HIGH-PERFORMANCE TOOL COATING FOR PRESSURE HARDENING OF COATED AND UNCOATED ULTRA-HIGH-STRENGTH STEEL ROLLED METALS

Abstract

Coated tool for hot stamping coated or uncoated rolled metals, in particular for hot stamping rolled metals coated with AlSi or Zn, comprising a coated substrate surface that will be in contact with the coated or uncoated rolled metal, wherein the coating on the coated substrate surface is a multilayer coating comprising one or more lower layers and one or more upper layers, wherein the lower layers are deposited closer to the substrate surface than the upper layers, and: - the lower layers are designed to provide load-bearing capacity, - the upper layers are designed to provide resistance to continuous friction wear, - at least one upper layer (layer 5) is deposited having a multinanolayer structure formed by sublayers of type A, B, and C.These three classes of sublayers are deposited alternately on top of each other forming a sequence of the type ...A / B / C / A / B / C / A..., wherein at least two sequences of a nanolayer A, a nanolayer B and a nanolayer C are deposited forming the multinanolayer structure - wherein: - the type A nanolayer is composed of at least 90 atomic percent chromium and nitrogen, - - the type B nanolayer is composed of at least 90 atomic percent titanium, aluminum and nitrogen, - - the type C nanolayer is composed of at least 90 atomic percent vanadium, carbon and nitrogen, and - - the thickness of the layer of the at least one upper layer (layer 5) is not less than 0.5 µm and not greater than 15 µm.

