Process and apparatus for the coating of shaped articles by cathode sputtering

Abstract

The invention concerns a method of coating shaped parts having a three-dimensional coating surface by the cathodic atomization of target material of a first cathode arrangement. The cathode arrangement comprises a magnetic field generator for the concentration of a first discharge space (plasma cloud) in the zone of the target surface by means of a first magnetic field (plasma trap), which is spatially closed with respect to the target. According to the invention and for the purpose of producing a uniform coating even on parts of complicated shape, it is proposed that, on their side disposed opposite the first cathode arrangement, the shaped parts should be simultaneously subjected to the atomizing action of a second cathode arrangement with the same target material. The second cathode arrangement likewise comprises a magnetic field generator for concentrating a second discharge space in the zone of the target surface by means of a second magnetic field, spatially closed with respect to the target; the second cathode arrangement is so arranged in relation to the first that the two cathode arrangements between them form a gap in which discharge occurs and through which the shaped parts are moved. Furthermore, a voltage U Sub , which is negative with respect to ground and is of such magnitude that the discharge spaces of the two cathode arrangements reach and touch the shaped part, is applied to said part. The invention also covers apparatus for performing the method of the invention.

We claim: 
     
       1. A method of coating a part by cathodic atomization of target material, the part having a three-dimensional surface to be coated, comprising: providing two, facing cathodic atomization devices for receiving the part to be coated in a discharge space therebetween, each cathodic atomization device having a target of the same material delimiting the discharge space, a cathode arrangement for producing a plasma cloud of the target material in the discharge space, and magnetic means producing a magnetic field which closes on the target for concentrating the plasma cloud of the target material in a zone at the target surface delimiting the discharge space; and   applying a voltage which is negative with respect to ground to the part to be coated in the discharge space sufficient to cause the plasma clouds of the target material from the cathodic atomization devices at least to touch each other at the part to be coated in the discharge space.   
     
     
       2. Apparatus of coating a part by cathodic atomization of target material, the part having a three-dimensional surface to be coated, comprising: two, facing cathodic atomization devices for receiving the part to be coated in a discharge space therebetween, each cathodic atomization device having a target of the same material delimiting the discharge space, a cathode arrangement for producing a plasma cloud of the target material in the discharge space, and magnetic means producing a magnetic field which closes on the target for concentrating the plasma cloud of the target material in a zone at the target surface delimiting the discharge space; and   means for applying a voltage which is negative with respect to ground to the part to be coated in the discharge space sufficient to cause the plasma clouds of the target material from the cathodic atomization devices at least to touch each other at the place in the discharge space where the part to be coated will be received. .Iadd.   
     
     
       3.  A method of coating a part by cathodic atomization of target material, the part having a three-dimensional surface to be coated, comprising: providing two, facing cathodic atomization devices for receiving the part to be coated in a discharge space therebetween, each cathodic atomization device having a target of the same material with a surface delimiting the discharge space, a cathode arrangement for producing a plasma cloud of the target material in the discharge space, and magnetic means producing a magnetic field which closes on the target for concentrating the plasma cloud of the target material in a zone at the target surface delimiting the discharge space; and   applying a voltage which is negative with respect to the ground to the part to be coated in the discharge space sufficient to facilitate at least touching of the plasma clouds of the target material from the cathodic atomization devices at the part to be coated in the discharge space. .Iaddend. .Iadd.   
     
     
       4.  The method of claim 3, wherein providing the cathodic atomization devices comprises providing at least one thereof with operating parameters so selected that the plasma clouds of the two cathodic atomization devices would overlap at least partially even when no part has been received in the discharge space therebetween and wherein applying the voltage which is negative with respect to ground to the part comprises so applying at least 10 V. .Iaddend. .Iadd. 
     
     
       5.  The method of claim 3, wherein providing the cathodic atomization devices comprises providing the cathode arrangement of each thereof with a discharge voltage of from about 200 V to about 1000 V in a way for an atomization power of from about 5 to about 30 watts/cm 2  at the surface of the target, providing the target surfaces, delimiting the discharge space with a spacing of from about 80 mm to about 200 mm, providing the magnetic means with a magnetic field strength of from about 150 Oersteds to about 350 Oersteds, and wherein applying a voltage comprises applying from about -50 V to about -500 V to the part; and further comprising providing a pressure in the discharge space of from about 1×10 -3  mbars to about 5×10 -2  mbars and a temperature to the part of from about 150° C. to about 500° C., whereby the method is adapted for producing hard coatings, and particularly nitride coatings. .Iaddend. .Iadd. 
     
