Cutting tool

Abstract

This invention relates to a cutting tool comprising a substrate (1) at least partially coated with a coating, the substrate (1) being made of cemented carbide or cermet, the coating comprising one or more layers, wherein at least one layer is a κ-Al2O3 layer (3) with a thickness of 3-6 μm, wherein the κ-Al2O3 layer (3) is composed of grains, and wherein the grain width is the width of the grains in a direction parallel to the surface of the substrate (1), and wherein the average grain width (d) of the κ-Al2O3 grains is... b The measurement is taken along a line corresponding to 80% of the thickness of the κ-Al2O3 layer (3), and the average grain width (d) of the κ-Al2O3 grains is... a The measurement is taken along a line 1 μm from the innermost κ-Al₂O₃ interface, characterized by the ratio d. b / d a Between 1.45 and 2.00.

Description

Technical Field

[0001] This invention relates to a coated cutting tool. The cutting tool is CVD coated, and the substrate is cemented carbide or cermet, and the CVD coating includes a TiCN layer and a κ-Al2O3 layer. Background Technology

[0002] In the field of cutting tool technology for metalworking, CVD coating is a well-known method for enhancing tool wear resistance. Commonly used CVD coatings include those made of TiN, TiC, TiCN, and Al2O3.

[0003] The wear resistance of Al2O3 coatings is influenced by their crystal structure, with κ-Al2O3 and α-Al2O3 coatings being the most commonly used. During processing, the wear characteristics of κ-Al2O3 and α-Al2O3 coatings typically differ, thus their respective application areas may also differ.

[0004] EP0753602 A1 discloses a cutting tool comprising a κ-Al2O3 coating having a preferred crystal growth orientation, thereby producing a {210} texture, which exhibits enhanced wear resistance in the machining of ball bearing steel.

[0005] One object of the present invention is to provide a cutting tool with extended life in metal cutting. Another object of the present invention is to provide a cutting tool with high resistance to flank wear and chipping during metal cutting of steel. Summary of the Invention

[0006] At least one of the above objectives is achieved by the cutting tool according to claim 1. Preferred embodiments are disclosed in the dependent claims.

[0007] This invention relates to a cutting tool comprising a substrate at least partially coated with a coating, the substrate being made of cemented carbide or cermet, the coating comprising one or more layers, wherein at least one layer is a κ-Al2O3 layer with a thickness of 3-6 μm, wherein the κ-Al2O3 layer is composed of grains, and wherein the grain width is the width of the grains in a direction parallel to the surface of the substrate, and wherein the average grain width db of the κ-Al2O3 grains is measured along a line corresponding to 80% of the thickness of the κ-Al2O3 layer, and wherein the average grain width da of the κ-Al2O3 grains is measured along a line at a distance of 1 μm from the innermost κ-Al2O3 interface, characterized in that the ratio db / da is between 1.45 and 2.00.

[0008] In one embodiment of the invention, the ratio db / da is between 1.48 and 1.80.

[0009] The coating of the present invention allows for the application of a strong wet blasting process, thereby expanding the application range of the κ-Al2O3 coating.

[0010] Surprisingly, it was found that cutting tools with a coating exhibited enhanced resistance to sandblasting and enhanced resistance to flank wear in milling stainless steel, wherein the coating comprises a κ-Al2O3 layer with grains having the aforementioned ratio.

[0011] A κ-Al2O3 layer with a thickness of less than 3 μm is disadvantageous because it limits wear resistance; while a κ-Al2O3 layer with a thickness of more than 6 μm is also disadvantageous because it increases the cutting radius of the cutting tool.

[0012] In one embodiment, the substrate of the coated cutting tool is composed of cemented carbide comprising 7-14 wt% Co (e.g., 11-13 wt% Co), 0.5-0.8 wt% Cr, with the balance being WC.

[0013] The cutting tool is preferably an indexable cutting insert, such as a milling insert, a turning insert, or a drilling insert. Alternatively, the cutting tool is preferably a drill bit or an end mill.

[0014] A cutting tool includes a rake face and a flank face, as well as a cutting edge located between the rake face and the flank face.

[0015] In one embodiment of the invention, the residual stress measured by XRD in the κ-Al2O3 layer is between -0.6 GPa and -2.0 GPa, preferably between -1.0 GPa and -1.5 GPa.

[0016] In one embodiment of the invention, the average grain width db of the κ-Al2O3 grains, measured along a line extending parallel to the surface of the substrate and at a location corresponding to 80% of the thickness of the κ-Al2O3 layer, is between 0.6 µm and 0.8 µm, preferably between 0.65 µm and 0.70 µm. Herein, the location corresponding to 80% of the thickness of the κ-Al2O3 layer refers to the position viewed from the surface of the substrate toward the outer surface of the coating, i.e., the position in the growth direction of the κ-Al2O3 layer. The location corresponding to 80% of the thickness of the κ-Al2O3 layer is a position relatively close to the outermost surface of the κ-Al2O3 layer.

