Method for coating an inner surface of a cylinder liner or a cylinder and coating formed in this way

Abstract

The invention relates to methods for coating an inner surface of a cylinder liner or cylinder made of a light metal to create an inner running surface for a piston of an internal combustion engine, and to coatings formed in this way. The methods and coatings are characterized in particular by the creation of a high-density layer with improved sliding and emergency running properties. For this purpose, in a first step, recesses with undercuts are introduced into the cylinder liner or cylinder. In a second step, the inner surface of the cylinder liner or cylinder is thermally coated with the compounds to form positive connections in the recesses and a connecting layer on the inner surface of the cylinder liner or cylinder. In a third step, material is applied to the connecting layer by means of laser deposition welding.In a fourth step, the laser-deposited layer is subjected to machining and / or surface-forming to form an inner running surface for the cylinder liner or cylinder. Finally, in a fifth step, recesses are introduced into the laser-deposited layer to serve as lubricant reservoirs.

Description

[0001] The invention relates to a method for coating an inner surface of a cylinder liner or a cylinder made of a light metal to produce an inner running surface for a piston of an internal combustion engine and to a coating formed in this way.

[0002] EP 1 645 652 A1 discloses a method for producing a layer system. For this purpose, at least one intermediate layer and one cover layer are applied to a substrate in such a way that the outer layer or the intermediate layer is only partially present on the substrate or on the intermediate layer due to a recess. Anchoring means are created in the recesses. The recesses are created and the respective layer is applied using a laser or a plasma torch. The anchoring means are designed as separate and continuous or internal anchoring means.

[0003] A plasma spraying device and a coating method are known from WO 2013 / 083 672 A1. The device is preferably designed for coating convex surfaces, such as the inner surfaces of bores or pipes. A characteristic feature of this device is that it comprises both a plasma torch for thermal spraying and a so-called treatment device. The treatment device can be another plasma torch or a laser. Coating material can also be fed into the treatment beam to apply an additional layer by laser deposition. Anchoring devices are not provided.

[0004] The publication DE 10 2016 210 507 A1 describes a method for producing a sliding surface on a machine element, as well as a machine element. Before applying a coating or coatings, the base material is treated with a laser, structuring the surface. This is followed by a layer buildup using PVD and / or PACDV and / or CVD. After coating, a profiled sliding layer is created.

[0005] From the publication DE 10 2018 202 540 A1, an engine block of an internal combustion engine with optimized thermal conduction properties is known, which has a cylindrical piston track with a longitudinal axis surrounded by the engine block. For this purpose, a first and a second inner, circumferential coating are each produced on a raw piston track using a thermal process. These coatings are then dimensionally finished. The layers partially overlap in the direction of the longitudinal axis. The second coating can be produced using a thermal spray process and then the first coating using laser deposition welding. These coatings can partially overlap in the longitudinal axis. The overlap thus comprises the two coatings. Dimensional finishing can be achieved by honing, whereby the resulting surface has favorable lubricant-carrying and lubricant-retaining properties.

[0006] The publication US 2010 / 0 326 270 A1 describes a method for roughening metal surfaces to improve the adhesion of thermally sprayed coatings. For this purpose, uniform grooves, particularly rectangular and / or trapezoidal grooves, are introduced into the metal surface. These are then deformed by turning, drilling, milling, or rolling to form undercuts. This roughens the surface of a cylinder block.

[0007] US Pat. No. 8,286,468 B2 covers, among other things, cylinder liners with a thermally sprayed coating on the inner surfaces of the cylinder bores. A drilling device is used, among other things, to roughen the base material surface. The drill rod of this drilling device is simultaneously rotated and moved downward to form a screw thread along the cylindrical inner surface. The surface of the rib section is finely serrated. A layer is then thermally sprayed onto the resulting surface.

[0008] EP 3 314 033 B1 describes an iron-based alloy for the production of thermally applied wear-resistant coatings, which are applied thermally sprayed or by laser powder deposition welding. The respective coating is applied as such as a wear-resistant coating.

[0009] DE 102 57 213 B4 discloses a process for reconditioning a cylinder bore of a crankcase. This involves removing the base material, applying a coating using a build-up welding process, and then removing this coating until the original diameter of a new cylinder bore is restored. The process involves repairing a cylinder bore.

[0010] The invention specified in claims 1 and 5 is based on the object of realizing a high-density layer with improved sliding and emergency running properties as an inner running surface of a cylinder liner or a cylinder made of a light metal.

