CN1340111A - Method for machining a component surface - Google Patents

Abstract

This invention relates to a method for treating the surface of a component using a particle beam generated by thermal spraying. The particle beam scans the surface of the component to be treated, at least partially, according to a predetermined pattern.

Description

Methods of Treating Part Surfaces

The invention relates to a method according to the preamble of claim 1 for the treatment of a surface of a component located in a treatment region with a plasma beam.

The hypoeutectic aluminum-silicon alloy, which is mainly used in the cylinder crankcase, is not suitable for the friction load of the piston-piston ring-cylinder working surface system because of too little silicon phase composition for wear resistance. Hypereutectic aluminum-silicon alloys, such as the alloy _AlSil7Cu4Mg , have _a sufficient silicon crystalline composition. Through chemical and/or mechanical treatment steps, this hard, wear-resistant structural component is increased relative to a matrix composed of aluminum crystals and forms an essential support surface component. However, disadvantages of such alloys are poor castability, poor handleability (machinability) and high cost relative to hypoeutectic and quasi-eutectic alloys.

One possibility to overcome these disadvantages is to cast in cylinder liners made of wear-resistant materials such as gray cast iron alloys and supercrystalline aluminum alloys. But the problem at this time is the bond between the cylinder liner and the recast material, which is only guaranteed by mechanical engagement. By using a porous ceramic liner material, it is possible to impregnate the ceramic liner material during the casting process to form a material-to-material bond. This requires slow filling of the mold and application of high pressure, which greatly reduces the economics of the method.

Another method is to apply hypoeutectic alloys and quasi-eutectic alloys directly to the working surface as electroplated coatings. However, this method is expensive and is not sufficiently wear-resistant tribochemically. Yet another method is to form thermal spray coatings, which are likewise applied directly to the work surface. However, the adhesive strength of these coatings is insufficient due to the mere micromechanical connection.

It has therefore already been proposed to modify the surface by remelting it with a laser, injecting an alloy material, dispersing it and applying a coating, as disclosed, for example, in document DE 196 43 029 A1. The disadvantage here, however, is that the cylinder face coating produced in this way has too many perforations, and its immersion depth is low, as a result, the adhesion of the applied coating is low, which is not satisfactory.

The object of the present invention is to provide an improved method of the above-mentioned kind which overcomes the disadvantages mentioned above and which enables rapid production with short processing times.

According to the invention, this object is solved by a method of the above-mentioned kind with the characterizing features of claim 1 . Some advantageous developments of the invention are given in the dependent claims.

According to the invention, in a method of the above-mentioned kind it is provided that the particle beam scans the surface of the component to be treated at least partially according to a predetermined pattern.

This has the advantage that a reduction in processing time is achieved by only partially processing, for example, less loaded areas.

A suitable way is to carry out thermal spraying by means of flame spraying, plasma spraying with a plasma beam or high-pressure spraying.

For example, the predetermined pattern includes at least one scan of the surface to be treated, especially two reverse scans or multiple helical scans at a predetermined ramp angle α, for example 1°-90°. Alternatively or additionally, the pattern can include a linear, angular, cross-shaped or point-shaped scan of the surface to be treated. When the surface to be processed at this time is the cylinder working surface that matches the piston in a cylinder of the internal combustion engine crankcase, then according to the requirements of the purpose, the scanning according to a predetermined pattern is between the top dead center and the bottom dead center of the piston. carried out in an area of .

In regions of the component that are exposed to high loads, for example, the plasma beam scans the surface of the component to be treated at least partially over the entire surface in order to achieve alloying over the entire surface. If the surface to be machined is the cylinder running surface associated with the piston in a cylinder of the crankcase of the internal combustion engine, then the scanning of the entire surface is preferably carried out in an area between the upper dead center and the lower dead center of the piston. In this case, the scanning of the full surface is carried out, for example, at least at a height corresponding to the width of the piston ring set of the piston, wherein it is particularly advantageous that the full surface scan will exceed the width of the piston ring set of the piston by 12 times the piston stroke. %, for example about 5mm.

