cutting tool

Abstract

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

Description

Technology Field

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

[0002] In the technical field of cutting tools for metal machining, the use of CVD coatings is a well-known method for improving the wear resistance of tools. Commonly used CVD coatings include TiN, TiC, TiCN, and Al2O3.

[0003] The wear resistance of Al2O3 coatings is influenced by their crystal structure, and the most commonly used are κ- and α-Al2O3 coatings. Wear characteristics in machining operations typically differ between α-Al2O3 coatings and κ-Al2O3 coatings, and therefore their respective applications may also differ.

[0004] EP0753602 A1 discloses a cutting tool that results in a {210} texture, including a κ-Al2O3 coating having a crystal growth orientation, and said tool exhibits improved wear characteristics in machining ball bearing steel. The problem to be solved

[0005] The object of the present invention is to provide a cutting tool with increased lifespan in metal cutting. Additionally, the object of the present invention is to provide a cutting tool having high resistance to flank wear and chipping during the cutting of steel. means of solving the problem

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

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

[0008] In one embodiment of the present invention, the ratio d b / d a It is between 1.48 and 1.80.

[0009] A strong wet blasting process can be applied to the coating of the present invention, and as a result, the application fields of the κ-Al2O3 coating are expanded.

[0010] It was surprisingly found that a cutting tool provided with a coating comprising a κ-Al2O3 layer having grains satisfying the above-mentioned ratio exhibits increased resistance to blasting and increased resistance to flank wear in the milling of stainless steel.

[0011] A κ-Al2O3 layer thinner than 3 μm is disadvantageous because it limits wear resistance, and a κ-Al2O3 layer thicker than 6 μm is disadvantageous because it widens the cutting edge radius of the cutting tool.

[0012] In one embodiment, the substrate of the coated cutting tool is composed of a cemented carbide comprising 7 to 14 weight% Co, for example 11 to 13 weight% Co, and 0.5 to 0.8 weight% Cr, with the remainder being WC.

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

[0014] The above cutting tool includes an inclined surface, a clearance surface, and a cutting edge between them.

[0015] In one embodiment of the present 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 present invention, the average grain width d of κ-Al2O3 grains measured along a line extending parallel to the substrate surface and located at a position corresponding to 80% of the thickness of the κ-Al2O3 layer b The thickness is between 0.6 μm and 0.8 μm, preferably between 0.65 μm and 0.70 μm. In this specification, the position corresponding to 80% of the thickness of the κ-Al2O3 layer refers to the position when viewed from the surface of the substrate toward the outer surface of the coating, that is, from the growth direction of the κ-Al2O3 layer. The position 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 present invention, the average grain width d of κ-Al2O3 grains measured along a line extending parallel to the substrate surface and at a distance of 1 μm from the innermost κ-Al2O3 interface aThe range 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 lowest interface of the κ-Al2O3 layer and is typically the interface with the bonding 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 comprises a TiCN layer between the substrate and the κ-Al2O3 layer, and 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 comprises an innermost TiN layer, and preferably, the thickness of the innermost TiN layer is between 0.3 μm and 0.6 μm.

[0021] In one embodiment of the present invention, the coating comprises a bonding layer between the TiCN layer and the κ-Al2O3 layer, preferably the bonding layer is one or more of TiCO, TiCNO, AlTiCO and AlTiCNO, and more preferably the thickness of the bonding layer is between 1.5 μm and 2.5 μm.

[0022] In one embodiment of the present invention, the surface roughness R of the substrate on an inclined surface measured in an SEM cross-section is a is between 0.05 μm and 0.2 μm, preferably between 0.15 μm and 0.2 μm. R within the range between 0.05 μm and 0.2 μm. a It was found to be advantageous for providing wear-resistant coated cutting tools.

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

[0024] (F1)

[0025] Here, I(hkl) is the measured integrated area intensity of the (hkl) reflection, I0(hkl) is the standard intensity, 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(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, n is the number of reflections used in the calculation, and the (hkl) reflections used are (1 1 1), (0 1 3), (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), and TC(0 0 4) + TC(0 1 5) ≥ 6, preferably ≥ 7, more preferably ≥ 8.

