Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
  • C23C30/005—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process on hard metal substrates
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B27/00—Tools for turning or boring machines; Tools of a similar kind in general; Accessories therefor
  • B23B27/14—Cutting tools of which the bits or tips or cutting inserts are of special material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B51/00—Tools for drilling machines
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23C—MILLING
  • B23C5/00—Milling-cutters
  • B23C5/16—Milling-cutters characterised by physical features other than shape
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
  • C23C14/0641—Nitrides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering
  • C23C14/3485—Sputtering using pulsed power to the target
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering
  • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering
  • C23C14/35—Sputtering by application of a magnetic field, e.g. magnetron sputtering
  • C23C14/352—Sputtering by application of a magnetic field, e.g. magnetron sputtering using more than one target
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
  • C23C28/042—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material including a refractory ceramic layer, e.g. refractory metal oxides, ZrO2, rare earth oxides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
  • C23C28/044—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material coatings specially adapted for cutting tools or wear applications

Definitions

• the present invention relates to a coated cutting tool for metal machining wherein the cutting tool has a coating comprising a (Ti,AI,Si)N layer.
• cutting tools for metal machining comprise a substrate of a hard material such as cemented carbide, cubic boron nitride, or cermet, and a wear resistant coating deposited on the surface of the substrate.
• the wear resistant coating is usually deposited by either chemical vapour deposition (CVD) or physical vapour deposition (PVD).
• the coating should ideally have a high hardness but at the same time possess sufficient toughness in order to withstand severe cutting conditions as long as possible.
• a coating for a metal cutting tool should also ideally have a low thermal conductivity since this correlates to the heat resistance of a coating.
• Cathodic arc evaporation uses an electric arc to vaporise material from a cathode target. The vaporised material, or a compound thereof, is then condensed on a substrate. Cathodic arc evaporation has advantages of high deposition rate but drawbacks such as droplets of target material are included in the coating and as well on the surface. This may create weakness in the coating and a comparatively rough surface. In many metal cutting applications a smooth surface of a deposited wear resistant coating is beneficial.
• Reactive sputtering is a second method of PVD.
• a plasma of ionised inert gas is created which is made bombarding a target material. Atoms from the target material are ejected and accelerated towards a substrate in the presence of a reactive gas, e.g., nitrogen. Since there is no problem with droplet formation a coating with a smooth surface is generally obtained.
• a reactive gas e.g., nitrogen
• High-power impulse magnetron sputtering is a special type of sputtering allowing for great flexibility in varying process parameters, especially the power level used (average power, peak pulse power) in combination with pulse on-time and using high bias voltages.
• HIPIMS enables high metal ionisation and allows for high quality coatings to be provided and by controlling the levels of metal ionisation very special coatings may be produced.
• thermal resistance is herein meant a low thermal conductivity of the coating which then protects the cutting tool body from excessive heat which is damaging for the substrate.
• a better wear resistance means a longer tool life.
• PVD (Ti,AI)N coatings are commonly used as wear resistant coatings in cutting tools.
• a sufficiently high Al content is desired as the oxidation stability of a (Ti,AI)N coating is better with increased Al content.
• the hot hardness increases by increasing the Al content.
• a drawback with (Ti, Al, Si)N is that already at moderate Al contents of the metal elements, together with Si in an amount of only a couple of at% of the metal elements, a further structure may form which is hexagonal or amorphous, such as an amorphous grain boundary phase.
• a hexagonal phase, as well as an amorphous phase, contributes to bad mechanical properties, such as insufficient hardness and insufficient plane strain modulus. It is therefore desired to provide a (Ti,AI,Si)N coating with a comparatively high Al content in which the benefits of Si can be enjoyed, the (Ti, Al, Si)N coating having excellent mechanical properties and heat stability.
• the object of the present invention is to provide a coated cutting tool comprising a layer of (Ti, Al, Si)N having improved tool life over prior art coated cutting tools.
