EP1711642B1 - Ferrous layer for a sliding surface, in particular for cylinder running surfaces on engine blocks, applied by means of thermal spraying - Google Patents

Abstract

Some material is first removed. An iron-containing layer is coated onto the sliding surface by thermal-spraying. This layer has an amorphous structure. It contains finely-divided nano-crystalline metal borides and/or metal carbides. Further borides and/or carbides precipitate into the layer, following subsequent heat treatment. An independent claim is included for the corresponding, repaired sliding bearing surface.

Description

The invention relates to an applied by thermal spraying iron-containing layer of a sliding surface, in particular for cylinder surfaces of engine blocks according to the preamble of claim 1 and a method for producing and the use of this layer.

From the WO 03/106718 is a generic iron-containing layer is known, which is applied by thermal spraying and which has an amorphous structure with finely divided, nano-crystalline metal borides and / or metal carbides. Such a layer is well suited as a sliding surface due to the high hardness. For this purpose, the layer is applied in the region of the sliding surfaces on the machine parts to be coated by thermal spraying. The resulting surface of the sprayed-on layer is relatively rough and, in order to serve as a sliding surface, must be smoothed by surface treatment. Such machining preferably takes place by honing, but other machining and non-cutting methods of surface treatment are also possible.

From document US-B1-6258185 is known, applied by thermal spraying iron-containing layer having an amorphous structure with nano-crystalline metal borides and / or metal carbides. The layer is aftertreated by heat input by laser light.

WO 89/10434 discloses a sliding layer provided by, for example, thermal spraying, in which a fine-grained distribution of the constituents in a quasi-amorphous state is produced by a punctiform laser beam. Subsequently, hard particles such as TiC, WC; SiC ... be stored in the layer.

JP-A-05288274 discloses the selective heat input by laser light for limited local hardening of a applied by thermal spraying layer (eg WC).

US-A-4,774,393 discloses the production of lubricating pockets in a lubricating layer by means of concentrated laser light.

Due to the surface treatment, the sprayed-on layer must be partially removed. For this to be possible, compromises between strength and machinability must be found in the formation of the sprayed-on layer, especially with regard to the total production outlay and the associated production costs. As a result, the sliding surface formed does not always have the best possible properties in terms of wear resistance and / or sliding friction, especially in connection with a lubricant, which it might have due to the superior properties of the iron-containing layer.

Accordingly, it is the object of the invention to improve an iron-containing layer so that it has higher wear resistance and / or better sliding friction properties, especially when used as a sliding surface, and can be manufactured as inexpensively.

This object is achieved with the features of claim 1 and 3, respectively.

According to the invention, the iron-containing layer thus comprises further nano-crystalline metal borides and / or metal carbides, which have been produced after application of the iron-containing layer and a subsequent surface treatment by selective heat input into the iron-containing layer.

By after the order of the iron-containing layer and a subsequent surface treatment by selective heat input into the iron-containing layer further nano-crystalline metal borides and / or metal carbides are formed, in selected areas of the sliding surface, for. B. in the highly loaded upper and lower reversal point of a cylinder bore, additional hard areas are generated. The selective heat input also makes it possible to produce small local areas with greater hardness and / or changed surface properties. The extent of the punctual heat input can be substantially less than the entire extent of the sliding surface.

Another advantage is that the surface treatment takes place after the application of the iron-containing layer. Thus, the surface of the iron-containing layer after application can be finished as much as possible, so that the final surface roughness and / or the final layer thickness is achieved. Since the iron-containing layer after application does not yet have to have their final properties, the layer is applied so that a favorable surface treatment, eg. B. in terms of accuracy and / or cost is possible. The subsequent heat input causes a change in the properties of the layer, for. B. greater hardness, better wear behavior and / or better sliding friction in the heat input. The then possibly necessary post-processing of the surface to z. B. remove burrs or to achieve a lower surface roughness, can then be limited to a minimum. As a rule, when heat input, z. B. with laser light, no roughening of Surface detectable. This altogether enables a highly accurate production of a sliding surface with the best possible wear and friction behavior at low production costs.

The surface treatment may be a mechanical fine machining of the iron-containing layer. These are z. As honing, grinding or polishing. These proven methods allow cost-effective and accurate production of the surface of a sliding layer. Thus, the sliding surface can be finished substantially, that is, a subsequent processing after the heat input is no longer necessary or limited to a little post-processing, for. B. to remove burrs formed during heat input.

Finely distributed nanocrystalline metal borides and / or metal carbides are advantageously precipitated from the amorphous structure of the iron-containing layer in the region of the heat input. Thus, the iron-containing layer during application may have a relatively high proportion of crystalline and / or partially crystalline structure. This allows the favorable mechanical processing. The heat input creates additional nanocrystalline metal borides and / or metal carbides, which substantially increases the strength of the iron-containing layer in the region of the heat input.

