EP3768876A1

EP3768876A1 - Method for producing improved cold-forming tools for high-strength and super-high-strength steels, and cold-forming tool

Info

Publication number: EP3768876A1
Application number: EP20726793.1A
Authority: EP
Inventors: Farwah Nahif; Mark Falkingham
Original assignee: Voestalpine Eifeler Vacotec GmbH
Current assignee: Voestalpine Eifeler Vacotec GmbH
Priority date: 2019-05-17
Filing date: 2020-05-15
Publication date: 2021-01-27
Also published as: DE102019113117A1; KR20220007162A; CA3140796A1; MX2021014035A; CN114072541A; US12146214B2; WO2020234186A1; CN114072541B; US20220205078A1; JP7340040B2; JP2022532680A; DE102019113117B4

Abstract

The invention relates a method for producing a cold-forming tool, in particular for the cold forming of super-high-strength steels, wherein the cold-forming tool is the upper and/or lower tool of a forming-tool set, wherein the cold-forming tool is formed from a metal material and has a mould surface which is designed such that a formed metal sheet has the desired final contour of the component, characterized in that a hard-material layer is deposited on the mould surface of the cold-forming tool by means of physical vapour deposition, wherein the hard-material layer constists of a titanium nitride bonding layer and, deposited on top of that, alternating layers of aluminium titanium nitride and aluminium chromium nitride, wherein as a last layer a titanium nitride top player or alternatively a titanium carbonitride top layer is deposited as an outermost outer surface facing the workpiece to be formed.

Description

Process for producing improved cold forming tools for high and ultra-high strength steels and cold forming tools

The invention relates to a method for producing cold forming tools, in particular re for cold forming high-strength steels and the cold forming tool for this purpose.

In the automotive industry in particular, there is an effort to make the body of vehicles ever lighter. In recent years, efforts have been made to this end, for example by press hardening process, to provide high-strength steel components that manage with comparatively low material thicknesses and thus weights due to their high strength. In the meantime, for reasons of environmental protection and the saving of fuel, the subject of lightweight construction has the highest priority among automobile manufacturers. In particular, so-called high, ultra high and ultra high strength steel materials are installed (UHSS - Ultra High Strength Steel, AHSS - Advanced High Strength Steel). High-strength steels within the meaning of the application relate to steel materials with a tensile strength of more than 350 MPa, in particular more than 600 MPa. In particular, components such as bumper reinforcements, side impact beams, seat frames and mechanisms and chassis components are made from such materials.

With such materials, the weight can be reduced by up to 40% compared to conventional components. In addition, costs can be reduced and production efficiency can be increased.

There are mainly two processes used in the forming of metals, namely hot forming and cold forming.

Hot forming refers to all those forming steps that take place above the recrystallization temperature of a metal. Generally these are lower Forming forces are necessary, and there is no work hardening of the workpiece during the forming process.

Here, AI203-based solutions are often used for hot forming tools, which, through the oxidic components, increase the hot hardness and oxidation resistance of the entire layer for the high temperature application of hot forming. However, these oxide layers are hard and brittle. Coatings on hot forming tools mostly aim to withstand the thermal load and also to act as a diffusion barrier.

A challenge in this context, however, is the cold forming of such high-strength steels.

Due to their properties, these materials oppose the forming tools with considerably higher forces than would be the case with conventional body steel.

Due to the high contact pressures that arise between the workpiece and the tool during the cold forming of high-strength steels, the tribological loads on the tools in particular are very high. For this reason, PVD layers are used in cold forming, the focus of which is on increasing the mechanical load-bearing capacity, increasing wear and reducing the spread of cracks, instead of using oxidic layers, as is the case with hot forming, which have a higher hot hardness in order to withstand thermal fatigue Tools to counteract it. Since long tool life is necessary for economic production, it must be ensured that wear is reduced due to the extremely high normal contact stresses. One approach here in cold forming is the pretreatment of the workpieces and, in particular, the addition of lubricants with a higher level of additives.

The addition of lubricants can have negative effects on the health of employees, since when using lubricant emissions can occur in the breathing air and on the skin of employees at the workplaces. In addition, cooling lubricants can be carried over into the area around the machine, which in turn worsens the ecological balance of the entire process. The object of the invention is to create a method with which cold forming tools can be made that show a reduced tendency to wear and with which the tool life can be increased significantly. Another object of the invention is to reduce the amount of lubrication required in forming processes, in particular high-strength steels.