[0026] In one embodiment of the present invention, the TiCN layer is measured by X-ray diffraction using Cu Kα radiation and θ-2θ scan and exhibits a texture coefficient TC(hkl) defined according to the Harris equation (F1), where I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, and I0(hkl) is the standard intensity, with 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, where n is the number of reflections used in the calculation, and 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 1 1), and TC(4 2 2) ≥ 3, preferably ≥ 4, more preferably ≥ 5.

[0027] In one embodiment of the present invention, the cutting tool comprises an innermost TiN layer of 0.3 to 0.5 μm, a TiCN layer of 1.5 to 2.5 μm, an AlTiCNO bonding layer of 1.5 to 2.5 μm, and a κ-Al2O3 layer of 3 to 6 μm.

[0028] Further objects and features of the present invention will become clear from the following definitions and embodiments considered together with the accompanying drawings.

[0029] method

[0030] Grain width measurement

[0031] The average grain width of the κ-Al2O3 grains is 80% of the layer thickness, i.e., at a position 20% from the top surface of the layer (d b ) and a position 1 μm above the lower interface (d a It was determined in ). A grain section method was used to determine the average grain width from the measured grain widths along a line of length 25 μm on the SEM image. Using a Zeiss Ultra scanning electron microscope equipped with InLens and an SE2 detector, fracture cross-section images of the coated insert on an inclined plane were collected at 10,000x magnification at an operating distance of 2 kV and between 3 mm and 4 mm, generating an image of approximately 35 μm × 27 μm of the coating cross-section. The line used for measurement was 25 μm in length in the SEM image and was parallel to the substrate surface.

[0032] Thickness measurement

[0033] The coating layer thickness was measured at the fracture cross-section of the coated insert. SEM images were generated using a Zeiss Ultra scanning electron microscope equipped with InLens and an SE2 detector. The microscope was operated at 2 kV, an operating distance between 3 mm and 4 mm, and a magnification of 10,000x to produce an image of approximately 35 µm × 27 µm. The rake face of the coated cutting tool was observed.

[0034] Surface roughness measurement

[0035] The surface roughness value of the substrate surface on the rake face of the cutting tool was evaluated from SEM images taken from the fracture cross-section. The method used here was performed as follows.

[0036] Using a Zeiss Ultra scanning electron microscope equipped with InLens and an SE2 detector, fracture cross-sections of the coated inserts were collected at 10,000x magnification at an operating distance of 2 kV and between 3 mm and 4 mm, and images of approximately 35 µm × 27 µm were generated for the cross-sectional interface between the substrate and the coating. After verifying the interface, the images were digitized using the Digitizer tool included in OriginLab's Origin 2018b (b9.5.5.409), and R a The value was calculated as follows.

[0037] Images were imported using Digitizer, an Origin tool. Axes were defined based on the image scale. Individual points on the interface between the substrate and the coating were collected at an average interval of approximately 0.5 μm; surface roughness profiles were generated using shorter intervals for curved features and longer intervals for linear features. Linear least squares lines were fitted to the obtained profiles. The obtained linear least squares lines were subtracted from the individual data points on the profiles to ensure that possible image rotation did not affect the evaluation. R a The value was calculated using the following formula:

[0038]

[0039] Here, n is the number of points used in the profile, and yi is the distance (μm) between point i and the least squares line.

[0040] X-ray diffraction measurement

[0041] The texture coefficient value TC(hkl) was measured by XRD using CuKα radiation on the inclined surface of the coated cutting tool using a Bruker D8 Advance diffractometer equipped with a LynxEye XE-T detector operating in θ-2θ mode and driving a Cu tube at 40 kV and 40 mA. The diffractometer was equipped with a fixed-beam optical system, featuring a 2.3° Soller slit and a 0.6 mm diverging slit on the primary side, and an 8 mm anti-scattering slit followed by a 2.5° Soller slit and a 0.5 mm Ni filter on the secondary side. Diffraction patterns were recorded at 0.05° intervals in the range of 18° to 143° at 2θ for a total measurement time of approximately 5 minutes. The coated cutting tool was mounted in a sample holder such that the sample surface being measured was parallel to the reference surface of the sample holder and positioned at an appropriate height.

[0042] Data analysis was performed using the Bruker TOPAS 5 program with full pattern fitting by the Le Bail method. The output from this program, i.e., the integrated peak area of ​​the profile fitting curve, was used to calculate the texture coefficient of each layer by comparing the ratio of the measured intensity data to the reference intensity for the TiCN and κ-Al2O3 layers using the Harris equation (F1) described above, after correction as described below.

