Coated Cutting Tools

Abstract

The present invention relates to a coated cutting tool consisting of a substrate and a multi-layer wear-resistant hard coating and a method for manufacturing the same, the layers of the hard coating being deposited by chemical vapor deposition (CVD) and including a multi-sublayer structure of alternating C-type and N-type sublayers and a TiCN layer having an overall fiber structure characterized by a texture coefficient TC(4 2 2) in the range of 3.0-5.5, an oxygen-containing Ti or Ti+Al compound bond layer, and an α-Al2O3 layer on top of the bond layer having an overall fiber structure characterized by a texture coefficient TC(0 0 12)>5.

Description

[Technical field]

[0001] The present invention relates to a coated cutting tool for chip-forming metal machining consisting of a substrate and a multi-layer wear-resistant hard-coating, where the layers of the hard-coating are deposited by chemical vapor deposition (CVD). [Background technology]

[0002] A typical cutting tool used in metal machining consists of a substrate such as cemented carbide, cermet, ceramic, steel or cubic boron nitride, and a single or multi-layer wear-resistant hard material coating deposited by CVD or PVD. Specifically, one type of high-performance cutting tool includes a substrate (base material) of cemented carbide, a thin base layer of TiC or TiN, a layer of TiCN, most often deposited as MT-TiCN (medium temperature CVD), followed by an alpha, kappa or mixed alpha + kappa Al2O3 layer. It is also known to provide a Ti compound or Ti + Al compound bond layer between the TiCN layer and the Al2O3 layer, which may be suitable for transferring crystallographic properties from the underlying TiCN layer to the Al2O3 layer and may affect the transformation, structure and adhesion of the Al2O3 layer. For example, some degree of oxidation at the surface of the Ti or Ti + Al compound bond layer may promote the formation of alpha Al2O3 rather than kappa transformation. An example can be found in US 7,172,807.

[0003] The performance and life of such cutting tools are influenced by various parameters, some of which are more or less dependent on the desired machining application, such as the work material, the intended cutting task, etc. However, there is still potential for improvement in the cutting tools themselves, particularly with regard to the coating properties and the balance between the different parts and layers of the coating that affect different wear types and enhance tool life and cutting performance.

[0004] Object of the invention It is an object of the present invention to provide a coated cutting tool having improved wear and oxidation resistance in continuous and interrupted cutting, and increased edge line toughness, especially for ISO P and ISO K steel applications. Summary of the Invention

[0005] The object is to provide a coated cutting tool for chip-forming metalworking, which comprises a substrate and a multilayer wear-resistant hard coating, a) a TiCN layer having a total thickness of 2 μm to 20 μm, the TiCN layer has a multi-sublayer structure with a total of p alternating C-type and N-type sublayers, where p is an even or odd number ranging from 5 to 25, preferably from 5 to 12; the C-type and N-type sublayers have different stoichiometries with respect to the atomic ratio of carbon and nitrogen, the C-type TiCN sublayer having a C / N ratio in the range of 1.0≦C / N≦2.0, the N-type TiCN sublayer having a C / N ratio in the range of 0.5≦C / N<1.0, and the difference in the C / N ratios of adjacent C-type and N-type layers being ≧0.2; The TiCN layer has an overall fiber structure characterized by a texture coefficient TC(4 2 2) in the range of 3.0 to 5.5, TC(4 2 2) being as follows: TIFF2024526245000002.tif18170 (in the formula, I(hkl) = XRD intensity of the (hkl) reflection I0(hkl) = Standard intensities of standard powder diffraction data from ICDD PDF card number 01-071-6059 n=7=the number of reflections used in the calculation, so the seven (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). The TiCN layer is defined as follows: b) a single or multi-sublayer oxygen-containing Ti or Ti+Al compound bonding layer on the TiCN layer, with a total thickness of 0.5 μm to 3 μm; c) an α-Al2O3 layer on top of the bonding layer with a total thickness of 2 μm to 15 μm; The α-Al2O3 layer has an overall fibrous texture characterized by a texture coefficient TC(0 0 12)>5, where TC(0 0 12) is equal to or greater than the following: TIFF2024526245000003.tif18170 (in the formula, I(hkl) = XRD intensity of the (hkl) reflection I0(hkl) = Standard intensity measured with NIST standard powder SRM676a n=8=the number of reflections used in the calculation, so the 8 (hkl) reflections used are: (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (3 0 0), (0 0 12) and (0 1 14). The α-Al2O3 layer is defined as follows: Standard strength is: Solved by coated cutting tool, with TIFF2024526245000004.tif20170.

[0006] Hereinafter, the terms "{2 1 1} texture of TiCN layers" and "{0 0 1} texture of α-Al2O3 layers" refer to preferred crystallographic orientations in polycrystalline layers, where the respective crystallographic planes are oriented parallel to the substrate surface (perpendicular to the growth direction of the layer) more frequently than randomly oriented. The preferred crystallographic orientations are determined herein by XRD and are represented by the texture coefficients of the corresponding (parallel) crystallographic {4 2 2} and {0 0 12} planes, TC(4 2 2) for TiCN layers and TC(0 0 12) for α-Al2O3 layers, respectively.

[0007] Attempts to improve the properties and performance of cutting tools must consider several aspects simultaneously. It was found that the control of high {0 0 1} texture of the α-Al2O3 layer, represented by the texture coefficient TC(0 0 12)>5, is important for high oxidation and crater wear resistance. Preferably, the texture coefficient TC(0 0 12) of the α-Al2O3 layer is >6. On the other hand, it was found that the flank wear resistance is strongly influenced by the microstructure and texture of the TiCN layer of the coating layer sequence. Another characteristic essential for the performance and tool life of cutting tools is the edge line toughness, which may be limited by the adhesion of the coating layers at the layer interface. Low adhesion leads to fracture, chipping and / or delamination and thus premature failure of the tool. The inventors have found a novel coated cutting tool that, due to the specific coating sequence and the respective properties of the coating layers, results in improved edge line toughness and flank wear, as well as improved oxidation and crater wear resistance.

