Method for surface treatment of DLC coated member
11618127 · 2023-04-04
Assignee
Inventors
Cpc classification
B24C1/04
PERFORMING OPERATIONS; TRANSPORTING
International classification
Abstract
A method for surface treatment of a DLC coated member that includes: taking as a treatment subject a DLC coated member having a DLC film coated on a base material surface; ejecting substantially spherical ejection particles having a median diameter of from 1 μm to 20 μm and a falling time through air of not less than 10 s/m against a surface of the film of the member at an ejection pressure of from 0.01 MPa to 0.7 MPa; and forming dimples on the surface of the film without exposing the base material so that a total projected area of the dimples is 50% or more of a treated region and so that the surface of the DLC film is processed to an arithmetic mean height (Sa) of from 0.01 μm to 0.1 μm and a texture aspect ratio (Str) of 0.4 or more.
Claims
1. A method for surface treatment of a DLC coated member, the method comprising: taking as a treatment subject a DLC coated member having a DLC film coated on a surface of a base material; ejecting substantially spherical metal-based or ceramic-based ejection particles of which a particle diameter and a density are set to have a median diameter D50 of within a range from 1 μm to 20 μm and a falling time in still air condition of not less than 10 s/m against a surface of the DLC film of the DLC coated member at an ejection pressure of from 0.01 MPa to 0.7 MPa; and forming dimples on the surface of the DLC film without exposing the base material so that a total projected area of the dimples is not less than 50% of a treated region and so that the surface of the DLC film is processed to an arithmetic mean height (Sa) of from 0.01 μm to 0.1 μm and a texture aspect ratio (Str) of not less than 0.4.
2. The method of claim 1, wherein ejection velocity of the ejection particles is not less than 80 m/s.
3. The method of claim 1, wherein the treatment subject is a DLC coated member with a DLC film formed on the surface of the base material smoothed to a surface roughness Ra of not more than 0.1 μm.
4. The method of claim 2, wherein the treatment subject is a DLC coated member with a DLC film formed on the surface of the base material smoothed to a surface roughness Ra of not more than 0.1 μm.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The objects and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof provided in connection with the accompanying drawings in which:
(2)
(3)
(4)
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(5) Explanation follows regarding an exemplary embodiment of the present invention.
(6) Treatment Subject Article
(7) The subject for treatment by the surface treatment method of the present invention has a surface coated with a DLC film/s, and also has dimples formed on the surface so as to exhibit the advantageous effects of improved slidability and improved demoldability etc. due to oil reservoirs, air reservoirs, release agent reservoirs, etc. The subject for treatment therewith may be any of various DLC coated members that have a DLC film formed thereon and that also find a beneficial effect from forming dimples on the surface of the DLC film, such as, for example, cutting-edges of cutting tools, sliding surfaces of sliding members such as bearings, shafts, etc., molding surfaces of various molds, and the like. The DLC coated member is not limited to being a member entirely coated in a DLC, and may be partially coated with a DLC.
(8) The material of the base material of the DLC coated member that is the subject for treatment is not particularly limited as long as it is a material a DLC film can be formed thereon. Examples of materials to be subject to treatment include various metal base materials such as cemented carbide, cold-worked die steel, high speed tool steel, stainless steel, or the like, as well as ceramic base materials.
(9) Note that in cases in which an under layer is formed on the surface of a treatment subject member, and then of film of DLC is formed on the surface of the under layer, the under layer corresponds to the base material of the present invention.
(10) The DLC coated member serving as the treatment subject is preferably a treatment subject having a DLC film formed on a base material surface polished to a mirror finish having a surface roughness Ra of not more than 0.1 μm. This is because if the surface roughness Ra exceeds 0.1 μm then tips of indentations and protrusions are liable to become the origin of breaks such that detachment readily occurs when treated by the present invention.
