Coating tools for machining difficult-to-process materials

Abstract

The present invention relates to a tool (100) for machining a workpiece (200). The tool (100) comprises a surface (110) at least partially covered by a wear-resistant coating (120) deposited by PVD. The wear-resistant coating (120) comprises one or more wear-resistant layers (121, 122). The coating has an elastic modulus E of 300 GPa≦E<350 GPa and a hardness H of more than 30 GPa.

Description

[Technical Field]

[0001] The present invention relates to the tool described in independent claim 1. [Background technology]

[0002] Machining tools used for cutting, drilling, grinding, shearing, or other deformations are subject to wear, especially when machining materials with high hardness or strength, such as nickel alloys (e.g., Inconel® 718), stainless steel, particularly austenitic stainless steel, or steels containing certain amounts of strength-enhancing additives, such as chromium, molybdenum, nickel, manganese, carbon, nitrogen, or oxygen. To increase the durability of machining tools, wear-resistant coatings can be deposited on the surface of the machining tools.

[0003] Each of these coatings possesses a unique combination of mechanical properties, particularly in terms of elastic modulus (also known as Young's modulus or elastic modulus) and hardness. These mechanical properties can enhance the performance and lifespan of the tool. Lifespan is also referred to below as service life or service life. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In general, the coating of the present invention offers significant advantages when machining materials, especially difficult-to-cut materials prone to tool adhesion wear, particularly when using end milling.

[0005] Generally, a wide variety of coatings are used to improve tool performance when machining materials. However, the wear resistance of known tools remains insufficient.

[0006] Therefore, the object of the present invention is to provide a tool that eliminates at least partially the aforementioned drawbacks, has a longer lifespan, and can improve the machining of workpieces. [Means for solving the problem]

[0007] The inventors of this invention have discovered that by coating tools with a coating exhibiting a hardness value H greater than 30 GPa (i.e., H > 30 GPa) and an elastic modulus value E between 300 GPa and 350 GPa (i.e., 300 ≤ E < 350 GPa), they have achieved remarkably high levels of wear reduction and improvement in the overall performance of the tools.

[0008] The above problem is solved by the apparatus having the features of claim 1. According to the present invention, a tool for machining a workpiece is proposed. This tool includes a surface that is at least partially covered with an abrasion-resistant coating, the abrasion-resistant coating having an elastic modulus of 300 to 350 GPa and a hardness H greater than 30 GPa (i.e., H > 30 GPa).

[0009] Furthermore, the specific values ​​for the elastic modulus and hardness of the wear-resistant coating refer specifically to values ​​measured under standard conditions, i.e., indoor ambient temperature, indoor ambient pressure, etc. (in other words, normal environmental conditions).

[0010] As demonstrated in the representative examples, the combination of these two mechanical properties can, surprisingly, extend tool life and improve machinability. When the hardness exceeds 30 GPa, coatings with an elastic modulus of 300-350 GPa exhibit significantly better performance than those below or above this range.

[0011] Machining may include, at a minimum, turning, drilling, countersinking, reaming, milling, planning, shaping, broaching, sawing, filing, rasping, brushing, scraping, or chiselling. The tools of the present invention are particularly suitable for materials that are difficult to process, especially those that are difficult to cut.

[0012] The modulus of elasticity, or Young's modulus, tensile modulus, modulus of elasticity, or elongation coefficient, are parameters of a material. In the case of linear elastic behavior, the modulus of elasticity indicates the proportional relationship between stress and strain during deformation of a solid. Therefore, the modulus of elasticity is the proportionality constant in Hooke's Law.

[0013] Hardness is the mechanical resistance of a material when mechanically penetrating another solid object, and can be determined in various ways. Hardness values ​​can be based on Vickers hardness tests, but the scope of this invention is not limited to this. Experts can draw conclusions from Vickers hardness to other hardness measures, such as Rockwell hardness.

[0014] The surface of this invention is formed from the same material that forms the tool. Therefore, in its simplest form, this surface is an uncoated surface. This does not preclude the formation of an oxide layer, which is always present when the surface comes into contact with ambient air. Other parts of the tool are typically made from at least one bulk material.

