HK1128951B - Sliding element and process for its production - Google Patents

Description

Sliding member and method for manufacturing same

Technical Field

The invention relates to a sliding component, comprising a molded carrier layer and a sliding layer applied to the molded carrier layer in an electroplating manner, wherein the sliding layer is formed by an alloy with alloy components of tin, antimony and copper, and the weight percentage of the antimony: 5 to 20%, copper: 0.5 to 20 percent, less than 0.7 percent of lead, less than 0.5 percent of other elements and the balance of tin. The invention also relates to a method for producing a sliding component by electrolytically applying a sliding layer formed from an alloy having the alloy components tin, antimony and copper on a shaped carrier layer.

Background

DE 8206353U1, for example, discloses a plain bearing coating of the aforementioned type. Here, the plain bearing coating is applied galvanically to a carrier layer on the steel shell. The plain bearing coating here has a thickness of approximately 20 μm. Furthermore, efforts are made to lower the copper content of the plain bearing coating to less than 0.5% by weight, since a comparatively higher copper content adversely affects the durability of the plain bearing coating.

The known plain bearing coating is produced in practice by electroplating using a wetting agent sold under the trade name Igepal CO 880 from Rhodia Nove, a nonylphenol ethoxylate having 30 Ethoxy (EO) units. The electrolyte layer structure appears as columnar crystals and no usable layer significantly larger than 20 μm can be formed. The service life of the plain bearing coating is therefore naturally very limited due to unavoidable wear.

Disclosure of Invention

It is an object of the present invention to provide a plain bearing coating having improved durability properties.

In the case of a sliding bearing of the aforementioned type, this object is achieved according to the invention by the tin crystals being formed in the sliding bearing coating in a substantially spherical shape.

In order to solve said problem, a method of the aforementioned type according to the invention is characterized in that an electrolyte based on fluoroboric acid and a metal fluoroborate in aqueous solution is used, the electrolyte containing the following components:

and some auxiliary agents which are not incorporated in the sliding member layer produced, wherein the migration speed of ions of the elements forming the sliding layer is controlled by at least one auxiliary agent according to their molecular weight, thereby producing tin crystals formed substantially in a spherical shape.

It has been found that by manufacturing the sliding layer in such a way that a major part (size 50%) of the tin crystals has a spherical structure instead of the former needle-like or columnar structure, a very uniform structure of the sliding layer is achieved. The spherical structure of the tin crystals is achieved in that the deposition rate is controlled by adding auxiliaries for macromolecules, in particular gelatin and/or resorcinol, so that the composition of the sliding layer and the resulting structure are adjusted in a desired manner. Here, C having a degree of ethoxylation of from 10 to 30 is used in a targeted manner₁₃C₁₅Oxo alcohols, C₁₆C₁₈Fatty alcohols or C₁₃-a wetting agent formed from oxo alcohols. Preferred wetting agents are oxo alcohols having a degree of ethoxylation of 20.

The structure formed according to the invention has a very homogeneous structure, in which a homogeneously distributed, at the same time substantially spherical, antimony-rich precipitate is obtained. A significantly more stable sliding layer is thereby obtained, which can be used stably and uniformly in a non-stratified manner with a thickness of 20 μm, in particular over 50 μm. Therefore, a sliding layer having a thickness of, for example, 500 μm can be formed without any problem.

"spherical" in reference to structure and crystallization is understood to mean grains having a ratio of maximum elongation to minimum elongation of the grain size of less than 3, preferably less than 2.

Suitable wetting agents are sold, inter alia, by the company BASF under the trade name Lutensol. Particularly suitable wetting agents (EO for degree of ethoxylation) are:

the wetting agents Lutensol ON 110 and TO 20 are particularly suitable for producing the plain bearing coating according TO the invention and for avoiding the formation of dendrites. Particular preference is given to Lutensol ON 110, i.e.C having a degree of ethoxylation of 20₁₃Oxo alcohols.

In a preferred embodiment of the sliding member according to the present invention, the copper content in the sliding layer is 3 to 6%. Contrary to the teaching of utility model 8206353U1, the increased copper content leads to an increase in the permissible load and service life of the sliding layer. The copper content can therefore be predetermined according to the invention, not only exceeding the copper content of less than 0.5% by weight which is advantageously endeavoured to be achieved, but also exceeding the copper content of 2% at the maximum which is mainly considered in the said document.

