Coated cutting tool

Abstract

The present invention relates to a coated cutting tool (1) for metal machining, having a substrate (5) of cemented carbide, cermet, ceramic, steel or high speed steel and a wear-resistant coating (6) deposited thereon, said coating (6) being a Ti alloy with 0.40≦x≦0.95, 0≦y≦0.10 and 0.85≦z≦1.15. 1-x Al x C y N z (8) layer and Ti 1-x Al x C y N z MeC present on the (8) layer a N b (9) part, 0≦a≦1, 0≦b≦1, a+b=1, and MeC a N b (9) is part of Ti 1-x Al x C y N z The coated cutting tool covers 5-28% of the layer (8). The present invention further relates to a method for manufacturing the coated cutting tool and to the use of the coated cutting tool in machining stainless steel.

Description

Technical Field

[0001] The present invention relates to a coated cutting tool for metal machining having a substrate including a Ti layer having 0.40 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.10 and 0.85 ≦ z ≦ 1.15 and a wear-resistant coating deposited thereon. The present invention further relates to a method for manufacturing a coated cutting tool and the use of the coated cutting tool in the machining of stainless steel. 1-x Al x C y N z The present invention further relates to a method for manufacturing a coated cutting tool and the use of the coated cutting tool in the machining of stainless steel.

Background Art

[0002] Tools for chip-forming metal machining generally consist of a cemented carbide substrate (also called a substrate) provided with a single-layer or multi-layer wear-resistant coating for improving cutting characteristics and / or wear characteristics. One important group of such wear-resistant coatings includes one or more layers of nitrides or carbonitrides of one or more metals. Important examples are nitrides and carbonitrides of Ti and Al, especially (Ti,Al)N.

[0003] Coatings of the aforementioned type are generally deposited by a CVD process (chemical vapor deposition) or a PVD process (physical vapor deposition).

[0004] U.S. Patent Application Publication No. 2018 / 0216224 addresses this problem and discloses a coated cutting tool having a (Ti,Al)N coating deposited by a CVD process on a cemented carbide substrate. An annealing procedure discloses a hexagonal phase of w-AlN formed at the grain boundaries of (Ti,Al)N that imparts compressive stress to the coating.

[0005] Adhesive wear is an important wear mechanism when machining stainless steel adhesives, especially in milling operations. Adhesive wear or smearing is characterized in that during the cutting process of a sticky material such as stainless steel, the workpiece material smears and adheres onto the cutting edge to form a layer of material that can form a so-called built-up edge. Flaking of the coating is a common problem associated with adhesive wear.

[0006] Therefore, when milling workpiece materials such as coated stainless steel, it is necessary to improve the performance of (Ti,Al)N coated tools.

Summary of the Invention

[0007] An object of the present invention is to provide a coated cutting tool for machining metals of coated workpiece materials such as stainless steel, particularly for milling, in which the coating exhibits high flaking resistance and a long tool life.

[0008] The present invention An object of the present invention is a coated cutting tool having a rake face, a flank face, and a cutting edge therebetween, comprising a substrate of cemented carbide, cermet, ceramic, steel or high speed steel, and a coating having a total thickness of 2 to 20 μm, wherein the coating has 0.40 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.10 and 0.85 ≦ z ≦ 1.15, and a Ti having a thickness of 1 to 18 μm 1-x Al x C y N z layer, wherein Ti 1-x Al x C y N z layer contains crystallites having a columnar structure with grain boundaries, and Ti 1-x Al x C y N z contains a face-centered cubic (fcc) crystal structure of ≧ 85% by volume, and on the rake face, Ti 1-x Al x C y N z layer, and MeC a N b (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, a + b = 1), which is a part of, and exists on the Ti 1-x Al x C y N z layer, and the Ti 1-x Al x C y N z layer is MeC a N bforms the outermost part of the coating together with a part of it, Me is Ti and / or Zr, and MeC in the region at a distance of 200 to 400 μm from the cutting edge on the rake face a N b A part of which is Ti 1-x Al x C y N z covers 5 to 28% of the layer of, and a part of MeC a N b is distributed over the region, and a part of MeC a N b is solved by a coated cutting tool including a part of and.

[0009] In a preferred embodiment, the layer of Ti 1-x Al x C y N z is a CVD layer, that is, deposited by a chemical vapor deposition (CVD) process.

[0010] In one embodiment, the layer of Ti 1-x Al x C y N z contains precipitates of Ti 1-x Al x C y N z at the grain boundaries of the crystallites of Ti 1-o Al o C p N q and the precipitates of Ti 1-o Al o C p N q have a higher Al content than inside the crystallites, and 0.95 ≦ o ≦ 1.00, 0 ≦ p ≦ 0.10, 0.85 ≦ q ≦ 1.15 and (o - x) ≧ 0.05. Preferably, 0.95 ≦ o ≦ 1.00, p = 0, q = 1 and 0.05 ≦ (o - x) ≦ 0.25.

[0011] In one embodiment, the layer of Ti 1-x Al x C y N z is the top 0.3 μm of the layer of Ti 1-x Al x Cy N z contains precipitates of Ti at the grain boundaries of the crystallites. 1-o Al o C p N q In one embodiment, the layer of Ti 1-x Al x C y N z contains precipitates of Ti at the grain boundaries of the crystallites in the uppermost 0.8 μm of the layer. 1-x Al x C y N z contains precipitates of Ti at the grain boundaries of the crystallites. 1-o Al o C p N q In one embodiment, the layer of Ti 1-x Al x C y N z contains precipitates of Ti at the grain boundaries of the crystallites throughout the layer. 1-x Al x C y N z contains precipitates of Ti at the grain boundaries of the crystallites. 1-o Al o C p N q

[0012] Ti 1-x Al x C y N z The layer of has a predominantly face-centered cubic (fcc) crystal structure. However, there may be a proportion of other softer phases, such as hexagonal AlN, present within the layer, but these are not desirable as they have an adverse effect on hardness and wear resistance if formed by co-deposition with the fcc-Ti 1-x Al x C y N z structure.

[0013] Therefore, the layer of Ti 1-x Al x C y N z in the coating of the present invention (if present, Ti at the grain boundaries 1-o Al o C p N q ​The entire layer including the volume fraction of the precipitate) contains a face-centered cubic (fcc) crystal structure of ≧85% by volume, suitably ≧90% by volume, preferably ≧95% by volume, and particularly preferably ≧98% by volume.