(11) There are no particular limitations to the method for forming the DLC film on the DLC coated member that is the treatment subject or to the type of the DLC film formed. The DLC film that is subject to the treatment of the present invention may be a high hardness hydrogen-free DLC film called tetrahedral amorphous carbon (ta-C) which is formed using a vacuum arc deposition method, may be a low hardness hydrogen-free DLC film called amorphous carbon (a-C) which is formed by a sputtering method or the like, may be a hydrogen containing DLC film called hydrogenated amorphous carbon (a-C:H) (with films therein of comparatively high hardness called hydrogenated tetrahedral amorphous carbon (ta-C:H)) which is formed by a plasma CVD method or the like. The subject of treatment by the present invention may also be a DLC film formed with a diamond structure (sp3 bonding), a graphite structure (sp2 bonding), or a mixed structure thereof. A film thickness of the DLC film is 0.5 μm to 2.0 μm.
(12) Surface Treatment
(13) Substantially spherical ejection particles are ejected against a region where dimples are to be formed on a surface of the DLC coated member described above so as to impact this region.
(14) Examples of the ejection particles, ejection apparatus, and ejection conditions employed when performing the above surface treatment are given below.
(15) (1) Ejection Particles
(16) For the substantially spherical ejection particles employed in the surface treatment method of the present invention, “substantially spherical” means that they do not need to be strictly “spherical”, and ordinary “shot” may be employed therefor. Particles of any non-angular shape, such as an elliptical shape and a barrel shape, are included in “substantially spherical ejection particles” employed in the present invention.
(17) Materials that may be employed for the ejection particles include both metal-based and ceramic-based materials. Examples of materials for metal-based ejection particles include steel, high-speed tool steels (HSS) (SKH), stainless steels (SUS), chromium boron steels (FeCrB), and the like. Examples of materials that may be employed for the ceramic-based ejection particles include alumina (Al.sub.2O.sub.3), zirconia (ZrO.sub.2), zircon (ZrSiO.sub.4), silicon carbide (SiC), glass, and the like.
(18) Regarding the particle diameter of the ejection particles employed, particles having a median diameter (D50) in a range of from 1 μm to 20 μm are employed.
(19) “Median diameter D50” refers to the diameter at a cumulative mass 50 percentile, namely, to a diameter that when employed as a particle diameter to divide a group of particles into two, results in the total mass of particles in the group of particles of larger diameter being the same as the total mass of particles in the group of particles of smaller diameter. This is the same definition as “particle diameter at a cumulative 50% point” in JIS R 6001 (1987).
(20) For fine powder ejection particles having a median diameter from 1 μm to 20 μm, the ejection particles can be imparted with the property of having a long falling time through air (caused to float in air) by selecting a material density of the ejection particles. Ejection particles having such properties readily ride on an airflow, and can be propelled with a velocity similar to the flow speed of the airflow.
(21) In the surface treatment method of the present invention, the ejection particles employed have a falling time in still air conditions of not less than 10 s/m. This enables the ejection particles to be ejected at substantially the same velocity as the flow speed of an airflow being ejected from an ejection nozzle of a blasting apparatus.
(22) With regard to the falling speed, for the same particle diameter, the falling time is longer, the lower the density of the material configuring the ejection particles. For iron-based ejection particles having a relative density of 7.85, the falling time is 10.6 s/m for a particle diameter of 20 μm, and 41.7 s/m for a particle diameter of 10 μm. For ceramic-based ejection particles having a relative density of 3.2, the falling time is 26.3 s/m for a particle diameter of 20 μm, and 100 s/m for a particle diameter of 10 μm.
(23) (2) Ejection Apparatus
(24) A known blasting apparatus for ejecting abrasive together with a compressed gas may be employed as the ejection apparatus to eject the ejection particles described above toward the surface of the region to be treated.
(25) Such blasting apparatuses are commercially available, such as a suction type blasting apparatus that ejects abrasive using a negative pressure generated by ejecting compressed gas, a gravity type blasting apparatus that causes abrasive falling from an abrasive tank to be carried by compressed gas and ejected, a direct pressure type blasting apparatus in which compressed gas is introduced into a tank filled with abrasive and the abrasive is ejected by merging the abrasive flow from the abrasive tank with a compressed gas flow from a separately provided compressed gas supply source, and a blower type blasting apparatus that carries and ejects the compressed gas flow from such a direct pressure type blasting apparatus with a gas flow generated by a blower unit. Any one of the above may be employed to eject the ejection particles described above.
