through an optical adjusting part 12 for performing a mechanical adjustment, and scans the plated film surface of the material S. As shown in FIG. By irradiating while scanning the laser beam, the irradiation amount per unit area can be controlled, and by adjusting the scanning speed of the laser beam, it is possible to uniformly modify the plating film in the irradiated area. .

FIG. 5 shows an example using a device that irradiates a laser beam while rotating a material. As a light source unit, a known laser irradiation device 20 is used, and as an irradiation control unit, a rotating device (not shown) and an optical adjustment unit 21 are provided, and the laser light L emitted from the laser irradiation device 20 is condensed or The light passes through the optical adjustment unit 21 that performs optical adjustment such as diffusion, and is irradiated toward the plated film surface of the cylindrical material T. As shown in FIG. The material T is rotated about its central axis by using a rotating device serving as a moving part, and the surface of the material T is irradiated with laser light while being rotated at a predetermined rotational speed. By adjusting the rotation speed of the material, it becomes possible to uniformly modify the plating film in the irradiation area.

FIG. 6 shows an example using a device that scans and irradiates a laser beam while rotating a material. A known laser irradiation device 30 is used as a light source, and a galvanometer scanner 31, a rotating device (not shown) and an optical adjustment unit 32 are provided as an irradiation control unit, and the laser light L emitted from the laser irradiation device 30 passes through an optical adjustment unit 32 that performs optical adjustment such as light condensing or diffusion, and is scanned against the plated film surface of the cylindrical material U by a galvanometer scanner 31 that serves as a moving unit. Then, the scanning line is set along the central axis direction of the material U and irradiated. Both ends of the material U are gripped by the supporting members 33 and rotated about the central axis by using a rotating device (not shown) serving as a moving part. By scanning and irradiating the laser light in the direction of the central axis while rotating the surface of the material about the central axis, irradiation control can be performed on the irradiation area.

EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples.

[Example 1]
A cylindrical rod (4 mm in diameter and 20 mm in length) made of carburized chromium steel was prepared as a metal material to be used as a raw material. Using an electroless nickel plating solution (manufactured by Nippon Kanigen Co., Ltd.; Schumer SEK-670), an electroless Ni—P plating film with a thickness of 20 μm (P content: 7% by weight) is applied to the entire surface of the rod-shaped body. was formed by a conventional method. The hardness of the formed plating film was measured with a Vickers hardness tester (manufactured by Akashi Co.; AVK-C2V3) and found to be 769 HV. The bar was cut in a direction orthogonal to the axial direction, and the hardness was measured at a depth of 0.1 mm from the surface of the material, which was 743 HV.

A high-output laser diode (M10Y-808.3-150Q, manufactured by Coherent-Dylas) is used as a laser light source, and a pulsed laser beam is emitted by driving with a high-output pulse power supply (PLSS17B, manufactured by Unitac). The emitted laser light is condensed into a line by a cylindrical lens and irradiated with the laser light.

As shown in Fig. 5, one end of the plated rod-shaped body was fixed to a jig of a rotating device (manufactured by Oriental Motor Co., Ltd.; model number US2-26JA-5-1) and rotated about the central axis. While rotating at 100 rpm, the surface of the plated film was irradiated with a laser beam having a pulse width of 10 μs and a repetition frequency of 5 kHz, and was continuously irradiated at an average output of 6.3 W for 10 minutes. The dose per unit area (fluence) was 0.04 J/cm ² .

It was 923 HV when the hardness of the plating film surface after irradiation was measured. Further, when the rod-shaped body after irradiation was cut in a direction perpendicular to the axial direction and the hardness was measured at a depth of 0.1 mm from the material surface, it was 718 HV, and the decrease in hardness on the material side was 3%. .

[Comparative Example 1]
As in Example 1, while rotating the plated bar, a laser beam was applied using a fiber laser oscillator (manufactured by IPG). The laser light to be irradiated had a pulse width of 300 μs and a repetition frequency of 600 Hz, and was irradiated continuously for 7.6 seconds at an average output of 135 W. The hardness of the plated film surface after irradiation was measured in the same manner as in Example 1 and found to be 1165 HV. After the irradiation, the bar was cut in a direction orthogonal to the axial direction, and the hardness was measured at a depth of 0.1 mm from the surface of the material. It can be seen that the thermal effect on the material is increasing.