[0015] The area covered with the wear-resistant coating may be placed where the tool mechanically contacts the workpiece. This offers the advantage that the tool does not need to be completely coated. In most deposition processes, the substrate (in this case, the tool) must be fixed to a holder, so coating the entire surface of the tool would be significantly more expensive. The position where the holder clamps the tool cannot be coated. Therefore, the holder would have to be moved to another position in order to coat the entire tool with the coating. Thus, by coating only the area where the tool contacts the workpiece, manufacturing costs can be reduced while maintaining functionality.

[0016] In this invention, coating with an abrasion-resistant layer means that this layer adheres firmly to the tool and will not be easily removed, especially if the tool is not used in the intended manner.

[0017] Furthermore, the wear-resistant coating of the present invention may include one or more wear-resistant layers, each of which has an elastic modulus of 300 to 350 GPa and a hardness exceeding 30 GPa.

[0018] This offers the advantage of ultimately resulting in a longer lifespan by combining the properties of different materials, such as chemical resistance. Furthermore, it can prevent Mode I cracking (opening mode), particularly at the interface between two layers.

[0019] Advantageously, an adhesive layer is applied between the surface and the abrasion-resistant coating, and the adhesive layer improves the adhesion of the abrasion-resistant coating to the surface, having a thickness between 10 nm and 1 μm, and in particular, the thickness of the adhesive layer is smaller than the thickness of the abrasion-resistant coating, preferably at least three times smaller.

[0020] This can be particularly important when the material and / or mechanical properties of the tool differ significantly from those of the wear-resistant coating. x Ti x-1In the case of the N film, the adhesive layer made of TiN or AlN can significantly improve the adhesion of the wear-resistant film. Further, the improvement in adhesion results in an increase in tool life.

[0021] An adhesive layer having a thickness between 10 nm and 1 μm or at least three times smaller than the wear-resistant film has the advantage of increasing the adhesion of the wear-resistant film without degrading the functionality (wear resistance) of the wear-resistant film. When the layer thickness is too thin, the adhesion may be reduced, and when the layer thickness is too thick, the functionality of the wear-resistant film may be impaired. This realizes the advantage of improving the machining performance.

[0022] Furthermore, the adhesive layer may have a thickness of 10 nm to 0.5 μm, particularly 10 nm to 0.25 μm. This can reduce the manufacturing cost by maintaining functionality and further shortening the time required for depositing the adhesive layer.

[0023] Also, the wear-resistant film may include two or more wear-resistant layers, and at least two of the two or more wear-resistant layers may be formed from materials containing the same elements with different chemical compositions. This has the advantage of enabling more flexible deposition processing. For example, in order to better improve the adhesion of the film to the tool, the layer directly deposited on the tool needs to have a slightly higher amount of one material than the layer in contact with the workpiece. This can customize the improvement of the wear-resistant film on the surface of the tool, enabling a longer life and better machining performance. In the context of the present invention, different chemical compositions can specifically mean both a composition in which the relevant elements are present in different amounts and a composition in which the relevant elements are different only in configuration.

[0024] Furthermore, advantageously, the wear-resistant coating may include two or more wear-resistant layers, at least two of which may be formed from materials with the same chemical composition and the same elements, but with different mechanical properties such as elastic modulus and / or hardness. This offers the advantage of allowing for more flexible adjustment of the wear-resistant layers depending on the specific application. For example, a harder wear-resistant coating may be required to machine a particular workpiece more quickly, while a lower hardness may be required to improve lifespan. Therefore, a wear-resistant coating with a lower hardness layer in contact with the tool surface can be combined with a wear-resistant coating with a higher hardness layer in mechanical contact with the workpiece. Thus, by combining different mechanical properties, a longer lifespan and better machinability can be achieved. The different mechanical properties may preferably be adjusted by specifically changing coating parameters such as temperature, pressure, deposition time, bias voltage, and discharge current.

[0025] The wear-resistant coating may include two or more wear-resistant layers, and at least two of these layers may be formed from different materials. By depositing two or more wear-resistant layers, for example, the properties of the layer facing the workpiece can be adjusted according to the properties of the workpiece, and the properties of the layer facing the tool surface can be adjusted according to the properties of the tool, thereby extending the lifespan and improving machining performance.

