Covering material

Abstract

To enhance the durability of a coated member.SOLUTION: A coated member has a base material and a hard film formed on a surface of the base material and including nitride or carbonitride of a metal element, and contains 65-85 atm% of Al, 15-35 atm% of Cr, and 90-100 atm% in total of Al and Cr for the total content of the metal element and a metalloid element contained in the hard film. In an intensity profile found from a limited visual field diffraction pattern through a transmission type electron microscope, crystal planes showing maximum peak intensities are different nearby the base material and nearby the surface, a peak corresponding to a (111) plane or (200) plane of a face-centered cubic lattice structure shows maximum intensity nearby the base material nearby the base material.and the peak intensity corresponding to a (220) plane of the face-centered cubic lattice structure is 0.6 time or larger as large as a peak intensity larger between the peak intensities corresponding to the (200) plane and (111) plane of the face-centered cubic structure nearby the surface.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a coated member that is applied to a mold, a cutting tool, or the like. [Background technology]

[0002] AlCr nitride is a film type with excellent wear resistance and heat resistance, and is widely used as a coating for coated members such as dies, cutting tools, etc. In recent years, coated members coated with Al-rich AlCr nitride, in which the Al content ratio in the metal component exceeds 70 atomic %, by arc ion plating have been proposed (Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-032861 [Patent Document 2] Japanese Patent Application Publication No. 2018-059146 [Patent Document 3] Japanese Patent Publication No. 2020-040175 Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have confirmed that there is room for improvement in durability in cutting hardened steel for coated members provided with a conventional coating containing Al-rich AlCr nitride.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coated member having a coating containing Al-rich AlCr nitride and having excellent durability. [Means for solving the problem]

[0006] The present invention provides a coated member having a substrate and a hard coating formed on a surface of the substrate, the hard coating contains a nitride or a carbonitride of a metal element, the aluminum (Al) content is 65 atomic % or more and 85 atomic % or less, the chromium (Cr) content is 15 atomic % or more and 35 atomic % or less, and the total content of the aluminum (Al) and chromium (Cr) is 90 atomic % or more and 100 atomic % or less, in the total amount of the metal elements and metalloid elements contained in the hard coating; the hard coating has a crystal plane exhibiting a maximum peak intensity in the vicinity of the substrate and in the vicinity of the surface in an intensity profile determined from a selected area diffraction pattern of a transmission electron microscope, In the vicinity of the substrate, a peak corresponding to the (111) plane or the (200) plane of the face-centered cubic lattice structure exhibits maximum intensity, Near the surface, the peak corresponding to the crystal plane of the face-centered cubic lattice structure exhibits the maximum intensity, and the peak intensity corresponding to the (220) plane of the face-centered cubic lattice structure is 0.6 times or more the larger of the peak intensities corresponding to the (200) plane and the (111) plane of the face-centered cubic lattice structure. [Effects of the Invention]

[0007] According to the present invention, a coated member having excellent durability can be obtained. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of a selected area diffraction pattern of the hard coating in the vicinity of the substrate according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of an intensity profile obtained from the selected area diffraction pattern of FIG. [Figure 3] FIG. 3 is a diagram showing an example of a selected area diffraction pattern near the surface of the hard coating according to the first example. [Figure 4] FIG. 4 is a diagram showing an example of an intensity profile obtained from the selected area diffraction pattern of FIG. [Figure 5] FIG. 5 is a diagram showing an example of an intensity profile obtained from a selected area diffraction pattern of the hard coating in the vicinity of the substrate according to Example 2. [Figure 6]FIG. 6 is a diagram showing an example of an intensity profile obtained from a selected area diffraction pattern near the surface of the hard coating according to Example 2. [Figure 7] FIG. 7 is a diagram showing an example of an intensity profile obtained from a selected area diffraction pattern of the hard coating in the vicinity of the substrate according to Example 3. [Figure 8] FIG. 8 is a diagram showing an example of an intensity profile obtained from a selected area diffraction pattern near the surface of the hard coating according to Example 3. [Figure 9] FIG. 9 is a diagram showing an example of an intensity profile obtained from a selected area diffraction pattern of the hard coating in the vicinity of the substrate according to Example 4. [Figure 10] FIG. 10 is a diagram showing an example of an intensity profile obtained from a selected area diffraction pattern near the surface of the hard coating according to Example 4. [Figure 11] FIG. 11 is an example of a photograph (×180,000 magnification) of the structure of the hard coating according to Example 1, observed from the direction of film thickness growth near the substrate. [Figure 12] FIG. 12 is an example of a photograph (×120,000 magnification) of the structure of the hard coating according to Example 1, observed from the direction of film thickness growth near the surface. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present inventors have discovered that the durability of a coated member, in which the surface of a substrate is coated with a hard coating containing an Al-rich Al and Cr nitride or carbonitride, can be improved by controlling the crystal structure of the hard coating near the substrate and near the surface. Hereinafter, details of embodiments of the present invention will be described.