(26) (3) Treatment Conditions
(27) Substantially spherical ejection particles configured from one of the materials described above or the like and having a median diameter D50 of from 1 μm to 20 μm and a falling time through air of not less than 10 s/m are ejected against the DLC coated member as described above at an ejection pressure of from 0.01 MPa to 0.7 MPa so as to form dimples without exposing the base material.
(28) The ejection of such ejection particles is performed against the surface of the DLC film until the total projected area of the dimples is not less than 50% of the treated region. Note that in the present specification the “projected area” means the area of the outlines of the dimples.
(29) Moreover, the ejection particles are ejected so that the surface roughness of the DLC surface after treatment is an arithmetic mean height Sa as defined by ISO 25178 lying within a range of from 0.01 μm to 0.1 μm.
(30) Moreover, this is performed so as to achieve a texture aspect ratio Str as defined by ISO 25178 of not less than 0.4, so as to work the surface of the DLC film to a non-directional surface.
Operation Etc
(31) The surface treatment method of the present invention as described above enables fine dimples to be formed on the DLC film at a total projected area of not less than 50% of the treated region without causing the DLC film to detach, and accordingly without exposing the base material.
(32) As a result, treating with the method of the present invention enables resistance during sliding to be reduced. This is achieved by reducing the area of contact between the DLC coated member having fine dimples formed on the surface of the DLC film and the opposing member.
(33) Moreover, the indentation-protrusion profile of the surface of the DLC coated member formed by the method of the present invention is a profile predominated by smooth indentations and protrusions. This means that the angles of slope of the indentations and protrusions are shallow, and a reduction is also achieved in the frictional force acting on the protrusions.
(34) Moreover, due to shallow dimples of small diameter being formed, an improvement in slidability is achieved due to obtaining an air lubrication effect by a layer of air being formed over the surface of the DLC film during sliding.
(35) Furthermore, the dimples formed also function as oil reservoirs, and so an improvement in slidability can also be achieved in both cases in which lubricating oil is applied to sliding portions, and also in cases in which none is applied.
EXAMPLES
(36) Next, the results will be given of comparative tests performed on the DLC coated members to which the surface treatment by the method of the present invention has been performed, and on untreated DLC coated members.
(37) A profile analyzing laser microscope (VK-X250, manufactured by Keyence Corporation) was employed to measure roughness as described below with measurements taken at a measurement magnification of 3000×. The analysis software applicable to this laser microscope (Multi-File Analysis Application VK-H1MX) was employed to compute the profile obtained thereby based on these analysis results.
Test Example 1: Aluminum-can-Forming Draw Die
(1) Test Method
(38) An aluminum-can-forming draw die on which the surface treatment by the method of the present invention has been performed, and an untreated aluminum-can-forming draw die were each employed to form 10,000 aluminum cans. After forming the cans therewith, the state of DLC film detachment from the surface of the aluminum-can-forming draw die and the state of aluminum adhesion thereto were then respectively evaluated by visual inspection.
(2) Examples and Comparative Example
(39) A cemented carbide aluminum-can-forming draw die was prepared by forming a DLC film with a film thickness of 0.5 μm on the surface of a base material after lap polishing the surface to an Ra of not more than 0.02 μm. The die surface was then subjected to the surface treatment method of the present invention under the conditions listed in Table 1 (Examples 1 to 3). These dies and an untreated cemented carbide aluminum can-forming draw die (Comparative Example 1) were then respectively employed to form aluminum cans.