By melting the material of the component with the laser beam in a local area immediately before, in this area and/or in a local area after this area of contact with the particle beam, a process result is obtained in which the immersion depth is lower. Larger, better material entry and better bonding of the material coated with the plasma beam to the material of the component.

In order to further improve the properties of the applied material layer, the component surface is additionally treated with a laser beam after treatment, in particular remelted.

According to the requirements of the purpose, a molten pool is formed by melting the component material in the coating zone.

For example, components are made of aluminum and in particular the crankcase of a piston internal combustion engine is coated on the cylinder running surfaces of its cylinders. In a preferred embodiment, a cooling medium, in particular gaseous nitrogen or a cooling liquid, flows through the water chamber of the crankcase during production of the wear-resistant surface.

In order to produce a wear-resistant surface, in a particularly advantageous manner, a powdery material, especially silicon or a silicon alloy, is applied by means of a particle beam to the material of the component, which is preferably aluminum at this time .

A wear-resistant surface, in particular in the form of a thermally sprayed layer, is formed on the surface of the component, for example by surface treatment. It is particularly advantageous in this case if, during the process for producing the wear-resistant surface, a subsequent honing process is carried out as a supplementary process, whereby the hardened surface can be smoothed.

Additional features, advantages and advantageous configurations of the invention emerge from the subclaims and from the following description of the invention with reference to the figures. In the attached picture,

Figure 1 is a schematic cross-sectional view of an apparatus for treating the surface of a component with a plasma beam and a laser beam,

Figure 2 is an enlarged view of a treatment area,

Figure 3 is a schematic diagram of a first preferred embodiment of a processing pattern according to the present invention,

Figure 4 is a schematic diagram of a second preferred embodiment of a processing pattern according to the present invention,

Fig. 5 is a schematic diagram of another preferred embodiment of a processing pattern according to the present invention.

A preferred embodiment of the device for surface treatment shown in FIGS. 1 and 2 comprises a plasma burner 10 and a laser 12, wherein the plasma burner 10 emits a plasma beam 14 with a coating material 16, and the laser 12 A laser beam 18 is emitted. A component to be treated is here a crankcase (not shown in detail) with corresponding cylinder bores 19 , wherein the surface 20 of the cylinder wall 22 is to be treated. The crankcase is made of aluminum, for example, and the surface 20 is treated to form a wear-resistant surface in the region of the running surface of the cylinder on which a piston, not shown, moves up and down in the cylinder 19 . For this purpose, the coating material 16 is, for example, powdered silicon, which is applied as a molten coating element to the surface 20 by means of the plasma beam 14 . For this purpose, the plasma burner 10 is inserted into the cylinder 19 and rotated about its own axis, as indicated by arrows 24 (see FIG. 1 ) and 25 (see FIG. 2 ), so that the plasma beam 14 scans the surface 20 . The area that the plasma beam 14 is now contacting is referred to below as the treatment or coating area 26 . In this region, the coating material 16 penetrates into the material of the cylinder wall 22 .

The laser 12 arranged additionally outside the plasma burner 10 is arranged in such a way that the laser 12 contacts the surface 20 ahead of the plasma burner 10 in the treatment direction 25 . The energy of the laser 12 is selected in such a way that at the point of contact of the laser beam 18 the material of the cylinder wall 22 is melted so that a molten zone or pool 28 is formed before the contact of the plasma beam 14 . In other words, the plasma beam 14 follows the laser beam 18 , adding the coating material 16 contained in the plasma into the melting zone 28 . Coating material 16 is thus optimally alloyed into the material of cylinder wall 22 .

A laser coating and a plasma coating are thus combined and carried out in a single process. The distance between the laser beam 18 and the plasma beam 14 at this point is a function of the laser power, the desired depth of fusion, the length of the fusion zone, the reflectivity of the material of the cylinder wall 22 and the diameter of the cylinder 19 .

