SLIDING ELEMENT FOR AN ENGINE COMPRISING SURFACE TREATED METAL PARTICULATE

Abstract

A sliding element for an engine may include a polymer-based overlay layer disposed on a metallic substrate. The polymer-based overlay layer may include a polymer-based matrix and a metal particulate. The metal particulate may be a surface treated metal particulate.

Claims

1. A sliding element for an engine, comprising a polymer-based overlay layer disposed on a metallic substrate, the polymer-based overlay layer including: a polymer-based matrix; and a metal particulate; wherein the metal particulate is a surface treated metal particulate.

2. The sliding element according to claim 1, wherein the surface treated metal particulate imparts a colour to the polymer-based overlay layer.

3. The sliding element according to claim 2, wherein the colour of the polymer-based overlay layer is visually discernible from a colour of the metallic substrate.

4. The sliding element according to claim 3, wherein the colour of the polymer-based overlay layer is predominantly one of gold, orange, and yellow.

5. The sliding element according to claim 1, wherein the polymer-based overlay layer includes about 5 wt % to about 40 wt % of the surface treated metal particulate.

6. The sliding element according to claim 1, wherein the polymer-based overlay layer includes about 24 wt % to about 28 wt % of the surface treated metal particulate.

7. The sliding element according to claim 1, wherein the surface treated metal particulate includes a plurality of aluminium flakes.

8. The sliding element according to claim 7, wherein the plurality of aluminium flakes are surface treated aluminium flakes having a D.sub.50 size of about 5 m to about 30 m along a maximal dimension.

9. The sliding element according to claim 1, wherein the surface treated metal particulate is surface treated via a controlled oxidation process.

10. The sliding element according to claim 1, wherein the surface treated metal particulate includes a metal oxide coating disposed on a surface of the surface treated metal particulate.

11. The sliding element according to claim 10, wherein a metal of the metal oxide coating is different from a metal of the surface treated metal particulate.

12. The sliding element according to claim 10, wherein the metal oxide coating is a coloured transition metal oxide coating.

13. The sliding element according to claim 1 wherein the polymer-based overlay layer has a thickness of about 3 m to about 17 m.

14. An engine comprising a sliding element including a polymer-based overlay layer disposed on a metallic substrate, the polymer-based overlay layer including a polymer-based matrix and a surface treated metal particulate.

15. A method of producing a sliding element for an engine, the method comprising steps of: providing a polymer-based matrix; providing a slurry including a surface treated metal particulate; combining the slurry and the polymer-based matrix to define a polymer-based matrix and slurry combination; applying the polymer-based matrix and slurry combination to a metal substrate; and forming a polymer-based overlay layer via curing the polymer-based matrix and slurry combination, the polymer-based overlay layer including the surface treated metal particulate, wherein the surface treated metal particulate provides the polymer-based overlay layer with a discernibly different colour than a colour of the metallic substrate.

16. The engine according to claim 14, wherein the surface treated metal particulate imparts a colour to the polymer-based overlay layer that is visually discernible from a colour of the metallic substrate.

17. The engine according to claim 14, wherein the surface treated metal particulate includes a plurality of surface treated aluminium flakes.

18. The engine according to claim 14, wherein the surface treated metal particulate includes a metal oxide coating disposed on a surface of the surface treated metal particulate.

19. The engine according to claim 18, wherein a metal of the metal oxide coating is different from a metal of the surface treated metal particulate.

20. The sliding element according to claim 12, wherein a metal of the coloured transition metal oxide coating is different from a metal of the surface treated metal particulate.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0069] The invention will further be described by way of example only with reference to the accompanying drawing, in which:

[0070] FIG. 1 shows a perspective view of a bearing shell according to preferred embodiments of the present invention. The figure provided herein is schematic and not to scale.

DETAILED DESCRIPTION

[0071] FIG. 1 schematically illustrates a sliding bearing 100 (e.g. a sliding engine component) in the form of a hollow semi-cylindrical bearing lining shell (commonly referred to as a half bearing). Many alternative shapes and configurations of the bearing element are envisaged and will be readily apparent to the skilled person. The sliding bearing 100 has a metallic substrate 102 formed from steel. The sliding bearing 100 further comprises a bearing lining layer 104 on the concave inner surface of the metallic substrate 102. Bearing lining layer 104 comprises an aluminium-tin alloy. A polymer-based overlay layer 106 is provided on the substrate 102. The overlay layer 106 is configured to provide a running surface over the lifetime of the sliding bearing 100. The overlay layer 106 is the innermost layer of the half bearing, which is configured to face a cooperating moving part (not shown) in a bearing assembly (e.g. the overlay layer receives a journaled shaft in an assembled bearing, which mutually cooperate, with an intervening film of lubricating oil).

[0072] The overlay layer 106 comprises a polymer-based matrix formed from polyamide imide (PAI). The overlay layer 106 further comprises aluminium flakes which have been coated in a layer of coloured transition metal oxide to form a surface treated metal particulate. Alternatively, a surface of the aluminium flakes may have been subjected to a controlled oxidation process. The aluminium flakes have a D50 size of between about 10 m and about 20 m along the maximal dimension. The overlay layer 106 comprises 26 wt % of the aluminium flakes dispersed evenly throughout the polymer-based matrix. The overlay layer 106 further comprises 10 wt % polytetrafluoroethylene (PTFE) to act as a dry lubricant. The dry lubricant has a particle size of about 3 m. The overlay layer 106 further comprises less than 0.5 wt % leveller and silane as an adhesion agent.

[0073] The overlay layer 106 has a thickness of about 10 m and appears gold in colour due to the coated aluminium flakes.

[0074] To form the sliding bearing 100 having a polymer based overlay layer 106, the polymer (PAI) is added to a premixed solvent blend to form a solution. The dry lubricant and the leveller are added to the solution to form a suspension. The aluminium flakes are made into a slurry with a premixed solvent blend and this slurry added to the solution. The silane is then added to the solution.

[0075] The polymer-based matrix solution is then applied to the metallic substrate 102 which may already have a bearing lining layer 104 on its inner surface. The polymer-based matrix solution is applied by spraying to form a series of sub-layers. After the deposition of each sub-layer, the solvent is removed by a flash-off phase. After deposition, the polymer-based matrix solution is cured by heating the sliding bearing 100.

[0076] Although illustrated in FIG. 1 in relation to a half bearing shell, the present invention equally applies to other sliding engine components, including semi-annular, annular or circular thrust washers, and bushes. The mechanical performance enhancing additives (e.g. dry lubricant particulate, silane and metal particulate) dispersed within the polymer-based matrix provide significant enhancements to the mechanical performance of the sliding engine component, such as wear resistance, adhesion promotion, fatigue resistance, and frictional properties.