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WO2025186329A1 - High performance coated tools for machining of carbon steel and alloyed steel - Google Patents

High performance coated tools for machining of carbon steel and alloyed steel

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Publication number
WO2025186329A1
WO2025186329A1 PCT/EP2025/056015 EP2025056015W WO2025186329A1 WO 2025186329 A1 WO2025186329 A1 WO 2025186329A1 EP 2025056015 W EP2025056015 W EP 2025056015W WO 2025186329 A1 WO2025186329 A1 WO 2025186329A1
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WO
WIPO (PCT)
Prior art keywords
nano
type
layer
layers
coating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2025/056015
Other languages
French (fr)
Other versions
WO2025186329A8 (en
Inventor
Volker Derflinger
Denis Kurapov
Derya KAYA BUERZLE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Oerlikon Surface Solutions AG Pfaeffikon
Original Assignee
Oerlikon Surface Solutions AG Pfaeffikon
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Application filed by Oerlikon Surface Solutions AG Pfaeffikon filed Critical Oerlikon Surface Solutions AG Pfaeffikon
Publication of WO2025186329A1 publication Critical patent/WO2025186329A1/en
Publication of WO2025186329A8 publication Critical patent/WO2025186329A8/en
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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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
    • 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
    • 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
    • C23C14/02—Pretreatment of the material to be coated
    • C23C14/024—Deposition of sublayers, e.g. to promote adhesion of the coating
    • 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
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/0641—Nitrides
    • C23C14/0647—Boron nitride
    • 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
    • C23C14/0676—Oxynitrides
    • 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
    • C23C14/24—Vacuum evaporation
    • C23C14/32—Vacuum evaporation by explosion; by evaporation and subsequent ionisation of the vapours, e.g. ion-plating
    • C23C14/325—Electric arc evaporation
    • 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
    • C23C28/40—Coatings including alternating layers following a pattern, a periodic or defined repetition
    • C23C28/42—Coatings including alternating layers following a pattern, a periodic or defined repetition characterized by the composition of the alternating layers

Definitions

  • the present invention relates to a nanolaminated coating structure suitable for producing coated tools exhibiting outstanding high performance in cutting operations of the type machining of carbon steel and machining of alloyed steel and a coating system using this nanolaminated structure, in particular a high performance coated tool for machining of carbon steel and alloyed steel.
  • the present invention relates even to a method for producing the inventive coating system and for producing coated tools comprising said inventive coating system.
  • Arndt describes in WO 2013/000557 A1 a coating system for cutting tools having a nanolaminated coating structure of alternating A and B layer, the A layers having chemical element composition (Al x Tii- x -yWy)N, with 0.50 ⁇ x ⁇ 0.65 and 0 ⁇ y ⁇ 0.10, and the B layers having chemical element composition (Tii- z -uSizW u )N, with 0.05 ⁇ z ⁇ 0.30 and 0 ⁇ u ⁇ 0.10, wherein the nanolaminated structure of alternating A and B layers exhibits a fine-grained structure.
  • the main objective of the present invention is to provide a coating solution for producing coated tools that allow attaining a highly improved tool performance in machining operations of the type machining of carbon steel and machining of alloyed steel in comparison to the state of the art.
  • the nanolaminated coating structure consists of a nano-layered architecture formed of nano-layers.
  • the nano-layered architecture comprises multiple nano-layers of type A and multiple nano-layers of type B which are alternately deposited (...A/B/A/B/A... ) and form a so- called A/B-layer.
  • a nano-layer in the context of the present invention is a layer having a layer thickness of maximal 200 nm, preferably lower than 200 nm, preferably between 5 nm and 200 nm, more preferably between 10 nm and 150 nm.
  • the nano-layers of type A are formed containing nitrogen (N), aluminium (Al), titanium (Ti), chromium (Cr) and optionally one or more dopants.
  • the nano-layers of type B are formed containing nitrogen (N), titanium (Ti), silicon (Si) and optionally one or more dopants.
  • Dopants in the context of the present invention are chemical elements from the periodic table group 4a, 5a and 6a that are different from the above-mentioned chemical elements contained in the A and B layers, respectively.
  • Preferred dopants in the context of the present invention are boron (B) and tantalum (Ta) for the nano-layers of type A and chromium (Cr) for the nano-layers of type B.
  • nanolaminated coating structure As used undifferentiated in the context of the present invention and have the same meaning.
  • nano-layered coating system or “coated body’ refers to a “nanolaminated coating structure” provided on a surface of a substrate.
  • the coating system and deposition method according to the present invention are especially suitable for manufacturing high-performance tools for machining carbon steel and machining alloyed steel compared to the state of the art.
  • the coating system according to the present invention is particularly suitable for manufacturing coated cutting tools, however, said inventive coating system can be also used for manufacturing other kinds of coated substrates.
  • the coating system according to the present invention can be used for example for manufacturing high performance solid carbide drills, cutting inserts and endmills which allow a higher productivity in automotive applications such as carbon steel, alloyed steel and cast-iron machining compared to the state of the art.
  • the newly developed coating system is primarily used for cutting application especially in drilling applications of carbon and alloyed steels, such as C45/C50 DIN 1.1191 as well as SCM440/AISI4140/DIN1.7225, etc.
  • the nanolaminated coating structure preferably exhibits a columnar fine-grained structure.
  • a nano-bilayer period will be defined as the sum of the thickness of two nano-layers, respectively one nano-layer of type A and one nano-layer of type B, which are deposited one of each repeatedly (at least two times).
  • nanolaminated coating structure is characterized by having essentially nano-bilayer periods less than 300 nm.
  • the coating system comprises at least three layers:
  • a D-layer comprising titanium, silicon and nitrogen, wherein a combined thickness of both the C-layer and the D-layer does not exceed 30% of a total coating thickness, and the A/B-layer is directly deposited on the C-layer and the D-layer is directly deposited on the A/B-layer.
  • a preferred embodiment of the, coating structure according to the present invention comprises nano-layers of type A and B, respectively having an element composition according to the following formulas:
  • Nano-layer A (AlxTii-x-g-yCr g Me 1 y)N with x and y in at.% and where
  • Nano-layer B (Tii-z-uSi z Me 2 u)N with z and u in at.% and where 0.05 ⁇ z ⁇ 0.30 and 0 ⁇ u ⁇ 0.20, where Me 2 represents chemical element selected from group 4a, 5a and 6a and boron.
  • a preferred embodiment of the coating structure according to the present invention comprises at least four or preferably at least ten individual nano-layers, respectively at least two nano-layers of type A and two nano-layers of type B or preferably at least five nano-layers of type A and five nano-layers of type B, wherein the nano-layers of type A and the nano-layer of type B are deposited alternately, i.e. each one nano-layer of type A is deposited on each corresponding one nano-layer of type B and/or each one nano-layer of type B is deposited on each corresponding one nanolayer of type A.
  • the hard coating structure preferably comprises a quantity n of nano-layers of type A, respectively Ai, A2, A3, ... A n , and a quantity m of nano-layers of type B, respectively Bi , B2, B3, ... B m , the thickness of the nano-layers of type A is denoted as dA, respectively dAi, dA2, dAs, ... dA n , and the thickness of the nano-layers of type B is denoted as dB, respectively dBi, dB2, dBs, ... dB m .
  • the thickness of the nano-layers of type A is equal or smaller than the thickness of the nano-layers of type B and the thickness of the individual nano-layers A and the thickness of the individual nano-layers B vary along the total coating thickness: dA ⁇ dB, respectively dA n ⁇ dB m , such that a) dAi > dA2 dAs > ... dA n and dBi > dB2 dBs ⁇ ... dB m , or b) dAi ⁇ dA2 dAs ⁇ ... dA n and dBi ⁇ dB2 dBs ⁇ ...
