DE19822932C2 - Process for applying a layer of lubricant to an exposed and tribologically stressed surface of a connecting rod, as well as connecting rods - Google Patents

Description

The invention relates to a method for applying a Lubricant layer on an exposed and tribologically be stressed surface of a connecting rod and a connecting rod according to the O Subject of claims 1 or 2 or 25, such as both. from the generic DE 32 00 549 as be knows emerges.

From DE 32 00 549 A1 a connecting rod is known that SiC Powder is pressed. On the tribologically stressed surface Chen of the Pleuls are used with a lubricant layer made from motor oil.

From the article "Formation and self-lubricating mechanisms of boric acid on borided steel surfaces" by A. Erdemir et al in Surface & Coating Technology 76-77 , 1995 , page 443-490, a coating of a dry lubricant made of boric acid on steels is known and a method of applying the coating. In the method previously known from this document, a steel is first borated. The borated surface of the steel has good hardness and corrosion resistance. However, their coefficient of friction (coefficient of friction) is very high. Therefore, the borated surface of the steel is provided with a layer of lubricant made of boric acid, which acts as a dry lubricant. For boronizing, the steel is immersed in a salt bath which contains a boron compound and which is heated to 940 ° C. After the salt bath, the borated steel is heated to 750 ° C, which allows the boron atoms to diffuse deeper into the surface area of the steel. It is believed that some of the atoms also diffuse to the free surface, where they react immediately to boron oxide in the presence of oxygen. As a result, a boron oxide layer is deposited on the surface of the steel, which is subsequently converted to boric acid when it cools down and in the presence of hydrogen. To form the boron oxide, however, the temperature must not be reduced below 750 ° C and the borated steel must not be heated to this temperature for longer than 8 minutes, as otherwise no boron oxide will form. In addition to the fact that this temperature treatment is an immense burden on the steel, the process for producing the boron oxide layer is also very sensitive, which is why the previously known method is also very complex, complicated and expensive. Furthermore, with this method, end-to-end, especially precisely dimensioned components are very difficult to manufacture and with a large reject rate. The entire process is also very inflexible, especially for changed layer thicknesses.

From the article "A study of the formation and self-lubrication mechanisms of boric acid folms on boric oxide caotings" by A. Erdemir et al in Surface & Coating Technology 43/44, 1990, Be te 588-596 is also a coating of Dry lubricant made of boric acid and a method for applying this coating are known. In this process, the surfaces of an object made of α-aluminum oxide and an object made of steel (M50) were cleaned by an argon ion beam and then coated with the boron oxide by means of an electron beam evaporation in vacuo. The friction coefficients of the several µm thick lubricant layers were very good in both cases, although the service life of the coating on steel was short. In addition, the adhesion of the lubricant layers made of boric acid to the substrates is low, so that this method also has a high rejection rate.

From the article Article "Tribilogical Properties of Boric-Acid-Forming Sufaces. Part II: Mechanisms of Formation and Self-Lubrication of Boric Acid Films on Boron- and Boric Oxide-Containing Surfaces." from A. Erdemir et al in Journal of the Siciety of Tribologists and Lubrication Engineers ( 1991 ), 47 ( 3 ), pages 179-184 a further coating of an object with boric acid as a dry lubricant as well as an associated method are known. Here, the surface to be coated first has a boron layer, then a boron oxide layer and then the lubricant layer.

The object of the invention is to provide a method with which a particularly metallic connecting rod in an inexpensive manner and within small manufacturing tolerances as well as small ones Reject rates with a good adhesive layer of lubricant a dry lubricant can be provided, the Tro lubricant with the lowest possible coefficient of friction and one should have as long a service life as possible. Furthermore, it is Object of the invention for a particularly metallic connecting rod a well-adhering layer of lubricant from a dry lubricant means to develop which lubricant layer inexpensive and within small manufacturing tolerances as well as small ones Reject rates is applied, the dry lubricant the lowest possible coefficient of friction and the highest possible Has service life.

