Abstract:
An abrasion resistant article ( 10, 30, 40 ) for use, while submerged or partly submerged in molten glass, in a glass article manufacturing operation, the article having a ceramic element ( 12, 32, 42 ) coated on its molten glass contacting surfaces with a thin base coating of a nickel chromium-aluminum-cobalt-yttria-composite powder ( 18, 34, 44 ) and a somewhat thicker coating ( 20, 36, 46 ) of a prealloyed ceria-yttria stabilized zirconium oxide superimposed on the base coating.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to coated ceramic parts of the type used in manufacturing articles from molten glass, and to a method of fabricating such parts. More particularly, this invention relates to the coating of ceramic parts that are to be submerged, or partly submerged, in molten glass to retard the abrasion of the molten glass contacting surfaces of such parts by the molten glass. 
     2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 AND 1.98 
     In the manufacture of glass articles from a molten glass composition, for example, in the manufacture of glass containers from a molten soda-lime-silica glass composition by a glass container forming machine of the individual section (I.S.) type, various ceramic parts are used at locations where the parts are submerged or partly submerged in the molten glass. Such parts include a ceramic orifice ring, as generally described in U.S. Pat. No. 4,950,321 (DiFrank), which is submerged in molten glass with its upper surface in contact with molten glass, and ceramic glass flow control needles, as identified by reference numeral 32 in U.S. Pat. No. 5,660,610 (DiFrank et al.), and a ceramic feeder tube, as identified by reference numeral 80 in the aforesaid &#39;610 patent, which are partly submerged, while in use, in molten glass. The aforesaid &#39;321 and &#39;610 patents are assigned to the assignee of this application, and their disclosures are incorporated by reference herein. 
     Molten glass compositions, including soda-lime-silica glass compositions, are very abrasive to the types of ceramic compositions that are used in the manufacture of parts for use, while submerged or partly submerged, in molten glass, and this necessitates frequent replacement of such ceramic parts, orifice rings, for example, typically requiring replacement at 30-60 day intervals, depending on glass color and temperature, and being shorter in high production installations. 
     BRIEF SUMMARY OF THE INVENTION 
     It has now been found, however, that it is possible to substantially extend the useful lives of ceramic parts used, while submerged in molten glass, to produce useful articles from the molten glass. The useful lives of the ceramic parts are substantially extended by coating all molten glass contacting surfaces of each article with a superimposed pair of these coatings, each such coating being applied in a fairly thin layer. The innermost or base or ceramic part-contacting coating which need only be applied in an approximate thickness of 0.002 in., is a composite powder coating that is made up of a nickel chromium-aluminum-cobalt-yttria composite powder. Such a coating powder is available from Metco Division of Perkin-Elmer Corporation, whose headquarters are in Westbury, Long Island, N.Y., under their product designation Metco 461. The base coated-ceramic part is then further coated, to an approximate thickness of 0.006 in., with a powder coating that is made up of a prealloyed ceria-yttria stabilized zirconium oxide, which is also available from the Metco Division of Perkin-Elmer Corporation, and this coating powder is offered under the product designation Metco 205 NS powder. It is believed that the base coat, which serves as a bond coat for the top coat, and the top coat for each such coated ceramic part will interact with the ceramic part, after being heated when the part is put into production, to produce a high strength, high resistant coating. Such a coating also produces a thermal barrier between the ceramic and the molten glass, and this thermal barrier protects the ceramic part, to reduce thermal shock thereto and to alleviate the occurrence of cracking. 
     Accordingly, it is an object of the present invention to provide enhanced life ceramic parts for use, while submerged or partly submerged, in molten glass, in the manufacture of articles from the molten glass. It is also an object of the present invention to provide a method for treating ceramic glass-making parts to extend the useful lives of such parts, notwithstanding that such parts are to be used, while submerged or partly submerged, in molten glass, which is otherwise highly abrasive to such ceramic parts. 
    
    
     For a further understanding of the present invention and the objects thereof, attention is directed to the drawing and the following brief description thereof, to the detailed description of the invention and to the appended claims. 
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is an elevation view, in cross-section, of a ceramic orifice ring according to the present invention, which has been fabricated by the method of the present invention, for use in a glass manufacturing operation; 
     FIG. 2 is an elevation view partly in cross-section, of a ceramic feeder tube according to the present invention, which has been fabricated by the method of the present invention, for use in a glass manufacturing operation; and 
     FIG. 3 is an elevation view, partly in cross-section, of a ceramic flow control needle according to the present invention, which has been fabricated by the method of the present invention, for use in a glass manufacturing operation. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An orifice ring according to the present invention is identified generally by reference numeral  10  in FIG.  1 . The orifice ring  10  is made up of a ceramic element  12 , which may be of conventional construction, and is designed to be used at the outlet of a molten glass feeder bowl that is used to provide molten glass to an I.S. glass forming machine through openings  14 ,  16 , in the orifice ring  10 . Thus, the orifice ring  10  is submerged in molten glass during its useful life with its upper surface in contact with the molten glass. 
