Patent ID: 8961711
Filing Date: 2015-02-24
Classification: C23C

Abstract:
1. A method of nitriding a metal article comprising at least one selected from stainless steels, a superalloy, a tool steel, a bearing steel, a cast iron product, or combinations thereof to provide a treated surface comprising: a. providing the metal article within a furnace operating at an approximately atmospheric pressure; b. introducing into an inlet of the furnace a gas atmosphere comprising a nitrogen source gas and a hydrocarbon gas wherein the gas atmosphere is substantially free of an added oxygen gas or oxygen-containing source gas wherein the introducing step is conducted by injecting the gas atmosphere through an electric arc-activation apparatus comprising: a low-power, high-voltage, non-pulsed, AC arc discharge, changing polarity from 50 to 60 times per second, where the peak-to-valley voltage ranges from 1 kV to 12 kV and the arc discharge current does not exceed 1 ampere; and c. heating the metal article in the gas atmosphere at one or more nitriding temperatures ranging from about 350° C. to about 1150° C. for a time sufficient to provide the treated surface.