[0017] In one embodiment of the invention, the average grain width da of the κ-Al2O3 grains, measured along a line extending parallel to the surface of the substrate and at a distance of 1 μm from the innermost κ-Al2O3 interface, is between 0.4 μm and 0.5 μm, preferably between 0.40 μm and 0.45 μm. The innermost κ-Al2O3 interface is the lowermost interface of the κ-Al2O3 layer, typically the interface with the adhesive layer.

[0018] In one embodiment of the present invention, the thickness of the κ-Al2O3 layer is between 4 μm and 5 μm.

[0019] In one embodiment of the present invention, the coating includes a TiCN layer located between the substrate and the κ-Al2O3 layer, preferably, the thickness of the TiCN layer is between 1.5 μm and 2.5 μm.

[0020] In one embodiment of the present invention, the coating includes an innermost TiN layer, preferably having a thickness between 0.3 μm and 0.6 μm.

[0021] In one embodiment of the present invention, the coating includes an adhesive layer located between the TiCN layer and the κ-Al2O3 layer. Preferably, the adhesive layer is one or more of TiCO, TiCNO, AlTiCO, and AlTiCNO. More preferably, the thickness of the adhesive layer is between 1.5 μm and 2.5 μm.

[0022] In one embodiment of the invention, the surface roughness Ra of the substrate at the rake face, measured in a SEM cross-section, is between 0.05 μm and 0.2 μm, preferably between 0.15 μm and 0.2 μm. It has been shown that Ra in the range of 0.05 μm to 0.2 μm is advantageous for providing wear-resistant coated cutting tools.

[0023] In one embodiment of the invention, the κ-Al₂O₃ layer exhibits a texture coefficient TC(hkl), which is measured using Cu Kα radiation and θ-2θ scanning X-ray diffraction and is defined according to the Harris formula:

[0024] Where I(hkl) is the measured intensity (integral area) of the (hkl) reflection, I0(hkl) is the standard intensity, where I0(11 1) = 105, I0(0 1 3) = 5026, I0(1 2 2) = 10000, I0(1 1 3) = 1116, I0(2 0 0) = 795, I0(2 0 1) = 1342, I0(0 0 4) = 291, I0(0 4 0) = 387, I0(0 1 5) = 429 and I0(2 04) = 1312, n is the number of reflections used in the calculation, where the (hkl) reflections used are (1 1 1), (0 13), (1 2 2), (1 1 3), (2 0 0), (2 0 1), (0 0 4), (0 4 0), (0 1 5) and (2 0 4), wherein TC(0 0 4) + TC(0 1 5) ≥ 6, preferably ≥ 7, more preferably ≥ 8.

[0025] In one embodiment of the invention, the TiCN layer exhibits a texture coefficient TC(hkl), as measured by X-ray diffraction using Cu Kα radiation and θ-2θ scanning, defined according to Harris formula (F1), where I(hkl) is the measured intensity (integral area) of the (hkl) reflection, I0(hkl) is the standard intensity, where I0(1 1 1) = 7871, I0(2 0 0) = 10000, I0(2 2 0) = 5369, I0(3 1 1) = 2550, I0(3 3 1) = 1128, I0(4 2 0) = 2366, I0(42 2) = 2479, and I0(5 1 1) = 1427, n is the number of reflections used in the calculation, and where the (hkl) reflections used are (1 1 1), (2 0) 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0), (4 2 2), (5 11), where TC(4 2 2)≥3, preferably ≥4, more preferably ≥5.

[0026] In one embodiment of the present invention, the cutting tool comprises an innermost TiN layer of 0.3-0.5 μm, a TiCN layer of 1.5-2.5 μm, an AlTiCNO bonding layer of 1.5-2.5 μm, and a κ-Al2O3 layer of 3-6 μm.

[0027] Other objects and features of the invention will become apparent from the following definitions and embodiments taken in conjunction with the accompanying drawings.

[0028] method

[0029] Grain width measurement

[0030] At 80% of the layer thickness (i.e., 20% from the top surface of the layer) (d b ) and at 1 μm above the lower interface (d a The average grain width of the κ-Al₂O₃ grains was determined. The grain intercept method was used, where the average grain width was determined by measurements of the grain width along a 25 μm line on the SEM image. Images of the fracture cross-section on the rake face of the coated cutting tool were acquired using a Zeiss Ultra scanning electron microscope equipped with an InLens detector and an SE2 detector. The images, approximately 35 μm × 27 μm in cross-sectional area, were produced at 10,000x magnification, a working distance of 3 mm to 4 mm, and an operating voltage of 2 kV. The line used in the measurements was 25 μm long in the SEM image and parallel to the surface of the substrate.