The object is achieved with a method having the features of claim 1.

Advantageous further developments are identified in the dependent claims.

Another object is to create a corresponding cold forming tool.

The task is solved with a cold forming tool with the features of claim 9 ge.

Advantageous further developments are identified in the dependent claims.

The invention relates to the special requirements in cold forming processes due to the high forming forces, especially in the cold forming of high-strength steels. To meet these requirements, a multi-layer hard material layer is applied for the cold forming tool according to the invention, consisting of an applied titanium nitride adhesive layer and alternating layers of aluminum titanium nitride and aluminum chromium trite deposited thereon. This specific multilayer structure enables the strength and load-bearing capacity of the overall layer to be developed, which is required by the application of cold forming of high-strength sheet metal.

Furthermore, the crack growth through the entire layer, which is observed with the high loading forces of cold forming of high-strength sheets, can be stopped by the alternating layers of aluminum titanium nitride and aluminum chromium nitride by stopping the cracks at the transitions between the individual layers due to their different microstructures. A titanium nitride or alternatively a titanium carbonitride top layer is provided as the top layer to reduce the breakaway torque. In the description, a single level of the multilayer composite is referred to synonymously with layer or layer or layer.

The focus of the present invention is designed on the mechanical and tribological requirements of cold forming, in which the hot hardness and oxidation resistance of the entire layer and individual layers are negligible due to the application of cold forming. Oxidic layers are extremely hard and brittle. In cold forming, the main stress on the tool is generated by the high forming forces and strain hardening, which means that the use of oxidic layers, the advantages of which are thermal resistance, is less common and more focus is placed on wear-resistant, multilayer, nitride-based layers which will inhibit crack growth and increase mechanical strength. The use of oxidic layers in cold forming is also only possible to a limited extent, as the synthesis of e.g. AI203 layers for this application area requires the generation of the alpha-AI203 phase, which can only be achieved with the usual PVD / CVD processes from deposition temperatures> 1000 ° C. Due to the high deposition temperatures and the resulting thermal distortion and hardness reduction of the tools, only a limited number of tools for cold forming can be coated with these processes due to the near-net-shape specifications. A coating of the gamma-AI203 phase at temperatures <800 ° C for use in cold forming is only possible to a limited extent, as this does not have comparable mechanical properties and wear resistance as other nitridic PVD systems.

According to the invention, the surface of a cold forming tool, in particular for forming high-strength steels, is changed in that hard material layers with a reduced coefficient of friction are applied to the surface. The underlying idea is to offer better resistance to the local stresses by generating property gradients on the tool surface. The surface is provided with a higher hardness, for example, while the substrate tool ensures the required toughness.

In particular, according to the invention, a PVD hard material layer is deposited on corresponding tools. The production of PVD layers (Physical Vapor Deposition) has been known for a long time and is used in particular in tools, in particular in cutting tools.

A method commonly used for such hard material layers is the light arc evaporation, also known as arc PVD or arc evaporation. This process belongs to the group of physical vapor deposition (PVD) and is more precisely an evaporation process.

In this process, the cathode or the material to be vaporized is placed on a negative potential, with an arc burning between the chamber wall of the vacuum chamber (acting accordingly as an anode) and the cathode surface. The cathode contains the material that is later to be deposited on the workpiece, in this case on the tool, for example, with the cathode material in the plasma phase also being able to react with corresponding gases (reaction gases), for example through a suitable atmosphere in the chamber, to form a corresponding layer.

In this arc evaporation, a large part of the evaporated material is ionized, with the material spreading radially in a line-of-sight process from the cathode surface. A negative potential is also applied to the substrate, so that the ionized metal vapor is accelerated towards the substrate. The vapor condenses on the substrate surface, whereby a high kinetic energy can be introduced into the growing layer due to the high proportion of ionization and the negative bias voltage on the substrate. In this way, among other things, the properties, such as layer adhesion, density and composition, as well as the microstructure of the deposited layer can be influenced.

