Coated Cutting Tools

Abstract

The present invention relates to a coated cutting tool including a substrate at least partially coated with a coating, the coating comprising a Ti(C,N) layer, an α-Al2O3 layer, and a bonding layer therebetween. The Ti(C,N) layer has a thickness of 3-20 μm and, viewed from the substrate toward the outer surface of the tool, has an inner Ti(C,N) portion T1 followed by an outer Ti(C,N) portion T2. ​​The inner portion T1 has a thickness of 2.5-15 μm, and the outer portion T2 has a thickness of 0.5-5 μm. The average grain width of the Ti(C,N) grains in T1 and T2 is less than 300 nm. The atomic ratio C / N of the inner Ti(C,N) portion T1 is 1.50-1.60, and the atomic ratio C / N of the outer Ti(C,N) portion T2 is 1.25-1.40.

Description

[Technical Field]

[0001] The present invention relates to a coated cutting tool comprising a substrate and a coating, the coating being deposited by chemical vapor deposition (CVD) and comprising a Ti(C,N) layer and an α-Al2O3 layer. [Background technology]

[0002] Coated cutting tools are well known in the metal cutting industry. CVD-coated and PVD-coated cutting tools are the two most common types of coated cutting tools. The advantage of these coatings is their high chemical and wear resistance, which is important for achieving a long tool life of the coated cutting tool. CVD coatings comprising a layer of Ti(C,N) along with a layer of alumina are known to perform well, for example, in turning or milling steel.

[0003] Recent studies have shown that the combination of very fine-grained Ti(C,N) and Al2O3 layers sometimes leads to poor adhesion between Ti(C,N) and Al2O3. Addressing this issue is of interest, as very fine-grained Ti(C,N) has shown promising performance for cutting tools.

[0004] It is an object of the present invention to provide a coated cutting tool for metal cutting that has high adhesion between the Ti(C,N) and Al2O3 layers of the coating. A further object is to provide a coated cutting tool that has high wear resistance, in particular high resistance to flaking during metal cutting. It is also an object of the present invention to provide a cutting tool that has high resistance to crater wear in steel metal machining.

[0005] Description of the Invention At least one of the above objects is achieved by a coated cutting tool according to claim 1. Preferred embodiments are disclosed in the dependent claims.

[0006] The present invention relates to a coated cutting tool having a substrate at least partially coated with a coating, the coating comprising a layer of Ti(C,N), a layer of α-Al2O3, and a bonding layer therebetween. The Ti(C,N) layer has a thickness of 3-20 μm, preferably 5-15 μm, and most preferably 6-10 μm, and is composed of columnar grains. The Ti(C,N) layer comprises, viewed from the substrate toward the outer surface of the tool, an inner Ti(C,N) portion T1 followed by an outer Ti(C,N) portion T2. ​​The inner portion T1 has a thickness of 2.5-15 μm, preferably 3-10 μm, and the outer portion T2 has a thickness of 0.5-5 μm, preferably 0.5-3.5 μm. The width of the Ti(C,N) crystal grains in the inner Ti(C,N) portion T1 is smaller than 300 nm, preferably smaller than 200 nm, and more preferably smaller than 100 nm, and the width of the Ti(C,N) crystal grains in the outer Ti(C,N) portion T2 is smaller than 300 nm, preferably smaller than 200 nm. The atomic ratio C / N in the inner Ti(C,N) portion T1 is 1.50 to 1.60, and the atomic ratio C / N in the outer Ti(C,N) portion T2 is 1.25 to 1.40, and preferably 1.27 to 1.36.

[0007] The Ti(C,N) segments T1 and T2 are defined by their C / N atomic ratios. Electron probe microanalysis (EPMA) line scans are used to determine the thicknesses of these segments based on the C / N ratio. The C / N atomic ratio is preferably approximately constant within each segment, i.e., the ratio can vary by approximately ±2%.

[0008] Surprisingly, it has been found that coated cutting tools comprising a fine columnar grain Ti(C,N) layer, the Ti(C,N) layer comprising two portions, one inner portion having a slightly higher carbon content than the outer portion, have increased crater wear resistance and also increased resistance to coating delamination.

[0009] In one embodiment of the present invention, the average grain width of the Ti(C,N) grains T1 in the inner Ti(C,N) portion is smaller than the average grain width of the Ti(C,N) grains in the outer Ti(C,N) portion T2, which is advantageous in that the outer portion has a larger grain width than the inner portion and contributes to the adhesion of the subsequent bonding layer.

[0010] In one embodiment of the present invention, the Ti(C,N) layer includes an outer portion T2 adjacent to the bond layer. The average grain width of the Ti(C,N) grains in the top section of T2 is 90 to 250 nm, preferably 100 to 200 nm. The T2 portion can contribute to improved adhesion between the bond layer and the subsequent α-Al2O3 layer. It has been found that if the average grain width in the top section of T2 is too large, the TC(0012) of the subsequently deposited α-Al2O3 layer decreases, although adhesion remains high. If the average grain width in the top section of T2 is too low, coating adhesion of the subsequent layer may decrease. The top section of T2 is the section of T2 closest to the bond layer. The average grain width of the Ti(C,N) grains adjacent to the bond layer, as used herein, refers to the average grain width of the Ti(C,N) grains measured along a line approximately 300 nm from the bond layer.