Description

HIGH-PERFORMANCE TOOL COATING FOR PRESSURE HARDENING OF ROLLED STEEL METALS ULTRA HIGH STRENGTH COATED AND UNCOATED Technical field The present invention relates to a coating to be applied to tool surfaces, especially forming tools (also referred to as dies in this text), used for pressure hardening, also known as hot stamping, of coated and uncoated rolled metals with AISi or Zn, e.g., ultra-high-strength steel (UHSS), the most common type of which is 22MnB5 USIBOR. This document uses the WorldAutoSteel format to define different types of steel, such as UHSS, AHSS, or LSS. This document uses the metallurgy type, minimum yield strength (MPa), and minimum tensile strength (MPa) to identify the different types of steel. Generally, steels with yield strengths above 550 MPa and tensile strengths above 780 MPa are designated as UHSS.A forming tool is a machine tool or accessory with a shape that imparts a predetermined contour or profile to a workpiece, thereby reshaping the workpiece without adding or removing material, and leaving its mass unchanged. On the other hand, the present invention relates to a method for applying the inventive coating to a substrate. State of the art The use of advanced high-strength steels (AHSS) and ultra-high-strength steels (UHSS) in the automotive industry has steadily increased over the past few decades. AHSS are a series of high-strength steels that contain microstructural phases other than ferrite, pearlite, or cementite—for example, martensite, bainite, austenite, and / or retained austenite in sufficient quantities to produce unique mechanical properties. Most AHSS have a multiphase o / nRnn / Lznz / e / YiAi microstructure, and their yield strength typically exceeds 550 MPa. The use of these steels in the manufacture of a car's structural components (e.g., in the body-in-white (BIW) or chassis) results in a considerable reduction in the overall weight of a vehicle, since these structural components can be produced using thinner rolled metals while maintaining a high level of strength.One clear advantage is in car production, as these vehicles consume less fuel and are also safer in the event of an accident. This is because UHSS (Ultra-High Strength Steels) absorb significantly more impact energy compared to low-strength steels (LSS). LSS is a group of steels with a tensile strength below 270 MPa, examples of which include void-free steels and mild steels. However, forming UHSS and AHSS rolled metals is challenging and causes significant wear on forming dies, particularly continuous abrasive wear and / or adhesive wear, such as massive material transfer from the rolled metals to the die surface. In both cases, the quality of the produced parts is considerably affected. To maintain the quality of the manufactured parts, frequent maintenance intervals for the forming dies are required. The generation and development of fatigue cracks in the die can significantly reduce the service life of an expensive die. This results in lower productivity and excessive production costs. When using cold forming processes, one way to minimize damage to the die is to use different surface treatments, which can improve the performance of the forming dies. One of the most common and practical techniques from an industrial perspective is to use different nitriding methods, such as plasma nitriding or low-pressure nitriding, to harden the tool surface. This is achieved by diffusing nitrogen into the subsurface areas of the steel, resulting in increased resistance to abrasive wear and, in many cases, also to adhesive wear. Additionally, by introducing compressive stress to the surface, resistance to fatigue cracking is increased. The compressive stress arises due to volume changes resulting from the introduction of nitrogen and / or carbon, and due to thermal effects.As an alternative solution, several hard, wear-resistant coatings based on nitrides, carbides, oxides, or a combination thereof have been developed and are used industrially. The use of these coatings, either individually or in combination with nitriding solutions, could significantly increase the performance of forming dies used in the cold forming of, for example, uncoated HSS and UHSS rolled metals or rolled metals whose total tensile strength is not as high (e.g., less than 1000 MPa). The Swedish company Plannja has introduced a forming process, called pressure hardening or hot stamping, which will be used, for example, for forming coated sheet metal or sheet metal in general, with a total strength exceeding 1000 MPa (e.g., between 1000 MPa and 2000 MPa or between 1250 MPa and 2000 MPa). In this type of forming process, a hot, incandescent steel sheet is formed and tempered simultaneously in the same die. The entire forming process, including the tempering stage, is completed in just a few seconds, e.g., 8–12 seconds. As a result of this rapid tempering of the hot-formed part, a martensitic structure is formed, exhibiting a total strength of up to 2000 MPa. In recent years, the use of such pressure hardened steel (PHS) parts in the automotive industry, such as, e.g.A and B pillars, bumpers, roof racks and side steps, tunnels, and others, has increased dramatically from 3 million in 1987 to 250 million in 2015. Some of the advantages of using hot stamping processes compared to cold forming processes are: an elimination of elastic recovery of the material, which is usually seen in cold-formed AHSS sheets, a single-stage forming process, and excellent weldability of PHS parts due to the use of low-carbon alloys. In order to prevent corrosion of PHS parts, sheet metal materials are usually coated