DE102009020674B4 - Method of manufacturing a component and coated component - Google Patents

Abstract

A method for producing a coated component as a cylinder bore, connecting rod or bearing shell in an internal combustion engine, which has a thermal spray layer as a surface layer, wherein the surface layer, in particular a bearing metal alloy layer or a wear protection layer is applied by means of a spraying process on a surface of the component and the component the surface layer is subsequently aftertreated by a knocking or hammering treatment, in particular by means of a striking head for densification and hardening, characterized in that the knocking or hammering machining of the component takes place with an average energy input or a mean deformation energy above 100 kJ / m ² and in that the knocking or hammering processing of the component results in a surface of the sprayed layer having a pattern of closely spaced, contiguous, and / or partially overlapping ones n recesses having an area in the range of 0.2 to 10 mm ² .

Description

The invention relates to a method for producing a coated component according to the preamble of patent claim 1 and to a coated component according to the preamble of claim 11.

In modern internal combustion engines in motor vehicles occur on friction surfaces, for example in cylinder liners or connecting rods, high mechanical loads, which can lead to material abrasion. In order to make the loaded material areas more wear-resistant, spray coatings are used in many cases. Preferred, well-known methods are, for example, the so-called plasma spraying, flame spraying or arc wire spraying or cold gas spraying. Although these, in particular thermal, injection methods increase the wear resistance of the base material (substrate material), they also have a certain porosity due to the process. This porosity is always above about five percent in conventional spray coatings. The porosity of the sprayed layer significantly reduces its strength and wear resistance.

Usually, the untreated sprayed layers are finished by grinding or by so-called honing process. In the DE 198 47 608 B4 It is also proposed to reduce the porosity of a sprayed layer by compacting the sprayed layer by means of a special roller. By this rolling, however, the required pressure is not applied, resulting in a homogeneous surface and a homogeneously compacted layer.

Also the DE 10 205 007 587 A1 describes a method for densifying a thermal sprayed layer, wherein the densification is to take place by a mechanical deformation.

From the WO 02072907 A1 a method for producing coated holes is known. The bore wall is plasma-sprayed with a coating material and the bore wall is subjected to roll-pressing.

The DE 10 2005 007 587 A1 discloses a method for post-treating coatings from thermal or kinetic spraying processes or a cold gas spraying process. The applied layers are at least partially densified by mechanical deformation.

From the DE 10 2006 033 004 A1 is an electromechanical device for machining, smoothing and work hardening of the surface of tools, machine and other parts known by the hammering of a percussion head on the surface.

An apparatus for producing a sliding surface on an inner wall of a cylinder, in particular the cylinder running surface of a reciprocating engine is in the DE 198 47 308 B4 disclosed. In this case, powdered additives are thermally sprayed with a powder applicator burner moved on the inner wall and compacted by rolling after the spraying on the surface of the base material.

Disadvantageously, known processes lead in this case only to a moderate compression of the sprayed layer. The known methods have the disadvantage that only low deformation energies can be entered without the coatings being sheared off, peeled off or disrupted. The degree of compaction and the hardening of the coating are still unsatisfactory. The possibilities of a local variation of the surface treatment is hardly given with the known methods.

The object of the invention is to provide a thermal sprayed coating which has a lower porosity and a higher strength compared to the prior art, and to show suitable processes for producing such a coating.

This object is achieved by a method for producing a coated component having the features of patent claim 1 and a component having the features of claim 11.

In such a method, first of all a surface layer is applied by means of a thermal spraying method for a surface of the component, and the component with the surface layer is subsequently aftertreated by a knocking or hammering machining by means of a tapping tool. According to the invention, it is provided that a very high deformation energy is introduced into the sprayed layer by means of the knocking or hammering treatment of the component, which is on average above 100 kJ / m ² .

It is of particular importance that a very high energy can be introduced into the surface or sprayed layer by the selected process of knocking or hammering (in the following also referred to simply as knocking) without the layer being shattered, flaked off or scraped off. It is the essence of the process that deformation energies above about 100 kJ / m ² can be entered. Depending on the sprayed layer, deformation energies above 150, 200 or even 300 kJ / m ^{2 are} expedient. The impact of this high energy is a compression and cold forging the material of the sprayed layer.

For example, the strain energy may be determined by the difference between the kinetic energy of the knocking tool before impacting the surface and the kinetic energy thereafter. Since the size of the tool tip can be chosen differently, the energy is expediently related to the area of the respective impression of the knocking tool in the fuel layer.