• a coated cutting tool comprising a substrate and a coating, wherein the coating comprises a from 0.5 to 15 pm monolithic layer of (Ti, Al, Si)N with an average composition Tii-x-yAlxSi y N, 0.50 ⁇ x ⁇ 0.60, 0.03 ⁇ y ⁇ 0.08, the layer of (Ti, Al, Si)N has a structure of columnar crystal grains, the layer of (Ti, Al, Si)N comprises two different cubic phases, one cubic phase being present in the columnar crystal grains and one cubic phase being a grain boundary phase located between columnar crystal grains, the layer of (Ti, Al, Si)N has a plane strain modulus of > 425 GPa.
• Tii-x-yAlxSiyN suitably 0.52 ⁇ x ⁇ 0.58.
• Tii-x-yAlxSiyN suitably 0.03 ⁇ y ⁇ 0.07, preferably 0.04 ⁇ y ⁇ 0.06.
• the layer of (Ti,AI,Si)N of this disclosure is monolithic, i.e. , substantially uniform in its properties and its elemental contents throughout the (Ti, Al, Si)N layer, in contrast to a multilayered (Ti, AI,Si)N layer.
• the aluminium content x in Tii-x-yAlxSi y N is less than 0.50 then there is insufficient oxidation stabilty and hot hardness giving less performance in metal cutting. If, on the other hand, the aluminium content x in Tii-x-yAlxSi y N is higher than 0.60 then there is a risk of introduction of hexagonal phase within the (Ti, Al, Si)N layer leading to worse mechanical properties such as lower hardness and lower plane strain modulus giving less performance in metal cutting. If the silicon content y in Tii-x-yAlxSi y N is less than 0.03 then there is no, or insufficient amount of, grain boundary phase giving less performance in metal cutting.
• the silicon content y in Tii-x-yAlxSi y N is higher than 0.08 then there is a risk of introduction of hexagonal phase within the (Ti, Al, Si)N layer leading to worse mechanical properties such as lower hardness and lower plane strain modulus giving less performance in metal cutting.
• the determination of crystal structure or structures present in the (Ti, Al, Si)N layer is suitably made by X-ray diffraction analysis, alternatively TEM analysis.
• the FWHM (Full Width at Half Maximum) of a diffraction peak in X-ray diffraction analysis depends on both the degree of crystallinity in the (Ti, Al, Si)N layer and the grain size of crystallites. The smaller the FWHM value, the higher the crystallinity and/or the larger the grain size.
• the (Ti, Al, Si)N layer comprises a cubic crystal structure and wherein the FWHM (Full Width at Half Maximum) of the cubic (200) peak in a theta-2theta scan in X-ray diffraction using Cu k-alpha radiation is from 0.4 to 1 .5 degrees 2theta, preferably from 0.5 to 1 .0 degrees 2theta.
• FWHM Full Width at Half Maximum
• the degree of crystallinity in itself in the (Ti, Al, Si)N layer can be expressed as measured by a peak-to-background ratio in X-ray diffraction analysis.
• the diffraction intensity of every (hkl) peak from a certain crystal structure in a theta-2theta scan is low and its relation to the background intensity is, thus, low.
• Peak-to-background ratio (I max - (background)/ Ibackground.
• the highest peak of a crystal structure is used as Imax in the formula since a crystal structure may be of different preferred crystallographic orientations and the relation between intensities of the different (hkl) peaks in a crystal structure may vary.
• the cubic (200) peak is in one embodiment the one of the cubic peaks showing the highest intensity in an X-ray diffraction theta-2theta scan.
• the (Ti, Al, Si)N layer has a peak-to-background ratio in X-ray diffraction analysis using Cu k-alpha radiation for the cubic (200) peak of > 3, preferably > 4.
• the peak-to-background ratio in X-ray diffraction analysis using Cu k-alpha radiation for the cubic (200) peak of the (Ti, Al, Si)N layer is in combination of any one of the lower limits suitably ⁇ 15, preferably ⁇ 12.