[0008] In the best mode of the coated cutting tool of the present invention, the layer of hard coating is deposited by chemical vapor deposition (CVD), and the TiCN layer having a multi-sublayer structure is a MT-TiCN layer deposited by MT-CVD at a reaction temperature in the range of 600° C. to 900° C. The polycrystalline TiCN layer consists of columnar grains.

[0009] The Ti or Ti+Al compound bond layer is preferably deposited by HT-CVD with a reaction temperature in the range of 900°C to 1200°C, and the α-Al2O3 layer is also preferably deposited by HT-CVD with a reaction temperature in the range of 900°C to 1200°C.

[0010] It was known that a certain degree of oxidation in the Ti or Ti+Al compound layer beneath the Al2O3 layer favors the nucleation and subsequent growth of the alpha modification over other modifications. However, it was found that the development and level of organization of the α-Al2O3 layer is determined to some extent not only by the deposition conditions of the Al2O3 layer itself but also by the microstructure and crystallographic orientation of the underlying TiCN layer. Thus, control of the TiCN layer is essential for controlling the properties of the subsequent α-Al2O3 layer.

[0011] The inventors have realized that a fine-grained TiCN layer with a high {2 1 1} texture promotes the controlled nucleation and deposition of a high {0 0 1} textured α-Al2O3 layer and high flank wear resistance of the coating. Therefore, in a first attempt, a maximum possible {2 1 1} texture of the TiCN layer is envisaged to improve the advantageous properties resulting from a high {0 0 1} textured α-Al2O3 layer and flank wear resistance.

[0012] However, the inventors have further found through numerous experiments and analyses that the adhesion at the interface, especially between the α-Al2O3 layer and the underlying bond layer of the coating, is strongly influenced by the microstructure and crystallographic orientation of the TiCN layer. It has been found that the high {0 0 1} texture of the α-Al2O3 layer and the high {2 1 1} texture of the TiCN layer, which promotes the advantage of high flank wear resistance, is often combined with a very weak adhesion at the interface between the α-Al2O3 layer and the bond layer, which leads to fractures and chipping, especially at the cutting line of the tool, and thus loss of tool performance and tool life.

[0013] This contradiction can be resolved according to the present invention by a multilayer wear-resistant hard coating as defined herein, where the TiCN layer has a multi-sublayer structure with a specific number of alternating C-type and N-type sublayers of well-defined C / N ratio between 5 and 25, and the TiCN layer has a {2 1 1} texture, represented by a texture coefficient TC(4 2 2) within the specified range of 3.0 to 5.5. Preferably, the texture coefficient TC(4 2 2) is between 3.5 and 5.5, or between 4.0 and 5.3.

[0014] On the one hand, the texture coefficient TC(4 2 2) of the TiCN layer is high enough to promote the growth and advantageous properties of the subsequent α-Al2O3 layer. On the other hand, it was found that by limiting the texture coefficient TC(4 2 2) of the TiCN layer, adhesion problems between the α-Al2O3 layer and the tie layer are reduced or avoided.

[0015] To achieve these properties, it has been found advantageous to deposit a multi-sublayer TiCN layer consisting mainly of C-type TiCN, where the growth of C-type TiCN is regularly interrupted by the deposition of N-type TiCN sublayers. The interruption of the growth conditions of C-type TiCN by sublayers of N-type TiCN is hypothesized and found to control the {2 1 1} texture of the TiCN layer, represented herein by the texture coefficient TC(4 2 2). While C-type TiCN promotes the {2 1 1} texture of the TiCN layer, the type and number of N-type TiCN sublayers are suitable to control and adjust the limitations of the {2 1 1} texture of the TiCN layer. The deposition of a single N-type layer alone has been found to entail disadvantages such as randomly textured crystals and / or very coarse grains.

[0016] It has been shown that in multi-sublayer structures of TiCN layers, the best properties and control of the {2 1 1} texture of the TiCN layer are achieved when the N-type sublayers are thinner than the adjacent C-type sublayers. Preferably, each N-type sublayer has a thickness less than 50%, or less than 40%, or less than 30% of each of the adjacent C-type sublayers. On the other hand, each N-type sublayer should have a thickness of at least 0.05 μm, or at least 0.1 μm, or at least 0.2 μm. Otherwise, the effect of the N-type sublayers to control the texture of the TiCN multilayer is too low.

[0017] The change between the C-type sublayer and the N-type sublayer during the deposition of the TiCN layer is controlled by the deposition conditions, particularly the change in the reaction gas composition. The thicknesses of the C-type and N-type sublayers are controlled by the deposition time under their respective C-type and N-type conditions. The deposition rates under different C-type and N-type conditions do not necessarily have to be the same, but it should be mentioned that it is within the skill range of those skilled in the art to find the respective deposition rates under specific conditions through simple experiments.

[0018] Also, it has been found that in order to achieve the desired properties of the TiCN layer, the number of alternating C-type and N-type sublayers should not be too few or too many. To control the {2 1 1} texture of the TiCN layer within the range of the beneficial texture coefficient TC(4 2 2), it has been found that the number of alternating C-type and N-type sublayers of 5 to 25 is advantageous.

