Hard Coating, Hard Coating-Coated Tool, and Method for Producing Hard Coating

Abstract

This hard coating 32 comprises: a first layer 34 provided on the surface of a base material 30; and a second layer 36 provided on the surface of the first layer 34. The first layer 34 is composed of AlCrαN, and the second layer 36 is composed of AlCrCN. In addition, the overall film thickness T, which is the total of the film thickness T1 of the first layer 34 and the film thickness T2 of the second layer 36, falls within a range of 0.5-9.0 μm. The proportion (T2 / T) of the film thickness T2 of the second layer 36 with respect to the overall film thickness T falls within a range of 5-50%. Furthermore, the hard coating exhibits X-ray diffraction peaks including peaks that are attributed to the (111) plane and (200) plane. The peak intensity ratio (SP1 / SP2) of the peak intensity SP1 of the (111) plane to the peak intensity SP2 of the (200) plane falls within a range of 0.1-20. With the hard coating 32 thus configured, it is possible to achieve excellent durability.

Description

Technical Field

[0001] The present invention relates to a hard film for coating the surface of a substrate, a hard film-coated tool coated with the hard film, and a method for manufacturing the hard film.

Background Art

[0002] In various members such as cutting tools such as taps, drills, end mills, milling cutters, and inserts, non-cutting tools such as raising taps, forging tools, and press dies, or friction parts that require wear resistance, it has been proposed to improve wear resistance, seizure resistance, durability, etc. by coating a hard film on the surface of the substrate. The hard films described in Patent Documents 1 and 2 are examples thereof, and techniques for forming a hard film using AlCrN or AlCrCN have been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, even in such conventional hard films, chipping, peeling, etc. may occur on the film depending on processing conditions, use conditions, etc., and sufficient satisfactory durability may not always be obtained, and there is still room for improvement. For example, when tapping SCM440 (chromium molybdenum steel) specified by JIS using a raising tap coated with AlCrN, the number of processed holes was less than 1000, and sufficient durability could not be obtained.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to further improve the durability of an AlCrN-based hard film.

Means for Solving the Problems

[0006] In order to achieve such an object, a first invention is a hard film provided on the surface of a substrate so as to coat the surface thereof, wherein (a) the hard film is composed of a first layer provided on the surface of the substrate and a second layer provided on the surface of the first layer; (b) the first layer is Al a Cr b α c N (where a, b, c are atomic ratios, a + b + c = 1, 0 ≦ c ≦ 0.40, b / a is in the range of 0.25 to 1.0, and the optional additive component α is one or more elements selected from Group IVa, Group Va, Group VIa (excluding Cr), and Y of the periodic table of elements); (c) the second layer is Al d Cr e C f N (where d, e, f are atomic ratios, d + e + f = 1, 0.001 ≦ f ≦ 0.20, and e / d is in the range of 0.25 to 1.0); (d) the total film thickness T obtained by combining the film thickness T1 of the first layer and the film thickness T2 of the second layer is in the range of 0.5 μm to 9.0 μm, and the ratio (T2 / T) of the film thickness T2 of the second layer to the total film thickness T is in the range of 5% to 50%; (e) in the X-ray diffraction peaks of the hard film composed of the first layer and the second layer, peaks attributed to the (111) plane and the (200) plane are present, and the intensity ratio (SP1 / SP2) of the peak intensity SP1 of the (111) plane to the peak intensity SP2 of the (200) plane is in the range of 0.1 to 20. Note that the values obtained by multiplying the atomic ratios a to f by 100 are at% (atomic %).

[0007] A second invention is a hard film-coated tool having a hard film provided on the surface of a substrate, wherein the hard film is the hard film of the first invention.

[0008] The third invention is a method for manufacturing the hard coating of the first invention, wherein (a) both the first layer and the second layer are formed by a high-power pulsed magnetron sputtering method, and (b) the second layer uses an AlCr alloy as a target, supplies nitrogen gas and hydrocarbon gas into the chamber for sputtering, and adjusts the supply amount of the hydrocarbon gas so that the atomic ratio f of C is 0.001 or more and 0.20 or less. The above high-power pulsed magnetron sputtering method is a film-forming technique called HiPIMS (abbreviation for High-Power Impulse Magnetron Sputtering), and hereinafter it will be referred to as the HiPIMS method.

Effects of the Invention

[0009] According to the hard coating of the first invention and the hard coating-coated tool of the second invention, excellent durability can be obtained. Further, when an AlCrN-based hard coating is formed by an arc ion plating method, minute droplets called macro particles adhere to the inside and surface of the coating, which may cause adhesion of the workpiece, chipping, peeling, etc. of the coating, resulting in a decrease in the durability of the hard coating. However, according to the HiPIMS method of the third invention, macro particles are reduced, the anti-adhesion property and the anti-chipping property are improved, and the durability is further improved.