  • At least one portion of the total coating thickness comprises nano-layers of type A and nano-layers of type B deposited according to a) and at least one portion of the total coating thickness comprises nano-layers of type A and nano-layers of type B deposited according to b).
  • a hard nano-layered coating system for manufacturing high-performance tools comprises a substrate having a substrate surface and a nanolaminated coating structure according as described above, wherein the nanolaminated coating structure is deposited on the substrate surface.
  • the present invention relates to a coated body comprising a substrate and a coating onto the substrate, the coating having a nanolaminated coating structure consisting of a nano-layered architecture formed of nanolayers, wherein the nanolayered architecture comprises alternately deposited nanolayers of type A and type B (...A/B/A/B/A... ), wherein the A nanolayers have a chemical element composition given by the formula (AlxTii-x-g-yCr g Me 1 y)N, and the B nanolayers have a chemical element composition given by the formula (Tii-z-uSi z Me 2 u)N, wherein Me 1 and Me 2 are the dopants in the A and B nanolayers, respectively.
  • Me 1 can be equal to or different from Me 2 .
  • the coefficients y and u corresponding to the concentration of Me 1 and Me 2 can be zero because the use of the dopants Me 1 and Me 2 in the inventive coating is optional as mentioned above.
  • the C-layer is deposited closer to the substrate than the A/B-layer and the A/B-layer is deposited closer to the substrate than the D-layer.
  • the C-layer can be deposited directly on the substrate surface.
  • a coating method for depositing the coating structure on a substrate surface of a substrate comprises the steps: forming an A/B-layer by alternatingly depositing a nano-layer of type A and a nano-layer of type B multiple times on the substrate surface using a PVD technique, wherein the nano-layer of type A contains nitrogen (N), aluminium (Al), titanium (Ti) and chromium (Cr), and the nano-layer of type B contains nitrogen (N), titanium (Ti) and silicon (Si).
  • the above-described coating method further comprises the steps: depositing a C-layer comprising titanium, aluminium, chromium and nitrogen directly on the substrate surface, and depositing a D-layer comprising titanium, silicon and nitrogen directly on the A/B-layer.
  • the coating method preferably uses arc ion deposition for depositing the coating structure on the substrate surface of the substrate with the following coating parameters: a N2-pressure pN2 within a range: 4 Pa ⁇ pN2 7 Pa, a DC substrate bias-voltage VDC within range: -20 V ⁇ VDC -60 V (negative bias voltage), and a temperature T within a range: 400°C ⁇ T ⁇ 550°C.
  • Further enhancement of the effectiveness of the inventive coating can be attained by using one or more of following process steps: a) Subjecting the substrate or substrate surface to be coated to a specific pretreatment, b) Subjecting the coating system after deposition to a specific post-treatment, c) Adding one or more further layer to the coating system.
  • Figure 1 a and 1 b show schematically the coating architecture of coating systems according to the present invention.
  • Figure 2 shows the results of a cutting test 1 .
  • Figure 3 shows the results of a cutting test 2.
  • Figure 4 shows a fractured cross-section scanning electron micrographs of an inventive coating system.
  • the nanolaminated coating structure 5 relates to a multilayer coating system which includes nano-layers of type A and nano-layers of type B deposited alternately one on each other and forming an A/B-layer.
  • the nano-layers of type A containing aluminium, Al, titanium, Ti, chromium Cr and nitrogen, N
  • the nano-layers of type B containing titanium, Ti, silicon, Si, and nitrogen, N.
  • At least some nano-layers of type A and/or at least some nano-layers of type B include additionally further elements, for example in the A layers additionally tantalum Ta and or boron B, and/or for example in the layer B additionally chromium Cr.
  • Each nano-layer of type A or B included in the hard nano-layered coating system according to the present invention having fundamentally a maximal individual layer thickness less than 200 nm.
  • the architecture of a hard nano-layered coating system according to the present invention can include in addition an interlayer (referenced as 2 in Fig. 1a or as C-layer in Fig. 1 b) between the substrate (referenced as 1 in Fig. 1 a or as substrate in Fig. 1 b) and the nanolaminated coating structure composed of the alternated nano-layers A and nano-layers B (referenced as 5 in Fig. 1 a and as A/B-layer in Fig. 1 b).
  • the thickness and composition of the interlayer is to be selected for example in order to influence the texture of the hard nano-layered coating system and to attain reduced stress in coating.
  • a top layer (referenced as 3 in Fig. 1 a and as D-layer in Fig. 1 b)) can also be deposited on the last layer of the coating structure 5 composed of the alternated nano-layers A and nano-layers B as it is drawn in Fig. 1 a, or it can be only a single top layer having for example the same or similar chemical element composition like the layers B (i.e. same or similar chemical element composition like the nanolayers B).
  • an interlayer 2 (or C-layer in Fig. 1 b) consisting of AITiCrN having the same Al, Ti and Cr concentration ratio as the A nano-layers which are part of the coating structure.
  • a top-layer 3 (or D-layer in Fig. 1 b) is the outermost layer and is deposited on the last layer of the nano-layers of the nanolaminated A/B/A/B/A/B... structure of the coating system, and is composed of the same chemical composition as either layer A or layer B.
  • the (AlxTii-x-g-yCr g Me 1 y)N/(Tii-z-uSizMe 2 u)N coatings according to the present invention were deposited on high performance solid carbide drills using PVD techniques. More exactly the coatings were deposited by means of arc ion plating deposition methods at an INNOVENTA coating machine of the company Oerlikon Balzers. Especially suitable coating parameters for the deposition of the coatings according to the present invention were: N2-Pressure pN2: 4 - 7 Pa
  • Another important aspect of the present invention is the significant influence of the kind of arc-evaporator used for the coating deposition.
  • the coatings according to the present invention exhibit also superior performance by cutting tests than state of the art coatings as it is shown in Fig. 2 and Fig. 3.
  • FIG. 4 correspond to fractured cross-section scanning electron micrographs of two coating systems deposited according to the present invention and comprising a nanolaminated coating structure 5 of alternating A and B layers, where the layers A are AITiCrN layers and the layers B are TiSiN nano-layers, respectively, and having a bilayer period (the sum of the thickness of one A layer and one B layer deposited alternately one on each other at least two times i.e. at least forming a A/B/A/B or B/A/B/A structure) of approximately 50 nm or less.
  • the produced nanolaminated coating structures exhibiting a fine-grained structure according to the present invention are in particular more advantageous for prevention of crack propagation than similar coatings exhibiting a columnar structure. It can be caused by the difference in the distribution of the grain boundary or crystal boundary in the nanolaminated structure.
  • the crystals grow as columns in parallel having consequently a long crystal boundary which extends to the substrate across the coating thickness facilitating the crack propagation along the coating thickness in direction to the substrate and consequently resulting in a faster coating delamination or coating failure.
  • a fine-grained structure like it is produced according to the present invention, comprises fine grains whose crystal boundary or grain boundary doesn’t extend to the substrate across the coating thickness and consequently stopping the crack propagation along the coating thickness in direction to the substrate.
  • the fine-grained structures exhibited by the nanolaminated coating structure formed according to the present invention show particularly better cutting performance during drilling and milling operations in relation to life time, fatigue resistance, crater wear resistance, fracture toughness and oxidation resistance than columnar structures.
  • Example of an inventive coating system Example of an inventive coating system:
  • the inventive coating shown in Fig. 4 comprises a nanolaminated coating structure of alternating AITiCrN and TiSiN nano-layers, the overall nanolaminated coating structure having average composition in atomic percentage of 24.4% Ti, 12.1 % Al, 3.8% Cr, 1.1 % Si and 58.6% N, measured by energy dispersive x-ray spectroscopy.
  • the bilayer period was less than 50 nm.