[0011] In one embodiment of the present invention, the average grain width of the Ti(C,N) grains in the inner Ti(C,N) portion T1 is <100 nm. Fine-grained Ti(C,N) may be advantageous as a wear-resistant layer, which may be due to its abundant grain boundaries or due to a smoother or more uniform thickness of the layer. Therefore, a relatively thick portion of the fine-grained TiCN layer is desirable.

[0012] In one embodiment of the present invention, the average grain size D of the Ti(C,N) portion T1 inside the Ti(C,N) layer 422 The particle size D is 25-50 nm as measured by X-ray diffraction with CuKα radiation. 422 is calculated from the full width at half maximum (FWHM) of the (422) peak by the Scherrer formula: TIFF2025535302000002.tif9170[where, D 422 is the average grain size of Ti(C,N), K is the shape factor (set here to 0.9), λ is the wavelength of CuKα radiation (set here to 1.5405 Å), and B 422 is the FWHM value of the (422) reflection, and θ is the Bragg angle] is calculated according to

[0013] It is difficult to study the average grain width of very fine-grained Ti(C,N). For example, in polished cross sections studied by SEM and EBSD, the recognition of grain orientation contrast differences and grain boundaries can be very low. Those skilled in the art are aware that if the amount of signal in the analysis is too low, the results are no longer reliable. We herein utilize XRD and the Scherrer equation to study even finer-grained Ti(C,N), for example, when the average grain width is less than 75 nm.

[0014] In one embodiment of the present invention, the thickness of the α-Al2O3 layer is 1 to 15 μm, preferably 3 to 9 μm.

[0015] The α-Al2O3 layer was determined by X-ray diffraction using CuKα radiation and θ-2θ scanning according to Harris equation (2): TIFF2025535302000003.tif10170 [where I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, I0(hkl) is the standard intensity according to ICDD PDF Card No 00-010-0173, n = number of reflections, and the reflections used are (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (2 1 4), (3 0 0), and (0 0 12)] 2. The coated cutting tool of claim 1, wherein the coated cutting tool exhibits a texture coefficient TC(hkl) defined according to: where TC(0 0 12) is the maximum texture coefficient. It has been found that a high TC(0 0 12) contributes to high crater wear resistance in metal cutting of steel.

[0016] In one embodiment of the present invention, the TC(0012) of the α-Al 2 O 3 layer is >7.7, preferably >7.8.

[0017] In one embodiment of the present invention, the α-Al2O3 layer comprises a portion A1 extending 1 μm from the bonding layer, the portion A1 being measured by electron backscatter diffraction (EBSD) on a cross section of the α-Al2O3 layer, wherein a surface normal of the α-Al2O3 layer is parallel to a surface normal of the substrate surface, and the portion A1 is within 15 degrees of the surface normal of the α-Al2O3 layer over ≥ 70%, preferably ≥ 80%, more preferably ≥ 90%, and most preferably ≥ 95% of the analyzed area. <001> Indicates a directional orientation.

[0018] In one embodiment of the present invention, the Ti(C,N) layer comprising the portions T1 and T2 has a refractive index determined by X-ray diffraction using CuKα radiation and a θ-2θ scan according to Harris equation (2): where I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, I0(hkl) is the standard intensity according to ICDD PDF Card No 42-1489, n is the number of reflections, and the reflections used in the calculation are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0), and (4 2 2). where TC(422)>3.

[0019] In one embodiment of the present invention, TC(422)+TC(311) is 5-6 for the Ti(C,N) layer.

[0020] In one embodiment of the present invention, the bond layer comprises at least one compound selected from the group consisting of titanium carboxylate, titanium oxynitride, and titanium carboxynitride. A bond layer comprising titanium carboxylate, titanium oxynitride, or titanium carboxynitride is advantageous in that it can provide an epitaxial relationship between the Ti(C,N) layer and the α-Al2O3 layer. The bottom layer is preferably a highly nitrogen-rich Ti(C,N) layer, preferably deposited at about 1000°C. The bond layer preferably has a thickness of 0.5 to 2 μm.

[0021] In one embodiment of the invention, the coating comprises an innermost layer of TiN, preferably having a thickness of 0.1 to 0.5 μm.

[0022] In one embodiment of the present invention, the substrate of the coated cutting tool is selected from the group of cemented carbides and cermets.

[0023] definition The term "cutting tool" is intended herein to denote a cutting tool, e.g. an insert, suitable for metal cutting applications. The field of application may be, for example, turning, milling or drilling of metals such as steel.