[Comparative Example 2]
As in Example 1, while rotating the plated bar, laser light was irradiated using an all-solid-state laser oscillator (manufactured by Spectra Physics). The irradiated laser light had a pulse width of 0.04 μs and a repetition frequency of 10 kHz, and was continuously irradiated for 1 minute at an average output of 10.6 W. The hardness of the plated film surface after irradiation was measured in the same manner as in Example 1 and found to be 696 HV. After the irradiation, the bar was cut in a direction orthogonal to the axial direction, and the hardness was measured at a depth of 0.1 mm from the surface of the material. The hardness of the plating film could not be increased by laser light irradiation.

[Comparative Example 3]
In the same manner as in Example 1, the plated bar was heat-treated in the air at 400° C. for 1 hour using a heating device (KDF-S80 manufactured by Denken Co., Ltd.). After the heat treatment, the surface hardness of the plated film was measured in the same manner as in Example 1 and found to be 1381 HV. When the heated bar was cut in a direction orthogonal to the axial direction and the hardness was measured at a depth of 0.1 mm from the surface of the material, it was 565 HV, and the hardness of the surface of the material decreased by 24%. It can be seen that although the hardness of the plated film is increased, the hardness of the material side is decreased, and the heat effect is increased.

[Example 2]
A plate-like body (15 mm long, 50 mm wide, 2 mm thick) made of chromium-molybdenum steel was prepared as a metal material as a raw material. As in Example 1, an electroless Ni—P plated coating (P content: 7% by weight) having a thickness of 20 μm was formed on the entire surface of the plate. The hardness of the formed plating film was measured with a Vickers hardness tester (manufactured by Akashi Co.; AVK-C2V3) and found to be 492 HV. When the plate-like body was cut in the thickness direction and the hardness was measured at a depth of 0.1 mm from the surface of the material, it was 741 HV.

A fiber laser device (manufactured by IPG Photonics; YLR-150/1500-QCW) was used as a laser light source, and was set to emit a laser beam with a pulse width of 200 μs and a repetition frequency of 600 Hz with a peak output of 1125 W. As shown in FIG. 4, the emitted laser light is deflected and controlled along a predetermined scanning direction using a galvanometer scanner (manufactured by SUNNY TECHNOLOGY), and the deflected laser light is incident on a cylindrical lens. The laser beam is condensed along a predetermined scanning line to control the scanning of the laser beam.

The galvanometer movement speed of the galvano scanner device was set to 100 mm/sec, and the material surface was irradiated with the laser beam 100 times. The dose per unit area (fluence) was 1.2 J/cm ² .

It was 916 HV when the hardness of the plated film surface after irradiation was measured. Further, when the plate-like body after irradiation was cut in the thickness direction and the hardness was measured at a depth of 0.1 mm from the material surface, it was 705 HV, and the decrease in hardness on the material side was 5%.

[Comparative Example 4]
In the same manner as in Example 2, the plated plate was heat-treated in the air at 400° C. for 1 hour using a heating device (KDF-S80 manufactured by Denken Co., Ltd.). After the heat treatment, the surface hardness of the plated film was measured in the same manner as in Example 2, and was 942 HV. When the plate-like body after heating was cut in the thickness direction and the hardness was measured at a depth of 0.1 mm from the surface of the material, it was 565 HV, and the hardness of the surface of the material decreased by 24%. It can be seen that although the hardness of the plated film is increased, the hardness of the material side is decreased, and the heat effect is increased.