(40) TABLE-US-00001 TABLE 1 Examples 1 to 3 and Comparative Example 1 Comparative Example 1 Example 2 Example 3 Example 1 Ejection apparatus LDQ-3 SFK-2 FDQ-3 Untreated manufactured by manufactured by manufactured by Fuji Manufacturing Fuji Manufacturing Fuji Manufacturing Co., Ltd Co., Ltd Co., Ltd Ejection Type Blower type Suction type Direct pressure type Ejection particle median Zirconia 16 Alumina 10 Steel alloy 4 diameter (μm) Ejection pressure (MPa) 0.03 0.1 0.3 Ejection velocity (m/s) 80 m/s or more 80 m/s or more 80 m/s or more Arithmetic mean height (Sa) 0.03 μm 0.04 μm 0.06 μm 0.01 μm Depth of dimple (μm) 0.2 μm or less 0.2 μm 0.4 μm 0 μm Texture aspect ratio (Str) 0.44 0.51 0.54 0.16
(3) Evaluation Results
(41) The laser microscope (VK-X250, manufactured by Keyence Corporation) mentioned above was employed for measurement, and the respective surface roughness profiles of the dies are illustrated in
(42) Electron micrographs imaging the surfaces of the respective dies are illustrated in
(43) Furthermore, the results listed in the following Table 2 were confirmed by visual inspection for the state of DLC film detachment and the state of aluminum adhesion after forming aluminum cans for the aluminum-can-forming draw dies of Examples 1 to 3 and for the aluminum-can-forming draw die of Comparative Example 1.
(44) TABLE-US-00002 TABLE 2 Confirmed Results of the State of DLC Film Detachment and Aluminum Adhesion Comparative Example 1 Example 2 Example 3 Example 1 Detachment of None None None Partial DLC film detachment Aluminum Very slight Very slight Slight Significant adhesion
(45) As is clear from a comparison with the surface of the untreated die (Comparative Example 1) illustrated in
(46) These dimples were formed to DLC with a film thickness 0.5 μm, and were all formed with a depth of not more than 0.2 μm. Thus the surface treatment method of the present invention was able to form dimples on the surface of the DLC coated member without exposing the base material of the die. This enabled the DLC film to be prevented from detaching with dimple formation positions acting as the origin thereof, as is the case when local detachment of the DLC film has been induced.
(47) Moreover, as is apparent from
(48) As a result, although partial detachment of the DLC film together with comparatively large aluminum adhesion occurred after forming aluminum cans with the aluminum-can-forming draw die not subjected to the surface treatment by the method of the present invention (Comparative Example 1), there was no detachment of the DLC film seen and there was only very slight or slight aluminum adhesion for the aluminum-can-forming draw die subjected to the surface treatment method of the present invention (Examples 1 to 3). Thus performing surface treatment with the surface treatment by the method of the present invention was confirmed to improve the mechanical properties in comparison to the untreated DLC coated member.
Test Example 2: Profile Punch
(1) Test Method
(49) A profile punch subjected to surface treatment by the method of the present invention and an untreated profile punch were respectively employed to die-cut electrical component material (brass material) 15,000 times. The state of DLC film detachment from the surface of the profile punches after use was then evaluated by visual inspection.
(2) Examples and Comparative Example
(50) A cemented carbide profile punch was prepared by forming a DLC film with a film thickness of 1.5 μm on the surface of a base material after lap polishing the surface to an Ra of not more than 0.02 μm. The cemented carbide profile punch was then subjected to the surface treatment method of the present invention under the conditions listed in Table 3 (Examples 4 to 6). These profile punches and an untreated cemented carbide profile punch (Comparative Example 2) were then respectively employed for punching.
