Coated cutting tool with alternating layer composition

Abstract

The invention relates to a coated cutting tool comprising a substrate and a coating, the coating comprising a (Ti, Al, Si)N layer, the (Ti, Al, Si)N layer comprising a periodic variation of the contents of the elements Ti, Al and Si between a minimum content and a maximum content of each element over the thickness of the (Ti, Al, Si)N layer, wherein the average minimum content of Ti is 14 to 18 at.%, the average maximum content of Ti is 18 to 22 at.%, the average minimum content of Al is 18 to 22 at.%, the average maximum content of Al is 24 to 28 at.%, the average minimum content of Si is 0 to 2 at.%, the average maximum content of Si is 1 to 5 at.%, the remainder in the (Ti, Al, Si)N layer being an inert gas with an average content of 0.1 to 5 at.% and the element N.

Description

Technical Field

[0001] The present invention relates to a coated cutting tool for metal machining, wherein the cutting tool has a coating comprising a (Ti,Al,Si)N layer. Background Technology

[0002] There has always been a desire to improve cutting tools used in metal machining to make them more durable, able to withstand higher cutting speeds and / or other increasingly demanding cutting operations. Typically, cutting tools for metal machining comprise a hard substrate material, such as cemented carbide, with a thin, hard coating, usually deposited through either chemical vapor deposition (CVD) or physical vapor deposition (PVD). Examples of cutting tools include inserts, drills, or end mills. Ideally, the coating should possess high hardness while also having sufficient toughness to withstand harsh cutting conditions for as long as possible.

[0003] PVD(Ti,Al)N coatings are commonly used as wear-resistant coatings in cutting tools.

[0004] Different PVD methods exist, which impart different properties to the deposited coatings.

[0005] Cathodic arc evaporation utilizes an electric arc to vaporize material from a cathode target. The vaporized material or its compounds then condense onto a substrate. Cathodic arc evaporation has the advantage of high deposition rates, but it also has disadvantages such as the presence of target droplets in the coating and on the surface. This can result in a weaker coating and a relatively rough surface. In many metal cutting applications, a smooth surface of the deposited wear-resistant coating is beneficial.

[0006] Reactive sputtering is the second method in PVD. In this method, a plasma of ionized inert gas is generated and bombarded with a target. In the presence of a reactive gas, such as nitrogen, atoms from the target are ejected and accelerated toward the substrate. Since there is no droplet formation problem, coatings with smooth surfaces are typically obtained. However, achieving high metal ionization is quite difficult. Furthermore, sputtering is a rather slow deposition process.

[0007] High-power pulsed magnetron sputtering (HIPIMS) is a special type of sputtering that allows for extremely flexible changes in process parameters, especially in the power levels (average power, peak pulse power) used in conjunction with pulse on-time and the application of high bias voltage. HIPIMS enables high metal ionization and allows for the delivery of high-quality coatings, and by controlling the level of metal ionization, very specific coatings can be produced.

[0008] Under harsh cutting conditions, the heat resistance of the coating is particularly important. In this context, heat resistance refers to the coating's low thermal conductivity, which protects the cutting tool body from overheating that could damage the substrate. The more thermal protection the coating provides, the better the wear resistance of the coated cutting tool. Better wear resistance translates to longer tool life.

[0009] It is known that incorporating silicon into the coating can improve its high-temperature stability. (Ti,Al,Si)N coatings are known examples of wear-resistant coatings.

[0010] However, a drawback of (Ti,Al,Si)N is that the Al content is already moderate, and the Si content is only a few atomic percent, potentially leading to partially hexagonal and amorphous structures. See, for example, Flink et al., "Arc-Evaporated (Ti,Al,Si)N". 0.33 Al 0.67 ) 1-x Si x Structure and thermal stability of arcevaporated (Ti) thin films 0.33 Al 0.67 ) 1-x Si x "Thin Films", 517 (2008), 714-721, discloses the appearance of a hexagonal phase with more than 2 atomic % Si. Tanaka et al., "Structure and properties of Al-Ti-Si-N coatings prepared by cathodic arc ion plating method for high speed cutting applications", Surface and Coatings Technology, 146 (2001), 215-221, disclose the appearance of a hexagonal phase with more than 5 atomic % Si. This hexagonal phase leads to poor mechanical properties, such as insufficient hardness and insufficient Young's modulus.

[0011] Therefore, it is desirable to provide a (Ti,Al,Si)N coating that has a crystalline structure similar to that of a cubic solid solution and good mechanical properties.

[0012] Purpose of the invention

[0013] One object of the present invention is to provide a cutting tool with high heat resistance and excellent tool life, the cutting tool having a coating comprising a (Ti,Al,Si)N layer. Summary of the Invention

[0014] A coated cutting tool that satisfies the above-mentioned objectives has now been provided. The coated cutting tool comprises a substrate and a coating comprising a (Ti,Al,Si)N layer, wherein the (Ti,Al,Si)N layer includes periodic variations in the content of elements Ti, Al, and Si between minimum and maximum contents of each element along the thickness of the (Ti,Al,Si)N layer, wherein the average minimum content of Ti is 14 to 18 atomic%, preferably 15 to 17 atomic%, the average maximum content of Ti is 18 to 22 atomic%, preferably 19 to 21 atomic%, the average minimum content of Al is 18 to 22 atomic%, preferably 19 to 21 atomic%, the average maximum content of Al is 24 to 28 atomic%, preferably 25 to 27 atomic%, the average minimum content of Si is 0 to 2 atomic%, preferably 0 to 1 atomic%, the average maximum content of Si is 1 to 5 atomic%, preferably 2 to 4 atomic%, and the remainder in the (Ti,Al,Si)N layer is an inert gas with an average content of 0.1 to 5 atomic% and element N.