The iron-containing layer preferably has a hardness of 1000 to 1250 HV 0.05 in the region of the heat input, but the hardness can readily be adjusted by means of appropriate process parameters and material composition in the range between 800 HV 0.05 and 1500 HV 0.05. Such hardness is currently z. B. in carbide tools based on tungsten carbide / cobalt known, and can now be applied over a large area for sliding surfaces. Due to the high hardness, the iron-containing layer is extremely wear-resistant. The metal borides or metal carbides preferably have a size of 60 to 130 nm. Due to the small size, the friction is reduced and the hardness increased.

Advantageously, the selective heat input in the form of geometric figures, regular patterns and / or irregular patterns. These figures or patterns can be made by continuous heat input by passing a point source of heat over the iron-containing layer according to the shape of the figures and patterns. The heat input can also be discontinuous, z. B. to create a dot pattern. By means of these figures and patterns, adjacent areas can be produced on the sliding surfaces, each having different properties.

In a preferred embodiment, the iron-containing layer on erosion, which are caused by the selective heat input. This can be z. B. take place in that material is removed on the surface of the layer by evaporation. In this case, the erosion can again take the form of figures or patterns, as previously described. Such abrasions on sliding surfaces in the form of lubrication pockets, oil collecting grooves, or the like can improve the sliding friction properties.

Finely divided nanocrystalline metal borides and / or metal carbides are preferably precipitated from the amorphous matrix of the iron-containing layer at the edge of the ablation. Thus, the wear resistance of the edge, z. B. a lubricating pocket, substantially increased and it is ensured that even after a long period of operation of the sliding surface, the function of the lubrication pocket, etc. is safely met.

The removal preferably takes the form of local depressions. Such depressions are from the EP1275864 known. The disclosure of this document is incorporated by reference into the disclosure of this application. For example, the recesses have a maximum extent of less than 2 mm. As favorable dimensions for lubricating pockets has been found, when the wells have a maximum length of 2 mm, a maximum width of 70 microns and a maximum depth of 40 microns. This represents a good compromise between tribological properties and production costs of the lubrication pockets. Due to these dimensions, individually or in combination, the optimal function of the recesses is ensured as lubrication pockets of the sliding surface. These dimensions are not meant to be limiting. For certain applications, these dimensions may be larger or smaller. In particular, no specific dimension ratio of the depressions is to be observed. Rather, each of the dimensions length, width and depth can be adapted to the requirements of the respective depression.

The heat input preferably takes place by means of laser light and / or electron beams. These energy sources can deliberately selectively introduce heat or energy into the iron-containing layer in a small area, as is the case, for example. B. is required for the preparation of the wells described above. In addition, these sources of energy in a small space, such. Example, within a cylinder bore of an internal combustion engine or a hydraulic cylinder, are used to produce the inventive iron-containing layer. However, all other suitable energy sources are also usable, which allow the heat input to produce the inventive iron-containing layer.

The embodiment of the invention is not limited to the present examples. It goes without saying that, in particular, the inventive iron-containing layer can be produced in any suitable combination with the method for producing an iron-containing layer, just as, conversely, the inventive method for the production can be used to produce an iron-containing layer.

The inventive iron-containing layer is used in the production of sliding surfaces on machine parts, in particular of connecting rod bearings, crankshaft bearings, piston rings, cylinder surfaces and pistons. In addition to combustion engines, this includes all machines where such machine components are located, eg. B. hydraulic cylinder, gearbox, shaft bearings.

Preferred applications are highly loaded cylinder surfaces of supercharged diesel and gasoline engines. Due to the high mechanical clamping of the Layer with the base material, the coating is particularly suitable for thermal shock claimed motors. Thermal shock occurs when, during cold start, at low ambient temperatures, engines rapidly spin up to maximum speed under load. By the iron-containing layer having an amorphous structure with finely divided, nano-crystalline metal borides and / or metal carbides, the sliding surface is highly resilient, since due to the nano-crystalline precipitations of the metal borides and metal carbides, a layer with extremely high hardness is formed. Furthermore, the borides lead to a very low coefficient of friction, so that this layer also has excellent sliding properties.

A preferred use of the iron-containing layer according to the invention can be carried out in the repair of worn sliding surfaces. The layer has an excellent mechanical bond to the base material due to the amorphous solidification and is thus able to be subsequently applied to. In this case, the order of the layer can be made on a post-processed, cleaned and / or blasted surface. This allows the flexible use of the layer in any repair work on sliding surfaces. Due to the high hardness and strength of the layer also a possible weakening of the base material is compensated by wear or subsequent removal, so that the original strength of the base material can be almost reached again. Application example is the critical web area between cylinder bores of an engine block.