(51) TABLE-US-00003 TABLE 3 Examples 4 to 6 and Comparative Example 2 Comparative Example 4 Example 5 Example 6 Example 2 Ejection apparatus SFK-2 LDQ-3 FDQ-3 Untreated manufactured by manufactured by manufactured by Fuji Manufacturing Fuji Manufacturing Fuji Manufacturing Co., Ltd Co., Ltd Co., Ltd Ejection Type Suction type Blower type Direct pressure type Ejection particle median Zirconia 15 Zircon 5 Glass 3 diameter (μm) Ejection pressure (MPa) 0.1 0.06 0.04 Ejection velocity (m/s) 80 m/s or more 80 m/s or more 80 m/s or more Arithmetic mean height (Sa) 0.04 μm 0.02 μm 0.56 μm 0.01 μm Depth of dimple (μm) 0.2 μm or less 0.15 μm or less 0.5 μm or less 0 μm Texture aspect ratio (Str) 0.61 0.45 0.54 0.14
(3) Evaluation Results
(52) The results seen for the state of DLC film detachment for the profile punches of Examples 4 to 6 and for the profile punch of Comparative Example 2 are listed in the following Table 4.
(53) TABLE-US-00004 TABLE 4 State of DLC Film Detachment Comparative Example 4 Example 5 Example 6 Example 2 DLC Film None None None Detachment at leading Detachment end of punch
(54) The above results confirmed that the DLC film at the leading end of the punch became detached after cutting out electrical component material with a profile punch not subjected to the surface treatment method of the present invention (Comparative Example 2).
(55) In contrast thereto, no DLC film detachment could be seen at any portion of the profile punches subjected to surface treatment by the method of the present invention (Examples 4 to 6), including at the leading end portions of the punches. This confirmed that performing surface treatment by the surface treatment method of the present invention improved the mechanical properties of the punches in comparison to the untreated DLC coated member.
Test Example 3: Component Transport Rail
(1) Test Method
(56) A component transport rail subjected to surface treatment by the method of the present invention (Example 7) and an untreated component transport rail (Comparative Example 3) were respectively employed to transport components. The presence or absence of catching of the transported components during transportation was then confirmed by visual inspection.
(2) Examples and Comparative Example
(57) A component transport rail made from SUS304 was prepared by forming a DLC film with a film thickness of 1.5 μm on the surface of a base material after lap polishing the surface to an Ra of not more than 0.02 μm. The component transport rail was then subjected to the surface treatment method of the present invention under the conditions listed in Table 5 (Example 7). This component transport rail and an untreated component transport rail (Comparative Example 3) were then respectively employed for component transport.
(58) TABLE-US-00005 TABLE 5 Example 7 and Comparative Example 3 Comparative Example 7 Example 3 Ejection apparatus SFK-2 Untreated manufactured by Fuji Manufacturing Co., Ltd Ejection Type Suction type Ejection particle median Steel alloy 15 diameter (μm) Ejection pressure (MPa) 0.2 Ejection velocity (m/s) 80 m/s or more Arithmetic mean height (Sa) 0.03 μm 0.01 μm Depth of dimple (μm) 0.2 μm or less 0 μm Texture aspect ratio (Str) 0.48 0.14
(3) Evaluation Results
(59) The results of the state of catching of transported components for the component transport rail of Example 7 and for the component transport rail of Comparative Example 3 confirmed by visual inspection are listed in Table 6 below.
(60) TABLE-US-00006 TABLE 6 Catching of Transported Components Comparative Example 7 Example 3 Catching of transported components None Some
(61) The above results confirmed that catching of transported components occurred with the component transport rail (Comparative Example 3) not subjected to the surface treatment method of the present invention. Catching at these portions is thought to be due to cracks and detachment developing in the DLC film.
(62) In contrast thereto, for the component transport rail (Example 7) subjected to surface treatment by the method of the present invention, no catching of transported components could be seen, and confirmation was made that cracks and detachment did not develop in the DLC film, and good slidability was exhibited thereby.
(63) Thus the broadest claims that follow are not directed to a machine that is configured in a specific way. Instead, said broadest claims are intended to protect the heart or essence of this breakthrough invention. This invention is clearly new and useful. Moreover, it was not obvious to those of ordinary skill in the art at the time it was made, in view of the prior art when considered as a whole.
(64) Moreover, in view of the revolutionary nature of this invention, it is clearly a pioneering invention. As such, the claims that follow are entitled to very broad interpretation so as to protect the heart of this invention, as a matter of law.
(65) It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
(66) It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.
(67) Now that the invention has been described;