[0026] The wear-resistant coating comprises at least one TiAlN layer (in the context of the present invention, the TiAlN layer preferably has an atomic percentage chemical composition of Ti 1-q Al qIt may include a titanium aluminum nitride layer having N(0.5 < q ≤ 0.9), or at least one layer of TiSiN, or at least one layer of AlCrN. Titanium aluminum nitride (TiAlN) and aluminum titanium nitride (AlTiN) represent a group of metastable hard coatings composed of the metal elements aluminum and titanium and nitrogen. The mechanical properties of the TiAlN layer and the AlTiN layer are particularly suitable for the machining of abrasives. Thereby, the extension of the service life and the improvement of machining can be realized. Titanium silicon nitride (TiSiN) has the advantages of high edge retention and high corrosion resistance of the cutting tool, and finally represents a group of hard coatings that improve the service life and machining. The aluminum chromium nitride (AlCrN) layer has excellent resistance to thermal shock and high thermal durability. This brings the advantages of extending the service life and improving machining.

[0027] According to a preferred embodiment, the wear-resistant coating is a two-layer coating including an AlTiN layer and a TiSiN layer, or a two-layer coating including an AlTiN layer and an AlCrN layer.

[0028] Advantageously, the wear-resistant coating includes at least one layer of nitride, or at least one layer of carbonitride, or at least one layer of carboxynitride, or at least one layer of oxynitride. In some cases, for example, when end-milling a material difficult to cut, the wear-resistant coating may preferably include only or mainly a nitride layer. Since the nitride layer has the advantage of hardening most surfaces, higher wear resistance can be achieved. The carboxynitride layer has a low friction coefficient and high hardness. Also, the carboxynitride layer has a low friction coefficient and low internal stress in the coating. The oxynitride layer has good chemical resistance. All these alternatives or combinations thereof provide the advantages of extending the service life and / or improving machining.

[0029] Furthermore, advantageously, the chemical composition of at least one wear-resistant layer included in the wear-resistant coating contains at least two metals, particularly aluminum and titanium. A coating containing at least two metals has good mechanical properties compared to a metal-free coating or a coating containing only one metal. Aluminum and titanium have shown particularly good performance with respect to lifespan and machinability.

[0030] Furthermore, the chemical composition of at least one wear-resistant layer included in the wear-resistant coating may be Al x Ti 1-x N. In the formula, x has a value between 0.5 and 0.9 (i.e., 0.5 < x ≤ 0.9), preferably a value between 0.6 and 0.8 (i.e., 0.6 ≤ x ≤ 0.8). The AlTiN coating having the characteristics of the present invention has a long lifespan and good machinability. Al x Ti 1-x N (in the range of 0.5 < x ≤ 0.9, particularly 0.6 ≤ x ≤ 0.8) coatings show particularly good characteristics, and a coating with x = 0.66 is particularly preferred.

[0031] The chemical composition of at least one wear-resistant layer included in the wear-resistant coating may contain at least titanium and silicon, and particularly may additionally contain nitrogen. A wear-resistant coating containing titanium and silicon has excellent adhesion to the surface of the tool and / or the adhesive layer. Furthermore, when nitrogen is additionally incorporated into the wear-resistant layer, the chemical resistance of the coating is improved. In any case, the lifespan is prolonged.

[0032] The wear-resistant coating may have a layer thickness of 0.5 to 20 μm, particularly 1 to 7 μm or 5 to 20 μm. The thickness of the wear-resistant coating has a great influence on the lifespan. If the coating is too thin, wear will be relatively fast. If the coating becomes very thick, it can be easily peeled off. The wear-resistant coating having the characteristics of the present invention shows particularly excellent lifespan when the layer thickness is 0.5 to 20 μm, and the lifespan is further improved when the layer thickness is in the range of 1 to 7 μm or 5 to 20 μm. A representative example of this behavior is described in the description of the drawings.

[0033] Furthermore, advantageously, wear-resistant coatings have a crystalline or polycrystalline structure. Wear-resistant coatings with a crystalline or polycrystalline structure are particularly resistant to abrasive wear, thus extending their lifespan.

[0034] The wear-resistant coating may have a variable texture. Texture refers to the distribution of crystal orientations in a polycrystalline sample. A variable texture means that at least two dominant orientations exist. When a variable texture is present in the wear-resistant coating, the lifespan of the wear-resistant coating is extended. If at least two layers are present in the wear-resistant coating, each layer may have a specific texture different from the texture of the other coatings. This allows for more flexible deposition processes and extends the lifespan of the tools.

[0035] The wear-resistant coating may include at least one wear-resistant layer exhibiting a cubic phase. The wear-resistant coating including a layer exhibiting a cubic phase offers the advantages of improved hardness and enhanced thermal stability.