[0043] The measured intensity was thin-film corrected because the relative intensity of the peaks scattered by the layer at different 2θ angles differs from that of the bulk sample due to differences in path lengths passing through the layer. Therefore, when calculating the TC value, thin-film correction was applied to the integrated peak area intensity extracted from the profile fitting curve, taking into account the linear absorption coefficients of the layer(s). For example, additional layers that may be located above the κ-Al2O3 layer affect the X-ray intensity entering the κ-Al2O3 layer and the X-ray intensity exiting the entire coating; thus, correction for these additional layers must also be performed by considering the linear absorption coefficients for each compound within the layer. The same applies to the X-ray diffraction measurements of the TiCN layer when, for example, a TiCN layer is located below the κ-Al2O3 layer. Alternatively, additional layers such as TiN above the alumina layer can be removed by methods that do not substantially affect the XRD measurement results, such as chemical etching.

[0044] To investigate the texture of the κ-Al2O3 layer, X-ray diffraction was performed using CuKα radiation, and the texture coefficient TC(hkl) for different growth directions of the crystal grains of the κ-Al2O3 layer was calculated according to the Harris equation (F1) described above, where I(hkl) is equal to the measured integrated area intensity of the (hkl) reflection having the corresponding reference intensity I0(hkl). In this case, the (hkl) reflections and their corresponding reference intensities used are as follows: 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(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. The measured integrated peak area is corrected for the thin film before calculating the above ratio, and corrected for any additional layer above the κ-Al2O3 layer, i.e., on top.

[0045] The texture coefficient TC(hkl) for different growth directions of columnar grains in the TiCN layer was calculated according to the Harris equation (F1) described above, where I(hkl) is equal to the measured integrated area intensity of the (hkl) reflection having the corresponding reference intensity I0(hkl). In this case, the (hkl) reflections and their corresponding reference intensities used are as follows: 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. Since the reflections (5 1 1) and (3 3 3) completely overlap, the intensity of the (5 1 1) peak was calculated from the sum of the intensities of the measured values ​​(5 1 1) and (3 3 3). This correction was performed as follows. I(5 1 1) was set as the sum of the integrated peak areas for (5 1 1) and (3 3 3), and then the (3 3 3) reflection value Ic(3 3 3) calculated using the reference intensity relationship of the (1 1 1) and (3 3 3) reflections was subtracted: Ic(3 3 3) = I(1 1 1) Х I0(3 3 3) / I0(1 1 1). The value used for I0(3 3 3) is 476. The measured integrated peak area is corrected for the thin film before calculating the above ratio, and corrected for any additional layer on top, such as a κ-Al2O3 layer, for example.

[0046] It should be noted that peak overlap is a phenomenon that may occur, for example, in X-ray diffraction analysis of a coating comprising multiple crystalline layers and / or a coating deposited on a substrate comprising a crystalline phase, and that this must be taken into account and compensated for by a person skilled in the art performing the analysis. Peak overlap between the peaks of the κ-Al2O3 layer and the TiCN layer needs to be taken into account as it may affect the measurement. Additionally, it should be noted that, for example, WC within the substrate may have diffraction peaks close to the relevant peaks of the coating.

[0047] Residual stress measurement

[0048] The residual stress of the κ-Al2O3 layer was evaluated on the inclined plane of the CNMG12 insert by the sin² method using elastic constants of 391 GPa and 0.24 for the Young's modulus and Poisson ratio, respectively, and the κ-Al2O3 (1 2 2) lattice spacing determined by X-ray diffraction (XRD). (1 2 2) Peak positions were determined at two φ 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). The instrument angle was selected according to the method described in Kumar, U. Welzel, EJ Mittemeijer, J. Appl. Cryst. (2006) 39, 633-646, so that the penetration depth τ was kept constant at 2 μm throughout the measurement. 12,300 m when calculating the penetration depth in Al2O3 -1 The linear absorption coefficient of was used.