• the columnar crystal grains in the layer of (Ti, Al, Si)N are suitably of single phase cubic crystal structure.
• the grain boundary phase has an average composition Tii- z -vAl z SivN of suitably 0.40 ⁇ z ⁇ 0.55, preferably 0.43 ⁇ z ⁇ 0.52, and suitably 0.06 ⁇ v ⁇ 0.13, preferably 0.07 ⁇ v ⁇ 0.12.
• v/y is >1 but ⁇ 3.5, or v/y is >1 .2 but ⁇ 3, or v/y is >1 .5 but ⁇ 2.5.
• x/z is >1 but ⁇ 1 .5, or x/z is >1 .1 but ⁇ 1 .3.
• the average thickness of the grain boundary phase between columnar crystal grains is from 0.5 to 10 nm, suitably from 1 to 5 nm.
• the (Ti, Al, Si)N layer comprises lattice planes crossing through the columnar crystal grains and the grain boundary phase.
• the cubic phase being present in the columnar crystal grains and the cubic phase being a grain boundary phase there may be a small amount of another phase present in the layer of (Ti, Al, Si)N, such as a hexagonal phase or an amorphous phase.
• Such phases will give a small, broad, diffraction peak in theta-2theta X-ray diffraction covering the range of about 30 to 40 degrees 2theta.
• the peak-to-background ratio in X-ray diffraction analysis using Cu k-alpha radiation for this peak is suitably ⁇ 0.25, preferably ⁇ 0.2, most preferably ⁇ 0.15.
• the (Ti, Al, Si)N layer has a thermal conductivity of ⁇ 5 W/mK, preferably from 2 to 4 W/mK. For wear resistant coatings on cutting tools a low thermal conductivity is beneficial to keep the thermal load from the cutting process on the tool substrate as low as possible.
• the (Ti, Al, Si)N layer has a residual compressive stress of from 1 .5 to 6 GPa, preferably from 2 to 4 GPa. If the residual compressive stress is too low then the toughness of the coating may be insufficient. If, on the other hand, the residual compressive stress is too high then flaking of the coating may occur.
• an innermost layer of the coating directly on the substrate, of a nitride of one or more elements belonging to group 4, 5 or 6 of the periodic table of elements, or a nitride of Al together with one or more elements belonging to group 4, 5 or 6 of the periodic table of elements.
• This innermost layer acts as a bonding layer to the substrate increasing the adhesion of the overall coating to the substrate.
• Such a bonding layer are commonly used in the art and a skilled person would choose a suitable one.
• Preferred alternatives for this innermost layer are TiN or (Ti, AI)N .
• the thickness of this innermost layer may vary and depends, for example, on the type of cutting tool, i.e.
• a coated insert may have another optimal thickness of its innermost layer than a coated drill.
• the thickness of this innermost layer is suitably less than 2 pm.
• the thickness of this innermost layer is in one embodiment from 5 nm to 2 pm, preferably from 10 nm to 1 pm. Since there may also be a need to have an innermost layer functioning as a barrier for Co diffusion into the coating there is a need for the thickness to be at least 50 nm.
• Si-contaning nitride layers are known to attract Co more than most other metal nitride layers.
• this innermost layer is from 50 nm to 2 pm, preferably from 100 nm to 1 pm.
• the (Ti, Al, Si)N layer has a Vickers hardness of > 3500 HV (15 mN load), preferably from 3500 to 3800 HV (15 mN load).
• the (Ti,AI,Si)N layer has suitably a plane strain modulus of from 425 to 540 GPa, preferably from 450 to 530 GPa.
• the thickness of the (Ti,AI,Si)N layer is suitably from 0.5 to 10 pm, preferably from 1 to 6 pm.
• the substrate of the coated cutting tool can be of any kind common in the field of cutting tools for metal machining.
• the substrate is suitably selected from cemented carbide, cermet, cubic boron nitride (cBN), ceramics, polycrystalline diamond (PCD) and high speed steel (HSS).
• the substrate is cemented carbide.