[0010] The coated member of this embodiment has a substrate and a hard coating formed on the surface of the substrate, the hard coating containing nitrides or carbonitrides of metal elements. The aluminum (Al) content of the hard coating is 65 atomic % to 85 atomic %, the chromium (Cr) content is 15 atomic % to 35 atomic %, and the total content of aluminum (Al) and chromium (Cr) is 90 atomic % to 100 atomic % of the total amount of metal and metalloid elements. The hard coating exhibits an intensity profile obtained from a selected-area diffraction pattern obtained using a transmission electron microscope. The crystal planes exhibiting the maximum peak intensity near the substrate and near the surface differ, and the peaks corresponding to the (111) or (200) plane of the face-centered cubic lattice structure exhibit the maximum intensity near the substrate. Near the surface, the peak corresponding to the crystal plane of the face-centered cubic lattice structure shows the maximum intensity, and the peak intensity corresponding to the (220) plane of the face-centered cubic lattice structure is 0.6 times or more the larger of the peak intensities corresponding to the (200) plane and the (111) plane of the face-centered cubic lattice structure. The coated member of this embodiment can be applied to molds and cutting tools.

[0011] <Base material> In this embodiment, the substrate is not particularly limited. Cold work tool steel, hot work tool steel, high speed steel, cemented carbide, etc. may be used as appropriate depending on the application. The substrate may be previously subjected to nitriding treatment or metal bombardment treatment, etc. Furthermore, it may be mirror-finished by lapping, etc.

[0012] <Hard coating> (Aluminum (Al), Chromium (Cr)) The hard coating according to this embodiment contains nitrides or carbonitrides of metal elements, and of the total amount of metal elements and metalloid elements (hereinafter, "metal elements and metalloid elements" will also be collectively referred to simply as "metal elements") contained in the hard coating, the aluminum (Al) content is 65 atomic % or more and 85 atomic % or less, the chromium (Cr) content is 15 atomic % or more and 35 atomic % or less, and the total content of aluminum (Al) and chromium (Cr) is 90 atomic % or more and 100 atomic % or less.

[0013] Nitrides or carbonitrides primarily composed of Al and Cr are film types that offer an excellent balance between wear resistance and heat resistance, and also have excellent adhesion to the substrate. In particular, increasing the Al content in the nitrides or carbonitrides improves the heat resistance of the hard coating. In addition, increasing the Al content facilitates the formation of an oxidation protective film on the surface of the hard coating, and the coating structure becomes finer, making it easier to suppress wear of the hard coating due to welding.

[0014] In the hard coating according to this embodiment, the Al content of the total amount of metal elements is set to 65 atomic % or more. In other words, when all the metal elements contained in the hard coating are taken as 100 atomic %, the Al content is set to 65 atomic % or more. This allows the above-mentioned effect of adding Al to be fully exerted. Preferably, the Al content is set to 68 atomic % or more. On the other hand, if the Al content is too high, the amount of AlN with a hexagonal close-packed (hcp) structure increases too much, significantly reducing the toughness of the hard coating. Therefore, in the hard coating according to this embodiment, the Al content of the total amount of metal elements is set to 85 atomic % or less. In other words, when all the metal elements contained in the hard coating are taken as 100 atomic %, the Al content is set to 85 atomic % or less. Preferably, the Al content is set to 82 atomic % or less.

[0015] The hard coating according to this embodiment has a Cr content of 15 atomic % or more relative to the total amount of metal elements. In other words, when the total amount of metal elements contained in the hard coating is taken as 100 atomic %, the Cr content is 15 atomic % or more. This facilitates the formation of a uniform and dense oxidation protective film on the surface of the hard coating of the coated member during use of a mold using the coated member or during machining with a cutting tool, thereby making it easier to suppress damage to the hard coating. Preferably, the Cr content is 18 atomic % or more. On the other hand, if the Cr content in the hard coating is too high, it becomes difficult to obtain the effects achieved by increasing the Al content. Therefore, the hard coating according to this embodiment has a Cr content of 35 atomic % or less relative to the total amount of metal elements. In other words, when the total amount of metal elements contained in the hard coating is taken as 100 atomic %, the Cr content is 35 atomic % or less. Preferably, the Cr content is 32 atomic % or less.