[0019] According to the present invention, the C-type TiCN sublayer has a C / N ratio in the range of 1.0 ≦ C / N ≦ 2.0, and the N-type TiCN sublayer has a C / N ratio in the range of 0.5 ≦ C / N < 1.0. In one embodiment of the present invention, the C-type TiCN sublayer has a C / N ratio in the range of 1.2 ≦ C / N < 1.5, and the N-type TiCN sublayer has a C / N ratio in the range of 0.7 < C / N < 1.0. The effect of interrupting the growth of C-type TiCN by the deposition of alternating N-type TiCN sublayers can be affected not only by the number of N-type sublayers that interrupt the C-type, but also by the adjustment of the C / N ratio and the difference in the C / N ratio between the C-type sublayer and the N-type sublayer. In the deposition process, the C / N ratio of the deposited layer is adjusted by the deposition conditions, mainly the ratio of the N donor to the C donor. In a reaction gas system containing N2 and CH3CN as N and C sources, the C / N ratio is adjusted by the ratio of these precursor gases.

[0020] According to the present invention, the difference in the C / N ratio between adjacent C-type and N-type layers is ≧ 0.2. In a preferred embodiment of the present invention, the difference in the C / N ratio between the C-type layer and the N-type layer is in the range of 0.3 to 1.5, or 0.4 to 1.0, or 0.5 to 0.8. If the difference in the C / N ratio between adjacent C-type and N-type layers is too small, the desired effect of controlling the crystallographic properties of the TiCN layer is too weak.

[0021] The substrate of the coated cutting tool of the present invention may be of any type known in the art to be suitable for metal cutting tools, such as cemented carbide, cermet, ceramic, steel or cubic boron nitride, whereby cemented carbide is particularly suitable and preferred.

[0022] The coated cutting tools of the present invention have been found to exhibit excellent wear and oxidation resistance, as well as improved edge line toughness in continuous and interrupted cuts, particularly in turning operations in ISO-P and ISO-K steel workpiece applications. Thus, the present invention includes the use of the coated cutting tools of the present invention for continuous and interrupted cuts of ISO-P and ISO-K steel materials.

[0023] In a preferred embodiment of the coated cutting tool of the present invention, at least one base layer of TiN or TiC is deposited immediately on the substrate surface and beneath the TiCN layer. Suitable base layers have a thickness in the range of 0.3-1.5 μm, or 0.3-1.0 μm, or 0.3-0.7 μm. The base layer can be deposited by thermal HT-CVD or MT-CVD.

[0024] The underlayer is suitable for improving the adhesion of the TiCN layer to the substrate and can also act as a barrier layer to avoid or at least reduce the diffusion of elements such as Co from the substrate to the TiCN coating layer and vice versa during subsequent high temperature processing such as during HT-CVD alumina deposition.

[0025] In a preferred embodiment of the coated cutting tool of the present invention, in the multi-sublayer structure of the TiCN layer in the growth direction, the first sublayer above the base layer is a type C layer. In another preferred embodiment, both the first sublayer above the base layer and the last sublayer below the bonding layer are type C layers.

[0026] As mentioned above, the major proportion of the multi-layered TiCN layer is C-type TiCN, which has been found to be the type that promotes the {2 1 1} texture of the TiCN layer and thus the {0 0 1} texture of the α-Al2O3 layer, while the N-type sublayer is preferably interposed to control the development of the {2 1 1} texture of the TiCN layer. However, it has been found that when the N-type layer is deposited as the first sublayer on top of the base layer, there is less development of the {2 1 1} texture of the TiCN layer and, as a result, less of the {0 0 1} texture of the α-Al2O3 layer. If the final sublayer below the tie layer is also a C-type layer, the effect is further enhanced and better control of the {0 0 1} texture of the α-Al2O3 layer is achieved.

[0027] Regarding the multi-sublayer structure of the TiCN layer, there are two preferred variants of the coated cutting tool of the invention.

[0028] In a first variant, the first C-type sublayer in the growth direction is relatively thick, with a thickness in the range of 5-15 μm, the subsequent C-type sublayers are thinner, with a thickness in the range of 0.5-4 μm, and further thinner N-type sublayers are deposited between the C-type layers. In this variant, in the first stage, the first thicker C-type sublayer develops a pronounced {2 1 1} texture, setting a kind of template for the subsequent layers.

[0029] In a second variant, each C-type sublayer in the growth direction has a thickness in the range of 0.5-4 μm, and further thinner N-type sublayers are deposited between the C-type layers. This variant also works very well and is particularly suitable when the number of alternating C-type and N-type sublayers in the TiCN layer is within the upper range and the total thickness of the TiCN layer should not be too high.

[0030] The bond layer of the coating of the invention is a single or multi-sublayer oxygen-containing Ti or Ti+Al compound layer deposited on a TiCN layer with a total thickness of 0.5 μm to 3 μm. Preferably, the bond layer has a multi-sublayer structure and a total composition of TiCNO or TiAlCNO. In the CVD deposition of the bond layer, oxygen can be introduced by adding carbon monoxide CO to the reaction gas composition. In a preferred embodiment, the deposited bond layer is subjected to a further oxidation step before the subsequent nucleation and growth of the Al2O3 layer. The presence of oxygen in the Ti or Ti+Al bond layer and the oxidation of the bond layer surface are favorable to promote the growth of the Al2O3 layer in the α modification.

