Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D37/00—Tools as parts of machines covered by this subclass
  • B21D37/01—Selection of materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/20—Deep-drawing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D24/00—Special deep-drawing arrangements in, or in connection with, presses
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/0021—Reactive sputtering or evaporation
  • C23C14/0036—Reactive sputtering
  • C23C14/0057—Reactive sputtering using reactive gases other than O2, H2O, N2, NH3 or CH4
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/02—Pretreatment of the material to be coated
  • C23C14/024—Deposition of sublayers, e.g. to promote adhesion of the coating
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
  • C23C14/0605—Carbon
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering

Definitions

• the present invention relates to a forming tool for hot forming of Zn-plated steel sheets.
• the present invention particularly relates to a forming tool which is used in performing a hot pressing, after a Zn-plated steel sheet is heated at a high temperature in the austenite range.
• the hot pressing is referred to also as hot stamping, die quenching, press quenching, or hot pressing.
• the hot pressing method has problems such as the following.
• the hot pressing method is a technique in which a blank that is a steel sheet is heated usually to a temperature range of austenite of 800 to 900° C. and then rapidly cooled and simultaneously formed into a desired part shape by means of a water-cooled forming tool.
• the steps from the heating of the steel sheet to the pressing are conducted in the air from the standpoint of cost. Consequently, for the purpose of inhibiting scale formation due to steel sheet oxidation, a Zn-plated steel sheet which has a plated layer consisting mainly of
• Zn formed on the surfaces thereof is often used as that steel sheet.
• the Zn softens during the high-temperature forming. Because of this, in the cases when the Zn-plated steel sheet is used as a blank, the softened Zn adheres to the forming tool for pressing as the number of pressing shots increases. In the case where this adhesion of Zn is serious, the shape of the forming tool is changed, arousing problems concerning product shape and the surface quality of the formed steel sheet.
• Zn adhesion the adhesion of Zn to a forming tool is sometimes referred to simply as “Zn adhesion”.
• a ceramic coating film of, for example, TiN is formed as a coating on the surfaces of the forming tools as a measure against wear by abrasion with steel sheets.
• the ceramic coating film is not considered to be sufficient for inhibiting the Zn adhesion to the forming tools.
• examples of techniques for inhibiting the adhesion of a soft metal to forming tools include the following techniques of Patent Document 1 and Patent Document 2.
• Patent Document 1 discloses a cold-pressing apparatus for magnesium alloy materials, in which cold pressing of a magnesium alloy material can be carried out at room temperature successively and continuously without causing a trouble to the tool surface of the press-forming tool and in the state of capable of mass production. Specifically, the document shows that a superhard film has been formed by a coating treatment on the tool surface of the press-forming tool. It also shows that the superhard film is constituted of one kind or two more kinds selected from among TiN, TiCN, CrN, TiAlN, Al 2 O 3 , and DLC (diamond like carbon).
• Patent Document 2 discloses, in a forming of magnesium alloy member, a method for forming a formed product easily and at low cost while avoiding fusion bonding to the forming tool even when neither a lubricant nor a sheet-shaped member is used. Specifically, the document discloses a method in which at least a part of the portion to be in contact with the magnesium alloy member in the forming tool is coated with a diamond film and the surface of the diamond film is polished to a maximum surface roughness of 0.1 ⁇ m or more and 1.0 ⁇ m or less, and in which pressing is conducted so that the diamond film of the forming tool after polishing comes into direct contact with the magnesium alloy member.
• Patent Document 1 mentions coating films of nitrides such as TiN and TiAlN, together with DLC, and indicates that these nitride coating films are effective in adhesion inhibition. In the case of Zn, however, such nitride coating films have no effect of inhibiting the adhesion, as will be demonstrated in the
• Patent Document 1 JP-A-2003-154418
• Patent Document 2 JP-A-2009-172640
• An object of the present invention which has been achieved by focusing on the circumstances described above, is to realize a forming tool which is for use in a hot forming of a Zn-plated steel sheet and to which the Zn of the Zn-plated steel sheet is less apt to adhere.
• the property whereby “the Zn of the Zn-plated steel sheet is less apt to adhere” is sometimes referred to as “Zn adhesion resistance”.
• the forming tool for a hot forming of the present invention which has overcome the problem, is a forming tool for use in a hot forming of a Zn-plated steel sheet, in which at least a portion to be in contact with the Zn-plated steel sheet during the hot forming in the forming tool is covered with an amorphous-carbon coating film that satisfies all of the following (1) to (4).