The object is achieved with a method with the Method steps of claim 1 or 2 or with a connecting rod solved with the features of claim 25. By inventing appropriate layer structure and the application of the individual Layers, preferably by means of a plasma CVD method, can the layer thicknesses can be easily reproduced in the µm range can be applied so that at least one complex Post-processing is not necessary. Furthermore, the liability on the Pleul improved by the procedure according to the invention.  

Useful embodiments of the invention are the respective Un removable claims. Otherwise, the invention is based on of examples and subsequent drawings explained in more detail.

It shows

Fig. 1 shows a detail of a section of a resistance through OF INVENTION to the invention layer structure of a coated Gegens,

Fig. 2 is a diagram of the friction coefficient in function of time for coated with different solid lubricants connecting rod at a resonant wear test and

Fig. 3 shows a device for producing the coating according to the invention

Fig. 4 is a gas flow diagram in the manufacture of an inventive coating.

In Fig. 1 is a section of a section through an inventive layer structure of a coated connecting rod 1 is provided, the scale is strongly distorted. The metallic connecting rod 1 made of steel has a borated adhesive layer 3 with borides of the material of the connecting rod 1 in the area of its outward-facing surface 2 covered with the coating. In the present case, 3 borides of iron are arranged within the adhesion promoter layer. Beginning inside there is at least more Fe ₂ B and then FeB.

Instead of a pure boration the near-surface regions of the connecting rod 1 can also nitrided and / or carbonized, and / or be trated carbonized for producing the primer layer. 3 Such adhesion promoter layers 3 can also be borated in addition. Instead of a connecting rod 1 made of steel, a connecting rod made of another material, but preferably of a Ti and / or Al and / or Mg material, can be provided with the coating according to the invention.

On the previously exposed surface 2 of the connecting rod 1 , the adhesive layer 3 is followed by an intermediate layer 4 , which has boron and its oxides. In particular, the intermediate layer 4 - starting from the previously exposed surface 2 of the connecting rod 1 - first at least predominantly boron, then at least predominantly B ₆ O and finally B ₂ O ₃ . The boric acid (H ₃ BO ₃ ) containing lubricant layer 5 is arranged on the B ₂ O ₃ , the proportion of boric acid in the lubricant layer 5 being at least 5%, preferably 10% and particularly preferably 30%, at least near the surface.

The boric acid used as a dry lubricant can, in particular, only or additionally, in particular in the event of wear of the previous lubricant layer 5 , be formed in the application by a near-surface conversion of B ₂ O ₃ in the presence of water or hydrogen. Advantageously, the boron and oxygen, in particular B ₂ O ₃ , intermediate layer 4 in the event of wear and tear can form a kind of reservoir for the boric acid of the lubricant layer 5 .

In Fig. 2 a diagram of the coefficient of friction is in Depending ness of time shown in coated with different solid lubricants substrates which were equal Schwingver a test subject.

The individual curves relate to substrates made of the following materials:
Curve A: a connecting rod 1 with a layer structure according to the invention with a lubricant layer made of boric acid,
Curve B: a molybdenum sulfide layer (MoS ₂ ) on an object made of a hard metal,
Curve C: amorphous diamond on an object made of a hard metal and
Curve D: a tungsten carbide / graphite layer on an object made of a high-performance high-speed steel.

The tests were carried out in a dry state, i.e. H. without additional che, especially liquid lubrication performed. As a test body was a ball made of 100Cr6 with a radius of 4 mm used with a load of 5 N on the coated  Pressed substrate and with a length of 600 microns Frequency of 10 kHz was moved back and forth.

The object coated with the WC / C layer (curve D) has a course of the coefficient of friction, which follows an initial run-in behavior at values between 0.2 and 0.3 sets. This value is within the band mentioned held just over 100 minutes wide and then rises on. At about 4000 minutes it is about 0.45.