[0024] The cutting tool disclosed herein includes a substrate and a coating. The coated cutting tool may be an insert including a rake face, a flank face, and a cutting edge therebetween. The substrate, the coating, and these layers each have an outer surface. By "surface normal," or a normal to the outer surface, is meant a direction perpendicular to the surface plane of the outer surface, i.e., the preferred growth direction of the coating.

[0025] method Coating Deposition The coatings in the following examples were deposited on radial Ionbond Bernex® type CVD equipment 530, sized to accommodate 10,000 half-inch size cutting inserts.

[0026] C / N measurement by electron probe microanalysis (EPMA) To determine the C / N atomic ratio for parts T1 and T2 of the Ti(C,N) layer, elemental analysis of the coating was performed by electron microprobe analysis using a JEOL electron microprobe JXA-8530F equipped with a wavelength dispersive spectrometer (WDS). A Ti(C,N) reference sample (composition: 10.22 wt% C, 10.68 wt% N, 78.86 wt% Ti, and 0.24 wt% O) was used for calibration. Analysis of each Ti(C,N) layer section was performed on a polished cross-section of the coating on the rake face of a cutting tool. Titanium, carbon, and nitrogen mapping was performed across the entire thickness of the Ti(C,N) layer using 10 kV and 40 nA. The Ti, C, and N contents of parts T1 and T2 of the Ti(C,N) layer were measured at at least five different locations, separated by at least 5 μm in the center of the section. The thickness of each part T1 and T2 was determined by line scanning. The C / N atomic ratio is preferably approximately constant within each part, ie, the ratio may vary, for example, by about ±2% within a part.

[0027] Grain size of Ti(C,N) by XRD and Scherrer To determine the average grain size of Ti(C,N) grains smaller than approximately 75 nm, as seen in the lower portion of the Ti(C,N) layer, portion T1, in this embodiment of the present invention, X-ray diffraction (XRD) was performed on the flank surface using a PANalytical CubiX3 diffractometer equipped with a PIXcel detector. Because layers above the Ti(C,N) layer affect the X-ray intensity incident on the Ti(C,N) layer and exiting the entire coating, these must be corrected for, taking into account the linear absorption coefficients of each compound within the layer. Alternatively, layers above it, such as Ti(C,N) portion T2, can be removed by methods (e.g., grinding or laser ablation) that do not substantially affect the XRD measurement results.

[0028] The coated cutting tool was mounted in a specimen holder to ensure that the flank of the specimen was parallel to the reference plane of the specimen holder and at the appropriate height. Cu-Kα radiation was used for the measurements (voltage 45 kV, current 40 mA). A 1 / 2-degree anti-scatter slit and a 1 / 4-degree divergence slit were used. The diffraction intensity from the coated cutting tool was measured over the 2θ range of 20° to 140°, i.e., over an incidence angle θ of 10° to 70°. Data analysis (including background fitting, Cu-Kα2 stripping, and profile fitting of the data) was performed using PANalytical's X'Pert HighScore Plus software.

[0029] The integrated peak full width at half maximum of the profile fit curve obtained from PANalytical's X'Pert HighScore Plus software was used to calculate the layer grain size according to the Scherrer equation (Eq1) (Birkholz, 2006).

[0030] Then, the average particle size D 422 However, from the full width at half maximum (FWHM) of the (422) peak, the Scherrer formula: TIFF2025535302000004.tif9170[where, D 422 is the average grain size for Ti(C,N), K is the shape factor (set here to 0.9), λ is the wavelength of CuKα radiation (set here to 1.5405 Å), and B 422 is the FWHM value of the (422) reflection, and θ is the Bragg angle, i.e., the angle of incidence. is calculated according to

[0031] The FWHM obtained from the measurements contains both instrumental broadening and broadening due to small grain sizes. To compensate for this, a Gaussian approximation was used (Birkholz, 2006). 422 is the line broadening at FWHM (in radians) after subtracting the instrumental broadening (0.00174533 radians), and is given by equation (3): B 422 =√((FWHM obs ) 2 -(FWHM ins ) 2 ) (3) [In the formula, B 422 is the broadening (in radians) used for particle size calculations, and FWHM obs is the measured broadening (radians), FWHM ins is the instrument broadening (in radians). It is defined by:

[0032] Grain width measurement using electron backscatter diffraction (EBSD) The average grain width of the Ti(C,N) grains in the topmost zone T2 of the Ti(C,N) (approximately 300 nm from the bonding layer) is determined herein by the average grain intercept (AGI) method, which quantifies the grain width by drawing a line on a micrograph, counting the number of times the line crosses a grain boundary, and determining the ratio of the intercept to the length of the line. AGI = (number of segments) / (length of line).