The knocking or hammering processing brings the fact that continuously individual impressions are produced instead of processing paths quite new process possibilities with it, which are basically different from the known rolling or pressing.

In particular, the desired high deformation energy of the treatment requires special tools. Such a principle suitable tool is for example from the DE 10 2006 033 004 A1 known. In contrast, ultrasonic methods, such as in the US 20080035627 A1 or WO 2007060284 A1 only partially suitable.

It has been found after several investigations that in particular a knocking process comprising such a periodic recurring knocking results in a particularly homogeneous, non-porous sprayed layer. In particular, it has been found that a particularly advantageous compressive residual stress is introduced into the surface of the sprayed layer and additionally into the main body of the component by the knocking process. The compressive residual stress of the thermal sprayed layer causes the layer to be pressed onto the substrate by its inherent pressure and thus the adhesion on the base body is increased. This compressive residual stress, in contrast to a tensile residual stress, is particularly advantageous since it prevents the layer from flaking off. In the case of the metallic parts of the sprayed layer, the knocking process virtually results in cold forging. As a result, the metallic material also undergoes the hardening known by forging processes or hardening. The nature of the metallic surface is therefore only of minor importance, because the effects described can be generated in principle on any type of metallic surface coating.

The periodic knocking process is also very advantageous for the reason that it can be set optimally by many different parameters. One of the parameters of the knocking process is a knocking frequency. This is the frequency with which a knocking tool is tapped on the sprayed layer. This knocking frequency advantageously has more than 20 Hz. The frequency upwards is essentially limited by the required energy, which has to be entered into the tool. Therefore, tools with frequencies below the ultrasonic range are particularly useful.

The knocking tool can be configured in different geometries. In addition to a cylindrical shape or a drop shape, a spherical shape has proven particularly useful as a tool tip of the knocking tool. It has been found that it is particularly advantageous if a ball diameter of the tool tip between 2 mm and 50 mm is selected.

It is particularly advantageous, if the size of the knocking tool or the tool tip, to be selected so that the impression surface in the treated surface is in the range of area in the range of 0.2 to 10 mm ² .

Depending on the deformation energy or geometry of the tool tip, depressions of different depths can be formed.

It is also important in which impact angle the knocking tool strikes the layer or the substrate. This can be seen in particular in comparison with the known methods of rolling, where the forces can basically only be entered into the surface at a shallow angle (rather tangentially) and therefore high shear forces act on the coating. An impact angle between 5 degrees and 90 degrees has proven to be useful. In this case, angles in the range of 45 ° to 90 ° and 60 ° to 90 ° are particularly favorable. Ideal is an approximately vertical angle.

The method has the great advantage that, even with curved or complex surface geometries of the component, very steep angles or vertical angles can still be set due to the small dimensions of the knocking tool.

This impact angle is particularly important in the processing of curved surfaces of importance.

Another parameter with which the result of the knocking process can be sustainably influenced is the choice of a so-called knock gap. This is to be understood as meaning the stroke that the knocking tool is lifted from the surface of the sprayed layer at each period in order to then impact the sprayed layer again. This knocking gap is advantageously between 0.01 mm and 3 mm.

When using a pneumatic knocking system, knocking gaps can also be evident be lower than 3 mm. The upper limit here is about 10 mm is important.

In a further embodiment according to the invention, the compacting and hardening of the sprayed layer takes place in two steps. Hierdruch it is also possible to bring the very high deformation energies in the spray layer. The deformation energy is chosen differently in the two steps, the energy is higher in the second step.

In an expedient embodiment of the invention, a knocking tool is used in a first step, which impacts on the sprayed layer with a smaller knocking gap. In a next method step, the tool is reduced and the distance to the substrate, so the knocking gap, increased. When using balls as knocking tools, the ball of the first step has a larger diameter than the ball of the second method step. As a result, the surface is already pre-solidified in the first step, by the second process step, which causes a higher point energy input by the higher knock gap and the smaller ball, the porosity in the layer is further reduced again and the compressive residual stress of the layer and the hardening on elevated.

It is furthermore particularly advantageous if the impacts of the knocking tool against the component in the second pass of the knocking process have a higher energy than the strikes of the knocking tool against the component in the first pass. The deformation energy in the first pass should not be higher than 50% of the deformation energy chosen in the subsequent step. In the first pass, the thermal spray layer is pre-compacted by still relatively low-energy knock, so that higher energies can be introduced in the second pass without damaging the surface layer. In the second pass, internal compressive stresses are therefore built up particularly efficiently both in the surface layer and in the near-surface region of the main body of the component, which substantially improves the strength of the component. The deformation energy in the first step is preferably already above 100 kJ / mm ² .