  • the inventive coating was deposited by arc PVD techniques using powder metallurgical composite TiAICr-targets having a composition in atomic percentage of 40% Al /50% Ti 1 10% Cr for the deposition of the TiAICrN-layers and melt metallurgical composite TiSi-targets having a composition in atomic percentage of 85% Ti /15% Si for the deposition of the TiSiN-layers.
  • the nanolaminated structure of alternating nano-layers A and B exhibit an average residual stress, o, between 2 and 4 GPa, preferably between 2.5 and 3.5 GPa. These recommended values of residual stress can be particularly advantageously for drilling and milling operations.
  • the targets used as source material would be preferably AITiCrMe 1 -targets and TiSiMe 2 -targets, respectively.
  • Example 1 of coating deposition according to the present invention :
  • the inventive coating was deposited comprising a nanolaminated coating structure of AITiCrN/TiSiN coating nanolayers having a bilayer period (thickness of two nanolayers AICrN and TiSiN directly next to each other) of about 5-30 nm were deposited on high performance solid carbide drills 0 8.5 mm at a coating machine of the company Oerlikon Balzers of the type INNOVENTA by following coating conditions:
  • Targets having an element composition of Alo.4Tio.5Cro.i and Tio.85Sio.15 were used respectively for the deposition of the AITiN and TiSiN nano-layer.
  • the material source targets were evaporated using arc evaporators of the type proposed by Krassnitzer et al. in patent document WO2010088947.
  • the arc evaporators were adjusted as follow the internal (centric) permanent magnet was positioned in front (front) in relation to the target and the outside permanent magnets were positioned at a distance of 4 mm in relation to the target.
  • the arc evaporators were operated setting a coil current of 0.9 A and an arc current of 180 A.
  • the arc evaporators were adjusted as follow the internal (centric) permanent magnet was positioned in front (front) in relation to the target and the outside permanent magnets were positioned at a distance of 48 mm in relation to the target.
  • the arc evaporators were operated setting a coil current of 0.9 A and an arc current of 200 A.
  • Coated cutting tools were post-treated after coating using different mechanical methods in order to improve surface quality.
  • Fig. 2 shows the results obtained by cutting test 1 , which was carried out with coated solid carbide drills 0 8.5 mm by the following cutting parameters:
  • Fig. 3 shows the results obtained by cutting test 2, which was carried out with coated solid carbide drills 0 8.5 mm by the following cutting parameters:
  • AITiCrN/TiSiN coatings having a bilayer period of about 8-15 nm were deposited on high performance solid carbide drills 0 8.5 mm at a coating machine of the company Oerlikon Balzers of the type Innova by following coating conditions:
  • Targets having an element composition of Alo.4Tio.5Cro.i and Tio.85Sio.15 were used respectively for the deposition of the AITiCrN and TiSiN nano-layer.
  • the material source targets were evaporated using arc evaporators of the same type as those described in example 1 .
  • the internal permanent magnet was also positioned rear in relation to the targets, while the outside permanent magnets were positioned respectively at a distance of 8 mm and 10 mm from the TiAICr- and TiSi-targets.
  • the arc evaporators for the evaporation of the TiAICr- and TiSi-targets were operated respectively setting coil currents of 0.9 A and arc current of 200 A for both target types.
  • Example 3 of coating deposition according to the present invention is a diagrammatic representation of Example 3 of coating deposition according to the present invention.
  • AITiCrTaN/TiSiBN coatings having a bilayer period of about 5-30 nm were deposited on high performance solid carbide drills 0 8.5 mm at a coating machine of the company Oerlikon Balzers of the type Innova by following coating conditions:
  • Targets having an element composition of Alo.35Tio.5Cro.1Tao.o5 and Ti0.80Si0.15B0.05 were used respectively for the deposition of the AITiCrTaN and TiSiN nano-layer.
  • the material source targets were evaporated using arc evaporators of the same type used in examples 1 and 2.
  • the arc evaporators were operated by same parameters than those used in example 1 .
  • coating structures according to the present invention which exhibit coatings hardness values of about 36 - 50 GPa and Young’s modulus values of about 350 - 450 GPa. Both coating hardness and Young’s modulus values were measured using nanoindentation technigues. Furthermore, the coatings deposited according to the present invention exhibit a texture intensity 200/100 > 10 determined by X-ray examinations.
  • layer A is (Al x Tii- x - y Wy)N, with 0.50 ⁇ x ⁇ 0.65 and 0 ⁇ y ⁇ 0.10, where the coefficients given by x, 1 -x-y and y correspond to the atomic concentration of aluminium, titanium and tungsten, respectively, considering only the elements aluminium, titanium and tungsten for the element quantification in the layer A, and where layer B is (Tii-z-uSizWu)N, with 0.05 ⁇ z ⁇ 0.30 and 0 ⁇ u ⁇ 0.10, where the coefficients given by 1-z-u, z and u correspond to the atomic concentration of titanium, silicon and tungsten, respectively, considering only the elements titanium, silicon and tungsten for the element quantification in said layer B, with a thickness of the nanolaminated coating structure between 0.01 and 30 pm, preferably between 1 and 15 pm, an average individual thickness of the A and B layers is between 1 and 200 nm, respectively,
  • the thickness of the A layers (A1 , A2, A3, ... An), referred to as dA1 , dA2, dA3... dAn, is equal or smaller than the thickness of the B layers (B1 , B2, B3,... Bm), referred to as dB1 , dB2, dB3... dBm, comprised in the nanolaminated coating structure of alternating A and B layers, preferably the thickness of the A layers is equal or smaller than % of the thickness of the B layers: dA1 ⁇ % dB1 , dA2 ⁇ % dB2, dA3 ⁇ % dB3, dAn ⁇ % dBm.
  • the thickness of the A layers and/or the thickness of the B layers decreases, so that dA1 ⁇ dA2 ⁇ dA3... ⁇ dAn and/or dB1 ⁇ dB2 ⁇ dB3... ⁇ dBm.
  • nanolaminated coating structure comprised in the coating of a coated body as mentioned above:
  • the sum of the thicknesses of a nano-layer of type A and a nano-layer of type B deposited alternately one on each other forming a nano-bilayer period is less than 300 nm, preferably less than 100 nm, more preferably between 5 and 50 nm, and
  • said nanolaminated coating structure comprises at least a total of four individual nanolayers A and B deposited alternately one on each other forming a A1/B1/A2/B2/ or B1/A1/B2/A2 multilayer architecture, preferably at least a total of ten individual nanolayers forming a A1/B1/A2/B2/A3/B3/A4/B4/A5/B5 or B1/A1/B2/A2/B3/A3/B4/A4/B5/A5 multilayer architecture.
  • nanolaminated coating structure comprised in the coating of a coated body as mentioned above:
  • the nanolaminated coating structure features a fine-grained structure comprising grains whose largest size is 1/3 of the overall thickness of the nanolaminated coating structure.
  • the nanolaminated structure features a fine-grained structure comprising grains having an average size of maximal 1000 nm, preferably between 10 and 800 nm, more preferably between 10 and 400 nm.
  • the nanolaminated coating structure comprised in the coating of the coated body mentioned before can be or can comprise an equiaxed structure in which the grains have approximately the same dimensions in all directions.
  • the coating structure comprises:
  • interlayer 2 or C-layer in Fig. 1b deposited between the substrate 1 and said nanolaminated coating structure (orA/B-layer in Fig. 1b), and/or
  • the coated body according to the present invention is a drilling or a milling tool.
  • the coated body according to the present invention is used for drilling or milling operations, more preferably for drilling of steel, stainless steel, or cast iron or milling of hardened steel or stainless steel.
