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US 5,851,313 AGranted
Case-hardened stainless steel bearing component and process and manufacturing the same
AssigneeThe Timken Company
InventorDavid L. Milam
Life of this patent
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AssigneeThe Timken Company
InventorDavid L. Milam
Estimating the term…
A stainless steel bearing component containing in excess of 11% chromium and between 0.05% and 0.50% carbon is case-hardened by introducing carbon or nitrogen into the surface of the race using a plasma process. The component is heated in a chamber from which air is evacuated. There it is bombarded with hydrogen ions to clean its surface. Next, while the component remains at an elevated temperature, a gas containing carbon or nitrogen or both is introduced into the chamber where it exists at a relatively low pressure on the order of 2-9 torr. A plasma is produced intermittently, and it causes carbon or nitrogen or both to diffuse intio the surface of the component and create a case containing a greater proportion of carbon or nitrogen than the underlying core. Thereafter, the component is cooled and with most stainless steels this may be acheived by quenching in oil. Where the case is enriched in carbon, the component is thereafter reheated to a temperature where its core exists as single phase austenite and held at that temperature to effect a soak. An oil quench follows and it converts much of the austenite to martensite. The quench in turn may be followed by cryogenic cooling to convert retained sustenite into martensite. After assuming ambient temperature, the component is again heated to temper the hardened case.
A corrosion resistant bearing component having a core and a case over the core with the case being harder than the core, the core comprising iron, 0.05% to 0.50% by weight carbon, and at least 11% by weight chromium, the case having a greater amount of martensite or nitrides than the core as a consequence of carbon or nitrogen having been diffused into the bearing component while subjected to a plasma containing carbon or nitrogen or both, the carbon content of the case at its surface not exceeding about 0.98% by weight.
A process for producing a corrosion resistant bearing component, said process comprising cleaning the surface of a steel shape having the configuration generally required for the component, the steel of the shape comprising iron, less than 0.50% by weight carbon and more than about 11% by weight chromium;
A process for producing a corrosion resistant bearing component, said process comprising cleaning the surface of a steel shape having the configuration generally required for the component, the steel of the shape comprising iron, less than 0.50% by weight carbon and more than about 11% by weight chromium;
Dependencies are inferred from the claim text.