[0011] This problem is solved by the features listed in patent claims 1 and 5.

[0012] The method for coating an inner surface of a cylinder liner or a cylinder made of a light metal to create an inner running surface for a piston of an internal combustion engine and the coating thus formed is characterized in particular by the creation of a high-density layer with improved sliding and emergency running properties of cylinder liners or cylinders made of a light metal.

[0013] For this purpose, in a first step, trapezoidal depressions with undercuts are introduced into the cylinder liner or the cylinder. The trapezoidal depressions are introduced in such a way that the cylinder liner or the cylinder has trapezoidal depressions that run radially and / or radially helically and are arranged at a distance from one another in some regions. In a second step, the inner surface of the cylinder liner or the cylinder is thermally coated with the compounds made of an iron-based material to form positive-locking connections in the trapezoidal depressions and a connecting layer on the inner surface of the cylinder liner or the cylinder, so that the connections in the depressions and the connecting layer are formed in a one-piece, positive-locking manner. In a third step, an iron-based layer is applied to the connecting layer by means of laser deposition welding.In a fourth step, the laser-deposited layer is subjected to machining and / or surface forming to form an inner running surface for the cylinder liner or cylinder. Finally, in a fifth step, recesses are introduced into the laser-deposited layer for use as lubricant reservoirs. The geometry, number, and distribution of these recesses are adapted to the property profile of the combustion engine.

[0014] A thermally coated bonding layer is arranged on the inner surface of the cylinder liner made of a light metal, in particular an aluminum alloy, or of the cylinder made of a light metal, in particular an aluminum alloy, to form the inner running surface for a piston of an internal combustion engine. This bonding layer is further anchored in recesses with undercuts. The laser-deposited layer is located on the bonding layer, the surface of which forms the inner running surface of the cylinder liner or cylinder through machining and / or surface-forming post-processing. Furthermore, the laser-deposited layer has recesses that serve as a reservoir for a lubricant.

[0015] The process for coating the inner surface of a cylinder liner or cylinder advantageously combines thermal coating and laser cladding. Laser cladding advantageously applies a high-density layer that forms the inner running surface. This allows a cylinder liner or cylinder made of light metal to be used in an internal combustion engine; the layer is wear-resistant and features improved sliding and emergency running properties. The combination of the two coating processes creates the possibility of indirectly applying a layer to light metals using laser cladding. To create tribologically favorable properties for this layer, post-processing is carried out using processes with geometrically defined cutting edges and / or surface-forming machining.Due to its material properties, the coating can be reworked quickly, reproducibly, and with low wear, using processes with a geometrically defined cutting edge without the need for cooling lubricant. This creates a tribologically stable coating. Due to the coating's low inherent porosity, the coating is provided with depressions to create the necessary retention volume for a lubricant, thus optimizing hydrodynamic lubrication. The depressions can be introduced according to the forces acting on the piston. This allows the number density at the upper and lower inflection points to be varied. This enables a new lubrication concept.

[0016] Advantageous embodiments of the invention are specified in the following developments, which further develop the method for coating an inner surface of a cylinder liner or a cylinder made of a light metal to realize an inner running surface for a piston of an internal combustion engine and the cylinder liner or the cylinder made of a light metal with an inner running surface for a piston of an internal combustion engine, each individually or in a combination.

[0017] The trapezoidal recesses can be created using a machining process, electromagnetic waves, or electron beams. Machining processes can include turning, milling, or boring. Special tools, such as those with diamond-tipped cutting inserts, can be used for this purpose. Electromagnetic waves are, in particular, the electromagnetic waves of a laser.

[0018] The positive connections in the trapezoidal recesses and the bonding layer can advantageously be formed by plasma spraying or wire arc spraying. Atmospheric plasma spraying can be used for this purpose, in particular.

[0019] The positive connections, the connecting layer and the laser-deposited layer can be made of the same material.

[0020] An embodiment of the invention is shown in principle in the drawing and is described in more detail below.

[0021] It shows: Fig. 1 a section of a coating with a bonding layer and a laser-deposited layer on a cylinder liner or a cylinder for forming an inner running surface for a piston of an internal combustion engine.

[0022] In the following exemplary embodiment, a method for coating an inner surface of a cylinder liner 1 or a cylinder made of a light metal for realizing an inner running surface for a piston of an internal combustion engine and such a coating are explained in more detail together.