[0033] To clearly determine the grain boundaries in the T2 section, electron backscatter diffraction (EBSD) was performed on the coating cross-section using a Zeiss Supra 55 equipped with an Oxford Instruments Symmetry EBSD detector. The coating cross-section was prepared using CNMG120408-PM inserts baked with AKASEL conductive black phenolic resin. The inserts were ground to approximately 1 mm and polished in two steps: coarse (9 μm) and fine (1 μm) polishing with diamond slurry, followed by a final polishing with colloidal silica. After the final polishing step, the inserts were removed from the conductive resin, washed with ethanol, dried with nitrogen, and mounted in a holder pre-tilted at 70° for EBSD analysis. The microscope was operated at an accelerating voltage of 15 kV, a beam current of 1.6 nA, and a working distance of 13–15 mm. To acquire the data, the detector was set to 622 × 512 pixels in binning mode to analyze an area of ​​at least 12 μm wide and 2 μm high, with a size increment of 15 nm. A line was placed approximately 300 nm from the bonding layer in this area, with a length of 12 μm. Three separate measurements were performed on different analyzed areas of the sample to obtain the average grain width. The Ti2CN (J Electrochem. Soc [JESOAN], (1950), vol. 97, pp. 299–304) crystal structure data was used as a reference for the Ti(C,N) phase, and 44 reflectors were used for the measurements. The average grain width of the Ti(C,N) grains in the area of ​​part T2 closest to the bonding layer was analyzed using Aztec software version 3.0 by defining a grain boundary misorientation of 10° in the EBSD (band contrast) map and counting the number of sections between the grain boundaries along the defined line.

[0034] Al2O3 at the bottom, orientation of part A1 In the present invention, the Al2O3 layer near the bonding layer is highly oriented. To analyze this region, a cross section of the coating was prepared, and the Al2O3 grains in section A1, extending 1 μm from the bonding layer, were examined in detail by EBSD. The polished cross section was prepared by mounting each CNMG120408-PM insert in AKASEL conductive black phenolic resin. The insert was then ground to approximately 1 mm and then polished in two stages: coarse polishing (9 μm) and fine polishing (1 μm) using a diamond slurry solution. A final polishing using colloidal silica solution was applied.

[0035] The orientation of the bottom of the Al2O3 is determined as the percentage of the analyzed area that is within a certain angular deviation from the set axis. For part A1, <001> The Al2O3 direction was chosen as the direction parallel to the surface normal. <001> It was calculated as the amount of the analyzed area that deviated ≤15° from the Al2O3 direction.

[0036] Areas at least 80 μm wide were analyzed in 50 nm increments using Speed ​​1 binning mode (622 × 512 px). To analyze the orientation of A1, four rectangular sections of A1 were randomly selected along the interface, each 10 μm wide and 1 μm high. The orientation was calculated as the average of the four rectangular sections. One automatic cleanup step and one zero solution deletion using five nearest neighbor levels were applied to the data. Aztec Crystal software (v 2.0) was used to determine the orientation.

[0037] The orientation of the A1 section was analyzed using a Zeiss Supra 55 and a Helios Nanolab 650, both equipped with Oxford-symmetry EBSD detectors. An accelerating voltage of 20 kV and a beam current of 13–26 nA were used. The sample was mounted in a sample holder pretilted at 70° to ensure maximum collection efficiency.

[0038] Alumina (α) (Acta Crystallogr, Sec B [ACBCAR], vol 49B pp. 973-980) was used as a reference for the determination of Al2O3, and 89 reflectors were used for the measurements.

[0039] SEM survey SEM examination of the polished cross-sections and the top surface of the samples was performed with a Carl Zeiss AG-Supra 40 type operating at an accelerating voltage of 3 kV and an aperture size of 30 μm. Images were acquired using a secondary electron detector. Layer thicknesses were measured on the cross-sectional SEM images.

[0040] X-ray diffraction measurements of Ti(C,N) and Al2O3 To investigate the texture of one or more layers, X-ray diffraction was performed on the flank face of the cutting tool insert using a PANalytical CubiX3 diffractometer equipped with a PIXcel detector. The coated cutting tool insert was mounted in a specimen holder, ensuring that the flank face of the cutting tool insert was parallel to the reference plane of the specimen holder and at the appropriate height. Cu-Kα radiation was used for the measurements at a voltage of 45 kV and a current of 40 mA. A 1 / 2-degree anti-scatter slit and a 1 / 4-degree divergence slit were used. The diffraction intensity from the coated cutting tool was measured over the range of 20° to 140° 2θ, i.e., over an incidence angle θ of 10° to 70°.