• a film thickness is 0.5 ⁇ m or larger
• a surface has an arithmetic mean roughness Ra of 2.0 ⁇ m or less
• (4) a hydrogen content is 30 atom % or less.
• the amorphous-carbon coating film has a skewness Rsk in the surface thereof of a negative value.
• the amorphous-carbon coating film may contain at least one metallic element of W and Si, in a total of up to 20 atom% in a proportion to all elements
• the amorphous-carbon coating film has a hydrogen content of 5 atom % or higher.
• bonds of carbon constituting the amorphous-carbon coating film have a proportion of sp2 bonds equal to or larger than a proportion of sp3 bonds.
• a forming tool which is for use in a hot forming of a Zn-plated steel sheet and to which the Zn of the Zn-plated steel sheet is less apt to adhere in the hot forming.
• the present inventor diligently made investigations in order to solve the problem. As a result, the inventor has found that in the cases when, in a forming tool to be used for a hot-forming of a Zn-plated steel sheet, at least a portion thereof to be in contact with the Zn-plated steel sheet during the hot forming is covered with a coating film in which control elements that are divided roughly into the following two are within specified ranges, then the Zn adhesion to the forming tool surface is remarkably inhibited when the forming tool comes into contact with the Zn of the Zn-plated steel sheet.
• the present invention has been thus completed.
• the first control element is the surface profile of the coating film. Since the Zn-plated steel sheet is heated to a high temperature and formed in hot pressing as stated above, the Zn present in the surface of the Zn-plated steel sheet which is in contact with the forming tool has softened. In the cases when the surface of the forming tool has a shape with projections, Zn transfers and adheres to the forming tool surface due to the Zn-digging effect by the projections. Consequently, in the present invention, it has been first found that for inhibiting the digging and the accompanying transfer and adhesion of Zn, it is necessary that the arithmetic mean roughness Ra of the surface should satisfy 2.0 ⁇ m or less.
• the Ra is preferably 1.0 ⁇ m or less and more preferably 0.5 ⁇ m or less. The smaller the Ra, the more preferred. For example, it can be reduced to about 0.01 ⁇ m, which indicates a supermirror surface.
• the regulation of Ra alone is not sufficient for inhibiting Zn adhesion, and it is necessary that the root-mean-square slope R ⁇ q of the surface should also be regulated.
• the R ⁇ q indicates the slope of roughness, and there is a tendency that the smaller the R ⁇ q, the gentler the slope. It has been found that by regulating the R ⁇ q to 0.50° or less along with the Ra, Zn adhesion can be inhibited without fail in the present invention.
• the R ⁇ q is preferably 0.10° or less and more preferably 0.05° or less. The smaller the R ⁇ q, the more preferred. However, a lower limit of R ⁇ q is about 0.001° when producibility, etc. are taken into account.
• Zn is a metal which is highly prone to adhere, as stated above. Physical control, such as controls of roughness and surface state, is not sufficient for inhibiting the adhesion of Zn. Consequently, from the standpoint of reducing reactivity with Zn when in contact with Zn, it is necessary that the material of the surface to be in contact with Zn should be investigated as the second element to be controlled.
• the present inventor from this standpoint, has discovered that amorphous-carbon coating films are suitable as substances showing reduced reactivity with Zn, and that among those, an amorphous-carbon coating film which has a hydrogen content, i.e., a proportion of hydrogen to the sum of carbon and hydrogen, of 30 atom % or less is suitable.
• the amorphous-carbon coating film is hereinafter sometimes referred to as DLC film.
• the hydrogen content of the DLC film exceeds 30 atom %, this DLC film has reduced heat resistance to show a considerable alteration or deterioration due to the heat during the forming. As a result, Zn adhesion is prone to occur.
• the hydrogen content is preferably 25 atom % or less and more preferably 10 atom % or less. Meanwhile, in the case where hydrogen is not contained at all, there is a tendency that Zn adhesion is rather enhanced. It is hence preferable that the hydrogen content is 5 atom % or higher.
• the value of skewness Rsk which is a parameter indicating the asymmetry between the recesses and protrusions of the surface to be in contact with Zn, is negative.
• the skewness Rsk is more preferably ⁇ 1 or less.
• a lower limit of the skewness Rsk is about ⁇ 10.
• the arithmetic mean roughness Ra is the arithmetic mean roughness Ra regarding contour curve, among the height-direction parameters defined in JIS B 0601 (2013).