[0049] The coated cutting tool was mounted in the sample holder so that the surface of the sample to be measured was parallel to the reference surface of the sample holder and positioned at an appropriate height. Measurements were performed on a Bruker D8 Discover instrument using point-focused Cu Kα radiation. A polycapillary optical system and a 2 mm pinhole were installed on the primary side. On the secondary side, an equatorial Soller slit was used in conjunction with a Bruker LynxEye-XET detector operating in 0D mode. Peak fitting was performed using Bruker Topas5 software and the Pseudo-Voigt peak function, after which the grid spacing d was calculated and the stress evaluated. Brief explanation of the drawing

[0050] Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an SEM image of the fracture cross-section of a coating in sample A (inventive example), wherein the substrate (1), TiCN layer (2), κ-Al2O3 layer (3) and the outermost surface (4) of the κ-Al2O3 layer are shown. FIG. 2 is an SEM image of the fracture cross-section of the coating in sample B (comparative example), where the substrate (1), TiCN layer (2), κ-Al2O3 layer (3) and the outermost surface (4) of the κ-Al2O3 layer are shown. FIG. 3 is a schematic cross-sectional view of an inventive coating showing the width expansion of κ-Al2O3 crystal grains, where the TiCN layer (2), the κ-Al2O3 layer (3), and the outermost surface (4) of the κ-Al2O3 layer are shown. FIG. 4 is a schematic cross-sectional view of a comparative example coating in which κ-Al2O3 crystal grains are the main phase, wherein the TiCN layer (2), the κ-Al2O3 layer (3), and the outermost surface (4) of the κ-Al2O3 layer are shown. FIG. 5 is a cross-sectional SEM image of a comparative example coating where the gray line indicates the 80% position of the κ-Al2O3 layer thickness, where the substrate (1), TiCN layer (2), κ-Al2O3 layer (3), and the outermost surface (4) of the κ-Al2O3 layer are shown. FIG. 6 is a cross-sectional SEM image of an inventive example coating where the gray line indicates a position of 1 μm from the interface within the κ-Al2O3 layer, where the substrate (1), TiCN layer (2), κ-Al2O3 layer (3), and the outermost surface (4) of the κ-Al2O3 layer are shown. FIG. 7 is an SEM image of the upper surface of the κ-Al2O3 layer of sample A (inventive example), where the outermost surface (4) of the κ-Al2O3 layer is shown. FIG. 8 is an SEM image of the upper surface of the κ-Al2O3 layer of sample B (comparative example), where the outermost surface (4) of the κ-Al2O3 layer is shown. FIG. 9 is a fracture cross-section SEM image of a coating in Sample A (Inventive Example) including an enlarged area illustrating the sectioning method by grain boundaries indicated by gray and black lines, wherein the substrate (1), TiCN layer (2), κ-Al2O3 layer (3) and the outermost surface (4) of the κ-Al2O3 layer are shown. Specific details for implementing the invention

[0051] Embodiments of the present invention will be disclosed in more detail in connection with the following examples. The examples should be considered exemplary and not limiting. In the following examples, coated cutting tools (inserts) were manufactured, analyzed, and evaluated in cutting tests. The cutting tools were prepared to include a cemented carbide substrate (1), said substrate was coated with a coating comprising a TiCN layer (2) and a κ-Al2O3 layer (3). Their performance was compared with that of a commercially available Seco milling grade MP1501 provided with a TiCN layer and an 001 oriented α-Al2O3 layer.

[0052] write

[0053] A cemented carbide substrate of ISO type XOMX120408TR was manufactured, and the composition was 12.5 wt% Co, 0.7 wt% Cr, and the remainder WC.

[0054] The powder mixture was milled, dried, and pressed, then sintered at 1470°C. The sintered cemented carbide substrate contained approximately 12.5 wt% Co. No free graphite or eta phase was observed in the cross-sectional SEM micrograph of the cemented carbide substrate.

[0055] Grinding of the inclined surface

[0056] All samples were polished on the bevels using a wet brushing process. The equipment used was a Sinjet IBX12 model, employing a setup consisting of two tasks; the first task performed rough polishing and edge preparation using a brush with flat SiC 240K grain size bristles. The second task performed fine polishing, utilizing a brush composed of Diamond 1000K bristles. Polishing was performed to achieve a surface roughness of 0.05 µm < R a This was performed until < 0.2 μm was obtained. After polishing, a cleaning operation using an ultrasonic bath and an alkaline solution was performed to remove any residue from the polishing process.

[0057] CVD deposition

[0058] The coatings in the following examples were deposited in a radial Ionbond Bernex Model BPXpro 530 L tandem CVD machine capable of accommodating 10,000 half-inch cutting inserts. Samples to be further tested and analyzed were selected at a location corresponding to the middle of the chamber and a half-radius between the center and the periphery of the plate.

