Coated cutting tools

Abstract

The present invention relates to a coated cutting tool comprising a coating and a cemented carbide substrate, wherein the cemented carbide comprises WC and a Ni-based metal binder, wherein the metal binder comprises Ni, Fe and Cr such that the weight ratio Ni / (Ni+Fe) is between 0.68 and 0.8; and the Cr content in the cemented carbide is such that the weight ratio Cr / (Cr+Ni+Fe) is between 0.03 and 0.12, and wherein the thickness of the coating is between 2 and 25 µm.

Description

[0001] The present invention relates to a coated cutting tool comprising a cemented carbide substrate having a Ni-based metal binder comprising Ni, Fe and Cr. Background Technology

[0002] In the market for cutting tools that perform chip-forming metal cutting operations, CVD (chemical vapor deposition) and PVD (physical vapor deposition) coated cemented carbide dominates, with cemented carbide typically made from WC in a Co metal binder.

[0003] In recent years, efforts have been made to replace cobalt due to its hazardous nature and status as a critical raw material. This has spurred increased activity in developing binders with reduced or no cobalt content. Nevertheless, products with reduced or even no cobalt content in the metal binder market remain rare or nonexistent. Several factors contribute to this, one of which is the difficulty in achieving matrix properties that match those of cemented carbides with cobalt binders. Scaling up the production of these new cemented carbides is also extremely challenging.

[0004] Other reasons include the difficulty in using known coating techniques and post-processing when replacing Co. This is especially true in chemical vapor deposition processes using reactive gases at high temperatures, where interactions occur between the gas phase and the hard alloy.

[0005] Among alternative metal binders, mixtures of Ni and Fe are promising candidates due to their mechanical properties. From the perspective of the mechanical properties of cemented carbides, a relatively high Ni / Fe ratio is preferred. However, such a high Ni content can lead to degradation in coatings such as CVD (chemical vapor deposition) coatings, as Ni diffuses extensively into the coating, causing deterioration. Reducing the Ni content in the metal binder can help maintain coating performance but will decrease the properties of the substrate, such as toughness and hardness.

[0006] Cr is a known additive for cemented carbide, which can help control the grain growth of WC grains and improve corrosion resistance. However, when using Co binders, adding Cr to the matrix composition can also have a negative impact on CVD coatings.

[0007] One object of the present invention is to provide a coated cutting tool for metal cutting, the coated cutting tool having a cemented carbide matrix using a Ni-based binder, the performance of which is equal to or better than that of using Co as a binder. Detailed Implementation

[0008] This invention relates to a coated cutting tool comprising a coating and a cemented carbide substrate, wherein the cemented carbide comprises a WC and a Ni-based metal binder. The metal binder comprises Ni, Fe, and Cr, such that: The weight ratio of Ni / (Ni+Fe) in cemented carbide is between 0.68 and 0.8; and The Cr content in cemented carbide results in a weight ratio of Cr / (Cr+Ni+Fe) between 0.03 and 0.12; and The thickness of the coating ranges from 2 to 25 µm.

[0009] In this article, cemented carbide refers to a hard phase in which at least 50% by weight is WC. The hard phase in this article refers to all phases other than the metallic binder phase.

[0010] Ni-based metal binders primarily consist of Ni, Fe, and Cr, which in this document means that the binder comprises at least 90% by weight of Ni, Fe, and Cr. In this document, Ni-based binders refer to binders containing at least 60% by weight of Ni.

[0011] The amount of the metal binder is 2 to 20% by weight of the sintered cemented carbide, preferably 5 to 12% by weight. Although the main elements in the binder are Ni, Fe, and Cr, as is well known in the cemented carbide manufacturing industry, other elements (such as W from WC) are also present in the metal binder because they inevitably dissolve in the metal binder during sintering. If other common additives (such as cubic carbides) are added, elements such as Ti, Nb, Ta, and V may also be found in the metal binder.

[0012] The cemented carbide according to the invention comprises Ni and Fe in amounts such that the weight ratio Ni / (Ni+Fe) is between 0.68 and 0.8, preferably between 0.70 and 0.74, and more preferably between 0.71 and 0.74. If the Ni content is too high, there is a risk that any coating deposited on the substrate will deteriorate in terms of microstructural characteristics (grain size, grain morphology, crystal orientation), resulting in a complete loss of physical and mechanical properties. If the Ni content is too low, the mechanical properties of the substrate, such as hardness and toughness, will be insufficient, and the overall performance of the cutting tool will also be poor.

