Parameters which characterize the nitriding atmosphere in the gas nitriding process of steel are: the nitriding potential K N , ammonia dissociation rate α and nitrogen availabilitym N2 . The article discusses the possibilities of utilization of the nitriding atmosphere's nitrogen availability in the design of gas nitriding processes of alloyed steels in atmospheres derived from raw ammonia, raw ammonia diluted with pre-dissociated ammonia, with nitrogen, as well as with both nitrogen and pre-dissociated ammonia. The nitriding processes were accomplished in four series. The parameters selected in the particular processes were: process temperature (T ), time (t), value of nitriding potential (K N ), corresponding to known dissociation rate of the ammonia which dissociates during the nitriding process (α). Variable parameters were: nitrogen availability (m N2 ), composition of the ingoing atmosphere and flow rate of the ingoing atmosphere (F In ).Keywords: Controlled gas nitriding, Nitrogen availability, Nitriding potential, Ammonia dissociation rate, Alloyed steels Parametrami charakteryzującymi atmosferę azotującą w procesie azotowania gazowego stali są: potencjał azotowy K N , stopień dysocjacji amoniaku α oraz rozporządzalność azotu m N2 . W artykule omówiono możliwości wykorzystania rozporzą-dzalności azotu atmosfery azotującej w projektowaniu procesów azotowania gazowego stali stopowych w atmosferach azotują-cych uzyskanych z amoniaku, z amoniaku rozcieńczonego zdysocjowanym amoniakiem, azotem oraz azotem i zdysocjowanym amoniakiem. Procesy azotowania wykonano w czterech seriach. Parametrami ustalonymi w poszczególnych seriach była temperatura procesu (T ), czas (t), wartość potencjału azotowego (K N ), któremu odpowiada określona wartość stopnia dysocjacji amoniaku zdysocjowanego podczas procesu azotowania (α). Parametrami zmiennymi była rozporządzalność azotu (m N2 ), skład atmosfery wlotowej i natężenie przepływu atmosfery azotującej wlotowej (F w ).

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In industrial applications of thermo-chemical treatments, gas nitriding is a widespread method of nitriding. Machine parts and tools of various shapes and sizes are nitrided, including drills, cutters, dies, shafts, rings, bearing balls, etc. often characterized by a complicated shape. The nitrided layers should have a controlled thickness not only of the diffusion zone, but also the surface layer of iron nitrides to have good exploitation properties. With a properly prepared surface on low alloy steels, we obtain a uniform nitrided layer after nitriding. It may happen that the structure of the nitrided layer is heterogeneous or even completely lacking in the nitrided parts having a complicated shape, and especially thin inner openings, where it is difficult to properly prepare the surface. Therefore, the nitriding problem is not the external surface of the workpieces but the internal one. The aim of the work was to assess the possibility of nitriding deep holes with small diameter. The tests were carried out on cylindrical specimens of unalloyed and low-alloy steel with electro-bored and mechanically hollow through holes and blind holes. The quality of the obtained nitrided layers was evaluated by metallographic and hardness examinations.