[0016] In the hard coating according to this embodiment, the total content of Al and Cr in the total amount of metal elements is 90 atomic % or more and 100 atomic % or less. In other words, if the total amount of metal elements contained in the hard coating is 100 atomic %, the total amount of Al and Cr is 90 atomic % or more and 100 atomic % or less. This ensures excellent durability of the coated member. Preferably, the total amount of Al and Cr is 95 atomic % or more.

[0017] The hard coating according to this embodiment contains nitrides or carbonitrides of the metal elements described above. Of nitrides and carbonitrides, the hard coating according to this embodiment is preferably a nitride, which has better heat resistance.

[0018] The content ratio of metal elements in the hard coating according to this embodiment can be measured by using an electron probe microanalyzer (EPMA) on the mirror-finished hard coating. In this case, for example, after mirror-finishing the hard coating surface, the content ratio can be determined from the average of five analysis points each having a diameter of about 1 μm.

[0019] (Metal elements other than aluminum (Al) and chromium (Cr)) The hard coating according to this embodiment may contain metal elements other than Al and Cr. For example, the hard coating according to this embodiment may contain one or more metal elements selected from the group 4a, 5a, and 6a of the periodic table (groups 4, 5, and 6, respectively, in the long-form periodic table) and Si, B, Y, Yb, and Cu, for the purpose of improving properties such as wear resistance, heat resistance, and durability (hereinafter also referred to as "coating properties"). Among these elements, Si and B are examples of metalloid elements. These elements are generally contained in coatings for coated members to improve the coating properties of the coated member. Metal elements other than Al and Cr may be contained within a range that does not significantly reduce the durability of the coated member. However, if the content ratio of metal elements other than Al and Cr is too high, the durability of the coated member may be reduced. Therefore, when the hard coating according to this embodiment contains metal elements other than Al and Cr, the total content ratio of these elements is preferably 10 atomic % or less, where 100 atomic % is taken as the total metal elements contained in the hard coating.

[0020] (crystal structure) In the evaluation of the crystalline structure of the hard coating according to this embodiment, an intensity profile obtained from a selected-area diffraction pattern obtained using a transmission electron microscope is used. This intensity profile can be obtained from a selected-area diffraction pattern obtained using a transmission electron microscope for a processed cross section of the hard coating. Specifically, the brightness of the selected-area diffraction pattern of the hard coating is converted into intensity, and an intensity profile is created with the horizontal axis representing the distance (radius r) from the center of the (000) plane spot and the vertical axis representing the integrated intensity (arbitrary units) for one circumference at each radius r. The intensity profile thus obtained from the selected-area diffraction pattern is used to evaluate the crystalline structure of the hard coating. In this embodiment, the crystalline structure of the hard coating is evaluated using an intensity profile created by removing background intensity.

[0021] In the hard coating according to this embodiment, the crystal planes exhibiting the maximum peak intensity near the substrate and near the surface are different in the intensity profile obtained from the selected area diffraction pattern of a transmission electron microscope. This means that the crystal structure and grain size of the hard coating change from near the substrate toward near the surface. This improves the wear resistance of the hard coating near the surface while ensuring adhesion between the substrate and the hard coating. In this embodiment, the vicinity of the substrate of the hard coating refers to a range within 0.5 μm from the interface between the substrate and the hard coating in the film thickness direction. In this embodiment, the vicinity of the surface of the hard coating refers to a range within 0.5 μm deep from the surface of the hard coating.

[0022] In the intensity profile obtained from the selected area diffraction pattern of a transmission electron microscope in the vicinity of the substrate of the hard coating according to this embodiment, the peak corresponding to the (200) or (111) plane of the face-centered cubic lattice structure shows the maximum intensity, thereby improving the adhesion between the substrate and the hard coating.

