DE102006029415A1 - Wear-resistant coating and manufacturing method thereof - Google Patents

Abstract

The invention relates to a wear-resistant coating for a machine part which is exposed to frictional wear, with a carbon-based, hydrogen-containing functional layer (4), which is nanostructured, for example by different successive layers (60, 61, 62) with thicknesses in the nanometer range or embedded nanoparticles (63, 64).

Description

The Invention is in the field of tribology and deals with the coating of machine parts to reduce friction losses and wear. The present invention is basically up Many different types of machine parts applicable to a grinding Exposed to wear are. However, a particularly advantageous example is the use in parts of internal combustion engines, in particular valve train components such as tappets used. An application in industrial use such as in Rolling bearings and linear guides is however also conceivable.

Basically the requirements for such components by increasing mechanical loads, movement speeds and service life higher and higher. Increasingly lower maintenance intensity is assumed. Appropriate Lubricants are becoming increasingly environmentally friendly used with fewer and fewer additives and the trend is partial to low-viscosity lubricants or even for operation without lubricants.

The corresponding requirements for low frictional forces and adhesion both in the liquid-lubricated, as well as in dry and transitional areas, low adhesion forces, high wear resistance and at the same time toughness against impact loads and the resilience against spalling are not by conventional coatings more fulfilled.

Partially can single of the requirements by specific type of coatings Fulfills be such as the hardness or the low frictional resistance, however, regularly suffer other properties of the tribological system.

Especially this becomes clear in the example of valve trains in internal combustion engines, where particular attention is paid to cam follower devices lies.

such Cam follower devices are for example in automotive engines with reciprocating Pistons are installed, which have air inlet and outlet valves, which is in phase with the rotation of the crankshaft or synchronous open this and close. A valve drive mechanism is used to transmit the movement of the used on the camshaft cam on the valves, when the camshaft coincides with the crankshaft of the engine rotates. In this case, the cam of the camshaft comes in frictional contact a tread the associated bucket tappet.

Generally are subject to such valve train components, such as Cup and pump plunger rising Conditions. The causes for the need for increased wear resistance lie in the higher and higher expectant loads and stresses of the tribological system, consisting of control cams and tappets. The causes are in new engine concepts, such as gasoline and diesel direct injection systems, with constantly increasing injection pressures, an increasing proportion on abrasive particles in the lubricant, lack of oil supply the friction partner, which increased Contribution to mixed friction and increasing use of tribologically unfavorable Steel cams for cost and mass reduction. An important contribution to conserve resources is the reduction of friction losses in the valve train, with consequent fuel saving while increasing the Lifetime of the entire valve train. To the friction losses To effectively reduce, it is not agile, the friction torque over a lower wide speed range.

It is known, such bucket tappets for the valve control an internal combustion engine as a light metal plunger, which form a Pusher body and one at the contact surface for the control cam the valve control has inserted steel plate with a hardened surface.

adversely However, this approach has revealed the fact that such bucket tappets during operation relatively large Temperature fluctuations of -30 ° C at cold start up to approx. 130 ° C while are exposed to the operation of an internal combustion engine. Problematic Here is the difference in thermal expansion the materials used. Although has the inserted as an insert in a light metal ram Steel plate good wear characteristics but, with appropriate thermal stress, it tends to Peel off. The Thermal load capacity is therefore limited. Another application technology Disadvantage is that the space in the form of a relatively wide Edge as functional surface or as a cam contact surface, which is contacted by the control cam of a valve control, get lost.

According to the state It is also known in the art to expose treads to abrasive wear Machine parts with wear protection layers to provide, depending on the application preferably from galvanic applied metals or from in a thermal spraying process applied metals and / or metal alloys optionally with hard material additives consist.