[0031] Thickness measurement

[0032] The coating thickness was measured on the fracture cross-section of the coated cutting tool. SEM images were generated using a Zeiss Ultra scanning electron microscope equipped with an InLens detector and an SE2 detector. The microscope was operated at 2 kV, a working distance of 3 mm to 4 mm, and a magnification of 10,000x, producing images of approximately 35 μm × 27 μm. The rake face of the coated cutting tool was studied.

[0033] Surface roughness measurement

[0034] The surface roughness value of the substrate surface on the rake face of the cutting tool is evaluated based on SEM images taken from the fracture cross-section. The method used here is as follows: Using a Zeiss Ultra scanning electron microscope equipped with an InLens detector and an SE2 detector, fracture cross-sections were acquired on the coated blade. At 10,000x magnification, a working distance of 3 mm to 4 mm, and an operating voltage of 2 kV, a cross-sectional image of approximately 35 μm × 27 μm at the interface between the substrate and coating was produced. After identifying the interface, the image was digitized using the Digitizer tool in Origin 2018b (b9.5.5.409) from OriginLab, and the Ra value was calculated as follows: Import the image using the Origin tool's Digitizer. Define the coordinate axes according to the scale in the image. Collect individual points at the interface between the substrate and coating at an average interval of approximately 0.5 μm (shorter intervals for curved features and longer intervals for straighter features) to generate a surface roughness profile. Fit a linear least squares line to the obtained profile. Subtract the obtained linear least squares line from the individual data points on the profile to ensure that possible image rotation does not affect the evaluation. Calculate the Ra value using the following formula:

[0035] Where n is the number of points used on the contour, and y i It is the distance between point i and the least squares line, in μm.

[0036] X-ray diffraction measurement

[0037] Texture coefficient values ​​TC(hkl) were measured on the rake face of a coated cutting tool using XRD utilizing Cu Kα radiation on a Bruker D8 Advance diffractometer (a Cu tube operated at 40 kV and 40 mA, equipped with a LynxEyeXE-T detector, and operated in θ-2θ mode). The diffractometer was equipped with fixed-beam optics: a 2.3° Soller slit and a 0.6 mm diverging slit on the primary side, an 8 mm anti-scattering slit on the secondary side, followed by a 2.5° Soller slit and a 0.5 mm Ni filter. During a total measurement time of approximately 5 minutes, diffraction patterns ranging from 18° to 143° were recorded in 2θ mode in steps of 0.05°. The coated cutting tool was mounted in a sample holder, ensuring that the sample surface being measured was parallel to the reference surface of the sample holder and also at the appropriate height.

[0038] Data analysis was performed using the Bruker TOPAS 5 program with the Le Bail method for full-pattern fitting. The output from this program (i.e., the integral peak area of ​​the profile fitting curve) was corrected as described below, and then the measured intensity data were compared with the reference intensity ratios of the TiCN and κ-Al2O3 layers using the Harris formula (F1) disclosed above to calculate the texture factor of each layer.

[0039] The measured intensities are corrected for thin films because, compared to a bulk sample, the relative intensities of the peaks scattered by each layer at different 2θ angles differ due to variations in path lengths across the layers. Therefore, when calculating the TC value, thin film correction is applied to the integral peak area intensity extracted from the profile fitting curve, taking into account the linear absorption coefficients of each layer. Since, for example, an additional layer above, such as the κ-Al₂O₃ layer, will affect the X-ray intensity entering the κ-Al₂O₃ layer and leaving the entire coating, these also need to be corrected for, taking into account the linear absorption coefficients of the corresponding compounds in the layer. The same applies to X-ray diffraction measurements of the TiCN layer if it is located below, for example, the κ-Al₂O₃ layer. Alternatively, another layer (e.g., TiN) located above the alumina layer can be removed by methods that substantially do not affect the XRD measurements (e.g., chemical etching).

[0040] To study the texture of the κ-Al2O3 layer, X-ray diffraction was performed using Cu Kα radiation, and the texture coefficient TC(hkl) for different growth directions of the κ-Al2O3 layer grains was calculated according to the Harris formula (F1) published above, where I(hkl) is equal to the measured integral area intensity of (hkl) reflection and has a corresponding reference intensity I0(hkl). In this case, the (hkl) reflections used and their corresponding reference intensities are: I0(1 1 1) = 105, I0(0 1 3) = 5026, I0(1 22) = 10000, I0(1 1 3) = 1116, I0(2 0 0) = 795, I0(2 0 1) = 1342, I0(0 0 4) = 291, I0(0 4 0) = 387, I0(0 1 5) = 429, and I0(2 0 4) = 1312. Before calculating the ratios, the measured integral peak area is corrected for the thin film, and any additional layers above (i.e., the layer on top of the κ-Al2O3 layer) are also corrected.