  • a preferred method for manufacturing a coated body according to the present invention is an arc PVD method characterized by the use of at least one arc vaporization source for the deposition of the nano-layered coating structure on the substrate surface, wherein the at least one arc vaporization source comprises a magnetic field arrangement provided on a target for generating magnetic fields on and above the target surface, wherein the magnetic field arrangement comprises marginal permanent magnets and at least one ring coil placed behind the target, whose inner diameter defined by the windings is smaller than or equal to, and in any case not considerably larger than the diameter of the target, and the marginal permanent magnets can be displaced away from the target essentially perpendicularly to the surface of the target and the projection of the marginal permanent magnets onto the target surface is further away from the middle of the target surface by comparison to the projection of the ring coil onto the target surface, the inner or internal, centric permanent magnet is positioned at the same level in relation to the target as the outer or outside permanent magnet.
  • Both rings are positioned at a distance of several millimeters in relation to the target, preferably between 0 and 10 mm, more preferably ca. 4 mm.
  • a negative coil current is applied, the applied coil current is preferably between 0.5 and 1 .4 A.
  • the method applied for the deposition of nanolaminated coating structures according to the present invention comprises the use as source coating material of:
  • At least one composite target made by means of powder-metallurgical techniques, comprising aluminium and titanium and/or tungsten are used for the deposition of the nano-layer of type A, and/or
  • At least one composite target made by means of melt-metallurgical techniques, comprising titanium and silicon and/or tungsten are used for the deposition of the nanolayer of type B.

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Abstract

A nanolaminated coating structure is provided, the nanolaminated coating structure consisting of a nano-layered architecture formed of nano-layers. The nano-layered architecture comprises multiple nano-layers of type A and multiple nano-layers of type B alternately deposited and forming an A/B-layer (5), wherein the nano-layers of type A contain nitrogen (N), aluminium (Al), titanium (Ti) and chromium (Cr), and the nano-layers of type B contain nitrogen (N), titanium (Ti) and silicon (Si).

Description

High Performance Coated Tools for machining of carbon steel and alloyed steel
The present invention relates to a nanolaminated coating structure suitable for producing coated tools exhibiting outstanding high performance in cutting operations of the type machining of carbon steel and machining of alloyed steel and a coating system using this nanolaminated structure, in particular a high performance coated tool for machining of carbon steel and alloyed steel.
The present invention relates even to a method for producing the inventive coating system and for producing coated tools comprising said inventive coating system.
State of the art
Arndt describes in WO 2013/000557 A1 a coating system for cutting tools having a nanolaminated coating structure of alternating A and B layer, the A layers having chemical element composition (AlxTii-x-yWy)N, with 0.50 < x < 0.65 and 0 < y <0.10, and the B layers having chemical element composition (Tii-z-uSizWu)N, with 0.05 < z < 0.30 and 0 < u <0.10, wherein the nanolaminated structure of alternating A and B layers exhibits a fine-grained structure.
This coating system in in WO 2013/000557 A1 has shown especially good results in drilling operations. However, for meeting the permanent increasing demands, further improvements are required, especially for attaining a highly improved tool performance in machining operations of the type machining of carbon steel and machining of alloyed steel.
Objective of the present invention
The main objective of the present invention is to provide a coating solution for producing coated tools that allow attaining a highly improved tool performance in machining operations of the type machining of carbon steel and machining of alloyed steel in comparison to the state of the art.
Description of the present invention The main objective of the present invention is attained by providing a nanolaminated coating structure with the features of claim 1 , a coating system with the features of claim 10 and a method with the features of claim 13 to deposit a nanolaminated coating structure on a substrate surface. Preferred embodiments are given in the dependent claims.
The nanolaminated coating structure consists of a nano-layered architecture formed of nano-layers.
The nano-layered architecture comprises multiple nano-layers of type A and multiple nano-layers of type B which are alternately deposited (...A/B/A/B/A... ) and form a so- called A/B-layer.
A nano-layer in the context of the present invention is a layer having a layer thickness of maximal 200 nm, preferably lower than 200 nm, preferably between 5 nm and 200 nm, more preferably between 10 nm and 150 nm.
The nano-layers of type A (hereafter also simply called A layers or A nanolayers) are formed containing nitrogen (N), aluminium (Al), titanium (Ti), chromium (Cr) and optionally one or more dopants.
The nano-layers of type B (hereafter also simply called B layers or B nanolayers) are formed containing nitrogen (N), titanium (Ti), silicon (Si) and optionally one or more dopants.
Dopants in the context of the present invention are chemical elements from the periodic table group 4a, 5a and 6a that are different from the above-mentioned chemical elements contained in the A and B layers, respectively.
Preferred dopants in the context of the present invention are boron (B) and tantalum (Ta) for the nano-layers of type A and chromium (Cr) for the nano-layers of type B.
The terms “nanolaminated coating structure”, “nanolaminated structure” and “nanolayered structure” are used undifferentiated in the context of the present invention and have the same meaning. The term “nano-layered coating system” or “coated body’ refers to a “nanolaminated coating structure” provided on a surface of a substrate.
The coating system and deposition method according to the present invention are especially suitable for manufacturing high-performance tools for machining carbon steel and machining alloyed steel compared to the state of the art.
The coating system according to the present invention is particularly suitable for manufacturing coated cutting tools, however, said inventive coating system can be also used for manufacturing other kinds of coated substrates.
The coating system according to the present invention can be used for example for manufacturing high performance solid carbide drills, cutting inserts and endmills which allow a higher productivity in automotive applications such as carbon steel, alloyed steel and cast-iron machining compared to the state of the art.
The newly developed coating system is primarily used for cutting application especially in drilling applications of carbon and alloyed steels, such as C45/C50 DIN 1.1191 as well as SCM440/AISI4140/DIN1.7225, etc.
For this kind of applications, a highly wear resistant coating which can be used in broad range of cutting speeds and having a good chip evacuation is needed.
The nanolaminated coating structure preferably exhibits a columnar fine-grained structure.
Within the present invention, a nano-bilayer period will be defined as the sum of the thickness of two nano-layers, respectively one nano-layer of type A and one nano-layer of type B, which are deposited one of each repeatedly (at least two times).
It was determined that coating structures as described above but having nano-bilayer periods of about 300 nm or more exhibit a markedly inferior cutting performance. Hence a preferred embodiment of the nanolaminated coating structure according to the present invention is characterized by having essentially nano-bilayer periods less than 300 nm.
According to a preferred embodiment of a coating structure according to the present invention, the coating system comprises at least three layers:
- a C-layer comprising titanium, aluminium, chromium and nitrogen, and
- a D-layer comprising titanium, silicon and nitrogen, wherein a combined thickness of both the C-layer and the D-layer does not exceed 30% of a total coating thickness, and the A/B-layer is directly deposited on the C-layer and the D-layer is directly deposited on the A/B-layer.
Further, a preferred embodiment of the, coating structure according to the present invention comprises nano-layers of type A and B, respectively having an element composition according to the following formulas:
• Nano-layer A: (AlxTii-x-g-yCrgMe1y)N with x and y in at.% and where
0.20 < x < 0.50, 0.05 < g < 0.30 and 0 < y < 0.20, where Me1 represents chemical element selected from group 4a, 5a and 6a and boron.
• Nano-layer B: (Tii-z-uSizMe2u)N with z and u in at.% and where 0.05 < z < 0.30 and 0 < u < 0.20, where Me2 represents chemical element selected from group 4a, 5a and 6a and boron.
Further, a preferred embodiment of the coating structure according to the present invention comprises at least four or preferably at least ten individual nano-layers, respectively at least two nano-layers of type A and two nano-layers of type B or preferably at least five nano-layers of type A and five nano-layers of type B, wherein the nano-layers of type A and the nano-layer of type B are deposited alternately, i.e. each one nano-layer of type A is deposited on each corresponding one nano-layer of type B and/or each one nano-layer of type B is deposited on each corresponding one nanolayer of type A.