[0036] Furthermore, advantageously, the abrasion-resistant coating and / or at least one abrasion-resistant layer and / or adhesive layer are deposited using physical vapor deposition, particularly arc evaporation. Coatings and layers deposited using physical vapor deposition (PVD) have the advantage of being harder and having higher corrosion resistance than coatings applied by other processes such as electroplating. In addition, compared to CVD processes, PVD processes have the advantage that the deposited layer does not inherently have residual tensile stress or chlorine residue. Moreover, the application temperature is significantly higher in CVD processes, which usually require undesirable post-treatment. By using arc evaporation, particularly filtered arc deposition, in the PVD process, the lifespan of the coating can be further improved.

[0037] Furthermore, the present invention includes the use of tools for machining the above-mentioned difficult-to-machine materials, and in particular for end milling difficult-to-machine materials. In the context of the present invention, difficult-to-machine materials can be understood to be specifically materials having a yield strength of more than 180 MPa at a temperature of 100°C, preferably more than 500 MPa, in particular more than 1000 MPa and / or a tensile strength of more than 400 MPa at a temperature of 100°C, preferably more than 800 MPa, in particular more than 1200 MPa.

[0038] Furthermore, the tool can be used to machine materials that are difficult to cut. These materials are at least partially stainless steel or nickel alloys (i.e., Inconel® 718). The materials may also be austenitic stainless steel or steel containing certain amounts of strength-enhancing additives, such as chromium, molybdenum, nickel, manganese, carbon, nitrogen, or oxygen.

[0039] Further features and details of the present invention are derived from the dependent claims, specification and drawings. Features and details described in relation to the apparatus of the present invention apply to the systems and / or methods of the present invention, and vice versa. Individual aspects of the disclosed present invention may be referenced to one another.

[0040] Further measures to improve the present invention are schematically shown in the drawings and can be derived from the following description of some examples for realizing the invention. All features and / or advantages derived from the claims, description, or drawings, including design details, spatial arrangements, and processing steps, are essential to the invention, both individually and in various combinations. The drawings are for illustrative purposes only and are not intended to limit the invention in any way. [Brief explanation of the drawing]

[0041] [Figure 1] This is a schematic diagram illustrating the tool of the present invention. [Figure 2]This is a schematic diagram showing the tool of the present invention, including an adhesive layer. [Figure 3] This is a schematic diagram showing the tool of the present invention, which includes two wear-resistant layers. [Figure 4] This diagram shows a typical set of coatings (in the diagram, the elastic modulus is shown as a function of hardness). [Figure 5] This figure shows typical coatings of various thicknesses having the mechanical properties of the prior art and the present invention (in the figure, tool life is shown as a function of coating thickness). [Figure 6] 1.3571 This figure shows a typical coating with an elastic modulus as a function of wear for machining a workpiece formed from SUS316Ti. [Figure 7] This figure shows a typical coating with an elastic modulus as a function of wear for machining workpieces formed from Inconel 718. [Modes for carrying out the invention]

[0042] Figures 1 to 3 are schematic diagrams illustrating examples of the tools of the present invention. Figures 4 to 7 below show the characteristics of representative tools and coatings measured to illustrate the advantages of a typical set of tools of the present invention. The advantages shown in the presented examples can be realized for other coatings having various chemical compositions, lamination methods, and thicknesses, as long as the characteristics of the present invention are maintained.

[0043] Figure 1 shows an example of a tool 100 of the present invention for machining a workpiece 200. The surface 110 of the tool is at least partially coated with an abrasion-resistant coating 120. The abrasion-resistant coating 120 has an elastic modulus E of 300 to 350 GPa and a hardness H greater than 30 GPa. The tool 100 is formed from at least one bulk material 101 which may have different mechanical properties from the abrasion-resistant coating 120.

[0044] Figure 2 shows another example of the tool 100 of the present invention. An adhesive layer 130 is applied between the surface 110 and the wear-resistant coating 120. The adhesive layer 130 improves the adhesion of the wear-resistant coating 120 to the surface 110 and can have a thickness of 10 nm to 1 μm, preferably 10 nm to 0.5 μm, and particularly 10 nm to 0.25 μm. Alternatively or additionally, the thickness of the adhesive layer is less than the thickness of the wear-resistant coating 120, preferably at least three times less. A thinner layer may reduce adhesion, while a thicker layer may impair the functionality of the wear-resistant coating. This allows for the benefit of improved processing performance.