[0014] In one embodiment, Ti having a higher Al content than inside the crystallite 1-x Al x C y N z Ti at the grain boundary of the crystallite 1-o Al o C p N q The precipitate contains AlN having a hexagonal wurtzite crystal structure (w-AlN), and preferably, Ti having a higher Al content than inside the crystallite 1-x Al x C y N z Ti at the grain boundary of the crystallite 1-o Al o C p N q The precipitate essentially contains AlN having a hexagonal wurtzite crystal structure (w-AlN). The precipitate can contain low proportions of Ti and C. Ti having a face-centered cubic crystal structure 1-x Al x C y N z During the formation of the precipitate from the crystallite, a phase transformation to the hexagonal phase is assumed to occur. Since the hexagonal w-AlN phase has a larger volume than the face-centered cubic phase, it is clear that the transformation occurs with the expansion of the volume. Therefore, Ti 1-x Al x C y N z This expansion of the volume at the grain boundary of the crystallite is further assumed to result in an increase in the residual compressive stress in the Ti 1-x Al x C y N z layer.

[0015] Ti 1-x Al x C y N zPreferably, it has stoichiometric coefficients of 0.60 ≦ x ≦ 0.90, y = 0, and 0.85 ≦ z ≦ 1.15, more preferably 0.70 ≦ x ≦ 0.90, y = 0, and 0.85 ≦ z ≦ 1.15. In these embodiments, Ti 1-x Al x C y N z layers are essentially pure nitride layers that contain essentially no carbide carbon, excluding inevitable impurities and / or contaminants that are conditional on manufacturing. Ti 1-x Al x C y N z In the case of layers, only a limited amount of carbon dissolves in the cubic lattice, and excess carbon may be present in an amorphous form, resulting in lower layer hardness and adverse tribological properties that can affect the tool life. Therefore, this must be considered.

[0016] In one embodiment, Ti 1-x Al x C y N z layers have a lamellar structure with lamellae having a thickness of 150 nm or less, preferably 100 nm or less, and particularly preferably 50 nm or less. The lamellae have alternating different stoichiometric contents of Ti and Al and are formed from periodically alternating regions of Ti 1-x Al x C y N z layers having the same crystal structure (= crystallographic phase) and / or the same crystallographic orientation.

[0017] Part of MeC a N b covers 5 to 28% of the Ti 1-x Al x C y N z layer in a region on the rake face at a distance of 200 to 400 μm from the cutting edge. Therefore, a part of MeC 1-x Al x C y N z should remain on the Ti a N b layer. Part of MeC a Nb Ti by a part of 1-x Al x C y N z The specific ratio of the coverage rate of the layer of is provided by a strong blasting operation, but nevertheless must be controlled. The MeC to be removed a N b If there is too much, the tool life will be significantly reduced. On the other hand, if the MeC to be removed a N b is too little, the tool life will also be very poor.

[0018] Preferably, in the region on the rake face at a distance of 200 to 400 μm from the cutting edge, a part of MeC a N b covers 6 to 26%, preferably 7 to 24%, most preferably 8 to 22% of the layer of Ti 1-x Al x C y N z and a part of MeC a N b is distributed over the said region.

[0019] MeC a N b Ti by a part of 1-x Al x C y N z The coating of the layer of is appropriately determined by image analysis of at least an area of about 25 μm × 15 μm in the top surface scanning electron microscope (SEM) image at a magnification of 5000X.

[0020] MeC a N b When a square grid of 2.5 μm × 2.5 μm is placed on the top surface scanning electron microscope (SEM) image at a magnification of 5000X for a part of, more than 75%, preferably more than 90% of the square of 2.5 μm × 2.5 μm is MeC a N b and Ti 1-x Al x C y N zBoth are shown and are appropriately distributed over the region on the rake face at a distance of 200 to 400 μm from the cutting edge on the rake face such that the number of squares is at least 60.

[0021] MeC a N b In MeC a N b when it contains both Ti and Zr, they can be present in any atomic ratio. Suitably, Me is Ti or Zr. MeC a N b is such that 0 ≦ a ≦ 0.5 and 0.5 ≦ b ≦ 1 are appropriate, and 0 ≦ a ≦ 0.1 and 0.9 ≦ b ≦ 1 are preferred. In a preferred embodiment, MeC a N b is TiN.

[0022] The coated cutting tool has been subjected to strong blasting during its manufacture and provides a smoothed surface. In one embodiment, the surface roughness Ra of the coating on the rake face is 20 to 60 nm, preferably 30 to 50 nm. The surface roughness is measured in the region at a distance of 200 to 400 μm from the cutting edge.

[0023] The upper surface of the Ti 1-x Al x C y N z layer is suitably non-uniform due to the preferred facet shape on top of the Ti 1-x Al x C y N z crystallites. A part of MeC a N b remains after the blasting procedure in the manufacturing process in which the MeC 1-x Al x C y N z layer deposited on the layer of Ti a Al b Al 1-x Al x C y N z crystallites on top is Ti 1-x Alx C y N z MeC on the grain boundaries of the crystallites a N b will result in some preferred positions. Therefore, in one embodiment of the present invention, MeC a N b is Ti 1-x Al x C y N z of the layer of Ti 1-x Al x C y N z is located on at least a part of the grain boundaries of the crystallites.

[0024] Ti 1-x Al x C y N z The crystallite Ti 1-x Al x C y N z The particle size of is defined herein as the average width of the columnar Ti 1-x Al x C y N z crystallites in the center of the layer. In one embodiment, Ti 1-x Al x C y N z The particle size of is 0.2 - 0.8 μm, preferably 0.3 - 0.6 μm.