However, it is known that aluminum chromium nitride (AICrN) and aluminum titanium nitride (AITiN) layers can usually only be applied to the growing layer with a high proportion of macroparticle deposits (so-called "droplets") or high macroparticle formation when aluminum chromium cathodes evaporate This is expressed in so-called droplet / macroparticle inclusions within the growing thin layer and a correspondingly higher layer roughness. These droplets also form in monolithic designs of aluminum chromium nitride and aluminum titanium nitride layers. In addition, aluminum chromium nitride and aluminum titanium nitride layers have a comparative effect high layer hardness and a higher coefficient of friction in use However, higher layer roughness and the higher coefficients of friction can have a disadvantageous effect in the near-surface area during the forming of, for example, high-strength galvanized steel sheets and lead to welds that can reduce the tool life. The welds are an adhesive material transfer from the softer, formed material to the harder tool.

According to the invention, therefore, an additional thin titanium nitride top layer (TiN) is applied as the last layer, which through its reduced droplet deposits leads to a more uniform, smoother layer surface. Another property of the titanium nitride top layer is the lower coefficient of friction than the layers below. This reduces the risk of weld build-up and thus improves the running-in behavior of the layer in comparison to the harder aluminum titanium nitride and aluminum chrome multilayers underneath. Before geous enough, the running-in behavior is improved by the titanium nitride top layer due to its good sliding properties and its low breakaway torque (the force that is necessary to overcome static friction and initiate the transition to sliding friction). Surprisingly, the titanium nitride top layer absorbs some force with every stroke, since the titanium nitride top layer has better elasticity than the hard aluminum chromium nitride and aluminum titanium nitride layers underneath. A TiN top layer thinner than 0.1 μm does not lead to any improved running-in behavior. If the TiN top layers are too thick (thicker than 0.5 μm), the multilayer underneath can no longer show its advantageous properties, for example slower crack growth. TiN top layers with a thickness between 0.2 and 0.3 μm can be particularly distinguished. This represents an optimum of good running-in properties and slower tool damage, for example through the inhibition of crack growth.

Instead of the titanium nitride top layer (TiN), a titanium carbonitride top layer (TiCN) can alternatively also be provided. The use of the titanium nitride top layer (TiN) is to be preferred, for example, for the cold forming of coated, ultra-high-strength sheet metal, as these, due to their lower hardness compared to the titanium carbonitride top layer (TiCN), reduce the abrasion and thus the possible welding of the coating (e. B. electrochemically galvanized with zinc) of the ultra-high-strength sheet on the tool. Furthermore, the choice between the two top layers allows a color diversification for the user if this is desired, since the TiN top layer has a golden color and the TiCN top layer has a gray-bluish color. Advantageously, a titanium nitride adhesive layer (TiN) can also be deposited onto the tool to be coated first.

This adhesive layer can lead to a better connection of the subsequent multilayer coating. The TiN adhesive layer advantageously has a thickness of 0.2 to 0.9 μm. In the case of thicker layers than 0.9 gm, the internal stresses in the layer can be so high that the layer adhesion deteriorates. A titanium nitride adhesive layer 0.4 to 0.7 μm thick proves to be particularly advantageous; the best layer adhesion could be achieved here.

The upper limit can also be selected at 0.9 or 0.8 or 0.7 or 0.6 μm thickness.

The lower limit can also be selected at 0.2 or 0.3 or 0.4 or 0.45 μm thickness. For the application of the individual layers of the multilayer, aluminum chromium and aluminum titanium and titanium cathodes are preferably used, whereby nitrogen can be used as the reactive gas for the deposition of aluminum titanium nitride or aluminum chromium nitride layers (AITiN-AICrN multilayer systems). Due to their mechanical and thermal properties, these nitride hard material layers can have a wear-minimizing effect in relation to the extreme normal contact stresses and local thermal effects. It has proven advantageous to first deposit an aluminum titanium nitride layer on the optional TiN adhesive layer. This can improve the connection of the following multilayers.

The interplay of layers with different mechanical and thermal properties is u. a. beneficial to reduce crack propagation. The inventors have recognized that advantageously 5 layers each of AICrN and AITiN (ie a total of 10 layers) can effectively reduce the propagation of cracks. However, too many layers can have the disadvantage that with increasing layer thickness the internal stresses in the applied layer can become so high that layer adhesion problems can arise. It has advantageously been found that for this purpose the number of alternating layer layers 20 (that is to say in total 40 or 42 with TiN adhesive layer and TiN or alternatively TiCN top layer) should not be exceeded. 20 or 18 or 16 or 14 or 12 layers of AICrN and AITiN can also be selected as the upper limit for alternating layers. 5 or 6 or 7 or 8 or 9 or 10 layers of AICrN and AITiN can also be selected as the lower limit for alternating layers.