[0045] Figure 3 shows a further example of the tool 100 of the present invention. In this example, the abrasion-resistant coating 120 shown includes two abrasion-resistant layers 121 and 122 in addition to the adhesive layer 130. Each of the abrasion-resistant layers 121 and 122 has an elastic modulus E of 300 to 350 GPa and a hardness H of more than 30 GPa. This allows for the combination of properties of different materials, such as chemical resistance, and ultimately extends the lifespan.

[0046] The following drawings (4-7) show the characteristics of a typical set of the tool 100 and coatings measured to demonstrate the advantages of the tool 100 of the present invention.

[0047] As shown in Figure 4, excellent results were obtained for all coatings having the elastic modulus and hardness within the scope of the present invention described above, particularly during machining of materials, especially during end milling of materials that are difficult to cut. These results were far better than when using coatings that do not have the elastic modulus and hardness within the scope of the present invention.

[0048] Figure 4 shows the combination of range values of the elastic modulus and hardness of an AlTiN coating deposited using the cathode arc deposition technique. To deposit each coating, four AlTi targets are used as the metal material source. The four targets are used in a known method. Each target is used as the cathode of the corresponding arc evaporator, and nitrogen gas is used as the reactive gas. A similar trend was also observed for other coating materials, particularly combinations of layers including AlCrN, TiSiN, and at least two metals and / or at least one nitride layer or at least one carbonitride layer or at least one carboxynitride layer or at least one oxynitride layer.

[0049] According to the present invention, a tool 100 can be provided. The wear-resistant coating 120 of the tool includes at least one layer of TiAlN, or at least one layer of TiSiN, or at least one layer of AlCrN. Alternatively or additionally, the wear-resistant coating 120 may include at least one layer of nitride, or at least one layer of carbonitride, or at least one layer of carboxynitride, or at least one layer of oxynitride. Further, alternatively or additionally, the chemical composition of at least one wear-resistant layer 121, 122 included in the wear-resistant coating 120 may include at least two metals, particularly aluminum and titanium.

[0050] In the tool 100 of the present invention, the chemical composition of at least one layer 121, 122 included in the wear-resistant coating 120 is Al x Ti 1-x N, where x has a value between 0.5 and 0.9, preferably between 0.6 and 0.8, and particularly preferably the value of 0.66. Alternatively or additionally, the chemical composition of at least one wear-resistant layer 121, 122 included in the wear-resistant coating 120 includes at least titanium and silicon, and particularly can additionally include nitrogen.

[0051] To obtain different values of the elastic modulus and hardness of the coatings shown in Figure 4, the coating parameters (e.g., substrate temperature, bias voltage) were changed.

[0052] All values ​​for the elastic modulus and hardness of the wear-resistant coatings used in the description of this invention were measured using a Fischerscope H100C. The applied load force was 10 mNw. Measurements were performed such that the maximum indentation depth was 1% of the total thickness of the wear-resistant coating 120. To perform the measurements, the surface of the steel sample was polished and then coated with the coating to be tested. To ensure accurate measurement of mechanical properties and further coating properties, the coating thickness was at least 2 μm.

[0053] To demonstrate the significant improvements achieved by the present invention, the inventors deposited different aluminum titanium nitride (AlTiN) coatings, particularly by using PVD (Physical Vapor Deposition) techniques belonging to arc deposition.

[0054] Deposited AlTiN has a hardness value exceeding 30 GPa, but does not have an elastic modulus value between 300 GPa and 350 GPa.

[0055] In order to better explain the present invention and the technical improvements achieved thereby, some embodiments and comparative examples of the present invention will be described in more detail below. These embodiments should be understood not as limiting the present invention, but as illustrative examples.

[0056] Example 1 - Conventional Example A conventional single-layer AlTiN coating was deposited as a wear-resistant coating on an end milling tool by reactive cathode arc evaporation of an AlTi target. To generate Al and Ti vapors, the target was used as the cathode of the corresponding arc evaporator in the presence of nitrogen gas. Nitrogen gas was introduced into the coating chamber as a reactive gas to react with Al and Ti to form the AlTiN coating. The fabricated AlTiN coating was composed of Al x Ti 1-xIt has an atomic percentage chemical composition corresponding to N(x=0.66), an elastic modulus value corresponding to 400 GPa, and a hardness value corresponding to 40 GPa. Similar trends were observed in other coating materials, particularly AlCrN, TiSiN, and combinations of layers containing at least two metals and / or at least one nitride layer, at least one carbonitride layer, at least one carboxynitride layer, or at least one oxynitride layer.