[0023] Near the surface of the hard coating according to this embodiment, the peak intensity corresponding to the crystal plane of the face-centered cubic lattice structure exhibits the maximum intensity. The crystal plane of the face-centered cubic lattice structure is selected from the (200), (111), and (220) planes. When at least one of these crystal planes exhibits the maximum intensity, the durability of the hard coating is improved.

[0024] In the vicinity of the surface of the hard coating according to this embodiment, the peak intensity corresponding to the (220) plane of the face-centered cubic lattice structure is at least 0.6 times the greater of the peak intensities corresponding to the (200) and (111) planes of the face-centered cubic lattice structure. Hereinafter, the "value obtained by dividing the peak intensity corresponding to the (220) plane of the face-centered cubic lattice structure in the vicinity of the surface of the hard coating by the greater of the peak intensities corresponding to the (200) and (111) planes of the face-centered cubic lattice structure" is also referred to as the "peak magnification." A peak magnification of 0.6 or more, i.e., the peak intensity of the (220) plane in the vicinity of the surface of the hard coating being relatively greater than the peak intensities of the other planes, is believed to improve wear resistance. The peak magnification is preferably 0.8 or more, and more preferably 1.1 or more. While there is no particular upper limit for the peak magnification, it is preferable to set the upper limit to 7. It is even more preferable to set the upper limit to 5.

[0025] In the vicinity of the surface of the hard coating according to this embodiment, it is preferable that the peak intensity of the (220) plane of the face-centered cubic lattice structure is greatest, followed by the peak intensity of the (111) plane of the face-centered cubic lattice structure.

[0026] The hard coating according to this embodiment has a high Al content, and therefore the microstructure may contain AlN with a hexagonal close-packed structure. It is preferable that the microstructure contains less AlN with a hexagonal close-packed structure near the surface of the hard coating according to this embodiment. The less AlN with a hexagonal close-packed structure the microstructure contains near the surface on the side that comes into contact with the workpiece, the more likely it is that sudden coating failure that occurs when the hard coating comes into contact with the workpiece will be suppressed.

[0027] To quantitatively determine the hexagonal close-packed AlN present in the microstructure of a hard coating, a selected area diffraction pattern is obtained for the processed cross section of the hard coating (cross section in the film thickness direction) using a transmission electron microscope, and the intensity profile obtained from the selected area diffraction pattern is used.Then, in the intensity profile of the selected area diffraction pattern obtained by the transmission electron microscope, the relationship between Ih and If is evaluated based on the value of Ih x 100 / (If + Ih).

[0028] In evaluating the relationship between Ih and If of the hard coating according to this embodiment, the background value of the intensity profile is removed. The measurement location is a cross section in the film thickness direction (a cross section in a direction perpendicular to the film thickness direction). Ih and If are defined as follows: Ih: Maximum peak intensity corresponding to hexagonal close-packed AlN structure. If: Sum of peak intensities corresponding to the (111), (200), and (220) planes of a face-centered cubic lattice structure.

[0029] By evaluating the relationship between Ih and If based on the value of Ih×100 / (If+Ih), the amount of hexagonal close-packed AlN contained in the microstructure can be quantitatively evaluated. A smaller value of Ih×100 / (If+Ih) means that there is less fragile hexagonal close-packed AlN present in the microstructure. In this embodiment, it is preferable that Ih×100 / (If+Ih)≦20 be satisfied near the surface of the hard coating. It is even more preferable that Ih×100 / (If+Ih)≦15 be satisfied.

[0030] <Intermediate film, upper layer> In order to further improve the adhesion between the substrate and the hard coating, the coated member of this embodiment may optionally have an intermediate coating between the substrate and the hard coating of this embodiment. The intermediate coating may be, for example, a layer made of a metal, nitride, carbonitride, or carbide.

[0031] Furthermore, a hard coating (upper layer) having a different component ratio or composition from the hard coating of this embodiment may be formed separately on the hard coating of this embodiment formed on the substrate. Furthermore, the hard coating of this embodiment (first hard coating) and another hard coating (second hard coating) having a different component ratio or composition from the hard coating of this embodiment (first hard coating) may be laminated together. Specifically, three or more layers of first and second hard coatings may be laminated alternately.

[0032] The hard coating according to this embodiment preferably has a thickness of 1 μm to 10 μm. When an intermediate coating, an upper layer, or a second hard coating is formed in addition to the hard coating, the thickness of each coating is preferably 1 μm to 10 μm. When the thickness t of the hard coating is less than 1 μm, the vicinity of the substrate of the hard coating refers to a range within t / 2 from the interface between the substrate and the hard coating in the thickness direction, and the vicinity of the surface refers to a range within a depth t / 2 from the surface of the hard coating.