[0025] Ti 1-x Al x C y N z The Ti 1-o Al o C p N q precipitates at the grain boundaries of Ti 1-x Al x C y N z occupy the volume between the crystallites. The Ti 1-o Al o C p N q Ti 1-x Al x C y N zThe average distance between crystallites is suitably 4 to 200 nm, preferably 10 to 100 nm, and most preferably 25 to 75 nm. Ti 1-o Al o C p N q The precipitate can be regarded as a grain boundary phase, Ti 1-o Al o C p N q Ti having the precipitate at the grain boundary 1-x Al x C y N z The average distance between crystallites can also be regarded as the thickness of the grain boundary phase. Ti at the grain boundary 1-o Al o C p N q Ti having the precipitate 1-x Al x C y N z If the average distance between crystallites is too small, Ti 1-x Al x C y N z The increase in the residual compressive stress within the layer may be too small to achieve the advantages described herein, such as improvement in wear resistance and crack resistance. Ti at the grain boundary 1-o Al o C p N q Ti having the precipitate 1-x Al x C y N z If the average distance between crystallites is too large, the total amount of the precipitate increases. The precipitate appropriately contains a high proportion of hexagonal w-AlN, which is softer than face-centered cubic Ti 1-x Al x C y N z so that if the proportion of the precipitate is too high, the hardness of the layer undesirably decreases and the cutting characteristics are impaired.

[0026] The precipitate can be shown, for example, in a sufficiently thin electron transmission type polished cross-section through a sample prepared by a scanning transmission electron microscope (STEM) with a sufficiently thin coating, preferably by a focused ion beam (FIB), Ti 1-x Al xC y N z The average distance between crystallites can be determined using a STEM image. Preferably, a HAADF detector (High Angle Annular Dark Field detectors) is used, and precipitates are visualized with the reverse contrast of the BF image (bright field) and the HAADF image. Thereby, Ti with a higher Al content than inside the crystallites 1-o Al o C p N q The precipitate appears brighter than Ti in the BF image 1-x Al x C y N z and appears darker than Ti in the HAADF image 1-o Al o C p N q The precipitate is Ti 1-x Al x C y N z and appears darker than the crystallite.

[0027] For Ti with respect to the electron beam 1-x Al x C y N z With an appropriate sample thickness and orientation of the crystallites, by high-resolution transmission electron microscopy (HRTEM), Ti 1-x Al x C y N z Diffraction images from the crystallites, as well as Ti at the grain boundaries 1-o Al o C p N q Images can be obtained from which diffraction images from the regions of the effluents can be derived by Fourier transform. By indexing the diffraction images, it can be shown that the face-centered cubic (fcc) phase is present in the Ti 1-x Al x C y N z crystallites. Also, Ti 1-o Al o C p N qWhen the precipitate contains a w-AlN structure, by indexing the diffraction image, Ti 1-o Al o C p N q It can be shown that the crystal domain of the grain boundary precipitate actually has a w-AlN structure, and fcc Ti 1-x Al x C y N z There is an epitaxial relationship between the crystallite and the w-AlN precipitate can be shown.

[0028] In another method, the precipitate can be visualized by a scanning electron microscope (SEM) of an embedded metal polished cross-section or a sample polished parallel to the surface. Thereby, in the final polishing step of the preparation process described later, the effect that w-AlN is etched stronger than the cubic phase region is utilized. Since the precipitate of the present invention contains a high proportion of hexagonal w-AlN, it is clearly visible in the prepared polished cross-section.

[0029] As an example, for the preparation of a sample of a polished cross-section for the described analysis, the manufactured tool is separated, embedded in, for example, bakelite, and then the following method: grinding for 6 minutes using a grinding wheel Struers Piano220 and water; polishing for 3 minutes using Struers 9μm MD-Largo diamond suspension; polishing for 3:40 minutes using Struers 3μm MD-Dac diamond suspension; polishing for 2 minutes using Struers 1μm MD-Nap diamond suspension; chemical polishing for at least 12 minutes using Struers OP-S (a suspension of colloidal silicon dioxide with an average particle size of 0.04μm). Before the subsequent SEM inspection, the sample is washed in an ultrasonic bath and demagnetized. In the polished cross-section manufactured in this way, Ti 1-x Al x C y N z The layer is imaged by FE-SEM using a secondary electron detector at an accelerating voltage of 2.5 kV and a typical working distance of 3 - 10 mm. Thereby, in the polished cross-section of the sample, Ti having a face-centered cubic (fcc) structure of about 100% in the non-annealed state1-x Al x C y N z Columnar structures of the layer are observed. Precipitates at grain boundaries etched more strongly than crystallites in the final step of chemical polishing in the above preparation can be identified as darker regions due to topography and atomic number contrast. The crystallites essentially contain 100% face-centered cubic phase, but the proportion of the w-AlN phase formed by annealing is Ti 1-o Al o C p N q contained in the grain boundary precipitates, whereby Ti 1-o Al o C p N q The grain boundary precipitates are considered to consist mainly of w-AlN. Ti 1-o Al o C p N q Determination of the spread of the grain boundary precipitates and Ti 1-x Al x C y N z Determination of the minimum content of the fcc phase in the layer is generally possible on the image thus generated by measuring the image or by applying established image analysis procedures.

[0030] In one embodiment, Ti 1-x Al x C y N z the layer has a residual compressive stress in the range of preferably <0 MPa to -5000 MPa, more preferably -300 MPa to -3500 MPa, measured by the (222) reflection at about 81.5 - 82 degrees 2 theta of the fcc-Ti 2 Al 1-x Al x C y N z phase.

[0031] Ti 1-x Al x C y N zThe residual compressive stress within the layer improves the resistance to crack formation, particularly to the formation of comb cracks, and thus the wear resistance of the tool. However, Ti 1-x Al x C y N z If the residual compressive stress of the layer is too high, problems with adhesion and chipping of the layer may occur.

[0032] In one embodiment, there is a further layer provided directly on a substrate having a thickness of 0.05 μm to 2 μm, preferably 0.1 μm to 1 μm. The further layer is a metal nitride or metal carbonitride layer, and Me is an element belonging to Group 4 of the Periodic Table of the Elements, preferably a TiN layer or a Ti(C,N) layer. This further layer appropriately has a function of improving the adhesion between the substrate and the upper layer.

[0033] Ti 1-x Al x C y N z The layer of TiAlCN preferably has a thickness of 1 to 15 μm, more preferably 3 to 12 μm, and most preferably 5 to 10 μm.

[0034] The total thickness of the coating is preferably 2 to 16 μm, more preferably 5 to 12 μm.

[0035] The substrate is preferably a cemented carbide substrate.