Brief Description of the Drawings

[0010]

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Mode for Carrying Out the Invention

[0011] The present invention is suitably applied to a hard coating provided on the surface of a base material in various processing tools such as cutting tools such as taps, drills, end mills, mills, and inserts, non-cutting tools such as raising taps (also called roll taps), roll tools, and press dies, that is, hard coating-coated tools. Even outside of processing tools, it can be applied to hard coatings of various members that require wear resistance, seizure resistance, etc., such as bearing members. It can also be applied to the tips of tip-exchangeable tools where the tips are detachably attached to the bodies.

[0012] As a method for manufacturing a hard coating of the present invention, that is, a coating method, physical vapor deposition methods (PVD methods) such as electron beam evaporation method, hollow cathode method, magnetron sputtering method (MS method), arc ion plating method (AIP method), etc. can be used. The MS method uses glow discharge by applying a voltage to a cathode (cathode) where a magnet and a target are arranged in a rare gas atmosphere, causing accelerated ions to collide with the target, knocking out coating material from the target by its kinetic energy, and depositing the knocked-out material on a substrate to form a film. In this case, it is possible to form a smooth film as compared with the electron beam evaporation method, hollow cathode method, and AIP method in which droplets are generated due to thermal shock. The MS method includes a DCMS method in which a DC voltage (DC) is applied to the cathode, and a HiPIMS method in which a capacitor and a switch are arranged between a DC voltage power supply and the cathode, and a high-power pulse is applied to the cathode by charging and discharging the capacitor. Since the HiPIMS method supplies a large amount of power to the cathode, it can generate a plasma with a higher ionization rate than the DCMS method. As a method for manufacturing the hard coating of the present invention, the HiPIMS method, which is a kind of sputtering method, is preferably used. After forming AlCrN as the first layer in a mixed gas atmosphere of Ar and N2 using an AlCr alloy as a target, hydrocarbon gas may be further introduced during the formation of the second layer to form AlCrCN. When AlCrαN containing an optional additive component α is provided as the first layer, an AlCrα alloy may be used as the target during the formation of the first layer.

[0013] The AIP method is a technique for evaporating or ionizing a target from a solid using arc discharge and forming a film on a substrate. Since a very high energy is supplied to the target, a film having high adhesion and wear resistance can be obtained. On the other hand, due to the impact of arc discharge, a large amount of macro particles called droplets with a size of several micrometers or more adhere to the substrate or the film surface. There is also a method of filtering to reduce the incidence of droplets, and in this case, it is preferably used as a method for manufacturing the hard coating of the present invention. Coating techniques other than this AIP method and the above-mentioned HiPIMS method can also be adopted.

Examples

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or deformed for the purpose of explanation, and the shapes, dimensional ratios, angles, etc. of each part are not necessarily drawn accurately.

[0015] FIG. 1 is a front view of the raised tap 10 to which the present invention is applied, as viewed from a direction perpendicular to the axis O, and FIG. 2 is an enlarged view of a cross section of the threaded portion 16 taken along the arrow II-II in FIG. 1. This raised tap 10 continuously and concentrically integrally includes a shank 12 attached to the main shaft of a tapping device (not shown) and a threaded portion 16 for raising (upsetting) the female thread (forging process) in the axial direction (a direction parallel to the axis O). The threaded portion 16 has a polygonal shape formed by sides curved outward, and in this embodiment, a substantially regular hexagonal cross section, and on its outer peripheral surface, there are provided male threads for raising the female thread by biting into and plastically deforming the inner wall surface layer portion of the pilot hole of the workpiece (female thread material).

[0016] The thread crest 18 of the male thread provided on the threaded portion 16 has a cross-sectional shape corresponding to the shape of the valley of the female thread to be formed, and is provided along the helical winding line of the lead angle corresponding to the female thread. Six protruding portions 20 where the thread crest 18 protrudes radially outward and a relief portion 22 having a smaller diameter following the protruding portion 20 are provided alternately along the advancing direction of the thread and at equal angular intervals of 60° around the axis O. That is, each vertex portion of the regular hexagon is a protruding portion 20, a large number of protruding portions 20 are continuously provided parallel to the axis O, and six rows of such a series of continuously arranged protruding portions 20 in the axial direction are provided at equal angular intervals around the axis O. Note that FIG. 2 is a cross-sectional view cut along the helical winding line at the valley portion of the thread crest 18.

