Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Patent
1997-12-23
2000-11-07
Zimmerman, John J.
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
428677, 384912, F16C 3312, C22C 908, C23C 1416
Patent
active
061434272
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a multilayer material comprising a bearing material applied directly to a backing material by sputtering, which bearing material comprises a matrix material of copper or a copper-based alloy with finely dispersed lead inclusions.
2. Description of Related Art
Copper-based materials with various alloy elements are widely used as highly-loadable plain bearing materials in modern combustion engines. Their considerable strength makes them suitable for use as connecting-rod bearings, main bearings, piston pin bushings and rocker bushings as well as for use as gear parts or as components in machine construction in general. As the lead content increases and the tin content decreases, for example, conformability to and compatibility with the counter-member increases, whereas corrosion resistance and strength decrease markedly. For use as connecting-rod or main bearings in modern engine construction, these bearings are therefore generally provided with a third electrodeposited layer, which markedly improves corrosion resistance. Connecting-rod bearings and crank bearings constructed in this way find millions of applications in the engine construction industry. However, the three-layer structure of these multilayer materials is technically extremely complex.
It is known from "Gleitlager", E. Schmidt, R. Weber, 1953, p. 192, that with lead-bronzes there is a straightforward correlation between structural formation or structural shape and corrosion behaviour. This means that the more finely crystalline the structure and thus also the more finely the lead particles are dispersed within the matrix, the more corrosion-resistant the material. In addition, it is advantageous for the lead particles to exhibit as fine a globular structure as possible.
To counter effectively the loss in matrix strength as the lead content increases, efforts have been made to achieve as finely crystalline a structure as possible, but lower limits are set to the achievement thereof by for example casting methods. The very much more favourable strength values achieved with finely crystalline metallic materials compared with those which are coarsely crystalline are based on an effect which markedly increases strength and which may be understood from the following background described in "Physikalische Metallkunde", Peter Haasen, 2nd Edition 1984, p. 246:
In metallic materials, deformation is caused by the migration of lattice defects (dislocations). If such a material is present which has as finely crystalline a structure as possible, i.e. a high grain boundary content, then, if deformation and the consequent migration of dislocations occur, the latter become pinned at the grain boundaries and act as obstacles. High internal stress fields are induced thereby, which prevent or at least make more difficult any further migration of the dislocations. This state of affairs results in a direct correlation between grain size and strength in metallic materials by way of the Hall-Petch equation, this so-called grain boundary consolidation increasing as the grain diameter d falls according to d.sup.-0.5.
These structural requirements in the production of sliding materials may be fulfilled outstandingly by the application of PVD technology (sputtering) to the deposition of this group of materials.
It is known from DE 28 53 724 that the cathodic evaporation of metals, especially AlSnCu alloys, makes it possible to produce overlays which exhibit much higher hardness levels than cast materials of the same chemical composition, and consequently outstanding wear resistance. This higher strength is provided by hard oxide particles finely dispersed in the layer, which result in dispersion strengthening ensuring, particularly at relatively high temperatures, that the mechanical characteristic values, such as high-temperature strength and high-temperature wear resistance, do not drop noticeably, as is known to occur with casting alloys. In the case of this known multilayer material, in w
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Federal-Mogul World Wide Inc.
Zimmerman John J.
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