[0036] The cemented carbide appropriately contains 5 to 15 wt% Co, optionally up to 10 wt% of one or more carbides or carbonitrides of metals from Groups 4, 5, and 6 of the Periodic Table of the Elements, and 75 to 95 wt% WC. In one embodiment, the cemented carbide has a composition of 5 to 15 wt% Co, optionally up to 10 wt% of one or more carbides or carbonitrides of metals from Groups 4, 5, and 6 of the Periodic Table of the Elements, and the balance WC. The metals of Groups 4, 5, and 6 in the Periodic Table that may be carbides or carbonitrides appropriately belong to the groups of Ti, Ta, Nb, V, Zr, Cr, and Mo, and W may further be present in the carbide or carbonitride optionally.

[0037] The coated cutting tool is preferably a milling insert or a turning insert, a drill or an end mill. Preferably, the coated cutting tool is a milling insert.

[0038] The present invention also relates to a coated cutting tool according to the present specification having a rake face, a flank face and a cutting edge therebetween, comprising a substrate of cemented carbide, cermet, ceramic, steel or high speed steel, and a Ti layer having a thickness of 1 to 18 μm with 0.40 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.10 and 0.85 ≦ z ≦ 1.15 1-x Al x C y N z and a coating having a total thickness of 2 to 20 μm, wherein the Ti 1-x Al x C y N z layer contains crystallites of a columnar structure having grain boundaries, and Ti 1-x Al x C y N z comprises a face-centered cubic (fcc) crystal structure of ≧ 85% by volume, a process for the manufacture of a coated cutting tool, the process comprising the following steps in the following order: · providing a layer of Ti 1-x Al x C y N z by a CVD process; and · providing a layer of MeC 1-x Al x C y N z (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, a + b = 1) by a CVD process directly above the layer of Ti a N b where Me is Ti and / or Zr; · blasting the surface of the coating until a portion of MeC 1-x Al x C y N z remains in a region on the rake face at a distance of 200 to 400 μm from the cutting edge covering 5 to 28% of the layer of Ti a N b where MeC a N bA blasting step in which a part is distributed over the region Relating to a process, including

[0039] Ti 1-x Al x C y N z The deposition of the layer is suitably carried out at a process temperature in the range of 625 to 800 °C.

[0040] In one embodiment, the process includes subjecting the deposited layer of Ti 1-x Al x C y N z to annealing for a duration of 0.5 to 12 hours at a temperature in the range of 700 to 950 °C respectively under the exclusion of air or oxygen, the conditions being that precipitates of Ti 1-x Al x C y N z are formed at the grain boundaries of the Ti 1-o Al o C p N q crystallites, and the precipitates of Ti 1-o Al o C p N q are selected to have a higher Al content than inside the Ti 1-x Al x C y N z crystallites, and 0.95 ≦ o ≦ 1.00, 0 ≦ p ≦ 0.10, 0.85 ≦ q ≦ 1.15 and (o - x) ≧ 0.05. Suitably, the precipitates of Ti 1-o Al o C p N q are at least 0.3 μm of the top of the layer of Ti 1-x Al x C y N z preferably at least 0.8 μm of the top of the layer of Ti 1-x Al x C y N z and most preferably at least 0.8 μm of the top of the layer of Ti 1-x Al x C y Nz is formed across the entire layer of Ti 1-x Al x C y N z at the grain boundaries of the crystallites.

[0041] In one embodiment, for depositing the layer of Ti 1-x Al x C y N z the CVD process involves using TiCl which reacts in the reaction zone 4 AlCl 3 H 2 and NH 3 as precursors. In a preferred embodiment, there is a first precursor gas mixture containing TiCl 4 AlCl 3 and H 2 and a second precursor gas mixture containing H 2 and NH 3 The first and second precursor gas mixtures are mixed at the inlet to the reaction zone.

[0042] Preferably, the CVD process for depositing the Ti 1-x Al x C y N z layer is an LP-CVD process (low-pressure CVD process), which is carried out at a process pressure in the CVD reactor of 0.05 - 8 kPa, preferably 0.1 - 7 kPa, particularly preferably 0.3 - 2 kPa. At higher process pressures, generally, a Ti 1-x Al x C y N z layer having a face-centered cubic and columnar structure is not achieved, rather a layer having a significant proportion of w-AlN is achieved. Lower process pressures require very high technical effort to generate a vacuum, and furthermore, the coating process at lower pressures has a lower throughput for uniformly distributing the coating thickness across complex shaped parts.

[0043] In one embodiment, MeC a N bTo deposit the layer, the CVD process involves using MeCl as a precursor 4 , H 2 , and one or both of a nitrogen source and a carbon source. The nitrogen source is preferably N 2 , or NH 3 together with N 2 . As the carbon source, CH 3 CN is preferred. Me is Ti and / or Zr.

[0044] Annealing of the deposited Ti 1-x Al x C y N z layer is suitably carried out at a temperature of 750 - 900 °C, preferably 800 - 850 °C.

[0045] The duration of annealing is suitably 1 - 6 hours.

[0046] Annealing is preferably carried out immediately after deposition of the Ti 1-x Al x C y N z layer in the same reactor. This is to avoid cooling cracks that can occur when the deposited Ti 1-x Al x C y N z deposition layer is cooled before deposition of MeC a N b .

[0047] In one embodiment, annealing of the deposited Ti 1-x Al x C y N z layer is carried out both before, during, and after deposition of the MeC a N b layer.

[0048] In a preferred embodiment of the process, the temperature and duration conditions during annealing are such that the Ti in the Ti 1-x Al x C y N z layer after annealing1-o Al o C p N q After the precipitation of the precipitate, Ti 1-x Al x C y N z is selected such that the remaining content of the face-centered cubic (fcc) crystal structure in the layer is ≧ 85% by volume, preferably ≧ 90% by volume, more preferably ≧ 95% by volume, and particularly preferably ≧ 98% by volume.

[0049] An essential process condition is also the exclusion of air or oxygen during annealing, otherwise the layer of Ti 1-x Al x C y N z may be oxidized. This process can be carried out, for example, under a vacuum or protective gas atmosphere such as argon, hydrogen or nitrogen.

[0050] Preferably, the surface of the coating is blasted until a part of MeC 1-x Al x C y N z remains in the region on the rake face at a distance of 200 - 400 μm from the cutting edge, covering 6 - 26%, preferably 7 - 24%, most preferably 8 - 22% of the layer of Ti a N b and a part of MeC a N b is distributed over the region.