[0057] An end milling tool was coated with the film from Example 1. The film thickness of the AlTiN coating was varied to produce tools containing AlTiN coatings of 1 μm, 2 μm, and 3 μm, respectively. Similar trends were observed with other coating materials.

[0058] Example 2 - Invention Example The single-layer AlTiN coating of the present invention was deposited as an abrasion-resistant coating 120 on an end milling tool 100 by reactive cathode arc evaporation of an AlTi target. To generate Al and Ti vapors, the target was used as the cathode of the corresponding arc evaporator in the presence of nitrogen gas. Nitrogen gas was introduced into the coating chamber as a reactive gas to react with Al and Ti to form the AlTiN coating. The fabricated AlTiN coating 120 is composed of Al x Ti 1-x It has an atomic percentage chemical composition corresponding to N(x=0.66), an elastic modulus value corresponding to 304 GPa, and a hardness value corresponding to 35 GPa. Similar tendencies and the advantages of the present invention can also be obtained by using other deposition processes such as physical vapor deposition.

[0059] Both Examples 1 and 2 described above were deposited to have a single-layer structure (i.e., a structure consisting of only one layer). However, as stated above, the present invention is not limited to a wear-resistant coating 120 having a single-layer structure, but also includes a wear-resistant coating 120 having a multilayer structure (i.e., a structure consisting of two or more layers deposited on each other).

[0060] According to the present invention, a tool 100 for machining materials, especially materials that are difficult to cut, and especially for end milling, and particularly an abrasion-resistant coating provided on an end mill, exhibits the above-described range values ​​of the present invention, namely, an elastic modulus of 300 GPa ≤ E < 350 GPa and a hardness of H > 30 GPa. When the abrasion-resistant coating 120 of the present invention includes one or more abrasion-resistant layers 121, 122, each of the abrasion-resistant layers 121, 122 can have an elastic modulus of 300 to 350 GPa and a hardness greater than 30 GPa.

[0061] The adhesive layer 130 may be deposited between the surface of the tool 110 and the wear-resistant coating 120. Such an adhesive layer 130 can improve the adhesion between the surface of the tool 110 being coated and the wear-resistant coating 120. The adhesive layer 130 may be provided to have different range values ​​for elastic modulus and hardness from the layer (or multiple layers) forming the wear-resistant coating 120.

[0062] When an adhesive layer 130 is provided, the thickness of the adhesive layer preferably does not exceed 1 μm. Also, when using the adhesive layer 130, the thickness of the adhesive layer 130 preferably does not exceed the thickness of the abrasion-resistant coating 120.

[0063] The tool life of an end milling tool coated with a conventional coating in Example 1 and the tool life of an end milling tool coated with the coating of the present invention in Example 2 are shown in Figure 5.

[0064] To produce the results shown in Figure 5, cutting tests were performed on end milling tools 100 coated with abrasion-resistant coatings 120 of Example 1 and Example 2, which have different coating thicknesses, using the following cutting test parameters. - Workpiece material: 1.4571 SUS316Ti - Tool type: End mill with diameter d=10mm - Cutting parameters: Vc = 110 m / min, f t =0.04mm, ap=8mm, ae=4mm, wet state Figure 5 (right side) shows that the AlTiN coating manufactured according to Example 2 was used as a wear-resistant coating for end milling tools, extending tool life when machining 1.4571 SUS316Ti, a material that is difficult to cut. It can also be observed that the longer the tool life achieved, the thicker the wear-resistant coating.

[0065] In contrast, Figure 5 (left) shows that conventional AlTiN coatings do not increase tool life. With these conventional wear-resistant coatings, the effect of coating thickness is completely reversed; that is, the thicker the wear-resistant coating, the shorter the tool life.

[0066] From the results shown in Figure 5, it can be concluded that in machining operations where adhesive wear is dominant, particularly cutting operations (e.g., machining of stainless steel, especially end milling, or machining of Inconel®), increasing the thickness of the wear-resistant coating can significantly increase tool performance and therefore tool life. However, a thicker wear-resistant coating may be beneficial only when the wear-resistant coating is provided according to the present invention, in other words, only when the wear-resistant coating 120 has elastic modulus and hardness values ​​within the range of the present invention described above.