with AISi or Zn coatings before carrying out the hot stamping processes. However, some difficulties arise when using this process. The level of adhesive and abrasive wear on the dies in a hot stamping process is significantly higher than that which occurs in a cold forming process. One reason for this is the high forming temperature of approximately 800 °C, as well as a very high quenching rate of >27 degrees / s. This means that the sheet material undergoes a very rapid temperature change (e.g., a change from approximately 800 °C or more to approximately 150 °C in approximately 20 seconds or less), while during this temperature change, the sheet material remains in contact with the die (forming tool) used for its shaping. It is believed that the high forming temperature results in contact between the die and the semi-molten AISi or Zn coating of the coated sheet material (e.g.,(USIBOR sheet), resulting in considerable material transfer from the sheets to the die surface. Furthermore, high tempering rates lead to the formation of a very hard AISiFeO layer on the surface of the produced parts, causing abrasive wear of the die. Another common failure mode for coated dies in a hot stamping process is a process called continuous-burnish wear. Continuous-burnish wear is a type of wear caused by adhesion between sliding surfaces. When a material undergoes continuous-burnish wear, some of it is dragged along with the contact surface, especially if a large amount of force is compressing the surfaces together. Continuous-burnish wear results from a combination of friction and adhesion between surfaces, followed by sliding and tearing of the crystalline structure.Wear from continuous friction first causes an accumulation of material on the forming tool and eventually leads to the detachment of the accumulated material, including parts of the forming tool, such as lining pieces. Problem to solve There is a need to find a solution for hot stamping processes that prevents tool failure by adequately increasing the tool's resistance to abrasive and adhesive wear at temperatures up to and above 800 °C, particularly above 700 °C. Coatings exist that increase resistance to abrasive wear within a specific temperature range, as do coatings that increase resistance to adhesive wear within a specific temperature range. However, it is difficult to find a coating with high resistance to both abrasive and adhesive wear at temperatures up to and even above 800 °C, particularly above 700 °C. Objective of the invention An objective of the present invention is to provide a solution for improving the performance of forming tools used for hot stamping and thereby increasing tool life, especially for forming tools used in hot stamping of sheet materials coated or uncoated with AISi and Zn (such as USIBOR sheets). Solution to the problem according to the present invention - Description of the present invention The present invention proposes to provide a coating to be used to coat forming tools that are intended to be used in hot forming processes as described in claim 1. The present invention discloses a coating system that provides increased resistance to adhesive and abrasive wear when applied to a substrate, such as, for example, but not limited to, a steel substrate, used as a forming tool, and particularly suitable for pressure hardening processes. The inventive coating system is a multilayer system. It comprises at least one top layer (hereinafter also called the top multinanolayer or top layer or layer 5, as shown in Figure 1 and Figure 5) containing, but not limited to, CrN, TiAlN, and VCN. This top layer is characterized by a minimal carbon content relative to the nitrogen content, considering the carbon-to-nitrogen content profile throughout the layer. This top layer is primarily intended to provide resistance to continuous friction wear.The inventive coating system may comprise additional layers, in particular, at least one layer to provide the necessary load-bearing capacity, which is required to withstand the combination of mechanical loading and thermal shock during the forming and tempering stage in the hot stamping process. In general, additional layers can be applied to the coating to further improve various coating properties, such as adhesion to the substrate, cohesiveness within the coating structure, hardness (HIT), and modulus of elasticity (EIT). Furthermore, the coating must be resistant to the temperatures it will typically encounter during the hot forming process, as mentioned previously. Therefore, tests were conducted at temperatures commonly found in hot stamping processes, as demonstrated in several trials (temperatures between 800 °C and 950 °C). The inventive coating system can preferably be deposited using a PVD method, such as, e.g., cathodic arc or magnetron sputtering. o / nRnn / Lznz / e / viAi Description of figures Figure 1 Schematic illustration of an embodiment of the inventive coating system Figure 2 Schematic illustration of a possible method for depositing an embodiment of the inventive coating system Figure 3 Left: Scanning electron microscopy (SEM) micrograph of the coating of the invention taken by BSE Right: SEM micrograph of the coating of the invention taken with the InLens detector Figure 4 Schematic illustration of how a PVD-coated ball oscillates inside the AISi layer on top of the USIBOR sheet during the high-temperature SRV test Implementation of the present invention An inventive coating system for application to a forming tool used in pressure hardening is presented. This coating may be a single-layer or multi-layer coating, which is then deposited onto the