EP1397526A2

EP1397526A2 - Modified diamond-like carbon (dlc) layer structure

Info

Publication number: EP1397526A2
Application number: EP02747332A
Authority: EP
Inventors: Reinhard HÖFER; Günther DURST
Original assignee: Saxonia Umformtechnik GmbH
Current assignee: Saxonia Textile Parts GmbH
Priority date: 2001-05-29
Filing date: 2002-05-29
Publication date: 2004-03-17
Also published as: WO2002097157A3; DE10126118A1; WO2002097157A2

Abstract

The invention relates to a wearing part which is comprised of a base material (51) and of a hard material layer (53), which is applied thereto and which contains carbon. Instead of being carbon steel, the base material is high alloy steel, particularly high alloy chrome steel. An inventive method for coating a base material of a wearing part with a hard material layer is characterized in that a mediator layer (52) is situated between the base material and the hard material layer and that the amorphous hard material layer containing carbon is applied by using a CVD method and/or a PVD method, in particular, inside the same reaction chamber used for subsequently applying the hard material layer.

Description

MODIFIED DLC LAYER STRUCTURE

I. Field of application

The invention relates to a wear part, the base material of which is protected by means of a very thin wear layer, which contains cross-linked amorphous (sp ² -binding part) and / or crystalline (sp ³ -binding part) carbon. Such carbon layers are called Diamond Like Carbon = DLC layer or Amorphheus Hydrogenetic Carbon = aC: H layer.

II. Technical background

The invention also relates to the method for coating the base material with such a hard material layer. These very thin, only a few μm thick hard material layers are deposited on the base material from the gas or plasma phase, either by chemical methods (Chemical Vapor Deposition = CVD) or by physical methods (Physical Vapor Deposition = PVD), the delimitation between the two types of process is sometimes difficult.

CVD:

Ions are made from a gas by energetic excitation, e.g. B. generated by means of high frequency or by means of DC voltage or pulsed voltage, which then cut off on the, lying on cathode potential, substrate. In addition to thermal CVD, in which the separation of gas ions is promoted by thermal energy, plasma-enhanced CVD (PE-CVD) plays a role in practice, in which the generation of ions from the gas by means of energy Coupling via radio frequency (eg 13.56 MHz) or via microwave frequency into (2.45 GHz).

PVD:

Ions are released from a target (solid, usually a plate, e.g. made of metal or non-metal) by means of physical influence, e.g. B. Bombardment by other ions that have been generated, for example, from a noble gas, preferably a heavy noble gas.

These physical processes (PVD) are usually classified according to their methods of atomizing the solid.

Conventional sputtering methods include DC sputtering, triode sputtering and ion plating

HF sputtering: The ionization of the sputtering gas is effected by applying a high-frequency voltage of a few kHz to MHz, with Me-a-C: H layers in particular pulsed in the 85-250 kHz range. The high-frequency coil can be arranged inside or outside the discharge chamber. In the latter case, the ions inside the chamber are additionally accelerated by an electric field.

The arrangement of double cathodes is also known.

The layers to be applied to the base material can consist of conductive or non-conductive material. It is also known to merely heat the substrates in a preliminary stage and to etch them by ion bombardment, ie to remove oxide layers, the bombardment being carried out by ions of an inert, heavy sputtering gas, usually an inert gas.

Bias sputtering:

In contrast to the previous methods, the substrate to be coated is isolated from ground and given a small negative bias of 50 to 500 V compared to the plasma. As a result, the growing layer is constantly bombarded with sputter gas atoms, and the growing layer is thus cleaned of adsorbed gas particles.

Combining bias sputtering with alternating current (AC) sputtering is also known, in which, in contrast to DC sputtering, the anodes and cathodes change constantly, and as a result both electrodes are removed evenly.

If you shift the zero potential in one direction, the AC voltage is superimposed on a DC voltage (bias). The cathode is more strongly bombarded than the anode, so that a net film grows on the anode.

Combination methods from CVD and PVD are also known, e.g. B.

Reactive sputtering: At least one component of the layer to be applied to the substrate does not come from the target but from the gas phase. A reactive gas is therefore introduced into the reaction chamber, which reacts chemically with the target material or the atoms knocked out of it and then deposits as a chemical product on the substrate.

