DE10163970A1 - Production of fluid-lubricated light metal cylinder surfaces of reciprocating machine comprises forming harder sites by changing the intermetallic structure of the base material - Google Patents

Abstract

Production of fluid-lubricated light metal cylinder surfaces of reciprocating machine comprises forming harder sites (13) by changing the intermetallic structure of the base material (21). An Independent claim is also included for the cylinder surface produced. Preferred Features: The harder sites are produced by heating the base material using a laser beam and rapidly cooling to form a recess. An alloy of additional material is produced in the base material to form the intermetallic phase. The additional material is made from copper, nickel, iron, silicon, preferably titanium.

Description

The invention relates to a method for producing low-wear Workpiece surfaces, especially of fluid-lubricated light metal Cylinder surfaces of piston engines and machines with an im essentially smooth surface and such a low-wear Workpiece surface. In it are singularly distributed across the surface a base material provided harder places, if necessary project over the base material.

The design of the surface of piston races, especially of Internal combustion engines is one of the key points of the Engine development. It is largely determinative of wear behavior and thus the service life of the engine, its friction and thus the Performance and especially the oil consumption. Through the so-called Plateau honing has made considerable progress. there a roughly honed surface is honed so that between the deeper grooves, which serve to keep the oil, relatively smooth plateaus be created, the low wear and the energy-saving Enable run, as well as the running-in behavior of the engine and the Improve oil consumption.

Attempts have also been made to use piston races To process laser beam, which is flat on the surface to be processed is directed. This is said to be the case with cylinder blocks made of cast iron Honing covered slats to create emergency running properties exposed (DE 42 17 530 A1). It has also become known Machining workpiece surfaces by means of laser beam in order to To produce grooves / perforated structures (DE 43 16 012 C2).

Cylinder surfaces, which are made of light metals, are in their Wear resistance improved by z. B. from hypereutectic Aluminum-silicon alloys are manufactured in which the emerging silicon crystals in the softer base material are embedded. These crystals are made by different methods exposed so that they are slightly above the surface of the base material project, e.g. B. by brushing (EP 0 348 608 (KADIA)). They are too other methods for exposing these silicon crystals in Materials such as ALUSIL, DURALCAN or LOCASIL (brand names) become known, for example by honing or etching. This is in the article "Modern light metal materials for engine construction and their finishing by honing "by Josef Schmid in MTZ Motortechnische Zeitschrift, Issue 4, 1998, Friedrich Vieweg & Sohn Verlagsgesellschaft mbH, Wiesbaden.

Task and solution

The object of the invention is to provide a cylinder tread that a has improved wear behavior.

This object is achieved according to the invention in that the harder places through targeted changes to the intermetallic structure of the base material are generated. The increase in Hardness against the base material should be measured in Vickers order more the factor 1.5, preferably 3, can be increased.

This can be done by making the harder parts through selective heating of the base material, e.g. B. by a laser beam, be generated. These places then cool down relatively quickly, so that they produce selective hardening.

In the applicant's German patent application 101 31 703 there is a Described method with which by means of a laser beam z. B. annular holes can be created in such a workpiece surface, a "stamp" remains in the middle. By appropriate choice The temperatures and materials can also be affected by the Evaporating the material resulting ring grooves around a hardened Area.

With selective heating, melting can occur, so that the hardening takes place by cooling from the melt.

It is particularly preferred that the points of greater hardness are used by means of a Additional material is generated, which is applied to the base material and an intermetallic phase with brief heating forms the base material, for example by alloying the Additional material in the base material.

Again, several methods are possible for this, namely the one Base material, for example by screen printing, pad printing or the like to apply the areas to be hardened selectively and then the whole Workpiece surface, for example with a surface covering Laser beam to heat or to form the intermetallic phase to apply the additional material to the workpiece surface over a large area and then only carry out the heating selectively. in the In connection with the invention, the term "punctiform" is intended to mean that it are relatively small areas, but not necessarily must be present as a "round point", but have any shape can, for example also ring structures, stars or the like. The Places created in this way should, however, be clear from the rest of the material be delimited and distributed singularly on the workpiece surface, d. that is, the individual points do not directly adjoin one another, but rather individually at a considerable distance from each other. The Distribution can be stochastic, i.e. H. to be arbitrary.

The additional material is usually applied in powder form for example, is applied as a paste and can preferably be in the form of metal hydrides to prevent oxidation respectively. Metals such as copper, nickel, iron, Silicon can be used. However, titanium is preferred because of the better corrosion resistance in connection with a base material based on aluminum or magnesium. With some materials it is advisable to heat under protective gas in order to To avoid oxidation processes.