The hard coating structure preferably comprises a quantity n of nano-layers of type A, respectively Ai, A2, A3, ... An, and a quantity m of nano-layers of type B, respectively Bi , B2, B3, ... Bm, the thickness of the nano-layers of type A is denoted as dA, respectively dAi, dA2, dAs, ... dAn, and the thickness of the nano-layers of type B is denoted as dB, respectively dBi, dB2, dBs, ... dBm. According to the present invention, the quantity of nano-layers of type A is preferably equal to the quantity of nano-layers of type B: n = m or at least n = m.
In another preferred embodiment of the coating structure according to the present invention, the thicknesses of the nano-layers of type A and the thickness of the nanolayers of type B are almost equal: dA = dB, respectively dAn = dBm and A1 = dA2 = dAs = ... dAn and dBi = dB2 = dBs = ... dBm.
Particularly, a very good cutting performance was observed by coatings deposited according to the present invention when the thickness of the B layers was greater than the thickness of the A layers. Therefore, in a further preferred embodiment of the hard nano-layered coating system according to the present invention, the thickness of the nano-layers of type A is smaller than the thickness of the nano-layers of type B: dA < dB or preferably dA « dB, respectively dAn < dBm or preferably dAn « dBm, where dAi = dA2 = dAs = ... dAn and dBi = dB2 = dBs = ... dBm
In one more preferred embodiment of the coating structure according to the present invention, the thickness of the nano-layers of type A is equal or smaller than the thickness of the nano-layers of type B and the thickness of the individual nano-layers A and the thickness of the individual nano-layers B vary along the total coating thickness: dA < dB, respectively dAn < dBm, such that a) dAi > dA2 dAs > ... dAn and dBi > dB2 dBs ^ ... dBm, or b) dAi < dA2 dAs < ... dAn and dBi < dB2 dBs ^ ... dBm, or c) at least one portion of the total coating thickness comprises nano-layers of type A and nano-layers of type B deposited according to a) and at least one portion of the total coating thickness comprises nano-layers of type A and nano-layers of type B deposited according to b).
A hard nano-layered coating system for manufacturing high-performance tools comprises a substrate having a substrate surface and a nanolaminated coating structure according as described above, wherein the nanolaminated coating structure is deposited on the substrate surface.
Concretely, the present invention relates to a coated body comprising a substrate and a coating onto the substrate, the coating having a nanolaminated coating structure consisting of a nano-layered architecture formed of nanolayers, wherein the nanolayered architecture comprises alternately deposited nanolayers of type A and type B (...A/B/A/B/A... ), wherein the A nanolayers have a chemical element composition given by the formula (AlxTii-x-g-yCrgMe1y)N, and the B nanolayers have a chemical element composition given by the formula (Tii-z-uSizMe2u)N, wherein Me1 and Me2 are the dopants in the A and B nanolayers, respectively.
Me1 can be equal to or different from Me2.
The coefficients y and u corresponding to the concentration of Me1 and Me2 can be zero because the use of the dopants Me1 and Me2 in the inventive coating is optional as mentioned above.
According to a preferred embodiment of the coating system, the C-layer is deposited closer to the substrate than the A/B-layer and the A/B-layer is deposited closer to the substrate than the D-layer.
According to a further preferred embodiment, the C-layer can be deposited directly on the substrate surface.
Additionally or alternatively, the D-layer can be deposited as outermost layer of the coating system. According to a further preferred embodiment of the present invention, the D-layer is deposited as outermost layer and comprises apart from titanium, silicon and nitrogen also one or more dopants for further enhancing the effectiveness of the inventive coating. Preferred dopants (one or more) that can be used for the outermost layer can be selected from: Ta, Cr, Si and B.
A coating method for depositing the coating structure on a substrate surface of a substrate comprises the steps: forming an A/B-layer by alternatingly depositing a nano-layer of type A and a nano-layer of type B multiple times on the substrate surface using a PVD technique, wherein the nano-layer of type A contains nitrogen (N), aluminium (Al), titanium (Ti) and chromium (Cr), and the nano-layer of type B contains nitrogen (N), titanium (Ti) and silicon (Si).
According to a preferred embodiment, the above-described coating method further comprises the steps: depositing a C-layer comprising titanium, aluminium, chromium and nitrogen directly on the substrate surface, and depositing a D-layer comprising titanium, silicon and nitrogen directly on the A/B-layer.
The coating method preferably uses arc ion deposition for depositing the coating structure on the substrate surface of the substrate with the following coating parameters: a N2-pressure pN2 within a range: 4 Pa < pN2 7 Pa, a DC substrate bias-voltage VDC within range: -20 V < VDC -60 V (negative bias voltage), and a temperature T within a range: 400°C < T < 550°C.
Further enhancement of the effectiveness of the inventive coating can be attained by using one or more of following process steps: a) Subjecting the substrate or substrate surface to be coated to a specific pretreatment, b) Subjecting the coating system after deposition to a specific post-treatment, c) Adding one or more further layer to the coating system.
The coating system according to the present invention can also be used in further applications different from cutting applications, such as for example in forming applications or in precision components applications, in which other kind of tools or components would be coated with the inventive coating system for attaining the desired performance in the respective application.
More detailed description by using figures 1 to 4 and concrete examples
Figure 1 a and 1 b show schematically the coating architecture of coating systems according to the present invention.
Figure 2 shows the results of a cutting test 1 .
Figure 3 shows the results of a cutting test 2.
Figure 4 shows a fractured cross-section scanning electron micrographs of an inventive coating system.
The nanolaminated coating structure 5 according to the present invention relates to a multilayer coating system which includes nano-layers of type A and nano-layers of type B deposited alternately one on each other and forming an A/B-layer. The nano-layers of type A containing aluminium, Al, titanium, Ti, chromium Cr and nitrogen, N, and the nano-layers of type B containing titanium, Ti, silicon, Si, and nitrogen, N.
Preferentially, at least some nano-layers of type A and/or at least some nano-layers of type B include additionally further elements, for example in the A layers additionally tantalum Ta and or boron B, and/or for example in the layer B additionally chromium Cr. Each nano-layer of type A or B included in the hard nano-layered coating system according to the present invention having fundamentally a maximal individual layer thickness less than 200 nm.
As shown in Fig. 1 (see Fig. 1 a and Fig. 1 b), the architecture of a hard nano-layered coating system according to the present invention can include in addition an interlayer (referenced as 2 in Fig. 1a or as C-layer in Fig. 1 b) between the substrate (referenced as 1 in Fig. 1 a or as substrate in Fig. 1 b) and the nanolaminated coating structure composed of the alternated nano-layers A and nano-layers B (referenced as 5 in Fig. 1 a and as A/B-layer in Fig. 1 b). The thickness and composition of the interlayer is to be selected for example in order to influence the texture of the hard nano-layered coating system and to attain reduced stress in coating. Furthermore, a top layer (referenced as 3 in Fig. 1 a and as D-layer in Fig. 1 b)) can also be deposited on the last layer of the coating structure 5 composed of the alternated nano-layers A and nano-layers B as it is drawn in Fig. 1 a, or it can be only a single top layer having for example the same or similar chemical element composition like the layers B (i.e. same or similar chemical element composition like the nanolayers B).
In one embodiment of the present invention, between the substrate 1 and the A/B-layer 5, it is deposited an interlayer 2 (or C-layer in Fig. 1 b) consisting of AITiCrN having the same Al, Ti and Cr concentration ratio as the A nano-layers which are part of the coating structure.
In another embodiment of the present invention, a top-layer 3 (or D-layer in Fig. 1 b) is the outermost layer and is deposited on the last layer of the nano-layers of the nanolaminated A/B/A/B/A/B... structure of the coating system, and is composed of the same chemical composition as either layer A or layer B.
