NITROGEN AVAILABILITY OF NITRIDING ATMOSPHERE IN CONTROLLED GAS NITRIDING PROCESSES

Parameters which characterize the nitriding atmosphere in the gas nitriding process of steel are: the nitriding potential K-N, ammonia dissociation rate alpha 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 (alpha). Variable parameters were: nitrogen availability (m(N2)), composition of the ingoing atmosphere and flow rate of the ingoing atmosphere (F-In).