Metal treatment – Process of modifying or maintaining internal physical... – Surface melting
Patent
1991-08-14
1993-10-19
Wyszomierski, George
Metal treatment
Process of modifying or maintaining internal physical...
Surface melting
148513, 148525, 148565, 118320, 118620, B05B 506, H01H 1104
Patent
active
052541851
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method and apparatus for producing a surface-coated component, in particular a contact piece for a vacuum switch, consisting of a metallic substrate and at least one additive supplied to the substrate, where the surface of the substrate is melted open in at least one local area by means of a flow of energy and where the additive is combined with the molten material of the local area.
BACKGROUND OF THE INVENTION
The invention makes reference to a state of the art as disclosed, for example, in German Patent Disclosure DE-A1-3541584. A method disclosed in this patent publication is used for producing metal composites consisting of a basic material with at least one metal and further active components. In this case, a substrate made of a basic material is melted down to a preset depth in a locally selected area by means of radiant energy and the active component is supplied to the metal material. This requires radiation with very high beam current density, such as a laser beam, for example, and special energy transmission devices, by means of which the active component can be accelerated to high speeds.
It is known from Swiss Patent Disclosure CH-A5-661616 to expose a sinter body containing chrome and copper in a vacuum or an inert gas atmosphere to a highly concentrated heat flow, for example supplied by an electrical arc, having a beam current density of 10 to 1000 kW/cm.sup.2. In the course of the application of the heating current, lasting approximately 21 to 100 ms, the surface of the work piece is melted open. By means of subsequent cooling of the sinter body at a speed of 10.sup.4 to 10.sup.5 K/s, a contact piece for a vacuum switch is then formed, having a surface layer up to 3 mm thick and made of a finely dispersed copper-chrome material having a low gas content. Contact pieces produced in this manner considerably increase the operational reliability of vacuum switches, but require considerable apparatus outlay when producing contact pieces of large area.
SUMMARY OF THE INVENTION
It is the object of the invention to recite a method for producing a surface-coated component, particularly a contact piece for a vacuum switch, by means of which it is possible to produce even components with large areas with small outlay in apparatus.
This object is attained by use of a method in which a metallic substrate is pre-heated to a temperature that is considerably above room temperature, but below its melting point. After pre-heating of the surface of the substrate, a local area is melted open and an additive is applied to the substrate surface in the form of a loose layer of powder. The local area, which has been melted open by the energy flow, is guided to and through the powder layer and in this way powder present in the powder layer is wetted or the powder layer is soaked by the liquid material from the locally melted open area. As a result, the powder of the powder layer is bonded with the surface of the substrate and the desired surface layer is formed.
The apparatus for carrying out this method includes a support for the substrate and an additive supply device. A heat source is mounted in position to heat a local area of the substrate, and the supply device moves relative to the substrate to supply the additive after the local area has been heated. The support for the substrate may include a rotatable member.
With small outlay in apparatus, the method in accordance with the invention makes possible the production of surface-coated components which can be subjected to high loads. Small demands are made on the heating current source, because its beam current density can be kept low. Because of the low beam current density, evaporation and spattering of the additive is prevented to a large extent in the course of the production of the components. Thus, there is no interference with the desired stoichiometry of the surface layer. Surface layers up to several millimeters can be achieved without problems. Surface layers of this type are eminently suitable
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Calor-Emag AG
Wyszomierski George
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