Coated cutting tools

Abstract

The present invention relates to a coated cutting tool comprising a cemented carbide base material and a coating, wherein the cemented carbide contains WC crystal grains and eta phase crystal grains and a metal binder, the metal binder contains Co, Cr, and Ti, the eta phase content in the cemented carbide is 1 to 10 volume%, the average crystal grain size of the eta phase crystal grains is 0.5 to 5 μm, and the coating thickness is 1 to 15 μm.

Description

【Technical Field】 【0001】 The present invention relates to a coated cutting tool. The cutting tool is coated with a wear-resistant coating, and the substrate is cemented carbide, which contains WC, eta phase, Co, Cr, and Ti. 【Background Art】 【0002】 Cemented carbide cutting tools for metal cutting applications are known in the art. Cemented carbide is a material containing a hard phase (usually a carbide, such as WC), and is usually bonded with a metal binder containing Co. The composition of the cemented carbide can be adjusted to meet specific requirements such as when the cutting tool is exposed to special types of materials or specific types of machining in machining. 【0003】 In some cutting applications, the requirements for the substrate are very high. In such applications, the substrate is prone to cracking, and the life of the cutting tool is limited. Examples of cutting applications with high requirements for the substrate include milling and turning of stainless steel and titanium alloys. These workpiece materials tend to adhere to and accumulate on the tool surface, forming a built-up edge, which may break if it is too large, and sometimes a part of the cutting edge may peel off. The cutting edge is further exposed to high temperatures during metal cutting with stainless steel and titanium alloys. 【0004】 It is known to add ruthenium (Ru) to the Co binder phase of cemented carbide, which is herein referred to as Ru-alloyed cemented carbide. This results in a cemented carbide substrate with improved resistance to thermal cracking, in which the cracks propagating to the substrate during the metal machining process are reduced. Thereby, the high-temperature properties of the cemented carbide are improved. The amount of Ru can vary depending on the application, and is usually within 5 to 25 weight percent (wt%) of the metal binder. 【0005】 Ru is a rare and extremely expensive raw material. Furthermore, recycling Ru as part of the recycling of cemented carbide materials is complex. There is a need to replace high-performance Ru alloy cemented carbides in metal cutting tools. 【0006】 The object of the present invention is to provide a coated cutting tool for metal cutting applications that has high-performance wear resistance similar to that of Ru alloy cemented carbide. A further object is to provide a coated cutting tool that exhibits high wear resistance when cutting stainless steel and titanium alloys. It is also an object to provide a cutting tool with a long service life for milling applications. 【0007】 Detailed explanation At least one of the above targets can be achieved by the cutting tool described in claim 1. Preferred embodiments are disclosed in the dependent claims. 【0008】 The present invention relates to a coated cutting tool comprising a cemented carbide base material and a coating, wherein the cemented carbide contains WC crystal grains and eta phase crystal grains and a metal binder, the metal binder contains Co, Cr, and Ti, the Co content in the cemented carbide is 6 to 16% by weight, the Cr / Co weight ratio in the cemented carbide is 2 to 12%, the Ti / Co weight ratio in the cemented carbide is 0.04 to 0.20%, the eta phase content in the cemented carbide is 1 to 10% by volume (vol%), the average grain size of the eta phase crystal grains is 0.5 to 5 μm, and the coating thickness is 1 to 15 μm. 【0009】 Surprisingly, the cutting tool according to the present invention was found to have similar performance and therefore be a viable alternative to Ru alloy cemented carbide cutting tools. 【0010】 The cutting tools disclosed herein may, for example, be inserts or end mills designed for milling applications. 【0011】 The cemented carbide of the present invention comprises WC crystal grains and eta phase crystal grains embedded in a metal binder. The metal binder contains Co, Cr, Ti, and W, the W being melted from the WC crystal grains into the metal binder during the sintering of the cemented carbide. 