[0033] <Method of manufacturing coated member> The coated member according to this embodiment can be produced by coating (forming) a hard coating on the surface of a substrate. The hard coating according to this embodiment is preferably formed by, for example, an arc ion plating method. For the arc ion plating method, it is preferable to use a film-forming device equipped with a cathode equipped with permanent magnets on the back surface and outer periphery of a target.

[0034] The film forming apparatus includes, for example, a cathode that applies an arc current to a target that is a material for the hard coating, a furnace (vacuum vessel) that houses the substrate, a substrate rotation mechanism that rotates the substrate in the furnace, and a bias power supply that applies a bias voltage to the substrate. The film forming apparatus also preferably includes a filter mechanism that can reduce droplets by using a magnetic field.

[0035] The temperature inside the furnace during coating of the hard coating according to this embodiment is preferably 420° C. to 550° C. The pressure inside the furnace is preferably 1 Pa to 6 Pa.

[0036] The absolute value of the negative pressure bias voltage applied to the substrate is preferably gradually increased from the vicinity of the substrate to the vicinity of the surface of the hard coating to be formed. The negative pressure bias voltage applied to the substrate near the substrate where the hard coating is to be formed is preferably -40 V to -80 V. The negative pressure bias voltage applied to the substrate near the surface of the hard coating is preferably -100 V to -150 V.

[0037] The arc current applied to the target is also preferably gradually increased from the vicinity of the substrate to the vicinity of the surface of the hard coating to be formed. The arc current applied to the target near the substrate of the hard coating is preferably 70 A to 120 A. The arc current applied to the target near the surface of the hard coating is preferably 120 A to 180 A.

[0038] As described above, this specification discloses various aspects of the technology, the main aspects of which are summarized below.

[0039] As described above, the coated member according to the present invention is a coated member having a substrate and a hard coating formed on a surface of the substrate, the hard coating contains a nitride or a carbonitride of a metal element, the aluminum (Al) content is 65 atomic % or more and 85 atomic % or less, the chromium (Cr) content is 15 atomic % or more and 35 atomic % or less, and the total content of the aluminum (Al) and chromium (Cr) is 90 atomic % or more and 100 atomic % or less, in the total amount of the metal elements and metalloid elements contained in the hard coating; the hard coating has a crystal plane exhibiting a maximum peak intensity in the vicinity of the substrate and in the vicinity of the surface in an intensity profile determined from a selected area diffraction pattern of a transmission electron microscope, In the vicinity of the substrate, a peak corresponding to the (111) plane or the (200) plane of the face-centered cubic lattice structure exhibits maximum intensity, Near the surface, the peak corresponding to the crystal plane of the face-centered cubic lattice structure exhibits the maximum intensity, and the peak intensity corresponding to the (220) plane of the face-centered cubic lattice structure is 0.6 times or more the larger of the peak intensities corresponding to the (200) plane and the (111) plane of the face-centered cubic lattice structure.

[0040] According to this configuration, a covering member having excellent durability can be obtained.

[0041] In the intensity profile of the hard coating near the ice surface obtained from the selected-area diffraction pattern of the coated member of the above configuration under a transmission electron microscope, it is preferable that the relationship Ih × 100 / (Ih + If) ≦ 20 be satisfied, where Ih is the maximum peak intensity corresponding to AlN with a hexagonal close-packed structure, and If is the sum of the peak intensities corresponding to the (111), (200), and (220) planes of the face-centered cubic lattice structure.

[0042] According to this configuration, a covering member having superior durability can be obtained. [Example]

[0043] <Sample> A coated member having a hard coating formed on the surface of a substrate was used as a sample.

[0044] <Base material> The substrate was a two-flute ball end mill made of cemented carbide. The substrate's composition was 8% by mass of Co, 0.5% by mass of Cr, and 0.3% by mass of VC, with the remainder being WC and unavoidable impurities. The average particle size of the WC was 0.6 μm, and the substrate's hardness was 93.9 HRA.