     
       6.  The method of claim 3, wherein providing the cathodic atomization devices comprises providing the cathode arrangement of each thereof with a discharge voltage of from about 200 V to about 1000 V in a way for an atomization power of from about 10 to about 15 watts/cm 2  at the surface of the target, providing the target surfaces delimiting the discharge space with a spacing of from about 100 mm to about 150 mm, providing the magnetic means with a magnetic field strength of from about 200 Oersteds to about 250 Oersteds, and wherein applying a voltage comprises applying from about -50 V to about -500 V to the part; and further comprising providing a pressure in the discharge space of from about 5×10 -3  mbars to about 2×10 -2  mbars and a temperature to the part of from about 250° C. to about 300° C., whereby the method is adapted for producing hard coatings, and particularly nitride coatings. .Iaddend. .Iadd.7. The method of claim 1, wherein providing the pressure in the discharge space comprises providing the same with an atomsphere of an inert gas and nitrogen having a partial pressure of from about 4×10 -4  mbars to about 8×10 -4  mbars. .Iaddend. .Iadd.8. The method of claim 7, wherein the inert gas is 
     
     
        argon. .Iaddend. .Iadd.9.  Apparatus of coating a part by cathodic atomization of target material, the part having a three-dimensional surface to be coated, comprising: two, facing cathodic atomization devices for receiving the part to be coated in a discharge space therebetween, each cathodic atomization device having a target of the same material with a surface delimiting the discharge space, a cathode arrangement for producing a plasma cloud of the target material in the discharge space, and magnetic means producing a magnetic field which closes on the target for concentrating the plasma cloud of the target material in a zone at the target surface delimiting the discharge space; and   means for applying a voltage which is negative with respect to ground to the part to be coated in the discharge space sufficient to facilitate at least touching of the plasma clouds of the target material from the cathodic atomization devices at the place in the discharge space where the   
     
     
        part to be coated will be received. .Iaddend. .Iadd.10.  The apparatus of claim 9, wherein the cathodic atomization devices comprises at least one thereof adapted and configured for operating parameters so selected that the plasma clouds of the two cathodic atomization devices would overlap at least partially even when no part has been received in the discharge space therebetween and wherein the means for applying the voltage which is negative with respect to ground to the part comprises means for so 
     
     
        applying at least 10 V. .Iaddend. .Iadd.11.  The apparatus of claim 9, wherein, in the cathodic atomization devices, the cathode arrangement of each thereof has a discharge voltage of from about 200 V to about 1000 V in a way for an atomization power of from about 5 to about 30 watts/cm 2  at the surface of the target, the target surfaces delimiting the discharge space have a spacing of from about 80 mm to about 200 mm, the magnetic means has a magnetic field strength of from about 150 Oersteds, to about 350 Oersteds, and wherein the means for applying a voltage applies from about -50 V to about -500 V to the part; and further comprising means for providing a pressure in the discharge space of from about 1×10 -3  mbars to about 5×10 -2  mbars and a temperature to the part of from about 150° C. to about 500° C., whereby the apparatus is adapted for producing hard coatings, and 
     
     
        particularly nitride coatings. .Iaddend. .Iadd.12.  The apparatus of claim 9, wherein the surfaces of the targets are curved in a manner to delimit the discharge space between the target surfaces as at least a sector of substantially cylindrical section. .Iaddend. .Iadd.13. The apparatus of claim 12, wherein the surfaces of both targets are curved and arranged to delimit an annular, substantially-cylindrical section sector to the discharge space therebetween, and further comprising a cylindrical holder for holding the part to be coated and at least one other part to be coated, the holder being rotatable through the annular substantially-cylindrical section sector of the discharge space delimited by the target surfaces, thereby substantially enclosing at least the target of one of the cathodic atomization devices, and having at least a portion which is removable to allow removal of the target substantially enclosed thereby. .Iaddend.