In this case, however, the fact has proved to be disadvantageous that thermally sprayed te metal layers have a relatively weak strength, and it is therefore known to improve the strength to remelt the metal layers after application, for example, by plasma blasting, laser beams, electron beams or by an arc such that the spray materials melt with the case simultaneously melted in the surface area base material mix and alloy. In addition, the thermally sprayed and thus rough coatings must be mechanically reworked to have good trochological properties. In remelting, however, inhomogeneous zones of different composition arise in which both the base material and the layer material can predominate. If the base material content is too high, then the layer wear will be too high, and with a low base material content there will be a risk of macrocracking in the case of different layer combinations, so that such layers can not be used. In such a case, frictional stresses can cause undesirable adhesive wear on the layers.

Further it is known the tread of the tappet by means of carbonitriding and / or nitrocarburizing a thermochemical process. However, it has proved to be disadvantageous that no satisfactory Friction coefficient is achieved and too low wear resistance arises.

Besides that is known, the tread the plunger with to coat a manganese phosphate layer or a lubricating varnish. Again, no satisfactory coefficients of friction and wear resistance achieved. In addition, such materials pollute the environment unnecessarily. The same applies to galvanic layers, which are also applied to the treads can be.

It are also known in the art as coating materials Hardmetals and high speed steels (ASP 23) are known, however besides an unsatisfactory coefficient of friction and an unsatisfactory wear resistance in addition to a have a disadvantageous high mass.

Besides, they are hard, for example, by a PVD or a (PA) CVD method produced Layers such as TiN, CrN, (Ti, Al) N, known. adversely However, this approach has revealed the fact that These layers result in high wear of the counter body if these layers are not post-processed. In the event of Postprocessing results in undefined surface conditions due to the reactive surfaces.

From the U.S. Patent 5,237,967 are known carbon-based PVD and (PA) CVD layers with 20 to 60 atom% of hydrogen in the top layer, so-called metal-containing hydrocarbon layers (aC: H: Me) and amorphous hydrocarbon layers (aC: H). However, these layers have a relatively low wear and fatigue resistance and are therefore not suitable for highly stressed components in new engine generations and offer a relatively low reduction in friction during operation.

As already explained above, is a friction reduction in the valve train a necessary contribution to Fuel saving and resource conservation. This goal can be achieved be reduced by reducing the area of solid and mixed friction and thus the field of fluid friction with complete Material separation increased. This is achieved by a possible optimized overall roughness of the tribological system consisting of Tappets and Camshaft.

Around the one for this necessary optimal surface structure the tappet over the To obtain a lifetime, it is necessary to the surface so too Design that they have a high wear resistance, a low adhesive tendency to against body and low reactivity to the environment. Furthermore, the surface may preferably not be abrasive Contain particles, such as droplets.

The Tappers off Iron carbon alloys, whether or not in the heat-treated state, such as carbonitrates, Nitrocarburised or nitrided, do not reach the necessary Wear resistance and tribologically favorable Surface states. treated For example, nitride layers, in particular by (fine) loops, lapping, Polishing, blasting, etc., mechanically after, so are next to the surface texture also changed the chemical composition and reactivity of the surface. These changes are on the one hand large variations subjected, whereby no consistent quality realized can be. On the other hand, topographically affine surfaces have less favorable surfaces tribological properties and are prone to adhesions the opposite body. Furthermore, by grinding and polishing processes compressive stresses in the near-surface Induced areas, which are associated with the already existing high residual compressive stresses add the hard material layer.

In addition, the induced dislocations and the ruptured droplets lead to imperfections and microcracks, so the local fatigue strength The layer is reduced in tappets and the adhesive strength is reduced to the possible chipping during reworking of the layer.

waived However, for example, in the case of an arc process deposited layers on a subsequent polishing, lead the hard Droplets to abrasive wear of the against body or at least to a random polishing of the counter body, thereby Unforeseeable adverse consequences arise. Furthermore break the droplets while of the operation out of the layer, causing layer damage and leads to free, abrasive particles.