The individual aluminum titanium nitride layers can advantageously each be 0.1 to 0.5 μm thick. With layers thinner than 0.1 μm, the desired properties (somewhat more elastic than AICrN) of the hard material layer may not be achieved. Thicker layers in particular Those over 0.5 mih thick can have such high internal stresses that the layer adhesion deteriorates. Layer thicknesses between 0.2 and 0.3 μm can be particularly noticeable because they can already have a functional effect without introducing too high internal stresses. The upper limit can also be selected at 0.50 or 0.40 or 0.35 or 0.30 μm thickness.

The lower limit can also be selected at 0.10 or 0.15 or 0.20 μm thickness.

The individual aluminum chromium nitride layers can advantageously each be 0.1 to 0.5 μm thick. With layers thinner than 0.1 μm, the desired properties (resistant to abrasive wear, very hard, tougher than AITiN, high hot hardness - temperature stability up to approx. 900 ° C) of the hard material layer may not be achieved. Thicker layers, especially over 0.5 μm thick, can have such high internal stresses that the layer adhesion deteriorates. Layer thicknesses between 0.2 and 0.3 μm can be particularly noticeable because they can already have a functional effect without introducing too high internal stresses. The upper limit can also be selected at 0.50 or 0.40 or 0.35 or 0.30 μm thickness.

The lower limit can also be selected at 0.10 or 0.15 or 0.20 μm thickness.

In a particularly advantageous embodiment, a layer thickness combination of 0.2 to 0.3 μm in each case is selected for each aluminum chromium nitride and aluminum titanium nitride layer. The interplay between somewhat more elastic and somewhat tougher layers can, for example, slow down the growth of cracks and thereby ensure a longer service life of the tool.

The total layer thickness can be between 1.5 and 21 μm. The total layer thickness is preferably 10 to 11 μm. The thickness of the AITiN-AICrN multilayer system is preferably more than 5 μm, since the crack propagation is slowed down.

The chemical composition of the layers of titanium nitride (adhesive layer and top layer) is 40 to 50 atom% titanium and 50 to 60 atom% nitrogen, in titanium carboron nitride (alternative top layer) 20 to 23 atom% carbon, 30 to 33 atom% nitrogen and 44 - 50 atomic percent titanium, for aluminum chromium nitride 30 to 40 atomic percent aluminum, 10 to 20 atomic percent chromium and 45 to 55 atomic percent nitrogen and for aluminum titanium nitride 8 to 14 atomic percent aluminum, 30 to 40 atomic percent % Titanium and 40 to 50 atomic% nitrogen. In other words: Ti _z Ni _z with z = 0.4 to 0.6, Ti _x CyNi- ₍ x _{+ y)} with x = 44 to 50 and y = 20 to 23, remainder nitrogen, Al _a Cr _b Ni - _{(a + b)} with a = 30 to 40 and b = 10 to 20, remainder nitrogen and Al _c Ti _d Ni ( _{C + d)} with c = 8 to 14 and d = 30 to 40, remainder nitrogen. The layer structure according to the invention on the cold forming tool can be deposited using a duplex process (in-situ plasma nitriding and subsequent PVD coating). Preferred substrates are all materials that can be plasma nitrided, in particular metal materials, in particular HSS (high-speed steel) and hard metal. For the purposes of the applications, the metal material to be coated is referred to as the substrate. For this purpose, the applicant produces the coating systems alpha 400P and alpha 900P. With the duplex process, both work steps (plasma nitriding and PVD coating) are switched one after the other in one process without having to ventilate the system in between. During plasma nitriding, nitrogen diffuses into the edge zone, which increases the surface hardness of the tool material. The formation of interfering connection layers is suppressed. This means that the workpiece can be optimally prepared (good supporting effect) for the hard, brittle PVD coating that follows.

The invention thus relates to a method for producing a cold forming tool, in particular for cold forming ultra-high-strength steels, the cold forming tool being the upper and / or lower tool of a forming tool set, wherein the cold forming tool is made of a metal material and has a forming surface that is designed so that a formed sheet has the desired final contour of the component,

whereby a hard material layer is deposited on the forming surface of the forming tool via physical vapor phase separation, the hard material layer consisting of a titanium nitride adhesive layer and alternating layers of aluminum titanium nitride and aluminum chromium nitride deposited thereon, with the outermost outer surface facing a workpiece to be formed being the last layer Titanium nitride top layer or a titanium carbonitride top layer is deposited.