[0031] The present invention also relates to a method for manufacturing a coated cutting tool of the invention as defined herein, in which the multi-layer wear-resistant hard coating is deposited on a substrate by chemical vapor deposition (CVD), comprising the steps of: - depositing a multi-sublayer TiCN layer of a total of p alternating C-type and N-type sublayers, where p is an even or odd number ranging from 5 to 20, to a total thickness of 2 μm to 20 μm by MT-CVD at a reaction temperature ranging from 600 °C to 900 °C from a process gas composition comprising at least TiCl4, H2, N2 and CH3CN, and optionally HCl; the C-type and N-type sublayers have different stoichiometries with respect to the atomic ratio of carbon and nitrogen, the C-type TiCN sublayer having a C / N ratio in the range of 1.0≦C / N≦2.0 and the N-type TiCN sublayer having a C / N ratio in the range of 0.5≦C / N<1.0, the difference in the C / N ratios of adjacent C-type and N-type layers being ≧0.2, and the C / N ratio being adjusted by the ratio of N2 / CH3CN in the process gas composition; - depositing a single or multi-sublayer oxygen-containing Ti or Ti+Al compound bond layer on the TiCN layer by thermal HT-CVD or MT-CVD from a process gas composition comprising at least TiCl4, H2, N2, CO, and AlCl3 if Al is present, and optionally CH4 and / or HCl, to a total thickness of 0.5 μm to 3 μm; - carrying out an oxidation step on the bonding layer at a temperature in the range of 900-1200 °C, a pressure in the range of 30-150 mbar, a duration of 2-20 minutes and in a gas atmosphere comprising or consisting of H2, N2, 1-10 vol.% CO2 and 1-20 vol.% CO, - depositing an α-Al2O3 layer with a total thickness of 2 μm to 15 μm on the bond layer treated in the oxidation step by HT-CVD at a reaction temperature in the range of 900 °C to 1200 °C; The present invention includes a method comprising the steps of:

[0032] Preferably, the method includes the further step of depositing at least one underlayer of TiN or TiC immediately on the substrate surface by thermal HT-CVD or MT-CVD from a process gas composition comprising at least TiCl4, H2 and N2 to a underlayer thickness in the range of 0.3 to 1.5 μm.

[0033] The Ti or Ti+Al compound bond layer is preferably deposited by several subsequent deposition steps to obtain a multi-sublayer structure, each deposition step being carried out by HT-CVD at a reaction temperature in the range of 900°C to 1200°C. In the examples herein, the bond layer is deposited in a five-step process, starting with a TiCN sublayer, followed by several steps under process conditions including CO in the reaction gas to incorporate oxygen into the layer, and a step including AlCl3 to incorporate Al into the layer. The total (overall) composition of the bond layer is Ti+Al+C+N+O. The deposition of the bond layer is followed by an oxidation step at high temperatures in the range of 900°C to 1200°C, preferably around 1000°C, in a gas atmosphere including H2, N2, CO2 and CO. [Brief description of the drawings]

[0034] [Figure 1] FIG. 1 shows examples of optical micrographs (LOM) of polished carrot-ground surfaces of coatings of different A adhesion classifications (FIG. 1a: A=1; FIG. 1b: A=2; FIG. 1c: A=3). [Diagram 2]Figure 2 shows the average values ​​of A and Z adhesion for inventive and comparative examples of coated cutting tool samples plotted against the number of sublayers of the TiCN layer (Fig. 2a) and against the texture coefficient TC (4 2 2) of the TiCN layer (Fig. 2b), respectively. [Diagram 3] 3A, 3B: 4WAG51; FIG. 3C, 3D: 4WAG60) and the reference sample (FIG. 3E, 3F: 1246260) after crater wear tests (turning operations in C45E steel) for a cutting time of 12 min (FIG. 3A, 3C, 3E) and 15 min (FIG. 3B, 3D, 3F) optical microscopy pictures of the crater wear of the inventive samples (FIG. 3A, 3B: 4WAG51; FIG. 3C, 3D: 4WAG60) and the reference sample (FIG. 3E, 3F: 1246260) after crater wear tests (turning operations in C45E steel) for a cutting time of 12 min (FIG. 3A, 3C, 3E) and 15 min (FIG. 3B, 3D, 3F) [Figure 4] FIG. 4 shows the flank wear of the 4WAG51, 4WAG60 and reference 1246260 samples shown in FIG. 3 after each 3 minute cycle in the Crater Wear Test. [Diagram 5] FIG. 1 shows the flank wear of the inventive samples 4WAG51 and 4WAG55 and the reference sample 1246260 in toughness testing, where the maximum wear width is plotted against the number of cycles and the edge line damage (ELD) of each sample at the end of the tool life is shown (VBmax ≧0.3 mm on the flank). [Figure 6] Figure 5a shows an example of a TEM (Figure 5a) and an EDXS line scan (Figure 5b) along the line AB in the layer growth direction of a sample of TiCN layers according to the invention. In the TEM image, a thicker C-type sublayer (light) is interrupted by six thin N-type sublayers (dark). The EDXS line scan shows the concentrations of Ti, C and N in % over a length of about 4 μm of the line AB. In this sample, the average C / N ratio of the C-type sublayers was about 1.42 and the average C / N ratio of the n-type sublayers was about 0.85, as determined by EDXS. The C / N ratio results could be confirmed by EELS line scans. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Definitions and Methods MT-TiCN The term "MT-TICN" as used herein means that the TiCN is deposited by medium temperature CVD (MT-CVD), which distinguishes it from material deposited by high temperature CVD (HT-CVD).

[0036] X-ray diffraction (XRD) measurements X-ray diffraction measurements were performed on a Panalytical CubiX3 diffractometer using CuKα radiation and a PIXcel 1D RTMS detector. The X-ray tube was operated at 45 kV and 40 mA with line focus. Measurements were performed in Bragg-Brentano geometry. On the primary beam side, a 0.04 rad Soller slit, a 0.5° fixed divergence slit, and a 1° anti-scatter slit were used. A 1.6 mm wide beam mask was inserted to avoid the X-ray beam spilling over onto the coated surface of the sample. On the secondary side, a 8 mm fixed anti-scatter slit, a 0.04 rad Soller slit, and a 20 μm thick NiKβ filter were used. Symmetric θ-2θ scans were performed in the angular range of 19° ≤ 2θ ≤ 130° with 0.0158° increments and approximately 0.2 s counting time.