The (AlxTii-x-g-yCrgMe1y)N/(Tii-z-uSizMe2u)N coatings according to the present invention were deposited on high performance solid carbide drills using PVD techniques. More exactly the coatings were deposited by means of arc ion plating deposition methods at an INNOVENTA coating machine of the company Oerlikon Balzers. Especially suitable coating parameters for the deposition of the coatings according to the present invention were: N2-Pressure pN2: 4 - 7 Pa
• DC Substrate bias-voltage VDC: -20 - -60 V (negative bias voltage)
• Temperature T: 400 - 550°C
• Arc-current was fixed for each experiment taking into account the kind of the arcevaporator used for the evaporation of the target material and the desired thickness of the nano-layers.
Another important aspect of the present invention is the significant influence of the kind of arc-evaporator used for the coating deposition.
Different types of coatings were deposited according to the present invention using different types of arc-evaporators. Arc-evaporators of the type described in the patent documents WO2010088947 and US61/357272 were found to be particularly good suitable for the deposition of the coatings according to the present invention. Using these kinds of arc-evaporators was possible to obtain coatings optimal combination of the mechanical properties, nanolayer period, preferred texture and productivity which are resulting in particularly good coating properties and best cutting performance.
Using the above-mentioned arc-evaporators, it was possible to deposit coatings according to the present invention which exhibit an excellent combination of high rigidity, high oxidation resistance and optimal ratio of Young’s modulus and hardness. This combination of the properties results in an excellent cutting performance particularly for drilling operations.
The coatings according to the present invention exhibit also superior performance by cutting tests than state of the art coatings as it is shown in Fig. 2 and Fig. 3.
Both of the arc evaporators or arc evaporation sources mentioned above were decisive for the deposition of the coatings according to the present invention. In each case the configuration of the arc evaporation source and the operational mode influenced the coating properties. Particularly, it was possible to influence the microstructure of the nanolaminated coating structure turning it fine-grained instead of columnar obtaining in such a manner a non-columnar structure but fine-grained structure. The formation of these fine-grained structures in the nanolaminated coating structure deposited according to the present invention can be clearly observed in Fig. 4. The pictures shown in Fig. 4 correspond to fractured cross-section scanning electron micrographs of two coating systems deposited according to the present invention and comprising a nanolaminated coating structure 5 of alternating A and B layers, where the layers A are AITiCrN layers and the layers B are TiSiN nano-layers, respectively, and having a bilayer period (the sum of the thickness of one A layer and one B layer deposited alternately one on each other at least two times i.e. at least forming a A/B/A/B or B/A/B/A structure) of approximately 50 nm or less.
The produced nanolaminated coating structures exhibiting a fine-grained structure according to the present invention are in particular more advantageous for prevention of crack propagation than similar coatings exhibiting a columnar structure. It can be caused by the difference in the distribution of the grain boundary or crystal boundary in the nanolaminated structure. In a columnar structure, the crystals grow as columns in parallel having consequently a long crystal boundary which extends to the substrate across the coating thickness facilitating the crack propagation along the coating thickness in direction to the substrate and consequently resulting in a faster coating delamination or coating failure. In contrast to a columnar structure, a fine-grained structure like it is produced according to the present invention, comprises fine grains whose crystal boundary or grain boundary doesn’t extend to the substrate across the coating thickness and consequently stopping the crack propagation along the coating thickness in direction to the substrate.
Possibly because of the reason explained above, the fine-grained structures exhibited by the nanolaminated coating structure formed according to the present invention show particularly better cutting performance during drilling and milling operations in relation to life time, fatigue resistance, crater wear resistance, fracture toughness and oxidation resistance than columnar structures.
For the experimental results shown in the present description, some examples of inventive coating systems were used: Example of an inventive coating system:
The inventive coating shown in Fig. 4 comprises a nanolaminated coating structure of alternating AITiCrN and TiSiN nano-layers, the overall nanolaminated coating structure having average composition in atomic percentage of 24.4% Ti, 12.1 % Al, 3.8% Cr, 1.1 % Si and 58.6% N, measured by energy dispersive x-ray spectroscopy. The bilayer period was less than 50 nm. The inventive coating was deposited by arc PVD techniques using powder metallurgical composite TiAICr-targets having a composition in atomic percentage of 40% Al /50% Ti 1 10% Cr for the deposition of the TiAICrN-layers and melt metallurgical composite TiSi-targets having a composition in atomic percentage of 85% Ti /15% Si for the deposition of the TiSiN-layers.
In a preferred embodiment of a coating structure according to the present invention, the nanolaminated structure of alternating nano-layers A and B exhibit an average residual stress, o, between 2 and 4 GPa, preferably between 2.5 and 3.5 GPa. These recommended values of residual stress can be particularly advantageously for drilling and milling operations.
In another preferred embodiment of the present invention, a nanolaminated (AlxTii-x-g- yCrgMe1y)N/(Tii-z-uSizMe2u)N with y = u = 0 is deposited by means of arc PVD techniques using as source material AITiCr-targets made by powder-metallurgical techniques and TiSi-targets made by melt-metallurgical techniques for the deposition of the (AITiCr)N and the (TiSi)N nano-layers, respectively.
In a further preferred embodiment of the present invention, a nanolaminated (AlxTii -x-g- yCrgMe1y)N/(Tii-z-uSizMe2u)N with y = u = 0 is deposited by means of arc PVD techniques using as source material AITiCr-targets made by powder-metallurgical techniques and TiSi-targets also made by powder-metallurgical techniques for the deposition of the (AITiCr)N and the (TiSi)N nano-layers, respectively.
In the case that y 0 and/or u^0, then the targets used as source material would be preferably AITiCrMe1 -targets and TiSiMe2-targets, respectively. Example 1 of coating deposition according to the present invention:
The inventive coating was deposited comprising a nanolaminated coating structure of AITiCrN/TiSiN coating nanolayers having a bilayer period (thickness of two nanolayers AICrN and TiSiN directly next to each other) of about 5-30 nm were deposited on high performance solid carbide drills 0 8.5 mm at a coating machine of the company Oerlikon Balzers of the type INNOVENTA by following coating conditions:
N2-Pressure pish: 6 Pa
Substrate bias-voltage VDC: -40 V (DC)
Temperature T: 570°C
Targets having an element composition of Alo.4Tio.5Cro.i and Tio.85Sio.15 were used respectively for the deposition of the AITiN and TiSiN nano-layer. The material source targets were evaporated using arc evaporators of the type proposed by Krassnitzer et al. in patent document WO2010088947. For Alo^Tio.sCro.i targets the arc evaporators were adjusted as follow the internal (centric) permanent magnet was positioned in front (front) in relation to the target and the outside permanent magnets were positioned at a distance of 4 mm in relation to the target. The arc evaporators were operated setting a coil current of 0.9 A and an arc current of 180 A. For Tio.85Sio.15 targets the arc evaporators were adjusted as follow the internal (centric) permanent magnet was positioned in front (front) in relation to the target and the outside permanent magnets were positioned at a distance of 48 mm in relation to the target. The arc evaporators were operated setting a coil current of 0.9 A and an arc current of 200 A. Coated cutting tools were post-treated after coating using different mechanical methods in order to improve surface quality.
