Stainless steel nitriding with a high nitrogen ion beam flux and a high power plasma torch

Low energy-high flux (1,2 keV, 10¹⁶cm^-2s^-1) nitrogen ion implantation and high flux plasma torch nitriding (10²¹cm^-2s^-1) of AISI 304 L stainless steel have been carried out in the temperature range 400°C-600°C. Thick nitrided layers of high nitrogen content (25-30 at %) have been formed and the nitrogen depth profiles determined by nuclear resonance analysis (NRA) and/or glow discharge optical spectroscopy (GOOS). The phases formed were identified by X-ray diffraction at glancing incidence. Below 430°C, the formation of a solid solution or expanded austenite γN phase has been observed; for higher temperature, the precipitation of chromium nitride occurs together with the formation of a α bcc Fe (Ni) phase. An important increase of hardness was obtained at both temperatures as well as a significant and durable wear resistance.