It is from the DE 102004043550 A1 In addition, a constellation is known in which the wear-resistant coating consists of at least one nanocrystalline functional layer of at least two CrN phases for a reduction of friction and for an increase of the wear resistance of the predetermined surface of the machine part. However, this coating does not meet all tribological requirements for friction reduction and wear resistance, especially in mixed friction region in an ideal manner.

Consequently The present invention is based on the object, a coating and a manufacturing method for such a coating create, which eliminate the above-mentioned disadvantages and in particular reduce the frictional torque in the entire application area and the service life increase the coated machine part and the counter body.

According to the invention This object is achieved by a wear-resistant coating with the features of claim 1 and by a method with the features of claim 21.

Thereby, that the functional layer is based on hydrogen-containing carbon is, and in cross-section areas of different consistency, their extension in at least one direction 20 nm, better yet 10nm, below, a nanostructured layer is formed, in the areas of different consistency, that is, for example made of different materials, different modifications, with different proportions of material or even with different crystal orientation can perform various tasks by a single substance of homogeneous nature very difficult to fulfill are. However, nanopatterning is the rubbing partner different in the functional layer at the same time For example, areas for reducing sliding friction and for Generation of the necessary material hardness opposite.

This is also the case when the functional layer at least partially through to the surface formed in substantially parallel layers, which are the areas form different consistency. In this case is through the small thickness of the layers (<20 nm or even <10nm) either from the beginning or after a short period of operation and beginning Abrasion a hybrid surface created in different places in different layers lie free. The surface The functional layer thus offers the friction partner different surface areas with different hardness, different friction properties, adhesion tendency and different Toughness. Such a nanostructuring is additionally due to the inhomogeneities high crack resistance against chipping and peeling off Layer formed. It can by suitable design and arrangement the layers also increased corrosion resistance or an elevated or reduced wettability with lubricants can be achieved. measurements have shown that by the invention, the reduction of friction by 30% as well as hardening between 15 and 70 GP can be achieved.

Advantageous are in such a constellation one or more of the layers thinner than 10 nm. The number of layers is typically greater than 2 and can be up to a few 10, especially over 50 or over 100 amount so that the total thickness of the layer up to 10 microns can amount.

neighboring Layers each have different consistency, insofar as, for example, at least two adjacent layers each have different of the following three consistencies: amorphous, metal-free, hydrogen-containing carbon, amorphous, metal containing hydrogen-containing carbon, more amorphous, at least a non-metal-containing, hydrogen-containing carbon. Basically you can do that contain process-corrected impurities of less than 1% be.

In addition, can be different be provided kind of layers. It has the non-metals containing Hydrogen-containing carbon, for example, typically the property frictional forces and, for example, fluorine, silicon or oxygen is stored, also the property of low wettability to favor with lubricants. This favors a thinner film of oil, which is especially true for fast relative movements of the friction partners, So for example in valve trains, brings benefits.

The metal-containing amorphous, hydrogen-containing hydrocarbons typically have the properties of hardness and abrasion resistance.

neighboring Layers can differ only in that they are different Materials are doped or that the extent of doping varies is.

By the doping will be the material properties, especially if it is a crystalline phase, significantly changed. Consequently can the doping targeted to produce certain mechanical Properties are used, with the properties generated thereby also depend on the type and size of the doping atoms. moreover is the nature of the resulting crystalline structure of the set the doping atoms in that dependent, as from a certain degree of doping crystalline transformations take place or mixed phases of various modifications arise. Thus, you can also neighboring layers, which differ only by the kind or the Extent of Differentiate doping, completely have different mechanical or tribological properties.

moreover can adjacent layers also by the percentage of hydrogen differ in the amorphous carbon. Also by the hydrogen content in carbon are the fundamental ones strongly influenced by tribological properties. Hydrogen shares below 20%, especially between 5% and 20%, make up the hydrogen-containing amorphous carbon tends to be harder and are advantageous for the practice of this invention.