• the root-mean-square slope R ⁇ q is the root-mean-square slope regarding contour curve which is a combined parameter as defined in the same JIS, and the skewness Rsk is the skewness Rsk regarding contour curve, among the height-direction parameters defined in the same JIS.
• the definition of each parameter and a method for determination thereof are based on the description of JIS B 0601 (2013).
• the DLC film according to the present invention may contain at least one metallic element of W and Si.
• the proportion of the metallic element(s) to the sum of carbon, hydrogen if hydrogen is contained, and the metallic element(s) is 0.5 atom % or higher.
• the expression “proportion of the metallic elements(s)” means the amount added alone when the metallic element is contained alone, and means the total amount when the two elements are contained. The same applies hereinafter.
• the proportion of the metallic element(s) is more preferably 1.0 atom % or higher, even more preferably 2.0 atom % or higher and especially preferably 5.0 atom % or higher.
• the proportion of the metallic element(s) is preferably 20 atom % or less and more preferably 10 atom % or less.
• the expression “hydrogen content of the DLC film” means the proportion of hydrogen (atom %) to the sum of carbon, hydrogen and the metallic element(s).
• DLC is an amorphous inorganic substance which has intermediate properties between diamond and graphite.
• Diamond is constituted only of sp3 hybridized orbital and graphite is constituted only of sp2 hybridized orbital, whereas DLC is considered to include both carbon atoms which show properties of diamond and carbon atoms which show properties of graphite.
• the properties of DLC are governed by the ratio between sp2 bonds which are graphitic bonds and sp3 bonds which are diamond-like bonds, in the coating film.
• the proportion of each kind of bonds in the DLC film can be determined by a method such as electron energy-loss spectroscopy (EELS).
• the film thickness of the DLC film according to the present invention is 0.5 ⁇ m or larger. This is because in the case where the film thickness is less than 0.5 ⁇ m, there are cases where the covering is insufficient and the substrate is exposed.
• the film thickness is preferably 1.0 ⁇ m or larger. Meanwhile, in the case where the film thickness of the DLC film is too large, peeling is prone to occur. It is therefore preferable that the film thickness of the DLC film is 10 ⁇ m or less. It is more preferably 5 ⁇ m or less.
• the forming tool is one in which at least a portion to be in contact with the Zn-plated steel sheet during hot forming is covered with the DLC coating film specified in the present invention, the covering of portions thereof not to be in contact with the Zn-plated steel sheet is not particularly limited.
• the forming tool of the present invention is not limited so long as the outermost surface thereof is constituted of the DLC film specified in the present invention.
• a film constituted of, for example, CrN, TiN or the like or any of a film of metallic Cr, a film of metallic W, a gradient layer in which the composition changes gradually from W to C, and the like, which are shown in the Examples given later, may have been formed as an interlayer between the DLC film constituting the outermost surface and the substrate.
• Examples of the forming tool of the present invention for the hot forming of a Zn-plated steel sheet include dies, punches and pads.
• Examples of the Zn-plated steel sheet include hot-dip galvanized steel sheets, hot-dip galvannealed steel sheets and electrogalvanized steel sheets.
• Methods for forming the DLC film specified in the present invention are not particularly limited.
• vapor deposition methods such as chemical vapor deposition (CVD), e.g., plasma chemical vapor deposition, and physical vapor deposition (PVD), e.g., arc ion plating and sputtering. These may be used alone or in combination.
• CVD chemical vapor deposition
• PVD physical vapor deposition
• a DLC film may be deposited by using a graphite target while introducing a hydrocarbon gas such as methane or acetylene during the deposition.
• a recommended method is to use a hydrocarbon gas, such as methane, acetylene or toluene, and apply DC bias or RF bias thereto to directly ionize it, thereby depositing a DLC film.
• a hydrocarbon gas such as methane, acetylene or toluene
• Preferred film deposition methods are sputtering methods. More preferred of these is un-balanced magnetron sputtering (UBMS).
• UBMS un-balanced magnetron sputtering
• the UBMS conditions may be, for example, a substrate temperature of room temperature to 400° C., a total gas pressure of 0.5 to 5 Pa, a negative bias voltage in DC mode of 100 to 1,600 V, a positive/negative bias voltage in AC mode of 100 to 1,600 V, and a voltage supply to the carbon target of 0.1 to 3.0 kW.
• the pure metal(s) constituted of the metallic element(s) or a carbide or the like of the metallic element(s) can be used as a target together with the carbon target.
• the Si it is also possible to use an Si-containing gas, such as SiH 4 , as a film deposition gas.