The reaction can still take place on the target, then the reaction product is sputtered off, or only on the substrate itself when it is deposited. If the pressure in the chamber is high enough, the chemical reaction can also take place in the plasma.

In this way, even very complicated connections can be deposited as a layer structure, for example by metal targets are used and the remaining components are specified in the gas phase. In particular, metal carbides, nitrides and oxides are deposited in this way.

Cathode sputtering using magnetron sputtering:

In this case, a magnetic field is superimposed on the electric field that is generated during cathode sputtering, for example by arranging permanent magnets behind a cathode plate.

As a result, the charge carriers in the plasma no longer move essentially parallel to the electrical field lines, but rather transversely or in the form of a garland or helically or helically.

Due to the resulting higher charge carrier density, the DC discharge voltage is reduced to 200 to 600 V and the target load capacity can be increased from, for example, 5 to 10 W / cm ² in the case of diode sputtering to 25 W / cm ² .

One of the main difficulties here is not in the basic production of a hard material layer with the desired hardness or material composition, but in the sufficient adhesion of this hard material layer to the base material, which is also strongly influenced by the type of base material.

In the past, different layer structures with one or more intermediate layers between the base material and the actual hard material layer have been proposed for this purpose in order to solve these adhesion problems. In the past it was used for thread-guiding elements a metallic base material - from carbon steel, i.e. a steel that has no essential (more than 1, 0 percent by weight) other alloy components apart from carbon, because of its good formability, low price, large range in different shapes and dimensions, many for Alloys available, good spring properties, good hardenability and good galvanic coatability.

This was obvious from the past, since carbon steel had always been used as the basic material in previous metal parts.

Nevertheless, one or even two intermediate layers as a mediator layer between the base material and the hard material layer have been necessary for a good durability of the hard material layer, the base material in particular having to be completely coated, since remaining free areas were susceptible to corrosion, and thus also the covering layer, for example the intermediate layer, must not be susceptible to corrosion.

Another disadvantage was the low tempering resistance, which only gave a hardness of 54 to 56 HRC when tempered to 200 degrees Celsius to 220 degrees Celsius.

In addition, it was difficult with the previous coating methods to coat complex geometries, for example inner diameters and their edges, evenly and without gaps.

III. Presentation of the invention

a) Technical task

It is therefore the object of the present invention to create a wearing part with an applied hard material layer or a method for producing such a wearing part which, despite being simple and easy to manufacture Layer structure maintains or improves its good adhesion and wear resistance.

b) solving the problem

This object is solved by the features of claims 1 and 15.

Advantageous embodiments result from the subclaims.

There was previously a technical prejudice when coating thread-guiding elements in such a way that such DLC or a-C: H layers can only be applied to carbon steel with good adhesion for this purpose.

According to the invention, however, it has been shown that this also applies to at least partially corrosion-resistant and / or acid-resistant steel, in particular a high-alloy steel such as high-alloy chromium steel, which contains at least 10% by weight, preferably at least 12% by weight, of chromium. is possible.

In particular, such an application is possible on base material of steel grade 1.4110 according to DIN 17007 (= alloy X 55 Cr Mo 14).

In particular, such a steel is used as the base material, which does not drop tempering after hardening at a tempering temperature of 500 ° Celsius below a hardness of 54 HRC, in particular not below a hardness of 50 HRC.

The coating of the base material, that is to say either directly the hard material layer or a mediator layer arranged, in particular only, between the base material and hard material layer, is located directly on the bare metal, non-oxidized surface of the base material. If such a mediator layer is present, this is preferably only a single layer which contains in particular silicon and / or a carbide former (Ti, Cr, W, Zr, Hf, V, Nb, Ta, Mo), in particular of 30% by weight % to 100% by weight, in particular the majority, in particular in the case of a metal carbide in the areas close to the substrate. This intermediate layer is then likewise applied by means of CVD or PVD, in any case by means of deposition from the gas or plasma phase or by sputtering, and not galvanically by means of chemical or electrolytic deposition, that is to say by means of wet plating.

The mediator layer contains either silicon, in particular silicon carbide, or a pure metal, in particular a metal carbide.

The hard material layer itself consists of at least 30 percent by weight, in particular mostly of carbon or a mixture of non-metal components (Si, F, O, N, Br, Cl) and carbon. It can also contain metal ions (Ti, Cr, Zr, Hf, V, Nb, Ta, Mo), in particular in an amount of 5 to 40% by weight, in particular 10 to 30% by weight, in particular 15 up to 25% by weight of the total weight of the hard material layer.