The post-treated solid carbide drills coated according to example 1 were tested by cutting tests 1 and 2 and exhibit an impressively superior cutting performance in all cutting tests (see fig. 2 and 3), almost 50-100% increased cutting distance was achieved. For tests all tools were post-treated with the same method. Fig. 2 shows the results obtained by cutting test 1 , which was carried out with coated solid carbide drills 0 8.5 mm by the following cutting parameters:
Cutting speed vc: 140 m/min
Feed f: 0.21 mm/rev
Through holes, ap: 40 mm
Workpiece material: 1.7225 (42CrMo4) at Rm = 900 MPa
Fig. 3 shows the results obtained by cutting test 2, which was carried out with coated solid carbide drills 0 8.5 mm by the following cutting parameters:
Cutting speed vc: 170 m/min
Feed f: 0.32 mm/rev
Through holes, ap: 40 mm
Workpiece material: 1.1191 (C45)
Example 2 of coating deposition according to the present invention:
AITiCrN/TiSiN coatings having a bilayer period of about 8-15 nm were deposited on high performance solid carbide drills 0 8.5 mm at a coating machine of the company Oerlikon Balzers of the type Innova by following coating conditions:
N2-Pressure plSh: 3.5 Pa
Substrate bias-voltage VDC: -40 V (DC)
Temperature T: 450°C
Targets having an element composition of Alo.4Tio.5Cro.i and Tio.85Sio.15 were used respectively for the deposition of the AITiCrN and TiSiN nano-layer. The material source targets were evaporated using arc evaporators of the same type as those described in example 1 . For the adjustment of the magnet system the internal permanent magnet was also positioned rear in relation to the targets, while the outside permanent magnets were positioned respectively at a distance of 8 mm and 10 mm from the TiAICr- and TiSi-targets. The arc evaporators for the evaporation of the TiAICr- and TiSi-targets were operated respectively setting coil currents of 0.9 A and arc current of 200 A for both target types.
Example 3 of coating deposition according to the present invention:
AITiCrTaN/TiSiBN coatings having a bilayer period of about 5-30 nm were deposited on high performance solid carbide drills 0 8.5 mm at a coating machine of the company Oerlikon Balzers of the type Innova by following coating conditions:
N2-Pressure plSh: 3.5 Pa
Substrate bias-voltage VDC: -40 V (DC)
Temperature T: 450°C
Targets having an element composition of Alo.35Tio.5Cro.1Tao.o5 and Ti0.80Si0.15B0.05 were used respectively for the deposition of the AITiCrTaN and TiSiN nano-layer. The material source targets were evaporated using arc evaporators of the same type used in examples 1 and 2. The arc evaporators were operated by same parameters than those used in example 1 .
The coatings deposited according to the examples 2 and 3 showed also very good cutting performance in similar cutting tests as those described in cutting test 1 and 3.
Using the above-mentioned arc-evaporators, it was possible to deposit coating structures according to the present invention which exhibit coatings hardness values of about 36 - 50 GPa and Young’s modulus values of about 350 - 450 GPa. Both coating hardness and Young’s modulus values were measured using nanoindentation technigues. Furthermore, the coatings deposited according to the present invention exhibit a texture intensity 200/100 > 10 determined by X-ray examinations.
The present invention discloses a coated body, preferably a coated tool comprising a body (1 ), onto which is deposited a hard and wear resistant PVD coating characterized in that the coating comprises a nanolaminated coating structure (5) of alternating A and B layers A1 , A2, A3,... An and B1 , B2, B3,... Bm, respectively, where layer A is (AlxTii-x- yWy)N, with 0.50 < x < 0.65 and 0 < y < 0.10, where the coefficients given by x, 1 -x-y and y correspond to the atomic concentration of aluminium, titanium and tungsten, respectively, considering only the elements aluminium, titanium and tungsten for the element quantification in the layer A, and where layer B is (Tii-z-uSizWu)N, with 0.05 < z < 0.30 and 0 < u < 0.10, where the coefficients given by 1-z-u, z and u correspond to the atomic concentration of titanium, silicon and tungsten, respectively, considering only the elements titanium, silicon and tungsten for the element quantification in said layer B, with a thickness of the nanolaminated coating structure between 0.01 and 30 pm, preferably between 1 and 15 pm, an average individual thickness of the A and B layers is between 1 and 200 nm, respectively, preferably between 1 and 50 nm, more preferably between 1 and 30 nm, characterized in that the nanolaminated coating structure of alternating A and B layers exhibits a fine-grained structure.
More preferably the coated body is a cutting tool comprising a body (1 ) of a hard alloy of cemented carbide, cermet, ceramics, cubic boron nitride based material or high-speed steel.
Preferably, the thickness of the A layers (A1 , A2, A3, ... An), referred to as dA1 , dA2, dA3... dAn, is equal or smaller than the thickness of the B layers (B1 , B2, B3,... Bm), referred to as dB1 , dB2, dB3... dBm, comprised in the nanolaminated coating structure of alternating A and B layers, preferably the thickness of the A layers is equal or smaller than % of the thickness of the B layers: dA1 < % dB1 , dA2 < % dB2, dA3 < % dB3, dAn < % dBm.
Preferably in at least a portion of the total thickness of the nanolaminated coating structure: - the thickness of the A layers and/or the thickness of the B layers remains constant, so that dA1 = dA2 = dA3... = dAn and/or dB1 = dB2 = dB3... = dBm, and/or
- the thickness of A layers and/or the thickness of the B layers increases, so that dA1 > dA2 > dA3... > dAn and/or dB1 > dB2 > dB3... > dBm, and/or
- the thickness of the A layers and/or the thickness of the B layers decreases, so that dA1 < dA2 < dA3... < dAn and/or dB1 < dB2 < dB3... < dBm.
Preferably, in the nanolaminated coating structure comprised in the coating of a coated body as mentioned above:
- the sum of the thicknesses of a nano-layer of type A and a nano-layer of type B deposited alternately one on each other forming a nano-bilayer period is less than 300 nm, preferably less than 100 nm, more preferably between 5 and 50 nm, and
- said nanolaminated coating structure comprises at least a total of four individual nanolayers A and B deposited alternately one on each other forming a A1/B1/A2/B2/ or B1/A1/B2/A2 multilayer architecture, preferably at least a total of ten individual nanolayers forming a A1/B1/A2/B2/A3/B3/A4/B4/A5/B5 or B1/A1/B2/A2/B3/A3/B4/A4/B5/A5 multilayer architecture.
Preferably, in the nanolaminated coating structure comprised in the coating of a coated body as mentioned above:
- the nanolaminated coating structure features a fine-grained structure comprising grains whose largest size is 1/3 of the overall thickness of the nanolaminated coating structure.
Preferably, in the nanolaminated coating structure comprised in the coating of a coated body as mentioned above: - the nanolaminated structure features a fine-grained structure comprising grains having an average size of maximal 1000 nm, preferably between 10 and 800 nm, more preferably between 10 and 400 nm.
According to the present invention, the nanolaminated coating structure comprised in the coating of the coated body mentioned before can be or can comprise an equiaxed structure in which the grains have approximately the same dimensions in all directions.
In a preferred embodiment of a coating structure according to the present invention, the coating structure comprises:
- at least one interlayer 2 (or C-layer in Fig. 1b) deposited between the substrate 1 and said nanolaminated coating structure (orA/B-layer in Fig. 1b), and/or
- at least one top-layer, i.e. outermost layer 3 (or D-layer in Fig. 1 b) deposited on the outermost nano-layer of the nanolaminated coating structure (orA/B-layer in Fig. 1 b).
Preferably, the coated body according to the present invention is a drilling or a milling tool.
Preferably, the coated body according to the present invention is used for drilling or milling operations, more preferably for drilling of steel, stainless steel, or cast iron or milling of hardened steel or stainless steel.
A preferred method for manufacturing a coated body according to the present invention is an arc PVD method characterized by the use of at least one arc vaporization source for the deposition of the nano-layered coating structure on the substrate surface, wherein the at least one arc vaporization source comprises a magnetic field arrangement provided on a target for generating magnetic fields on and above the target surface, wherein the magnetic field arrangement comprises marginal permanent magnets and at least one ring coil placed behind the target, whose inner diameter defined by the windings is smaller than or equal to, and in any case not considerably larger than the diameter of the target, and the marginal permanent magnets can be displaced away from the target essentially perpendicularly to the surface of the target and the projection of the marginal permanent magnets onto the target surface is further away from the middle of the target surface by comparison to the projection of the ring coil onto the target surface, the inner or internal, centric permanent magnet is positioned at the same level in relation to the target as the outer or outside permanent magnet. Both rings are positioned at a distance of several millimeters in relation to the target, preferably between 0 and 10 mm, more preferably ca. 4 mm. Preferably by using this method for the deposition of the nanolaminated coating structure according to the present invention, a negative coil current is applied, the applied coil current is preferably between 0.5 and 1 .4 A.