• Examples of methods for attaining a hydrogen content in the DLC film of 30 atom % or less include regulating the flow rate of a hydrocarbon gas, e.g., methane that is caused to flow during the process.
• examples include to increase the bias voltage and to elevate the substrate temperature
• Examples of methods for obtaining a DLC film in which the proportion of sp2 bonds in the bonds of the carbon constituting the DLC film is equal to or higher than the proportion of sp3 bonds include to regulate the voltage being applied to the substrate during the film deposition.
• Examples of methods for regulating so that the Ra, R ⁇ q and Rsk specified in the present invention are satisfied include polishing the surface of a DLC film formed by the method described above, for example, with a projection type polishing apparatus while changing the conditions including projection period and projection pressure. There is a tendency that as the projection period is made longer and the projection pressure is made higher, the factors Ra, R ⁇ q and Rsk each become smaller. The polishing may be performed while ascertaining the value of each factor.
• the surface has high roughness
• large irregularities such as grinding flaws are removed in advance by a method such as buffing, and then the projection polishing is performed.
• a method such as buffing
• examples thereof include using diamond particles (abrasive grains) having an average particle diameter of 4 to 8 ⁇ m which are for use in mirror polishing as an abrasive material in order to carry out the polishing with only a slight polishing amount.
• devices for projecting such an abrasive material include AERO LAP (registered trademark; Yamashita Works Co., Ltd.).
• Another method for regulation for satisfying the Ra, R ⁇ q and Rsk is to regulate the surface roughness of the substrate before a DLC film is formed.
• the methods described above for regulating the surface roughness of the DLC film can be applied to methods for regulating the surface roughness of the substrate.
• the roughness of the surface of the substrate before being covered with a DLC film is not necessarily regulated so as to fall in the Ra, R ⁇ q and Rsk ranges for the DLC film.
• Examples include a method in which the substrate surface is processed, for example, by shot blasting or the like to regulate the Ra of the substrate surface to, for example, fall in the range of Ra 1.5 ⁇ m ⁇ 20% and a DLC film is thereafter formed on the substrate surface in the manner described above.
• the substrate surface may be further polished, for example, by projection polishing in order to remove sharp angles formed by the shot blasting, so long as the shape of the substrate surface does not change considerably.
• the surface roughness of the substrate is regulated and a DLC film is then formed, for example, projection polishing may be given to the surface of the DLC film for the purpose of further regulating the surface roughness of the DLC film, removing particles adherent to the surface or the like.
• the roughness of the surface of the interlayer may be regulated so as to be similar to the roughness of the substrate.
• Example 1 the influences of the composition and hydrogen content of a coating film on Zn adhesion resistance were examined.
• a coating film formed on a substrate surface is often referred to as a coating.
• a mirror-surface substrate constituted of SKD11 and having an HRC of 60 and a substrate Ra of 0.005 ⁇ m was prepared as a substrate for evaluating the surface profile of a coating.
• a mirror-surface bending tool constituted of SKD61 and having a substrate Ra of 0.01 to 3 ⁇ m was prepared for evaluating Zn adhesion resistance.
• As a coating each of coating films of nitrides, i.e., TiN, CrN and TiAlN, as conventional coating films, DLC films having the hydrogen contents shown in Table 1, and the DLC films containing Si or W as shown in Table 1 was formed on a surface of the substrate.
• the film deposition conditions for the un-balanced magnetron sputtering method included a substrate temperature of 200° C., a total gas pressure of 0.6 Pa, an electric power input of 3 kW, and a target size of 6 inches in diameter.
• As a film deposition gas was used a mixed gas of methane gas and argon. Each film was formed for about 1 to 3 ⁇ m on the surface of the substrate. Regulation of the hydrogen contents of the DLC films was carried out by changing the amount of the methane gas or the bias voltage applied to the substrate.
• each DLC film in order to improve adhesion to the iron-based substrate, an interlayer constituted of metallic Cr was deposited on the substrate, an interlayer constituted of metallic W was thereafter deposited, a gradient layer was subsequently formed in which the composition changed gradually from W to C, and the DLC film was then formed on the gradient layer.
• the DLC film containing Si or W was formed by using either the pure metal of that metallic element or a carbide or the like of the metallic element as a target together with the carbon target or by using SiH 4 as a film deposition gas in the case of Si.
• Example 1 an apparatus AERO LAP (registered trademark), manufactured by Yamashita Works Co., Ltd., was used as a projection type polishing apparatus after the coating to polish the coating surface.
• Ra, R ⁇ q and Rsk of all the coatings were made to be equal as will be shown later.