【0012】 In this context, "coating" in the context of cutting tools refers to a coating deposited on a cemented carbide substrate to enhance the wear resistance of the cutting tool. This coating may be, for example, a coating deposited by physical vapor deposition (PVD) or chemical vapor deposition (CVD). 【0013】 The Co content in the cemented carbide of this invention is 6 to 16% by weight. If the Co content is lower than 6% by weight, the toughness of the cutting tool will be lost. On the other hand, if the Co content is higher than 16% by weight, the cutting tool will lose comb crack resistance, and plastic deformation of the cutting edge will be more likely to occur. When the Co content is higher than 16% by weight, the cutting tool becomes sensitive to chemical attack by the cooling medium used in milling applications and the workpiece material during cutting. 【0014】 The eta phase content in the cemented carbide of the present invention is 1 to 10 volume percent. If the eta phase content is too high, most of the Co content in the metal binder will be consumed and become eta phase crystal grains, which will make the cemented carbide too brittle. If the eta phase content is too low, there is an increased risk that the eta phase crystal grains will form brittle clusters instead of well-dispersed eta crystal grains. 【0015】 In the cemented carbide of the present invention, the Cr content is such that the Cr(wt%) / Co(wt%) ratio is 2-12%. Surprisingly, it has been found that the properties of cutting tools are improved by the Cr content in the cemented carbide. When Cr is added to the cemented carbide, the crystal grains of the eta phase contain Cr. Cr also remains as a solid solution in the metal binder phase containing Co. Cr also acts as a grain growth inhibitor during sintering, continuously limiting the growth and coarsening of WC crystal grains. If the Cr content is too low, Cr still affects the grain size growth of WC crystal grains, but the solid solution is limited. If the Cr content is too high, undesirable Cr carbides (e.g., M7C3) may form, leading to embrittlement of the cemented carbide. Cemented carbides with a Cr content in the range of 2-12% Cr / Co weight ratio have high strength due to the solid solution effect. It is thought that the work hardening properties of Co are improved, as are the thermosetting properties, and the corrosion resistance (chemical resistance) is also thought to be improved by the Cr content of the present invention. Due to the Cr content of the present invention, the work hardening properties of Co are improved, the hot hardness properties are improved, and the chemical resistance, i.e., corrosion resistance, is also considered to be improved. 【0016】 The cemented carbide according to the present invention has a low carbon content as the formation of eta phase crystal grains increases. As a result, the cemented carbide has a W content in both the binder and the eta phase crystal grains. Here, the eta phase is defined as Me 12 This refers to carbides selected from C and Me6C, where Me is one or more metals selected from W and one or more metals of the binder phase, and thus the carbides are (W,Co,Cr)6C and / or (W,Co,Cr) 12 It could be C. 【0017】 In this invention, the cemented carbide contains finely dispersed eta phase crystal grains. Here, "finely dispersed" means that the microstructure of the cemented carbide is such that it can be seen as being 1 mm in size in an optical microscope image at 200x magnification. 2This means that within the area, there are no clusters greater than 8 or eta phase grains larger than 15 μm. Eta phase grains can be very large, brittle, and exist in undesirable shapes, and their grain size is typically greater than 50 μm, or even more than 100 μm, but these are not part of the present invention. The eta phase grains of the present invention have an average grain size of 0.5 to 5 μm, and these grains are uniformly distributed within the cemented carbide metal binder. The finely dispersed eta phase grains of the present invention are formed during the sintering process, in which carbon deficiency and equilibrium temperature must be controlled to achieve the claimed appearance and content of the eta phase. The difference between achieving undesirable large agglomerates of the eta phase and achieving the desired substoichiometric carbon content of the finely dispersed eta phase can be very small. To approach this limit, it is necessary to monitor the microstructure to ensure that undesirable large agglomerates are avoided. Carefully adjusting the carbon content and monitoring the results in terms of the resulting microstructure is a procedure known to those skilled in the art. 