In my below-listed U.S. Pat.  Nos:
__________________________________________________________________________ U.S. PAT.  NO.  TITLE OF PATENT ISSUE DATE __________________________________________________________________________ 4,351,855 NONCRUCIBLE METHOD OF AND 09/28/82 APPARATUS FOR THE VAPOR DEPOSITION OF MATERIAL UPON A SUBSTRATE USING VOLTAIC ARC IN VACUUM 4,438,153 METHOD OF AND APPARATUS FOR THE 03/20/84 VAPOR DEPOSITION OF A MATERIAL UPON A SUBSTRATE 4,537,794 METHOD OF COATING CERAMICS 08/27/85 4,505,948 METHOD OF COATING CERAMICS AND 03/19/85 QUARTZ CRUCIBLES WITH MATERIAL ELECTRICALLY TRANSFORMED INTO A VAPOR PHASE 4,548,670 SILICON MELTING AND EVAPORATION 10/22/85 METHOD FOR HIGH PURITY APPLICATIONS 4,565,711 METHOD OF AND APPARATUS FOR THE 01/21/86 COATING OF QUARTZ CRUCIBLES WITH PROTECTIVE LAYERS 4,569,307 SILICON MELTING AND EVAPORATING 02/22/86 APPARATUS FOR HIGH PURITY APPLICATIONS 4,596,719 MULTILAYER COATING METHOD AND 06/24/86 APPARATUS 4,609,564 METHOD OF AND APPARATUS FOR THE 09/02/86 COATING OF A SUBSTRATE WITH MATERIAL ELECTRICALLY TRANSFORMED INTO A VAPOR PHASE. __________________________________________________________________________ 
I have described a unique method of coating substrates which involves the striking of an electric arc utilizing, as one of the electrodes for the arc, a material of a substance to be coated onto a substrate. 
Among these patents, moreover, is U.S. Pat.  No.  4,537,794 which describes a method of coating ceramics, primarily to promote the adhesion of conductive layers thereto, whereby refractory metal layers are first applied to the ceramic substrate, e.g. by a process using a low voltage arc and at comparatively low temperatures in a vacuum, whereupon the conductive metal layer is applied, e.g. in a like manner. 
While the resulting coatings are highly adherent, they have only limited wear resistance. 
In recent years, the use of ceramic materials, such as clay-based ceramics as well as oxide ceramics, cermets, silicon nitride and silicon carbide ceramics have been found to be increasingly of interest in mechanical systems where wear at high temperatures may be a problem. 
It has been suggested, for example in the case of silicon nitride where contact pressure can cause deterioration of a wear surface, that coatings may be provided to limit the damage of such surfaces, and indeed, plasma-coating systems and like spray deposition techniques have been used for such coating purposes.  However, the resulting products have not been fully satisfactory.