[0013] Cr is frequently added to cemented carbides, but the amount of Cr added is often limited by its solubility in the metal binder. If the amount of Cr exceeds its solubility in the binder, brittle carbides Cr7C3 will precipitate in the microstructure, and the mechanical properties of the cemented carbides will deteriorate.

[0014] Add Cr until the limit for forming Cr7C3 is reached, but for practical reasons, it is not advisable to approach this limit too closely. A suitable weight fraction of Cr / (Cr+Ni+Fe) is between 0.03 and 0.12, preferably between 0.035 and 0.095.

[0015] If the amount of Cr is too low, the hardness and other mechanical properties will be insufficient.

[0016] The cemented carbide according to the invention is substantially free of Co. This means herein that no Co powder is added. However, if the same manufacturing equipment was used when manufacturing the Co-containing cemented carbide, and / or if the grinding media is made of the Co-containing cemented carbide, a small amount of Co may be present due to contamination. "Substantially free of Co" herein means that the Co content in the cemented carbide is less than 1% by weight, preferably less than 0.5% by weight. The Co content is measured according to standard practice when chemically analyzing the cemented carbide.

[0017] The cemented carbide according to the invention can have any average WC grain size known to cutting tools. Preferably, the average WC grain size, measured by the linear intercept method, is between 0.1 and 12 µm, more preferably between 0.4 and 9 µm. However, the specific average WC grain size is selected according to the specific cutting application.

[0018] The carbon content in the sintered cemented carbide should be selected so that neither the η phase nor free graphite exists in the microstructure. If the carbon content is too low, the η phase may form. If the carbon content is too high, graphite may form in the material. Methods for adjusting the carbon balance to achieve this are well-known to those skilled in the art of cemented carbide manufacturing.

[0019] In one embodiment of the invention, the cemented carbide comprises a γ phase (sometimes also referred to as a cubic phase). If one or more γ phase-forming elements (e.g., Ti, Ta, Nb, Zr, V, Mo, Cr, Hf) are present, a γ phase will be formed during sintering, with the general formula (W,X)(C,N) or (W,X)(C), where X can be one or more γ phase-forming elements. The amount of the γ phase is suitably 1 to 20% by volume, preferably 2 to 7% by volume. This can be measured in various ways, preferably by image analysis (e.g., using ImageJ) of optical microscopy (LOM) images or scanning electron microscopy (SEM) photographs of the matrix cross-section. When the surface region of the cemented carbide is provided with a gradient, the amount of the γ phase described herein is measured in bulk.

[0020] In one embodiment of the invention, when the cemented carbide contains a γ phase, the cemented carbide may contain a surface region rich in a binder phase that does not contain a γ phase.

[0021] The thickness of the surface region is preferably 5 to 35 µm. This thickness is measured between the matrix surface and the boundary between the γ-phase-containing bulk and the γ-phase-reduced surface region. This boundary is easily identifiable in SEM or LOM images because it is quite obvious. The surface region thickness measurement should preferably be performed on a flat surface, preferably on the flank face, and not too close to the cutting edge. In this context, this means the measurement should be performed at least 0.3 mm from the cutting edge.

[0022] In this paper, enriched binder refers to a binder phase content in the surface region that is at least 1.3 times that in the bulk binder phase. The binder phase content in the surface region should be measured at half the total thickness / depth of the surface region. In this paper, "bulk" refers to areas that are not part of the surface region. All measurements of the bulk should be performed in areas not too close to the surface region. This means that any measurements of the bulk microstructure should be performed at a depth of at least 200 µm from the surface.

[0023] In this article, γ phase reduction refers to the absence or minimal presence of γ phase particles in the surface region, i.e., less than 0.5% of the area.

[0024] In one embodiment of the present invention, the coating is a CVD coating.

[0025] In one embodiment of the present invention, the coating comprises one or more layers selected from TiN, TiCN, AlTiN, ZrCN, TiB2, and Al2O3, or multiple layers comprising α-Al2O3 and / or κ-Al2O3.

[0026] In one embodiment of the invention, the coating comprises an inner TiN layer, preferably having a thickness of 0.3-1 µm.