[0045] <Sample manufacturing method> <Film forming equipment> For the formation (film formation) of a hard film on the substrate surface, a film formation apparatus using an arc ion plating method was used. This film formation apparatus had a plurality of cathodes (arc evaporation sources), a vacuum chamber, and a substrate rotation mechanism. The cathode was provided with an electromagnetic coil for converging plasma on the front surface of the target and a permanent magnet on the back surface of the target. Further, the cathode had a filter mechanism capable of reducing droplets by a magnetic field. The inside of the vacuum chamber could be evacuated by a vacuum pump, and gas could be introduced into the vacuum chamber through a supply port provided in the vacuum chamber. A bias power supply could be connected to the substrate installed in the vacuum chamber, and a negative-pressure bias voltage could be applied independently to a plurality of substrates. The substrate rotation mechanism had a work table, a plate-shaped jig attached to the work table, and a pipe-shaped jig attached to the plate-shaped jig. In the substrate rotation mechanism, the work table rotated at a speed of 3 revolutions per minute, and the plate-shaped jig and the pipe-shaped jig could each rotate and revolve on their own.

[0046] <Heating and Vacuum Exhaust Process> A plurality of substrates were respectively fixed to the pipe-shaped jigs in the vacuum chamber of the film formation apparatus, and the pre-film formation process was carried out as follows. First, the inside of the vacuum chamber was evacuated to a pressure of 5×10 -3 Pa or less. Then, using a heater installed in the vacuum chamber, the substrate was heated until the substrate temperature reached 500°C, and vacuum exhaust was performed. As a result, the substrate temperature was set to 500°C, and the pressure inside the vacuum chamber was set to 5×10 -3 Pa or less.

[0047] <Ar Bombardment Process> Thereafter, Ar gas was introduced into the vacuum chamber, a current was passed through the filament to generate Ar ions, a negative-pressure bias voltage was applied to the substrate, and Ar bombardment was performed.

[0048] <Film Formation Process> After Ar bombardment, the gas in the vacuum chamber was replaced with nitrogen, and the pressure inside the vacuum chamber was adjusted to 4 Pa. Power was supplied to the cathode, and a negative bias voltage was applied to the substrate, resulting in a nitride (hard coating) coating of approximately 3 μm. Table 1 summarizes the deposition conditions. For example, "Al75Cr25" in the "Cathode" column in Table 1 means that the cathode composition was 75 atomic % Al and 25 atomic % Cr. In the bias voltage and arc current columns, if the bias voltage and arc current values ​​were varied (graded) from near the substrate to near the surface of the hard coating, the values ​​near the substrate, near the surface, and at intermediate positions are listed. If the values ​​were kept constant, the values ​​are listed.

[0049] [Table 1]

[0050] ≪Composition analysis≫ The composition of the hard coating was measured using a wavelength dispersive electron probe microanalysis (WDS-EPMA) attached to an electron probe microanalyzer (JXA-8500F manufactured by JEOL Ltd.). The cross section of the ball end mill with the hard coating formed on its surface was mirror-finished and used for composition analysis. The measurement conditions were an accelerating voltage of 10 kV, a probe current of 5 × 10 -8 A, the acquisition time was 10 seconds. The analysis area was a range of approximately 1 μm in diameter per point, and the content of each element was measured at five points. The content ratio of the detected element and the content ratio of the metal element in the hard coating were calculated from the average values ​​of the five measurements.

[0051] ≪TEM analysis≫ Microanalysis of the hard coating was carried out using a field discharge transmission electron microscope (TEM, JEM-2100F model manufactured by JEOL Ltd.). Specifically, selected area diffraction patterns were obtained and the structure was observed. The selected area diffraction patterns of the hard coating were obtained under the following conditions: accelerating voltage 200 kV, selected area diameter φ500 nm (circular), camera length 100 cm, and incident electron dose 5.0 pA / cm. 2The selected area diffraction patterns were obtained under the conditions of (on a fluorescent screen). The selected area diffraction patterns were obtained near the substrate and near the surface of the hard coating. The brightness of the obtained selected area diffraction patterns was converted to intensity, and an intensity profile was obtained using the method described above. From the intensity profile, the peak intensity of each crystal plane of the hard coating and the value of Ih x 100 / (If + Ih) near the surface were obtained.

[0052] <Residual stress> The residual stress and crystal structure of the hard coating were analyzed using an X-ray diffraction device. 2 The residual stress was measured using the ψ method. Test pieces made of cemented carbide were also used to measure the residual stress.