A further advantageous embodiment provides that an aluminum titanium nitride layer is first deposited on the titanium nitride adhesive layer as the first layer of the alternately deposited layers.

In another advantageous embodiment, five to twenty alternating layers are deposited on the titanium nitride adhesive layer before a final titanium nitride top layer or a titanium carbonitride top layer is deposited.

It is advantageous if the titanium nitride adhesive layer (2) has a thickness of 0.2 micrometers to 0.9 Micrometers, preferably from 0.4 micrometers to 0.7 micrometers.

It is also advantageous if the aluminum titanium nitride layers (3) have a thickness of 0.1 to 0.5 micrometers, preferably 0.2 to 0.3 micrometers.

The aluminum chromium nitride layers (4) advantageously have a thickness of 0.1 to 0.5 micrometers, preferably 0.2 to 0.3 micrometers.

In a further embodiment, the final titanium nitride top layer (5) or a titanium carbonitride top layer has a thickness of 0.2 to 0.5 micrometers, preferably 0.2 to 0.3 micrometers.

In another advantageous embodiment, the chemical composition of the layers is as follows: Adhesive and top layer Ti _z Ni _z with z = 0.4 to 0.6, as an alternative

Top layer Ti _x CyNi- _{(X + y)} with x = 44 to 50 and y = 20 to 23, remainder nitrogen, Al _a Cr _b Ni- _{(a + b)} with a = 30 to 40 and b = 10 to 20, Remainder nitrogen and Al _c Ti _d Ni (c _{+ d)} with c = 8 to 14 and d = 30 to 40, remainder nitrogen.

The invention also relates to a cold forming tool which has a hard material coating which is deposited according to the method described above.

An advantageous embodiment provides that the hard material layer is formed from alternating aluminum titanium nitride layers (3) and aluminum chromium nitride layers (4), with a titanium nitride top layer (5) or a titanium carbonitride top layer finally being present.

In another advantageous embodiment, the first layer on the tool is a titanium nitride adhesive layer (2) and then the aluminum titanium nitride layers (3) and aluminum chromium nitride layers (4) and the final titanium nitride top layer (5) or a titanium carbonitride top layer.

The invention is explained by way of example with the aid of a drawing. It shows:

Figure 1 shows an exemplary layer structure with a titanium nitride adhesive layer 2 on a

Substrate 1 with 15 alternating layers of aluminum titanium nitride layers 3 and aluminum chromium nitride layers 4 and a titanium nitride top layer 5 in a first embodiment; FIG. 2 shows an abstract dome section, ie a top view in which the individual layers can be seen;

FIG. 3 shows a metallographic comparison of model layers by means of dome grinding, which were applied to a sample in two different systems;

In Figure 1 is an exemplary layer structure with a titanium nitride adhesive layer 2 on a substrate 1 with 15 alternating layers of aluminum titanium nitride layers 3 and aluminum chromium nitride layers 4 and a titanium nitride top layer 5 in a first embodiment, where on the titanium nitride Adhesive layer 2 is followed directly by an aluminum titanium nitride layer 3.

In Figure 2, an abstract spherical cut is shown. When grinding a spherical cap, a ball grinds a spherical cap into the surface. If you grind through the multilayer down to the substrate, you can see the substrate in the innermost circle. You can see the model-like layer structures. First, a titanium nitride adhesive layer 2 is applied to the substrate 1, which improves the adhesion between the subsequent layers and the substrate 1. The titanium nitride adhesive layer 2 is advantageously followed directly by an aluminum titanium nitride layer 3. Subsequently, aluminum titanium nitride layers 3 and aluminum chromium nitride layers 4 alternate, these layers each being deposited 15 times and finally a titanium nitride top layer 5 being deposited.

In Figure 3 you can see the metallographic spherical grindings of two model-like layer structures that were applied to a cylindrical sample body made of the corresponding steel material. Layer structure as in FIG. 2. The coating system on the left was applied to an alpha 400P coating system from the applicant, the coating system on the right was applied to an alpha 900P coating system from the applicant.