The object coated with the amorphous diamond (curve C) has a course of the coefficient of friction which, after an initial running-in behavior of approximately ten minutes, in which the values of the coefficient of friction increase and decrease between approximately 0.1 and 0.35, to a value of approximately 0.1 sets. From this point in time, the value of the coefficient of friction increases steadily with increasing exposure time. As can be seen from the diagram in FIG. 2, the value of the coefficient of friction increases from about 0.1 to about 0.2 within 10 minutes after about 10 minutes.

The object coated with MoS ₂ (curve B) has a course of the coefficient of friction which, after a very short running-in behavior, adjusts to a value between approximately 0.05 and approximately 0.1. This value of the coefficient of friction is kept within the upper range for about 100 minutes and then rises to values over 0.4 within a very short time. This means that the material has very good short-term behavior but very poor long-term behavior.

The connecting rod 1 (curve A) having the layer structure according to the invention has, after an initial running behavior of approximately one minute, a course of the coefficient of friction which adjusts to a value of approximately 0.05. This value of the coefficient of friction is kept unchanged over the entire time. In particular, it should be mentioned here that the value of the coefficient of friction remained stable even after a test period which was longer than the time shown in the diagram of 10,000 min.

In Fig. 3, a device in the manner of a plasma CVD system is shown, which is suitable for carrying out the inventive method with which the layer structure according to the invention can be realized.

The device has a reactor 6 which can be evacuated by a pump system 7 connected to it in a fluidic manner. Furthermore, the reactor 6 has a gas supply system with several gas bottles 8-11 and an evaporator 12 . The gas supply system, like the pump system 7, can be switched on and off. The gas bottles 8-11 and the evaporator 12 can be a single and connected to the interior 13 of the reactor 6 with a controllable gas flow. In the gas bottles 8-11 , for example, the process gases, a gas supporting a plasma 16 and / or also starting materials for the layer according to the invention are stored. In particular, u, the gases methane, diborane, hydrogen, oxygen and nitrogen.

A substrate holder 14 is arranged inside the reactor 6 , on which a connecting rod 1 to be coated can be arranged. The substrate holder 14 is electrically conductively connected to a generator 15 for the voltage supply. The generator 15 provided for plasma generation can be operated, for example, with alternating electrical voltage, with an alternating voltage with a cut half-wave or the like, preferably with a pulsed direct voltage.

To produce a layer structure according to the invention, the connecting rod 1 to be coated is installed in the reactor 6 and the reactor interior 13 is evacuated to a pressure of less than 100 mbar, preferably less than 10 mbar and particularly preferably to about 1 mbar. After evacuation, the vacuum reached is kept inside the reactor 13 . Optionally, the interior of the reactor 13 can also be at least partially refilled with an inert gas.

Subsequently, a desired pulse voltage with respect to its amplitude and frequency is set on the generator 15 and applied to the connecting rod 1 connected to the electrically conductive ver 15 with the generator. A voltage is preferably selected which is negative with respect to the gas space surrounding the connecting rod 1 and in particular also to ground.

Thereafter, the process gas for producing the adhesion promoter layer 3 , which serves to improve the adhesion between the later applied lubricant layer 5 and the material of the connecting rod 1 or to improve the adhesion between a subsequently applied intermediate layer 4 and the material of the connecting rod 1 , is introduced.

The adhesion promoter layer 3 is advantageously produced by boronizing and / or nitriding and / or carbonizing and / or carbonitriding, which processes are expediently supported by a plasma 16 . Excess gas particles are removed from the pump system 7 .

Instead of or in addition to the above process for the manufacture of the adhesion promoter layer 3 , the substance or substances in question can also be introduced into the areas of the surface 2 of the connecting rod 1 to be coated near the surface by means of ion implantation.

As a replacement measure or as a supplementary measure to the above-mentioned adhesion promoter layers 3 , the surface 2 of the connecting rod 1 to be coated can be used as an adhesion promoter layer 3 or as part of the adhesion promoter layer 3, in particular TiN and / or TiC and / or Ti (C , N) and / or a boron carbide layer (B ₄ C) are deposited.