Advantageously, spraying layers are treated by the said method, which are used as anti-friction or anti-wear layers. These are tribo layers which are subject to tribological stress.

These include in particular spray coatings on components that are part of an internal combustion engine. In particular, cylinder liners and connecting rods or bearing shells have been found to be particularly suitable components whose coatings can be compacted, solidified and hardened by said method.

Further advantageous embodiments of the invention and further features will be explained in more detail with reference to the following figures. In this case, equivalent features in different embodiments are each provided with the same reference numerals.

Showing:

1 the schematic sequence of a knocking process in two steps on a thermal spray coating,

2 the application of the knocking process to a curved surface of a basic body,

3 a thermal spray coating on a body directly after the injection process and

4 a sprayed layer after the compression process.

The process for producing a sprayed coating comprises two steps. In the first step, a thermal spray coating on a base body 4 applied. Methods for the production of thermal spray coatings are well known. This may be, for example, a plasma spraying, a flame spraying or an arc wire spraying. Also, other, not mentioned spraying process can be used in this process. The resulting sprayed layer 2 is applied in particular to a component of an internal combustion engine. Cylinder liners or connecting rods or bearing shells offer this. The sprayed layer 2 is compressed in a further process step by a knocking process. The knocking process is in this case periodically designed, which means that a knocking tool is raised periodically and with a certain energy back to the sprayed layer 2 strikes. The tapping machining of the component is carried out in at least two separate passes, resulting in a particularly good reduction of the number of pores of the surface and particularly high residual compressive stresses in the component.

In 1 is shown schematically such a knocking process. This is a likewise schematically shown knocking device 24 , which at one end a knocking tool in the form of a ball 6 has, periodically moved up and down. This periodic up and down movement, for example, by a here again only schematically illustrated eccentric bearing or even be designed an electromagnetic drive.

In addition to the eccentric and electromagnetic drives, pneumatic drives are also suitable.

The knocking device 24 in 1 is shown in several states. On the far left is the ball 6 the knocking device 24 just on a sprayed layer 2 , in turn, on a basic body 4 is up, up. spray layer 2 and basic body 4 are in this simplified illustration 1 shown as flat surfaces, which serves to illustrate the knocking process schematically easier. In a next period, the knocking tool is raised, creating a so-called knocking gap 12 , This knocking gap 12 or another, higher knock gap 14 are in the two right representations of the knocking device 24 shown. This is an upper reversal point, after which the ball reaches 6 or a ball 20 back to the sprayed layer 2 falls.

This periodic process can be repeated at a frequency that can range between 20 Hz and 500 Hz (knock frequency). Lower frequencies usually do not bring the desired compaction effect, higher frequencies can the layer 2 damage. During the knocking process, either the substrate becomes 4 with the sprayed layer 2 or the knocking device 24 emotional. By the resulting relative movement between the knocking tool and the layer 2 it comes to densification of the layer 2 along a predetermined line.

Both the knocking gap 12 . 14 as well as the diameter of the ball 6 . 20 , which in the present example are designed as a knocking tool, have proven to be parameters by which the compression process of the sprayed layer 2 can be significantly influenced. Therefore, in the following with reference to the example of 1 to discuss a two-stage consolidation process.

In the right half of the 1 are 2 rappers 24 represented, which are separated by a dashed line. The left-hand knocking device 24 illustrates a first step I of the compaction process. This is a knocking tool with a ball 6 used a first ball diameter 8th having. Further, the knocking device is 24 in the first step I adjusted so that between the sprayed layer 2 and the ball 6 in the upper reversal point of the sphere 6 a knocking gap 12 consists. This knocking gap 12 is relatively low. It is for example 0.05 mm (preferably between 0.03 mm and 0.07 mm). The ball diameter is 16 mm in this example. In this step I, the thermal spray coating 2 precompacted. The combination of a relatively low knock gap 12 and a relatively wide ball diameter 8th causes per unit area on the sprayed layer 2 a relatively low energy is introduced.