[0027] In one embodiment of the invention, the coating comprises a TiCN layer, preferably having a thickness of 6-12 µm.

[0028] In one embodiment of the invention, the TiCN layer exhibits a texture coefficient TC(hkl) as defined by Harris formula (1), as measured by X-ray diffraction using CuKα radiation and θ-2θ scanning:

[0029] Where I(hkl) is the measured intensity (integrated area) of the reflection of (hkl), I0(hkl) is the standard intensity according to ICDD PDF card No. 42-1489, n is the number of reflections, and the reflections used in the calculation are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0), (4 2 2) and (5 1 1), where TC(4 2 2)≥4.

[0030] In one embodiment of the present invention, the coating comprises an α-Al2O3 layer, preferably having a thickness of 4-8 µm.

[0031] In one embodiment of the invention, the α-Al2O3 layer exhibits a texture coefficient TC(hkl) defined according to Harris formula (1), measured by X-ray diffraction using CuKα radiation and θ-2θ scanning, where I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, I0(hkl) is the standard intensity according to ICDD PDF card No. 00-010-0173, n is the number of reflections used in the calculation, and the (hkl) reflections used are (1 0 4), (1 1 0), (1 1 3), (0 24), (1 1 6), (2 1 4), (3 0 0), and (0 0 12), characterized in that TC(0 0 12) ≥ 6, preferably ≥ 7.

[0032] In one embodiment of the invention, the coated cutting tool comprises a substrate containing a WC and a Ni-based metal binder, wherein the weight ratio of Ni / (Ni+Fe) is between 0.70 and 0.72; and the Cr content in the cemented carbide results in a weight ratio of Cr / (Cr+Ni+Fe) between 0.075 and 0.095.

[0033] In one embodiment of the invention, the coated cutting tool comprises a substrate containing a WC and a Ni-based metal binder, wherein the weight ratio of Ni / (Ni+Fe) is between 0.70 and 0.72; and the Cr content in the cemented carbide results in a weight ratio of Cr / (Cr+Ni+Fe) between 0.035 and 0.05.

[0034] In one embodiment of the invention, the coated cutting tool comprises a substrate containing a WC and a Ni-based metal binder, wherein the weight ratio of Ni / (Ni+Fe) is between 0.73 and 0.75; and the Cr content in the cemented carbide results in a weight ratio of Cr / (Cr+Ni+Fe) between 0.075 and 0.095.

[0035] In one embodiment of the invention, the coated cutting tool comprises a substrate containing a WC and a Ni-based metal binder, wherein the weight ratio of Ni / (Ni+Fe) is between 0.73 and 0.75; and the Cr content in the cemented carbide results in a weight ratio of Cr / (Cr+Ni+Fe) between 0.035 and 0.05.

[0036] In one embodiment of the invention, the coated cutting tool comprises a substrate containing a WC and a Ni-based metal binder, wherein the weight ratio of Ni / (Ni+Fe) is between 0.73 and 0.75; and the Cr content in the cemented carbide results in a weight ratio of Cr / (Cr+Ni+Fe) between 0.045 and 0.065.

[0037] In one embodiment of the invention, the coated cutting tool comprises a substrate containing a WC and a Ni-based metal binder, wherein the weight ratio of Ni / (Ni+Fe) is between 0.73 and 0.75; and the Cr content in the cemented carbide results in a weight ratio of Cr / (Cr+Ni+Fe) between 0.065 and 0.075.

[0038] In this article, cutting tools refer to inserts, end mills, or drills.

[0039] In one embodiment of the present invention, the cutting tool is an insert, preferably a turning insert.

[0040] In one embodiment of the invention, the cemented carbide matrix is ​​used for turning steel.

[0041] The present invention also relates to a method for manufacturing the above-described cutting tool.

[0042] The method includes the following steps: - Provides WC powder; - Provides powders containing the elements Fe, Ni, and Cr; - The powder is mixed with a grinding liquid to form a slurry, and the slurry is dried into particles. - The particles are pressed and sintered into a sintered hard alloy matrix; The coating is deposited onto the substrate using chemical vapor deposition at a deposition temperature of at least 800°C.

[0043] Raw materials containing Fe, Ni, and Cr can be added as pure metals, alloys of two or more metals, or their carbides, nitrides, or carbonitrides. The amount of raw materials added should be such that the sintered binder phase has the composition described above.