The hard material layer has a thickness of 1 to 10 μm, in particular 2 to 4 μm, while a mediator layer - if present - has a maximum thickness of 1 μm, in particular a maximum of 200 nm, and is ideally as thin as possible.

Furthermore, the outside of the finished coated wear part should have a light color, at least over a part of the surface, in particular a metallic sheen.

This can be achieved by an additional cover layer on the hard material layer, or by having the hard material layer, at least in its outermost one

Area that has such a light color or metallic shine. The hard In addition to carbon and hydrogen, the material layer can also contain non-metal ions instead of metal ions.

A silicon content, in particular from 10% by weight to 30% by weight, in particular in the form of silicon carbide or silicon oxide, increases the temperature resistance.

Other embedded metal and / or non-metal ions influence the color, the coefficient of friction, the wetting behavior, the inherent voltage, the electrical conductivity, the temperature resistance or the transparency.

It is therefore possible not to form the cover layer as a separate layer on the hard material layer, but to change the doping in the course of the structure of the hard material layer in the direction of those ions which give the desired color effect, that is to say also brightening.

In particular, HF cathode sputtering by magnetron sputtering is shortlisted, with the aid of which metals which have the desired light color and even the metallic sheen can be applied simply and inexpensively.

Such an outer cover layer can in particular also, for. B. galvanically, by wet pasting, applied and in particular consist of nickel.

In addition, the mediator layer and the hard material layer are not necessarily to be regarded as a precisely delimited layer, but by changing the process parameters when the layer is deposited on the substrate, in particular the type and composition of the gas filling in the reaction chamber, a gradual, smooth transition between the mediator layer can occur and hard material layer, and can also be achieved between hard material layer and cover layer. That is why the top layer is classified as a separate layer or to be regarded as equivalent as a gradual transition within the hard material layer.

The main focus of the procedure for applying the coating is to be able to carry out the application of different layers as far as possible with the same system, in particular in one and the same reaction chamber, in the sense of an inexpensive application.

Two methods are usually used for this, that of reactive HF cathode sputtering by magnetron sputtering in combination with the HF-PE-CVD method (plasma-assisted CVD under high frequency).

Above all, the cleaning of the surface of the base material to a metallic bright state, in particular of any oxide layer or other contaminants, should also be carried out with the same system and in particular in the same reaction chamber in order to run the process quickly and inexpensively to let.

This is achieved by ion-etching the surface of the base material as a first step, by exposing the surface of the base material to ions or atoms of a heavy, low-reaction gas or plasma, in particular a noble gas, with the exclusion of oxygen. The next step is preferably to proceed directly to the layer structure, for example by changing the gas in the reaction chamber, which in particular takes place again in a flowing transition.

If a mediator layer is not applied directly, but rather a mediator layer, it is possible to switch between a CVD process and a PVD process, even several times, when applying the mediator layer and hard material layer. The same applies to the change from the hard material layer to the outer cover layer.

The entire process, that is to say from the cleaning of the surface of the base material to the application of the cover layer including, is preferably carried out in one and the same reaction chamber in an uninterrupted process with fluid change of the process gases and fluid change of the other process parameters, continuously with the exclusion of air , especially under exclusion of oxygen, is working and / or under negative pressure.

c) working examples

An embodiment according to the invention is described in more detail below by way of example. Show it:

Fig. 1: a layer structure and

Fig. 2: a process apparatus.

Fig. 1 shows a fully coated wear part in cross-sectional view greatly enlarged.

A mediator layer 52 with a thickness of 500 nm is applied to the outer surface of the base material 1, and a hard material layer of 3.5 μm is applied to this. In the outer area of this hard material layer, this is formed to cover layer δ 4 with a thickness of again 500 nm. The base material 51 is a rust and acid resistant steel of the grade 1.4110 according to DIN 17007 (= X55CrMo14).

The mediator layer 52 is made of silicon carbide (). The hard material layer 53 - with the exception of the cover layer (°) 54 - consists of highly cross-linked amorphous carbon (°), hydrogen and silicon in a weight ratio of 70% to 20% to 10%.

In the cover layer 54, the silicon and / or the hydrogen and / or the carbon is replaced by metal ions (X).

