Ford Motor Company Limited

Roy L Van Alsten

David Moskowitz

Leslie L Terner

Morton E Milberg

Donald J Cassidy

A method is disclosed for making an aging-resistant, partially stabilized zirconia ceramic, which method is not totally dependent upon grain size control, can function to eliminate substantially any monoclinic phase that results from machining such zirconia article, and employs a novel heat treatment to do so. The method particularly comprises: (a) sintering such article at a temperature and for a period of time to produce a densified product having little or no monoclinic crystal phase when cooled to room temperature (i.e. 2550.degree.-2650.degree. F. for 0.5-4 hours); (b) subjecting the cooled sintered article a machining operation that results in the formation of monoclinic crystal phase on the surface of the part; and (c) heating said treated article to the temperature range of 1800.degree.-1950.degree. F. (982.degree.-1066.degree. C.) to re-transform monoclinic crystal structure to tetragonal crystal.

Method of making a stress resistant, partially stabilized zirconia

This application discloses a new powder composition which may be plasma sprayed onto the surface of an article to provide a protective coating therefor. The protective coating may be resistant to heat, wear, and corrosion. The coating may also provide a thermal or radiation barrier. In particular, the coating composition for arc plasma spraying consists of finely divided silicon carbide mixed with finely divided silicon. This coating composition is applied to a substrate by developing a plasma spray, feeding the coating composition to the plasma spray and directing the plasma spray at an exposed surface of the substrate so that the exposed substrate is coated with a coating which consists essentially of beta silicon carbide and silicon. The new article of manufacture disclosed in this application, is a substrate with a tightly adherent coating thereon consisting essentially of beta silicon carbide and silicon. The substrate may be any material, either metallic or non-metallic, to which the coating adheres. The coating may provide the substrate with wear resistant characteristics as, for example, if the substrate is to be used for machining metals or as a valve seat in an aluminum engine. The substrate, with the coating thereon, may be used to withstand severe temperatures as, for example, in rocket nozzles and other areas where a substrate would be subjected to extreme temperatures.

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Redford, MI, United States of America

Roy L Van Alsten