Also, the percentage ratio of sp ³ and sp ² hybridized carbon can distinguish two adjacent layers from each other. This concerns the carbon present in diamond and graphite modification, which are known to have different mechanical properties. Accordingly, the thus different adjacent layers also have different tribological properties. It is particularly advantageous if the proportion of sp ³ -hybridized C atoms is greater than 50% of the C atoms.

It may also advantageously be provided that in at least one layer at least one of the parameters: hydrogen content, proportion of the sp ³ -hybridized C atoms, doping perpendicular to the surface of the coating has a gradient.

Important is primarily that in practical use at the actual Friction surface different Areas with different mechanical properties are available.

By the described types and constellations of layers and through their thickness and sequence seen from the friction surface, can be used for a variety of tribological requirements the qualities of the surface permanently be adjusted by the proportion of each exposed at the surface Areas with big ones Hardness, great tenacity or effective reduction of friction is predominant or less weighted is. Thus allows the invention by suitable stratification of the areas with different Consistency an individual adjustment to customer-specific requirements.

It can according to the invention also be provided that the areas at least partially by Nanoparticles are formed. These can for example consist of a or more of the materials: nitride, boride, carbide, silicide be. There are, for example, chromium nitride, titanium nitride, silicon nitride, Silicon carbide or titanium carbide conceivable.

such Nanoparticles can For example, in the context of a deposition process together with or before or after the deposition of appropriate hydrogen-containing Carbon layers are deposited with.

To be in the separator temporarily the corresponding necessary Substances are brought into the gas phase, either by sputtering or other known methods and by the process parameters is the Particle crystallization promoted. This creates nanodisperse, self-organized regions, either of different crystallites or also crystallites of the same structure with different Orientations.

For example can so-called nitride formers such as chromium, titanium and others, unstable Nitride-forming elements such as copper deposited together be, for example, when using copper and chromium nitride the copper content compared chromium content can be less than 2%. It then forms chromium nitride in a copper matrix as a nanocrystal. A similar result can be seen with Titanium nitride and a very low boron content can be achieved, instead of Titanium nitride can also be used titanium carbide and anyway the corresponding nitride or carbide in a quasi-amorphous boron matrix crystallized.

in the Result can the corresponding nanoparticles either in a hydrogen-containing carbon existing amorphous layer be embedded or between the carbon layers form a nanoparticle layer.

It is important that the layer formed is thin or the particles are finely distributed, so that on the surface of the functional layer in each case the exposed areas of the nanoparticles occupy only a part of the surface and thus other parts are occupied by areas of different consistency with other mechanical or tribological properties.

Also by the incorporation of nanoparticles is beyond the inherent mechanical properties also in total in the resulting functional layer Effectively inhibited crack propagation. This is at a size of the nanoparticles under 20 nm better even below 10 nm optimally guaranteed.

Advantageous has the coating below the functional layer at least a primer layer made of chromium, tungsten or titanium or Borides, carbides or nitrides of transition metals. One Such adhesion promoter stabilizes the overall structure of the coated machine part with the functional layer and prevented especially detachments the functional layer. As for the machine parts suitable materials come usual easily processable and cost-effective Materials (16Mn Cr5, C45, 100 Cr6, 31 Cr Mo V9, 80 Cr2 and so on) in question. As a friction partner in the sense of a lightweight construction to save weight also egg sen / carbon alloys conceivable.

Especially advantageous is additional the provision of a support layer below the functional layer of a metal-containing or non-metal-containing, Hydrogen-containing carbon layer containing one or more the components tungsten, tantalum, chromium, vanadium, hafnium, titanium or nickel on the one hand or silicon, oxygen, fluorine, nitrogen on the other contains.