After the precompacting step I, a further compaction step II takes place. This compaction step II is described in FIG 1 shown schematically on the right of the dashed line. The knocking device 24 is designed according to step II so that the knocking tool in the form of a ball 20 There is a second ball diameter 16 has, for example, with 8 mm diameter only half as large as the ball diameter 8th the ball 6 from step I. Hereinafter is the knocking device 24 after Step II designed so that another knocking gap 14 comes to fruition with, for example, 0.8 mm (preferably 0.6 mm to 1 mm) is more than sixteen times as large as the knock gap from step I. Due to the smaller ball diameter 16 in conjunction with the higher knock gap 14 In step II per unit area a significantly higher energy in the sprayed layer 2 introduced, as is the case in step I. The already pre-compressed in step I spray coating 2 gets on the surface 30 (see. 4 ) of the sprayed layer 2 further smoothed, and it thereby becomes one in the sprayed layer 2 and also in the basic body 4 induced residual compressive stress further increased. A typical compressive residual stress in a sprayed layer treated according to steps I and II 2 is about 70 MPa. A sprayed layer treated by the prior art method which has been rolled has only a compressive stress of 30 MPa. An untreated sprayed layer 2 not only has no compressive residual stress, but even a tensile residual stress of 70 MPa, which is negative for the strength.

In 2 is shown as a knocking device 24 also on curved surfaces, as is the case for example in a connecting rod or a bearing shell, can be applied. Here, the ball hits in a certain impact angle 10 on the layer 2 , The main body 4 in 2 is shown in schematic form a connecting rod half.

In the 3 and 4 are schematically two thermal spray coatings 2 or two 2 ' shown, wherein the 3 the initial structures of a thermal spray coating 2 show the 4 now shows the same sprayed layer as a sprayed layer 2 ' after a described compaction process. The thermal sprayed coating 2 gem. 3 has a very rough surface 28 on, below the surface 28 includes the sprayed layer 2 many big pores 26 , The porosity of a sprayed layer in the initial state is in this case about 4%. After described treatment by the periodic knocking process is a thermal spray coating 2 ' before that, as in 4 shown a smooth surface 30 wherein the porosity was reduced from 4% to about 0.3%.

By the described compression method, in particular by the two steps I and II of the periodic knocking process, the topography of the surface, ie the final spray-layer surface 30 to be influenced. After pre-compaction acc. step 1 can in step II targeted profiles in the surface 30 the sprayed layer 2 ' be introduced. These profiles can be configured for example in the form of oil pockets or grooves. Such oil pockets are particularly advantageous in oil-lubricated component areas, such as a cylinder surface. Through targeted oil pockets or grooves, the oil can be stored in these wells, which is referred to as so-called reservoirs. The oil stored in these topographic depressions can advantageously act as required in the rubbing process between the part to be coated and the counterpart moved thereon.

Another aspect of the invention relates to the components which are obtainable in particular by the method according to the invention. These are components with a thermal spray layer of metal alloys or a metal / ceramic composite material. As materials, in particular from bearing metal alloys or wear protection materials are of importance. The spray coatings may also be complex multilayer coating systems, which are known, for example, from plain bearings, raceways or wear protection coatings. According to the invention, the sprayed layer is post-compacted by a mechanical aftertreatment and cured.

The aftertreatment is a knocking or hammering mechanical aftertreatment.

According to the invention, coatings having a porosity of the sprayed layer below 1.5% by volume are provided. Particularly preferably, the porosity of the sprayed layer is below 1% by volume.

The knocking or hammering mechanical aftertreatment gives a very characteristic surface topography. The surface is no longer flat, but has a wavy topography, which is characterized by a variety of wells. The depressions correspond to the prints of the hammering or tapping processing. As a rule, the individual impressions can still be identified individually, even with repeated or superimposed aftertreatment.

Thus, the surface of the sprayed layer preferably has a pattern of closely spaced, adjoining and / or partially overlapping recesses. The area of the individual depressions is preferably in the range of 0.2 to 10 mm ² . The individual impressions can overlap, resulting in a flattened wave profile in the surface.

The depressions preferably correspond in their geometry substantially to the tool tips of the tapping or hammer tools used.

The pattern of the depressions or impressions can be designed differently.

In a first embodiment, the pattern is formed by a regular sequence of web-shaped depressions. The webs particularly preferably have a common preferred direction. For example, the tracks can be parallel. or be aligned perpendicular to the subsequent sliding or tribological load on the surface. This is of particular interest when lubricated sliding pairs are used and the recesses are formed as lubricant pockets, which extend approximately perpendicular to the sliding direction.