Through the formation of hard intermetallic phases in the form of a Alloy in the base material creates a solid metallic Connection there. The conversion or alloy zone should be in the Reach in the base material and have a minimum thickness of 2 µm. But it can also be considerably thicker and up to one millimeter in hand in the basic material.

The hardened areas can be exposed and as Wear-resistant supporting structure can be used when the base material is around is reset around these places, for example by mechanical or chemical removal, such as honing, brushing, etching or a Blasting, e.g. B. with hard particles or the like. Excess, not intermetallic with the base material Additional material that is particularly soft compared to the hard areas, is also removed. When you remove it, the harder Make smoothing at the same time, for example, when honing used for this.

These and other features go beyond the claims from the description and the drawings, the individual Features each individually or in groups in the form of Sub-combinations in one embodiment of the invention and on other areas to be realized and beneficial as well can represent protective designs for which protection is claimed here becomes. Embodiments of the invention are in the drawings shown and are explained in more detail below.

Brief description of the drawings

Embodiments of the invention are shown in the drawing and are explained below. Show it:

Fig. 1 is a schematic perspective plan view of a work surface with respect to the base material harder sites,

Fig. 2 is a point in a version with an annular groove in high magnification,

Fig. 3 shows the application of an additional material on the base material in schematic detail section,

Fig. 4 shows the workpiece of FIG. 3 after formation of the intermetallic compound,

Fig. 5 is a Fig. Representation corresponding 3 with continuous application of an additional material,

Fig. 6 shows the workpiece of Fig. 5 after formation of the intermetallic phases and

Fig. 7 shows the workpiece of FIG. 5 and 6 after an etching treatment.

Fig. 1 shows enlarged a section of a workpiece 11, such as a like of light metal or light metal alloys, such as aluminum, magnesium o.. Existing working cylinder of a piston engine such as a gasoline or diesel engine. The surface 12 of the workpiece 11 which forms the piston running surface is machined by conventional machining processes, such as honing, to a very high surface quality and a low surface roughness, e.g. B. to a surface roughness between 0.5 microns and 4 microns, preferably at 2 microns.

Stochastic, ie irregularly distributed, points 13 of greater hardness are contained in this surface 12 . These points can be essentially circular, but can also have other shapes, for example include elongated, ring-shaped or star-shaped structures, etc. They are provided singularly on the surface, ie spaced apart from one another. Your dimensions, e.g. B. at a round point of diameter, are relatively small and can preferably be between 2 microns and 1 mm, particularly preferably between 5 microns and 200 microns.

The average distance d between the points 13 should in any case be greater than their dimensions a. It also results from the preferred area proportion of the surfaces of the points 13 , compared to the remaining surface 12 of 5% to 50%, in particular 10% to 30%.

Due to the manufacturing process described below, the locations are not sharply delimited, but rather pass with a transition region into the base material 21 forming the largest part of the surface 12 .

The harder points 13 are generated by treating the surface 12 of the base material 21 selectively with a laser beam which essentially corresponds to the size a of the points 13 . As a result, the material is heated up, preferably melted, but in FIG. 1 without evaporating. Due to the small size of the spots, their distance from each other, the heating only on the surface, which ensures a relatively small penetration depth, and the good thermal conductivity of the base material, these spots cool very quickly after the laser beam is switched off, so that a change in the intermetallic Structure of the base material is generated, which leads to a greater hardness than that of the base material surface. Due to the small size and isolation of the spots, however, possible distortions, surface changes and possibly greater brittleness of the hardened material play during hardening. B. could lead to cracks, no role.

When it comes to the material, make sure that hardenable light metal alloys, including titanium, are used. A pulsed laser can be used to generate the laser beam, the beam of which is set to the desired size a of the positions and which is guided over the workpiece surface 12 according to a predetermined program, for example using a random generator. However, a uniform arrangement of the points 13 is also possible.

Fig. 2 shows in a very large enlargement a hardening point 13 a, which is generated by means of a defocused laser. The laser beam has a tubular intensity distribution, so that when it strikes the surface 12 by evaporation, it creates an annular groove 14 , in the center of which a "stamp" 15 which is essentially at the level of the surface 12 remains. This ring channel 14 , which can also be referred to as a ring crater, ensures good oil maintenance. In the periphery around the annular groove 14 , zones 16 are formed both on the outside and on the inside, ie on the "stamp", which, when using a hardenable base material 21, have a greater hardness than the base material 21 which surrounds them or from them is surrounded. However, care should be taken to ensure that the largest dimensions of the areas or zones of greater hardness do not become too large, in particular in the case of line structures, because there is then a risk of cracking.

