Refrigeration – Processes – Treating an article
Reexamination Certificate
2001-08-20
2003-10-21
Doerrler, William C. (Department: 3744)
Refrigeration
Processes
Treating an article
C427S446000, C148S524000
Reexamination Certificate
active
06634179
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a process for producing wear-resistant surfaces on components made from an AlSi alloy. The invention also relates to a configuration for producing wear-resistant surfaces on components made from an AlSi alloy.
Hypoeutectic aluminum-silicon alloys, which are predominantly used for cylinder crankcases, are unsuitable for the tribological loads of the piston/piston ring/cylinder bearing surface system, because of an insufficient level of the wear-resistant silicon phase. Hypereutectic alloys, e.g. the alloy AlSi
7
Cu
4
Mg have a sufficient number of silicon crystallites. This hard, wear-resistant microstructure constituent is raised with respect to the matrix formed of an aluminum mixed crystal by chemical and/or mechanical processing stages and forms a required load-bearing surface component. However, drawbacks are the castability, which is low compared to the hypoeutectic and almost eutectic alloys, poor machinability and the high costs of this alloy.
One possible way of avoiding these drawbacks is to cast in sleeves or liners made from a wear-resistant material, such as for example gray cast iron and hypereutectic aluminum alloys. However, a problem in this case is the join between the sleeve and the surrounding casting, because the join is achieved merely by mechanical meshing or interlocking. When using a porous ceramic liner material, it is possible to infiltrate the liner material during the casting process and thus to obtain a material-to-material bond. This requires a slow filling of the casting mold and the use of high pressure, which considerably reduces the economic efficiency of the process.
Alternatively, hypoeutectic and almost eutectic alloys of electrodeposition coatings are applied directly onto the cylinder bearing surfaces. However, this is expensive and these coatings cannot sufficiently withstand tribochemical loads. A further alternative are thermally sprayed layers, which are likewise applied directly to the cylinder bearing surfaces. However, the adhesive strength of these layers is insufficient, since they are joined only by a micromechanical interlocking.
Therefore, it has already been proposed to carry out the surface modifications of remelting, alloying, dispersing and coating by using a laser, as is disclosed, for example, in Published, Non-Prosecuted German Patent Application No. DE 196 43 029 A1. In this case, it is necessary to sufficiently dissipate the energy which is introduced into the crankcase or the cylinder bearing surfaces by the laser beams. The dissipation of energy is necessary because an excessively high input of heat with high-energy laser beams may lead to undesirable changes to the microstructure in the crankcase. For this purpose, Published, Non-Prosecuted German Patent Application No. DE 196 43 029 A1 has already proposed that the component surface be cooled via cooling-water channels of the crankcase.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a process and a configuration for producing a wear-resistant surface on a component which overcome the above-mentioned disadvantages of the heretofore-known processes and configurations of this general type and which allow components to be coated even with high-energy coating devices, such as high-performance lasers, without causing heat-related changes to the material of the component.
With the foregoing and other objects in view there is provided, in accordance with the invention, a process for producing a wear-resistant surface on a component, the process includes the steps of:
providing a component formed of an AlSi alloy;
forming a wear-resistant surface on the component by using a thermal spraying or a laser beam treatment; and
bringing at least one thermally conductive device into a thermally conductive contact with the component such that the at least one thermally conductive device touches the component during the step of forming the wear-resistant surface; and
actively cooling the at least one thermally conductive device.
In other words, a process for producing wear-resistant surfaces on components made from an AlSi alloy is provided, wherein the wear-resistant surfaces are applied by thermal spraying or a laser beam, wherein, during the production of the wear-resistant surface, at least one thermally conductive device is brought into a thermally conductive contact with the component, and wherein this thermally conductive device is actively cooled.
The above-defined process has the advantage that a good dissipation of heat in combination with an increased cooling capacity is available during the coating operation, so that in particular a laser alloying and a laser coating can be carried out without the risk of a heat-related change in the structure of the material of the crankcase. This allows to carry out a coating at even higher energies, so that, for example, a greater depth of penetration of the coating material into the material of the component, a better join or connection between the coating and the material of the component and/or a greater layer thickness are achieved.
To further improve properties of the coating that is applied, after the formation of the wear-resistant surface in the form of a thermally sprayed layer, this layer is additionally treated with a laser beam. In particular, the layer is remelted with a laser beam.
As explained, the wear-resistant surface may be applied through the use of a thermal spraying, in particular a flame spraying, a plasma spraying or a HV (high velocity) spraying, or through the use of a laser beam.
According to a preferred mode of the invention, a remelting, alloying, dispersing and/or coating is carried out through the use of a laser beam or by thermal spraying.
The component, whose surface is to be treated, is for example a crankcase of a reciprocating internal combustion engine. The coating is to be carried out on cylinder bearing surfaces of cylinders of the crankcase. In this case, according to a preferred mode of the invention, during the production of the wear-resistant surface, a water space or water chamber of the crankcase has a cooling medium, in particular gas, nitrogen or a cooling liquid, flowing through it.
According to another mode of the invention, the thermally conductive device or heat-conducting device includes at least one cooling plate with passages for a cooling medium. The at least one cooling plate is put against the crankcase on at least one side on which open ends of the cylinders are situated.
According to yet another mode of the invention, the thermally conductive device includes at least one cooling mandrel which is formed such that it corresponds to the cross section of the cylinder and which is brought into contact with the cylinder bearing surface. The at least one cooling mandrel follows a coating zone on the cylinder bearing surface in an axial direction of the cylinder and/or trails the coating zone.
According to a further mode of the invention, the thermally conductive device includes a cooling-medium tank, into which the crankcase is dipped during the production of the wear-resistant surface, in such a manner that a cooling-medium level in the cylinder remains below a coating zone as seen in the direction of the force of gravity. In this case, an immersion depth, i.e. a depth to which the crankcase is dipped into the cooling-medium tank, is controlled in such a manner that a constant given distance is maintained between the coating zone and the cooling-medium level.
According to yet a further mode of the invention, the active cooling of the thermally conductive device is carried out by using a gas, nitrogen and/or a cooling liquid.
According to an advantageous mode of the invention, a honing operation is performed subsequent to the coating process according to the invention, in order to smooth the coated surface.
With the objects of the invention in view there is also provided, a configuration for producing a wear-resistant surface on a component, including:
a thermally conductive
Färber Klaus
Heider Thomas
Heinemann Rolf
Beck Manfred
Doerrler William C.
Volkswagen AG
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