[0041] The texture coefficient TC(hkl) of the columnar grains in the TiCN layer is calculated according to the Harris formula (F1) disclosed above for different growth directions, where I(hkl) is equal to the measured integral area intensity of the (hkl) reflection and has a corresponding reference intensity. In this case, the (hkl) reflection used and its corresponding reference intensity are: I0(1 1 1) = 7871, I0(2 00) = 10000, I0(2 2 0) = 5369, I0(3 1 1) = 2550, I0(3 3 1) = 1128, I0(4 2 0) = 2366, I0(4 2 2) = 2479, and I0(5 1 1) = 1427. The reflections (5 1 1) and (3 3 3) completely overlap, therefore the intensity of the (5 1 1) peak is calculated from the sum of the intensities of (5 1 1) and (3 3 3), which is the measured intensity. This correction is performed as follows: I(5 1 1) is set to the sum of the integral peak areas of (5 1 1) and (3 3 3), and then the calculated value I of the (3 3 3) reflection is subtracted using the relationship between the reference intensities of the (1 1 1) and (3 3 3) reflections. c (3 3 3): I c (3 3 3) = I(1 11) I0(3 3 3) / I0(1 1 1). The value used for I0(3 3 3) is 476. Before calculating the ratio, the measured integral peak area is corrected for the thin film and for any other layers above it (e.g., κ-Al2O3 layers).

[0042] It should be noted that peak overlap is a phenomenon that can occur in the X-ray diffraction analysis of coatings comprising, for example, several crystalline layers and / or deposited on a substrate containing a crystalline phase. This must be considered and compensated for by those skilled in the art performing the analysis. Peak overlap between peaks from the κ-Al₂O₃ layer and peaks from the TiCN layer may affect the measurement and therefore 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 coating of the present invention.

[0043] Residual stress measurement

[0044] The residual stress of the κ-Al₂O₃ layer on the rake face of a CNMG12 cutting tool was evaluated using the sin²ψ method. The elastic constants used were Young's modulus 391 GPa and Poisson's ratio 0.24. The (1 2 2) lattice spacing of κ-Al₂O₃ was determined by X-ray diffraction (XRD). The positions of the (1 2 2) peaks were determined at angles (0° and 180°) and 6ψ angles (corresponding to sin²ψ values ​​of 0.225, 0.315, 0.405, 0.495, 0.585, and 0.675, respectively). Following the method proposed by Kumar, U. Welzel, and EJ Mittemeijer in the *Journal of Applied Crystallography* (2006, Vol. 39, pp. 633-646), the instrument angles were selected to maintain a constant penetration depth τ of 2 µm throughout the measurement process. A linear absorption coefficient of 12300 m was used when calculating the penetration depth in Al₂O₃. - ¹.

[0045] A coated cutting tool was mounted in the sample holder to ensure that the sample surface being measured was parallel to the reference surface of the sample holder and at the appropriate height. Measurements were performed using point-focused Cu Kα radiation on a Bruker D8 Discover instrument. On the primary side, the instrument is equipped with multi-capillary optics and a 2 mm pinhole. On the secondary side, an equatorial Soller slit was used with a Bruker LynxEye-XET detector operating in OD mode. Peak fitting was performed using Bruker Topas5 software and a pseudo-Voigt peak function, after which the lattice spacing d was calculated and the stress was evaluated. Attached Figure Description

[0046] Embodiments of the present invention will be described with reference to the accompanying drawings.

[0047] Figure 1 This is a SEM image of the fracture cross section of the coating in sample A (the present invention), showing the substrate (1), TiCN layer (2), κ-Al2O3 layer (3), and the outermost surface (4) of the κ-Al2O3 layer.

[0048] Figure 2 This is a SEM image of the fracture cross section of the coating in sample B (reference), showing the substrate (1), TiCN layer (2), κ-Al2O3 layer (3), and the outermost surface (4) of the κ-Al2O3 layer.

[0049] Figure 3 This is a schematic diagram of the cross-section of the coating of the present invention, which shows the widening of κ-Al2O3 grains (in the present invention), and shows the TiCN layer (2), the κ-Al2O3 layer (3) and the outermost surface (4) of the κ-Al2O3 layer.

[0050] Figure 4This is a schematic diagram of the cross-section of the reference coating, in which the κ-Al2O3 grains are columnar (reference), and the TiCN layer (2), the κ-Al2O3 layer (3), and the outermost surface (4) of the κ-Al2O3 layer are shown.

[0051] Figure 5 This is a SEM image of a cross-section of the reference coating, where the gray lines indicate the location of 80% of the thickness of the κ-Al2O3 layer, showing the substrate (1), the TiCN layer (2), the κ-Al2O3 layer (3), and the outermost surface (4) of the κ-Al2O3 layer.