A such support layer has the job, big mechanical forces acting on the functional layer so that no excessive deformation the functional layer occurs, which is used to detach from substrates or to destruction the functional layer could result from cracking and flaking. The Interlayer is extremely strong, with neither a small Friction resistance must still have wear resistance. Therefore, the support layer specifically designed so that they give a low compliance has or adjusted in the compliance Will that make an optimal transition between creates the functional layer and the actual machine part.

The The invention further relates to a process for the preparation a coating according to claim 1 or one of the following, wherein in a deposition method for Apply the areas on the surface to the process parameters successive times are changed so that the size of Deposition formed areas in the cross section of the coating 20 nm below. It is particularly advantageous if the size of the areas 10 nm below.

For this can at least one of the parameters pressure, temperature, admixture of dopants, hydrogen content, rotational speed carbon content while the production of the functional layer abruptly or continuously be changed.

At the Separation process as well as in any other steps of Be coating such as heating or plasma etching a process temperature of 250 ° C advantageously not exceeded, therewith the hardening the basic material of the machine part is preserved and a post-processing For example, must not be done by inductive hardening.

The Deposition takes place in the context of known PVD (physical vapor diposition) and (PA) CVD (Plasma Assisted Chemical Vapor Doposition) method.

at a PVD process is a starting material, such as graphite, heated so that a beam of high-energy carbon ions out imitated the graphite and in the direction of the surface to be coated in one Field is accelerated.

at A (PA) CVD method is used with the aid of a plasma Gas mixture introduced into the process chamber, in which the be located to be coated material parts. The (PA) CVD method is a further development of the CVD process and combines the Advantages of the CVO process (undirected process) and the PVD process (low temperatures). In the PACVD process, the layer deposition is carried out by chemical Reaction from the gas phase at temperatures of less than 200 ° C with a targeted plasma support.

By the change the process parameters such as pressure, temperature and hydrogen content as well as dopants or the Rotationsgeschwidigkeit of the coated Subject, the structure of the resulting coating is determined. there With certain parameter limits, there are also sudden changes in the consistency of the deposited layer, as certain in particular crystalline configurations only up to certain proportions of material individual substances can be formed. Are these shares not before, then becomes another crystal or another modification or a mixed phase formed.

Consequently can be adjusted by varying the process parameters at appropriate intervals small (smaller 10 nm) areas either particle or layered deposit.

The The invention ultimately also relates to machine parts that are associated with the coating of the invention are provided, especially on a valve lifter for a cam actuated Valve of an internal combustion engine.

The Invention will be with reference to an embodiment with reference on the said valve lifter in one Drawing shown and then described.

there demonstrate:

1 a front view of a friction pair consisting of bucket tappet and camshaft for the operation of a valve of an internal combustion engine;

2 a perspective view of the tappet 1 ;

3 a perspective view of a hydraulic support element, which is connected via a rolling bearing component with a finger lever in connection;

4 a schematic cross-sectional view of a machine part with wear-resistant coating according to an embodiment of the present invention and

5 Representation of a functional layer.

In the figures of the drawing, like reference numerals designate the same or functionally identical components, unless stated otherwise is.

1 illustrates a friction pair consisting of a bucket tappet 5 with a cam contact surface 50 and a cup shirt 51 as well as from a cam 6 , The tappet 5 is in 2 shown in more detail in a perspective view. The tappet 5 is generally for engine parts in internal combustion engines with the shaft 7 a valve connected by moving the cam surface against the cam contact surface 50 the tappet 5 the valve opens or closes.

In general, modern valvetrain components, such as cup and pump tappets, are subject to high demands in terms of wear resistance and resource conservation, in particular at the contact surface 50 ,

Combined with 4 which is a schematic cross-sectional view of a wear-resistant coating for a machine part 1 For example, for a tappet 5 , Illustrated according to a preferred embodiment of the present invention, an embodiment of the present invention will be explained in more detail below.