[0037] Data analysis was performed using a Matlab-based peak fitting procedure by fitting pseudo-Voigt profiles to the measured 2θ scans after Cu-Kα2 stripping (Rachinger method) and background subtraction. Peak intensities herein are peak area intensities. A thin film absorption (TF) correction was applied to all samples, which takes into account the limited thickness of the layer, as opposed to the natural penetration depth in the bulk material. In addition, an absorption correction (Abs) was applied for the layer deposited on top of each layer of interest. The formulas applied for the thin film (TF) correction and the absorption (Abs) correction are known to those skilled in the art and are shown below: TIFF2024526245000005.tif30170

[0038] The thin film correction formula (I TF corr), where S is the thickness of the layer of interest and the absorption correction formula (I Abs corr ), where S is the thickness of the absorbing top layer. "μ" is the linear absorption coefficient of each layer material, μ(α-Al2O3) = 0.01258 μm -1 and μ(TiCN)=0.08150μm -1 (See also Birkholz, Thin Film Analysis by X-ray Scattering, 2006, Wiley-VCH, ISBN 3-527-31052-5, Chapter 5.5.3, pp. 211-215).

[0039] Because the tie layer is thinner than the TiCN coating, has the same crystal structure, and similar chemical composition, the overlapping interference peaks of both layers cannot be separated or reliably deconvoluted, so separate absorption and thin film corrections were not made for the tie layer over the TiCN coating; instead, they are treated as one layer.

[0040] Texture coefficient TC(hkl) The term "fiber texture", as it is commonly used in reference to polycrystalline thin films produced by vapor deposition, describes the preferential crystallographic orientation of the grown grains, in that a set of geometrically equivalent crystallographic planes {hkl} are found preferentially oriented parallel to the substrate surface, as compared to a random orientation.

[0041] A measure of preferred growth, i.e., that a set of geometrically equivalent crystallographic planes {hkl} are found to be preferentially oriented parallel to the substrate, is the texture coefficient TC(hkl), calculated using the formula proposed by Harris, based on a defined set of XRD reflections measured on each sample (Harris, GB, Philosophical Magazine Series 7, 43 / 336, 1952, pp. 113-123). According to Harris' formula, the measured peak intensity I(hkl) correlates with the relative standard intensity I0(hkl), obtained from the PDF card of the respective lCDD or measured on a standard reference powder. TIFF2024526245000006.tif18170

[0042] A texture coefficient TC(hkl)>1 for a layer of crystalline material indicates that the grains of the crystalline material are more frequently oriented with their {hkl} crystallographic planes parallel to the substrate surface than with a random distribution, at least as compared to the XRD reflections used in the Harris formula. In the calculation of the texture coefficient TC(hkl) herein, the measured peak intensities I(hkl) refer to the net peak area intensities corrected as above.

[0043] For TiCN, ICDD PDF card number 01-071-6059 was applied and the following (hkl) reflections were used in the calculations (n=7): TIFF2024526245000007.tif20170

[0044] For α-Al2O3, the standard peak area intensity I0(hkl) was obtained by measuring as above using the certified NIST (National Institute of Standards and Technology) standard powder SRM676a. The following (hkl) reflections were used in the calculation (n=8): TIFF2024526245000008.tif20170

[0045] Scanning Electron Microscope (SEM) For SEM analysis, the inserts were cut in cross section, mounted in a holder, and processed by i) grinding with Struers Piano220 disks and water for 6 min, ii) polishing with 9 μm MD-Largo Diamond suspension for 3 min, iii) polishing with 3 μm MD-Dac Diamond suspension for 3:40 min, iv) polishing with 1 μm MD-Nap Diamond suspension for 2 min, and v) polishing / etching with OP-S colloidal silica suspension for at least 12 min (average particle size of colloidal silica = 0.04 μm). Before SEM examination, the specimens were ultrasonically cleaned. SEM images were acquired with a Zeiss Supra 40 VP field emission scanning electron microscope using a 30 μm aperture, an accelerating voltage of 2.5 kV, and a working distance of 5 mm.

[0046] Sample preparation for TEM analysis Samples for TEM were prepared by an in-situ lift-out technique in which a combined FIB / SEM Zeiss Crossbeam 540 field emission scanning electron microscope equipped with a gallium liquid metal ion source was used to cut thin cross-sections from the surface and thin the sample sufficiently to be electron transparent.

[0047] Analytical Transmission Electron Microscopy (TEM) Investigations (STEM-EDXS) The combination of scanning transmission electron microscopy (STEM) imaging and elemental mapping by energy dispersive X-ray spectroscopy (EDXS) was performed with a FEI Tecnai Osiris microscope at a primary electron energy of 200 keV and an electron current of 1 nA, equipped with a high-brightness field emission electron gun and four silicon drift detectors (FEI Super-X EDX system).

[0048] STEM-EDXS mapping was used to determine the sublayer thicknesses of the C-type and N-type layers, respectively. The obtained quantitative line profiles of elemental distribution show high homogeneity and reproducibility of the stack of alternating C-type and N-type layers. The C / N ratio was determined by line profile fitting using Matlab.

[0049] Electron Energy Loss Spectroscopy (EELS) Electron energy loss spectroscopy (EELS) was performed using an FEI Titan 80-300 microscope at 300 kV with a GIF Tridiem 865 ER type Gatan imaging energy filter. EELS line profile analysis was performed in STEM mode. For accurate quantification of the C / N ratio, high spatial resolution EELS analysis was applied. These measurements corroborate the data from the STEM EDXS analysis.