After the hard spots 13 have been formed , they are exposed by mechanical or chemical treatment, ie the remaining surface 12 is removed somewhat. This is preferably carried out by honing, which removes more from the softer base material 21 than from the harder points 13 due to the procedure and / or tool properties. However, these are smoothed so that, in their entirety, they form a relatively smooth and hard supporting structure which works with a counter surface sliding on it, for example a piston or its piston rings, in a low-wear manner. The slightly recessed sections of the surface 12 ensure that lubricant is held well. The corresponding workpiece surfaces are therefore particularly intended for fluid-lubricated applications.

Such ring channel structures are in the German patent application 101 31 703 dated June 29, 2001 by the applicant. These are referred to for the details.

During remained unchanged in the embodiments according to FIGS. 1 and 2 the material in its composition, and only the intermetallic structure has been changed by the heat treatment, the compositions of the materials is changed in the embodiments described with reference to FIGS. 3 to 7 ,

FIGS. 3 and 4 shows an embodiment in which onto the surface 12 of the workpiece 11 by means of screen printing, pad printing, inkjet printing o. The like. Additive material 18 in the form of later forming therefrom bodies 13 is applied. The additional material is an intermetallic compound, for example an alloy, incoming material with the base material 21 of the workpiece 11 , that is to say in the case of light metals, for example copper, nickel, iron, silicon etc. If the base material does not itself consist of titanium, it is titanium a preferred filler material. This additional material is applied in the form of a paste, which may contain the material, for example, as a powder, but preferably in the form of a corresponding metal hydride.

After the selective application of the additional material 18 , the entire workpiece surface 12 with a surface laser, z. B. (cw laser; continons wave, ie not pulsed) heated. This can be, for example, a CO ₂ laser, which heats the entire surface in a very short time with very high power, so that at least the points moved with additional material are melted. Depending on the reflection or absorption characteristics of the additional material and the remaining surface 12 (base material), either only the additional material can be melted or the entire surface. In the latter case, a certain, albeit less, hardening also takes place on this surface because the cooling does not take place as quickly due to the large area of the heating. The base material 21 can also be selected such that it cannot be hardened to the same extent by heat.

At points 13 , however, the base material 21 forms an intermetallic compound with the additional material 18 . Fig. 4 shows that this intermetallic phase extends into the base material over a certain depth. Depending on the degree of melting and the materials used, this conversion or alloy zone can have very different thicknesses. You should have a minimum thickness of 2 microns, but can also be much larger, z. B. up to 1 mm thick. The thickness is preferably 5 μm to 200 μm. The thickness is 5 µm to 200 µm. The corresponding material pairings are selected so that the intermetallic phase, together with the rapid heating and cooling, results in greater hardness at points 13 .

In the subsequent ablation processing, as described on the occasion of FIGS. 1 and 2, the remaining surface 12 is displaced somewhat by abrasion (see dash-dotted line 12 a in FIG. 4), so that the locations 13 are exposed and thus the desired one Support structure or matrix is created. The surface 20 at the points 13 is also improved in its shape and surface quality, and deburring takes place at the edge regions. Due to the greater hardness, however, the positions 13 remain as protruding "islands".

The printing with the additional material 18 ( FIG. 3) can take place in any layer thicknesses which can be considerably thicker than the later intermetallic phase. The type of printing creates practically unlimited possibilities for patterns of the supporting point structure adapted to the application. In the case of brief heating, the additional material which makes it printable, e.g. B. pasty components of the printing material.

With some additional materials or basic materials it can become necessary when heating in a protective gas atmosphere work to remove unwanted oxidation phenomena that result in a Avoid burning the additional material. at Use of metal hydrides, for example titanium hydride, can do this but may be avoided under certain circumstances. The hydride does not oxidize that way strong and is self-reducing. It deprives due to the reducing Effect from the aluminum surface oxygen and promotes the alloying connection there. There is also such a printed surface can be stored longer without there already being signs of oxidation are to be feared.