Likewise, a disordered arrangement of the wells is possible. Here, the pattern is formed by an irregular or stochastic arrangement of depressions. Preferably also the area and depth of the individual recesses are formed differently. It has been shown that it is precisely the stochastic distribution in lubricated sliding pairs that gives particularly good results. These include, for example, connecting rods or cylinder liners in internal combustion engines.

The component can also have several separate densified and hardened areas. Depending on the requirement profile, these can be equipped with identical and / or different patterns of recesses.

LIST OF REFERENCE NUMBERS

2

spray layer

4

substratum

6

Ball (knocking tool)

8th

Ball diameter

10

angle of impact

12

First knock gap

14

Second knock gap

16

Second ball diameter

20

Second ball

22

Bearing shell connecting rod

24

rapper

26

pore

28

Layer surface, originally

30

Layer surface, treated

Claims (16)

A method for producing a coated component as a cylinder bore, connecting rod or bearing shell in an internal combustion engine, which has a thermal spray layer as a surface layer, wherein the surface layer, in particular a bearing metal alloy layer or a wear protection layer is applied by means of a spraying process on a surface of the component and the component the surface layer is subsequently aftertreated by a knocking or hammering treatment, in particular by means of a striking head for densification and hardening, characterized in that the knocking or hammering machining of the component takes place with an average energy input or a mean deformation energy above 100 kJ / m ² and in that the knocking or hammering processing of the component results in a surface of the sprayed layer having a pattern of closely spaced, contiguous, and / or partially overlapping ones en has depressions having an area in the range of 0.2 to 10 mm ² . A method according to claim 1, characterized in that the knocking or hammering processing of the surface layer takes place in at least two passes with increasing energy. A method according to claim 1 or 2, characterized in that the tapping or hammering processing of the surface layer is carried out until the porosity of the surface layer has fallen below 1.5 vol .-%. The method of claim 1, 2 or 3, characterized in that the knocking process has a knocking frequency of more than 20 Hz. Method according to one of the preceding claims, characterized in that the tool tip of the knocking tool as a ball ( 6 . 20 ) is trained. A method according to claim 5, characterized in that a ball diameter of the knocking tool ( 8th . 16 ) between 2 mm and 50 mm, and the area of the impression is set to 0.5 to 6 mm ² . Method according to one of the preceding claims, characterized in that the tool tip of the knocking tool with respect to the surface of the component an impact angle ( 10 ) between 45 ° and 90 °. Method according to one of the preceding claims, characterized in that a knocking gap ( 12 . 14 ) is between 0.01 mm and 3 mm and in the first step (I) a first knock gap ( 12 ) is used with a first knocking tool and in the second step (II) a second knocking gap ( 14 ) is used with a second knocking tool, wherein the second knocking gap ( 14 ) is greater than the first knock gap ( 12 ) and the second knocking tool is smaller than the first. Method according to claim 7 or 8, characterized in that the knocking tools of the first step and the second step comprise balls ( 6 . 20 ), and the ball ( 6 ) of the first step has a larger diameter ( 8th ) than the ball ( 20 ) of the second step. Method according to one of claims 7 to 9, characterized in that the impacts of the knocking tool against the component in the region of the surface layer in the second passage have a higher energy than the impacts of the knocking tool against the component in the region of the surface layer in the first passage. Component in a sliding mating in internal combustion engines with a thermal spray layer of metal alloys or a metal / ceramic composite material, in particular bearing metal alloys or wear protection materials, wherein the sprayed layer is densified and cured by a knocking or hammering mechanical aftertreatment, characterized in that the porosity of the sprayed layer Below 1.5 vol .-% and the surface of the sprayed layer has a pattern of closely spaced, contiguous and / or partially overlapping recesses having an area in the range of 0.2 to 10 mm ² . Component according to claim 11, characterized in that the recesses in their geometry substantially correspond to the tool tips of the knocking or hammering tools. Component according to one of claims 11 or 12, characterized in that the pattern is formed by a regular sequence of web-shaped depressions extending in a preferred direction. Component according to one of claims 11 or 12, characterized in that the pattern by an irregular or stochastic arrangement is formed on depressions. Component according to one of claims 11 to 14, characterized in that the recesses are formed with different depth and different lateral dimensions. Component according to one of claims 11 to 15, characterized in that the component has a plurality of mutually separate densified and hardened areas with the same and / or different patterns of recesses.

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