[0051] In MeC a N b , Me is Ti and / or Zr. In MeC a N b when it contains both Ti and Zr, they can be present in any atomic ratio. Suitably, Me is Ti or Zr. For MeC a N b , 0 ≦ a ≦ 0.5, 0.5 ≦ b ≦ 1 is suitable, and 0 ≦ a ≦ 0.1, 0.9 ≦ b ≦ 1 is preferred. In a preferred embodiment, MeC a N b is TiN.

[0052] In one embodiment, Ti 1-x Al x C y N z The precipitates of Ti 1-o Al o C p N q at the grain boundaries of the crystallites include AlN having a hexagonal wurtzite crystal structure (w-AlN).

[0053] In one embodiment, there is a further layer provided directly on a substrate having a thickness of 0.05 μm to 2 μm, preferably 0.1 μm to 1 μm, by a CVD process. The further layer is a metal nitride or metal carbonitride layer, and Me is an element belonging to Group 4 of the periodic table of elements, preferably a TiN layer or a Ti(C,N) layer. To deposit this further layer, the CVD process uses MeCl 4 , H 2 , and one or both of a nitrogen source and a carbon source. The nitrogen source is preferably N 2 . The carbon source is preferably CH 4 or CH 3 CN. Me is preferably Ti and / or Zr, most preferably Ti.

[0054] Preferably, the blasting of the surface of the coating is performed by wet blasting.

[0055] As used herein, "wet blasting" means a blasting process that uses a medium containing abrasive particles, such as aluminum oxide particles, in a liquid that forms a slurry. The material is typically removed to some extent to result in a smoother surface of the coating. Also, some residual compressive stress is introduced into the coating.

[0056] Wet blasting uses a blasting gun in which the slurry exits the nozzle. In one embodiment, wet blasting is performed using a blasting pressure at the exit of the nozzle of 1.8 to 3.5 bar, preferably 2.0 to 3 bar.

[0057] In one embodiment, the concentration of aluminum oxide particles in the slurry is 10 to 25% by volume, preferably 15 to 20% by volume.

[0058] For example, for abrasive grains used in blasting, there is an established standard - FEPA (Federation of European Producers of Abrasives) that defines the particle size. The aluminum oxide particles used in wet blasting appropriately belong to one or more of FEPA designations F120 to F240, i.e., an average grit size of about 44 to about 109 μm, preferably an average grit size of F150 to F230, i.e., an average grit size of about 36 to about 82 μm. MeC a N b To obtain the desired results regarding the coating rate, an appropriate grit size is selected.

[0059] In one embodiment, the wet blasting is performed in a blasting direction in which the angle with respect to the surface of the coated cutting tool is 40 to 90°, preferably 50 to 90°, and most preferably 80 to 90°.

[0060] In one embodiment, the distance between the blasting gun nozzle and the surface of the coated cutting tool is 75 to 200 mm, preferably 100 to 150 mm.

[0061] The desired blasting time depends on all other blasting parameters, i.e., blasting pressure, concentration of aluminum oxide particles, distance between the blasting gun nozzle and the surface of the coated cutting tool, and blasting angle.

[0062] The blasting time is appropriately 1 to 80 minutes, preferably 1.5 to 60 minutes. These time ranges are generally effective for blasting processes in which about 200 to 400 inserts are grouped on a support net before blasting. Thus, the blasting time for an individual insert is about 0.5 to 30 seconds, preferably about 1 to 20 seconds.

[0063] In one embodiment, when a high blast angle, i.e., between 80 and 90°, is used, the blast time in wet blasting is suitably 10 to 80 minutes, preferably 20 to 60 minutes. These time ranges are generally effective for a blasting process in which about 200 to 400 inserts are gathered on a support net before blasting. Accordingly, the blast time for an individual insert is about 2 to 10 seconds.

[0064] In one embodiment, when a lower blast angle, i.e., between 45 and 70°, is used, the blast time in wet blasting is suitably 1 to 10 minutes, preferably 2 to 5 minutes. These time ranges are generally effective for a blasting process in which about 200 to 400 inserts are gathered on a support net before blasting. Accordingly, the blast time for an individual insert is about 0.2 to 2 seconds.

[0065] The purpose of the blasting is both to smooth the surface of the coating and to remove MeC a N b until a small part of the layer of 1-x Ti x Al y C z N a remains covered. If excessive MeC b N a remains after blasting, the tool life will not reach its optimal level. On the other hand, if too little MeC b N a remains after blasting, it will have an adverse effect on the tool life. b

[0066] Finally, the present invention also relates to the use of the coated cutting tool described herein in the machining of stainless steel.

[0067] Method Scanning electron microscopy (SEM): For the scanning electron microscope images, a Supra 40 electron microscope equipped with a field emission cathode made by Carl Zeiss was used. The imaging conditions for finding and characterizing grain boundary precipitates are described above. MeC a N b Ti by part of 1-x Al x C y N z The coating of the layer of is appropriately determined by image analysis of at least a 25 μm × 15 μm area of a top surface scanning electron microscope (SEM) image at a magnification of 5000X.

[0068] In the examples of this specification, an area of about 25 μm × 18 μm of a top surface scanning electron microscope (SEM) image at a magnification of 5000X was used.

[0069] The software used for image analysis was "ImageJ". In the image analysis, MeC a N b region and Ti 1-x Al x C y N z sufficient contrast is provided between the regions of, for example, black and white. Then, the amount of each region can be determined.

[0070] The distribution of part of MeC a N b over the region on the rake face at a distance of 200 - 400 μm from the cutting edge is performed by electronically or as a printed image placing a 3 μm × 3 μm square grid on a top surface scanning electron microscope (SEM) image at a magnification of 5000X. MeC a N b region and Ti 1-x Al x C y N z The number of squares containing both regions of is determined. At least 70 squares are investigated. MeC a N b The very small region of MeC, that is, the maximum width in an image less than 0.1 μm a N bis considered unimportant and is thus ignored. Among all the squares, the proportion of squares that contain both the region of MeC a N b and the region of Ti 1-x Al x C y N z is determined.