Of course, the layers and methods described herein are not limited to the described embodiments. Rather, the layers and / or methods may find use in any suitable combination of the features described herein.

Fig. 1

einen schematischen Schnitt durch eine eisenhaltige Schicht; und

Fig. 2

ein Mikroskopaufnahme einer eisenhaltigen Schicht im Bereich des Wärmeeintrages.

Further details of the invention can be seen in the figures. Show it:

Fig. 1

a schematic section through an iron-containing layer; and

Fig. 2

a micrograph of an iron-containing layer in the region of the heat input.

FIG. 1 shows a base material 1, on which an iron-containing layer 2 is applied. On the surface 3, the layer 2 is already finished and has reached its final surface finish as a sliding surface. By means of a laser beam 4 is introduced with a high energy density heat in the layer 2 localized, whereby a region 5 of the heat input is formed, which is limited approximately by the boundary line 6. The material of the layer 2 evaporates partially, and there is the recess 7, which preferably extends in the form of a lubricating pocket over the layer 2. If the recess is designed as a lubricating pocket, have proven advantageous dimensions a width b of up to 70 microns and a depth t of up to 40 microns. The longitudinal extent is not shown here, but here a maximum length of not more than 2 mm has been found to be advantageous.

In FIG. 2 a micrograph of an iron-containing layer in the region of the heat input is shown. Such a material structure results, for example, in a region which is in FIG. 1 is marked with the section 8. The applied iron-containing layer 2 in this case has an area 5 of the heat input. This was created by the recess 7 was made by evaporation of material due to heat input by a laser beam, not shown. The region 5 shows, especially in the edge zone 9 of the recess 7, an increased density of finely divided nano-crystalline metal borides 10 and metal carbides 10 compared to the base material of the layer 2, where no heat treatment was carried out. Thus, the edge zone 9 in the region 5 of the heat treatment to an even greater hardness than the non-heat-treated layer 2 itself.

Claims (8)

1. Iron-containing layer (2), applied by means of thermal spraying, for a sliding surface, in particular for cylinder bearing surfaces of engine blocks, wherein the iron-containing layer (2) contains further metallic, metalloid and/or non-metallic elements, and the iron-containing layer (2) has an amorphous structure with finely distributed, nanocrystalline metal borides and/or metal carbides,
   characterized in that
   the iron-containing layer (2) contains further nanocrystalline metal borides (10) and/or metal carbides (10) which have been formed by the punctiform introduction of heat into the iron-containing layer (2) after the application of the iron-containing layer (2) and subsequent surface machining, wherein the iron-containing layer (2) has areas from which material has been removed and which have been formed by the punctiform introduction of heat, the areas from which material has been removed are in the form of local depressions (7), and finely distributed, nanocrystalline metal borides (10) and/or metal carbides (10) are precipitated from the amorphous matrix of the iron-containing layer (2) at the edge (9) of the areas from which material has been removed.
2. Iron-containing layer according to Claim 1,
   characterized in that
   the punctiform introduction of heat is in the form of geometric figures, regular patterns and/or irregular patterns.
3. Process for producing an iron-containing layer (2) for a sliding surface, wherein the iron-containing layer (2) is applied by means of thermal spraying, contains further metallic, metalloid and/or non-metallic elements and has an amorphous structure with finely distributed, nanocrystalline metal borides and/or metal carbides,
   characterized in that
   further nanocrystalline metal borides (10) and/or metal carbides (10) are formed by the punctiform introduction of heat into the iron-containing layer (2) after the application of the iron-containing layer (2) and subsequent surface machining, wherein material in the iron-containing layer (2) is removed by the punctiform introduction of heat, the material in the iron-containing layer (2) is removed in the form of local depressions (7), and finely distributed, nanocrystalline metal borides (10) and/or metal carbides (10) are precipitated from the amorphous structure of the iron-containing layer (2) at the edge (9) of the areas from which material has been removed.
4. Process according to Claim 3,
   characterized in that
   the surface machining is mechanical precision machining of the iron-containing layer (2), in particular honing, grinding or polishing.
5. Process according to either of Claims 3 and 4,
   characterized in that
   the punctiform introduction of heat takes place in the form of geometric figures, regular patterns and/or irregular patterns.
6. Process according to one of Claims 3 to 5,
   characterized in that
   the introduction of heat takes place by means of laser light (4) and/or electron beams.
7. Use of an iron-containing layer according to one of the preceding claims for producing sliding surfaces on machine parts, in particular connecting rod bearings, crankshaft bearings, piston rings, cylinder bearing surfaces and pistons.
8. Use of an iron-containing layer according to Claim 1 or 2 for repairing worn sliding surfaces.

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