Fig. 2 shows a coating system in section in a schematic diagram.

In a coating chamber, the so-called plasma chamber 1, a plate-shaped, electrically insulated substrate holder 12, which is movable in the direction of the main plane 23, is arranged on the main plane 23, which is simultaneously the longitudinal center plane of the plasma chamber 1 and the plane of symmetry with respect to the magnetron cathodes described later.

The plasma chamber 1 has a suction nozzle 21, to which a vacuum pump 11 is connected, which can evacuate the plasma chamber 1 and also has a gas inlet which can be shut off by means of a valve 13. Outside the valve 13, the gas inlet branches into several, in particular three, arms, which can each be closed by an inlet valve 14, 15, 16 and through which different gases can be introduced into the plasma chamber 1.

Due to the controllability of at least the valves 14-16 of the individual branches, in particular also the valve 13, the desired composition and quantity of gases can be set.

The wear parts (not shown in the figure) for coating are fastened on the substrate holder 12, preferably on both sides. The electrically insulated substrate holder 12 is wired to a controllable via a matchbox 17

High-frequency generator 18 connected. By the high frequency generator 18 it is possible to also deposit electrically non-conductive layers and to coat electrically non-conductive substrates.

Matchbox 17 is used to optimally couple the power emitted by the HF generator into the plasma.

On both sides of the substrate holder 12, a preferably flat magnetron cathode 7, 22 is positioned near the outer walls of the plasma chamber 1 as a so-called double cathode arrangement, opposite which the substrate holder 12 and, above all, the substrates, not shown, attached thereon are arranged.

The magnetron cathodes 7, 22 are constructed identically as follows:

On the side facing the substrate holder 12 there is a plate-shaped target 8, on the back of which a cooling system 6 rests as far as possible. The cooling system 6 serves to dissipate the heat generated in the target 8 during sputtering, and consists of a non-magnetizable material, for example in the form of a hollow profile, through which a cooling liquid preferably flows.

On the back of the cooling system, a magnet arrangement is arranged, consisting of individual permanent magnets 2, 3, 4, the polar direction of which (from the north to the south pole) within these magnets 2, 3, 4 extends transversely to the plane of the target 8.

The magnets 2, 3, 4, which are spaced apart in the direction of the main plane 23, have mutually opposite pole arrangements, so that an electrical flow from the ends of the magnets 2, 3, 4 facing the substrate holder to the adjacent magnet in the form of a semicircle or one Half ellipse results.

On the back facing away from the target 8, the magnets 2, 3, 4, however, are by a composite plate placed on the back of the magnets, which as Flußleitstück 5 serves, connected so that the magnetic flux takes place on the back of the magnets via the composite plate 5.

The target 8 is connected to a high-frequency generator 10 via a matchbox 9, which fulfills the same purpose as the matchbox 17 in the substrate holder 12, or also to a pulse generator or a DC voltage source.

LIST OF REFERENCE NUMBERS

1 plasma chamber

2, 3, 4 magnets

5 flow guide

6 cooling system

7, 22 magnetron cathode

8 target

11 vacuum pump

12 substrate holder

13 valve

14 - 16 inlet valves

17 matchbox

18 high frequency generator

21 suction nozzle

23 main level

51 base material

52 mediator layer

53 hard material layer

54 surface layer

Claims

1. Wearing part made of a base material (51) and hard material layer (53) applied thereon, which contains carbon, characterized in that the base material (51) is high-alloy steel, in particular high-alloy chrome steel, instead of carbon steel.

2. Wearing part made of a base material (51) and hard material layer (53) applied thereon, which contains amorphous carbon, characterized in that between the base material (51) and the hard material layer (53) one, in particular only, mediator layer (52) located.

3. Wearing part according to claim 2, characterized in that the mediator layer (52) up to 30 wt .-%; contains in particular more than 10% by weight of silicon and / or up to 100% by weight of a carbide former (Ti, Cr, Zr, Hf, V, Nb, Ta, Mo).

4. Wearing part according to claim 2 or 3, characterized in that the mediator layer (52) in the areas close to the substrate, in particular in the case of a metal carbide in the mediator layer, no layer between the mediator layer (52) and the base material (51) is applied by wet patting.

5. Wearing part according to one of the preceding claims, characterized in that the high-alloy steel contains 10 to 20% by weight, in particular 12 to 17.5% by weight, chromium.