[0023] A layer arrangement for a cylinder liner 1 or a cylinder for forming the inner running surface for a piston of an engine essentially consists of a connecting layer 2 with recesses and a laser-deposited layer 3.

[0024] The Fig. 1 shows a section of a coating with a connecting layer 2 and a laser-deposited layer 3 on a cylinder liner 1 or a cylinder for forming an inner running surface for a piston of an internal combustion engine in a schematic representation.

[0025] In a first step, recesses with undercuts are introduced into the cylinder liner 1 or the cylinder made of a light metal. The light metal is, for example, an aluminum material or consists of an aluminum alloy. The recesses have a trapezoidal cross-section for a dovetail joint. The trapezoidal recesses are introduced in such a way that at least the cylinder liner 1 or the cylinder are partially circumferential and spaced apart trapezoidal recesses are created and thus present. The trapezoidal recesses are thus formed in a trench-like shape.

[0026] In a second step, the inner surface of the cylinder liner 1 or the cylinder is thermally coated to form connections in the trapezoidal recesses and a bonding layer 2 connected thereto. The connections of the trapezoidal recesses and the bonding layer 2 consist, in particular, of an iron-based material, which is applied particle by particle by plasma spraying.

[0027] In a third step, material is deposited on the connecting layer 2 by laser deposition welding. For this purpose, an iron-based material is applied. The resulting laser-deposited layer 3 is subsequently machined and / or surface-formed in a fourth step.

[0028] Finally, in a fifth step, this laser-deposited layer 3 is provided with recesses 4. For this purpose, a laser drilling process is used, so that the laser-deposited layer 3 has blind holes for receiving a lubricant as a lubricant reservoir.

[0029] The thermally coated bonding layer 2 is thus arranged on the inner surface of the cylinder liner 1 made of light metal or of the cylinder made of light metal. This bonding layer is anchored by connections in the trapezoidal recesses with undercuts in the cylinder liner 1 or the cylinder. The connections in the trapezoidal recesses and the bonding layer 2 are thus formed as a single piece. The laser-deposited layer 3 is located on the bonding layer 2, the surface of which forms the inner running surface of the cylinder liner 1 or the cylinder through machining and / or surface-forming post-processing. The laser-deposited layer 3 also has recesses 4, which can be blind holes created by laser drilling. These are introduced in a targeted and patterned manner. This structuring is primarily done to increase the retention volume for the lubricant.The geometry, number, and distribution of these recesses 4 of the laser-deposited layer 3 can be individually adapted to the property profile of the combustion engine. This allows the retention volume to be varied at different positions of the piston, particularly at the turning points of the piston's movement.

Claims

[1] Method for coating an inner surface of a cylinder liner (1) or a cylinder made of a light metal to produce an inner running surface for a piston of an internal combustion engine, comprising the following steps: - introducing trapezoidal recesses with undercuts into the cylinder liner (1) or the cylinder, wherein the trapezoidal recesses are introduced in such a way that the cylinder liner (1) or the cylinder has trapezoidal recesses which extend radially and / or radially helically in regions and are arranged at a distance from one another, - thermally coating the inner surface of the cylinder liner (1) or the cylinder to form positive connections in the trapezoidal recesses and a connecting layer (2) on the inner surface of the cylinder liner (1) or the cylinder with the connections made of an iron-based material, so that the connections in the trapezoidal recesses and the connecting layer (2) are formed in one piece with a positive fit, - material application of an iron base layer to the connecting layer (2) by means of laser deposition welding, - machining and / or surface-forming of the laser-deposited layer (3) to form the inner running surface of the cylinder liner (1) or the cylinder and - introducing depressions (4) into the laser-deposited layer (3) for use as a lubricant reservoir, so that the geometry, number and distribution of these depressions (4) introduced into the laser-deposited layer (3) are adapted to a property profile of the internal combustion engine. [2] Method according to claim 1, characterized by that the trapezoidal recesses are created by means of a machining process, electromagnetic waves or electron beams. [3] Method according to claim 1, characterized by that the positive connections in the trapezoidal recesses and the connecting layer (2) are formed by means of plasma spraying or wire arc spraying. [4] Method according to claim 1, characterized by that the positive connections in the trapezoidal recesses, the connecting layer (2) and the laser-deposited layer (3) are made of the same material. [5] Cylinder liner (1) or cylinder made of a light metal with an inner running surface for a piston of an internal combustion engine produced by the method according to claim 1.

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