Surface finishing covalent-ionic ceramics

摘要

Method of surface finishing covalent-ionic ceramics comprising: (a) repeatedly rubbing a finishing medium against an exposed surface of the ceramic, the medium being constituted of an ionic bonded oxide having grains harder than the grains of the covalent-ionic bonded ceramic; (b) interrupting the rubbing at frequent intervals to dress the medium by a single point diamond tool; and (c) continuing the repeated rubbing and dressing interruptions of steps (a) and (b) until a surface roughness of about 0.04 micrometer Ra has been achieved on the ceramic and the exposed surface of the ceramic retains an ionic residue of the finishing medium. Also, a method of effecting reduced friction between lubricated rubbing surfaces, comprising: (a) forming one of the rubbing surfaces of silicon nitride based ceramics having a polished surface roughness about 0.04 micrometer Ra with an ionic residue thereon resulting from finishing with an ionic-bonded oxide having grains harder than the grains of the silicon nitride ceramic; and (b) operating the silicon nitride rubbing surface against the other rubbing surface while lubricating the interface between such rubbing surfaces with oil in a mixed hydrodynamic regime, whereby the ionic residue is effective to react with additives in said lubricant oil to form a transfer film on said silicon nitride ceramic that reduces contact friction.