[0067] Surprisingly, the inventors of the present invention have found that further advantages can be achieved by changing the coating properties of the wear-resistant layer 120, such as the chemical composition, (poly)crystalline structure, and (variable) texture, but the effects described above are obtained by maintaining the combination of elastic modulus and hardness within the ranges described above, i.e., 300 GPa ≤ E < 350 GPa and H > 30 GPa, as described in claim 1 of this patent application. Therefore, a similar trend may be observed in other coating materials, particularly AlCrN, TiSiN, and combinations of layers including at least two metals and / or at least one nitride layer, or at least one carbonitride layer, or at least one carboxynitride layer, or at least one oxynitride layer.

[0068] According to a preferred embodiment of the present invention, the wear-resistant coating 120 may have a crystalline or polycrystalline structure. Alternatively or additionally, the wear-resistant coating 120 may have a variable texture and / or exhibit a cubic phase.

[0069] According to a preferred embodiment of the present invention, the wear-resistant coating 120 comprises at least one layer made of or mainly containing AlTiN.

[0070] According to a preferred embodiment of the present invention, the wear-resistant coating 120 comprises at least two wear-resistant layers 121, 122, where one of the two layers is made of or mainly contains AlTiN, and the other layer is made of or mainly contains TiSiN. Alternatively, the wear-resistant coating 120 may comprise two or more wear-resistant layers 121, 122, where at least two of the two or more wear-resistant layers 121, 122 are formed from materials with the same chemical composition and the same elements, but with different mechanical properties such as elastic modulus and / or hardness. Alternatively or additionally, the wear-resistant coating 120 may comprise two or more layers 121, 122, where at least two of the two or more wear-resistant layers 121, 122 are formed from different materials. According to a further preferred embodiment of the present invention, the wear-resistant coating 120 comprises two or more layers 121, 122, wherein the two or more layers 121, 122 differ in at least one of the material properties that fall under the group consisting of chemical composition, crystalline structure, and texture.

[0071] According to a further preferred embodiment of the present invention, the thickness of the wear-resistant coating is 0.5 μm to 20 μm, for example, 1 μm to 7 μm, preferably 5 to 20 μm, as shown in Figure 3.

[0072] The desired coating properties relating to the combination of elastic modulus and hardness of the present invention can be achieved by selecting an appropriate combination of coating parameters depending on the type of coating process employed.

[0073] For example, when depositing an AlTiN film, the inventors of the present invention discovered that the selection of an appropriate combination of bias voltage and substrate temperature greatly affects the combination of elastic modulus and hardness achieved. Furthermore, the appropriate combination of film parameters for depositing the AlTiN film of the present invention also depends on the Al content.

[0074] Figure 6 shows the wear behavior of tool 100 coated according to a representative example of the present invention. As shown in Figure 6, tool 100 exhibits a hardness and elastic modulus (vertical axis - left index scale) combination exceeding 30 GPa. The coated tool was tested by machining stainless steel. The amount of wear was measured from wear photographs after a cutting distance of 24 m.

[0075] The following cutting parameters were used to produce the results shown in Figure 6. - Workpiece material: 1.4571 SUS316Ti - Tool type: End mill with diameter d=10mm - Cutting parameters: Vc=110m / min, ft=0.04mm, ap=8mm, ae=4mm, wet condition The results obtained are representative examples only. Similar trends were observed with other coating materials, particularly AlCrN, TiSiN, and combinations of layers containing at least two metals and / or at least one nitride layer, at least one carbonitride layer, at least one carboxynitride layer, or at least one oxynitride layer. Other deposition processes, workpiece materials, and lamination methods can also be used.

[0076] Figure 7 shows the wear behavior of a representative example of a tool coated according to the present invention. As shown in Figure 7, this tool exhibits a hardness and elastic modulus (vertical axis - left index scale) combination exceeding 30 GPa. The coated tool was tested by machining Inconel. Wear was measured after a cutting distance of 6.8 m.

[0077] The following cutting parameters were used to produce the results shown in Figure 7. - Workpiece material: Inconel 718 - Tool type: End mill with diameter d=10mm - Cutting parameters: Vc=50m / min, ft=0.06mm, ap=5mm, ae=0.5mm, wet condition The results obtained are representative examples only. Similar trends were observed with other coating materials, particularly AlCrN, TiSiN, and combinations of layers containing at least two metals and / or at least one nitride layer, at least one carbonitride layer, at least one carboxynitride layer, or at least one oxynitride layer. Other deposition processes, workpiece materials, and lamination methods can also be used.