surface of a substrate, e.g., a steel substrate associated with forming tools and forming members. The inventive coating system comprises at least one layer (referred to herein as the top layer or layer 5). The top layer itself (Layer 5 in Fig. 1) is a multilayer (also called a top multilayer), preferably a multinanolayer system (in the context of the description of the present invention also called a stack of top layers). The stack of top layers consists of at least three different classes of layers, e.g., layers of type A, layers of type B and C-type layers deposited forming a sequence ... A / B / C / A / B / C / A.... According to a preferred embodiment of the present invention, the top layer stack is deposited consisting of type A layers comprising mainly chromium nitride or consisting of chromium nitride CrN, type B layers comprising mainly aluminum titanium nitride or consisting of aluminum titanium nitride TiAlN, and type C layers comprising mainly vanadium carbonitride or consisting of vanadium carbonitride VCN. Especially good results were obtained using inventive coatings that had a stack of top layers comprising layers of CrN, TiAlN, and VCN. Therefore, a stack of upper layers is preferably designed having layers A, B, and C consisting of CrN, TiAIN, and VCN, respectively. In that case, preferably, the layer of the upper layer stack closest to the substrate is a layer comprising CrN, followed by a layer comprising TiAlN, followed again by a layer comprising VCN. However, the invention should not be understood as limited to the preferred embodiments described herein. The stack of top layers of the inventive coating system must comprise at least one set of layers. A set of layers in the context of the present invention is understood to be a sequence consisting of three unique layers: a layer A, a layer B, and a layer C deposited successively. It is important to note that when single layers A, B, and C are deposited successively as previously mentioned, an interface may form between two single layers deposited in contact with each other. Such an interface between two single layers may comprise elements of both layers. For example, when layer B is deposited onto layer A, an interface layer may form between layer A and the respective layer B, comprising elements of both. This will depend on the type of coating process used for the deposition of the upper layer stack. Preferably, and especially preferentially if the thickness of single layers A, B, and C is in the nanometer range, the top layer stack should contain a greater number of layer sets, typically between 25 and 600 layers. The total coating thickness of the top layer stack should be in the range of 0.5 µm to 12 µm, preferably between 2 µm and 7 µm. The inventors discovered that an inventive coating comprising this top layer exhibits excellent characteristics in terms of abrasive and adhesive wear resistance. Furthermore, the inventors observed that the composition of the top layer is critical for achieving optimal performance in terms of resisting material transfer from the AISi or Zn layer on the USIBOR sheets to the tool surface. In this regard, the carbon content is determined by the balance between resistance to buildup and maximum abrasive wear resistance. To improve adhesion between the top layer and the substrate of the forming tool, an adhesion layer (referred to herein as layer 1) can be deposited onto the substrate. This adhesion layer comprises CrN and preferably consists of CrN. It is preferably a monolayer, deposited directly onto the substrate. The thickness of this CrN layer is between 100 nm and 3 pm and is preferably selected to be between 300 nm and 1.5 pm. By depositing an additional layer comprising CrN and TiAlN, the performance of the inventive coating system can be further improved. This layer (hereinafter referred to as layer 2, or the second multilayer – see Fig. 1) is a multilayer, but it can also be a multinanolayer system (hereinafter also referred to as the CrN / TiAlN stack). The CrN / TiAlN stack is preferably deposited on top of layer 1, but it can also be deposited directly onto the substrate surface. Preferably, layer 2 is deposited by starting with a layer comprising CrN, preferably consisting of CrN. On top of this CrN layer, another layer comprising TiAlN is deposited. This TiAlN layer preferably consists of TiAlN. The CrN / TiAlN stack can comprise one or more assemblies consisting of two layers (a layer consisting of CrN and a layer consisting of TiAlN). In other words, the CrN / TiAlN stack comprises at least one CrN / TiAlN stack, but is not limited to one. Preferably, between 5 and 130 stacks are deposited to form the CrN-TiAlN layer (layer 2). The thickness of layer 2 can range from 150 nm to 4 pm and is preferably between 600 nm and 3 pm. This layer is known for its good load-bearing capacity (meaning its ability to withstand applied loads). The inventors discovered that the inventive coatings, comprising not only layer 5 but also the layers 1 and 2 described above, are well-suited for stamping processes. Forming tools coated in this manner generally exhibit good wear resistance in hot stamping processes compared to prior art coatings. The coating's resistance to abrasive and adhesive wear can be further improved by adding two more layers to the system (referred to here as layer 3, or the third multilayer, and layer 4, or the fourth multilayer). Surprisingly, the inventors discovered that within this system, it is beneficial to add a layer (layer 3) containing V and deposit it on top of layer 2. Layer 3 is a nanolayer system (referred to herein as the CrN / TiAlN / VN stack) comprising