[0044] In one embodiment of the present invention, the powder is Cr3C2, Fe and Ni.

[0045] The average grain size of the WC powder used is preferably 0.2-10 µm, more preferably 0.2-5 µm (FSSS).

[0046] In one embodiment of the invention, when a γ phase is required, a powder comprising one or more of Ti, Ta, Nb, Zr, V, Mo, Cr, and Hf, a carbide, a nitride, or a carbonitride is added to form a γ phase during sintering. When a γ phase-free enriched binder phase surface region is required, at least one γ phase forming powder is a nitride or a carbonitride.

[0047] Any liquid commonly used as a polishing slurry in conventional cemented carbide manufacturing can be used. The polishing slurry is preferably water, alcohol, or an organic solvent, more preferably water or a mixture of water and alcohol, and most preferably a mixture of water and ethanol. The properties of the slurry depend on the amount of polishing slurry added. Since drying the slurry requires energy, the amount of liquid should be minimized to maintain low cost. However, sufficient liquid needs to be added to achieve a pumpable slurry and avoid system blockage. In addition, other compounds known in the art, such as dispersants and pH adjusters, can be added to the slurry.

[0048] An organic binder may also be optionally added to the slurry to promote granulation during subsequent spray drying operations and to act as a pressing aid in any subsequent pressing and sintering operations. The organic binder can be any binder commonly used in the art. For example, an organic binder can be paraffin wax, polyethylene glycol (PEG), long-chain fatty acids, etc. The amount of organic binder is suitably between 15 and 25% by volume based on the total dry powder volume, and the amount of organic binder is not included in the total dry powder volume.

[0049] A slurry comprising powders forming a hard component and powders forming a binder phase (and possibly an organic binder) is suitably mixed by a grinding operation in a ball mill or a vertical ball mill. The grinding is preferably performed first to form a slurry comprising a metallic binder powder, first and second powder components (and possibly an organic binder). The slurry is then suitably ground in a ball mill or a vertical ball mill to obtain a homogeneous slurry blend.

[0050] A slurry containing a powdered material (and possibly an organic binder) mixed with an organic liquid is atomized through a suitable nozzle into a drying tower, where small droplets are instantaneously dried by a hot gas stream (e.g., nitrogen stream) to form aggregated particles. For small-scale experiments, other drying methods, such as disc drying, can also be used.

[0051] Subsequently, the dried powder / granules are formed into a green body through pressing operations (such as uniaxial pressing, multiaxial pressing, etc.).

[0052] According to the present invention, a green body formed from powder / particles is manufactured and then sintered according to any conventional sintering method, such as vacuum sintering, sintering HIP, spark plasma sintering, gas pressure sintering (GPS), etc.

[0053] In one embodiment of the present invention, the sintering temperature is between 1350 and 1550°C.

[0054] In one embodiment of the invention, the sintering process includes a sintering HIP step, which is carried out at a temperature between 1350 and 1550°C and a pressure of at least 40 bar (preferably between 40 and 80 bar). Attached Figure Description

[0055] Figure 1 SEM images of the top surface of the Al2O3 layer of Invention 1 are shown.

[0056] Figure 2 A SEM image of the substrate / coating interface cross-section of Invention 1 is shown, revealing the innermost TiN and TiCN layers.

[0057] Figure 3 SEM images of the top surface of the Al2O3 layer of Invention 3 are shown.

[0058] Figure 4 The image shows a cross-sectional SEM image of the substrate / coating interface of Invention 3, revealing the innermost TiN and TiCN layers.

[0059] Figure 5 SEM images of the top surface of the Al2O3 layer of Invention 4 are shown.

[0060] Figure 6 A SEM image of the substrate / coating interface cross-section of Invention 4 is shown, revealing the innermost TiN and TiCN layers.

[0061] Figure 7 SEM images of the top surface of the Al2O3 layer of Invention 5 are shown.

[0062] Figure 8 The image shows a cross-sectional SEM image of the substrate / coating interface of Invention 5, revealing the innermost TiN and TiCN layers.

[0063] Figure 9 SEM images of the top surface of the Al2O3 layer of Invention 6 are shown.

[0064] Figure 10 The image shows a cross-sectional SEM image of the substrate / coating interface of Invention 6, revealing the innermost TiN and TiCN layers.

