Final surface machining of ionic ceramic, e.g. an engine valve, tappet or cam follower coating, comprises grinding with an ionic bonded oxide medium to produce an ultra-smooth surface retaining an ionic residue of the medium

摘要

Final machining of ionic ceramic surfaces, comprising grinding with a harder ionic bonded oxide medium to produce an ultra-smooth surface which retains an ionic residue of the medium, is new. A final machining process for ionic ceramic surfaces comprises repeated surface grinding with a final machining medium of ionic bonded oxide with grains which are harder than the grains of the covalent ionic ceramic, including frequent interruption of grinding to dress the medium, until an average surface roughness of about 0.04 mu m is achieved, the free ceramic surface retaining an ionic residue of the medium. An Independent claim is also included for a method of reducing friction between lubricated friction surfaces by pressing a silicon nitride friction surface, produced by the above process, against another friction surface with mixed hydrodynamic interface lubrication by oil having additives which react with the ionic residue to form a frictional torque reducing transfer film on the silicon nitride ceramic surface. Preferred Features: The ionic bonded oxide is aluminum oxide in the form of a grinding wheel, the ionic residue is aluminum oxide or hydroxide and the covalent ionic ceramic is selected from silicon nitride, sialon, beryllium oxide, silicon oxynitride, aluminum oxynitride and nitrogen-containing silicates.