【0018】 Surprisingly, it was found that by combining the addition of a specific Cr content with the addition of a specific low level of Ti, favorable grain size and grain size distribution for the eta phase crystal grains could be obtained in cemented carbides containing a finely dispersed eta phase. Surprisingly, the presence of a specified small amount of Ti increased hardness while maintaining almost the same level of toughness. 【0019】 In one embodiment of the present invention, the cemented carbide comprises 75 to 91 volume% of WC, preferably 75 to 85 volume% or 80 to 87 volume% of WC. 【0020】 In one embodiment of the present invention, the cemented carbide contains WC grains and eta-phase grains in a metal binder of Co, Cr, and Ti, where a part of W is dissolved in the metal binder. During sintering, W inevitably dissolves in the metal binder, and its exact amount depends on a plurality of factors (such as the overall composition of the cemented carbide and the exact carbon content, etc.). 【0021】 In one embodiment of the present invention, the average WC particle size is 0.30 to 1.00 μm. The average WC particle size can be measured, for example, by image analysis. 【0022】 In one embodiment of the present invention, the Co content in the cemented carbide is 10 to 15% by weight, preferably 12 to 14% by weight. 【0023】 In one embodiment of the present invention, the Cr / Co weight ratio in the cemented carbide is 2% to 10%, preferably 2% to 4% or 8% to 10%. 【0024】 In one embodiment of the present invention, the Ti / Co weight ratio in the cemented carbide is 0.05% to 0.16%. 【0025】 In one embodiment of the present invention, the eta-phase content in the cemented carbide is 1 to 5% by volume, and preferably the Cr / Co weight ratio in the cemented carbide is 2% to 4%. 【0026】 In one embodiment of the present invention, the eta-phase content in the cemented carbide is 5 to 10% by volume, and preferably the Cr / Co weight ratio in the cemented carbide is 8% to 10%. 【0027】 In one embodiment of the present invention, the average particle size of the eta-phase grains is 0.5 to 3 μm, preferably 1 to 2 μm. 【0028】 In one embodiment of the present invention, the thickness of the coating is 2 to 10 μm. 【0029】 In one embodiment of the present invention, the average WC particle size is 0.40 to 0.95 μm. 【0030】 In one embodiment of the present invention, the content of the eta phase in the portion of the substrate adjacent to the substrate surface corresponds to the content of the eta phase in the innermost portion of the substrate. Therefore, the distribution of the eta phase is the same throughout the cemented carbide substrate. Here, it means that the cemented carbide does not contain an eta phase gradient or a zone without an eta phase, such as in U.S. Patent No. 4,843,039. 【0031】 In one embodiment of the present invention, the coating is a PVD coating. In one embodiment of the present invention, the PVD coating is a multilayer including TiAlN and Al2O3 sublayers. In one embodiment of the present invention, the PVD coating includes a lower TiAlN layer with a thickness of 1 to 3 μm, an Al2O3 layer with a thickness of 0.2 to 1 μm, a (TiAlN + Al2O3) multilayer with sublayer thicknesses of 0.1 to 0.2 μm for TiAlN and Al2O3, respectively, a TiAlN layer of 0.3 to 0.7 μm, and an outer layer of Al / Al2O3 / ZrN with sublayer thicknesses of 10 to 30 nm / 10 to 30 nm / 50 to 100 nm. 【0032】 In one embodiment of the present invention, the coating is a CVD coating. In one embodiment of the present invention, the coating is a CVD coating comprising a lower TiN layer with a thickness of 0.05 to 2 μm and a TiAlN layer with a thickness of 1 to 14 μm, and preferably the coating also comprises an upper TiN layer with a thickness of 0.05 to 2 μm. 【0033】 In one embodiment of the present invention, the coated cutting tool is a cutting tool insert, drill, or solid end mill for metal machining. 【0034】 In one embodiment of the present invention, a coated cutting tool comprises a cemented carbide base material and a coating, wherein the cemented carbide contains Co, Cr, Ti, and eta phase crystal grains, and the remainder is WC, the Co content in the cemented carbide is 6-16% by weight, the Cr / Co weight ratio in the cemented carbide is 2-4%, the Ti / Co weight ratio in the cemented carbide is 0.04% to 0.20%, the eta phase content in the cemented carbide is 1-5% by volume, the average grain size of the eta phase crystal grains is 0.5-3 μm, and the coating thickness is 1-15 μm. 