[0071] Residual stress measurement: For the analysis of residual stress, the {222} interference of the face-centered cubic Ti 1-x Al x C y N z layer can be measured according to the sinψ method by applying 25 ψ angles (-60° to +60°, increasing by 5° each) using an appropriate diffractometer for this purpose. After background subtraction, Lorentz polarization correction, and Kα 2 subtraction (Rachinger separation), the position of the interference line is determined by fitting a profile function to the measurement data. The elastic constants applied are 1 / 2s 2 = 1.93 TPa 2 and s -1 = -0.18 TPa 1 respectively. -1

[0072] Ti 1-x Al x C y N z Characterization of the lamellar structure in the Ti Ti 1-x Al x C y N z layer: The presence and characterization of the lamellar structure in the Ti

[0073] Al C N layer can be carried out by, for example, X-ray diffraction (XRD) and by performing conventional and high-resolution transmission electron microscopy (TEM and HR-TEM) as described in, for example, J. Keckes et al., "Self-organized periodic soft-hard nano-lamellae in polycrystalline TiAlN thin films", Thin Solid Films 545 (2013), pages 29 - 32.

[0073] Surface roughness: The surface roughness is the arithmetic mean deviation Ra according to ISO4287:1997.

Brief Description of the Drawings

[0074]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0075] FIG. 1 shows a schematic view of an embodiment of a cutting tool (1) having a rake face (2), a flank face (3), and a cutting edge (4). The cutting tool (1) is a milling insert in this embodiment.

[0076] FIG. 2 schematically shows a cross-section of a coated cutting tool (1) of an embodiment of the present invention having a substrate (5) and a coating (6). The coating (6) consists of a layer of TiN (7) closest to the substrate (5) and a layer of TiAlN (8) following it. A part of TiN (9) remains on the layer of TiAlN (8) after post-treatment.

[0077] Figure 3 shows a SEM image of the cross-section of the coating of TiAlN(8) with an upper layer of TiN(9) deposited thereon. No post-treatment of the coating was performed.

[0078] Figure 4 shows a SEM image of the cross-section of the coating according to an embodiment of the present invention. A layer of TiN(7) is present on the cemented carbide substrate(5), followed by a layer of TiAlN(8). Since the surface of the coating has been post-treated, it is substantially smoothed, and in particular, the upper surface of the TiAlN crystallites is worn. A part of TiN(9) exists to some extent, especially across the grain boundaries of the TiAlN crystallites.

[0079] Figure 5 shows a SEM image at a magnification of 5000 times of an embodiment of the present invention, showing a region of about 18 μm × 25 μm. A part of TiN(9) is seen on the layer of TiAlN(8). A part of TiN(9) is brighter in the image than the exposed TiAlN(8).

[0080] Figure 6 shows a SEM image at a magnification of 5000 times of an embodiment of the present invention, showing a region of about 18 μm × 25 μm. The SEM image is subjected to image processing so as to be able to separate the TiN region and the TiAlN region in image analysis. A part of TiN(8) is seen in white on the black layer of TiAlN(8). The coating rate of TiN on TiAlN is about 9%.

[0081] Figure 7 shows the same image-processed SEM image as Figure 6, with a square grid of about 2.5 μm × 2.5 μm placed on the image to determine the distribution of a part of TiN(9). The total number of squares is 60.

Example

[0082] Example 1: As the substrate in these examples, a cemented carbide cutting insert (milling insert) of geometric shape R390 - 11 M - MM having a composition of 90.5 wt% WC, 8 wt% Co, and 1.5 wt% (NbC + TaC) was used.

[0083] Figure 1 shows an embodiment of a coated cutting tool (1) which is a milling insert. The cutting tool (1) has a rake face (2), a flank face (3), and a cutting edge (4) therebetween.

[0084] For the coating of a cemented carbide indexable cutting insert, a Bernex BPX325S type CVD coating reactor with a reactor height of 1250 mm, a reactor diameter of 325 mm and a filling device volume of 40 liters was used. The gas flow was radial with respect to the longitudinal axis of the reactor.

[0085] Ti 1-x Al x C y N z To adhere the layer, a TiN layer with a thickness of about 0.3 μm was first deposited by CVD on the cemented carbide substrate under the deposition conditions shown in Table 1 just above the cemented carbide substrate. TIFF0007692428000001.tif30170

[0086] Ti 1-x Al x C y N z For the preparation of the layer, a first precursor gas mixture (VG1) containing the starting compounds TiCl 4 and AlCl 3 and a second precursor gas mixture (VG2) containing the starting component NH 3 as a reactive nitrogen component were separately introduced into the reactor so that the mixing of the two gas flows did not occur earlier than at the inlet to the reaction zone. The volumetric gas flows of the precursor gas mixtures (VG1) and (VG2) were set so that the average residence time of the reaction gases in the reactor and the total volumetric flow under normal conditions were achieved. Ti 1-x Al x C y N z The parameters for the preparation of the layer are shown in Table 2. Ti 1-x Al x C y N z The thickness of the layer was about 8 μm. TIFF0007692428000002.tif34170

[0087] After that, the prepared cutting insert was subjected to heat treatment for a certain period under the conditions shown in Table 3. TIFF0007692428000003.tif23170

[0088] During the heat treatment period, a 0.3-μm top layer of TiN was deposited. The process parameters for the preparation of this TiN layer are shown in Table 4. Therefore, out of the 3 hours and 15 minutes of heat treatment, there was a 45-minute TiN deposition time. TIFF0007692428000004.tif29170

[0089] Ti 1-x Al x C y N z For the characterization of the layers, X-ray diffraction (XRD), electron diffraction, especially EBSD, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and transmission electron microscopy (TEM) were applied.

[0090] For the deposited Ti 1-x Al x C y N z x = 0.80, y = 0, and z = 1.

[0091] Ti 1-x Al x C y N z The average grain size was 0.4 μm. The grain size was measured by drawing a line in the middle of the layer and calculating the average width of each Ti 1-x Al x C y N z columnar crystal grain width, and the average value was calculated. A cross-sectional SEM image at 5000 times magnification was taken, and the average value of the individual widths of about 20 crystal grains was calculated.

[0092] Sample 1 was not post-treated at all, while Samples 2 to 8 were post-treated by different blast procedures with different severities.