[0015] The average distance between two consecutive maximum values ​​and two consecutive minimum values ​​of any of the elements Ti, Al, and Si is 3 to 15 nm.

[0016] In the periodic variation of the contents of the elements Ti, Al and Si on the thickness of the (Ti,Al,Si)N layer, the maximum content of Ti, the minimum content of Al and the minimum content of Si on the thickness of the (Ti,Al,Si)N layer are on average consistent, and the minimum content of Ti, the maximum content of Al and the maximum content of Si on the thickness of the (Ti,Al,Si)N layer are on average consistent.

[0017] There is an average gradual variation in the content of Ti per unit distance of 0.8 to 1.5 atomic % / nm between the minimum and maximum contents and between the maximum and minimum contents on the thickness of the (Ti,Al,Si)N layer; an average gradual variation in the content of Al per unit distance of 0.8 to 1.5 atomic % / nm between the minimum and maximum contents and between the maximum and minimum contents on the thickness of the (Ti,Al,Si)N layer; and an average gradual variation in the content of Si per unit distance of 0.3 to 0.8 atomic % / nm between the minimum and maximum contents and between the maximum and minimum contents on the thickness of the (Ti,Al,Si)N layer.

[0018] Therefore, the (Ti,Al,Si)N layer can be viewed as a nanolayer with two distinct sublayers having different contents of Ti, Al, and Si. Due to the periodic gradual change in elemental content, the (Ti,Al,Si)N layer originates from PVD deposition using combinations of Ti, Al, and Si targets with different compositions, combinations of Ti, Al and Ti, Al, and Ti, Al, and Ti, Si targets, or combinations of Ti, Al and Ti, Si targets. Preferably, combinations of Ti, Al and Ti, Al, and Ti, Al, and Si targets are used.

[0019] Coated cutting tools containing (Ti,Al,Si)N layers as disclosed herein exhibit high heat resistance and excellent tool life. The (Ti,Al,Si)N layers also exhibit significant crystallinity, high hardness, high reduced Young's modulus, and high thermal conductivity as a cubic structure.

[0020] Suitablely, the average gradual variation of the Ti content per unit distance between the minimum and maximum contents and between the maximum and minimum contents over the thickness of the (Ti,Al,Si)N layer is 0.9 to 1.3 atomic% / nm, the average gradual variation of the Al content per unit distance between the minimum and maximum contents and between the maximum and minimum contents over the thickness of the (Ti,Al,Si)N layer is 0.9 to 1.3 atomic% / nm, and the average gradual variation of the Si content per unit distance between the minimum and maximum contents and between the maximum and minimum contents over the thickness of the (Ti,Al,Si)N layer is 0.5 to 0.7 atomic% / nm.

[0021] The average maximum / minimum content of elements in the (Ti,Al,Si)N layer can be calculated by taking at least 8 consecutive maximum / minimum values ​​from elemental analysis, such as STEM-EDS, and calculating the average value.

[0022] The average gradual change in elemental content per unit distance over the thickness of the (Ti,Al,Si)N layer can be calculated by subtracting the average minimum content (atomic%) from the average maximum content (atomic%) of the element, and dividing the resulting value by the average distance between the positions of the maximum and minimum content of the element in the (Ti,Al,Si)N layer. At least eight successive maximum / minimum values ​​are considered from elemental analysis.

[0023] The term "gradual" change in content as used herein refers to an average local change in elemental content per unit distance at the midpoint between the maximum and next minimum value, where the average gradual change in elemental content per unit distance over the thickness of the (Ti,Al,Si)N layer, as defined above for elements Ti, Al, and Si, falls within the same range. This average local change in content is calculated by considering the local changes in elemental content between at least eight consecutive maximum / minimum values ​​from elemental analysis.

[0024] The inert gas is suitably one or more of Ar, Kr, or Ne, preferably Ar.

[0025] Appropriately, the average distance between two successive maximum values ​​and two successive minimum values ​​of any of the elements Ti, Al, and Si is 5 to 10 nm.

[0026] In one embodiment, there is a variation in the content of element N across the thickness of the (Ti,Al,Si)N layer, between the minimum and maximum contents of each element, with an average minimum N content of 50 to 56 atomic%, preferably 51 to 55 atomic%, and an average maximum N content of 57 to 63 atomic%, preferably 58 to 62 atomic%. This variation in nitrogen content may occur due to differences in the metallic elemental composition between targets. Furthermore, different deposition parameters used for different targets may also affect the amount of nitrogen contained in the deposited structure. The average distance between two successive maximum values ​​and two successive minimum values ​​of N content is substantially the same as the average distance between two successive maximum values ​​and two successive minimum values ​​of the contents of elements Ti, Al, and Si.