The preferred antimony content in the sliding layer is 8 to 17 wt.%.

The preferred copper content is 2 to 7%.

The proportion of tin crystals formed in a spherical shape in the sliding layer is preferably more than 70%, more preferably more than 80%.

The sliding member according to the invention may be a generally cylindrical sliding bearing sleeve, a component of such a sliding bearing sleeve or a substantially planar member. The shaped support member is composed of metal and may be composed in a conventional manner of steel with the bearing alloy applied, which has emergency lubrication properties. On which a sliding layer according to the invention is applied. Since the sliding layer according to the invention with a thick layer thickness can be applied with high stability, the bearing metal layer can also be omitted and the sliding layer can be applied directly on the profiled support member made of metal.

Detailed Description

The following test results of the examples are illustrated to illustrate the invention:

a matrix electrolyte (containing no wetting agent) having the following composition was prepared:

resorcinol and gelatin are aids that affect the composition and deposition rate of the formed layer. Resorcinol mainly affects the composition, whereas the large molecules of gelatin affect the crystalline structure, roughness and layer composition. For this purpose, gelatin concentrations of 0.1 to 0.5g/l can be set specifically.

At a bath temperature of 22 to 24 ℃ using a tin electrode at 2A/dm²The electrolytic deposition is carried out at a constant current.

The steel substrate is pre-coated (electrolytically) with a nickel layer.

SnSbCu deposition was performed on the rotating rod electrodes and on the strips. Deposition on a rotating rod electrode avoids uncontrolled dendrite growth that could compromise the test results.

All of the tested humectants described above produced other different textures upon deposition than the currently commonly used reference standard humectant. In particular, the growth of dendrites is significantly reduced.

The wetting agents Lutensol ON 110 and Lutensol TO 20 are particularly advantageously used here.

With the aid of the wetting agent, in particular with the aid of the wetting agent preferably used, the sliding layers achieved differ from the current sliding layers in terms of their crystal structure and have considerable operating advantages. In particular, a layer having an almost arbitrary thickness can be formed, so that a degree of freedom which is not yet present in terms of the layer thickness and the composition of the sliding element is thereby achieved.

Claims (9)

1. A sliding member having a shaped carrier layer and a sliding layer applied in an electroplated manner on the carrier layer, the sliding layer being formed from an alloy having the alloy components tin, antimony and copper, the percentage by weight of antimony: 5 to 20%, copper: 0.5 to 20%, the lead content being less than 0.7%, the total content of other elements being less than 0.5%, the balance being tin, characterized in that tin crystals are formed in the sliding layer substantially in a spherical shape.

2. Sliding element according to claim 1, characterized in that the thickness of the applied sliding layer is more than 20 μm.

3. Sliding element according to claim 1 or 2, characterized in that the copper content is 0.5 to 7%.

4. Sliding element according to claim 1 or 2, characterized in that the content of copper in the sliding layer is 3 to 6%.

5. The sliding member according to claim 1 or 2, wherein the content of antimony in the sliding layer is 8% to 17%.

6. Method for producing a sliding element by electrolytically applying a sliding layer on a shaped carrier layer, the sliding layer consisting of an alloy with the alloy components tin, antimony and copper, characterized in that an electrolyte based on fluoroboric acid and a metal fluoroborate in an aqueous solution is used, the electrolyte containing the following components:

and certain auxiliaries which are not incorporated in the sliding layer produced, said auxiliaries being gelatin and/or resorcinol, wherein the rate of electrodeposition is adjusted to 0.3 to 1.5 μm/min with the aid of the auxiliaries, depending on their molecular weight, so that tin crystals which form substantially spherical form are produced.

7. The process according to claim 6, wherein the wetting agent is C having a degree of ethoxylation of from 10 to 30₁₃C₁₅Oxo alcohols, C₁₆C₁₈Fatty alcohols or C₁₃Oxo alcohols.

8. Process according to claim 7, characterized in that C with a degree of ethoxylation of 20 is used₁₃-oxo alcohols as the wetting agent.

9. The method according to claim 6 or 8, characterized in that the wetting agent is used in a concentration of 0.1 to 3.0 g/l.