[0050] Carrot Grinding / Ball Cratering Carrot grinding was used to evaluate the coating thickness and adhesion. The inserts were placed on an inclined magnetic holder of a ball cratering device. A rotating 30 mm steel ball, wetted with a drop of 3 μm aqueous diamond suspension (Struers, DP-Lubricant Green) and driven by a drive shaft at >500 rpm, ground the spherical carrots with the coating and substrate material. The grinding process was stopped when the carrot diameter of the substrate material reached approximately 600-1100 μm. Thickness measurements, taking into account the carrot shape, were performed using optical microscopy (LOM) with dedicated software.

[0051] A and Z Adhesives "A adhesion" defines the adhesion of the α-Al2O3 layer to the bond layer, and "Z adhesion" defines the internal adhesion within the bond layer, i.e. between the individual sublayers of the bond layer. A and Z adhesion were assessed by LOM observation of polished carrot-ground surfaces and visually classified on a scale of 1.0 (= complete adhesion) to 3.0 (= no adhesion).

[0052] The criteria for A and Z adhesion at the layer / sublayer interface are as follows: A or Z=1: No or negligible breakout is observed at the contact surface. The contact line is intact. A or Z=2: Minor breakouts can be observed at the contact surface, and approximately 51-80% of the entire contact surface line is not degraded. A or Z=3: Large breakouts or continuous delamination can be observed at the contact surface, and 50-100% of the carrot contact surface line is degraded.

[0053] Figures 1a, 1b and 1c show examples of A adhesion (Figure 1a: A=1; Figure 1b: A=2; Figure 1c: A=3).

[0054] CVD Coating All CVD coatings herein were prepared in an industrial size Bernex BPX530L radial flow CVD coating chamber with an internal reactor height of 1580 mm, an internal reactor diameter of 500 mm, and an internal volume of approximately 300 L. Reactant gases were fed into the reactor through a central gas inlet pipe and introduced into the reaction zone through orifices distributed along the inlet pipe, providing a substantially radial gas flow over the substrate body.

[0055] It should be noted that a large number of cutting tool insert substrates (up to about 15.000 inserts) may be located at different tray levels in the reactor and at different radial distances from the reaction gas outlet opening. Thus, the total gas flow, gas velocity, and type of deposition reaction may change the reaction gas composition and therefore the reactivity at different substrate positions in the same reactor, which may change the coating thickness and other product parameters of the coated substrates in the same deposition run under the same nominal reaction conditions. This is a phenomenon well known to those skilled in the art. However, it is within the understanding of those skilled in the art to reduce or overcome such variations by adjustments known in the art, such as adjustments of total gas flow, gas velocity, deposition time, etc., to achieve the coating properties of the present invention.

[0056] Unless otherwise indicated, in the examples herein, the reactor was filled with inserts to nearly its full capacity, whereby the sample inserts investigated were located at three different radial locations on the tray from the central inlet pipe (locations: central (C), middle (M), peripheral (P)), and at six different tray levels within the height of the reactor. The remaining locations on the tray were filled with "scrap" inserts to simulate as closely as possible the full-scale deposition conditions and volumetric usage in the reactor.

[0057] Unless otherwise indicated, in the examples herein, measurements shown for samples such as layer thickness, texture coefficient, A and Z adhesion, etc. represent the average of 18 samples taken from 18 different locations within the reactor as described above.

[0058] Blast Blasting of the deposited coating, if performed, was performed on the rake face of the insert. Dry blasting ("TS") was performed with 70-120 μm diameter ZrO2 round media, blast pressure of 5 bar (injector presser = 1.8 bar), and blast distance of 90 mm. Wet blasting ("TT") was performed with a blaster slurry of 20 vol% Al2O3 in water (F240 microgrit), blast pressure of 2.8-3.8 bar (injector presser = 1.-2.0 bar), blast angle of 75°, and blast distance of 94.5 mm.

[0059] Crater Abrasion Test The coated cutting tools were tested with C45E steel using the following cutting data: cutting speed v c :270m / min Cutting feed, f: 0.32mm / revolution Cutting depth, a p :2.5mm Insert style: WNMG080412 (No cutting fluid)

[0060] One cutting edge per cutting tool was evaluated. For crater wear analysis, optical microscopy was used to measure the area of ​​exposed substrate. The tool life was considered to be reached when the wear crater formed by the flowing chip broke through / reached the minor cutting edge. The wear of each cutting tool was evaluated by optical microscopy after 3 minutes of cutting. The cutting process was then continued with measurements every 3 minutes of operation until the tool life criterion was reached. In addition to the crater wear, flank wear was also observed.

[0061] Toughness Test - Edge Line Damage (ELD) Coated cutting tools (blasted or non-blasted) were tested in an intermittent turning operation in C45E steel with the following cutting data: cutting speed v c :200m / min Cutting feed, f: 0.2mm / revolution Cutting depth, a p :2.64mm Insert style: WNMG080412

[0062] The workpiece material consisted of C45E. The intermittent cutting process in this type of test has been shown to be critical to tool life. 70% edge line damage (ELD) (criterion #1) or 0.3 mm flank wear VB max The end of tool life was assumed to be reached when (criterion #2) was met or exceeded, whichever occurred first. Water miscible metal working fluids were used. EXAMPLES

[0063] Base material In this example, cemented carbide substrates with cutting insert geometries ISO types CNMA120412 and WNMG080412 were used. The cemented carbide composition was WC 86.11 wt.%, Co 5.48 wt.%, TaC 3.52 wt.%, TiC 2.12 wt.%, NbC 2.33 wt.%, and other carbides 0.44 wt.%. The substrate has a Co binder enriched surface zone approximately 20 μm from the substrate surface.