[0093] Wet blasting was performed using aluminum oxide grit (sand) of the size of the "mesh" described in the table. The distance between the blast gun nozzle and the coated surface was 120 mm for top blasting and 135 mm otherwise. When shot peening was used for Sample 2, ZrO 2 -based beads were used in the dry form, and the beads had a size of 70 - 120 μm. The blast angle is the angle between the coated surface and the blast direction. The blast pressure is the pressure when the slurry exits the blast gun nozzle.

[0094] The different treatments were as follows. 1. No treatment 2. Shot peening (90°, 5.3 bar) + micro wet blasting (11 - 15°, 2.6 bar, FEPA 240 mesh grit size, 3 minutes) 3. TB3 (top wet blasting 90°, 2.1 bar, FEPA 230 mesh grit size, 27 minutes) 4. ERB (angled wet blasting 55°, 2.8 bar, FEPA 280 mesh grit size, 3 minutes) 5. TB1 (top wet blasting 90°, 2.0 bar, FEPA 230 mesh grit size, 54 minutes) 6. ERB (angled wet blasting 55°, 2.8 bar, 150 mesh grit size, 1.8 minutes) 7. ERB (angled wet blasting 55°, 2.1 bar, 150 mesh grit size, 3 minutes) 8. ERB (angled wet blasting 55°, 3.2 bar, 150 mesh grit size, 4.5 minutes)

[0095] For each sample, SEM images were analyzed at a magnification of 5000 times to determine the amount of TiN remaining on the outer surface. An area of approximately 18 μm × 25 μm, about 250 μm from the cutting edge of the rake face, was analyzed. The software used for image analysis was "ImageJ".

[0096] For some samples, the surface roughness Ra of the coating after post-treatment was measured. The measurement was taken on the rake face at a distance of approximately 250 μm from the cutting edge.

[0097] The results are shown in Table 5. TIFF0007692428000005.tif60170

[0098] When a part of TiN was distributed over the area on the rake face at a distance of 250 μm from the cutting edge and a 2.5 μm × 2.5 μm square grid was placed on the top surface scanning electron microscope (SEM) image at a magnification of 5000 times, the following results were obtained. TIFF0007692428000006.tif61170

[0099] Figure 6 shows a 5000-fold magnification SEM image of Sample 6, showing an area of approximately 18 μm × 25 μm. The image has been subjected to image processing. A part of TiN appears white, and TiAlN appears black.

[0100] Figure 7 shows the same image processing SEM image as Figure 6, with a 2.5 μm × 2.5 μm square grid placed on the image to determine the distribution of a part of TiN on the surface.

[0101] Analysis using transmission electron microscopy (TEM) revealed that the Ti 1-x Al x C y N z layer contains Ti 1-x Al x C y N z precipitates at the grain boundaries of the Ti 1-o Al o C p N q crystallites. Furthermore, the presence of a face-centered cubic (fcc) phase with ≧95% by volume in the Ti 1-x Al x C y N z crystallites and Ti 1-o Al o C p N qEpitaxial relationship with crystal domains in the precipitate, and Ti 1-o Al o C p N q There is the presence of the w-AlN phase in the precipitate. Ti having the w-AlN structure 1-o Al o C p N q Ti having the precipitate 1-x Al x C y N z The average distance at the grain boundaries of the crystallites is about 25 nm.

[0102] Furthermore, Ti 1-x A lx C y N z There is a lamellar structure of the layer. Alternating lamellae of higher Ti ratio (lower Al ratio) and lower Ti ratio (higher Al ratio) exist. The regions with a higher Ti ratio are generally significantly thinner than the Al-rich regions of the lamellar structure.

[0103] Furthermore, the overall structure consists of a face-centered cubic (fcc) phase. The entire lamellar structure consists of a face-centered cubic (fcc) phase, whereby the same orientation exists within one crystallite.

[0104] Example 2: Cutting test Samples 1 to 8 were tested in a milling operation (wet corner cracking and flaking test) under the following cutting conditions. Workpiece material: Stainless steel: SS2343 - 28PR Procedure: Up milling, wet coolant Feed per tooth: f z = 0.2 mm Cutting depth: a p = 3 mm Cutting speed: v c = 150 m / min Milling width: a e = 15 mm Pass length: 200 mm

[0105] Cut-off criterion, VBmax is chipping > 0.3 mm

[0106] The results are shown in Table 7. TIFF0007692428000007.tif73170

Claims

1. A coated cutting tool (1) having a rake face (2), a flank face (3), and a cutting edge (4) therebetween, comprising a substrate (5) of cemented carbide, cermet, ceramic, steel or high speed steel, and a coating (6) having a total thickness of 2 to 20 μm, wherein the coating (6) ・ 0.40 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.10 and 0.85 ≤ z ≤ 1.15, and Ti having a thickness of 1 to 18 μm １－ｘ Al ｘ C ｙ a layer (8) of Ti １－ｘ Al ｘ C ｙ a layer (8) of Ti １－ｘ Al ｘ C ｙ N ｚ contains a face-centered cubic (fcc) crystal structure of ≥ 85% by volume, and on the rake face (2), the layer (8) of Ti １－ｘ Al ｘ C ｙ Nz and ・MeC ａ N ｂ Part of (9) (0 ≤ a ≤ 1, 0 ≤ b ≤ 1, a + b = 1), Ti １－ｘ Al ｘ C ｙ Exists on the layer (8) of Ti １－ｘ Al ｘ C ｙ Nz. The layer (8) of Ti ａ Al ｂ C ａ Nz forms the outermost part of the coating (6) together with part of MeC ｂ N (9), where Me is Ti and / or Zr, and MeC １－ｘ N ｘ Part of (9) is Ti ｙ Al ａ C ｂ Covers 5 - 28% of the layer (8) of Nz, and part of MeC ａ N ｂ Part of (9) is distributed over the said region, part of MeC comprises a coated cutting tool (1).

2. Ti １－ｘ A ｘ C ｙ N ｚ The layer (8) is made of Ti １－ｘ A ｘ C ｙ N ｚ Ti at the grain boundaries of the crystallites １－ｏ A ｏ C ｐ N ｑ The precipitates include Ti １－ｏ A ｏ C ｐ N ｑ The precipitates are Ti １－ｘ A ｘ C ｙ N ｚ 2. The coated cutting tool (1) according to claim 1, having a higher Al content than inside the crystallite, 0.95≦o≦1.00, 0≦p≦0.10, 0.85≦q≦1.15 and (o−x)≧0.

05.