• the coated cutting tool has suitably at least one rake face and at least one flank face and a cutting edge inbetween.
• the coated cutting tool is suitably in the form of an insert, a drill or an end mill.
• the (Ti, Al, Si)N layer according to the invention is suitably a layer deposited by sputtering, preferably a High-Power Impulse Magnetron Sputtering (HIPIMS) - deposited layer.
• HIPIMS High-Power Impulse Magnetron Sputtering
• Figure 1 shows a schematic view of one embodiment of a cutting tool being a milling insert.
• Figure 2 shows a schematic view of a cross section of an embodiment of the coated cutting tool of the present invention showing a substrate and a coating.
• Figure 3 shows a dark-field TEM image of Sample 1 (invention) showing a grain boundary phase visualised as darker areas is seen between columnar crystal grains.
• Figure 4 shows a high-resolution TEM (HR-TEM) dark-field image where one sees lattice planes crossing through the columnar crystal grains as well as the darker grain boundary phase.
• HR-TEM high-resolution TEM
• Figure 5 shows X-ray diffractograms from theta-2theta scans for the (Ti, Al, Si)N layer of Sample 1 (invention) as deposited and after heat treatment at 950°C.
• Figure 6 shows X-ray diffractograms from theta-2theta scans for the (Ti, Al, Si)N layer of Sample 2 (invention) as deposited and after heat treatment at 950°C.
• Figure 7 shows X-ray diffractograms from theta-2theta scans for the (Ti, Al, Si)N layer of Sample 3 (comparative) as deposited and after heat treatment at 950°C.
• Figure 8 shows an X-ray diffractogram from a theta-2theta scan for the (Ti, Al, Si)N layer of Sample 4 (comparative) as deposited.
• Figure 1 shows a schematic view of one 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 in this embodiment a milling insert.
• Figure 2 shows a schematic view of a cross section of an embodiment of the coated cutting tool of the present invention having a substrate body (5) and a coating (6).
• the coating (6) consisting of a first thin (Ti, AI)N innermost layer (8) followed by a (Ti, Al, Si)N layer (7).
• Figure 3 shows a dark-field TEM image of Sample 1 (invention). A structure is seen where bright (9) and dark (10) areas indicate different elemental compositions. The bright areas (9) being columnar crystal grains and the dark areas (10) being a grain boundary phase.
• Figure 4 shows a high resolution transmission electron microscope (HR- TEM) image of an cross-section of an embodiment of the (Ti, Al, Si)N layer.
• the bright areas (9) being columnar crystal grains and the dark areas (10) being a grain boundary phase. It is seen a pattern of stripes from the crystal structure over the whole (Ti, Al, Si)N layer analysed, Thus, lattice planes are crossing through the columnar crystal grains (9) and grain boundary phase (10).
• the X-ray diffraction patterns were acquired by Grazing incidence mode (GIXRD) on a diffractometer from Panalytical (Empyrean). Cu-Ka-radiation with line focus was used for the analysis (high tension 40 kV, current 40 mA).
• the incident beam was defined by a 2 mm mask and a 1/8° divergence slit in addition with a X-ray mirror producing a parallel X-ray beam.
• the sideways divergence was controlled by a Soller slit (0.04°).
• a 0,18° parallel plate collimator in conjunction with a proportional counter (0D- detector) was used for the diffracted beam path a 0,18° parallel plate collimator in conjunction with a proportional counter (0D- detector) was used.
• the 2theta range was about 20-80° with a step size of 0.03° and a counting time of 10 s.
• the Transmission Electron Microscopy data (selected area diffraction patterns and dark field images) was acquired by a Transmission Electron Microscope Joel ARM200F.
• a high tension of 300 kV was used.
• FIB Fluorine Beam
• a cross-section of the coating was analysed perpendicular to surface of the coating.