[0027] In one embodiment, the innermost layer of the coating is located immediately adjacent to the substrate. This innermost layer is a nitride of one or more elements belonging to Groups 4, 5, or 6 of the periodic table, or a nitride of Al and one or more elements belonging to Groups 4, 5, or 6 of the periodic table. This innermost layer acts as a bonding layer to the substrate, increasing the adhesion of the entire coating to the substrate. Such bonding layers are commonly used in the art, and those skilled in the art should select suitable bonding layers. Preferred alternatives for this innermost layer are TiN or (Ti,Al)N. The thickness of the innermost layer is suitably less than 2 μm. In one embodiment, the thickness of the innermost layer is from 5 nm to 2 μm, preferably from 10 nm to 1 μm. Since it may also be necessary for the innermost layer to function as a barrier against Co diffusion into the coating, a thickness of at least 50 nm is required. Si-containing nitride layers are known to attract Co more readily than most other metal nitride layers. Therefore, in another embodiment, the innermost layer is from 50 nm to 2 μm, preferably from 100 nm to 1 μm.

[0028] The (Ti,Al,Si)N layer suitably comprises a cubic crystal structure.

[0029] The crystal structure present in the (Ti,Al,Si)N layer is appropriately determined by X-ray diffraction analysis or TEM analysis.

[0030] In X-ray diffraction analysis, the FWHM (full width at half maximum) of a diffraction peak depends on both the crystallinity of the (Ti,Al,Si)N layer and the grain size of the microcrystals. A smaller value indicates higher crystallinity and / or smaller grain size.

[0031] In one embodiment, the (Ti,Al,Si)N layer comprises a cubic crystal structure, wherein the FWHM (full width at half maximum) of the cubic (200) peak is 0.5 to 2.5°2θ, preferably 0.75 to 2°2θ, and most preferably 1 to 1.5°2θ in the θ-2θ scan of X-ray diffraction using Cuk-α radiation.

[0032] The crystallinity of the (Ti,Al,Si)N layer itself can be expressed as a peak-to-background ratio measured by X-ray diffraction analysis. At low crystallinity, the diffraction intensity of each (hkl) peak from a specific crystal structure is low in the θ-2θ scan, and therefore its relationship with the background intensity is also low. This can be expressed as: the intensity I of the highest peak in the θ-2θ scan of a specific crystal structure. 最大 Subtract the background intensity I at the 2θ position of the peak. 背景 Divide by the background intensity I at the 2θ position of the peak 背景 ,Right now,

[0033] Peak-to-back ratio = (I 最大 -I 背景 ) / I 背景 .

[0034] The highest peak of the crystal structure is used as I in this formula. 最大 This is because crystal structures may have different preferred crystal orientations and the relationship between the intensities of different (hkl) peaks in a crystal structure may vary.

[0035] In one embodiment of the (Ti,Al,Si)N layer of the present invention, the cubic (200) peak is one of the cubic peaks that exhibit the highest intensity in X-ray diffraction θ-2θ scan.

[0036] In one embodiment, the (Ti,Al,Si)N layer comprises a cubic crystal structure, and in X-ray diffraction analysis using Cu k-α radiation, the cubic (200) peak exhibits a peak-to-background ratio of ≥2, preferably ≥3, more preferably ≥4, and most preferably ≥5. In X-ray diffraction analysis using Cu k-α radiation, the peak-to-background ratio of the cubic (200) peak of the (Ti,Al,Si)N layer is combined with any of a suitable lower limit of ≤15, preferably ≤10.

[0037] In one embodiment, the (Ti,Al,Si)N layer includes crystal planes passing through the (Ti,Al,Si)N layer, the crystal planes having variations in the content of the elements Ti, Al and Si in the (Ti,Al,Si)N layer.

[0038] In one embodiment, the surface roughness Ra of the (Ti,Al,Si)N layer is ≤0.05μm, preferably ≤0.03μm.

[0039] In one embodiment, the surface roughness Rz of the (Ti,Al,Si)N layer is ≤0.5μm, preferably ≤0.25μm.

[0040] In one embodiment, the Vickers hardness of the (Ti,Al,Si)N layer is ≥3500 HV (15mN load), preferably 3500 to 3800 HV (15mN load).

[0041] In one embodiment, the reduced Young's modulus of the (Ti,Al,Si)N layer is ≥420 GPa, preferably ≥450 GPa.

[0042] In one embodiment, the thermal conductivity of the (Ti,Al,Si)N layer is ≤3W / mK, preferably 1 to 2.5W / mK.

[0043] In one embodiment, the residual compressive stress of the (Ti,Al,Si)N layer is 4 to 9 GPa, preferably 5 to 8 GPa.

[0044] If the residual stress is too low, the coating will lack sufficient toughness. On the other hand, if the residual stress is too high, the coating will peel off.

[0045] The substrate of the coated cutting tool can be any type commonly found in the field of cutting tools used in metal machining. Suitable substrates are selected from cemented carbide, cermet, cubic boron nitride (cBN), ceramics, polycrystalline diamond (PCD), and high-speed steel (HSS).

[0046] In a preferred embodiment, the substrate is a cemented carbide.

[0047] The coated cutting tool is suitably in the form of an insert, drill bit, or end mill having at least one rake face and at least one flank face.

[0048] The (Ti,Al,Si)N layer according to the present invention is preferably a layer deposited by high-power pulsed magnetron sputtering (HIPIMS).