The tappet 5 is for a reduction of the friction coefficient and for an increase of the wear resistance in the area of the cam contact surface 50 or, if required, in the area of the cam contact surface 50 and the cup shirt 51 coated with a wear-resistant coating according to the invention. In case of high deformations of the cup shirt 51 the tappet 50 in the area of the open side, can optionally also a partial coating of the cup shirt 51 respectively.

The area to be coated 2 , ie in the present case, the cam contact surface 50 the tappet 5 , is preferably case hardened or carbonitrided and tempered prior to coating.

The main body, in the present case, the cam contact surface 50 the tappet 5 , which advantageously consists of a cost-effective steel material, such as 16MnCr5, C45, 100Cr6, 31 CrMoV9, 80Cr2 or derglei Chen, according to the present embodiment, first with an adhesive layer 3 coated. The adhesive layer 3 For example, each may consist of a metal-containing carbon, such as a compound of tungsten and carbon, but also of metallic materials (eg Cr, Ti), and borides, carbides, nitrides and silicides of the transition metals. An additional support layer above the primer layer may consist of a non-metal such as W, Ta, Cr, V, Hf, Ti, Ni or Si, O, F, N, and hydrogen containing amorphous carbon. The adhesion-promoting and the supporting layer can in connection with a heat treatment, for example case hardening, carbonitriding, nitrocarburizing, by a thermochemical process, for example nitriding, boriding, by a galvanic process, for example by applying a chromium-containing layer, or by means of a PVD process, for example Application of Me-C, carbides and nitrides of the transition metals, are formed.

The support layer is intended to increase the fatigue strength of the overall coating, ie to prevent plastic deformation, cracking, growth and fractures of the layer system. Such fatigue operations may be due to the loading of the cam and the material stress of the bucket tappet induced therefrom 5 and by different degrees of hardness, moduli of elasticity, Deformabilities of the individual layers or the base body and the wear-resistant coating arise. In this case, an education of the layer 3 as a support layer 3 either alone or in combination with a suitable primer layer.

As in 4 is shown, according to the present embodiment over the support and / or the adhesion-promoting layer 3 a wear-resistant coating 4 educated.

The functional layer 4 is there shown schematically constructed from many individual nanolayers, wherein the size ratios are shown only schematically and not to scale.

In the 5 On the other hand, the functional layer is scaled up to scale. In this case, the variants are shown in the left half of the figure, which have different superimposed less than 10 nm thick layers, each consisting of a hydrogen-containing amorphous carbon with different consistency, while on the right side of the figure a variant with additional nanodisperse particles is shown.

The scale is widely spaced because of the small thickness of the nanosheets in the direction perpendicular to the surface. The wavy line on the surface represents the real surface, which self-adjusts due to irregularities in manufacture or after use. The waviness is in reality not as great as shown but appears exaggerated by the uniaxial magnification of the scale perpendicular to the friction surface. Nevertheless, the effect achieved with the invention can be explained on the basis of this illustration. The individual layers 60 . 61 . 62 are hatched differently at least in the upper area to the surface and distinguishable thereby. It turns out that due to the somewhat (a few nm) irregular structure of the surface at the latest after a first start-up and wear at different places the lower layers 61 . 62 and even layers further down, not individually marked, come to light. These layers each have different tribological properties, so that the entire surface of the friction partner is a mixture of many different areas with different properties in terms of hardness, elasticity, wear resistance and friction coefficient. This state is maintained even if the wear continues to progress, but this is greatly delayed by the said structure and the resulting wear resistance.

The individual layers differ at least partially in relation on the consistency, that is the amount of hydrogen, the type and amount of added, doped Substances or crystal modifications and orientations. At the same time, some or many of the layers are open the surface.

On the right side of the 5 shows the variant in which nanoparticles 63 . 64 are introduced into the carbon matrix. The corresponding nanoparticles, which may be formed for example as borides, carbides or nitrides, form where they come to the surface, so for example in the case of the particles 63 . 64 Hard and wear-resistant areas and thus also prevent the removal of the surrounding material of the carbon matrix. This, in turn, contributes somewhat to a reduction in the coefficient of friction, depending on the composition on the surface, for example.

