Norton Company

John W Lucek

Normand D Corbin

James G Hannoosh

Kazimierz Sawicki

Brad J Miller

A composite ceramic structure which does not fail catastrophically and thus is useful as a ceramic rolling contact bearing assembly is disclosed. The structure is a ceramic monolith bonded through an interlayer to a fiber-reinforced ceramic body. The structure is useful at elevated temperatures.

High temperature ceramic composite

The reliability of silicon nitride bodies for use in bearings can be greatly improved by control of microstructural flaws which produce bright specular reflections when metallographically prepared surfaces of the composites are examined microscopically in low angle incident light, dark field reflected light, or reflected polarized light viewed through a crossed polarizing analyzer. The population of such flaws can be controlled by modestly increasing the normal amount of intergranular phase and longer than normal milling times before sintering. Size classification of the powder before compression also improves the performance of the body. The fatigue cycles to failure of ten percent of the silicon nitride surfaces tested at 6.9 GPa contact stress in accelerated bearing failure ASTM Test STP 771 (L.sub.10 parameter) for sintered bodies prepared according to this invention is increased by about an order of magnitude over the values obtained with the best previously known type of silicon nitride body for bearing applications.

Rolling contact bearings, material for bearing surfaces, and process

The invention is an electrophoretic casting process which produces highly dense green castings with residual liquid e.g. water below 7%, and which eliminates excessive liquid and electrode degradation. This is accomplished by careful selection of slip viscosity, utilization of an impervious casting mold set-up in which only a minor part of the mold is conducting, application of a varying voltage cycle, and moving one electrode relative to the other.

Growing community of inventors

Worcester, MA, United States of America

John W Lucek