[0041] Data analysis (including background subtraction, Cu-Kα stripping, and profile fitting of the data) was performed using PANalytical's X'Pert HighScore Plus software. A general description of the fitting is as follows: In this case, the output from this program (integrated peak areas of the profile fit curve) is used to calculate the layer texture coefficient by comparing the ratio of the measured intensity data to the standard intensity data according to the PDF card of a specific layer (e.g., a Ti(C,N) or α-Al2O3 layer) using the previously disclosed Harris equation (2). Because the layer thickness is finite, the relative intensities of a pair of peaks at different 2θ angles will differ from those of a bulk sample due to differences in the optical path length through the layer. Therefore, when calculating the TC value, a thin-film correction was applied to the integrated peak area intensity extracted for the profile fit curve, taking into account the linear absorption coefficient of the layer. For example, additional layers that may be present above the α-Al2O3 layer will affect the X-ray intensity entering the α-Al2O3 layer and exiting the entire coating, so corrections must also be made for these, taking into account the linear absorption coefficients of each compound within the layer. The same applies to X-ray diffraction measurements of a Ti(C,N) layer, if the Ti(C,N) layer is located, for example, underneath an α-Al2O3 layer. Alternatively, further layers, such as TiN, located above the alumina layer can be removed by methods that do not substantially affect the XRD measurement results, such as chemical etching.

[0042] To investigate the texture of the α-Al2O3 layer, CuK αX-ray diffraction was performed using radiation, and the texture coefficient TC(hkl) for the different growth directions of the columnar grains in the α-Al2O3 layer was calculated according to the Harris equation (2), where I(hkl) = the measured (integrated area) intensity of the (hkl) reflections, I0(hkl) = the standard intensity according to ICDD PDF card number 00-010-0173, and n = the number of reflections used in the calculation. In this case, the (hkl) reflections used are (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (2 1 4), (3 0 0), and (0 0 12). The measured integrated peak areas were thin-film corrected and corrected for the additional layers above (i.e., on top of) the α-Al2O3 layer, after which the ratios were calculated.

[0043] The texture coefficients TC(hkl) for different growth directions of the columnar grains in the Ti(C,N) layer were calculated according to the Harris equation (2) previously disclosed, where I(hkl) is the measured (integrated area) intensity of the (hkl) reflections, I0(hkl) is the standard intensity according to ICDD PDF card number 42-1489, and n is the number of reflections used in the calculation. In this case, the (hkl) reflections used are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0), and (4 2 2).

[0044] It should be noted that peak overlap is a phenomenon that can occur in the X-ray diffraction analysis of, for example, coatings comprising multiple crystalline layers and / or coatings deposited on substrates comprising crystalline phases, and that needs to be taken into account and compensated for. The overlap of peaks from the α-Al2O3 layer with peaks from the Ti(C,N) layer can affect the measurement and needs to be taken into account. It should also be noted that, for example, WC in the substrate may have diffraction peaks close to the relevant peaks of the present invention.

[0045] Embodiments of the present invention will now be described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0046] [Figure 1]1 shows a scanning electron microscope (SEM) image across a cross section of sample 090, an example of a coating according to the present invention, showing portions T1 and T2 of the Ti(C,N) layer, the tie layer (B), the substrate (S), and portion A1 of the α-Al2O3 layer. [Figure 2] An enlarged image of the T2 portion of the sample shown in FIG. 1 is shown. [Figure 3] 1 shows a scanning electron microscope (SEM) image across a cross section of sample 045, an example of a coating according to the present invention. [Figure 4] An enlarged image of the T2 portion of the sample shown in FIG. 3 is shown. [Figure 5] 1 shows a scanning electron microscope (SEM) image across a cross section of a reference sample (Ref 0). [Figure 6] An enlarged image of the outer portion of the Ti(C,N) layer of the sample shown in FIG. 5 is shown. [Figure 7] 1 shows a scanning electron microscope (SEM) image across a cross section of a reference sample (Ref260). [Figure 8] An enlarged image of the outer portion of the Ti(C,N) layer of the sample shown in FIG. 7 is shown. [Figure 9] A forward scattering image acquired from a central low forward scattering detector (FSD) on an EBSD camera of a cross section of sample 130, an example of a coating according to the present invention, provides orientation contrast and reveals the grain structure on the Ti(C,N) layer, showing portions T1 and T2 of the Ti(C,N) layer, the tie layer (B), the substrate (S), and portion A1 of the α-Al2O3 layer. [Figure 10] EBSD band contrast image of sample 130 reveals the grain structure, with dark areas corresponding to low band contrast values ​​and light areas corresponding to high band contrast values. [Figure 11] Carbon mapping from EPMA of sample 090 is shown, showing portions T1 and T2 of the Ti(C,N) layer, the tie layer (B), the substrate (S), and portion A1 of the α-Al2O3 layer. [Figure 12] 1 shows nitrogen mapping from EPMA of sample 090. [Figure 13] 1 shows carbon mapping from EPMA of sample 130. [Figure 14] Nitrogen mapping of sample 130 is shown. [Figure 15] 1 shows a schematic diagram of one embodiment of a cutting tool (1) having a rake face (2), a flank face (3) and a cutting edge therebetween. [Example]

[0047] Exemplary embodiments of the present invention are disclosed in more detail below and compared with reference embodiments: Coated cutting tools were manufactured, analyzed and tested in metal cutting tests.