• Analysis of thickness of the grain boundary phase can be made by image analysis by determining the variation in brightness of the TEM image along an intersecting line. Since the grain boundary phase is dark in the image the thickness can be determined. A sufficient length of and/or number of intersecting lines is/are drawn so to provide a reliable average value of the grain boundary phase thickness. Suitably, at least 20 grain boundaries are intersected and an average value is calculated. Elemental content:
• the content of metal elements, nitrogen and argon in the coating can be measured by using Scanning Transmission Electron Microscopy (STEM) with Energy Dispersive X-Ray Spectroscopy (EDX) on a cross sectional FIB- prepared sample.
• STEM Scanning Transmission Electron Microscopy
• EDX Energy Dispersive X-Ray Spectroscopy
• Jeol ARM System instrument was used, equipped with a field emission gun, secondary electron-dectector and Si(Li) energy dispersive x- ray (EDX) detector from Oxford Instruments. Either using a spot size small enough for probing, e.g., a grain boundary or use STEM mode to get an elemental mapping over a distance in the coating.
• the side-inclination method (MJ-geometry) has been used with eight spangles, equidistant within a selected sin 2l P range. An equidistant distribution of cp-angles wihin a cp-sector of 90° is preferred.
• the Poisson’s ratio 0.20
• the data were evaluated using commercially available software (RayfleX Version 2.503) locating the (2 0 0) reflection of (Ti, Al, Si)N by the Pseudo-Voigt-Fit function.
• a suitable method for the removal of deposited coating material may be polishing, however, gentle and slow polishing using a fine-grained polishing agent should be applied. Strong polishing using a coarse grained polishing agent will rather increase the compressive residual stress, as it is known in the art.
• Other suitable methods for the removal of deposited coating material are ion etching and laser ablation.
• thermoreflectance TDTR
• a laser pulse (Pump) is used to heat the sample locally.
• the heat energy is transferred from the sample surface towards the substrate.
• the temperature on the surface decreases by time.
• the part of the laser being reflected depends on the surface temperature.
• a second laser pulse (probe pulse) is used for measuring the temperature decrease on the surface.
• the samples should be polished into mirror-like finish before the measurement.
• the Vickers hardness was measured by means of nano indentation (load-depth graph) using a Picodentor HM500 of Helmut Fischer GmbH, Sindelfingen, Germany.
• the Oliver and Pharr evaluation algorithm was applied, wherein a diamond test body according to Vickers was pressed into the layer and the force-path curve was recorded during the measurement.
• the maximum load used was 15 mN (HV 0.0015), the time period for load increase and load decrease was 20 seconds each and the holding time (creep time) was 10 seconds. From this curve hardness was calculated.
• the elastic properties of the coating samples were characterized by the so-called plane strain modulus E ps as derived by nanoindentation via the Oliver and Pharr method.
• the nano-indentation data was obtained from indentation as described for Vickers hardness above.
• the thickness of the coating layers was determined by calotte grinding. Thereby a steel ball was used having a diameter of 30 mm for grinding the dome shaped recess and further the ring diameters were measured, and the layer thicknesses were calculated therefrom. Measurements of the layer thickness on the rake face (RF) of the cutting tool were carried out at a distance of 2000 pm from the corner, and measurements on the flank face (FF) were carried out in the middle of the flank face of a polished test sample.
• RF rake face
• FF flank face
• a start layer of (Ti,AI)N was deposited onto WC-Co based substrates using three targets with the composition Tio.4oAlo.6o. Then, a (Ti, Al, Si)N layer was further deposited using three targets with the composition Ti0.40AI0.55Si0.06.
• the WC-Co based substrates were cutting tools being milling inserts of geometry ADMT 160608R-F56, ROHX1204M0-D67, and as well flat inserts (for easier analysis of the coating) using HIPIMS mode in an Oerlikon Balzers Ingenia equipment using S3p technology.
• the substrates had a composition of 8 wt% Co and balance WC.
• the uncoated insert blanks were mounted and rotated in the PVD chamber during deposition of the coating.