Preferably, the method applied for the deposition of nanolaminated coating structures according to the present invention comprises the use as source coating material of:
- at least one composite target made by means of powder-metallurgical techniques, comprising aluminium and titanium and/or tungsten are used for the deposition of the nano-layer of type A, and/or
- at least one composite target made by means of melt-metallurgical techniques, comprising titanium and silicon and/or tungsten are used for the deposition of the nanolayer of type B.

Claims

Claims
1. A nanolaminated coating structure, the nanolaminated coating structure consisting of a nano-layered architecture formed of nano-layers, the nano-layered architecture comprising multiple nano-layers of type A and multiple nano-layers of type B alternately deposited and forming an A/B-layer (5), wherein the nano-layers of type A contain nitrogen (N), aluminium (Al), titanium (Ti) and chromium (Cr), and the nano-layers of type B contain nitrogen (N), titanium (Ti) and silicon (Si).
2. The coating structure according to claim 1, wherein the nano-layers of type A contain one or more dopants, preferably boron (B) and tantalum (Ta), and/or the nano-layers of type B contain one or more dopants, preferably chromium (Cr), wherein the dopants are chemical elements selected from the periodic table group 4a, 5a and 6a and boron (Br) that are different from the above-mentioned chemical elements contained in the nano-layers of type A and the nano-layers of type B, respectively.
3. The coating structure according to claim 1 or 2, wherein each nano-layer of the nanolayers of type A or the nano-layers of type B has a maximal individual layer thickness less than 200 nm.
4. The coating structure according to according to claim 1 or 2, wherein a nano-bilayer period of the nano-layers of type A and the nano-layers of type B defined as the sum of the thickness of two nano-layers, respectively one nano-layer of type A and one nano-layer of type B, which are deposited one of each repeatedly at least two times, is less than 300 nm.
5. The coating structure according to any one of the preceding claims, further comprising a C-layer (2) comprising titanium, aluminium, chromium and nitrogen, and a D-layer (3) comprising titanium, silicon and nitrogen, wherein a combined thickness of the C-layer (2) and the D-layer (3) preferably does not exceed 30% of a total coating thickness, and wherein, further preferably, the A/B-layer (5) is directly deposited on the C-layer (2) and the D-layer (3) is directly deposited on the A/B-layer (5).
6. The coating structure according to any one of the preceding claims, wherein one nano-layer of type A has an element composition according to the following formula:
(AIxTii-x-g-yCrgMe^N with x and y in at.% and where 0.20 < x < 0.50, 0.05 < g < 0.30 and 0 < y < 0.20, where Me1 represents a chemical element selected from periodic table group 4a, 5a and 6a and boron (Br), and one nano-layer of type B has an element composition according to the following formula:
(Tii-z-uSizIVIe2u)N with z and u in at.% and where 0.05 < z < 0.30 and 0 < u < 0.20, where Me2 represents chemical element selected from periodic table group 4a, 5a and 6a and boron.
7. The coating structure according to any one of the preceding claims, wherein the A/B- layer comprises at least four or preferably at least ten individual nano-layers, respectively at least two nano-layers of type A and two nano-layers of type B or preferably at least five nano-layers of type A and five nano-layers of type B.
8. The coating structure according to any one of the preceding claims, wherein the quantity of nano-layers of type A is preferably equal to the quantity of nano-layers of type B.
9. The coating structure according to any one of the preceding claims, wherein the thickness of the nano-layers of type A is smaller than the thickness of the nano-layers of type B, wherein the thickness (dA, dAi, dA2, dAs, ...dAn) of the individual nanolayers of type A and the thickness (dB, dBi, dB2, dBs, ... dBm) of the individual nanolayers of type B vary along the total coating thickness such that a) dAi > dA2 > dAs > ... dAn and dBi > dB2 > dBs > ... dBm, or b) dAi < dA2 < dAs < ... dAn and dBi < dB2 < dBs < ... dBm, or c) at least one portion of the total coating thickness comprises nano-layers of type A and nano-layers of type B deposited according to a) and at least one portion of the total coating thickness comprises nano-layers of type A and nano-layers of type B deposited according to b).
10. A coating system for manufacturing high-performance tools, comprising a substrate (1) having a substrate surface, and the nanolaminated coating structure according to any one of claims 1 to 9, wherein the nanolaminated coating structure is deposited on the substrate surface, and wherein the coating system is preferably a high performance coated tool for machining of carbon steel and alloyed steel.
11. The coating system according to claim 10, when dependent on claim 5, wherein the C- layer (2) is deposited closer to the substrate (1) than the A/B-layer (5) and the A/B- layer (5) is deposited closer to the substrate (1) than the D-layer (3).
12. The coating system according to claim 11, wherein the C-layer (2) is deposited directly on the substrate (1), and/or the D-layer (3) is deposited as outermost layer of the coating system and, preferably, further comprises one or more dopants selected from tantalum (Ta), chromium (Cr), silicon (Si) and boron (B).
13. A coating method for depositing the coating structure on a substrate surface of a substrate (1), comprising the steps: forming an A/B-layer by alternatingly depositing a nano-layer of type A and a nanolayer of type B multiple times on the substrate surface using a PVD technique, wherein the nano-layer of type A contains nitrogen (N), aluminium (Al), titanium (Ti) and chromium (Cr), and the nano-layer of type B contains nitrogen (N), titanium (Ti) and silicon (Si).
14. The coating method according to claim 12, further comprising the steps: depositing a C-layer (2) comprising titanium, aluminium, chromium and nitrogen directly on the substrate surface, and depositing a D-layer (3) comprising titanium, silicon and nitrogen directly on the A/B- layer.
15. The coating method according to claim 14, using arc ion deposition for depositing the coating structure on the substrate surface with the following coating parameters: a N2-pressure pN2 within a range: 4 Pa < pN2 < 7 Pa, a DC substrate bias-voltage VDC within range: -20 V < VDC < -60 V, and a temperature T within a range: 400°C < T < 550°C.
PCT/EP2025/056015 2024-03-08 2025-03-05 High performance coated tools for machining of carbon steel and alloyed steel Pending WO2025186329A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010088947A1 (en) 2009-02-09 2010-08-12 Oerlikon Trading Ag, Trübbach Modifiable magnet configuration for arc vaporization sources
WO2013000557A1 (en) 2011-06-30 2013-01-03 Oerlikon Trading Ag, Trübbach Nano-layer coating for high performance tools
US20150259782A1 (en) * 2012-09-08 2015-09-17 Oerlikon Surface Solutions Ag, Trubbach Ti-al-ta-based coating exhibiting enhanced thermal stability
EP4170064A1 (en) * 2021-10-20 2023-04-26 AB Sandvik Coromant Coated cutting tool

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010088947A1 (en) 2009-02-09 2010-08-12 Oerlikon Trading Ag, Trübbach Modifiable magnet configuration for arc vaporization sources
WO2013000557A1 (en) 2011-06-30 2013-01-03 Oerlikon Trading Ag, Trübbach Nano-layer coating for high performance tools
US20150259782A1 (en) * 2012-09-08 2015-09-17 Oerlikon Surface Solutions Ag, Trubbach Ti-al-ta-based coating exhibiting enhanced thermal stability
EP4170064A1 (en) * 2021-10-20 2023-04-26 AB Sandvik Coromant Coated cutting tool

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