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, comprising: at least one bore with an inner shell formed from a base material, a layer system at least partially provided on the base material in a region of the bore to form a first boundary surface between the base material and the layer system, wherein the layer system comprises a thermally sprayed layer that at least partially forms a shell surface of the bore to act as a functional layer, wherein the layer system further comprises an adhesive layer including a boundary surface material, in a region of the first boundary surface, that includes molybdenum and at least one further element, the boundary surface material being bonded to the inner shell of the base material, and the inner shell having a surface roughness from the manufacturing of the bore but not profiled to activate the inner shell, by a chemical bond, and wherein the boundary surface material differs from a material of the functional layer in at least one of composition or structure.

2. The cylinder according to claim 1, wherein the layer system is configured for the bonding of the layer system on the bore material.

3. The cylinder according to claim 2, wherein the layer system are configured to at least one of form the chemical bond or to produce a boundary surfaces roughness.

4. The cylinder according to claim 1, wherein the chemical bond between the boundary surface material to the base material is realized by at least one of ionic bonds or covalent bonds.

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

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

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

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

9. The cylinder according to claim 3, wherein the at least one of the chemical bonds or the boundary surface roughnesses are formed by at least one of applying the boundary surface material or a gradual transition from the boundary surface material to a material of the functional layer.

10. A method of manufacturing a cylinder for a piston-type internal combustion engine, the method comprising: forming a bore in a base material, the bore having an inner shell with a surface roughness resulting from manufacture of the bore, applying a layer system to the inner shell of the bore, the layer system comprising an adhesive layer including a boundary surface material at a boundary surface to the base material and a thermally sprayed layer forming a functional layer as a surface of the cylinder, wherein the surface roughness of the inner shell from the manufacturing of the bore is not profiled to activate the surface of the bore for applying the layer system, wherein the boundary surface material comprises molybdenum and at least one further element to form a chemical bond with the base material, and wherein the boundary surface material and a material of the thermally sprayed functional layer differ chemically in at least one of composition or structure.

11. The method according to claim 10, wherein a 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 at least one of porosity, or roughness or columnarity.

12. The method according to claim 10, wherein the layer system is applied completely by thermal spraying.

13. The method according to claim 10, wherein the layer system is formed at least partially as a gradient layer in a direction of layer thickness.

14. The method according to claim 13, wherein, a transition from the boundary surface material to a material of the functional layer is formed as a gradient.

15. A method of manufacturing an engine, wherein the method comprises the manufacturing a cylinder according to claim 10.

16. The method according to claim 10, further comprising forming a second boundary surface on the boundary surface material for bonding with the functional layer, wherein the second boundary surface comprises at least one of a porosity, roughness or columnarity for mechanical activation.

Description

(1) The invention is now represented in detail with reference to an example and with the help of the figures.

(2) FIG. 1 shows the state of the art up to now

(3) FIG. 2 shows a first embodiment of the present invention,

(4) FIG. 3 shows a second embodiment of the present invention.

(5) 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.

(6) 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.

(7) 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.