[0059] Before coating deposition, all substrates were cleaned in an ethanol bath for 30 minutes.

[0060] A thin TiN layer of about 0.4 μm was first coated on the insert, and then a TiCN layer of about 2 μm was coated by applying the well-known MTCVD technique using TiCl4, CH3CN, N2, and H2 at 860°C. The volume ratio of TiCl4 / CH3CN in the MTCVD deposition of the TiCN layer was 3.7. Details of the TiN and TiCN deposition are shown in Table 1.

[0061]

[0062] A bonding layer with a thickness of 2 μm was deposited on an MTCVD TiCN layer by a process consisting of five distinct reaction steps at 1020°C. First, an HTCVD TiN-1 step was performed using TiCl4, N2, and H2 at 200 mbar, followed by a second step (HTCVD TiC-1) using TiCl4, CH4, and H2 at 80 mbar, a third step (HTCVD TiN-2) using TiCl4, HCl, N2, and H2 at 500 mbar, a fourth step (HT TiCN-1) using TiCl4, CH4, HCl, N2, and H2 at 60 mbar, and finally, a fifth step (HT TiCNO-1) using TiCl4, HCl, CO, N2, and H2 at 60 mbar. Before subsequent κ-Al2O3 nucleation began, the bonding layer was exposed to an H2 atmosphere at 45 to 55 mbar for 33 minutes. Details of the bonding layer deposition are shown in Table 2.

[0063]

[0064] The κ-Al2O3 layer was deposited on the bonding layer, and first, AlCl3 was flushed onto the surface in the AlCl3-1 step. In Inventive Example Sample A, the deposition of the κ-Al2O3 layer involved three different process steps (Al2O3-1, Al2O3-2, Al2O3-3), while in Sample B, the deposition of the κ-Al2O3 layer involved only the first two process steps (Al2O3-1, Al2O3-2) (see Table 3). The first nucleation step (Al2O3-1) was performed identically in both Sample A and Sample B, producing κ-Al2O3 of approximately 0.05 μm. In Inventive Example Sample A, the second step (Al2O3-2) produced κ-Al2O3 of approximately 2.5 μm, and the third grain width expansion step (Al2O3-3) produced approximately 2 μm. In Inventive Example Sample A, the total thickness of the κ-Al2O3 layer was approximately 4.5 μm. In Comparative Example Sample B, the second step produced κ-Al2O3 of approximately 4.0 μm. In Comparative Example Sample B, the total thickness of the κ-Al2O3 layer was approximately 4 μm.

[0065]

[0066] Short pinning

[0067] Subsequently, the coated cutting tool was subjected to a shot peening process in which its surface was impacted by a medium containing particles, so-called beads, which were non-abrasive and rounded beads. The medium consisted mainly of beads of a hard material containing ZrO2. During shot peening, the impact or energy from the beads must not be too high, as this increases the risk of damaging the surface and cutting edge of the cutting tool. Furthermore, if the impact or energy from the beads is too low, it is undesirable as the desired technical effect is not 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 transferred from the medium to the substrate are less significant.

[0068] Shot peening was a dry process in which a bead was introduced into the path of high-pressure air. Shot peening was performed with peening medium beads having a diameter of 70 to 150 μm. The peening pressure was approximately 5 bar, and the distance between the gun nozzle and the surface of the cutting tool insert was approximately 10 cm. Shot peening was performed perpendicular to the surface of the cutting tool, and the duration per insert was approximately 1 second.

[0069] Wet blasting

[0070] After dry blasting, the coated cutting tool was subjected to a wet blasting process. In this process, the cutting tool was subjected to blasting using abrasive particles. Wet blasting is well known in the field of cutting tools and is known, for example, to introduce residual stress into the coating of the cutting tool.

[0071] The wet blasting step was performed with a blasting medium containing Al2O3 particles with a diameter of 20 to 80 μm. Wet blasting was performed perpendicular to the surface of the cutting tool, at a distance of about 10 to 20 cm between the gun nozzle and the surface of the cutting tool. The blasting pressure was about 1.4 to 1.8 bar, and the duration per insert was about 1 second.

[0072] Coating analysis

[0073] Samples A and B were observed by SEM in cross-sections on inclined planes. The layer thicknesses are shown in Table 4.