• the deposition process was run in HIPIMS mode using the following process parameters
• Target material Ti0.40AI0.60 (three targets)
• Target size circular, diameter 160 mm Thickness: 12 mm
• Peak pulse power 60 kW
• a layer thickness of about 200 nm was deposited.
• Target material Ti0.40AI0.54Si0.06
• Target size circular, diameter 160 mm
• Thickness 12 mm
• Peak pulse power 60 kW
• a (Ti, Al, Si)N layer with a thickness of about 2.5 pm was deposited on the milling inserts, as measured on the flank face of an insert.
• Example 1 The coated cutting tool provided is called “Sample 1 (invention)”.
• Example 2 (invention):
• a further sample within the invention was made in the same way as described in Example 1 with the exception that the target material used in the process for depositing the (Ti,AI,Si)N layer wasTi0.40AI0.56Si0.04 instead of Ti0.40AI0.54Si0.06.
• the WC-Co based substrates were cutting tools being flat inserts (for easier analysis of the coating).
• a (Ti, Al, Si)N layer with a thickness of about 1 .5 pm was deposited on the inserts, as measured on the rake face of an insert.
• the coated cutting tool provided is called “Sample 2 (invention)”.
• the WC-Co based substrates were cutting tools being flat inserts (for easier analysis of the coating).
• a (Ti, Al, Si)N layer with a thickness of about 1 .6 pm was deposited on the inserts, as measured on the rake face of an insert.
• the coated cutting tool provided is called “Sample 3 (comparative)”.
• a (Ti, Al, S i)N layer from a target with the composition Tio.35Alo.55Sio.1o was deposited onto WC-Co based substrates of a milling insert type ADMT 160608R-F56 as well as flat cutting inserts (for easy analysis of the coating).
• the substrates had a composition of 8 wt% Co and balance WC.
• the uncoated insert blanks were mounted and rotated in the PVD chamber during deposition of the coating.
• Target material 2 Tio.35Alo.55S io.i 0
• Target size circular, diameter 150 mm
• Peak pulse power 30 kW
• a (Ti, Al, Si)N layer with a thickness of about 2.5 m was deposited on the milling inserts, as measured on the flank face of an insert.
• the coated cutting tool provided is called “Sample 4 (comparative)”.
• a (Ti, Al, S i)N layer from a target with the composition Ti0.40AI0.54Si0.06 was deposited onto WC-Co based substrates of a milling insert with SPMW12 geometry as well as flat cutting inserts (for easy analysis of the coating).
• the substrates had a composition of 8 wt% Co and balance WC.
• the uncoated insert blanks were mounted and rotated in the PVD chamber during deposition of the coating.
• the deposition was made using cathodic arc deposition in an Hauzer HTC1000 equipment using the following process parameters:
• Target material Ti0.40AI0.60
• Target size circular, diameter 104 mm
• a layer thickness of about 340 nm was deposited.
• Target material Ti0.40AI0.54Si0.06
• Target size circular, diameter 104 mm
• a (Ti, Al, Si)N layer with a thickness of about 2.5 pm was deposited on the milling inserts, as measured on the flank face of an insert.
• the coated cutting tool provided is called “Sample 5 (comparative)”.
• a (Ti , Al )N layer from a target with the composition Ti0.40AI0.60 was deposited onto WC-Co based substrates being cutting tools of a milling insert type ROHX1204M0-D67 and as well flat inserts (for easier analysis of the coating) using HIPIMS mode in an Oerlikon Balzers equipment using S3p technology.
• This HIPIMS-deposited coating was known to give very good results in machining of stainless steel (ISO-M) materials.
• the substrates had a composition of 8 wt% Co and balance WC.
• the uncoated insert blanks were mounted and rotated in the PVD chamber during deposition of the coating.
• the deposition process was run in HIPIMS mode using the following process parameters
• Target material 1 Ti0.40AI0.60 Target size: circular, diameter 160 mm
• Peak pulse power 60 kW
• a (Ti, Al, Si)N layer with a thickness of about 2.5 pm was deposited on the milling inserts, as measured on the flank face of an insert.