Now according to the present invention, the scanning of the surface 20 by the double beams consisting of the laser beam 18 and the plasma beam 14 is not carried out on the entire cylinder working surface, but is carried out according to a predetermined pattern in a predetermined area. Figures 3 to 5 show examples of such patterns as laser implanted alloy and coated channels 29 .

As can be seen from FIG. 3, the scanning in the region of the upper dead center 30 (OT) and the lower dead center 32 (UT) of a piston, not shown, is carried out over the full surface, and the height of the scanning corresponds to the height of the piston The height 34 of the ring set plus, for example, 5 mm corresponds to 12% of the piston stroke. The scanning of surface 20 in the region between OT30 and UT32 is performed helically at a rise angle @ of 1 to 90 degrees.

In the pattern of Figure 4, the surface 20 is scanned along two opposing helical lines. In this case, in a preferred embodiment not shown, three or more helical wires are also used. According to the exemplary embodiment of FIG. 5, the surface 20 is scanned linearly, angularly, crosswise or pointwise.

Partial scanning of the surface 20 in the less stressed area ensures on the one hand that the cylinder running surface has a sufficiently wear-resistant surface and on the other hand shortens the processing time in production and reduces the costs accordingly.

In accordance with the present invention, the laser 12 is utilized to enhance the edge-bound silicon composition 16 of the hypoeutectic and quasi-eutectic aluminum alloys. To this end, in a single-step process shown, during the treatment with the laser, aluminum silicon powder is applied in suitable feed quantities into the resulting melting zone 28 . Depending on the load, coating thicknesses of more than 2 mm can now be achieved. The degree of mixing with the base material is now less required. The silicon component content in the supplied powder is in the range between 20% and 40%. If very small coating thicknesses with a high degree of mixing are required, a powder 16 with a silicon content of between 40% and 60% will be used. Since the powder particles 16 should dissolve completely in the melt zone 28, the selected process parameters such as advance speed and laser power must ensure a minimum melt pool lifetime. Choosing an appropriate beam intensity distribution helps reduce processing costs. Furthermore, it is advantageous to have a nugget with as rectangular a cross-section as possible and thus to have as few overlapping points of line crossings as possible.

In addition to the alloy treatment of the entire cylinder working surface as required, the treatment is mainly partial. The high load areas at the upper and lower turning points of the piston (top dead center 30 and bottom dead center 32) are full surface remelted, while the low load areas in between have only individual laser treatment lines (e.g. diamond pattern, See Figures 3 to 5), it provides adequate friction protection here. This approach greatly reduces machining time, since only a small part of the working surface needs to be processed. If the entire or large part of the running surface is to be laser surface treated, cooling of the crankcase is required, for example by passing a cooling medium through the existing cooling water system of the crankcase. In the case of only partial treatment, it is sufficient to remove the entrained energy, for example by contact with a water-cooled copper plate, in addition to removing it from the upper and lower sides.

In conclusion, the present invention proposes a combination of thermal spraying (plasma spraying) and laser surface treatment. In this case, by remelting the previously applied spray layer, the porosity of the coating is avoided and a connection with the base metal is produced at a sufficiently large melting depth. It is suitable to carry out full-surface remelting with laser 12 only in high-load areas, and not to remelt in the remaining areas or to only perform remelting in areas of a pattern type, such as diamonds, shaded parts and dot patterns.

It is not the only possibility to carry out a supplementary remelting treatment of the applied spray coating. Immediately in front of the plasma-coating zone along the advancing direction 25 , the molten pool 28 produced by the laser beam 12 leads to a metallic connection of the powder particles 16 supplied in the solid or liquid state to the substrate. At high advance speeds, the coating structure consists of base material, thin alloy zones with dissolved and only partially melted primary powder particles 16 and a relatively thick sprayed layer. Due to the improved micro-occlusion under the correspondingly selected processing parameters, the coating adhesion between the sprayed layer and the alloy layer can be greatly improved by means of this intermediate coating, which saves the need for the sprayed layer to achieve sufficient In order to reduce the adhesion of the coating, an expensive and cost-intensive pretreatment (cleaning and irradiation) of the coating surface 20 to be applied is necessary. In this case, the described coating treatment for surface treatment of the component can be followed by a honing treatment of a ground surface.