【0035】 In one embodiment of the present invention, a coated cutting tool comprises a cemented carbide base material and a coating, wherein the cemented carbide contains WC crystal grains, eta phase crystal grains, and a metal binder, the metal binder contains Co, Cr, and Ti, the Co content in the cemented carbide is 6-16% by weight, the Cr / Co weight ratio in the cemented carbide is 2-4%, the Ti / Co weight ratio in the cemented carbide is 0.04%-0.20%, the eta phase content in the cemented carbide is 1-5% by volume, the average grain size of the eta phase crystal grains is 0.5-3 μm, and the coating thickness is 1-15 μm. 【0036】 In one embodiment of the present invention, the cemented carbide consists of 75-85 vol% WC crystal grains, 1-10 volume% eta phase crystal grains, and the remainder by volume% of metal binder. The area fraction in the image is considered to correspond to the volume fraction here. 【0037】 method The cemented carbide of the present invention is manufactured according to conventional cemented carbide manufacturing methods. Milling, drying, pressing, and sintering processes are used. 【0038】 To achieve the precise eta phase content, the carbon content needs to be adjusted during the manufacturing of the cemented carbide. 【0039】 The formation of uniformly or finely distributed eta phase crystal grains according to the present invention is achieved by carefully controlling the carbon content during the manufacture of cemented carbide. The cemented carbide according to the present invention has a substoichiometric carbon content within a specific range. Substoichiometric carbon is an indicator of carbon content relative to stoichiometric carbon content. 【0040】 The carbon content is appropriately such that the substoichiometric carbon content is between -0.40 and -0.16 wt%, preferably between -0.35 and -0.17 wt%. 【0041】 The stoichiometric carbon content can be calculated by assuming that the carbides in cemented carbides are perfectly stoichiometric, for example, by assuming an atomic ratio of W:C of 1:1. Since cemented carbides contain other carbide-forming elements (e.g., Cr), the corresponding carbide Cr3C2 is also assumed to be stoichiometric. 【0042】 This means that the term substoichiometric carbon, as used here, refers to the total carbon content in cemented carbide, which is determined by subtracting the stoichiometric carbon content, calculated from chemical analysis based on WC and other carbides that may be present in the cemented carbide. In sintered cemented carbide, this is as follows: [Carbon content] = [Stoichiometric carbon content] + [Substoichiometric carbon content] 【0043】 For example, if the stoichiometric carbon content of a particular cemented carbide is 5.60 wt%, and the substoichiometric carbon content of that cemented carbide is 5.30 wt%, then the substoichiometric carbon content will be -0.30 wt%. 【0044】 To achieve the precise carbon content in the final sintered cemented carbide production, W and / or W2C are added in the amount necessary to achieve the desired substoichiometric carbon content. The cemented carbide has a low carbon content to the extent that an eta phase is formed. However, the formed eta phase exists as fine grain sizes and is well distributed, rather than as large grains or aggregates. By carefully controlling the carbon balance during production, the desired morphology of the eta phase is provided. 【0045】 If the carbon content in sintered cemented carbide is too low, i.e., if the substoichiometric carbon content is lower than -0.40 wt%, the amount of the eta phase becomes too large, and the grain size increases considerably, making the cemented carbide brittle. On the other hand, if the carbon content is higher than the substoichiometric carbon content of -0.16 wt% and still in the eta phase formation region, the formed eta phase will be distributed non-uniformly in large aggregates, leading to a decrease in the toughness of the cemented carbide. 