[0065] Figure 11 The SEM image of the top surface of the Al2O3 layer in Comparison 1 is shown.

[0066] Figure 12SEM images of the substrate / coating interface cross-section of Comparison 1 are shown, revealing the innermost TiN and TiCN layers.

[0067] Figure 13 The image shows a SEM image of the top surface of the Al2O3 layer in Comparison 2.

[0068] Figure 14 The image shows a SEM image of the top surface of the Al2O3 layer in Comparison 3.

[0069] Example 1

[0070] Square cemented carbide matrix was manufactured using the powder composition given in Table 1.

[0071] Table 1

[0072] The average particle size (FSSS) of the WC powder was 0.8 µm. Carbon balance was adjusted by adding carbon to avoid η-phase and graphite formation. The raw material powder was ball-milled for 8 hours with an organic binder (PEG based on 2 wt% of total powder weight) and a grinding slurry (water / ethanol) to form a slurry. The slurry was then dried and ground in an agate mortar to obtain a powder blend. This powder was pressed into green bodies. The green bodies were sintered in a HIP (hot isostatic pressing) furnace at a maximum sintering temperature of 1450 °C under a vacuum of 40 mbar for 1 hour, followed by a 15-minute high-pressure step at 50 bar to reduce the porosity of the sample.

[0073] After sintering, one side of the cemented carbide substrate was polished before the coating process.

[0074] For comparison, a CVD coating was also deposited on a commercial substrate using Co as a binder. This sample is referred to as Comparison 3 in this paper.

[0075] Subsequently, the sintered substrate was coated using CVD coating deposition in a radial Ionbond Bernex™ CVD system (Model 530, capable of accommodating 10,000 half-inch cutting blades). Samples for further testing and analysis were selected from the middle of the reaction chamber, located between the center and edge of the disk, at half the disk's radius. CVD coatings were deposited on the cemented carbide composition presented above, and the layers are summarized in Table 2.

[0076] Table 2. Layers of the deposited coating

[0077] Before starting CVD deposition, the CVD chamber is heated to 885°C. A preheating step is performed at 200 mbar: 100 vol% N2 is used when heating from room temperature to 600°C, and 100 vol% H2 is used when heating from 600°C to 885°C.

[0078] First, a TiN layer of approximately 0.4 µm thickness was deposited on the substrate at 885 °C.

[0079] Subsequently, an approximately 8 µm thick TiCN layer was deposited at 885 °C using the well-known MTCVD technique, employing TiCl4, CH3CN, N2, HCl, and H2. In the initial stage of MTCVD deposition of the TiCN layer, the TiCl4 / CH3CN volume ratio was 6.6, and in subsequent stages, the TiCl4 / CH3CN volume ratio was 3.7. Detailed information on the TiN and TiCN deposition is shown in Table 3.

[0080] Table 3. MTCVD of TiN and TiCN

[0081] After the TiCN outer layer was deposited, the temperature was increased from 885°C to 1000°C in an atmosphere of 75 vol% H2 and 25 vol% N2.

[0082] A bonding layer approximately 1 µm thick was deposited on top of the MTCVD TiCN layer at 1000 °C. This deposition process consisted of four independent reaction steps. First, the MTCVD TiCN step was performed at 400 mbar using TiCl4, CH4, N2, HCl, and H2. Then, the second step (TiCNO-1) was performed at 70 mbar using TiCl4, CH3CN, CO, N2, and H2. Next, the third step (TiCNO-2) was performed at 70 mbar using TiCl4, CH3CN, CO, N2, and H2. Finally, the fourth step (TiN) was performed at 70 mbar using TiCl4, N2, and H2. During the third deposition step, some of the gas was continuously varied, as shown in Table 4 as the first initial level and the second termination level. Before the subsequent Al2O3 nucleation began, the bonding layer was oxidized for 4 minutes in a mixed gas of CO2, CO, N2, and H2.

[0083] Detailed information on the deposition of the bonding layer is shown in Table 4.

[0084] Table 4. Deposition of the bonding layer

[0085] The α-Al₂O₃ layer was deposited in two steps at 1000 °C and 55 mbar. The first step used 1.2 vol% AlCl₃, 4.7 vol% CO₂, 1.8 vol% HCl and the balance H₂ to obtain an α-Al₂O₃ layer of approximately 0.1 µm. The second step used 1.16% AlCl₃, 4.65% CO₂, 2.91% HCl, 0.58% H₂S and the balance H₂ to obtain an α-Al₂O₃ layer with a total thickness of approximately 5 µm.