[0078] The above description of embodiments is illustrative and describes the present invention exclusively. Needless to say, individual features of the design configuration can be freely combined as long as they do not depart from the scope of the present invention and are technically reasonable.

Claims

1. A tool (100) for machining a workpiece (200), The surface (110) is at least partially covered by a wear-resistant coating (120) deposited by PVD, The abrasion-resistant coating (120) includes one or more abrasion-resistant layers (121, 122), The coating has an elastic modulus E of 300 GPa ≤ E < 350 GPa, and a hardness H greater than 30 GPa. At least one of the wear-resistant layers has an atomic percentage chemical composition Al ｘ Ti １－ｘ A tool (100) characterized by having an aluminum titanium nitride layer having N (0.6 < x ≤ 0.8), i.e., an AlTiN layer.

2. The abrasion-resistant coating (120) includes two or more abrasion-resistant layers (121, 122), The tool (100) according to claim 1, characterized in that each of the wear-resistant layers (121, 122) has an elastic modulus E of 300 GPa ≤ E < 350 GPa and a hardness H greater than 30 GPa.

3. An adhesive layer (130) is applied between the surface (110) and the wear-resistant coating (120). The tool (100) according to claim 1 or 2, characterized in that the adhesive layer (130) improves the adhesion of the abrasion-resistant coating (120) to the surface (110) and has a thickness of 10 nm to 1 μm.

4. The tool (100) according to claim 3, characterized in that the adhesive layer (130) is deposited by physical vapor deposition.

5. The abrasion-resistant coating (120) includes two or more abrasion-resistant layers (121, 122), The tool (100) according to any one of claims 1 to 4, characterized in that at least two of the two or more wear-resistant layers (121, 122) are formed from materials containing the same elements but with different chemical compositions.

6. The abrasion-resistant coating (120) includes two or more abrasion-resistant layers (121, 122), The tool (100) according to any one of claims 1 to 5, characterized in that at least two of the two or more wear-resistant layers (121, 122) are formed from materials that have the same chemical composition and contain the same elements, but have different mechanical properties in terms of elastic modulus and / or hardness.

7. The abrasion-resistant coating (120) includes two or more layers (121, 122), The tool (100) according to any one of claims 1 to 5, characterized in that at least two of the two or more wear-resistant layers (121, 122) are formed from different materials.

8. The abrasion-resistant coating (120) is At least one TiAlN layer, and / or At least one TiSiN layer, and / or A tool (100) according to any one of claims 1 to 7, characterized by comprising at least one AlCrN layer.

9. The tool (100) according to any one of claims 1 to 8, characterized in that the wear-resistant coating (120) includes at least one nitride layer.

10. The tool (100) according to any one of claims 1 to 9, characterized in that the wear-resistant coating (120) comprises at least one carbonitride layer, or at least one carboxynitride layer, or at least one oxynitride layer.

11. The tool (100) according to any one of claims 1 to 10, characterized in that the wear-resistant coating (120) has a layer thickness of 0.5 to 20 μm.

12. The tool (100) according to any one of claims 1 to 11, characterized in that the wear-resistant coating (120) has a crystalline or polycrystalline structure.

13. The tool (100) according to claim 12, characterized in that the wear-resistant coating (120) has a variable texture, and the variable texture means that at least two dominant crystal orientations exist.

14. The tool (100) according to any one of claims 1 to 13, characterized in that the wear-resistant coating (120) includes at least one wear-resistant layer exhibiting a cubic phase.

15. The tool (100) according to any one of claims 1 to 14, characterized in that the abrasion-resistant coating (120) and / or the at least one abrasion-resistant layer (121, 122) is deposited by physical vapor deposition.

16. The tool (100) according to any one of claims 1 to 15, characterized in that the wear-resistant coating (120) is a two-layer coating comprising an AlTiN layer and a TiSiN layer, or a two-layer coating comprising an AlTiN layer and an AlCrN layer.

17. Use of the tool (100) according to any one of claims 1 to 16 for machining materials that are difficult to cut.

18. The use according to claim 17, characterized in that the material that is difficult to cut is at least partially stainless steel or a nickel-based alloy.

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