• the samples thus obtained were used to evaluate the surface properties in the following manner, and a Zn adhesion evaluation test simulating hot stamping was conducted to evaluate Zn adhesion resistance.
• the Ra of each sample was measured by using a stylus type surface roughness meter (DekTak 6M).
• a scanning length was set to be 1 mm and the number of horizontal-direction measuring points was set to be 3,900 to measure a surface curve, from which a roughness curve was obtained by removing undulations therefrom.
• Ra, R ⁇ q and Rsk were calculated from the roughness curve in accordance with JIS B 0601 (2013). These were measured at arbitrary five points on the surface, and average values thereof were employed.
• Ra was 0.1 ⁇ m
• R ⁇ q was 0.02°
• Rsk was ⁇ 1.0, in all the samples.
• a hot-dip galvanized steel sheet was prepared as a sheet material which is a blank.
• the bending tools having the various coatings formed on the surfaces thereof were used to conduct bending of the galvanized steel sheet which had been heated, under the following forming conditions. Zn adhesion state in the surface of the forming tool after the bending was examined.
• Blank hot-dip galvanized steel sheet having tensile strength of 590 MPa and sheet thickness of 1.4 mm
• Heating temperature 760° C.
• the Zn adhesion resistance was evaluated in the following manner. First, the surface roughness change (Ra) was measured before and after the Zn adhesion evaluation test, and the proportion of the change of the absolute value of Ra, i.e., [100 ⁇ (Ra before the adhesion test) ⁇ (Ra after the adhesion test) ⁇ /(Ra before the adhesion test)], was determined, and the evaluation was performed in four grades, i.e., 0 to 3, as follows. The case where the grade was 2 or less was regarded as acceptable. In particular, the case where the grade was 1 or less, i.e., 1 or 0, was evaluated as having better Zn adhesion resistance. The results thereof are shown in the column “Evaluation of Zn adhesion resistance” in Table 1.
• the DLC films satisfying a hydrogen content of 30 atom % or less showed excellent Zn adhesion resistance as in Nos. 4 to 8.
• the hydrogen content is more preferably 10 atom % or more and 25 atom % or less, sufficiently excellent Zn adhesion resistance is exhibited.
• the Zn adhesion resistance was rather poor, as in No. 9.
• Nos. 10 to 13 are examples of the DLC film containing at least one element of W and Si.
• the DLC films which satisfied a hydrogen content of 30 atom % or less and contained at least one element of W and Si in the specified amount showed excellent Zn adhesion resistance, as in Nos. 10 and 11.
• the Zn adhesion resistance was poor, as in Nos. 12 and 13.
• Example 2 the influence of the surface profile of a DLC film on Zn adhesion resistance was examined.
• Example 1 Samples were produced in the same manner as in Example 1, except that a substrate was coated with a DLC film having a hydrogen content of 10 atom % and the Ra, R ⁇ q and Rsk were changed as shown in Table 2.
• Example 1 and Example 3 which will be given layer, a substrate having a mirror surface was used.
• the roughness of the substrate was varied by the method described above, and a DLC film was formed thereon.
• samples which varied in the Ra, R ⁇ q and Rsk were prepared.
• a Zn adhesion evaluation test was conducted in the same manner as in Example 1 to evaluate Zn adhesion resistance. The results thereof are shown in Table 2.
• Example 3 the influence of the proportion of sp2 bonds in a DLC film on Zn adhesion resistance was examined.
• Samples were produced in the same manner as in Example 1, except that one of the coating films was formed by the arc ion plating (AIP) method and that the voltage which was applied to the substrate during film deposition by the AIP method or UBMS method was changed to thereby form DLC films differing in the proportion of sp2 bonds as shown in Table 3.
• the hydrogen content was regulated in the same manner as in Example 1.
• the film deposition conditions for the arc ion plating method included a substrate temperature of 400° C., a total gas pressure of 4 Pa and a bias voltage of ⁇ 50 V.
• a Zn adhesion evaluation test was conducted in the same manner as in Example 1 to evaluate Zn adhesion resistance.
• the proportion of sp2 bonds was ascertained by EELS analysis.
• the measurement conditions for the EELS analysis are as follows.

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• 2014
  • 2014-04-22 JP JP2014088271A patent/JP6211987B2/ja not_active Expired - Fee Related
• 2015
  • 2015-04-22 EP EP15783193.4A patent/EP3135395A4/en not_active Withdrawn
  • 2015-04-22 WO PCT/JP2015/062310 patent/WO2015163386A1/ja active Application Filing
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