[0086] To investigate the texture of the layers, X-ray diffraction was performed on the polished sintered surface of the coated substrate using an Xpert-Pro Malvern Panalytical diffractometer system equipped with an X'Celerator detector. The coated substrate was mounted in a sample holder, ensuring its surface was parallel to the reference plane of the holder and at an appropriate height. Measurements were performed using a Cu-Kα radiation source (1.54 Å) at 45 kV and 40 mA. A 0.04 radian Solar slit was used for the incident beam. A 1 / 16 degree divergence slit was used for the diffracted beam. The nickel β-filter was 0.020 mm thick. The diffraction intensity of the coated cutting tool was measured within the range of 15° to 140° 2θ (i.e., the incident angle θ ranged from 10° to 70°).

[0087] Data analysis was performed using PANalytical's X'Pert HighScore Plus software, including background subtraction and Cu-K. α2 Subtraction and data profile fitting. The general description of the fitting is as follows. Then, using the output of the program (the integral peak area of ​​the profile fitting curve), the texture coefficient of the layer is calculated by comparing the measured intensity data with the standard intensity data of the α-Al2O3 PDF card and using the Harris formula (1) disclosed below. Due to the finite layer thickness, the relative intensity of a pair of peaks at different 2θ angles differs from that of the bulk sample due to the different path lengths through the layer. Therefore, when calculating the TC value, a thin film correction is applied to the integral peak area intensity of the extracted profile fitting curve, and the linear absorption coefficient of the layer is also considered.

[0088] Since other layers that may exist above the α-Al₂O₃ layer can affect the X-ray intensity entering the α-Al₂O₃ layer and penetrating the entire coating, these coatings also need to be corrected, taking into account the linear absorption coefficients of the corresponding compounds in each layer. Alternatively, other coatings (such as TiN) above the alumina layer can be removed by methods that do not substantially affect XRD measurements (e.g., chemical etching).

[0089] To study the texture of the α-Al2O3 layer, CuK was used. αX-ray diffraction was performed using radiation, and the texture coefficient TC(hkl) of the α-Al2O3 columnar crystals in different growth directions was calculated according to Harris formula (1):

[0090] Where I(hkl) = the measured intensity (integral area) of the (hkl) reflection, I0(hkl) = the standard intensity according to ICDD PDF card No. 00-010-0173, and n = the number of reflections used in the calculation. In this case, the (hkl) reflections used are: (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (2 1 4), (3 0 0), and (0 012).

[0091] The texture coefficient TC(hkl) of the TiCN columnar crystals in different growth directions is calculated according to the Harris formula (1) disclosed above, where I(hkl) is the measured intensity (integrated area) of the (hkl) reflection, I0(hkl) is the standard intensity according to ICDD PDF card No. 42-1489, and n is the number of reflections used in the calculation. In this example, the (hkl) reflections used are: (1 11), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0), and (4 2 2).

[0092] It should be noted that peak overlap is a phenomenon that may occur in X-ray diffraction analysis of coatings containing, for example, several crystalline layers and / or coatings deposited on a substrate containing a crystalline phase. This must be taken into account and compensated for. Peak overlap between α-Al₂O₃ layers and TiCN layers may affect the measurement and needs to be considered. It should also be noted that, for example, WC in the matrix may have diffraction peaks close to the peaks relevant to this invention.

[0093] Following the methods described above, the TC values ​​of α-Al₂O₃ and TiCN were analyzed using XRD. The XRD results are presented in Table 5.

[0094] Table 5. XRD Results

[0095] The coating quality deposited in the above CVD process is determined by analyzing the outer surface and morphology of Al2O3, as well as the interface between the substrate and the first TiN layer. The unevenness of the Al2O3 surface may be caused by the growth of coarse grains and is related to the formation of intermetallic phases (such as Ni3Ti) at the interface between the substrate and the coating.

[0096] In this study, a Carl Zeiss AG-Supra 40 scanning electron microscope at 3500x magnification was used to detect the roughness on the outer surface of Al2O3. The analytical results are shown in Table 6.