[0052] Figure 6 This is a SEM image of the cross-section of the coating of the present invention, in which the gray line represents the position 1 μm away from the interface in the κ-Al2O3 layer, showing the substrate (1), TiCN layer (2), κ-Al2O3 layer (3) and the outermost surface (4) of the κ-Al2O3 layer.

[0053] Figure 7 This is a SEM image of the top surface of the κ-Al2O3 layer of sample A (the present invention), showing the outermost surface (4) of the κ-Al2O3 layer.

[0054] Figure 8 This is a SEM image of the top surface of the κ-Al2O3 layer of sample B (reference), showing the outermost surface of the κ-Al2O3 layer (4).

[0055] Figure 9 It is a SEM image of the fracture cross section of the coating in sample A (the present invention), which also includes a close-up area, in which the intercept method is illustrated by using gray lines to represent measurement lines and black lines to mark grain boundaries, showing the substrate (1), TiCN layer (2), κ-Al2O3 layer (3) and the outermost surface (4) of κ-Al2O3 layer. Detailed Implementation

[0056] Example

[0057] Embodiments of the invention will be disclosed in more detail with reference to the following examples. These examples are intended to be illustrative rather than limiting. In the following examples, coated cutting tools (inserts) are manufactured, analyzed, and evaluated in cutting tests. The cutting tools are prepared, wherein the cutting tools comprise a cemented carbide substrate (1) coated with a coating comprising a TiCN layer (2) and a κ-Al2O3 layer (3). The performance of these cutting tools is compared with that of a commercially available Seco milling grade MP1501, which has a TiCN layer and a 001-oriented α-Al2O3 layer.

[0058] base

[0059] The cemented carbide substrate for manufacturing ISO type XOMX120408TR is composed of 12.5 wt% Co, 0.7 wt% Cr, and the balance WC.

[0060] The powder mixture was ground, dried, pressed, and sintered at 1470 °C. The sintered cemented carbide substrate contained approximately 12.5% ​​by weight Co. No free graphite or η phase was observed in the SEM micrograph of the cross-section of the cemented carbide substrate.

[0061] Polishing the rake face

[0062] All samples were polished using a wet brush process. The equipment used was a Sinjet IBX12, which consisted of two operations. The first operation used a brush with flat SiC 240K bristles for coarse polishing and edge preparation. The second operation performed fine polishing using a brush composed of 1000K diamond bristles. Polishing was carried out until a surface roughness of 0.05 μm < Ra < 0.2 μm was achieved. After polishing, a cleaning operation using an ultrasonic bath and an alkaline solution was performed to remove any residue from the polishing process.

[0063] CVD deposition

[0064] The coating deposition in the following examples was performed in a radial Ionbond Bernex BPXpro 530 L tandem CVD system, which can accommodate 10,000 half-inch cutting blades. Samples for further testing and analysis were selected from the center of the chamber, located halfway along the plate's radius, between the plate's center and perimeter.

[0065] Before coating deposition, each substrate was cleaned in an ethanol bath for 30 minutes.

[0066] First, using the well-known MTCVD technique, a thin TiN layer of approximately 0.4 μm was coated onto the blade at 860 °C using TiCl4, CH3CN, N2, and H2, followed by a TiCN layer of approximately 2 μm. The TiCl4 / CH3CN volume ratio in the MTCVD deposition of the TiCN layer was 3.7. Details of the TiN and TiCN depositions are shown in Table 1.

[0067] Table 1. MTCVD of TiN and TiCN

[0068] A 2 μm thick binder layer was deposited on top of the MTCVD TiCN layer at 1020 °C via a process consisting of five independent reaction steps. The first step was HTCVD TiN-1 using TiCl4, N2, and H2 at a pressure of 200 mbar; the second step was HTCVD TiC-1 using TiCl4, CH4, and H2 at a pressure of 80 mbar; the third step was HTCVD TiN-2 using TiCl4, HCl, N2, and H2 at a pressure of 500 mbar; the fourth step was HT TiCN-1 using TiCl4, CH4, HCl, N2, and H2 at a pressure of 60 mbar; and finally, the fifth step was HT TiCNO-1 using TiCl4, HCl, CO, N2, and H2 at a pressure of 60 mbar. The binder layer was exposed to an H2 atmosphere of 45–55 mbar for 33 minutes before initiating subsequent κ-Al2O3 nucleation. Details of the adhesive layer deposition are shown in Table 2.