The supporting plasma 16 is generated from the interaction of the pulsed electrical voltage and hydrogen, which is introduced ex tra into the interior of the reactor 13 , and / or the process gas. The plasma 16 is preferably generated in such a way that it envelops the surface 2 of the connecting rod 1 to be coated and, if appropriate, also at least partially immerses it in depressions, such as bores and the like, of the connecting rod 1 . The plasma 16 is preferably generated in the region of the surface of the connecting rod 1 .

In a favorable manner, the plasma 16 heats at least the surface 2 of the connecting rod 1 to be coated to temperatures of less than 750 ° C., preferably less than 700 ° C. and particularly preferably less than 600 ° C., since here at most a slight change in the structure of the connecting rod material 1 is to be expected.

The pulse rate of the electrical voltage has an effect on the spatial shape of the plasma 16 , among other things. Therefore, the pulse rate and possibly also the selected electrical voltage are expediently set depending on the physical configuration of the surface 2 of the connecting rod 1 to be coated.

The process gases are more appropriately gases which contain the element or elements which are required for the production of the adhesion promoter layer 3 . This can be done, for example, by the fact that the process gas has the element (s) in question in pure form and / or that the element (s) concerned is at process conditions from the process gas as a dissociation product and / or as Ion be made available.

In the above cases, process gases are used as process gas, the boron and / or nitrogen and / or carbon at least as Have connection and / or the ent under process conditions Release speaking element.

In the case of a boronization, the process gas is preferably borane (B _n H _m ), preferably diborane (B ₂ H ₆ ), boron chloride (BCl ₃ ) or boron fluoride (BF ₃ ) or a mixture of at least two these gases.

In the case of a connecting rod 1 having Fe, in particular Fe ₂ B is formed during boriding and that is brittle compared to FeB ₂ and therefore mostly undesirable FeB. Particularly good adhesion of the subsequent layer is achieved if the FeB is formed in a proportion of less than 20%, preferably less than 10% and particularly preferably less than 1% in relation to all iron borides.

In order to achieve this in a simple manner, the proportion of boron in the separating gas phase after the formation of Fe ₂ B in the region of the surface 2 of the connecting rod 1 to be coated can in particular be increased by at least 20% within 5 s and / or the surface temperature of the Connecting rods 1 are lowered.

On the adhesion promoter layer 3 , an intermediate layer 4 is usefully arranged. For this purpose, a gas is introduced as the second primary material into the reactor interior 13 and into the plasma 16 , which has boron at least as a compound and releases the boron under process conditions.

As with the adhesion promoter layer 3 , special boranes (B _n H _m ), preferably diborane (B ₂ H ₆ ), boron chloride (BCl ₃ ) or boron fluoride (BF ₃ ) or a mixture of at least two of these gases are used for this purpose.

Furthermore, to form the intermediate layer 4, an oxygen material is introduced at least as a compound and, under process conditions, the oxygen-releasing first primary material is introduced into the separating gas phase.

The intermediate layer 4 containing boron and oxygen is deposited on the adhesion promoter layer 3 from these two materials.

By varying the temperature and / or the oxygen, the proportion of oxygen in the intermediate layer 4 can be controlled so that the proportion of oxygen within the intermediate layer 4 has a gradient.

The proportion of oxygen preferably increases with increasing distance from the adhesion promoter layer 3 . The intermediate layer 5 is preferably applied with boron oxide, in particular as B ₆ O and / or B ₂ O ₃ , B ₆ O and then B ₂ O ₃ preferably being applied first. Before the boron oxides are applied, at least largely pure boron is expediently applied to the adhesion promoter layer 3 .

Analogous to the production of the adhesion promoter layer 3 , the connecting rod 1 is heated during the deposition of the intermediate layer 4 containing boron and oxygen, in particular to temperatures below 750 ° C., preferably below 700 ° C. and particularly preferably below 600 ° C.