[0017] The thread portion 16 also includes a complete thread portion 26 having a substantially constant diameter dimension in the axial direction and a biting portion 24 having a smaller diameter toward the tip side. In the biting portion 24, the outer diameter, effective diameter, and root diameter of the male thread change to a smaller diameter with a constant change gradient equal to each other. Also in the biting portion 24, it forms a substantially regular hexagonal shape as in FIG. 2 and alternately includes the protruding portions 20 and the relief portions 22 in the circumferential direction. Further, oil grooves 28 for supplying a lubricating oil agent are provided in parallel with the axis O at intermediate positions of the six rows of protruding portions 20 around the axis O on the outer peripheral surface of the thread portion 16. There may be one oil groove 28, and it may be omitted.

[0018] Such a raising tap 10 is screwed into the counterbore provided in the workpiece from the biting portion 24 side, and the protruding portions 20 bite into the inner wall surface layer portion of the counterbore and plastically deform it to form an internal thread. In such tapping processing using the raising tap 10, a large rotational torque is required, and wear and seizure are likely to occur in the thread portion 16 due to friction with the workpiece, and sufficient tool life may not be obtained depending on the processing conditions.

[0019] On the other hand, as shown in FIG. 3, the thread portion 16 of the raising tap 10 of this embodiment is coated with a hard coating 32 so as to cover the surface of the base material 30. The base material 30 is made of cemented carbide, high-speed tool steel, or other tool materials, and is high-speed tool steel in this embodiment. The hard coating 32 is composed of a first layer 34 provided on the surface of the base material 30 and a second layer 36 provided on the surface of the first layer 34, and the surface of the coating is constituted by the second layer 36. The raising tap 10 corresponds to a hard-coated tool.

[0020] Specifically explaining the hard coating 32, the first layer 34 is Al a Cr b α cN (where a, b, and c are atomic ratios, a + b + c = 1, 0 ≦ c ≦ 0.40, b / a is in the range of 0.25 to 1.0, and the optional additive component α is one or more elements selected from Group IVa, Group Va, Group VIa (excluding Cr), and Y of the periodic table of elements). The second layer 36 is Al d Cr e C f N (where d, e, and f are atomic ratios, d + e + f = 1, 0.001 ≦ f ≦ 0.20, and e / d is in the range of 0.25 to 1.0). Also, the total film thickness T, which is the sum of the film thickness T1 of the first layer 34 and the film thickness T2 of the second layer 36, is in the range of 0.5 μm to 9.0 μm, and the ratio (T2 / T) of the film thickness T2 of the second layer to the total film thickness T is in the range of 5% to 50%. Further, this hard coating 32 has peaks attributable to the (111) plane and the (200) plane in X-ray diffraction (hereinafter also expressed as XRD (X Ray Diffraction)), and the intensity ratio (SP1 / SP2) of the peak intensity SP1 of the (111) plane to the peak intensity SP2 of the (200) plane is in the range of 0.1 to 20.

[0021] Figure 6 is an example of the intensity distribution measured under the following measurement conditions using an X-ray diffractometer manufactured by PANalytical, and is the measurement result of test piece No7 shown in Figures 7 and 8. θ is the diffraction angle. The peak of the (111) plane is a peak that appears in the angle range of 2θ = 37° to 39°, and the peak of the (200) plane is a peak that appears in the angle range of 2θ = 43.5° to 44.5°. The peak intensities SP1 and SP2 are values measured based on the intensity of the base portion between the peaks as shown in Figure 6. The intensity ratio (SP1 / SP2) in the case of Figure 6 (test piece No7) is 6.4 (see Figure 8). In the column of XRD, that is, X-ray diffraction, in Figure 8, the "presence or absence of peak" is the presence or absence of the peak of the (111) plane, and the "peak intensity ratio" is the above intensity ratio (SP1 / SP2). That is, the peak of the (200) plane always exists regardless of the film structure of the first layer 34 and the second layer 36. The peak marked with "*" in Figure 6 is a peak derived from the cemented carbide test piece substrate. The results of X-ray diffraction (XRD) in Figure 8 are the results of forming the same hard coating 32 on the cemented carbide test piece substrate and examining it for test pieces No1 to No40. 〔Measurement Conditions〕 · Tube voltage: 45 kV · Tube current: 40 mA · X-ray source: CuKa (0.15060 nm) · Divergence slit: 1 / 8° · Anti-scatter slit: 1°, 25° - 55°

[0022] Figures 7 and 8 are diagrams for explaining a plurality of test pieces No1 to No40 having different coating structures of the hard coating 32. Test pieces No1 to No29 are the products of the present invention having the requirements of the hard coating 32, and test pieces No30 to No40 are comparative products that do not satisfy any of the requirements of the hard coating 32. In the comparative products No30 to No40, the items marked with dots mean that they deviate from the requirements of the hard coating 32. The reason why the film thickness T2 of the second layer 36 of the test piece No36 is 0.0 is that the carbon content of the second layer 36 is 0.0 at%, and since it is substantially composed of AlCrN, the film thickness T1 of the first layer 34 including the second layer 36 is used. Note that even for the comparative products that do not satisfy the requirements of the hard coating 32, they are described as the hard coating 32.