• the coated cutting tool provided is called “Sample 6 (comparative)”.
• Figures 5-8 show the XRD theta-2theta d iff ractog rams for Sample 1 (invention), Sample 2 (invention), Sample 3 (comparative) and Sample 4 (comparative).
• the diffractograms for Sample 1 (invention) and Sample 2 (invention) reveal a cubic crystal structure.
• the diffractograms show significant cubic (111 ) and cubic (200) peaks at around 37-38 degrees 2theta and around 43-44 degrees 2theta, respectively.
• the peaks are also quite sharp which implies significant crystallinity.
• the peak with the highest intensity is the (200) peak.
• the peak-to-background ratio for the (200) peak is estimated to be about 5.0 for Sample 1 (invention) and about 8.1 for Sample 2 (invention).
• the FWHM (Full Width at Half Maximum) of the cubic (200) peak is about 0.8 degrees 2theta for Sample 1 (invention) and about 0.6 degrees 2theta for Sample 2 (invention).
• the diffractogram for Sample 4 (comparative) shows much less significant cubic (111) and cubic (200) peaks than Sample 1 (invention) and Sample 2 (invention).
• the (111 ) peak can hardly be distinguished from a broad underlying reflection which ranges from about 31-39 degrees 2theta. There is also a broad underlying reflection ranging from about 40-45 degrees 2theta which covers the position where the cubic (200) peak is. These broad reflections implies presence of significant amorphous structure.
• the much lower degree of crystallinity can be determined from the peak-to-background ratio for the (200) peak which is only estimated to be about 0.3.
• the Full Width at Half Maximum (FWHM) of this less significant cubic (200) peak is quite difficult to determine but is estimated to be about 4 degrees 2theta.
• the average content of each metal element in the (Ti, Al, Si)N layer is considered to reflect the target composition, i.e. , the layers desposited are regarded as seen in Table 1 .
• the average elemental content of Ti, Al and Si in the grain boundary phase of Sample 1 was Ti: 43 at%, Al: 46 at% and Si: 11 at%.
• the thickness of the grain boundary phase was estimated from TEM analysis to be about 2 nm.
• Residual stress was also measured on Sample 1 (invention) and Sample 2 (invention) showing values of between -2 to -3 GPa for as-deposited samples. Heat treatments were further made at 950°C for a period of one hour and there was no significant relaxation, i.e. , reduction of residual stress, seen which indicates no substantial formation of hexagonal phase. Table 2.
• the phase stability was, furthermore, determined through XRD measurements for samples having been heat treated at 950°C for one hour.
• the cubic (200) peak at about 42-43 degrees 2theta Sample 1 (invention) and Sample 2 (invention) showed only small changes in the (200) peak shape. See Fig. 5 and Fig. 6.
• Sample 3 (comparative) showed a significant broadening of the (200) peak, see Fig. 7, which indicates reduced crystallinity and/or other changes in the structure.
• Sample 3 (comparative) is less heat stable than Sample 1 (invention) and Sample 2 (invention).
• the thermal conductivity was determined using the Time-domain thermoreflectance (TDTR) method. Table 3 shows the results.
• Sample 1 (invention) was 3.1 W/mK, i.e. , a low thermal conductivity, despite the cubic columnar structure, giving an advantage in heat generating severe metal cutting.
• Hardness measurements (load 15 mN) were carried out on the coated tool of Samples 1-5 to determine Vickers hardness and plane strain modulus. Table 4 shows the results. Table 4.
• Sample 1 (invention) performs better than Sample 4 (comparative).
• Sample 1 (invention) and Sample 6 (comparative), being milling inserts of type ROHX1204M0-D67, were tested in a milling test, and the average flank wear was measured.
• the cutting conditions are summarized in Table 7. As workpiece material stainless steel ISO-M was used. Cutting conditions:
• Sample 1 (invention) performs better than Sample 6 (comparative).
• Sample 1 (invention) performs better than Sample 5 (comparative).

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• 2023
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