In the area of the exposed surface 2 of the intermediate layer 4 , the lubricant layer 5 made of boric acid (H ₃ BO ₃ ) is finally arranged. This lubricant layer 5 can be produced with the gases What serstoff, oxygen and boron right inside the reactor 6 .

Convert It is also possible within the reactor 6, the oberflä-near areas of the boron and oxygen-containing interim rule layer 4 by reaction with hydrogen in the boric acid transform or the boron and oxygen-containing intermediate layer 4 are identical in their preparation from the gas phase at least partially in boric acid convert. In both cases, the temperature of the connecting rod 1 is expediently reduced, at least close to the surface.

Alternatively, it is also possible for this lubricant layer 5 to be formed only when hydrogen and / or water vapor are present when the connecting rod 1 is used. In this case, a chemical reaction of the near-surface regions of the intermediate layer 4 containing boron and oxygen with the hydrogen in the atmosphere converts the layer 5 to the lubricant containing boric acid. This reaction is particularly promoted by the heat generated during use. In this case, at least certain areas of the intermediate layer containing boron and oxygen represent a reservoir for the recovery of worn or otherwise removed boric acid.

In all cases, the lubricant layer 5 expediently has at least 80%, preferably at least 90% and particularly preferably at least 95% boric acid.

Advantageously, not only during the production of the adhesion promoter layer 3 but also during the production of the intermediate layer 4 containing boron and oxygen and / or the lubricant layer 5 within the reactor 6 , a pulsed DC voltage is applied to the connecting rod 1 , which voltage compared to that of the connecting rod 1 surrounding gas space has a negative electrical potential.

With a coating applied according to claim 1 can especially abrasive treads in mechanical engineering share, preferably engine components and particularly preferably Noc core shafts, rocker arms, tappets, liners, valve bridges, Valve stems, valve bushings or guides, piston pins, Piston rings, cylinder surfaces, connecting rods, thrust washers, fer ner gears, especially gears, chain links or Belt pulleys for continuously variable transmissions, furthermore cutting engaging cutting surfaces of cutting tools with defin cutting edge geometries such as milling cutters, turning tools, reversible cutting edges plates, drills, and also tools for reaming and broaching as well abrasively stressed forming tools, especially forming tools ge such as deep drawing presses and the like in an advantageous manner at least in some areas with a sensible and well-adhering tri biological coatings.  

In all applications it is particularly advantageous that an otherwise necessary lubrication with liquid lubricants at least ver can be reduced.

The method according to the invention is described below using a gas flow diagram shown in FIG. 4.

In Fig. 4, a gas flow diagram of various gases is shown over time, with the temperature of the sample to be coated is also applied. The diagram according to FIG. 4 describes the gas flow set in the reactor interior 13 during the production of a layer structure according to the invention on a metallic sample by means of a plasma CVD process.

In the plasma CVD process, the sample is heated by a plasma 16 surrounding the sample. The surface to be coated surface 2 of the sample heating plasma 16 , which also activates the primary materials and the process gas for deposition or for boring, is ignited or maintained by a voltage applied to the sample.

To regulate the temperature, the temperature of the sample is measured and, accordingly, the electrical voltage applied to the sample is changed for the plasma 16, which has a heating effect, for example. As in the present case, the electrical voltage can be a pure DC voltage. Depending on the requirements of the plasma 16 , a pulsed voltage, an AC voltage or a half-wave AC voltage is preferably applied instead of the DC voltage.

The course of the pressure p in the interior of the reactor is in the diagram according to FIG. 4 as an unmarked curve, the H ₂ flow (5% B ₂ H. Mixed with the process gas in the manufacture of the adhesion promoter and the intermediate layer and also the lubricant layer ₆ and 95% H ₂ ) as curve E and the oxygen flow from curve G. The values of the different gas flows refer to the standard cubic centimeter (sccm) unit. Since the boron-producing process gas is also used for the boron-supplying primary material, the curve F after the boronization (time interval H) also shows the gas flow of the second primary material (time interval I). During the time interval J, the lubricant layer 5 is applied.

