COATING CYLINDER BORES WITHOUT PRIOR ACTIVATION OF THE SURFACE

Abstract

Cylinder of piston-type internal combustion engine includes at least one bore with inner shell formed from a base material. The base material, in a region of the bore, includes a layer system, and a first boundary surface formed between base material and layer system. Layer system includes at least one thermally sprayed layer forming at least partially a shell surface of the bore and acts there as a functional layer. First boundary surface does not include any profiling applied for mechanical activation of the surface apart from surface roughness resulting from manufacture of the bore. The material of the layer system includes molybdenum and at least one further element in the region of the boundary surface to the base material and is bonded to the base material by a chemical bond. This boundary surface material differs from the material of the functional layer in composition and/or structure.

Claims

1. A cylinder of a piston-type internal combustion engine, wherein the cylinder comprises at least one bore with an inner shell formed from a base material, wherein in the region of the bore the base material is at least partially provided with a layer system and a first boundary surface is thus formed between the base material and the layer system and the layer system comprises at least one thermally sprayed layer and the thermally sprayed layer forms at least partially the shell surface of the bore and can act there as a functional layer and wherein the first boundary surface does not comprise any profiling applied for the activation of the surface apart from the surface roughness resulting from the manufacture of the bore, characterized in that the material of the layer system comprises molybdenum and at least one further element in the region of the boundary surface to the base material, hereinafter referred to as the boundary surface material, and is bonded to the base material by a chemical bond and the boundary surface material differs from the material of the functional layer in its composition and/or structure.

2. A cylinder according to claim 1, characterized in that structural means for the cohesion of the layer system are provided within the layer system.

3. A cylinder according to claim 2, characterized in that the structural means comprise chemical bonds and/or boundary surfaces roughnesses, which have preferably been created by the application process of the boundary surface material and/or by a gradual transition from boundary surface material to the material of the functional layer.

4. A cylinder according to claim 1, characterized in that the chemical bond between the boundary surface material to the base material is realized by ionic bonds and/or by covalent bonds.

5. A cylinder according to claim 1, characterized in that at least one chemical element which corresponds to a chemical element in the base material is present in the boundary surface material.

6. A cylinder according to claim 1, characterized in that the layer system forms at least partially at least one gradient in the chemical composition and/or structural construction over the layer thickness, starting from the first boundary surface and continuing through the functional layer on the shell surface.

7. A cylinder according to claim 1, characterized in that at least one chemical element, which corresponds to a chemical element in the functional layer, is present in the boundary surface material.

8. A method of manufacturing a cylinder for a piston-type internal combustion engine having a bore, the method comprising: providing a cylinder with a bore, wherein the inner shell of the bore is formed from a base material and the surface of which, apart from the surface roughness resulting from the manufacture of the bore, does not comprise any profiling for activating the surface, applying the inner shell of the bore with a layer system, which comprises a boundary surface material at the boundary surface to the base material and wherein at least the layer of the layer system forming the surface of the cylinder bore is thermally sprayed and forms a functional layer, characterized in that the boundary surface material comprises molybdenum and at least one further element and is selected such that it forms a chemical bond with the base material and the layer system is applied in such a way that the boundary surface material and the material of the functional layer differ chemically in the composition and/or the structure.

9. A method according to claim 8, characterized in that the region comprising the boundary surface material between base material and functional layer is produced as a base layer forming a second boundary surface to the functional layer in such a way that the second boundary surface has structures suitable for mechanical activation such as porosity and/or roughness and/or columnarity.

10. A method according to claim 8, characterized in that the layer system is applied completely by means of thermal spraying.

11. A method according to claim 8, characterized in that the layer system is formed at least partially as a gradient layer in the direction of the layer thickness.

12. A method according to claim 11, characterized in that the layer system of the transition from the boundary surface material to the material of the functional layer is formed as a gradient.

13. An engine having a cylinder according to claim 1.

14. A method of manufacturing an engine, characterized in that the method comprises the process steps according to claim 8.

Description

[0047] The invention is now represented in detail with reference to an example and with the help of the figures.

[0048] FIG. 1 shows the state of the art up to now

[0049] FIG. 2 shows a first embodiment of the present invention,

[0050] FIG. 3 shows a second embodiment of the present invention.

[0051] The example refers to the invention according to the first embodiment. The bore of a cylinder is coated, whereby the base material of the cylinder is an aluminum alloy and the bore has a diameter of 85 mm and the bore is 170 mm deep. This bore is to be coated with an iron-based thermally sprayed coating (95% Fe, 1.5% Cr, 1% Mn, 1% C) with a thickness of 200-300 micrometers. Atmospheric plasma spraying (APS) is to be used as the coating method for thermal spraying. In this case, powdery coating material is continuously melted in a plasma under supply of energy and process gases, atomized in liquid form and then applied to the base material of the cylinder wall inside where it solidifies and forms a closed layer. The plasma gun rotates during the melting process so that the inside of the cylinder wall is evenly coated.

[0052] If this layer were simply applied directly to the base material using the method described, it would not adhere sufficiently to the base material. According to the state of the art, the surface of the base material could now be roughened or profiled.

[0053] In contrast, in the present embodiment according to the invention a 5-150 micrometer thick adhesive layer of a mixture of molybdenum and nickel-aluminum powder is applied directly to the base material. This material has the advantage that it forms chemical bonds both with the base material and with the actual layer material. At the boundary surface to the base material, chemical compounds of an ionic nature, for example, are formed, and at the boundary surface of the adhesive layer to the coating material, ionic bonds are also formed and, in addition, mechanical interlocking by the rough spray coating occurs. In doing so, a sufficient adhesion at both boundary surfaces is ensured.