[0053] <Hardness / Elastic Modulus> The hardness and elastic modulus of the hard coating were measured using a nanoindentation tester (ENT-2100, manufactured by Elionix Co., Ltd.). Measurements were performed by mirror-polishing the cross section of the coating by tilting the test piece 5 degrees relative to the outermost surface of the coating, and then selecting an area on the polished surface of the coating where the maximum indentation depth was less than approximately 1 / 10 of the film thickness. Measurements were performed at 15 points under the measurement condition of an indentation load of 9.8 mN / sec, and the hardness and elastic modulus were calculated from the average of 11 points, excluding the two points with the largest value and the two points with the smallest value.

[0054] The measured values ​​are summarized in Tables 2 and 3. Blank columns or columns marked with "-" in each table indicate that no measurements were performed. For example, "Al70Cr30N" in the "Coating composition" column of Table 2 means that the hard coating is an alloy nitride of Al and Cr, and the composition of the metal components of the hard coating is Al: 70 atomic % and Cr: 30 atomic %. The value in the "Near-surface (220) plane intensity ratio" column is "the value (peak magnification) obtained by dividing the peak intensity corresponding to the (220) plane of the face-centered cubic lattice structure near the surface of the hard coating by the larger of the peak intensities corresponding to the (200) plane and the (111) plane of the face-centered cubic lattice structure."

[0055] [Table 2]

[0056] [Table 3]

[0057] For Examples 1 to 4, in which the substrate was coated while the negative bias voltage applied to it was gradient (changed) from near the substrate to near the surface, the crystal structure was evaluated by obtaining the intensity profile from the selected area diffraction patterns near the substrate and near the surface.

[0058] In the comparative example, the bias voltage applied to the substrate during coating was constant, and the crystal plane showing the maximum intensity near the substrate and near the surface was the same. Comparative example 7 is an AlCr nitride, which has been conventionally used in cutting tools.

[0059] In the measurement using an X-ray diffractometer, no clear peak corresponding to AlN with a hexagonal close-packed (hcp) structure was confirmed except for Comparative Example 4.

[0060] 1 to 4 show the results of TEM analysis of Example 1. FIG. 1 shows a selected-area diffraction pattern of the hard coating of Example 1 near the substrate. FIG. 2 shows an intensity profile obtained from the selected-area diffraction pattern of FIG. 1. FIG. 3 shows a selected-area diffraction pattern of the hard coating of Example 1 near the surface. FIG. 4 shows an intensity profile obtained from the selected-area diffraction pattern of FIG. 3. The peak of the hard coating of Example 1 had the greatest intensity for the (200) plane of the face-centered cubic lattice (fcc) structure near the substrate, and the greatest intensity for the (220) plane of the face-centered cubic lattice structure near the surface. Furthermore, a slight peak corresponding to AlN with a hexagonal close-packed (hcp) structure was confirmed near the surface.

[0061] 5 and 6 show intensity profiles near the substrate and near the surface obtained from the selected area diffraction pattern of the hard coating according to Example 2. The peak of the hard coating according to Example 2 had the greatest intensity near the substrate for the (200) plane of the face-centered cubic lattice structure, and the greatest intensity near the surface for the (220) plane of the face-centered cubic lattice structure. A slight peak corresponding to AlN with a hexagonal close-packed (hcp) structure was also observed near the surface of the hard coating according to Example 2.

[0062] 7 and 8 show intensity profiles near the substrate and near the surface obtained from the selected area diffraction pattern of the hard coating according to Example 3. The peak of the hard coating according to Example 3 had the greatest intensity near the substrate for the (200) plane of the face-centered cubic lattice structure, and near the surface for the (111) plane of the face-centered cubic lattice structure. More peaks corresponding to AlN with a hexagonal close-packed (hcp) structure were confirmed near the surface of the hard coating according to Example 3 than in Examples 1 and 2.

[0063] 9 and 10 show the intensity profiles obtained from the selected area diffraction pattern of the hard coating of Example 4. In Example 4, the (111) plane of the face-centered cubic lattice structure showed the maximum intensity near the substrate, and the (220) plane of the face-centered cubic lattice structure showed the maximum intensity near the surface. In Example 4, more peaks corresponding to AlN with a hexagonal close-packed (hcp) structure were confirmed near the substrate and near the surface than in Examples 1 and 2.

[0064] It was confirmed that the hard coatings according to Examples 1 to 4 have different crystal planes showing the maximum peak intensity near the substrate and near the surface, and that the peak corresponding to the (220) plane is higher near the surface (the surface-near (220) plane intensity ratio (peak magnification) is 0.6 or more).