【0046】 The carbon content should be measured in sintered cemented carbide. This is because some carbon is lost during sintering, for example, due to the formation of CO2. The exact amount of carbon loss depends on the sintering furnace and process. Therefore, the powder will contain a slightly excess of carbon compared to the carbon targeted in the sintered cemented carbide. Typically, the substoichiometric carbon content in sintered material is about 5-25% lower than the substoichiometric carbon content in the powder composition. For example, if the substoichiometric carbon content in the powder composition is -0.20 wt%, the substoichiometric carbon content in the sintered material may range from about -0.21 wt% to about -0.25 wt%. The carbon content in sintered cemented carbide or powder can be measured, for example, by an instrument such as the LECO CS844. It is up to the art to adjust the addition of W and / or W2C to achieve the target eta content in the cemented carbide. 【0047】 The amount of the eta phase in cemented carbide was determined by LOM (optical microscope) image analysis at 2000x magnification. The area fraction in the image is considered to correspond to the volume fraction of the cemented carbide. The volume fraction of WC can be determined in a manner corresponding to the volume fraction of the eta phase. 【0048】 Here, the average grain size of WC crystal grains is measured using the Saltykov method on an image of the substrate cross-section. The test area is square and contains at least 50 crystal grains and a maximum of 100 crystal grains. At least 700 crystal grains should be defined as follows: In formula TIFF2026519048000002.tif16170, M is the magnification used, and A is the area of ​​the test square. intercepted This represents the number of crystal grains whose sides intersect (cross) the sides of the test square. Crystal grains that intersect at the corners of the test square are counted as one-quarter of a crystal grain. inside is the number of crystal grains that are entirely contained within the test square. Next, the average grain size d of WC. WC This can be determined as follows: TIFF2026519048000003.tif17170 【0049】 Here, the average grain size of the eta phase crystal grains is defined as the average value of the maximum Ferret diameter of the eta phase crystal grains. This value can be determined, for example, by image analysis of optical microscope (LOM) images. 【0050】 For example, the chemical composition of cemented carbide can be measured by chemical analysis using XRF (X-ray fluorescence) with a Panalytical Axios Max Advanced instrument. 【0051】 The layer thickness of the coating was measured in the polished cross-section using SEM imaging. 【0052】 The hardness and toughness of cemented carbide were measured using Vickers indentation. 【0053】 Embodiments of the invention will be described with reference to the attached drawings. [Brief explanation of the drawing] 【0054】 [Figure 1] A schematic diagram of one embodiment of the cutting tool (1) is shown, which has a geometric shape ADMT160608 comprising a rake face (2), a relief face (3), and a cutting edge (4). The cutting tool (1) is a milling insert in this embodiment. [Figure 2] Figure (1) shows a cutting tool having the geometric shape ROHX120. [Figure 3] The following are LOM (optical microscope) cross-sectional views of the samples further shown in the Examples section, showing LOM cross-sectional views of Reference Sample 1, b) Sample 1 according to the present invention, and c) Sample 2 according to the present invention. [Figure 4] The following are LOM (optical microscope) cross-sectional views of the samples further shown in the Examples section, showing LOM cross-sectional views of Reference Sample 2, b) Sample 3 according to the present invention, and c) Sample 4 according to the present invention. [Figure 5] The following are LOM (optical microscope) cross-sectional views of the samples further shown in the Examples section, showing LOM cross-sectional views of reference sample 3, b) sample 5 according to the present invention, and c) sample 6 according to the present invention. [Examples] 【0055】 The following describes exemplary embodiments of the present invention in more detail and compares them with reference examples. Coated cutting tools (inserts) were manufactured and analyzed and evaluated in cutting tests. 【0056】 Base material Two types of cemented carbide base materials were manufactured for milling inserts with different geometric shapes (ADMT160608R-F56 ​​and ROHX1204M0-F67). 【0057】 The cemented carbide was prepared from raw material powders according to Table 1. 