The sample may be pre-cleaned before installation in the reactor 6 and then installed in the reactor 6 . The reactor interior 13 is then evacuated to a pressure of less than 0.5 mbar. For cleaning, an H _{2 is} introduced into the evacuated interior 13 of the reactor 6 for about 30 minutes. The plasma 16 is ignited in the area of the sample with the H ₂ gas and the surface 2 of the sample to be coated is cleaned with the aid of the H ₂ plasma 16 . As can be seen from the diagram in FIG. 4, when the sample is cleaned, the pressure inside the reactor 13 rises to a value of approximately 10 mbar. This value is at least largely maintained in the described production of the layer structure according to the invention of this exemplary embodiment.

After the surface 2 of the sample has been cleaned, it is put on for a period of H of about 6 hours at a temperature of about 750 ° C. and a B ₂ H ₆ gas stream of about 60 sccm mixed with 95% H ₂ . Under these process conditions, the adhesive layer 3 is produced. The sample is borated close to the surface for a few µm under the conditions just mentioned. By borated adhesive layer 3, the adhesion between the subsequently to be applied intermediate layer 4 and the lubricant layer 5 to be applied later and the material of the sample is improved (the object 1).

After boriding, the temperature is reduced to approximately 500 ° C. and the flow of the H ₂ -constituted process gas is reduced to a flow of approximately 50 sccm. As a result, a boron layer is produced on the adhesion promoter layer 3 for the period I of approximately 5 hours. This boron layer belongs to the intermediate layer 4 .

After the boron layer has grown, oxygen is additionally flowed into the reactor 6 for about 1 hour (time period J) with a flow of about 15 sccm, the previous process parameters (gas flows, temperature and pressure) being maintained. The boron and oxygen-containing regions of the intermediate layer 4 are thereby formed .

The temperature is then lowered and the remaining parameters are kept constant. By lowering the temperature, the plasma 16 collapses and the hydrogen previously used as the plasma fuel is freely available. This forms at temperatures below approx. 200 ° C and the presence of hydrogen the largely exclusively the dry lubricant boric acid (H ₃ BO ₃ ) containing lubricant layer 5 .

Claims (29)