[0065] In order to confirm the microstructure of the hard coatings according to Examples 1 to 4, microstructure observations were carried out near the substrate and near the surface. In cross-sectional structures observed from a direction perpendicular to the film thickness growth direction, the grain boundaries tend to become unclear due to the influence of overlapping in the thickness direction of the sample. Therefore, in order to evaluate the grain size while eliminating the influence of overlapping in the thickness direction of the sample, microstructure observations were carried out from the film thickness growth direction.

[0066] A transmission electron microscope was used for the microstructural observation. The microstructural observation was performed at low magnification, and a portion was selected after excluding clearly coarse crystal grains, and the evaluation was performed at a magnification that allowed for the observation of 100 or more crystal grains.

[0067] 11 and 12 are examples of microstructure observation photographs of the hard coating according to Example 1 near the substrate and near the surface. A binarized image was created from the observation photographs of FIGS. 11 and 12 to determine the area of ​​each granular particle, and the circle-equivalent grain size was calculated from the binarized image to evaluate the grain size. The circle-equivalent grain size is the diameter of a perfect circle with the same area as the columnar grain. Interrupted grains on the periphery of the image were excluded from the observation. Near the substrate, the average circle-equivalent grain size was 59 nm, with a standard deviation of 35 nm. Near the surface, the average circle-equivalent grain size was 90 nm, with a standard deviation of 52 nm. The hard coatings according to Examples 1 to 4 had larger grain sizes and standard deviations near the surface than near the substrate. On the other hand, the hard coatings according to Comparative Examples 1 to 7 had a nearly uniform grain size throughout the coating.

[0068] <Cutting test> (Condition) Dry processing Tool: 2-flute carbide ball end mill (ball radius 1.0 mm) Cutting method: bottom cutting Workpiece: STAVAX (52HRC) (manufactured by Böhler-Uddeholm Co., Ltd.) Depth of cut: axial, 0.14 mm, radial, 0.14 mm Cutting speed: 99.0m / min Feed per blade: 0.028 mm / blade Cutting distance: 40m Evaluation method: After cutting, the maximum wear width on the flank face near the chisel of the ball end mill was measured using a scanning electron microscope. The cutting evaluation results are summarized in Table 4.

[0069] [Table 4]

[0070] The hard coatings according to Examples 1 to 4 had a smaller maximum flank wear width than Comparative Example 7 and were superior in durability.

[0071] The hard coatings of Comparative Examples 1 to 4 and 6 tended to have poor durability, with early peeling occurring, possibly due to poor adhesion. The hard coatings of Comparative Examples 5 and 7 had a larger maximum flank wear width and were inferior in durability compared to Examples 1 to 4.

Claims

1. A coated member having a substrate and a hard coating formed on a surface of the substrate, the hard coating contains a nitride or a carbonitride of a metal element, the hard coating contains, in a total amount of the metal elements and metalloid elements, an aluminum (Al) content of 65 atomic % or more and 85 atomic % or less, a chromium (Cr) content of 15 atomic % or more and 35 atomic % or less, and a total aluminum (Al) and chromium (Cr) content of 90 atomic % or more and 100 atomic % or less; the hard coating has a crystal plane exhibiting a maximum peak intensity in the vicinity of the substrate and in the vicinity of the surface in an intensity profile determined from a selected area diffraction pattern of a transmission electron microscope, In the vicinity of the substrate, a peak corresponding to the (111) plane or the (200) plane of the face-centered cubic lattice structure exhibits maximum intensity, a peak corresponding to a crystal plane of a face-centered cubic lattice structure exhibits maximum intensity near the surface, and the peak intensity corresponding to the (220) plane of the face-centered cubic lattice structure is 0.6 times or more the larger of the peak intensities corresponding to the (200) plane and the (111) plane of the face-centered cubic lattice structure.

2. 2. The coated member according to claim 1, wherein in an intensity profile near the surface of the hard coating obtained from a selected-area diffraction pattern under a transmission electron microscope, a relationship of Ih × 100 / (Ih + If)≦20 is satisfied, where Ih is the maximum peak intensity corresponding to AlN having a hexagonal close-packed structure, and If is the sum of peak intensities corresponding to the (111), (200), and (220) planes of the face-centered cubic lattice structure.

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