【0058】 TIFF2026519048000004.tif68170 【0059】 The powder was ground in a ball mill with a grinding solution (water / ethanol ratio 9 / 91) and an organic binder (2 wt% PEG). The amount of PEG is not included in the dry powder weight shown in Table 1. After grinding, the slurry was dried. The dried aggregate was pressed to form a green body. This green body was sintered at 1410°C in Ar and CO at 40 mbar. 【0060】 The average ethode phase content was determined by counting the area of ​​LOM (optical microscope) images taken at 2000x magnification using ImageJ software, with the "Analyze particles" function combined with "include holes" and "0-Infinity" filter settings. Before measurement, the images were converted to 8-bit grayscale images using automatic thresholding. The area percentage was assumed to correspond to the volume fraction in the sample. The average values ​​from 10 images are shown in Table 2. 【0061】 Here, the average grain size of the eta phase crystal grains is calculated using the same software as the average maximum Ferret diameter of the eta crystal grains. When measuring the maximum Ferret diameter, the "0.01-Infinity" and "exclude on edges" filters were further activated in the "particle analysis" function, and only images at a magnification of 2000x were used. Before measurement, the images were converted to 8-bit grayscale images using automatic thresholding. The average values ​​from the six images are shown in Table 2. 【0062】 The substoichiometric carbon content in sintered cemented carbide was first calculated by measuring the total carbon content using a LECO CS844 instrument. The sample was pulverized before analysis for this purpose. The accuracy of the values ​​is ±0.01 wt%. The W, Co, and Cr content was measured using XRF (X-ray fluorescence) with a Panalytical Axios Max Advanced instrument. The W content, used to calculate the stoichiometric carbon content, is obtained by subtracting the amounts of cobalt, chromium, and carbon from the total weight of the sample (assuming a 1:1 ratio for W and C). The substoichiometric carbon value is obtained by subtracting the stoichiometric carbon content from the total carbon measured by the LECO CS844 instrument. The substoichiometric carbon value of sintered material differs from that of powder. This is because during sintering, some carbon reacts with oxygen and exhaust gases to form CO or CO2, reducing the final C content of the cemented carbide. The carbon content in the powder was adjusted to obtain the desired microstructure in the sintered cemented carbide. 【0063】 The ethta phase content and the average grain size of the ethta phase grains were measured according to the methods disclosed herein (see Table 2). In the samples containing the ethta phase, the ethta phase grains were uniformly distributed throughout the substrate, and no gradient of ethta phase component was observed in these samples. No gamma phase grains, very large ethta phase grains, or graphite were found in the cemented carbide. 【0064】 Table 2 shows the average grain size, eta phase grain size, and volume fraction of the eta phase for sintered cemented carbide. 【0065】 TIFF2026519048000005.tif73170 【0066】 Hardness and toughness were measured according to the previously disclosed method, and the achieved values ​​are shown in Table 3. 【0067】 TIFF2026519048000006.tif60170 【0068】 The sample according to the present invention was shown to have higher hardness compared to the reference sample. The K1C level of the sample according to the present invention was lower than that of the reference sample, but all samples had a high K1C level. 【0069】 TiAlN / Al2O3 multilayer PVD coating Samples of Invention 1, Invention 2, Invention 3, Invention 4, Reference 1, and Reference 2 were formed by coating substrates 1A, 1B, 2A, 2B, and 3 using a PVD process. A similar PVD coating is disclosed in European Patent Application No. 1762637 (EP1762637A2). 【0070】 This is the first inner layer of TiAlN, 2 μm thick, with an Al:Ti ratio of 67:33. The crystal structure is mainly cubic, with only trace amounts of hexagonal AlN phase. 【0071】 Subsequently, a nanocrystalline γ-Al2O3 layer with a thickness of 0.5 μm is formed. 【0072】 A 0.7 μm thick multilayer is arranged on top of the γ-Al2O3 layer, and this multilayer consists of a series of TiAlN / γ-Al2O3 / TiAlN / γ-Al2O3 layers. The atomic ratio of TiAlN is Al:Ti 67:33. All four layers have approximately the same thickness, about 0.175 μm each. 