The Figs. 5 to 7 schematically show a variant of the application. There, the surface 12 is coated over the entire area with the additional material 18 , for example also in the form of an applied paste. It is then produced with a laser, similar to that in FIG. 1, at points 13 for a brief heating / melting, which causes the intermetallic phases 21 according to FIG. 4 ( FIG. 6). In the subsequent removal, not only is the remaining, unused additional material 18 removed, but also the surface 12 is set back relative to the surface 20 of the locations 13 (see 12a in FIG. 7). This reset ( FIG. 7) can be between 0.1 μm and 2 μm, preferably 0.2 μm to 1 μm. This dimension also depends on the dimensions of the positions 13 .

Claims (20)

1. Process for the production of low-wear workpiece surfaces, in particular fluid-lubricated light metal cylinder surfaces of piston power and work machines with an essentially smooth surface, in which, over the surface ( 12 ), singularly harder points ( 13 ) are distributed over a base material ( 21 ). are provided, which possibly protrude above the base material ( 21 ), characterized in that the harder points ( 13 ) are generated by changes in the intermetallic structure of the base material ( 21 ) which are aligned with them. 2. The method according to claim 1, characterized in that the points are generated by selective heating of the base material ( 21 ), preferably by a laser beam and subsequent rapid cooling, possibly around a depression ( 14 ) generated by a laser beam. 3. The method according to claim 1, characterized in that the points ( 13 ) are generated by selective melting. 4. The method according to any one of the preceding claims, characterized in that the points ( 13 ) of greater hardness are generated by means of an additional material ( 18 ) which is applied to the base material ( 21 ) and an intermetallic phase ( 22 ) with the by brief heating Base material ( 21 ) forms. 5. The method according to claim 4, characterized in that the additional material is applied to the base material ( 21 ) at points ( 13 ) and the intermetallic phase ( 22 ) by briefly heating the workpiece surface ( 12 ), preferably with a surface-covering and / or - heating laser beam is generated. 6. The method according to claim 4, characterized in that the additional material ( 18 ) is applied over a large area to the surface ( 12 ) and the heating is carried out selectively, preferably with a laser beam. 7. The method according to any one of claims 4 to 6, characterized in that with the formation of the intermetallic phases, an alloying of the additional material ( 18 ) takes place in the base material ( 21 ). 8. The method according to any one of claims 4 to 7, characterized in that the additional material ( 18 ) is copper, nickel, iron, silicon, preferably titanium. 9. The method according to any one of claims 4 to 8, characterized in that the application of the additional material ( 18 ) by screen printing, pad printing, ink jet printing or the like. 10. The method according to any one of claims 4 to 9, characterized in that the application of the additional material ( 18 ) in powder or paste form and / or in the form of metal hydrides. 11. The method according to any one of claims 2 to 10, characterized characterized that the heating takes place under protective gas. 12. The method according to any one of the preceding claims, characterized in that the base material ( 21 ) around the hard spots ( 13 ) is slightly reset, so by mechanical or chemical removal, such as honing, brushing, etching, blasting with hard particles or the like ., Excess material ( 18 ) which is not in intermetallic connection with the base material ( 21 ) may also be removed. 13. The method according to claim 12, characterized in that the harder points ( 13 ) are smoothed during removal. 14. The method according to any one of the preceding claims, characterized in that the locations ( 13 ) have dimensions between 2 µm and 1mm, preferably 5 µm to 200 µm. 15. The method according to any one of the preceding claims, characterized in that the area proportion of the locations ( 13 ) provided on the surface ( 12 ) is 5% to 50%, preferably 10% to 30%, compared to the rest of the surface. 16. The method according to any one of claims 12 to 15, characterized in that the base material ( 21 ) with respect to the points ( 13 ) between 0.1 µm and 2 µm, preferably 0.2 µm to 1 µm, is reset. 17. The method according to any one of the preceding claims, characterized in that the hardness of the points ( 13 ) compared to the base material ( 21 ), when measured according to Vickers, increased by at least 1.5 times, preferably more than 3 times becomes. 18. Low-wear workpiece surface, in particular fluid-lubricated light metal cylinder surface of piston-powered machines and work machines with an essentially smooth surface, in which, over the surface ( 18 ), harder points ( 13 ) are provided compared to a base material ( 21 ), which may protrude above the base material (21), characterized in that the points (13) have a different from the base material (21) intermetallic structure. 19. Workpiece surface according to claim 18, characterized in that the locations ( 13 ) have a different intermetallic composition, preferably a different alloy shape. 20. Workpiece surface according to claim 18 or 19, characterized in that the points ( 13 ) in the base material ( 21 ) reaching into the thickness between 2 and 1000 microns, preferably 5 to 200 microns and / or have a shape adapted to the application, which are preferably self-contained patterns and in particular contain or delimit oil holding depressions.