[0069] Table 2. Deposition of the binder layer

[0070] A κ-Al₂O₃ layer is deposited on top of the adhesive layer. The surface is first rinsed with AlCl₃ in the AlCl₃-1 step. On sample A of the present invention, the κ-Al₂O₃ layer deposition includes three different process steps (Al₂O₃-1, Al₂O₃-2, Al₂O₃-3), while on sample B, the κ-Al₂O₃ layer deposition includes only the first two process steps (Al₂O₃-1, Al₂O₃-2), as shown in Table 3. The first nucleation step (Al₂O₃-1) is performed identically on samples A and B, yielding approximately 0.05 μm of κ-Al₂O₃. On sample A of the present invention, the second step (Al₂O₃-2) yields approximately 2.5 μm of κ-Al₂O₃, and the third grain-broadening step (Al₂O₃-3) yields approximately 2 μm of κ-Al₂O₃. The total thickness of the κ-Al₂O₃ layer on sample A of the present invention is approximately 4.5 μm. On reference sample B, the second step yielded a κ-Al₂O₃ layer of approximately 4.0 μm. The total thickness of the κ-Al₂O₃ layer on reference sample B was approximately 4 μm.

[0071] Table 3. κ-Al2O3 deposition steps

[0072] shot peening

[0073] The coated cutting tool is then subjected to a shot peening process, in which the surface is bombarded with a medium containing particles (so-called beads), which are non-abrasive and have a rounded shape. The medium consists of beads made of a hard material primarily composed of ZrO2. The impact or energy from the beads during shot peening should not be too high, as this increases the risk of damaging the cutting tool's surface and cutting edge. The impact or energy from the beads should also not be too low, as the desired technical effect will not be achieved. If the beads are too large, the risk of damaging the cutting edge increases. If the beads are too small, the energy and impact transmitted from the medium to the substrate will be less.

[0074] Shot peening is a dry process, in which shot is introduced into the path of high-pressure air. Shot peening is performed using shot peening media beads with a diameter of 70-150 μm. The shot peening pressure is approximately 5 bar, and the distance between the shot peening nozzle and the surface of the cutting tool insert is approximately 10 cm. Shot peening is performed perpendicular to the surface of the cutting tool, and the peening duration for each insert is approximately 1 second.

[0075] wet sandblasting

[0076] Following dry blasting, the coated cutting tool undergoes a wet blasting process. In this process, abrasive particles are used to blast the cutting tool. Wet blasting is well-known in the cutting tool industry and, for example, is known to introduce residual stress into the coating of the cutting tool.

[0077] The wet blasting step uses a blasting medium containing Al2O3 particles with a diameter of 20-80 μm. Wet blasting is performed perpendicular to the surface of the cutting tool, with the distance between the blasting nozzle and the tool surface approximately 10-20 cm. The blasting pressure is approximately 1.4-1.8 bar, and the wet blasting duration for each insert is approximately 1 second.

[0078] Coating analysis

[0079] The cross-sections of samples A and B on the rake face were studied using SEM. The layer thicknesses are shown in Table 4.

[0080] Table 4. Layer thickness in the samples

[0081] Roughness of the substrate on the rake face

[0082] The roughness of the substrate at the rake face was measured, and the average Ra value of both samples was approximately 0.18 μm.

[0083] Grain broadening

[0084] The grain width in the κ-Al2O3 layer was investigated using cross-sectional SEM images of the coating on the rake face. At a distance of 1 μm from the binder layer (d... a The average width of the κ-Al2O3 grains was studied at 80% of the total thickness of the κ-Al2O3 layer (db) (approximately 3.6 μm from the binder layer in this example). The average values ​​of the four parallel measurements are shown in Table 5.

[0085] Table 5. Grain width in the κ-Al2O3 layer

[0086] Texture coefficient

[0087] Texture coefficients were analyzed using the method described above via X-ray diffraction. All calculated TC values ​​are shown in Tables 6 and 7.

[0088] Table 6. Texture coefficients of the TiCN layers in Invention A and Reference B.

[0089]

[0090] Table 7. Texture coefficients of the κ-Al2O3 layers in Invention A and Reference B.

[0091]

[0092] Performance Testing - Sandblasting Test

[0093] The cutting tools were evaluated after wet blasting and the degree of wear caused by blasting was studied.

[0094] Samples A and B underwent a mild wet blasting process (blasting G), using Al2O3 particles with a diameter of 20-80 μm mixed with water as the blasting medium. Blasting was performed at a distance of 20 cm, with each blade's wet blasting duration being 1 second, and the blasting pressure being approximately 1.4 bar. The samples treated with this mild blasting were subsequently designated as sample AG and sample BG.

[0095] Samples A and B underwent intense wet blasting (blasting S) using Al₂O₃ particles with a diameter of 20-80 μm mixed with water as the blasting medium. Blasting was performed at a distance of 10 cm, with each blade blasting lasting 1 second, and a blasting pressure of approximately 1.8 bar. The samples subjected to this intense blasting treatment were subsequently designated as Sample AS and Sample BS.