3. Ti １－ｘ Al ｘ C ｙ N ｚ The layer (8) of Ti, Al, C, and N contains precipitates of Ti, Al, C, and N in the range of 0.3 μm from the top of the layer (8) of Ti1−xAlxCyNz at the grain boundaries of the Ti1−xAlxCyNz crystallites. １－ｏ Al ｏ C ｐ N ｑ The coated cutting tool (1) according to claim 2, which contains precipitates of Ti, Al, C, and N.

4. Ti １－ｘ Al ｘ C ｙ N ｚ The layer (8) of is Ti １－ｘ Al ｘ C ｙ N ｚ The Ti at the grain boundaries of the crystallites of １－ｏ Al ｏ C ｐ N ｑ The coated cutting tool (1) according to any one of claims 2 or 3, comprising precipitates of It should be noted that the text seems to be incomplete in some parts where "" is used. If there are specific substances or elements that should be filled in those places, it would be more accurate to have the complete information for a more precise translation.

5. Ti １－ｘ Al ｘ C ｙ N ｚ The Ti １－ｏ Al ｏ C ｐ N ｑ precipitates at the grain boundaries of the crystallites contain AlN having a hexagonal wurtzite crystal structure (w-AlN), and the coated cutting tool (1) according to any one of claims 2 to 4.

6. Ti １－ｘ Al ｘ C ｙ N ｚ The coated cutting tool (1) according to any one of claims 1 to 5, characterized in that (8) contains a face-centered cubic (fcc) crystal structure of ≧ 90% by volume.

7. Ti １－ｘ Al ｘ C ｙ N ｚ The coated cutting tool (1) according to any one of claims 1 to 6, characterized in that it has stoichiometric coefficients of 0.60 ≦ x ≦ 0.90, y = 0 and 0.85 ≦ z ≦ 1.

15.

8. In the region on the rake face (2) at a distance of 200 to 400 μm from the cutting edge (4), MeC ａ N ｂ (9) part of which is Ti １－ｘ Al ｘ C ｙ Nz layer (8) covering 7 to 24%, and part of MeC ａ N ｂ (9) is distributed over the said region, the coated cutting tool (1) according to any one of claims 1 to 7.

9. MeC ａ N ｂ The coated cutting tool (1) according to any one of claims 1 to 8, wherein (9) is TiN or Ti(C, N).

10. The coated cutting tool (1) according to any one of claims 1 to 9, characterized in that the surface roughness Ra of the coating on the rake face (2) is 20 to 60 nm at a distance of 200 to 400 μm from the cutting edge (4).

11. It has a rake face (2), a flank face (3), and a cutting edge (4) therebetween, a substrate (5) of cemented carbide, cermet, ceramic, steel or high-speed steel, and 0.40 ≦ x ≦ 0.95, 0 ≦ y ≦ 0.10, and 0.85 ≦ z ≦ 1.15, and Ti with a thickness of 1 to 18 μm １－ｘ Al ｘ C ｙ a coating (6) with a thickness of 2 to 20 μm including a layer (8) of Ti １－ｘ Al ｘ C ｙ Nz, the layer (8) of Ti １－ｘ Al ｘ C ｙ N ｚ (8) includes a face-centered cubic (fcc) crystal structure of ≧ 85% by volume, and a method for manufacturing a coated cutting tool (1), the method comprising ・Provide a layer (8) of Ti １－ｘ Al ｘ C ｙ N₂ by a CVD process, and ・ Ti １－ｘ Al ｘ C ｙ By a CVD process directly above the layer (8) of Nz, MeC ａ N ｂ Providing a layer (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, a + b = 1) of (9), wherein Me is Ti and / or Zr, and the step of providing ・Ti １－ｘ Al ｘ C ｙ MeC remaining in the region on the rake face (2) at a distance of 200 to 400 μm from the cutting edge (4) covering 5 to 28% of the layer (8) of Nz ａ N ｂ A step of blasting the surface of the coating (6) until a part of MeC ａ N ｂ (9) is distributed over the region, the step of blasting comprises a method.

12. Before the step of blasting the surface of the coating (6), Ti １－ｘ Al ｘ C ｙ N ｚ The deposited layer of (8) is annealed at a temperature in the range of 700 to 950 °C for a duration of 0.5 to 12 hours under the exclusion of air or oxygen, and the conditions are that Ti １－ｘ Al ｘ C ｙ N ｚ At the grain boundaries of the crystallites, Ti １－ｏ Al ｏ C ｐ N ｑ Precipitates are formed, and the precipitates of Ti １－ｏ Al ｏ C ｐ N ｑ Are selected to have an Al content higher than that inside the Ti １－ｘ Al ｘ C ｙ N ｚ Crystallites, and 0.95 ≦ o ≦ 1.00, 0 ≦ p ≦ 0.10, 0.85 ≦ q ≦ 1.15 and (o - x) ≧ 0.05, The method according to claim 11, characterized in that.

13. Ti １－ｘ Al ｘ C ｙ N ｚ Annealing of the deposited layer of (8) is performed before, during, and after deposition of the layer of MeC ａ N ｂ The method according to claim 12, characterized in that annealing of the deposited layer of (8) is performed before, during, and after deposition of the layer of (9).

14. Ti １－ｘ Al ｘ C ｙ The CVD process for the deposition of the layer (8) of Nz is an LP-CVD process, and the CVD process is carried out at a process pressure in the CVD reactor of 0.05 to 8 kPa, characterized in that the method according to any one of claims 11 to 13.

15. The surface blasting of the coating (6) is carried out by wet blasting using a slurry of aluminum oxide particles exiting a blasting gun nozzle, the wet blasting is carried out using a blasting pressure at the outlet of the nozzle of 1.8 to 3.5 bar, the concentration of aluminum oxide particles in the slurry is 10 to 25% by volume, the aluminum oxide particles belong to one or more of the FEPA designations F120 to F240, the distance between the blasting gun nozzle and the surface of the coated cutting tool (1) is 75 to 200 mm, the wet blasting is carried out in a blasting direction having an angle of 40 to 90° with respect to the surface of the coated cutting tool (1), and the blasting time is 1 to 75 minutes. The method according to any one of claims 11 to 14, characterized in that.

16. Use of the coated cutting tool (1) according to any one of claims 1 to 10 in the machining of stainless steel.

Images