[0097] When the inhomogeneity of Al2O3 is difficult to determine, the interface between the substrate and the coating is analyzed to obtain accurate information about the coating quality. Cross-sectional images primarily focus on the interface between the substrate and the first TiN layer to determine whether the diffusion of binder elements interferes with coating growth. In this study, the SEM used had a magnification of 1200x (see [link to study]. Figure 2 , 4 6, 8 and 10).

[0098] Table 6. Coating Evaluation

[0099] As can be seen in Tables 5 and 6, the samples according to the present invention (i.e., Inventions 1-6) show that the CVD coating has the same properties as the CVD coating deposited on a substrate having Co as a binder (see Tables 5 and 6). Figure 14 The same performance, texture factor and appearance (see, for example) Figure 1-10 Comparing samples 1 and 2, the CVD coatings are clearly affected by the matrix composition, specifically resulting in a deterioration in appearance, which is shown in... Figure 11 and Figure 13 (Comparing Al2O3 top views 1 and 2) the unevenness is very obvious. Figure 12 The cross-sections of the two coatings are shown, and it can be seen that, compared with the present invention (e.g., Figure 2 , 4 Compared to (6, 8, and 10), its Al2O3 layer has fewer columnar crystals. Figure 12 It can also be seen that the coating contains some pores.

[0100] Example 2

[0101] Cutting tool inserts according to the invention were manufactured according to the powder composition given in Table 7, wherein the balance was WC powder with an average particle size (FSSS) of 4.2 µm. The carbon balance was adjusted by adding carbon, in accordance with standard practice, to avoid the formation of the η phase and graphite. The target carbon content was close to the formation of graphite, i.e., a slight excess of carbon. In the (Ta,Nb)C feedstock, the Ta / Nb weight ratio was 3.4, and for the (Ti,W)C feedstock, the Ti / W weight ratio was 0.84. The feedstock powder was ball-milled for 32 hours with an organic binder (PEG based on 2 wt% of the total powder weight) and a grinding slurry (water / ethanol) to form a slurry, which was then spray-dried to obtain a powder blend. This powder was pressed into a green body. The green body was sintered at 1480 °C for 1 hour under a vacuum of 40 mbar.

[0102] Table 7

[0103] After sintering, the cemented carbide cutting tool contains a γ phase in the bulk and has a surface region without the γ phase. The thicknesses of the surface regions in inventions 7 and 8 are 14 µm and 18 µm, respectively.

[0104] Subsequently, the substrate according to the present invention is coated with a CVD coating according to the method described in Example 1.

[0105] Two different substrates using Co as a binder were also coated in the same process. The composition of the substrates is shown in Table 8, with the balance being WC. The aim was to achieve the same substrate composition as inventions 7 and 8, with the only difference being the binder composition.

[0106] Table 8

[0107] The cemented carbide cutting tool contains approximately the same γ phase content in its bulk as the sample of the present invention, and has a surface region free of γ phase. The thickness of the surface region in both Comparison 4 and 5 is approximately 22 µm.

[0108] The coating parameters for all samples are shown in Table 9.

[0109] Table 9

[0110] Performance testing

[0111] Test 1

[0112] The coated insert from Example 2 was tested in a cast steel (Impax Supreme) turning operation under the following cutting conditions: f = 0.7 mm / revolution a p = 2 mm T = 30 s V c = 120 m / min The test results can be found in Table 10.

[0113] Table 10

[0114] As can be seen from Table 10, the plastic deformation of the blade with the composition according to the present invention is significantly smaller compared to the comparative blade with Co binder.

[0115] Test 2

[0116] The coated insert from Example 2 was tested during face turning of cast steel (Impax Supreme) under the following cutting conditions: V c = 170 m / min f = 0.35 mm / revolution a p = 2 mm Tool life standard is flank wear VB B = 0.3 mm.

[0117] Two blades were tested for each type, and the results shown in Table 11 are the average of the two tests.

[0118] Table 11

[0119] As shown in Table 11, the tool life of the blades with the composition according to the present invention is significantly longer compared with the comparative blades with Co binder.

[0120] Test 3

[0121] The coated insert from Example 2 was tested during the turning of medium carbon steel C45 under the following cutting conditions: V c = 250 m / min f = 0.3 mm / revolution a p = 2 mm The blades were tested under both cooled and uncooled conditions.