[Example 3]
A cylindrical rod-shaped body subjected to electroless nickel plating was prepared in the same manner as in Example 1, and both ends of the rod-shaped body were set in a rotating device as shown in FIG. While rotating the rotating device about the central axis at a rotation speed of 250 rpm, using the same laser light source as in Example 2, the laser light was applied to the surface of the plating film with a pulse width of 200 μs and a repetition frequency of 600 Hz. Irradiated at a peak power of 1500W. The emitted laser light was configured to scan and control the laser light using a scanning device similar to that of Example 2, and the laser light was irradiated 100 times with the galvanometer moving speed set to 100 mm/sec. A scanning line shape set along the central axis direction of was irradiated. Therefore, the entire outer peripheral surface of the rod-shaped body is irradiated with the laser beam and heat-treated by the rotational movement of the rod-shaped body and the scanning control of the laser beam. The dose per unit area (fluence) was 1.5 J/cm ² .

After the irradiation, the bar was cut in a direction orthogonal to the axial direction, and the hardness of the plating film was measured to be 916 HV. Further, when the hardness was measured at a depth of 0.1 mm from the surface of the bar, it was 705 HV, and the decrease in hardness on the material side was 5%.

Further, when the cylindrical bar was cut along the axial direction and the hardness distribution of the plating film was measured from the cross section, it was confirmed that the hardness was substantially uniformly increased. The fact that such a hardness distribution was obtained indicates that the outer peripheral surface of the rod-shaped body was heat-treated almost uniformly by controlling the rotation of the rod-shaped body and the irradiation control of the laser beam by scanning control of the laser beam. .

As described above, by irradiating the plated film formed on the surface of the material with a laser beam having a pulse width of 1 μs to 200 μs, the plated film can be locally heat-treated. It is possible to improve the hardness of the plating film while suppressing the influence of heating.

A main body having a surface hardness of 700 Hv or more and a plating film having a surface hardness of 900 Hv or more formed on the surface of the main body are provided by treating the sliding member on which the plating film is formed by the surface modification method described above. A sliding member can be obtained. For example, plating films such as Ni--P and Ni--B are known for the sliding surfaces of sliding members such as automobile parts and chain pins whose bodies are made of metal materials such as carbon steel and carburized chromium steel. By irradiating the formed plating film with a pulse laser, the hardness of the surface of the main body can be maintained at 700 Hv or more and the surface hardness of the plating film can be hardened to 900 Hv or more. Therefore, it is possible to obtain a high-quality sliding member by improving the sliding characteristics and durability of the sliding surface.

DESCRIPTION OF SYMBOLS 10... Laser irradiation apparatus 11... Galvano scanner 12... Optical adjustment part 20... Laser irradiation apparatus 21... Optical adjustment part 30... Laser irradiation apparatus 31... Galvanometer scanner, 32 Optical adjustment unit, 33 Support member, S, T, U Material

Claims (5)

A pulse laser with a pulse width of 1 μs to 200 μs is applied to a plating film with a thickness of 1 μm to 30 μm formed on the hardened surface of a steel material to harden the surface of the plating film to a hardness of 900 Hv or more. A method for modifying the surface of a plated film by increasing the hardness of the surface of the material and maintaining the hardness of the material surface at 700 Hv or more. 2. The method for modifying the surface of a plating film according to claim 1, wherein the irradiation amount of the pulse laser is set so that the fluence is 0.01 J/cm ² to 2.0 J/cm ² . 3. The method for modifying the surface of a plated film according to claim 1, wherein the material is surface-hardened by carburizing or quenching, and the plated film is formed by electroless plating. A plated film surface modification apparatus for modifying a plated film having a thickness of 1 μm to 30 μm formed on a hardened surface of a material made of steel by irradiating a laser beam with a pulse width of 1 μs. A light source unit that emits a pulse laser of up to 200 μsec, and a fluence of 0.01 J / cm for a predetermined irradiation area of the laser light emitted from the light source unit ² ~2.0 J/cm ² and an irradiation control unit for controlling the hardness of the surface of the plating film to 900 Hv or more by irradiating with the irradiation amount of , and maintaining the hardness of the surface of the material at 700 Hv or more. 5. The apparatus for modifying the surface of a plated film according to claim 4, wherein the irradiation control section controls the irradiation by moving the surface of the material relative to the irradiation region.

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