at least CrN, TiAlN, and VN. The CrN / TiAlN / VN stack comprises sets of three layers deposited on top of one another (see Fig. 1). Of these at least three layers, the CrN layer is closest to the substrate. This layer preferably consists of CrN. On top of this layer, a TiAlN layer is deposited. On top of this layer, a VN layer is deposited. To form an inventive coating system, at least one set is used to form Layer 3. However, this is not a limitation. Typically, between 4 and 80 sets are deposited to form the CrN, TiAlN, and VN layer. The thickness of this layer can vary from 20 nm to 4 μm and is preferably chosen to be between 800 nm and 3 pm. Layer 4 is also a multi-layer system, constructed like layer 3, but with carbon added gradually to change the layer from a VN to a VCN layer. This means that the lower part of layer 4 has a low carbon content, while the upper part has a high carbon content. The inventors discovered that wear resistance could be further improved by adding such a layer between layers 3 and 5. Layer 4 is a nanolayer system (referred to herein as the CrN / TiAlN / VN stack) comprising at least CrN, TiAlN, and VN, wherein carbon is gradually added to change the VN layer to a VCN layer. The CrN / TiAlN / VCN stack comprises sets of three layers deposited on top of one another (see Fig. 1). Of these at least three layers, the CrN layer is closest to the substrate. This layer preferably consists of CrN. On top of this layer, a TiAlN layer is deposited. On top of this layer, a VCN layer is deposited. To form an inventive coating system, at least one set is used to form layer 3. However, this is not a limitation. Typically, between 4 and 80 sets are deposited in order to form the layer containing CrN, TiAIN, and VCN.The thickness of this layer can vary from 20 nm to 4 pm and is preferably chosen to be between 800 nm and 3 pm. The inventors also noted that the inventive coating works best when the forming tool substrate is pre-nitrided. The nitriding process can be performed in the same deposition chamber or in a separate one. In order to clarify the accumulation of the inventive coating system, it will now be described by means of embodiments. One embodiment of the invention will be described by way of example, which is intended to be merely illustrative and therefore not limiting. According to a preferred embodiment of the present invention, shown in Figure 1, the multilayer system consists of five different layers, which are deposited onto the substrate of a forming tool. A layer of CrN (in this embodiment referred to as layer 1) is deposited directly onto the substrate. On top of layer 1, a layer (in this embodiment referred to as layer 2) consisting of CrN and TiAlN is deposited. On top of layer 2, a layer (in this embodiment referred to as layer 3) consisting of CrN, TiAlN, and VCN is deposited. On top of layer 3, a layer (in this embodiment referred to as layer 4) consisting of CrN, TiAlN, and VCN is deposited with a carbon content profile in gradients over layer 3. The topmost layer (in this embodiment referred to as layer 5) consists of CrN, TiAlN, and VCN, with a constant carbon content throughout the layer.The total thickness of the coating described in this embodiment can vary from 4 pm to 20 pm. The sum of the coating thicknesses of layers 4 and 5 preferably represents between 40% and 50% of the total coating thickness, but is not limited to this amount. As can be seen, layers 4 and 5 are carbonitride layers. Layer 4 is a transition layer from a pure nitride layer (third layer) to a carbonitride layer (fifth layer). Therefore, the carbon level increases and the nitrogen level decreases along the thickness of layer 4, as the distance of layer 4 from the substrate increases. In this respect, layer 4 is a compound of (CraTibAlcVd)?XCxNy)6 in which x and y are preferably adjusted as follows: 0 <x<0,33 y 0,67<y<1. La relación de metal (es decir, la suma de contenido de Cr, Ti, Al y V) a no metal (es decir, la suma de contenido de C y N) se elige preferentemente para que sea 0,72<λ / δ<1,27. Asimismo, el contenido de elementos metálicos individuales de Cr, Ti, Al, y V se ajusta preferentemente de la siguiente manera: 0,20<a<0,30, 0,05<b<0,15, 0,15<c<0,25, y 0,40<d<0,50 con a+b+c+d=1, preferentemente 0,20<a<0,30, b = 0,10, c = 0,20, y 0,40<d<0,50 con a+b+c+d=1. Layer 5 is a carbonitride compound with a constant composition of (CraTibAlcVd)x(CxNy)6 with 0.4 <x / y<0,6 y 0,65<λ / δ<1,1, preferentemente x / y=0,5, y λ / δ=0,72. El contenido de elementos metálicos individuales de Cr, Ti, Al, y V se elige de la siguiente manera: 0,20<a<0,30, 0,05<b<0,15, 0,15<c<0,25, y 0,40<d<0,50, preferentemente, a = 0,20, b = 0,10, c = 0,20, y d = 0,50. Layers 1, 2, and 3 are composed of nitride layers. These layers are stoichiometric nitrides with a metal-to-nonmetal ratio of 1. To deposit the coating system described in this embodiment, three different target materials—Cr, TiAl, and V—were used in an Oerlikon Balzers INNOVA deposition chamber, as shown in Figure 2. In addition to the elemental Cr and V target materials, the TiAl target was metallurgically prepared as a powder to achieve an Al-to-Ti weight ratio of approximately 2. Pure nitrogen gas was used in the chamber to produce layers 1 through 3. During the transition to layer 4, acetylene gas was also purged into the chamber. The acetylene flow rate was gradually increased while the nitrogen gas level was kept constant. Because acetylene gas exhibits very high reactivity, it must be introduced into the chamber as close as possible to the substrate to be coated. Since the objective was to generate a high carbon