[0064] For the CVD deposition, inserts of two different geometries CNMA120412 and WNMG080412 were coated in the same deposition run under the same conditions by placing at least one insert of geometry CNMA120412 and one insert of geometry WNMG080412 side-by-side at the same radius and tray level position in the CVD reactor. CNMA120408 inserts were used for coating analysis and measurements (including A and Z adhesion analysis) as they have a simpler geometry and flatter surface and are therefore easier to handle, while WNMG080412 inserts, which are a common turning tool insert geometry for steel machining, were used for cutting tests.

[0065] deposition The coating sequence in the deposition of the examples herein was: TiN base layer / TiCN coating (MT-TiCN) / TiAlCNO bond layer / α-Al2O3 layer. Prior to depositing the α-Al2O3 layer, the bond layer was subjected to an oxidation step. In all inventive and comparative examples prepared herein, the TiN base layer, TiAlCNO bond layer, oxidation step and α-Al2O3 layer were deposited and carried out under the same process conditions, respectively, so that the examples are comparable in terms of the variants of single or multi-layer TiCN coatings.

[0066] The process parameters for the deposition of the layers of the inventive and comparative samples are given in Table 1, and the TiCN coating sequence is given in Table 3. The process steps and parameters for the deposition of the layers of reference sample 1246260 are given in Table 2. The parameters measured on the samples (average of 18 each of the inventive and comparative samples, distributed in the reactor as described above) are given in Table 4.

[0067] The TiN base layer was approximately 0.3-0.5 μm thick. The TiAlCNO bond layer was approximately 1.0-1.5 μm thick. The α-Al2O3 layer was approximately 5.5-6.5 μm thick. The thickness of the TiCN coating ranged from approximately 7.5-11.0 μm thick.

[0068] The bonding layer consisted of a multi-sublayer structure deposited with Be from five coating steps BL-a. The deposition of α-Al2O3 was carried out in two steps, step 1 and step 2.

[0069] Adhesion analysis The average values ​​of A and Z adhesion of the inventive and comparative samples (see Tables 3 and 4) were determined and plotted against the number of multilayers (Fig. 2a; #-ML) and the texture coefficient TC(4 2 2) of the TiCN layer (Fig. 2b), respectively. In the dashed boxes in Fig. 2a and 2b, the monolayer samples (#-ML=1) using TiCN-C and TiCN-D are marked. The results show that #-ML and TC(4 2 2) have little effect on the Z adhesion, even for the monolayer samples. However, a strong negative linear dependence of A adhesion on #-ML and a strong positive linear dependence of A adhesion on TC(4 2 2) were observed. Both monolayer samples show very weak A adhesion. The multisublayer samples within the #-ML and TC(4 2 2) range of the inventive TiCN layer show improved A adhesion and at the same time improved cutting properties. TIFF2024526245000009.tif255170TIFF2024526245000010.tif255170TIFF2024526245000011.tif216170TIFF2024526245000012.tif138170

[0070] Toughness Test Edge line toughness tests were performed on the reference specimen (1246260) and two inventive specimens (4WAG51 and 4WAG55). Each specimen was post-treated with "TS+TT" = dry blast followed by wet blast as described above. All specimens had a flank wear VB length of 0.3 mm (end of tool life criterion #2) before reaching 70% edge line damage (ELD) (end of tool life criterion #1). max Therefore, the ELD was determined for each specimen after the end of tool life due to flank wear. The results are shown in Table 5 below and in Figure 5. TIFF2024526245000013.tif38170

[0071] Crater wear The inventive samples 4WAG51 and 4WAG60 and the reference sample 1246260 were subjected to the above-mentioned crater wear test (turning operation of C45E steel) for 12 and 15 minutes, respectively. Figure 3 shows the observed (LOM) wear of the inventive samples. (Figures 3a = 4WAG51, 12 minutes; 3b = 4WAG51, 15 minutes; 3c = 4WAG60, 12 minutes; 3d = 4WAG60, 15 minutes; 3e = 1246260, 12 minutes; 3f = 1246260, 15 minutes). The results show that the crater wear of the inventive and reference samples after 12 minutes was comparable, but the wear of the inventive samples after 15 minutes was still acceptable, whereas the cutting edge as well as the rake and flank of the reference sample was almost completely destroyed. Figure 4 shows the flank wear of the samples after each cycle of 3 minutes in the crater wear test.

Claims

1. 1. A coated cutting tool for chip-forming metal machining comprising a substrate and a multi-layer wear-resistant hard coating, a) a TiCN layer having a total thickness of 2 μm to 20 μm; the TiCN layer has a multi-sublayer structure with a total of p alternating C-type and N-type sublayers, where p is an even or odd number ranging from 5 to 25, preferably 5 to 12; the C-type and N-type sublayers have different stoichiometries with respect to the atomic ratio of carbon and nitrogen, the C-type TiCN sublayer having a C / N ratio in the range of 1.0≦C / N≦2.0 and the N-type TiCN sublayer having a C / N ratio in the range of 0.5≦C / N<1.0, and the difference in the C / N ratios of adjacent C-type and N-type layers being ≧0.2; The TiCN layer has an overall fiber texture characterized by a texture coefficient TC(4 2 2) in the range of 3.0 to 5.5, where TC(4 2 2) is as follows: (In the formula, I(hkl) = XRD intensity of the (hkl) reflection I ０ (h k l) = standard intensities of standard powder diffraction data according to ICDD PDF card number 01-071-6059 n=7=the number of reflections used in the calculation, so the seven (h k l) 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) A TiCN layer, defined as follows: b) a single or multi-sublayer oxygen-containing Ti or Ti+Al compound bonding layer on top of the TiCN layer, with a total thickness of 0.5 μm to 3 μm; c) α-Al on top of the tie layer, with a total thickness of 2 μm to 15 μm ２ O ３ layer, α-Al ２ O ３ The layer has an overall fiber texture characterized by a texture coefficient TC(0 0 12)>5, where TC(0 0 12) is as follows: (In the formula, I(hkl) = XRD intensity of the (hkl) reflection I ０ (h k l) = standard intensity measured with NIST standard powder SRM676a n=8=the number of reflections used in the calculation, so the eight (h k l) reflections used are: (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (3 0 0), (0 0 12) and (0 1 14) α-Al is defined as follows: ２ O ３ layer, Standard intensities are as follows: A coated cutting tool comprising:

2. 2. The coated cutting tool of claim 1, wherein at least one underlayer of TiN or TiC is deposited immediately on the substrate surface and beneath the TiCN layer, the underlayer having a thickness in the range of 0.3 to 1.5 μm, or 0.3 to 1.0 μm, or 0.3 to 0.7 μm.

3. The coated cutting tool of claim 1, wherein the TiCN layer has an overall fiber texture characterized by a texture coefficient TC(4 2 2) in the range of 3.5 to 5.5 or 4.0 to 5.

3.

4. The coated cutting tool of claim 1 , wherein in the multi-sublayer structure of the TiCN layer in the growth direction, the first sublayer above the base layer and the last sublayer below the bonding layer are C-type layers.

5. 2. The coated cutting tool of claim 1, wherein in the multi-sublayer structure of the TiCN layer, each N-type sublayer has a thickness less than 50%, or less than 40%, or less than 30% of each of the adjacent C-type sublayers.

6. The coated cutting tool of claim 1 , wherein in the multi-sublayer structure of the TiCN layer, each N-type sublayer has a thickness of at least 0.05 μm, or at least 0.1 μm, or at least 0.2 μm.

7. In the multi-sublayer structure of the TiCN layer in the growth direction, the first type C sublayer has a thickness in the range of 2 to 15 μm and the subsequent type C sublayer has a thickness in the range of 0.5 to 4 μm, or A coated cutting tool according to claim 1, wherein all C-type sublayers have a thickness in the range of 0.5 to 4 μm.

8. The coated cutting tool of claim 1 , wherein the Ti or Ti+Al compound bond layer has a multi-sublayer structure and an overall composition of TiCNO or TiAlCNO.

9. 2. The coated cutting tool of claim 1, wherein the substrate consists of cemented carbide, cermet, ceramic, steel or cubic boron nitride, preferably cemented carbide.

10. The layer of hard coating is deposited by chemical vapor deposition (CVD), TiCN being a MT-TiCN layer deposited by MT-CVD at a reaction temperature in the range of 600° C. to 900° C., and / or Ti or Ti+Al compound bond layer deposited by HT-CVD at a reaction temperature in the range of 900° C. to 1200° C., and / or α-Al ２ O ３ The coated cutting tool of claim 1, wherein the layer is deposited by HT-CVD at a reaction temperature in the range of 900°C to 1200°C.

11. Use of a coated cutting tool according to any one of claims 1 to 10 for continuous and intermittent chip-forming machining, preferably turning operations, of ISO P or ISO K steel materials.

12. 11. A method for manufacturing a coated cutting tool according to any one of claims 1 to 10, wherein the multi-layer wear-resistant hard coating is deposited on a substrate by chemical vapor deposition (CVD), comprising the steps of: At least TiCl ４ , H ２ , N ２ and C.H. ３ depositing a multi-sublayer TiCN layer of a total of p alternating C-type and N-type sublayers, where p is an even or odd number ranging from 5 to 20, to a total thickness of 2 μm to 20 μm by MT-CVD at a reaction temperature ranging from 600° C. to 900° C. from a process gas composition comprising CN, and optionally HCl; The C-type and N-type sublayers have different stoichiometries with respect to the atomic ratio of carbon and nitrogen, the C-type TiCN sublayer has a C / N ratio in the range of 1.0≦C / N≦2.0, the N-type TiCN sublayer has a C / N ratio in the range of 0.5≦C / N<1.0, the difference in the C / N ratios of adjacent C-type and N-type layers being ≧0.2, and the C / N ratios are determined by the N in the process gas composition. ２ / CH ３ CN ratio, At least TiCl ４ , H ２ , N ２ , CO, and AlCl when Al is present. ３ , and optionally CH ４ and / or depositing a single or multi-sublayer oxygen-containing Ti or Ti+Al compound bond layer on the TiCN layer by thermal HT-CVD or MT-CVD from a process gas composition containing HCl to a total thickness of 0.5 μm to 3 μm; - a temperature in the range of 900 to 1200 ° C, a pressure in the range of 30 to 150 mbar, a time of 2 to 20 minutes, and H ２ , N ２ , 1 to 10 vol.% CO ２ and performing an oxidation step on the bonding layer in a gas atmosphere containing (consisting of) 1 to 20 vol. % CO; - HT-CVD at reaction temperatures ranging from 900°C to 1200°C to deposit α-Al with a total thickness of 2 μm to 15 μm on a bond layer treated with an oxidation step. ２ O ３ Depositing a layer A method comprising:

13. At least TiCl ４ , H ２ and N ２ 13. The method of claim 12, comprising depositing at least one underlayer of TiN or TiC immediately above the substrate surface by thermal HT-CVD or MT-CVD from a process gas composition comprising:

14. 13. The method of claim 12, wherein the Ti or Ti+Al compound bond layer is deposited by multiple subsequent deposition steps to obtain a multi-sublayer structure, each deposition step being performed by HT-CVD at a reaction temperature in the range of 900°C to 1200°C.

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