[0048] Base material The cemented carbide substrate was manufactured using conventional processes, including milling, mixing, spray drying, pressing, and sintering. The ISO type geometry of the cemented carbide substrate (insert) was CNMG-120408-PM. The cemented carbide composition was 7.2 wt% Co, 2.9 wt% TaC, 0.5 wt% NbC, 1.9 wt% TiC, 0.4 wt% TiN, and the balance was WC.

[0049] Prior to the deposition of the coating, the substrate was subjected to a mild blasting treatment to remove residues from the sintering process on the substrate surface.

[0050] CVD deposition The sintered substrates were CVD coated in a Bernex Type 530 radial CVD reactor large enough to accommodate 10,000 half-inch cutting inserts. The samples to be tested and further analyzed were selected from the center of the chamber along half the plate radius between the center and periphery of the plate. Mass flow controllers should be selected such that the flow rate of CH3CN, for example, is selected to accommodate the flow rate of the CVD recipe.

[0051] An initial innermost coating of approximately 0.3 μm of TiN was deposited on all substrates using a deposition temperature of 885° C. and a pressure of 400 mbar. A gas mixture of 48.8 volume percent (vol%) H, 48.8 vol% N, and 2.4 vol% TiCl was used.

[0052] This was followed by the deposition of a Ti(C,N) layer, and all samples were deposited with different Ti(C,N) recipes as follows: Reference sample Ref260 was deposited by process step V followed by process step W as shown in Table 1; the Ti(C,N) layer of reference sample Ref0 was deposited by process step X as shown in Table 1; For samples 015, 020, 030, 045, 090, and 130, the Ti(C,N) layer was deposited by process step X followed by process step Z, using the deposition times shown in Tables 1 and 2. A temperature adjustment from 885°C to 870°C was performed with 250 vol% H and 250 vol% N at 80 mbar, after which process step X of the relevant sample was started. The layer thicknesses of the samples are shown in Table 4.

[0053] TIFF2025535302000005.tif101170

[0054] TIFF2025535302000006.tif64170

[0055] Tie layers with thicknesses ranging from 0.7 to 1.1 μm were deposited on the Ti(C,N) layer at 1000 °C using a process consisting of four distinct reaction steps: an 8-minute HTCVD Ti(C,N) step using TiCl, CH, N, HCl, and H at 400 mbar, followed by a 7-minute Ti(C,N,O) step (Ti(C,N,O)-1) using TiCl, CHCN, CO, N, and H at 70 mbar, followed by a 5-minute Ti(C,N,O) step (Ti(C,N,O)-2) using TiCl, CHCN, CO, N, and H at 70 mbar, and finally a 6-minute TiN step (TiCl, N, and H) using TiCl, N, and H at 70 mbar. During the third deposition step, the CO gas flow was continuously increased linearly from the start value of the process step to the stop value at the end of the process step, as shown in Table 3. All other gas flow rates were kept constant, but the overall gas flow rate was increased, which affected the concentrations of all gases to some extent. The bonded layer was then oxidized in a mixture of CO, CO, N, and H for 4 minutes prior to the initiation of AlO nucleation.

[0056] The details of the tie layer deposition are given in Table 3.

[0057] TIFF2025535302000007.tif70170

[0058] An α-Al2O3 layer was deposited on top of the tie layer. All α-Al2O3 layers were deposited in two steps at 1000 °C and 55 mbar. The first step was performed for 30 minutes using 1.2 vol% AlCl3, 4.7 vol% CO2, 1.8 vol% HCl, and the balance H2, resulting in approximately 0.1 μm of α-Al2O3. The process time for the second step was adjusted to achieve a total thickness of approximately 5 μm for the α-Al2O3 layer. The second step of the α-Al2O3 layer was deposited using 1.16% AlCl3, 4.65% CO2, 2.91% HCl, 0.58% H2S, and the balance H2.

[0059] Coating analysis results The layer thickness was measured on the rake face of the cutting tool samples using a scanning electron microscope. The layer thickness of the samples is shown in Table 4.

[0060] TIFF2025535302000008.tif94170

[0061] The thicknesses of the inner and outer parts T1 and T2 were measured in cross section using both line scan and elemental mapping with EPMA and SEM. It should be noted that the bond layer of the specimen contains a HT-Ti(C,N) sublayer (which is very common in the art for Ti(C,N) and α-Al2O3 coated cutting tools), and that this HT-Ti(C,N) sublayer is highly nitrogen-rich.

[0062] For the Ref0 samples, the average particle size was measured by XRD using the Scherrer equation, and it was concluded that the average particle size T1 for all samples was about 30 nm.

[0063] The average grain size range of the Ti(C,N) grains in part T2 of the Ti(C,N) layer was measured using the method disclosed in the Methods section above, and the results are shown in Table 5.

[0064] The determination of C and N contents was carried out according to the above method. The atomic percentages of the elements were used to calculate the ratios.

[0065] TIFF2025535302000009.tif132170

[0066] The texture coefficients of the Ti(C,N) and α-Al2O3 layers were analyzed by X-ray diffraction, and the results are shown in Table 6.

