| US 7,520,940 B2 | ||
| Steam oxidation of powder metal parts | ||
| Hyung Kyu Yoon, Peoria, Ill. (US); Thomas E. Clements, Peoria, Ill. (US); Daniel Patrick Vertenten, Aurora, Ill. (US); and David Anthony Cusac, East Peoria, Ill. (US) | ||
| Assigned to Caterpillar Inc., Peoria, Ill. (US) | ||
| Filed on Jul. 29, 2004, as Appl. No. 10/901,366. | ||
| Prior Publication US 2006/0024516 A1, Feb. 02, 2006 | ||
| Int. Cl. C23C 26/00 (2006.01) | ||
| U.S. Cl. 148—284 [148/537; 419/19; 419/54; 419/55] | 21 Claims |
| 1. A method of forming an oxide layer on a powder metal part, comprising:
placing the powder metal part in a furnace;
raising a temperature of the furnace to a first temperature;
maintaining the furnace at the first temperature for a first predetermined amount of time;
maintaining the powder metal part in a steam environment for a period of time greater than or equal to about 15 minutes;
maintaining the furnace at a second temperature between about 460° C. and about 500° C. for a period of time greater than
or equal to about 10 minutes, the second temperature being higher than the first temperature;
maintaining the furnace at a third temperature between about 570° C. and about 610° C. for a period of time greater than or
equal to about 30 minutes; and
forming an oxide layer on the powder metal part, wherein the oxide layer has a thickness greater than about 7 microns.
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