【0073】 Subsequently, a TiAlN layer with a thickness of 0.55 μm was added, with an Al:Ti atomic ratio of 67:33. 【0074】 Finally, the outermost sublayer of the Al / Al2O3 / ZrN layer sequence is deposited with sublayer thicknesses of 20nm / 20nm / 80nm. 【0075】 The total thickness of the PVD coating measured on the relief surface of the cutting tool was approximately 4 μm. 【0076】 Sample 1 of the present invention, Sample 2 of the present invention, and Reference Sample 1 were formed from substrates 1A, 2A, and 3 having a geometric shape ADMT160608R-F56 ​​on which a PVD coating was deposited. 【0077】 Sample 3 of the present invention, Sample 4 of the present invention, and Reference Sample 2 were formed from substrates 1A, 2A, and 3 having a geometric shape ROHX1204M0-F67 on which a PVD coating was deposited. 【0078】 TiN / TiAlN / TiN CVD coating Sample 5, Sample 6, and Reference Sample 3 of the present invention were formed by coating substrates 1A, 2A, and 3 having the geometric shape ROHX1204M0-F67 using a CVD process. A similar CVD coating is disclosed in international patent application WO2017 / 0216826. 【0079】 First, an inner layer, which is a TiN layer approximately 0.7 μm thick, was deposited at 850°C. 【0080】 Subsequently, a TiAlN layer was deposited at approximately 700°C. The thickness of the TiAlN layer was approximately 8 μm. 【0081】 Subsequently, the prepared cutting inserts were subjected to heat treatment for a certain period of time. The temperature was raised to 850°C. After 10 minutes of temperature stabilization, a 0.3 μm top layer of TiN was deposited. The total heat treatment time at 850°C (including the deposition of the top TiN layer) was 3 hours and 12 minutes. 【0082】 Table 4 shows an overview of the coated samples. 【0083】 TIFF2026519048000007.tif80170 【0084】 The coated samples were evaluated using a cutting test. 【0085】 Performance testing To determine the performance of the sample shown above, a cutting test was performed. 【0086】 The following are expressions / terms commonly used in metal cutting: Vc (m / min): Cutting speed per minute (meters) fz (mm / tooth): Feed rate per tooth (in millimeters, for milling) z: (number): Number of teeth in the cutter ae (mm): Cutting radius depth (millimeters) ap (mm): Axial depth of cutting (millimeters) 【0087】 Cutting Test 1 A cutting tool with geometric shape ADMT160608R-F56 ​​was tested in a shoulder milling operation on a high-strength titanium alloy Ti6Al4V workpiece. The cutting speed (Vc) was 40 m / min, the feed rate (fZ) was 0.12 mm / tooth, the number of cutter teeth (z) was 4, the axial cutting depth (ap) was 2.0 mm, and the radial cutting depth (ae) was 18.0 mm. A water-miscible cutting fluid was used. Machining continued until the end of the tool life criterion was reached. The tool life criterion was set to a wear width on the rake face of the main cutting edge: Vbmax > 0.3 mm. A specified interval was used to evaluate tool wear. The average results of four parallel cutting tests are shown in Table 5 for each sample type. 【0088】 TIFF2026519048000008.tif58170 【0089】 For samples 1 and 2 of the present invention, the wear width of the rake face of the cutting tool was significantly smaller compared to reference sample 1, which contains ruthenium. 【0090】 Cutting Test 2 The cutting tool ROHX1204M0-F67 (round insert) was tested in a turbine blade milling operation using a heat-resistant stainless steel rectangular bar (100 × 60 × 400 mm) workpiece. The cutting speed (vC) was 240 m / min, the feed rate (fZ) was 0.3 mm / tooth, the number of cutter teeth (z) was 5, the axial cutting depth (ap) was 3.0 mm, and the radial cutting depth (ae) was 32.0 mm. No cutting fluid was used. Machining continued until the end of the tool life criterion was reached. The tool life criterion was set to a wear width of the rake face of the main cutting edge: Vbmax > 0.5 mm. Specified intervals were used to evaluate tool wear and the number of cuts at Vbmax. The average results of 5 parallel cutting tests for each sample type are shown in Table 6. 【0091】 TIFF2026519048000009.tif71170 【0092】 The PVD-coated cutting tools of samples 3 and 4 of the present invention showed significantly higher cutting cycles, tool life, and total chip volume compared to reference sample 2, which contained Ru. 【0093】 The number of cuts, tool life, and total chip volume for the CVD-coated cutting tools 5 and 6 of the present invention were at a comparablely high level compared to the reference sample 3 containing Ru.