1. A method for the outside and adhesive application of a lubricant layer to an exposed and tribologically stressed surface of a connecting rod, the lubricant layer having boric acid (H ₃ BO ₃ ) at least under stress conditions,
in which method that is installed to be coated and provided with an adhesive layer connecting rod (1) into a reactor, being improved by the adhesive layer (3) the adhesion between the later-applied dry lubricant of the lubricant layer (5) and the material of the connecting rod (1) ,
in which process the reactor ( 6 ) is evacuated to a pressure of less than 100 mbar, preferably less than 10 mbar and particularly preferably to about 1 mbar and / or at least partially filled with an inert gas,
in which method an intermediate layer is produced on the adhesion promoter layer from pre-materials that contain boron and oxygen,
in which method the intermediate layer ( 4 ) deposited above the adhesion promoter layer ( 3 ) is deposited with an oxygen gradient which increases with increasing distance from the adhesion promoter layer ( 3 ),
Which process is used to add a boron, at least as a compound, to the separating gas phase and to release the boron under process conditions,
in which method of the separating gas phase an oxygen material is added at least as a compound and under process conditions the oxygen-releasing first primary material is added, and
In which method, at least in part, boron and oxygen convert the intermediate layer ( 4 ) containing boron and oxygen at least in the area of its freely accessible surface with the aid of hydrogen to boric acid and is used as the dry lubricant of the lubricant layer ( 5 ). 2. Method for the outside and adhesive application of a lubricant layer to an exposed and tribologically stressed surface of a connecting rod, the lubricant layer having boric acid (H ₃ BO ₃ ) at least under stress conditions,
the process by which the connecting rod ( 1 ) to be coated is installed in a reactor,
in which process the reactor ( 6 ) is evacuated to a pressure of less than 100 mbar, preferably less than 10 mbar and particularly preferably to about 1 mbar and / or at least partially filled with an inert gas,
Which method produces an adhesion promoter layer ( 3 ), for which purpose at least one element of a process gas in the material of the exposed surface ( 2 ) of the connecting rod ( 1 ) in the region of the exposed surface ( 2 ) of the connecting rod ( 1 ), in particular by diffusion. introduced and installed there and / or chemically reacted, the adhesion between the later applied dry lubricant of the lubricant layer ( 5 ) and the material of the connecting rod ( 1 ) being improved by the adhesive layer ( 3 ),
the process in which a boron and / or nitrogen and / or carbon is added to the reactor, at least as a compound, and process gas which releases the corresponding element under process conditions,
in which method with intermediate materials containing boron and an intermediate layer ( 4 ) is produced on the adhesion promoter layer ( 3 ),
in which method the intermediate layer ( 4 ) deposited above the adhesion promoter layer ( 3 ) is deposited with an oxygen gradient which increases with increasing distance from the adhesion promoter layer ( 3 ),
In which method, at least in part, boron and oxygen convert the intermediate layer ( 4 ) containing boron and oxygen at least in the area of its freely accessible surface with the aid of hydrogen to boric acid and is used as the dry lubricant of the lubricant layer ( 5 ),
in which method a boron, at least as a compound and which releases the boron under process conditions, is added to the separating gas phase, and
in which process of the separating gas phase an oxygen material is added, at least as a compound and under process conditions, the oxygen-releasing first primary material is added. 3. The method according to claim 2, characterized in that for the production of the adhesive layer ( 3 ) at least one element of the process gas in the material of the exposed and to be coated surface ( 2 ) of the connecting rod ( 1 ) is diffused and / or ion-implanted. 4. The method according to claim 2, characterized in that the surface of the connecting rod ( 1 ) to form the adhesive layer ( 3 ) is borated and / or nitrided and / or carbonized and / or carbonitrided. 5. The method according to claim 1 or 2, characterized, that to form the boric acid layer hydrogen and / or a under process conditions hydrogen releasing hydrogen ver bond from the separating gas phase is used. 6. The method according to claim 1 or 2, characterized in that the process gases and / or the materials before they meet on the surface to be coated ( 2 ) of the connecting rod ( 1 ) passed through a plasma ( 16 ) and at least partially dissociated and / or be ionized. 7. The method according to claim 6, characterized in that the plasma ( 16 ) in the region of the surface to be coated ( 2 ) of the connecting rod ( 1 ) is generated and that at least the surface of the connecting rod ( 1 ) to be coated is heated with the plasma . 