[0049] The coated cutting tool of the present invention is made by the following steps: providing one or more substrates, loading the one or more cemented carbide substrates into a PVD reactor, and depositing a coating comprising a (Ti,Al,Si)N layer as described herein by means of a suitable HIPIMS process.

[0050] More preferably, the HIPIMS process involves using a combination of at least two different target materials, said at least two different target materials being (Ti,Al) and (Ti,Al,Si). In the HIPIMS process, the peak pulse power density is preferably ≥340 W / cm². 2 The preferred average target power density is 20 to 50 W / cm³. 2 The pulse duration is preferably 1 to 5 ms, the pulse frequency is preferably 15 to 30 Hz, and the total pressure is preferably 0.35 to 0.7 Pa.

[0051] The substrate of the coated cutting tool can be any type commonly found in the field of cutting tools used in metal machining. The substrate is suitably selected from cemented carbide, cermet, cBN, ceramic, PCD, and HSS, with cemented carbide being preferred.

[0052] The one or more substrates are suitably in the form of cutting tool insert blanks, drill blanks or end mill blanks having at least one rake face and at least one flank face.

[0053] Further details on how the coated cutting tool according to the invention can be manufactured are given in the Embodiments section of this application. Attached Figure Description

[0054] Figure 1 A schematic diagram showing one embodiment of a cutting tool as a solid end mill is displayed.

[0055] Figure 2 A cross-sectional schematic diagram of one embodiment of the coated cutting tool of the present invention is shown, which shows the substrate and the coating.

[0056] Figure 3 The X-ray diffraction pattern from the θ-2θ scan of the (Ti,Al,Si)N layer of sample 1 (invention) is shown.

[0057] Figure 4The X-ray diffraction pattern from the θ-2θ scan of the (Ti,Al,Si)N layer of sample 2 (reference) is shown.

[0058] Figure 5 The X-ray diffraction pattern from the θ-2θ scan of the (Ti,Al,Si)N layer of sample 4 (reference) is shown.

[0059] Figure 6 The transmission electron microscope (TEM) electron diffraction image of the (Ti,Al,Si)N layer of sample 1 (invention) is shown.

[0060] Figure 7 The TEM electron diffraction image of the (Ti,Al,Si)N layer of sample 4 (reference) is shown.

[0061] Figure 8 High-resolution transmission electron microscopy (HR-TEM) images of the cross-section of the (Ti,Al,Si)N layer of Sample 1 (invention) are shown.

[0062] Figure 9 The image shown is an EDS line scan image of the (Ti,Al,Si)N layer from Sample 1 (Invention).

[0063] Figure 10 The results of cutting tests in milling operations of Sample 1 (Invention) and Sample 2 (Reference) are shown.

[0064] Detailed description of the embodiments in the accompanying drawings

[0065] Figure 1 A schematic diagram of one embodiment of a cutting tool (1) having a cutting edge (2) is shown. In this embodiment, the cutting tool (1) is an end mill. Figure 2 A cross-sectional schematic diagram of one embodiment of the coated cutting tool of the present invention, having a substrate (3) and a coating (4), is shown. The coating consists of a first innermost (Ti,Al)N layer (5) followed by a (Ti,Al,Si)N layer (6). Figure 8 A high-resolution transmission electron microscope (HR-TEM) image of a cross-section of one embodiment of the (Ti,Al,Si)N layer is shown. A layered structure is seen, where bright areas (7) and dark areas (8) represent different elemental compositions. A striped pattern from the crystal structure is also seen throughout the analyzed (Ti,Al,Si)N layer, thus the crystal planes pass through the bright areas (7) and dark areas (8). Figure 9 The image shows an EDS line scan of a (Ti,Al,Si)N layer according to the present invention. EDS scanning was performed on a cross-section of the (Ti,Al,Si)N layer to measure the content of different elements Ti, Al, Si, Ar, and N at different thicknesses of the (Ti,Al,Si)N layer.

[0066] method

[0067] X-ray diffraction:

[0068] X-ray diffraction patterns were acquired using a Panalytical Empyrean diffractometer in grazing incidence mode (GIXRD). Analysis was performed using line-focused Cu-Kα radiation (40 kV high voltage, 40 mA current). The incident beam was defined by a 2 mm mask and a 1 / 8° divergence slit, along with an X-ray mirror that generated a parallel X-ray beam. Lateral divergence was controlled by a Soler slit (0.04°). For the diffraction beam path, a 0-18° parallel plate collimator combined with a proportional counter (0D detector) was used. The measurements were performed in grazing incidence mode (ω = 1°). The 2θ range was approximately 20–80°, with a step size of 0.03° and a counting time of 10 s.

[0069] Electron diffraction in transmission electron microscopy (TEM)

[0070] In the electron diffraction analyses presented in this paper, these measurements were performed using a transmission electron microscope: a Zeiss 912 Omega High tension 120 kV. A 10 eV energy slit aperture was used. By using a selected area aperture, only the coating should contribute to the diffraction pattern. Parallel illumination for SAED (Self-Assisted Electron Diffraction) was employed during the TEM operation.

[0071] To eliminate amorphization during sample preparation, different methods can be used: i) classical preparation, including mechanical cutting, gluing, grinding and ion polishing, and ii) cutting the sample using FIB and lifting it out for final polishing.

