The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 19, 1990
Filed:
Apr. 29, 1985
John W Lucek, Worcester, MA (US);
Norton Company, Worcester, MA (US);
Abstract
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.