Becomes in the course of the material wear from the surface The functional layer is slightly worn away, so are new nanoparticles uncovered, which then again the task mentioned, the hardness and wear resistance ensure you exercise.

Basically, the Nanoparticles can also be concentrated in different layers. This can, for example, in the context of the deposition process offer between the deposition of the remaining layers during the PVD or PACVD method certain metal nitrides, borides or carbides are introduced, in mixed proportions which are automatically separated to form different phases to lead. this leads to then to the formation of hard nanoparticles in the layer concerned.

The described invention provides a novel coating, the by selecting the particles and the individual nanolayers one Adaptation to the present tribological requirements in a very allowed by the mixture of areas with different consistencies on the surface Parameters in the macro area can be adjusted which can not be achieved with any known homogeneous material. The Invention also provides a simple manufacturing method for such a functional layer ready to face that the previously used production equipment for PVD and (PA) CVD coating no constructive changes requires.

The maximum coating temperature is preferably 250 ° C, so in a coating process, the base material is not tempered becomes.

The coating is preferably in a thickness of about 0.5 μm to about 10.0 μm preferably 2.0 microns, formed. As a result, the dimensions and surface roughness of the base body change to such a small extent that no reworking is necessary.

In the following, a further advantageous use of the coating according to the invention is explained in more detail. 3 illustrates a perspective view of a hydraulic support element 8th which is a piston 9 and a housing 10 having. The hydraulic support element 8th is with a drag lever 11 coupled, the drag lever 11 via a rolling bearing 12 is pivotally mounted. As in 3 also can be seen, the piston 9 a contact area 90 between the piston 9 and the rocker arm 11 on. Furthermore, the piston has 9 a contact area 91 between the piston 9 and the housing 10 on. For a reduction of wear in the contact area 90 between the piston 9 and the rocker arm 11 becomes the contact area 90 likewise with a nanostructured functional layer according to the invention 4 Mistake.

Furthermore, also the contact area 91 between the piston 9 and the housing 10 with such a coating 3 . 4 Depending on the application and manufacturing technology are coated. As a result, the overall service life of the illustrated tribological system is increased, whereby a failure of the individual machine parts can be reduced during operation and thus overall costs can be saved.

In addition, components of the rolling bearing 12 , For example, the rolling elements, the inner and outer rings of the bearing 12 , the rolling bearing cages, the axial discs or the like also to increase the wear resistance and to reduce friction with the functional layer according to the invention 4 with the interposition of, for example, a support and / or adhesion-promoting layer 3 be coated.

The Of course, the layer system described above is also for others Construction and functional units, such as valve stems or valve stem supports, Abstütz- and male members, rolling bearing components, release bearing, Piston pin, bearing bushes, control piston for example for injectors in the engine area, linear guides and other mechanically and tribologically highly stressed parts suitable.

It should be noted at this point that the functional layer 4 can also be deposited directly on the body of the machine part to be coated without a support layer 3 or adhesion layer 3 is applied in between.

Even though the present invention with reference to preferred embodiments As described above, it is not limited thereto on diverse Modifiable way.

1

machinery

2

predetermined area of the machine part

3

Backing / adhesive layer

4

nanocrystalline functional layer

5

tappets

6

cam

7

valve stem

8th

hydraulic supporting

9

piston

10

casing

11

cam follower

12

roller bearing

50

Cam contact surface

51

cup shirt

60,61,62

layers

63.64

nanoparticles

90

contact area between piston and drag lever

91

contact area between piston and housing

Claims (24)