[0072] Element content:

[0073] The content of metallic elements, nitrogen, and argon in the coating was measured on a cross-section of the FIB-prepared sample using a scanning transmission electron microscope (STEM) with energy-dispersive X-ray spectroscopy (EDX). For TEM imaging and EDX analysis, a JEOL ARM System instrument was used, equipped with an Oxford Instruments field emission gun, a secondary electron detector, and a Si(Li) energy-dispersive X-ray (EDX) detector. A spot size of 0.1 nm and a step size of 0.15 nm were used.

[0074] Vickers hardness:

[0075] Vickers hardness was measured using a Picodentor HM500 nanoindenter (load-depth map) at Helmut Fischer GmbH in Sindelfingen, Germany. For measurement and calculation, the Oliver-Pharr evaluation algorithm was applied, in which a diamond test piece according to Vickers hardness was indented into the layer, and the force-path curve was recorded during the measurement. The maximum load used was 15 mN (HV 0.0015), with loading and unloading periods of 20 seconds each, and a holding time (creep time) of 10 seconds. The hardness was calculated from this curve.

[0076] Reduced Young's modulus

[0077] The reduced Young's modulus (reduced elastic modulus) is determined by nanoindentation (load-depth map) as described in the determination of Vickers hardness.

[0078] thermal conductivity

[0079] The thermal conductivity of the coatings prepared in this paper was determined using the Time-Domain-Thermal Reflectance (TDTR) method, which has the following characteristics:

[0080] 1. Use laser pulses (intermittently) to locally heat the sample.

[0081] 2. Depending on thermal conductivity and heat capacity, heat energy is transferred from the sample surface toward the substrate. The surface temperature decreases over time.

[0082] 3. The portion of the laser light reflected depends on the surface temperature. A second laser pulse (probe pulse) is used to measure the temperature drop on the surface.

[0083] 4. By using a mathematical model, thermal conductivity can also be calculated using the heat capacity of the sample. See (DGCahill, Review of Scientific Instruments (Rev. Sci. Instr.) 75, 5119 (2004)).

[0084] Before measurement, the sample should be polished to a mirror-like finish.

[0085] Residual stress

[0086] Using sin 2The Ψ method (refer to ME Fitzpatrick, A. Fry, P. Holdway, FAKandil, J. Shackleton and L. Suominen – A Measurement Good Practice Guide No. 52; “Determination of Residual Stresses by X-ray Diffraction – Issue 2”, 2005) measures residual stress by XRD.

[0087] Using the tilt method (Ψ-geometry), the selected sin... 2 Eight Ψ angles equidistant within the Ψ range. Preferably, the Φ angles are equidistantly distributed within a Φ sector of 90°. For the calculation of residual stress values, Poisson's ratio = 0.20 and Young's modulus E = 450 GPa are applied. For the measurement of the (Ti,Al,Si)N layer, the data are evaluated by locating the (200) reflection of (Ti,Al,Si)N using commercially available software (RayfleX, version 2.503) via a quasi-isostrain fitting function. To measure the residual stress of a layer on which other deposited layers have been deposited, the coating material above the layer to be measured is removed. The method of material removal must be carefully selected and applied so as not to significantly alter the residual stress within the remaining (Ti,Al,Si)N multilayer material. A suitable method for removing the deposited coating material is polishing; however, gentle and slow polishing using a fine-grained polishing agent should be employed. As is known in the art, strong polishing using a coarse-grained polishing agent will instead increase compressive residual stress. Other suitable methods for removing deposited coating materials are ion etching and laser ablation.

[0088] Surface roughness

[0089] The average surface roughness Ra and average roughness depth Rz were measured using the P800 roughness measuring device from JENOPTIK Industrial Metrology Germany GmbH (formerly Hommel-ETamic GmbH) with the evaluation software TURBO WAVE V7.32. The waviness was determined according to ISO 11562, using a TKU300 sensor with a scan length of 4.8 mm and a KE590Gd test tip, at a speed of 0.5 mm / s. Example:

[0090] Example 1 (Invention):

[0091] Using Ti 0.50 Al 0.50 The target was used to deposit a starting layer of (Ti,Al)N onto a WC-Co type matrix. Then, a target with the composition Ti was used... 0.50 Al 0.50 The target and having Ti 0.35 Al 0.55 Si 0.10 The target is further deposited with a (Ti,Al,Si)N layer. The WC-Co matrix is ​​a milling cutter (nose end mill, 6 mm diameter) and a face insert (for easier coating analysis) using a milling cutter in HIPIMS mode on an Oerlikon Balzers Ingenia device with S3p technology. The matrix composition is 8 wt% Co and the balance WC.

[0092] The deposition process was operated in HIPIMS mode using the following process parameters.

[0093] Starting (Ti,Al)N layers:

[0094]

[0095]

[0096] Double rotation

[0097] A layer with a thickness of approximately 200 nm was deposited.

[0098] (Ti,Al,Si)N layer:

[0099]

[0100] Double rotation

[0101] A (Ti,Al,Si)N layer with a thickness of approximately 2 μm was deposited.

[0102] The coated cutting tool provided is referred to as "Sample 1 (Invention)".

[0103] Example 2 (reference):

[0104] From having composition Ti 0.40 Al 0.60The target deposits a (Ti,Al)N layer on a WC-Co type substrate, which is a milling cutting tool (head end mill, 6 mm diameter) and a face insert (for easy coating analysis) using an Oerlikon Balzers device employing S3p technology in HIPIMS mode. This HIPIMS-deposited coating is known to give very good results in the machining of hardened steel (ISO-H) materials.