content in the coating, the acetylene gas was released in the immediate vicinity of the substrate.The same would apply to O₂, which also exhibits high reactivity. The situation, however, is different for N₂, which can be introduced into the chamber without such specialized arrangements, as it is less reactive than acetylene gas. This method resulted in a gradient layer 4 that begins as pure nitride and ends as carbonitride. The acetylene gas flow was kept constant throughout layer 5, so a carbonitride layer with a constant composition formed as the top layer. To form a layer with the desired structure and properties, a negative substrate polarization of 60 V was used through the first three layers. The negative substrate polarization was increased to 100 V during gradient layer 4. It was kept constant at -100 V through layer 5. Within the framework of the present invention, the properties and structure of the coating solution described in this embodiment were analyzed. Figure 3 shows scanning electron microscopy (SEM) micrographs taken using the conventional method as well as the InLens method. A CrN / TiAlN nanolayer was deposited on top of the bottom layer 1, which is a dense and uniform CrN layer. The hardness (HIT) and elastic modulus (EIT) of this layer were approximately 27 GPa and 300 GPa, respectively. The bilayer span of this nanolayer was measured at 35 nm. A CrN / TiAlN / VN nanolayer was deposited in layer 3. The mechanical properties of this layer were measured as 29 GPa for HIT and 340 GPa for EIT. The total thickness of the three nanolayers together is estimated at 55 nm. Finally, the upper layers containing C4 and C5 have HIT and EIT of 24 GPa and 250 GPa, respectively.The presence of C in these two layers has led to a refinement of the nanolayer structure, so that the thickness of three CrN / TiAIN / VCN layers is reduced by half to ~22 nm. The resistance of coatings to adhesive wear, defined as the transfer and accumulation of AISi or Zn from the coated USIBOR sheets onto the PVD coating surface, is measured using an innovative test method on an SRV test apparatus at high temperatures of ~730 °C. In this innovative method, a 10 mm diameter 100Cr6 steel ball was coated with an inventive PVD coating. As a counterpart, a round, AISi-coated USIBOR sheet, cut to a diameter of 21 mm, was mounted on a suitable high-temperature support. The USIBOR sheet was then heated via a resistance-heated table in contact with the sheet support. The temperature of the glowing USIBOR sheet was measured using a secondary thermocouple as 730 °C, compared to the SRV test apparatus's reference temperature of 900 °C.The temperature of 730 °C reached in the USIBOR sheet was high enough to bring the AISi coating to a semi-liquid state, identical to actual practice in industrial applications and suitable for build-up resistance studies. To represent the actual conditions of hot stamping USIBOR with AISi, test parameters such as the contact time between the ball and the USIBOR sheet, the vertical force applied to the ball, and its vibration frequency were adjusted to ensure that the coated ball remained within the depth of the AISi coating and never touched the underlying 22MnB5 steel. To meet this requirement, a vertical load of 10 N was used. The contact time between the coated ball and the AISi-coated USIBOR sheet was set at 1 minute before the next cycle began. Figure 4 shows a schematic representation of the test.This is done to simulate the contact of the coated tool with a new sheet metal part in an actual hot stamping application. By doing this, the volume and height of the AISi buildup on any desired PVD coating were measured using a Nanofocus 3D confocal microscope, resulting in a quantitative and qualitative assessment of that coating's buildup resistance. Depending on the performance of the tested coatings, this process could be repeated up to 20 times at the same point with a coated ball, followed by Nanofocus microscopy measurements. Using this unique testing method, the coating of the invention showed an order of magnitude lower o / nRnn / Lznz / e / YiAi buildup volume compared to conventional prior art AlCrN and TiAlN coatings deposited by an identical PVD method. The abrasive wear resistance of the coatings was measured using a high-temperature bolt-on-disc test setup. The maximum temperature reached in this test was 800 °C. For this purpose, a specially designed PVD coating was applied to a round Inconel sample, suitable for high-temperature measurement. Upon reaching the target temperature, a 6 mm diameter aluminum oxide abrasive ball was brought into contact with the PVD-coated Inconel sample. The ball's linear velocity and total contact time with the coated sample were 2.64 cm / s and 10 minutes, respectively. Finally, the wear profile of the surface was measured using a Nanofocus 3D confocal microscope, allowing for the measurement of the wear produced on the desired PVD coating. A coated substrate having a coating to provide increased resistance to abrasive and adhesive wear, wherein the coating has a multilayer structure comprising a deposited top multilayer, characterized in that the top multilayer is formed by sublayers of type A, B, and C, said three types of sublayers being deposited alternately on top of each other forming a sequence of type ...A / B / C / A / B / C / A..., characterized in that: - the type A sublayer is a chromium nitride layer, - The B-type sublayer is an aluminum titanium nitride layer, - the C-type sublayer is a vanadium carbonitride layer. Coated substrate according to the previous sentence, characterized in that the substrate is a shaping tool.