Wear-resistant coating for a machine part which is exposed to frictional wear, with a functional layer based on amorphous carbon and hydrogen, characterized in that the functional layer has cross-sectional areas ( 60 . 61 . 62 . 63 . 64 ) of different consistency, the extent of which in at least one direction is less than 20 nm. Coating according to claim 1, characterized in that the regions ( 60 . 61 . 62 . 63 . 64 ) are formed at least partially by layers substantially parallel to the surface. Coating according to claim 2, characterized in that at least at least one of the layers ( 60 . 61 . 62 ) is thinner than 10 nm. Coating according to claim 2 or 3, characterized in that adjacent layers ( 60 . 61 . 62 ) each have different consistencies. Coating according to claim 4, characterized in that at least two adjacent layers ( 60 . 61 . 62 ) have different of the following three consistencies: amorphous metal-free carbon with hydrogen, amorphous metal-containing carbon with hydrogen, amorphous one Non-metal-containing carbon with hydrogen. Coating according to claim 4 or 5, characterized in that adjacent layers ( 60 . 61 . 62 ) differ by the nature and / or extent of doping. Coating according to claim 4, 5 or 6, characterized in that adjacent layers ( 60 . 61 . 62 ) differ by the percentage of hydrogen. Coating according to Claim 4 or one of the following, characterized in that adjacent layers differ by the ratio of sp ³ - and sp ² -hybridized carbon. Coating according to claim 2 or one of the following, characterized in that in at least one layer ( 60 . 61 . 62 ) at least one of the parameters: hydrogen content, proportion of sp ³ -hybridized carbon atoms, doping, has a gradient perpendicular to the surface of the coating. Coating according to Claim 2 or one of the following, characterized in that an uppermost layer of a hydrogen-containing Carbon layer doping with fluorine, oxygen and / or Has silicon. Coating according to Claim 1 or one of the following, characterized in that the regions ( 63 . 64 ) are at least partially formed by nanoparticles. Coating according to claim 11, characterized in that the nanoparticles ( 63 . 64 ) are formed from one or more of the materials: nitride, boride, carbide, silicide. Coating according to claim 11 or 12, characterized in that nanoparticles ( 63 . 64 ) of the same composition are provided with different crystal orientation. Coating according to claim 11, 12 or 13, characterized in that the nanoparticles ( 63 . 64 ) are embedded in a hydrogen-containing carbon layer. Coating according to claim 13, characterized in that a layer of nanocrystalline material is formed. Coating according to Claim 1 or one of the following, characterized in that below the functional layer ( 4 ) at least one adhesive layer ( 3 ) consisting essentially of chromium, tungsten or titanium or of borides, carbides, nitrides or silicides of the transition metals is provided. Coating according to Claim 1 or one of the following, characterized in that below the functional layer ( 4 ) a supporting layer ( 3 ) is provided from a hydrogen-containing, metal-containing or non-metal-containing carbon layer containing one or more of the components tungsten, tantalum, chromium, vanadium, haffnium, titanium, nickel on the one hand or silicon, oxygen, fluorine, nitrogen on the other. Coating according to Claim 1 or one of the following, characterized in that the thickness of the functional layer between 0.5 and 10 microns. Coating according to Claim 1 or one of the following, characterized in that the carbon layer is less than Contains 20 atomic percent hydrogen. Process for producing a coating according to the claims 1 to 19, characterized in that in a deposition method for Applying the functional layer to the surface in certain temporal intervals in each case at least one process parameter is changed in such a way that the size of the Deposition formed different areas in cross section the coating falls below 20 nm. Process according to claim 20, characterized in that the process parameters controlled so that will be the size of the different ones Areas 10 nm in the cross section of the coating falls below. Method according to claim 20 or 21, characterized that at least one of the parameters pressure, temperature, admixture of dopants, hydrogen content rotational speed while the production of the functional layer is repeatedly changed abruptly. A method according to claim 20 or one of the following characterized in that the preparation of the coating at Temperatures below 250 ° C carried out becomes. Valve tappets for a through a cam actuated Valve of an internal combustion engine with a coating according to a the claims 1 to 19.