Patent ID: 8182617
Filing Date: 2012-05-22
Classification: B22F,B32B,C22C,C23C

Abstract:
1. A process for nitriding stainless steel comprising: a) forming an alloy of martensitic stainless steel from scrap or other ferrous metal through the application of high temperature to liquefy the scrap or ferrous metal to a molten liquid; b) incorporating metal additives to form a molten mixture; c) subjecting said molten mixture to water- or gas-atomization to yield a particulate base alloy powder; d) introducing hydrogen or argon gas in order to clean the surface of the powder prior to activation with nitrogen; e) removing the hydrogen or argon gas from the furnace; f) introducing nitrogen or ammonia gas at a partial pressure of from about 500 torr to about 1000 torr in a static or fluidized bed to nitrogen alloy the particulate base powder; g) quenching the nitrogen alloyed particulate base powder; h) heating the nitrogen alloyed powder in a hot iso-static press under vacuum at reduced pressure followed by the injection of argon gas at 1,000 psi; i) increasing the temperature to 1470° F. (800° C.) and the argon pressure to 15,000 psi; j) further increasing the temperature to 1920° F. (1050° C.) for four hours after which the consolidated particulate alloy powder is cooled to ambient temperature.