Abstract: A surface processing method and power transmission component includes transforming a surface region of a metal alloy into a hardened surface region at a temperature that is less than a heat treating temperature of the metal alloy. The metal alloy includes about 11.1 wt % Ni, about 13.4 wt % Co, about 3.0 wt % Cr, about 0.2 wt % C, and about 1.2 wt % Mo which reacts with the C to form a metal carbide precipitate of the form M2C. The surface processing temperature, vacuum pressure, precursor gas flow and ratio, and time of processing are controlled to provide a desirable hardened surface region having a gradual transition in nitrogen concentration.

Abstract: A method of nitriding a metal includes transforming a surface region of a generally nitrogen-free metal into a nitrogen-containing solid solution surface region. A first heating process heats the surface region at a first temperature in the presence of a nitrogen gas partial pressure to form a nitrogen-charged surface portion on the surface region. A second heating process heats the surface region and nitrogen-charged surface portion at a second temperature for a predetermined time to interstitially diffuse nitrogen from the nitrogen-charged surface portion a depth into the surface region. Coincident with the second heating process, an ionized inert or reducing gas removes the nitrogen-charged surface portion. The resulting nitrogen-containing solid solution surface region has a gradual transition in nitrogen concentration.