Claims

1. A coated tool for hot stamping coated or uncoated rolled metals, particularly for hot stamping rolled metals coated with AISi or Zn, comprising a coated substrate surface in contact with the coated or uncoated rolled metal, wherein the coating on the coated substrate surface is a multilayer coating comprising one or more lower layers and one or more upper layers, the lower layers being deposited closer to the substrate surface than the upper layers, characterized in that: the lower layers are designed to provide load-bearing capacity, the upper layers are designed to provide resistance to continuous friction wear, at least one upper layer (layer 5) is deposited having a multinanolayer structure formed by sublayers of type A, B, and C,These three classes of sublayers are deposited alternately on top of each other forming a sequence of the type ... A / B / C / A / B / C / A..., wherein at least two sequences of a nanolayer A, a nanolayer B and a nanolayer C are deposited forming the multinanolayer structure, wherein: - the type A nanolayer is composed of at least 90 atomic percent chromium and nitrogen, - the type B nanolayer is composed of at least 90 atomic percent titanium, aluminum and nitrogen, - the type C nanolayer is composed of at least 90 atomic percent vanadium, carbon and nitrogen, and - the thickness of the layer of the at least one upper layer (layer 5) is not less than 0.5 μιτ) and not greater than 15 pm.

2. Coated tool according to claim 1, characterized in that the sum of the layer thicknesses of three nanolayers A, B and C forming a sequence is between 15 nm and 300 nm, between 15 nm and 200 nm.

3. Coated substrate according to claim 1 or claim 2, characterized in that in at least one upper layer (layer 5), the average ratio of the carbon content fraction, x, to the nitrogen content fraction, y, is in the range of 0.4 <x / y<0,6, cuando se considera una composición de elementos químicos promedio en porcentaje atómico descrita por (CraT¡bAlcVd)x(CxNy)5, donde la composición promedio se mide considerando una extensión del espesor de capa de al menos 100 nm, con los coeficientes a, b, c y d correspondientes a las fracciones de composición de Cr, Ti, Al, V, C y N, en intervalos 0,20<a<0,30, 0,05<b<0,15, 0,15<c<0,25, y 0,40<d<0,50, respectivamente, con a+b+c+d=1 y x+y=1, y los coeficientes λ y δ siendo factores para la indicación de la estequiometría, donde 0,72<λ / δ<1,27.

4. Coated substrate according to claim 3, characterized in that in the at least one upper layer (layer 5), the average ratio of the carbon content fraction to the nitrogen content fraction, x / y, can be considered constant since the variation along the total thickness of the at least one upper layer (layer 5) is less than 10% of the maximum value.

5. Coated substrate according to any of claims 1 to 4, characterized in that an interface is formed between two sublayers deposited in contact with each other, wherein the interface comprises elements of both of the two sublayers.

6. Coated substrate according to any of claims 1 to 5, characterized in that the upper multilayer normally contains between 25 and 600 layers, wherein the total thickness of the coating of the upper multilayer is preferably in the range of 0.5 pm to 12 pm, more preferably between 2 pm and 7 pm.