The figures do not show the exemplary use of a titanium carbonitride top layer instead of a titanium nitride top layer.

The invention is explained below using a specific example:

The chemical composition of the layers in the example of titanium nitride consists of approx. 45 atom% titanium and approx. 55 atom% nitrogen, in the case of aluminum chromium nitride approx. 35 atom% aluminum, approx. 15 atom% chromium and approx. 50 atoms -% nitrogen, while aluminum titanium nitride contains about 11 atom% aluminum, 35 atom% titanium and 45 atom% nitrogen. A coating for cold forming tools is produced in the form of a multi-layer hard material coating, which is produced using PVD-ARC technology from the substrate 1 (tool base material, metal material) as a sequence of a TiN adhesive layer 2, an AITiN-AICrN multilayer system ( 15 individual layers) and a TiN top layer 5 is deposited and is able to improve the service life of the cold forming tool. The tool life is optimized because the PVD arc-based AITiN-AICrN multilayer system, due to its mechanical and thermal properties, has a wear-minimizing effect on the extreme normal contact stresses and local thermal effects during forming. The additional thin TiN top layer 5 promotes the running-in behavior of the layer and reduces the friction compared to the harder AITiN-AICrN multilayers underneath.

The 0.5 .mu.m thick TiN adhesive layer 2 is evaporated with an increasing substrate temperature ramp from 400 to 450 ° C and a decreasing substrate bias of 600-220 V and a Ver evaporator current of 60 A with the help of the reaction gas N2 at 1.2 * 10 ^{~ 2} mbar deposited. The composition of the TiN adhesive layer 2 is within the scope of the measurement inaccuracy: 45 atom% Ti and 55 atom% Al.

The 0.2 to 0.3 μm thick AITiN layer 3 of the AITiN-AICrN multilayer system starts with an Al-TiN layer with a higher Ti concentration, which is at 450 ° C substrate temperature, at 200 V substrate bias and simultaneous deposition of AITi -Cathodes at 55 A and Ti cathodes at 60 A with the help of the reaction gas N2 at 2 * 10 ^{~ 2} mbar. The composition of the AITiN single layer is within the scope of the measurement inaccuracy: 11 atom% Al, 35 atom% Ti and 54 atom% N.

The overlying 0.2 to 0.3 μm thick AICrN layer 4 of the AITiN-AICrN multi-layer system is at 450 ° C substrate temperature, at 80 V substrate bias and an AICr cathode current of 105 A with the aid of the reaction gas N2 at 2 * 10 ^{~ 2} mbar is deposited. The composition of the AICrN single layer 4 is within the scope of the measurement inaccuracy: 35 atom%

Al, 15 atom% Ti and 50 atom% N.

The AITiN 3 and AICrN individual layers 4 are coated 15 times in succession and produce the named AITiN-AICrN multilayer system. The 0.2 mih thick TiN top location 5 mbar is deposited at a substrate temperature rising to 450 ° C and a substrate bias voltage 80 V and a Ti-cathode current of 60 A with the aid of Reakti onsgases N2 at 2 * 10 ^{~ 2 only.} The composition of the TiN top layer 5 is within the scope of the measurement inaccuracy: 45 atom% Ti and 55 atom% Al.

The layer thickness of the overall layer composite in the example is 5-7 μm. The upper mold surface 6 is the tool surface facing the workpiece.

The layer properties and tool life were determined on a punching tool, since punching tests and the associated parameters are better defined than forming tests. All punching tests were carried out on an eccentric press (four pillar eccentric press, 15000kg). A punching tool made of cold work steel was coated in each case (with 0.7% by weight of carbon, 5% by weight of chromium, 2.3% by weight of Mo, 0.5% by weight of vanadium, 0.5% by weight Manganese, 0.2 wt.% Si and a hardness of 60 to 61 HRc). A 1.5 mm thick sheet of high-strength steel with a tensile strength of 1400 MPa was punched without additional lubrication.

Punching parameters:

Number of strokes: 160-170 strokes / minute

Feed rate (with 1.5 mm thick sheet steel): 8 m / min

Pressure: 72500-74000 N

The tool life was measured in comparison to an aluminum titanium nitride-based reference layer and the tool failure or the burr height on the punched workpiece / component was used as the termination criterion. I.e. if tool failure occurs, the wear on the edge areas of the tool is so high that a critical burr height is achieved on the workpiece / sheet steel. The aluminum titanium nitride-based reference layer achieved a critical burr height with 65,000 strokes and the tool coated according to the invention only achieved the critical burr height after 365,000 strokes. This corresponds to a 5-fold increase in service life.