[0105] The matrix is ​​composed of 8% by weight Co and the balance WC.

[0106] The deposition process was operated in HIPIMS mode using the following process parameters.

[0107]

[0108] Double rotation

[0109] A layer with a thickness of approximately 2 μm was deposited.

[0110] The coated cutting tool provided is referred to as "Sample 2 (Reference)".

[0111] Furthermore, from Ti 0.50 Al 0.50 The target deposits a (Ti,Al)N layer on a WC-Co type substrate, which is a planar cutting tool insert using the same Oerlikon Balzers apparatus with S3p technology and HIPIMS mode (for easy coating analysis). Process parameters are compared with those obtained from a substrate with a Ti composition. 0.40 Al 0.60 The process parameters were the same when the (Ti,Al)N layer was deposited on the target. A layer thickness of approximately 2 μm was deposited. The coated cutting tool provided is referred to as "Sample 3 (Reference)".

[0112] Example 3 (reference):

[0113] From having composition Ti 0.35 Al 0.55 Si 0.10 The target deposits a (Ti,Al,Si)N monolayer on a WC-Co type substrate, which is a planar cutting tool for easy coating analysis. Deposition was performed using the following process parameters in HIPIMS mode on an Oerlikon Balzers instrument employing S3p technology:

[0114]

[0115] Double rotation

[0116] A layer with a thickness of approximately 1.5 μm was deposited. The coated cutting tool provided is referred to as "Sample 4 (Reference)".

[0117] Example 4 (Analysis):

[0118] X-ray diffraction (XRD) θ-2θ analysis was performed on samples 1, 2 and 4.

[0119] Figures 3 to 6 The XRD θ-2θ diffraction patterns of Sample 1 (Invention), Sample 2 (Reference), Sample 2 (Reference) and Sample 4 (Reference) are shown.

[0120] As can be seen, the diffraction pattern of sample 1 (invention) reveals a cubic crystal structure. The diffraction pattern shows significant cubic (111) and cubic (200) peaks at approximately 37-38°2θ and approximately 42-43°2θ, respectively. This indicates significant crystallinity. The most intense peak is the (200) peak. The peak-to-background ratio of the (200) peak is estimated to be approximately 6.0.

[0121] The FWHM (full width at half maximum) of the cubic (200) peak is approximately 1.2°2θ.

[0122] The diffraction pattern of sample 2 (reference) shows a highly crystalline structure of a (Ti,Al)N monolayer. The (111) peak is more prominent here than the (200) peak, indicating a (111) crystal texture. There are no broad underlying reflections from the amorphous structure.

[0123] Finally, compared to Sample 1 (Invention), the diffraction pattern of Sample 4 (Reference) shows far less pronounced cubic (111) and cubic (200) peaks. The (111) peak is almost indistinguishable from a broad background reflection ranging from approximately 31 to 39°2θ. A similar broad background reflection ranging from approximately 40 to 45°2θ is also present, covering the location of the cubic (200) peak. These broad reflections imply the presence of a significant amorphous structure. The estimated peak-to-background ratio of only about 0.3 for the (200) peak indicates a much lower degree of crystallinity.

[0124] The full width at half maximum (FWHM) of the less prominent cubic (200) peak is very difficult to determine, but it is estimated to be approximately 4°2θ.

[0125] Electron diffraction analysis of Sample 1 (Invention) and Sample 4 (Reference) was performed using transmission electron microscopy (TEM). Figures 6 to 7 The obtained electron diffraction pattern is shown.

[0126] It can be seen that the pattern of the present invention displays obvious reflective spots at a specific scattering vector (distance from the center), proving the highly crystalline structure of sample 1 (the invention). On the other hand, for sample 4 (reference), a diffuse pattern indicating a significant amorphous phase is observed.

[0127] From high-resolution TEM (HR-TEM) images, see Figure 8 You can see the crystal planes passing through the modulation layer structure.

[0128] TEM-EDX line scan was performed on sample 1 (invention). Figure 9 The results are shown. It is clear that a modulation layer exists, exhibiting a gradual variation in the content of elements Ti, Al, and Si across the thickness of the layer between minimum and maximum contents. Therefore, the elemental content of each element has multiple maximum and minimum values ​​across the thickness of the layer.

[0129] In the periodic variations in the contents of the elements Ti, Al, and Si, the average minimum content of Ti is about 16 atoms, and the average maximum content of Ti is about 19 atoms.

[0130] In the periodic variations in the contents of the elements Ti, Al, and Si, the average minimum content of Al is about 21 atoms, and the average maximum content of Al is about 25 atoms.

[0131] In the periodic variations in the contents of the elements Ti, Al, and Si, the average minimum content of Si is about 1 atom, and the average maximum content of Si is about 3 atoms.

[0132] The content of element N varies between the minimum and maximum contents of each element along the thickness of the (Ti,Al,Si)N layer, with an average minimum content of N of about 54 atoms and an average maximum content of N of about 59 atoms.

[0133] All of the above minimum and maximum content values ​​can be obtained from... Figure 9 Extracted from TEM-EDS line scans.

[0134] The average content of each element in the (Ti,Al,Si)N layer was also analyzed using TEM-EDX. The results are shown in Table 1.