[0074]

[0075] Material roughness on an inclined surface

[0076] The roughness of the material was measured on an inclined surface, and R a The average value of was about 0.18 μm in both samples.

[0077] Grain width expansion

[0078] The grain width within the κ-Al2O3 layer was observed in the SEM image of the coating cross-section on the inclined plane. The average width of the κ-Al2O3 grains was at a position 1 μm from the bonding layer (d a ) and at the 80% position of the total κ-Al2O3 layer thickness (d b In this case, all measurements were taken at a position approximately 3.6 μm from the bonding layer. The average of the four parallel measurements is shown in Table 5.

[0079]

[0080] Collective Organization Count

[0081] The texture coefficient was analyzed by X-ray diffraction according to the method described above. All calculated TC values ​​are shown in Tables 6 and 7.

[0082]

[0083]

[0084] Performance Test - Blasting Test

[0085] The cutting tool was evaluated after wet blasting post-treatment, and the degree of wear from the blasting was investigated.

[0086] Samples A and B were subjected to a gentle wet blasting process, namely blasting G, using a blasting medium of Al2O3 particles with a diameter of 20 to 80 μm mixed with water. Blasting was performed at a distance of 20 cm, for 1 second per insert, and at a blasting pressure of approximately 1.4 bar. The samples treated with this gentle blasting were subsequently referred to as Sample AG and Sample BG.

[0087] Samples A and B were subjected to a strong wet blasting process, namely blasting S, using a blasting medium of Al2O3 particles with a diameter of 20 to 80 μm mixed with water. Blasting was performed at a distance of 10 cm, for 1 second per insert, and at a blasting pressure of approximately 1.8 bar. The samples treated with this strong blasting were subsequently referred to as Sample AS and Sample BS.

[0088] The blasted cutting tools were inspected with an optical microscope. In Sample BS, a comparative example sample that was heavily blasted, the oxide layer was removed and the coating was destroyed at the edge. In Sample AS, an inventive example sample that was heavily blasted, the oxide layer was still present at the edge. The results of the visual inspection are shown in Table 8.

[0089]

[0090] Sample A resisted a stronger wet blasting process with oxides not removed from the cutting edge. Therefore, Sample A can be processed to achieve higher compressive residual stress, which is advantageous for higher wear resistance in metal cutting applications.

[0091] residual stress

[0092] The residual stress of the κ-Al2O3 layer was measured for samples A and B using the method described above. The stress state was evaluated for samples A and B before post-treatment (deposited state) and for samples AS and BG after post-treatment (shot peening and wet blasting) (see Table 9). Sample AS exhibited significant compressive stress in the κ-Al2O3 layer after the post-treatment operation.

[0093]

[0094] Performance Test - Cutting Test

[0095] Sample AS and Sample BG, which are coated cutting tools of ISO type XOMX120408TR, were shot peening and wet blasting treatments and evaluated in cutting tests. Comparative Example Sample BG was wet blasted using the aforementioned blasting G, and Inventive Example Sample AS was wet blasted with blasting S.

[0096] In this cutting test, Sample C, a comparative example sample, was also included in the evaluation. Sample C is a commercially available Seco milling grade MP2501, ISO type XOMX120408TR. Details of Sample C are presented below.

[0097] The substrate composition of Sample C is identical to Samples A and B disclosed above. The roughness of the substrate on an inclined surface was measured, and R a The average value was approximately 0.18 μm.

[0098] The coating of sample C comprises the following layers starting from the substrate: 0.4 µm TiN, 4 µm TiCN, 0.6 µm AlTiCNO bonding layer, 3.5 µm α-Al2O3 layer, and 0.05 µm outermost Cr color layer. Thus, the total coating thickness is 8.55 µm.

[0099] As described above, the texture coefficients of the TiCN layer of sample C measured by X-ray diffraction are as follows: 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 1 1)=0.22.

[0100] The texture coefficients of the α-Al2O3 layer of Sample C are as follows: 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, which were measured by X-ray diffraction using Cu Kα radiation and θ-2θ scans and are defined according to the Harris equation (F1), where I(hkl) is the (hkl) reflection I0(hkl) is the measured integrated area intensity, 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, and the (hkl) reflections used are those listed above.

[0101] The residual stress of the α-Al2O3 layer of sample C, measured in a manner corresponding to that described above using peak (1 1 6), is -0.92 GPa.