[0067] EBSD measurements were carried out on the internal alumina (A1). The orientation of the α-Al2O3 grains in the α-Al2O3 layer in the internal part A1 was analyzed. The results are shown in Table 6.

[0068] TIFF2025535302000010.tif125170

[0069] Performance Test The cutting tools were first evaluated by subjecting them to an abrasive wet blasting treatment. The blasting was performed on the rake face of the cutting tool. The blasting slurry consisted of 20% alumina by volume in water. The angle between the rake face of the cutting insert and the direction of the blasting slurry was 90°. The distance between the gun nozzle and the insert surface was approximately 145 mm. The slurry pressure on the gun was 1.8 bar for all samples, and the air pressure on the gun was 2.2 bar. The alumina grit was F230 mesh (FEPA 42-2:2006). The average time per unit area was 4.4 seconds. Sample Ref0 did not withstand the wet blasting, and the coatings of samples 015 and 020 showed severe white spotting. All other samples, 030, 045, 090, 130, and Ref260, actually withstood the wet blasting treatment, with no white spotting on the coatings.

[0070] The as-coated cutting tools were also tested in face turning (from 180 mm diameter to 60 mm diameter) of the workpiece material DIN C45E (medium carbon alloy steel). The spindle speed was fixed at n = 120 rpm. Thus, the cutting speed constantly varied along the face turning process from Vc approximately 70 m / min (180 mm diameter) to Vc approximately 20 m / min (60 mm diameter). The feed Fn constantly increased along the face turning process from 0.1 mm / rev (180 mm diameter) to 0.5 mm / rev (60 mm diameter). The depth of cut was 2 mm, and no cutting fluid was used. Four specimens of each variation were used in this test.

[0071] To measure the total area of ​​Ti(C,N) exposed on the rake face after end turning, the inserts were etched in a HCl (hydrochloric acid) solution for 15 minutes. This sequence involved SEM examination of the top surface using a Zeiss AG-Supra 40 type microscope operating at an accelerating voltage of 10 kV and a 30 μm aperture size. Images were acquired at 50x magnification using a backscattered electron detector. The images were then used to measure the area of ​​the spalled coating using image analysis software; a larger area indicated greater wear due to loss of adhesion of the α-Al2O3 layer.

[0072] The as-coated cutting tools were further tested in longitudinal turning of the workpiece material Ovako 825B (100CrMo7-3) (high alloy steel). The cutting speed Vc was 220 m / min, the feed fn was 0.3 mm / rev, and the depth of cut was 2 mm, using a water-miscible cutting fluid. Cutting continued for 14 minutes, after which the cutting tool wear was evaluated. One cutting edge per cutting tool was evaluated.

[0073] The cutting tools were evaluated for wear after the longitudinal cutting tests. To measure the total area of ​​exposed Ti(C,N) on the rake face, a top-side SEM examination was performed using a Zeiss AG-Supra 40 type microscope operating at an accelerating voltage of 10 kV with an aperture size of 30 μm. Several images were acquired at 250x magnification using a backscattered electron detector. These images were then used to measure the area of ​​exposed Ti(C,N) using image analysis software. Here, a larger measured area corresponds to greater wear.

[0074] The wear after longitudinal turning was also investigated by cross-sectioning the crater area. An FEI Helios FIB / SEM instrument was used to generate controlled cross-sections parallel to the chip flow direction on the rake face. The cross-sections were precisely positioned 550 μm from the primary edge and 320 μm from the secondary edge, measuring 150 μm in length and approximately 18 μm in depth, revealing the entire coating and a portion of the substrate. To protect the surface from ion beam damage, a thin layer of Pt approximately 100 nm thick was first deposited on the surface (150 μm in length and 3.5 μm in width) using an electron beam. A thicker Pt layer (approximately 3 μm thick) was then deposited on top of it using Ga ion assistance. The cross-sections were prepared in two steps: rough ion milling using a regular cross-section pattern with a 47 nA ion beam, followed by fine ion milling using a cleaning cross-section pattern with a 9.2 nA ion beam. Using image analysis software, the cross section is then used to measure the area of ​​the Ti(C,N) layer, where a larger area of ​​the Ti(C,N) layer corresponds to less wear.

[0075] The results of the cutting tests are shown in Table 7.

[0076] TIFF2025535302000011.tif100170

[0077] As can be seen from Table 7, all samples 030, 045, 090, and 130 had higher resistance to crater wear compared to the Ref260 reference sample.

[0078] While the invention has been described in connection with various exemplary embodiments, it is to be understood that the invention is not to be limited to the disclosed exemplary embodiments, and it is intended to cover various modifications and equivalent arrangements within the scope of the appended claims.