     The ceramic element  12  of the orifice ring  10  is provided with a superimposed pair of coatings  18 ,  20  on each of its glass contacting surfaces. The innermost or base coating  18  is a coating that is made up of nickel chromium-aluminum-cobalt-yttria composite powder that is applied to the ceramic element  12  to an approximate thickness of 0.002 in., by plasma spraying, and Metco 461 powder coating from Metco Division of Perkin-Elmer is a suitable coating material for use as the coating  18 . 
     The ceramic element  12 , with the coating  18  applied thereto, is again coated, this time with a coating  20 , which is applied to the exterior of the coating  18  on the ceramic element  12 . The coating  20  is also applied as a powder by plasma coating, and is applied to an approximate thickness of 0.006 in. A prealloyed ceria-yttria stabilized zirconium oxide, such as that available from Metco Division of Perkin-Elmer under their designation Metco 205 NS, is suitable for use as the coating  20 . The Metco brochure for the Metco 205 NS coating describes the plasma application of the coating to a ceramic element, and its disclosure is also incorporated by reference herein. The orifice ring  10 , with the coatings  18 ,  20  applied to the ceramic element  12  thereof, is installed without further processing in a glass feeder bowl. It is believed that the heat required during the plasma spraying of the coatings ( 18  and  20 ) allows for interaction between the ceramic element  12  and the base coating  18 , and also interaction between the base coating  18  and the coating  20 . This interaction between the ceramic element  12 , the base coating  18  and the coating  20  creates a thermal barrier that protects the ceramic element to reduce the thermal shock it experiences upon sudden exposure to molten glass, and alleviates the occurrence of cracking of the ceramic element  12 . The dual coating  18 ,  20  of the ceramic element  12  not only increases the wear resistance of the orifice ring  10  in spite of its submergence in molten glass, but it also protects those areas that have less ceramic mass, such as the bridge area (not shown) of the orifice ring, from excessive thermal gradients. 
     A feeder tube according to the present invention is identified generally by reference numeral  30  in FIG.  2 . The feeder tube  30  is made up of an annular ceramic element  32 , which may be of conventional construction, and is designed to have its lowermost end submerged in molten glass in a feeder bowl that is used to provide molten glass to an I.S. glass forming machine. Thus, the lowermost end of the feeder tube  30  is submerged in molten glass during its useful life. 
     The portion of the ceramic element  32  that is submerged in molten glass is provided with a superimposed pair of coatings  34 ,  36  on all of its molten glass-exposed surfaces. The innermost or base coating  34  is a coating that is made up of a nickel chromium-aluminum-cobalt-yttria-composite powder, and this coating is applied to the submerged portion of the ceramic element  32 , to an approximate thickness of 0.002 in., by a plasma spraying. Metco 461 powder coating from Metco Division of Perkin-Elmer is a suitable coating material for use as the coating  34 . 
     The submerged portion of the ceramic element  32 , with the coating  34  applied thereto, is again coated with the coating  36 , which is applied to the exterior of the coating  34  on the ceramic element  32 . The coating  36  is also applied as a powder by plasma coating, and is applied to an approximate thickness of 0.006 in., a prealloyed ceria-yttria stabilized zirconium oxide, such as that available from Metco Division of Perkin-Elmer under their designation Metco 205 NS being suitable for use as the coating  36 . 
     The feeder tube  30 , with the coatings  34 ,  36  applied to the ceramic element  32  thereof, is installed without further processing in a glass feeder bowl with molten glass extending from the lowermost end of the feeder tube  30  to a level not above the level of the coatings  34 ,  36  on the ceramic element  32  thereof. 
     A flow control needle according to the present invention is identified generally by reference numeral  40  in FIG.  3 . The flow control needle  40  is made up of a ceramic element  42 , which may be of conventional construction, and is designed to be used to control the flow of molten glass through submerged outlets of a molten glass feeder bowl that is used to provide molten glass to an I.S. glass forming machine. Thus, the lowermost portion of the flow control needle is submerged in molten glass during its useful life. 
     The ceramic element  42  of the flow control needle  40  is provided, in the lowermost portion thereof, with a superimposed pair of coatings  44 ,  46  on its lowermost portion, namely, the portion that is to be submerged in molten glass in a feeder bowl. The innermost or base coating  44  is a coating that is made up of a nickel chromium-aluminum-cobalt-yttria-composite powder, and this coating is applied to element  42  to an approximate thickness of 0.002 in., by plasma spraying. Metco 461 powder coating from Metco Division of Perkin-Elmer is a suitable coating material for use as the coating  44 . 
     The ceramic element  42 , with the coating  44  applied thereto, is again coated, with the coating  46 , which is also applied to the exterior of the coating  44  on the ceramic element  42 . The coating  46  is also applied as a powder by plasma coating, and is applied to an approximate thickness of 0.006 in., a prealloyed ceria-yttria stabilized zirconium oxide, such as that available from Metco Division of Perkin-Elmer under their designation Metco 205 NS, being suitable for use as the coating  46 . 
     Although the best mode contemplated by the inventors for carrying out the present invention as of the filing date hereof has been shown and described herein, it will be apparent to those skilled in the art that suitable modifications, variations and equivalents may be made without departing from the scope of the invention, such scope being limited solely by the terms of the following claims and the legal equivalents thereof.