6. Wearing part according to one of the preceding claims, characterized in that the base material (51) is so resistant to tempering that it has a hardness of not more than 50 HRC (hardness according to the Rockwell scale) when tempered to a temperature of 500 degrees Celsius. , especially not further than 54 HRC.

7. Wearing part according to one of the preceding claims, characterized in that the mediator layer (52) and / or the hard material layer (3) is arranged directly on a bare metal, not oxidized, surface of the base material (51).

8. Wearing part according to one of the preceding claims, characterized in that the mediator layer (52) contains silicon in combination with carbon, in particular as silicon carbide SiC.

9. Wearing part according to one of the preceding claims, characterized in that the mediator layer (52) contains metal ions, possibly with carbon, in particular as metal carbides.

10. Wearing part according to one of the preceding claims, characterized in that the hard material layer (53) is applied directly to the mediator layer (52).

11. Wearing part according to one of the preceding claims, characterized in that the hard material layer (53) contains metal ions in addition to amorphous carbon, in particular contains more than 20% by weight, in particular the majority.

12. Wearing part according to one of the preceding claims, characterized in that the hard material layer (53) contains, in addition to amorphous carbon, non-metal ions, in particular up to 10% by weight, in particular up to 30% by weight of the hard material layer (53).

13. Wearing part according to one of the preceding claims, characterized in that the wearing part has at least over a part of its surface as the outermost layer a cover layer (54) of light color, in particular metallic gloss.

14. Wearing part according to one of the preceding claims, characterized in that the thickness of the cover layer (54) is at most 2 μm, in particular at most 500 nm, and in particular the cover layer consists of metal.

15. Wearing part according to one of the preceding claims, characterized in that the mediator layer (52) has a thickness of at most 1 μm, in particular at most 200 nm, and is in particular as thin as possible.

16. Wearing part according to one of the preceding claims, characterized in that the hard material layer (53) has a thickness of 1 to 10 microns, in particular of 2 to 4 microns.

17. Wearing part according to one of the preceding claims, characterized in that the hard material layer (53) has a metallic sheen on the outside as a cover layer (54), which is caused in particular by the incorporation of metals in the outer regions of the hard material layer (53).

18. A method for coating a base material (51) of a wearing part with a hard material layer (53), a mediator layer (52) being located between the base material (51) and the hard material layer (53), and wherein the hard material layer (53) containing amorphous carbon is applied by means of a CVD method and / or by means of a PVD method, characterized in that the previous application of the mediator layer (52) on the base material (51) by means of CVD or by means of PVD, but in particular in the same reaction chamber as the subsequent application the hard material layer (53) takes place.

19. The method according to any one of the preceding method claims, characterized in that the application of the mediator layer (52) as well as the application of the hard material layer (53) takes place, in particular by deposition from gases containing carbon.

20. The method according to any one of the preceding method claims, characterized in that the application of the mediator layer (52) takes place by means of the same method as the application of the hard material layer (53).

21. The method according to any one of the preceding method claims, characterized in that the application of the mediator layer (52) by sputtering, in particular metal

Sputtering, by means of PVD, followed by a transition to the deposition of metal carbides by reactive sputtering, and the hard material layer (53) by means of

Plasma-assisted CVD, especially under high frequency, is applied.

22. The method according to any one of the preceding method claims, characterized in that prior to the application of the mediator layer (52) on the base material (51) the surface of the base material (51) is cleaned of any oxide layer which may be present, in particular by bombardment with ionized atoms a heavy noble gas is cleaned, and remains in the absence of air until the application of the first layer.

23. The method according to any one of the preceding method claims, characterized in that the surface of the base material is cleaned of oxide layers in the reaction chamber, in which subsequently at least the application of the hard material layer (53), in particular also the application of the mediator layer (52), he follows.

24. The method according to any one of the preceding method claims, characterized in that the application of a cover layer (54) as the last layer, in particular a metal layer, takes place in the same reaction chamber as the application of the mediator layer and the hard material layer.

25. The method according to any one of the preceding method claims, characterized in that the application of a cover layer (54) as the last layer by means of wet plating, in particular by means of electrodeposition.

26. The method according to any one of the preceding method claims, characterized in that the application of all layers on the base material (51) takes place in succession in the same reaction chamber in an uninterrupted process with a flowing change of the process gas.