[0135] Table 1

[0136] element Ti Al Si N Ar Average content (atomic %) 17.9 23.1 1.8 56.8 0.4

[0137] The average composition of (Ti,Al,Si)N can also be written as: Ti 0.42 Al 0.54 Si 0.04 N x The sum of the atomic fractions of Ti, Al, and Si equals 1, and the atomic ratio of N to the metallic elements (Ti, Al, Si), i.e., "x", is approximately 1.3.

[0138] The average distance between two successive maximum values ​​and two successive minimum values ​​of the content of any of the elements Ti, Al, and Si is approximately 6 nm.

[0139] In the periodic variation of the contents of the elements Ti, Al and Si on the thickness of the (Ti,Al,Si)N layer, the maximum content of Ti, the minimum content of Al and the minimum content of Si on average are consistent on the thickness of the (Ti,Al,Si)N layer, and the minimum content of Ti, the maximum content of Al and the maximum content of Si on average are consistent on the thickness of the (Ti,Al,Si)N layer.

[0140] The average gradual variation of Ti content per unit distance of approximately 1 atom% / nm exists between the minimum and maximum contents and between the maximum and minimum contents in the (Ti,Al,Si)N layer thickness.

[0141] The average gradual variation of Al content per unit distance of approximately 1.3 atoms / nm exists between the minimum and maximum contents and between the maximum and minimum contents across the thickness of the (Ti,Al,Si)N layer.

[0142] The average Si content per unit distance varies gradually between the minimum and maximum contents and between the maximum and minimum contents over the thickness of the (Ti,Al,Si)N layer, with an average variation of approximately 0.7 atomic% / nm.

[0143] The residual stress of sample 1 (invention) was also measured, showing a value of -6.9 GPa.

[0144] Thermal conductivity was determined using the time-domain thermal reflectance (TDTR) method. The results are shown in Table 2.

[0145] Table 2

[0146]

[0147] The monolayer made from the target used to fabricate the modulation layer of sample 1 (invention) exhibits a thermal conductivity of 1.8 W / mK (for Ti). 0.35 Al 0.55 Si 0.10 N) and 4.7 W / mK (for Ti) 0.50 Al 0.50 The average value for N) is expected to be 3.3 W / mK. However, the result for Sample 1 (the invention) is 2.0 W / mK, meaning that Sample 1 has the advantage of low thermal conductivity in the heat-generating and intense metal cutting process.

[0148] Hardness measurements (load 15 mN) were performed on the flank face of the coated tools of Samples 1 and 4 to determine Vickers hardness and reduced Young's modulus (EIT). Table 3 shows the results.

[0149] Table 3

[0150] coating Hardness HV [Vickers] Reduced Young's modulus, EIT [GPa] Sample 1 (Invention) 3790 431 Sample 4 (reference) 2443 290

[0151] Example 5:

[0152] Cutting tests of Sample 1 (Invention) and Sample 2 (Reference):

[0153] Sample 1 (invention) and Sample 2 (reference), as end mills with a diameter of 6 mm, were tested in a milling experiment, and local flank wear was measured. The cutting conditions are summarized in Table 4. Hardened steel ISO-H was used as the workpiece material. Cutting operations on such a material generate particularly high heat at the cutting edge.

[0154] Cutting conditions:

[0155] Table 4

[0156] <![CDATA[Tooth feed rate f z [mm / tooth]]]> 0.09 <![CDATA[Cutting speed v c [m / min]]]> 185 <![CDATA[Cutting width a e [mm]]]> 0.12 (0.1 × tool diameter) <![CDATA[Cutting depth a p [mm]]]> 0.12 workpiece material ISO-H; 1.2379 (61 HRC)

[0157] In this experiment, the maximum wear was observed at the cutting edge on the flank side. Two cutting edges were tested for each coating, and the average cutting lengths are shown in Table 5.

[0158] Table 5

[0159]

[0160] Sample 2 (reference) has a coating that is known to give very good results in milling hardened steel (ISO-H) materials. However, it is concluded that Sample 1 (invention) performs much better than Sample 2 (reference). Figure 10 This also demonstrates that.

[0161] For sample 4, although no specific tests were conducted due to the poor mechanical properties (low hardness and low elastic modulus) of its (Ti,Al,Si)N layer, the results would be very poor in the aforementioned cutting tests.

Claims

1. A coated cutting tool comprising a substrate and a coating, said coating comprising a (Ti,Al,Si)N layer. Its features The (Ti,Al,Si)N layer comprises a periodic variation in the content of elements Ti, Al, and Si between the minimum and maximum content of each element along the thickness of the (Ti,Al,Si)N layer. - The average minimum content of Ti is 14 to 18 atomic%. - The average maximum content of Ti is 18 to 22 atomic%. - The average minimum content of Al is 18 to 22 atomic%. - The average maximum content of Al is 24 to 28 atomic%. - The average minimum Si content is 0 to 2 atomic%. - The average maximum Si content is 1 to 5 atomic%. - The residue in the (Ti,Al,Si)N layer consists of an inert gas and element N with an average content of 0.1 to 5 atomic percent. The average distance between two successive maximum values ​​and two successive minimum values ​​of any of the elements Ti, Al, and Si is 3 to 15 nm. In the periodic variation of the contents of the elements Ti, Al, and Si along the thickness of the (Ti,Al,Si)N layer, the maximum content of Ti, the minimum content of Al, and the minimum content of Si along the thickness of the (Ti,Al,Si)N layer are on average consistent, and the minimum content of Ti, the maximum content of Al, and the maximum content of Si along the thickness of the (Ti,Al,Si)N layer are on average consistent. There is an average gradual variation in the content of Ti per unit distance of 0.8 to 1.5 atomic % / nm between the minimum and maximum contents and between the maximum and minimum contents in the (Ti,Al,Si)N layer thickness; an average gradual variation in the content of Al per unit distance of 0.8 to 1.5 atomic % / nm between the minimum and maximum contents and between the maximum and minimum contents in the (Ti,Al,Si)N layer thickness; and an average gradual variation in the content of Si per unit distance of 0.3 to 0.8 atomic % / nm between the minimum and maximum contents and between the maximum and minimum contents in the (Ti,Al,Si)N layer thickness.