8. The method according to claim 1 or 2, characterized in that the connecting rod ( 1 ) is heated during the deposition of the boron / oxygen layer in particular to temperatures below 750 ° C, preferably below 700 ° C and particularly preferably below 600 ° C. 9. The method according to claim 2, characterized in that the connecting rod ( 1 ) during the formation of the adhesion promoter layer ( 3 ) by introducing boron atoms and / or carbon atoms and / or nitrogen atoms, in particular at temperatures below 750 ° C, preferably less than 700 ° C and particularly preferably less than 600 ° C is heated. 10. The method according to claim 5, characterized in that during the at least near-surface and at least partial conversion of the boron and oxygen-containing intermediate layer ( 4 ) in boric acid to produce the lubricant layer ( 5 ) the temperature is lowered. 11. The method according to claim 1 or 2, characterized in that for the introduction of boron and / or for the deposition of the boron and oxygen-containing intermediate layer ( 4 ) borane (B _n H _m ), preferably diborane (B ₂ H ₆ ), boron chloride ( BCl ₃ ) or boron fluoride (BF ₃ ) or a mixture of at least two of these gases is introduced into the reactor ( 6 ). 12. The method according to claim 1 or 2, characterized in that an electrical voltage is applied to the connecting rod ( 1 ) during the production of the intermediate layer ( 4 ) containing boron and oxygen and / or the lubricant layer ( 5 ). 13. The method according to claim 2, characterized in that an electrical voltage is applied to the connecting rod ( 1 ) during the production of the adhesive layer ( 3 ). 14. The method according to claim 12 or 13, characterized, that a pulsed DC voltage ge as electrical voltage is chosen. 15. The method according to claim 1 or 2, characterized in that as boron and oxygen-containing intermediate layer ( 4 ) Bo roxid, in particular B ₂ O _{3 is} deposited. 16. The method according to claim 5, characterized in that the lubricant layer ( 5 ) is formed with at least 30%, preferably at least 50% and particularly preferably at least 60% boric acid. 17. The method according to claim 5, characterized in that the lubricant layer ( 5 ) is formed with at least 80%, preferably at least 90% and particularly preferably at least 95% boric acid. 18. The method according to claim 1 or 2, characterized in that for the intermediate layer ( 4 ) B ₆ O and / or B ₂ O _{3 is} deposited. 19. The method according to claim 1 or 2, characterized in that B, B ₆ O and B ₂ O _{3 are} successively deposited on the connecting rod ( 1 ) and / or the adhesion promoter layer ( 3 ). 20. The method according to claim 4, characterized in that a connecting rod ( 1 ) is a metallic, in particular iron-bearing connecting rod ( 1 ) and that as the boride of the adhesive layer ( 3 ) is a metal boride, preferably Fe ₂ B and / or FeB , is formed. 21. The method according to claim 2, characterized in that as an adhesion promoter layer ( 3 ) on the surface to be coated ( 2 ) of the connecting rod ( 1 ) a boron and carbon, before a boron carbide layer (B ₄ C) is deposited. 22. The method according to claim 20, characterized, that the FeB has an An in relation to all iron borides partly less than 20%, preferably less than 10% and especially before trains less than 1% is formed. 23. The method according to claim 2, characterized in that after the formation of Fe ₂ B in the region of the surface to be coated ( 2 ) of the connecting rod ( 1 ), the proportion of boron in the separating gas phase increases by at least 20% within 5 s becomes. 24. The method according to claim 2, characterized in that after the formation of Fe ₂ B in the region of the surface to be coated ( 2 ) of the connecting rod ( 1 ) at least the near-surface temperature of the connecting rod ( 1 ) is lowered. 25. Connecting rod with a lubricant layer, which at least in some cases has boric acid as a dry lubricant, characterized in that an adhesion promoter layer ( 3 ) is arranged below the lubricant layer ( 5 ), that the adhesion promoter layer ( 3 ) boron and / or carbon and / or nitrogen, that the lubricant layer ( 5 ) is applied from a gas phase, that an intermediate layer ( 4 ) is arranged between the lubricant layer ( 5 ) and the adhesion promoter layer ( 3 ), that the intermediate layer ( 4 ) has boron and oxygen and that the intermediate layer ( 4 ) has an oxygen gradient which increases with increasing distance from the adhesion promoter layer ( 3 ). 26. Connecting rod according to claim 25, characterized in that the lubricant layer ( 5 ) has at least 5%, preferably 10% and particularly preferably 30% boric acid (H ₃ BO ₃ ) at least near the surface. 27. Connecting rod according to claim 25, characterized in that the adhesion promoter layer ( 3 ) is designed as a boronized and / or carbonized and / or nitrided and / or carbonitrided layer. 28. Connecting rod according to claim 25, characterized in that the intermediate layer ( 4 ) has boron, B ₆ O and B ₂ O ₃ . 29. Connecting rod according to claim 25, characterized in that the intermediate layer ( 4 ) starting from the adhesion promoter layer ( 3 ) first has boron, then B ₆ O and then B ₂ O ₃ , the B ₂ O _{3 being} in direct contact with the Lubricant layer ( 5 ) is arranged.