Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-02-04
2002-04-09
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S448000, C428S212000, C428S217000, C428S908800, C427S488000, C427S489000, C427S492000
Reexamination Certificate
active
06368717
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a combination wear protection film and methods for generating and using the combination protection film in technical devices, in particular mechanical energy transfer mechanisms.
BACKGROUND INFORMATION
Practically all objects are subjected to a greater or lesser degree of wear due to interactions with their environment. As a rule, this wear results over time and decreases in the utilitarian value or functionality of the object. Efforts have therefore always been made to configure technical components, i.e. objects having a technical function, in such a way that when used as intended they exhibit as little wear as possible and thus can fulfill their purpose for as long as possible.
Depending on the manner in which they interact with their environment, components are subjected to very different wear stresses that are to be counteracted with very different measures.
In the case of components that do not need to transmit any appreciable energy, wear occurs essentially due to the action of light, air, climatic influences, and/or particle impact. The principal task here is to equip the objects with nonporous, scratchproof surfaces. One conventional method that equipped a wide variety of surfaces with polymer coatings is the plasma polymerization method. In this method, a plasma is generated by electrical excitation in a high vacuum using saturated or unsaturated compounds that can be vacuum-evaporated. From the monomer compounds, fragments such as gaseous radicals, radical ions, ions, and excited molecules form in the plasma and are deposited onto a substrate, on which they form a highly crosslinked polymer film that constitutes a sealed coating. Detailed information about implementation of this method is provided, for example, in Ullmanns Encyclopedia of Industrial Chemistry, Vol. A20, pages 755-756, 5
th
ed. and the literature cited therein, Comprehensive Polymer Science 4, pp. 357-375 and Encyclopedia Polymer Science and Engineering. 11, pp. 248-261.
An interesting possibility, based on this method, for depositing a transparent scratchproof coating onto plastics such as polymethyl methacrylate or polycarbonate—as used, for example, in the manufacture of automobile headlights—is Schutzschichten durch Plasmapolymerisation (Protective Film Using Plasma Polymerization) of Bosch Technische Berichte (Bosch Technical Reports) 8 1986/87 published in Handbuch Plasmapolymerisation (Plasma Polymerization Manual), VDI-Bildungswerk (VDI Education Text), 1990. According to. this publication, plasma polymerization of HMDS(O) is used to produce on the plastic surface a plasma polymer film that is relatively soft directly on the plastic surface, but becomes harder and harder with increasing thickness and terminates in a hard, quartz-like surface film. In practical terms, this hardness gradient is produced by the fact that plasma polymerization is initially performed in the presence of very little oxygen, and the oxygen partial pressure is continually raised as the film thickness increases.
Conditions are even more complex in mechanical energy transfer systems, which have components that are exposed not only to the kind of mechanical stress that occurs in the case of headlight but also to lenses, for example stone impact, abrasion wear particularly high and complicated loads. Components of this kind are exposed to shear forces, impact stresses, high pressures, and in particular to sliding frictional forces as well as long-term vibratory effects, which act on the elements either individually or (as a rule) simultaneously, albeit to different degrees, and result in more or less rapid wear.
One solution that at first glance appears obvious—i.e. to manufacture all the functional elements from materials that can withstand the various wear stresses—runs into considerable and often insurmountable difficulties, either because such materials are not conventional for suitable materials are much too expensive or very difficult or impossible to shape or machine into the desired components.
Many attempts have therefore been made to manufacture the functional elements of mechanical energy transfer systems as well from easily shaped and (whenever possible) also inexpensive materials, and to impart the necessary wear resistance to them by way of a surface finish.
Different protective measures are necessary depending on the type of effect that causes the wear. It is conventional, for example, for drills not only to be equipped with hard metal cutting edges, but also vacuum-coated with hard-material coatings, for example titanium nitride. In highly stressed energy transfer elements, however, very high demands are placed on these surface protective coatings. Desirable properties include, for example, good adhesion to the component, good cohesion and minimal stress within the film, high hardness and load-carrying capability, minimal coefficient of friction, good surface smoothness, and minimal adhesion to the countermember. In general, homogeneous hard-material films on wear-affected substrates cannot meet this aforesaid combination of criteria. Methods have therefore already been described for producing combination films that can be better adapted to requirements.
International Published Patent No. WO 95/16799 describes components equipped, for protection against wear, with a hard-material film that is composed of an adhesion film in contact with the component, a functional film thereabove, and a surface film. The adhesion film comprises a titanium composition, in particular titanium boride, or, if the component comprises a metallic substrate, pure titanium. The functional film is made up in turn of three films of hard-material alloys (titanium nitrides, titanium carbides, and/or titanium borides) of various composition, for example titanium nitride, titanium carbonitride, and titanium carbide, or titanium boronitride, titanium boronitride carbide, and titanium borocarbide, with gradual transitions in composition between the films.
The individual films are obtained by successively vacuum evaporating the titanium compositions, in accordance with a predetermined schedule, onto the substrate while simultaneously allowing high-energy (and, in particular, heavy) ions to act on it. The coating temperature for this method is approx. 200° C. The surface film comprises a metal-containing carbon film (i-C(Ti)), and optionally also a metal-free carbon film (a-C:H) thereabove.
Film deposition in combination with heavy ion bombardment solves adhesion and film separation problems.
For some time, efforts have been made to replace expensive and/or difficult-to-machine materials with more favorable materials, e.g. roller bearing steel, for the manufacture of mechanically stressed components. In the context of these efforts, many attempts have also been made to fabricate components with a technical function from plastics. Plastics not only have the advantage of economical accessibility, but are also available in many different types, can be made into almost any desired shape, and have advantageous physical properties, e.g. favorable internal damping or resonance, which means they have little tendency to generate, accept and transmit vibration. This property not only prevents fatigue wear, but also results in particular low operating noise.
In cases in which no appreciable mechanical loads occur, it has also been possible to create sufficient surface protection, for example by applying (as described above) a scratch protection film of SiO
2
.
In the case of mechanically stressed components, however, the wear properties of the more favorable materials are often inadequate. As discussed above, in such cases an attempt is made to achieve the necessary wear resistance for the components by way of a thin coating. In the case of plastics as an economical material for wear-stressed components (i.e. gears or friction clutches), hard films must be applied onto these components.
Since high-temperature tolerance plays a role in the coating process for many materials, and in particular for
Forget Jeanne
Rauschnabel Johannes
Voigt Johannes
Dawson Robert
Feely Michael J
Kenyon & Kenyon
Robert & Bosch GmbH
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