Claims

[Claim 1] A coated cutting tool (1) comprising a cemented carbide base material and a coating, wherein the cemented carbide contains WC crystal grains and finely dispersed eta phase crystal grains and a metal binder, the metal binder contains Co, Cr, and Ti, the Co content in the cemented carbide is 6 to 16% by weight, the Cr / Co weight ratio in the cemented carbide is 2% to 12%, the Ti / Co weight ratio in the cemented carbide is 0.04% to 0.20%, the eta phase content in the cemented carbide is 1 to 10% by volume, the average crystal grain size of the eta phase crystal grains is 0.5 to 5 μm, and the thickness of the coating is 1 to 15 μm. [Claim 2] A coated cutting tool according to claim 1, wherein the average WC grain size is 0.30 to 1.00 μm. [Claim 3] A coated cutting tool according to claim 1 or 2, wherein the Co content in the cemented carbide is 10 to 15% by weight, preferably 12 to 14% by weight. [Claim 4] A coated cutting tool according to any one of claims 1 to 3, wherein the Cr / Co weight ratio in the cemented carbide is 2% to 10%, preferably 2% to 4% or 8% to 10%. [Claim 5] A coated cutting tool according to any one of claims 1 to 4, wherein the Ti / Co weight ratio in the cemented carbide is 0.05% to 0.16%. [Claim 6] A coated cutting tool according to any one of claims 1 to 5, wherein the average grain size of the ethode phase crystal grains is 1 to 2 μm. [Claim 7] A coated cutting tool according to any one of claims 1 to 6, wherein the thickness of the coating is 2 to 10 μm. [Claim 8] A coated cutting tool according to any one of claims 1 to 7, wherein the average WC grain size is 0.40 to 0.95 μm. [Claim 9] A coated cutting tool according to any one of claims 1 to 8, wherein the content of the eta phase in the portion of the substrate adjacent to the surface of the substrate is equivalent to the content of the eta phase in the innermost portion of the substrate. [Claim 10] A coated cutting tool according to any one of claims 1 to 9, wherein the coating is a PVD coating. [Claim 11] A coated cutting tool according to claim 10, wherein the PVD coating is a multilayer comprising a TiAlN sublayer and an alumina sublayer. [Claim 12] The coating consists of a bottom TiAl layer with a thickness of 1-3 μm and an Al layer with a thickness of 0.2-1 μm. ２ O ３ layer, (TiAl+Al ２ O ３ ) is a multilayer, with sublayers of TiAl and Al ２ O ３ The materials consist of a multilayer with a thickness of 0.1–0.2 μm, a TiAlN layer with a thickness of 0.3–0.7 μm, and an Al / Al layer, respectively. ２ O ３ A coated cutting tool according to claim 10 or 11, comprising an outer layer of a layer sequence of ZrN, wherein the thickness of the sublayers is 10-30 nm / 10-30 nm / 50-100 nm. [Claim 13] A coated cutting tool according to any one of claims 1 to 12, wherein the coating is a CVD coating. [Claim 14] A coated cutting tool according to claim 13, wherein the coating comprises a lower TiN layer with a thickness of 0.05 to 2 μm and a TiAlN layer with a thickness of 1 to 14 μm, and preferably the coating also comprises an upper TiN layer with a thickness of 0.05 to 2 μm. [Claim 15] The coated cutting tool (1) according to any one of claims 1 to 14, wherein the coated cutting tool (1) is a cutting tool insert, drill, or solid end mill for metal machining.

Images