[0023] Next, the manufacturing method of the above hard coating 32, that is, the coating method, will be described. In this example, the hard coating 32 is coated on the substrate 30 by the HiPIMS method. Figure 4 is a conceptual diagram for explaining an example of a sputtering apparatus capable of implementing the HiPIMS method. This sputtering apparatus 40 is configured to include a chamber 42, a bias power supply 44, a target 46, and a power supply device 48. The target 46 is made of an AlCr alloy that constitutes the hard coating 32. When the first layer 34 does not have the optional additive component α, one type of target 46 made of an AlCr alloy may be used. When the first layer 34 has the optional additive component α, two types of targets 46, namely, the AlCrα alloy for forming the first layer 34 and the AlCr alloy for forming the second layer 36, may be used. This target 46 is arranged at the cathode together with a magnet, and when a - voltage is applied by the power supply device 48, ions (Ar) accelerated by glow discharge +) is made to collide with the target 46, and the kinetic energy thereof knocks out AlCrα or AlCr, which is the coating material, from the target 46 and adheres to the substrate 30 to which a negative bias voltage is applied by the bias power supply 44. The power supply device 48 includes a capacitor and a switch circuit in addition to a DC voltage power supply. By charging and discharging the capacitor, for example, the peak power density is 0.1 kW / cm 2 or more high-power pulses are applied to the cathode. Specifically, for example, the film is formed under the film-forming conditions where the cathode input power is 5 to 55 kW, the degree of vacuum is 0.5 to 2.0 Pa, the on time of the pulse waveform is 20 μs to 4000 μs, and the off time of the pulse waveform is 150 μs to 12000 μs. Thereby, a plasma with a high ionization rate is generated, and a hard film 32 having high smoothness with few macro particles, excellent adhesion resistance, abrasion resistance, and heat resistance is coated.

[0024] Also, when forming the first layer 34, the first layer 34 of AlCrαN can be formed by introducing nitrogen gas (N2) into the chamber 42 as a reaction gas. When forming the second layer 36, the second layer 36 of AlCrCN can be formed by introducing nitrogen gas (N2) and methane gas (CH4) into the chamber 42 as reaction gases. Other hydrocarbon gases may be used instead of methane gas. By adjusting the supply amount of methane gas, the atomic ratio f of C can be set to 0.001 or more and 0.20 or less. Fig. 5 is a diagram showing the relationship between the supply ratio of CH4 to the total flow rate of N2 + CH4 [CH4 / (N2 + CH4)] and the carbon content. As the supply ratio of methane gas increases, the carbon content in the second layer 36 increases. Thereby, for example, as shown in Test Specimen No. 3 in Fig. 8, the carbon content in the second layer 36 can be increased to 20 at%.

[0025] The carbon content can be examined, for example, by the SIMS method (secondary ion mass spectrometry). The carbon content (at%) of the second layer 36 shown in FIG. 8 is the measurement result by the SIMS method. The measuring device is PHIADEPT1010 (manufactured by ULVAC-PHI, Inc.), the primary ion species is Cs+, the primary acceleration voltage is 5.0 kV, the detection area is 24 μm × 24 μm, and the standard sample for quantification is AlN. FIG. 5 shows the measurement results of the carbon content for four types of test pieces No12, No22, No7, and No36 with different supply amounts of methane gas when forming the second layer 36. For test piece No12, the supply ratio of CH4 [CH4 / (N2 + CH4)] was 21%, and the carbon content was approximately 9.0 at%. For test piece No22, the supply ratio of CH4 [CH4 / (N2 + CH4)] was 10%, and the carbon content was approximately 4.0 at%. For test piece No7, the supply ratio of CH4 [CH4 / (N2 + CH4)] was 3%, and the carbon content was approximately 0.9 at%. For test piece No36, the supply ratio of CH4 [CH4 / (N2 + CH4)] was 0%, that is, when CH4 was not introduced, AlCrN was formed as the second layer 36, and the carbon content was approximately 0.01 at%.