[0122] Tool life standard is flank wear VB B = 0.2 mm, or the area of ​​the crescent-shaped depression is greater than 0.2 mm. 2 .

[0123] The test results are shown in Table 12.

[0124] Table 12

[0125] As can be seen in Table 12, the tool life of the blade with the composition according to the present invention is significantly longer compared with the comparative blade with Co binder.

Claims

1. A coated cutting tool, the coated cutting tool comprising a coating and a carbide substrate, The cemented carbide comprises WC and 2 to 20% by weight of a Ni-based metal binder. The metal binder comprises Ni, Fe, and Cr, such that the weight ratio of Ni / (Ni+Fe) in the cemented carbide is between 0.68 and 0.8; and The Cr content in the cemented carbide results in a weight ratio of Cr / (Cr+Ni+Fe) between 0.03 and 0.12; The thickness of the coating is between 2 and 25 µm.

2. The coated cutting tool according to claim 1, wherein the weight ratio Ni / (Ni+Fe) is between 0.7 and 0.74; and The Cr content in the cemented carbide results in a weight ratio of Cr / (Cr+Ni+Fe) between 0.035 and 0.

095.

3. The coated cutting tool according to any one of the preceding claims, wherein the cemented carbide is substantially free of Co.

4. The coated cutting tool according to any one of the preceding claims, wherein the metal binder comprises more than 90% by weight of Ni, Fe and Cr.

5. The coated cutting tool according to any one of the preceding claims, wherein the cemented carbide comprises between 1 and 20% by volume of a γ phase.

6. The coated cutting tool of claim 6, wherein the cemented carbide comprises a surface region rich in binder phase without γ phase, wherein the thickness of the surface region is between 5 and 35 µm.

7. The coated cutting tool according to any one of the preceding claims, wherein the coating is a CVD coating.

8. The coated cutting tool according to any one of the preceding claims, wherein the coating comprises one or more layers selected from TiN, TiCN, AlTiN, ZrCN, TiB2, and Al2O3, or multiple layers comprising α-Al2O3 and / or κ-Al2O3.

9. The coated cutting tool according to any one of the preceding claims, wherein the coating comprises an inner TiN layer, preferably, the thickness of the TiN layer is 0.3 to 1 µm.

10. The coated cutting tool according to any one of the preceding claims, wherein the coating comprises a TiCN layer, preferably, the thickness of the TiCN layer is 6 to 12 µm.

11. The coated cutting tool according to claim 10, wherein the TiCN layer exhibits a texture coefficient TC(hkl) as defined by Harris formula (1), measured by X-ray diffraction using CuKα radiation and θ-2θ scanning: Where I(hkl) is the measured intensity (integral area) of the reflection of (hkl). I0(hkl) is the standard strength according to ICDD PDF card No. 42-1489. n is the number of reflections. The reflections used in the calculations are (1 1 1), (2 0 0), (2 2 0), (3 1 1), (3 3 1), (4 2 0), (4 2 2), and (5 1 1). Where TC(4 2 2)≥4.

12. The coated cutting tool according to any one of the preceding claims, wherein the coating comprises an α-Al2O3 layer, preferably, the thickness of the α-Al2O3 layer is 4 to 8 µm.

13. The coated cutting tool according to claim 12, wherein the α-Al2O3 layer exhibits a texture coefficient TC(hkl) as defined by Harris formula (1), as measured by X-ray diffraction using CuKα radiation and θ-2θ scanning. Where I(hkl) is the measured intensity (integral area) of the reflection of (hkl). I0(hkl) is the standard strength according to ICDD PDF card number 00-010-0173. n is the number of reflections used in the calculation, and The (hkl) reflections used are (1 0 4), (1 1 0), (1 1 3), (0 2 4), (1 1 6), (2 1 4), (3 00), and (0 0 12). Its features TC(0 0 12)≥6, preferably ≥7.

14. A method for manufacturing a coated cutting tool according to any one of claims 1-13, the method comprising the following steps: - Provides WC powder; - Provides powders containing the elements Fe, Ni, and Cr; - The powder is mixed with a grinding liquid to form a slurry, and the slurry is dried into particles. - The particles are pressed and sintered into a sintered hard alloy matrix. - The coating is deposited onto the substrate using chemical vapor deposition at a deposition temperature of at least 800°C.

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