2. The coated cutting tool according to claim 1, wherein the average minimum content of Ti is 15 to 17 atoms.

3. The coated cutting tool according to claim 1, wherein the average maximum content of Ti is 19 to 21 atoms.

4. The coated cutting tool according to claim 1, wherein the average minimum content of Al is 19 to 21 atoms.

5. The coated cutting tool according to claim 1, wherein the average maximum content of Al is 25 to 27 atoms.

6. The coated cutting tool according to claim 1, wherein the average minimum content of Si is 0 to 1 atom.

7. The coated cutting tool according to claim 1, wherein the average maximum content of Si is 2 to 4 atoms.

8. The coated cutting tool according to claim 1, wherein the average gradual variation of the content of Ti per unit distance between the minimum and maximum contents and between the maximum and minimum contents over the thickness of the (Ti,Al,Si)N layer is 0.9 to 1.3 atomic% / nm, the average gradual variation of the content of Al per unit distance between the minimum and maximum contents and between the maximum and minimum contents over the thickness of the (Ti,Al,Si)N layer is 0.9 to 1.3 atomic% / nm, and the average gradual variation of the content of Si per unit distance between the minimum and maximum contents and between the maximum and minimum contents over the thickness of the (Ti,Al,Si)N layer is 0.5 to 0.7 atomic% / nm.

9. The coated cutting tool according to claim 1 or 2, wherein the inert gas is one or more of Ar, Kr or Ne.

10. The coated cutting tool according to claim 1 or 2, wherein the inert gas is Ar.

11. The coated cutting tool according to claim 1 or 2, wherein the average distance between two successive maximum values ​​and two successive minimum values ​​of any one of the elements Ti, Al and Si is 5 to 10 nm.

12. The coated cutting tool according to claim 1 or 2, wherein there is a variation in the content of element N between a minimum and a maximum content of each element on the thickness of the (Ti,Al,Si)N layer, wherein the average minimum content of N is 50 to 56 atomic%, and the average maximum content of N is 57 to 63 atoms.

13. The coated cutting tool according to claim 12, wherein the average minimum content of N is 51 to 55 atoms.

14. The coated cutting tool according to claim 12, wherein the average maximum content of N is 58 to 62 atoms.

15. The coated cutting tool according to claim 1 or 2, wherein an innermost layer of the coating is present immediately adjacent to the substrate, the innermost layer being a nitride of one or more elements belonging to Group 4, 5 or 6, or Al and a nitride of one or more elements belonging to Group 4, 5 or 6, the thickness of the innermost layer being less than 2 µm.

16. The coated cutting tool according to claim 1 or 2, wherein the (Ti,Al,Si)N layer comprises a cubic crystal structure, and wherein the FWHM (full width at half maximum) of the cubic (200) peak is 0.5 to 2.5°2θ in the θ-2θ scan of X-ray diffraction using Cu k-α radiation.

17. The coated cutting tool according to claim 1 or 2, wherein the (Ti,Al,Si)N layer comprises a cubic crystal structure and has a peak-to-background ratio of ≥2 for the cubic (200) peak in X-ray diffraction analysis using Cu k-α radiation.

18. The coated cutting tool according to claim 1 or 2, wherein the (Ti,Al,Si)N layer comprises a crystal plane passing through the (Ti,Al,Si)N layer, the crystal plane having a variation in the content of the elements Ti, Al and Si in the (Ti,Al,Si)N layer.

19. The coated cutting tool according to claim 1 or 2, wherein the Vickers hardness of the (Ti,Al,Si)N layer is ≥3500 HV under a load of 15 mN.

20. The coated cutting tool according to claim 1 or 2, wherein the reduced Young's modulus of the (Ti,Al,Si)N layer is ≥420 GPa.

21. The coated cutting tool according to claim 1 or 2, wherein the thermal conductivity of the (Ti,Al,Si)N layer is ≤3 W / mK.

22. The coated cutting tool according to claim 1 or 2, wherein the residual compressive stress of the (Ti,Al,Si)N layer is 4 to 9 GPa.

23. The coated cutting tool according to claim 1 or 2, wherein the substrate is selected from cemented carbide, cermet, cubic boron nitride (cBN), ceramic, polycrystalline diamond (PCD), and high-speed steel (HSS).

24. The coated cutting tool according to claim 1 or 2, wherein it is in the form of an insert, drill or end mill having at least one rake face and at least one flank face.

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