[0102] Coated cutting tools AS, BG, and C were tested in linear lateral radius milling operations on M2 stainless steel (SS2333) using the following cutting data:

[0103] Milling Cutter: R220.69-0063-12-6AN

[0104] Cutting speed v c : 100 m / min

[0105] Cutting feed fz: 0.2 mm / tooth

[0106] Cutting depth a p : 3 mm

[0107] Radial cutting depth a e : 12.6 mm

[0108] Length per pass: 300 mm

[0109] Workpiece overhang length: 200 mm

[0110] Lifespan criteria: Clearance wear > 0.3 mm

[0111] Machining was performed using a 6% coolant emulsion at a pressure of 40 Bar. Three cutting edges were evaluated per cutting tool. All edges of all variations were driven in the same manner and stopped when the flank wear reached 0.3 μm when observed using an optical microscope in relation to visible wear of the flank-side coating below the contact area with the workpiece at the nose of the cutting insert. The results are shown in Table 10.

[0112]

[0113] As can be seen in Table 10, the inventive example sample AS shows an extended life compared to comparative example samples BG and C.

[0114] Although the present invention has been described in relation to various exemplary embodiments, it should not be understood that the present invention is limited to the disclosed exemplary embodiments, but rather the present invention is intended to include various modifications and equivalent configurations within the scope of the appended claims.

Claims

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

00. Claim 2 In paragraph 1, the above ratio d b / d a A cutting tool with a value between 1.48 and 1.

80. Claim 3 A cutting tool according to claim 1 or 2, wherein the residual stress measured by XRD in the κ-Al2O3 layer is between -0.6 GPa and -2.0 GPa. Claim 4 In any one of claims 1 to 3, the average grain width d of the κ-Al2O3 grains measured along a line at a position corresponding to 80% of the thickness of the κ-Al2O3 layer (3). b A cutting tool with a diameter between 0.6 μm and 0.8 μm. Claim 5 A cutting tool according to any one of claims 1 to 4, wherein the thickness of the κ-Al2O3 layer (3) is between 4 μm and 5 μm. Claim 6 A cutting tool according to any one of claims 1 to 5, wherein the coating comprises a TiCN layer (2) between the substrate (1) and the κ-Al2O3 layer (3). Claim 7 A cutting tool according to claim 6, wherein the thickness of the TiCN layer (2) is between 1.5 μm and 2.5 μm. Claim 8 A cutting tool according to any one of claims 1 to 7, wherein the coating comprises an innermost TiN layer. Claim 9 A cutting tool according to claim 8, wherein the thickness of the innermost TiN layer is between 0.3 μm and 0.6 μm. Claim 10 A cutting tool according to claim 6 or 7, wherein the coating comprises a bonding layer between the TiCN layer (2) and the κ-Al2O3 layer (3), preferably wherein the bonding layer is one or more of TiCO, TiCNO, AlTiCO, or AlTiCNO. Claim 11 A cutting tool according to claim 10, wherein the thickness of the bonding layer is between 1.5 μm and 2.5 μm. Claim 12 In any one of claims 1 to 11, the surface roughness R of the substrate (1) on an inclined surface, measured in an SEM cross-section. a A cutting tool having a thickness between 0.05 μm and 0.2 μm, preferably between 0.15 μm and 0.2 μm. Claim 13 In any one of claims 1 to 12, the κ-Al2O3 layer (3) is measured by X-ray diffraction using Cu Kα radiation and θ-2θ scan and exhibits a texture coefficient TC(hkl) defined according to the following Harris equation, (F1) Here, I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, and 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(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, and n is the number of reflections used in the calculation, and the (hkl) reflections used are (1 1 1), (0 1 3), (1 2 2), (1 1 3), (2 A cutting tool comprising 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. Claim 14 In any one of claims 6 to 13, the TiCN layer (2) is measured by X-ray diffraction using Cu Kα radiation and θ-2θ scan and exhibits a texture coefficient TC(hkl) defined according to the Harris equation (F1), where I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, and I0(hkl) is the standard intensity, 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, and n is the number of reflections used in the calculation, and the used (hkl) The reflection is (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0), (4 2 2), (5 1 1), and TC(4 2 2) ≥ 3, preferably ≥ 4, more preferably ≥ 5, a cutting tool.

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