[0096] The cutting tool after sandblasting was examined under an optical microscope. On the heavily sandblasted reference sample (sample BS), the oxide layer was removed, and the coating was damaged at the cutting edge. The heavily sandblasted sample of the present invention (sample AS) still showed an oxide layer at the cutting edge. The results of the visual inspection are shown in Table 8.

[0097] Table 8. Sandblasting evaluation

[0098] Sample A does indeed resist more intense wet blasting processes without removing the oxide layer from the cutting edge. Therefore, Sample A can be treated to achieve higher compressive residual stress, which is beneficial for improving wear resistance in metal cutting applications.

[0099] Residual stress

[0100] The residual stress in the κ-Al2O3 layer of samples A and B was measured using the method described above. The stress state was assessed before post-treatment of samples A and B (in the deposited state) and after post-treatment of samples AS and BG (after shot peening and wet blasting), as shown in Table 9. Sample AS exhibited significant compressive stress in the κ-Al2O3 layer after the post-treatment operation.

[0101] Table 9. Residual stress state measured in the κ-Al2O3 layer of the samples before and after post-treatment.

[0102] Performance Testing - Cutting Test

[0103] Coated cutting tools of ISO type XOMX120408TR (samples AS and BG) were subjected to shot peening and wet sandblasting, and evaluated in cutting tests. Reference sample BG underwent wet sandblasting using the aforementioned sandblasting G, while sample AS of this invention underwent wet sandblasting using sandblasting S.

[0104] In this cutting test, a reference sample—Sample C—was also included in the evaluation. Sample C is a commercially available Seco milling machine, grade MP2501, ISO type XOMX120408TR. Details of Sample C are as follows: The substrate composition of sample C is the same as that of samples A and B disclosed above. The substrate roughness at the rake face was measured, and the average value of Ra was approximately 0.18 μm.

[0105] The coating of sample C consists of the following layers (listed from the substrate): a 0.4 μm TiN layer, a 4 μm TiCN layer, a 0.6 μm AlTiCNO binder layer, a 3.5 μm α-Al₂O₃ layer, and a 0.05 μm outermost Cr color layer. Therefore, the total coating thickness is 8.55 μm.

[0106] The texture indices of the TiCN layer in sample C are: TC(1 1 1)=0.05, TC(2 0 0)=0.04, TC(2 2 0)=1.18, TC(3 1 1)=2.02, TC(3 3 1)=1.30, TC(4 2 0)=0.48, TC(4 2 2)=2.70, and TC(5 11)=0.22, measured by X-ray diffraction as disclosed above.

[0107] Using Cu Kα radiation and θ-2θ scanning X-ray diffraction measurements, the texture coefficients of the α-Al₂O₃ layer of sample C, defined by Harris formula (F₁), are: TC(1 0 4) = 0.02, TC(1 1 0) = 0.01, TC(1 1 3) = 0.00, TC(0 2 4) = 0.01, TC(1 1 6) = 0.03, TC(0 1 8) = 0.28, TC(0 3 0) = 0.01, TC(0 2 10) = 0.33, TC(0 0 12) = 7.77, TC(0 1 14) = 1.53, and TC(0 0 12) + TC(0 1 14) = 9.3, where I(hkl) is the measured integral area intensity of (hkl) reflection, and I₀(hkl) is the standard intensity, where I₀ (1 0 4)=9681, I0 (1 1 0)=4562, I0(1 1 3)=9742, I0 (0 2 4)=5055, I0 (1 1 6)=10000, I0 (0 1 8)=761, I0 (0 3 0)=6168, I0(0 2 10)=852, I0 (0 0 12)=204, I0 (0 1 14)=598, n is the number of reflections used in the calculation, where the (hkl) reflections used are those listed.

[0108] The residual stress in the α-Al2O3 layer of sample C, measured using peak (116) in the manner described above, is -0.92 GPa.

[0109] Using the following cutting data, coated cutting tools AS, BG, and C were tested in a linear side radial milling operation in M2 stainless steel (SS2333). End mill: R220.69-0063-12-6AN Cutting speed v c 100m / minute Cutting feed fz: 0.2mm / tooth Cutting depth a p 3mm radial cutting depth ae 12.6mm Length of each pass: 300mm Workpiece overhang length: 200mm Life standard: Rake face wear >0.3mm Machining was performed using a 6% coolant emulsion at a pressure of 40 bar. Three cutting edges were evaluated for each cutting tool. All cutting edges in all variations operated in the same manner and stopped when flank wear reached 0.3 µm (visible wear relative to the coating on the clearance surface in the insert tip section below the workpiece material contact area) was observed using an optical microscope. The results are shown in Table 10.

[0110] Table 10. Cutting Test Results

[0111] As shown in Table 10, the present invention sample AS exhibits an extended lifetime compared to reference samples BG and C.