[0026] FIG. 9 is a diagram showing the results of tapping the test pieces No1 to No40 shown in FIGS. 7 and 8 under the following processing conditions, examining the number of processed holes until the tool life is reached as durability, and examining the cause of the life. The "workpiece" SCM440 in the processing conditions represents chromium molybdenum steel by the steel material symbol according to JIS standards, and HRC is the Rockwell C hardness. Also, D of the "thread forming length" is the tool diameter, which is 6 mm in this case, and 2D = 12 mm. Note that the hard coatings 32 of the test pieces No1 to No40 are all coated using the HiPIMS method, including comparative products that do not meet the requirements of the hard coating 32. 〔Processing Conditions〕 · Tool shape: M6×1 · Workpiece: SCM440 (30HRC) · Machining speed: 15 m / min · Thread forming length: 2D · Cutting oil: Water-soluble cutting oil, diluted 20 times, external oil supply

[0027] In the "Judgment" column of Fig. 9, "○" means qualified and "×" means unqualified. Here, it is considered qualified when the number of processed holes is 1000 or more. Also, in the "Cause of Life" column, "GP-OUT" means that the through-thread plug gauge (GP) cannot pass through the formed internal thread, which means that the effective diameter of the internal thread has become smaller due to the wear of the hard coating 32. As is clear from the results in Fig. 9, all of the test products No1 to No29, which are the products of the present invention, were able to perform tapping processing of 1000 holes or more and were qualified. The cause of life was GP-OUT due to the wear of the hard coating 32 in all cases. On the other hand, the test products No30 to No40, which are comparative products that do not meet the requirements of the hard coating 32, all had less than 1000 processed holes due to adhesion, chipping of the coating, coating peeling, etc., and were inferior in durability compared to the products of the present invention.

[0028] Thus, according to the raised tap 10 of the present embodiment coated with the hard coating 32, excellent durability can be obtained. Further, when an AlCrN-based hard coating is formed by the AIP method, minute droplets called macro particles (for example, having a diameter of 1 μm or more) adhere to the inside or the surface of the coating, which may cause adhesion of the workpiece, chipping of the coating, peeling, etc., and the durability may decrease. However, in the present embodiment, since the hard coating 32 is coated using the HiPIMS method, the macro particles are reduced, the anti-adhesion property and the anti-chipping property are improved, and the durability is further improved.

[0029] Incidentally, when the inventors examined the number of macro particles having a diameter of 1 μm or more present on the surface of the hard coating 32 using a scanning electron microscope, it was 1 / 10 or less compared to the case where an AlCrN film was coated by the AIP method.

[0030] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, these are merely one embodiment, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

Explanation of Reference Numerals

[0031] 10: Pouring tap (hard film-coated tool) 30: Substrate 32: Hard film 34: First layer 36: Second layer 40: Sputtering apparatus 42: Chamber 46: Target

Claims

1. A hard film provided on the surface of a substrate so as to cover the surface, wherein the hard film comprises a first layer provided on the surface of the substrate and a second layer provided on the surface of the first layer, The first layer is Al a Cr b α c N [where a, b, and c are atomic ratios, a + b + c = 1, 0 ≦ c ≦ 0.40, b / a is in the range of 0.25 to 1.0, and the optional additive component α is one or more elements selected from Group IVa, Group Va, Group VIa (excluding Cr), and Y of the periodic table of elements]. The second layer is Al d Cr e C f N [where d, e, f are atomic ratios, d + e + f = 1, 0.001 ≦ f ≦ 0.20, and e / d is in the range of 0.25 to 1.0], the total film thickness T obtained by combining the film thickness T1 of the first layer and the film thickness T2 of the second layer is in the range of 0.5 μm to 9.0 μm, and the ratio (T2 / T) of the film thickness T2 of the second layer to the total film thickness T is in the range of 5% to 50%, the X-ray diffraction peaks of the hard film composed of the first layer and the second layer have peaks attributable to the (111) plane and the (200) plane, and the intensity ratio (SP1 / SP2) of the peak intensity SP1 of the (111) plane to the peak intensity SP2 of the (200) plane is in the range of 0.1 to 20 A hard film characterized by the above.

2. A hard film-coated tool having a hard film provided on the surface of a substrate, wherein the hard film is the hard film according to Claim 1 A hard film-coated tool characterized by the above.

3. A method for manufacturing the hard film according to Claim 1, wherein both the first layer and the second layer are formed by a high-power pulsed magnetron sputtering method, the second layer uses an AlCr alloy as a target, nitrogen gas and hydrocarbon gas are supplied into the chamber for sputtering, and the supply amount of the hydrocarbon gas is adjusted so that the atomic ratio f of C is 0.001 or more and 0.20 or less A method for manufacturing a hard film characterized by the above.

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