Instead of the TiN top layer, a TiCN top layer can also be used. With a rising substrate temperature of 450 ° C and a falling substrate bias voltage from 150 V to 50 V and a falling Ti cathode current from 60 A to 42 A with the aid of the reaction gases N2 and CH at 2 * 10 ^{~ 2} mbar can be deposited. The The composition of the TiCN top layer is within the scope of the measurement inaccuracy: 20 to 23 atom% C, 30 -33 atom% N2 and 44 - 50 atom% Ti.

The advantage of the invention is that the service life could be increased significantly with the multilayer arrangement on a tool according to the invention.

Reference list

1 Meta II material, substrate (tool to be coated) 2 Titanium nitride adhesive layer (TiN adhesive layer)

3 aluminum titanium nitride layers (AITiN layer)

4 aluminum chromium nitride layers (AICrN layer)

5 Titanium nitride top layer (TiN top layer)

6 mold surface

Claims

1. A method for producing a cold forming tool, in particular for cold forming men high-strength steels, wherein the cold forming tool is the upper and / or lower tool of a forming tool set, wherein the cold forming tool is made of a metal material (1) and has a mold surface (6) which is designed so that a formed sheet has the desired final contour of the component, characterized in that,

that a hard material layer is deposited on the forming surface of the forming tool (6) via physical vapor deposition, the hard material layer consisting of a titanium nitride adhesive layer (2) and alternating layers of aluminum titanium nitride (3) and aluminum chromium nitride (4) deposited thereon, with as the outer surface facing a workpiece to be shaped is deposited as the last layer a titanium nitride top layer (5) or a titanium carbonitride top layer.

2. The method according to claim 1,

characterized,

that an aluminum titanium nitride layer (3) is first deposited on the titanium nitride adhesive layer (2) as the first layer of the alternately deposited layers.

3. The method according to any one of the preceding claims,

characterized,

that five to twenty alternating layers are deposited on the titanium nitride adhesive layer (2) before a final titanium nitride top layer (5) or a titanium carbonitride top layer is deposited.

4. The method according to any one of the preceding claims,

characterized,

that the titanium nitride adhesive layer (2) has a thickness of 0.2 micrometers to 0.9 micrometers, preferably 0.4 micrometers to 0.7 micrometers.

5. The method according to any one of the preceding claims, characterized,

that the aluminum titanium nitride layers (3) have a thickness of 0.1 to 0.5 micrometers, preferably 0.2 to 0.3 micrometers.

6. The method according to any one of the preceding claims,

characterized,

that the aluminum chromium nitride layers (4) have a thickness of 0.1 to 0.5 micrometers, preferably 0.2 to 0.3 micrometers.

7. The method according to any one of the preceding claims,

characterized,

that the final titanium nitride top layer (5) or a titanium carbonitride top layer has a thickness of 0.2 to 0.5 micrometers, preferably 0.2 to 0.3 micrometers.

8. The method according to any one of the preceding claims,

characterized,

that the chemical composition of the layers is as follows: Adhesive and top layer TizNi-z with z = 0.4 to 0.6, as an alternative top layer Ti _x CyNi- _{(X + y)} with x = 44 to 50 and y = 20 to 23, remainder nitrogen, Al _a Cr _b Ni- ( _{a + b)} with a = 30 to 40 and b = 10 to 20, remainder nitrogen and Al _c Ti _d Ni- (c _{+ d)} with c = 8 to 14 and d = 30 to 40, remainder nitrogen.

9. Cold forming tool with a hard material coating, which is deposited in particular according to a Ver drive according to one of the preceding claims.

10. Cold forming tool according to claim 9,

characterized,

that the hard material layer is formed from alternating aluminum titanium nitride layers (3) and aluminum chromium nitride layers (4), with a titanium nitride top layer (5) or a titanium carbonitride top layer finally being present.

11. Cold forming tool according to claim 9 or 10,

characterized,

that the first layer on the tool is a titanium nitride adhesive layer (2) and then the aluminum titanium nitride layers (3) and aluminum chromium nitride layers (4) and the final titanium nitride top layer (5) or a titanium carbonitride top layer.