Claims

1. A coated cutting tool comprising a substrate at least partially coated by a coating, wherein the coating comprises a Ti(C,N) layer, α-Al ２ O ３ The Ti(C,N) layer, comprising layers and a bonding layer between them, having a thickness of 3 to 20 μm, preferably 5 to 15 μm, most preferably 6 to 10 μm, is composed of columnar crystalline grains, and the Ti(C,N) layer, viewed in the direction from the substrate toward the outer surface of the tool, comprises an inner Ti(C,N) portion T1 followed by an outer Ti(C,N) portion T2, the thickness of the inner portion T1 being 2.5 to 15 μm, preferably 3 to 10 μm, and the thickness of the outer portion T2 being 0.5 to 5 μm, preferably 0.5 to 3.5 μm, and the inner Ti(C,N) portion T1 A coated cutting tool wherein the average grain width of the Ti(C,N) crystal grains in portion T1 is less than 300 nm, preferably <200 nm, more preferably <100 nm; the average grain width of the Ti(C,N) crystal grains in portion T2 is less than 300 nm, preferably <200 nm; the atomic ratio C / N in portion T1 is 1.50 to 1.60; and the atomic ratio C / N in portion T2 is 1.25 to 1.40, preferably 1.27 to 1.

36.

2. The coated cutting tool according to claim 1, wherein the average grain width of the Ti(C,N) crystal grains in the inner Ti(C,N) portion T1 is smaller than the average grain width of Ti(C,N) in the outer Ti(C,N) portion T2.

3. The coated cutting tool according to claim 1, wherein the Ti(C,N) layer comprises an outer portion T2 adjacent to the bonding layer, and the Ti(C,N) crystal grains in the uppermost region of T2 have an average crystal grain width of 90 to 250 nm, preferably 100 to 200 nm.

4. The coated cutting tool according to claim 1, wherein the average grain width of the Ti(C,N) crystal grains in the inner Ti(C,N) portion T1 is <100 nm.

5. Average grain size D of the Ti(C,N) portion T1 inside the Ti(C,N) layer ４２２ However, measured by X-ray diffraction using CuKα emission, the grain size is 25-50 nm, and the grain size is D ４２２ (422) From the full width at half maximum (FWHM) of the peak, Scherrer's formula is: [In the formula, D ４２２ λ is the average grain size of Ti(C,N), K is the shape factor (set to 0.9 here), λ is the wavelength of CuKα emission (set to 1.5405 Å here), B ４２２ (422) is the FWHM value of the reflection, and θ is the Bragg angle. A coated cutting tool according to claim 1, calculated according to the following:

6. α-Al ２ O ３ The coated cutting tool according to claim 1, wherein the thickness of the layer is 1 to 15 μm, preferably 3 to 9 μm.

7. α-Al ２ O ３ The layer was measured by X-ray diffraction using CuKα radiation and θ-2θ scan, and the texture coefficient TC(hkl) defined according to the Harris formula: [In the formula, I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, and I ０ (hkl) is a standard intensity according to ICDD PDF card No. 00-010-0173, where n = number of reflections, and the reflections used are (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (2 1 4), (3 0 0), and (0 0 12). The coated cutting tool according to claim 1, wherein TC(0 0 12) is the maximum texture coefficient.

8. α-Al ２ O ３ The coated cutting tool according to claim 1, wherein the TC(0012) of the layer is >7.7, preferably >7.

8.

9. The α-Al ２ O ３ The layer includes a portion A1 extending 1 μm from the binding layer, and this portion A1 is made of the α-Al ２ O ３ Measured by electron backscatter diffraction (EBSD) on the cross-section of the layer, α-Al ２ O ３ The surface normal of the layer is parallel to the surface normal of the substrate surface, and portion A1 is such that ≥70%, preferably ≥80%, more preferably ≥90%, and most preferably ≥95% of the analyzed region is α-Al ２ O ３ A coated cutting tool according to claim 1, exhibiting an orientation having a <001> direction within 15 degrees from the surface normal of the layer.

10. The Ti(C,N) layer was measured by CuKα emission and X-ray diffraction using θ-2θ scanning, and the Harris equation (2) is obtained [wherein I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, and I ０ The coated cutting tool according to claim 1, wherein (hkl) is the standard intensity in accordance with ICDD PDF card No. 42-1489, n is the number of reflections, and the reflections used in the calculation are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0), and (4 2 2), and TC(4 2 2) > 3.

11. A coated cutting tool according to claim 1, wherein the Ti(C,N) layer has TC(422) + TC(311) of 5 to 6.

12. The coated cutting tool according to claim 1, wherein the bonding layer comprises at least one compound selected from the group consisting of carboxylated titanium, oxynitride titanium, and carboxynitride titanium, and preferably the thickness of the bonding layer is 0.5 to 2 μm.

13. The coated cutting tool according to claim 1, wherein the coating comprises the innermost layer of TiN and preferably has a thickness of 0.1 to 0.5 μm.

14. The coated cutting tool according to claim 1, wherein the base material of the coated cutting tool is selected from the group consisting of cemented carbide and cermet.

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