7. Coated substrate according to any of claims 1 to 6, characterized in that an adhesion layer is deposited, preferably directly, on the substrate between the upper multilayer and the substrate, wherein the adhesion layer preferably comprises CrN, more preferably the adhesion layer consists of CrN.

8. Coated substrate according to any of claims 1 to 7, characterized in that a second multilayer is deposited on the substrate between the upper multilayer and the substrate, preferably between the upper multilayer and the adhesion layer according to claim 6, wherein the second multilayer preferably comprises CrN and TiAlN.

9. Coated substrate according to claim 8, characterized in that the second multilayer comprises between 5 and 130 assemblies formed by a layer consisting of CrN and a layer consisting of TiAlN, wherein preferably the thickness of the second layer ranges from 150 nm to 4 pm, preferably between 600 nm and 3 pm.

10. Coated substrate according to claim 8 or 7, characterized in that a third layer is deposited on top of the second layer, wherein the third layer comprises V, preferably the third layer is a nanolayer system comprising at least CrN, TiAIN and VN.

11. Coated substrate according to claim 10, characterized in that the third multilayer comprises between 4 and 80 assemblies for the purpose of forming the third layer comprising CrN, TiAlN and VN, wherein preferably the thickness of the third layer ranges from 20 nm to 4 pm, preferably between 800 nm and 3 pm.

12. Coated substrate according to claim 10 or 11, characterized in that a fourth layer is deposited on top of the third layer, wherein the fourth layer is a transition layer from a nitride layer to a carbonitride layer, wherein the carbon level increases and the nitrogen level decreases throughout the thickness of the fourth layer as the distance of the fourth layer from the substrate increases.

13. Coated substrate according to claim 12, characterized in that the fourth layer is a compound of (CraT¡bAlcVdÉ(CxNy)6 in which xey are preferably fitted as follows: 0 <x<0,33 y 0,67<y<1, en el que la relación de metal, en particular, la suma de contenido de Cr, Ti, Al y V, a no metal, en particular, la suma de contenido de C y N, se elige preferentemente para que sea 0,72<λ / δ<1,27, en la que el contenido de elementos metálicos individuales de Cr, Ti, Al, y V se ajusta preferentemente de la siguiente manera: 0,20<a<0,30, 0,05<b<0,15, 0,15<c<0,25, y 0,40<d<0,50 con a+b+c+d=1, preferentemente 0,20<a<0,30, b = 0,10, c = 0,20, y 0,40<d<0,50 con a+b+c+d=1.

14. Coated substrate according to any of the preceding claims, characterized in that the upper multilayer is a carbonitride compound with a constant composition of (CraTibAlcVd)Á(CxNy)s with 0.4 <x / y<0,6 y 0,65<λ / δ<1,1, preferentemente x / y=0,5, y λ / δ=0,72, en donde el contenido de elementos metálicos individuales de Cr, Ti, Al, y V se elige preferentemente de la siguiente manera: 0,20<a<0,30, 0,05<b<0,15, 0,15<c<0,25, y 0,40<d<0,50, preferentemente, a = 0,20, b = 0,10, c = 0,20, yd = 0,50.

15. A method for coating a coated substrate according to any one of claims 1 to 14, characterized in that a PVD method, in particular cathodic arc or magnetron sputtering, is used to coat the coated substrate.

16. Method according to claim 15, characterized in that the following steps are performed during coating: - the substrate is previously nitrided, in particular in the deposition chamber, - when optional layer 1, 2 and / or 3 is produced, pure nitrogen gas is present in the deposition chamber, where a negative substrate polarization of 60 V is used, - when optional layer 4 is produced, acetylene gas is further purged into the deposition chamber, where the acetylene flow is gradually increased while the nitrogen gas level is kept constant, where the negative substrate polarization is increased from 60 V to 100 V, - the acetylene gas flow is kept constant along the upper multilayer, whereby a carbonitride layer with a constant composition like the upper multilayer is formed, where a constant negative substrate polarization of 100 V is maintained.