The above description of the preferred embodiment is to be understood as illustrating the invention by way of example only. A flexible and particularly preferred embodiment of the invention consists in combining thermal spraying and laser surface treatment in such a way that when the coating material 16 is applied over the entire surface with thermal spraying or the cylinder is sprayed over the entire surface When the working surface of the laser is used, the laser or the laser beam only irradiates the local line part, where the line is formed similar to the pattern described above for the plasma coating. In this case, the laser is continuously moved together, for example during a spraying process, but is only partially switched on so that a desired pattern is obtained.

Claims (19)

1. with a method, it is characterized in that particle beam scans parts surface to be processed according to a predetermined pattern at least in part by the particle beam processing element surface of thermospray generation.

2. according to the method for claim 1, it is characterized in that thermospray is implemented by means of flame plating, the plasma spraying with a beam-plasma or high pressure (HV) spraying.

3. according to the method for claim 1 or 2, it is characterized in that predetermined pattern comprises at least to surface to be processed single pass, especially twice reverse scanning or with the repeatedly spiral scanning of a predetermined ascending angle at least in part.

4. according to the method one of in the claim 1 to 3, it is characterized in that ascending angle α comprises the angle of one 1 °-90 ° of scopes.

5. according to the method one of in the aforementioned claim, it is characterized in that, surface to be processed is the cylinder face that matches with a piston in the cylinder of crank case of internal combustion engine, is to carry out in the upper dead point of piston and a zone between the bottom dead centre according to a scanning of subscribing pattern.

6. according to the method one of in the aforementioned claim, it is characterized in that pattern comprises linear, the scanning corneous, that intersect and/or point-like that surface to be processed is carried out.

7. according to the method one of in the aforementioned claim, it is characterized in that a beam-plasma scans at least in part entirely outwardly to parts surface to be processed.

8. according to the method for claim 7, it is characterized in that surface to be processed is the cylinder face that matches with a piston in the cylinder of crank case of internal combustion engine, the scanning on full surface is to carry out in a zone of the upper dead point of piston and/or bottom dead centre.

9. according to the method for claim 8, it is characterized in that the scanning on full surface is carried out on a height at least, this height is corresponding to the width of the piston ring group of piston.

10. according to the method for claim 9, it is characterized in that the scanning on full surface is 12% of travel of piston above the amount of the width of the piston ring group of piston, for example is approximately 5mm.

11. the method according to one of in the aforementioned claim is characterized in that, near the regional area before the particle beam zone of action, in this zone and/or in the regional area after this zone, with laser beam the material of parts is implemented fusing.

12. the method according to claim 11 is characterized in that, fusing utilizes laser beam to carry out according to a predetermined pattern.

13. the method according to claim 11 or 12 is characterized in that, by molten bath of fusing formation of component materials.

14. the method according to one of in the aforementioned claim is characterized in that parts are crankcases of a piston type internal combustion engine, the coating of coating is to implement on the cylinder face of its cylinder.

15. the method according to claim 14 is characterized in that, during handling, makes a kind of heat-eliminating medium, especially gas, nitrogen or a kind of cooling liqs flow in the water cavity of crankcase.

16. the method according to one of in the aforementioned claim is characterized in that, by means of particle beam a kind of powder attitude material, especially silicon or a kind of silicon alloy is coated on the component materials.

17. the method according to one of in the aforementioned claim is characterized in that parts are made with aluminium.

18. the method according to one of in the aforementioned claim is characterized in that, by surface treatment, constitutes a wearing face, the especially wearing face of thermally sprayed coating form on the surface of parts.

19. the method according to claim 1 is characterized in that, follows after the thermospray operation honing processing of surface enforcement of applying coating.

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