[0112] While the invention has been described in conjunction with various exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments; rather, the invention is intended to cover various modifications and equivalent arrangements within the scope of the appended claims.

Claims

1. A cutting tool comprising a substrate (1) at least partially coated with a coating, the substrate (1) being made of cemented carbide or cermet, the coating comprising one or more layers, wherein, At least one layer is a κ-Al2O3 layer (3) with a thickness of 3-6 μm, wherein the κ-Al2O3 layer (3) is composed of grains, and wherein the grain width is the width of the grain in a direction parallel to the surface of the substrate (1), and wherein the average grain width d of the κ-Al2O3 grains is... b It is measured along a line corresponding to 80% of the thickness of the κ-Al2O3 layer (3), and the average grain width d of the κ-Al2O3 grains is... a It is measured along a line 1 μm away from the innermost κ-Al2O3 interface, characterized by the ratio d b / d a Between 1.45 and 2.

00.

2. The cutting tool according to claim 1, wherein, The ratio d b / d a Between 1.48 and 1.

80.

3. The cutting tool according to any one of the preceding claims, wherein, The residual stress in the κ-Al2O3 layer, as measured by XRD, is between -0.6 GPa and -2.0 GPa.

4. The cutting tool according to any one of the preceding claims, wherein, The average grain width d of the κ-Al2O3 grains, measured along a line corresponding to 80% of the thickness of the κ-Al2O3 layer (3). b Between 0.6μm and 0.8μm.

5. The cutting tool according to any one of the preceding claims, wherein, The thickness of the κ-Al2O3 layer (3) is between 4 μm and 5 μm.

6. The cutting tool according to any one of the preceding claims, wherein, The coating includes a TiCN layer (2) located between the substrate (1) and the κ-Al2O3 layer (3).

7. The cutting tool according to claim 6, wherein, The thickness of the TiCN layer (2) is between 1.5 μm and 2.5 μm.

8. The cutting tool according to any one of the preceding claims, wherein, The coating includes the innermost TiN layer.

9. The cutting tool according to claim 8, wherein, The thickness of the innermost TiN layer is between 0.3 μm and 0.6 μm.

10. The cutting tool according to any one of claims 6-7, wherein, The coating includes an adhesive layer located between the TiCN layer (2) and the κ-Al2O3 layer (3), preferably, the adhesive layer is one or more of TiCO, TiCNO, AlTiCO or AlTiCNO.

11. The cutting tool according to claim 10, wherein, The thickness of the adhesive layer is between 1.5 μm and 2.5 μm.

12. The cutting tool according to any one of the preceding claims, wherein, Measured in a SEM cross section, the surface roughness Ra of the substrate (1) at the rake face is between 0.05µm and 0.2µm, preferably between 0.15µm and 0.2µm.

13. The cutting tool according to any one of the preceding claims, wherein, The κ-Al2O3 layer (3) exhibits a texture coefficient TC(hkl), which is measured by X-ray diffraction using Cu Kα radiation and θ-2θ scanning, and is defined according to the Harris formula: Where I(hkl) is the measured intensity (integral area) of the (hkl) reflection, I0(hkl) is the standard intensity, where I0(1 1 1) = 105, I0(0 1 3) = 5026, I0(1 2 2) = 10000, I0(1 1 3) = 1116, I0(2 0 0) = 795, I0(20 1) = 1342, I0(0 0 4) = 291, I0(0 4 0) = 387, I0(0 1 5) = 429 and I0(2 0 4) = 1312, n is the number of reflections used in the calculation, where the (hkl) reflections used are (1 1 1), (0 1 3), (1 2 2), (1 1 3), (2 0 1 ... 0), (2 0 1), (0 0 4), (0 4 0), (0 1 5) and (2 0 4), wherein TC(00 4) + TC(0 1 5) ≥ 6, preferably ≥ 7, more preferably ≥ 8.

14. The cutting tool according to any one of claims 6 to 13, wherein, The TiCN layer (2) exhibits a texture factor TC(hkl), which is measured by X-ray diffraction using Cu Kα radiation and θ-2θ scanning, and defined according to Harris formula (F1), where I(hkl) is the measured intensity (integral area) of the (hkl) reflection, I0(hkl) is the standard intensity, where I0(1 1 1) = 7871, I0(2 0 0) = 10000, I0(2 2 0) = 5369, I0(3 1 1) = 2550, I0(3 3 1) = 1128, I0(4 2 0) = 2366, I0(4 2 2) = 2479, and I0(5 1 1) = 1427, n is the number of reflections used in the calculation, and where the (hkl) reflection used is (1 1 1), (2 0 0), (22 0), (3 1 1), (3 3 1), (4 2 0), (4 2 2), (5 1 1), where TC(4 2 2)≥3, preferably ≥4, more preferably ≥5.

Images