8.4.3 Part Hardness The overall hardness of the part as determined by the original heat treatment used prior to any surface hardening and/or after surface hardening on a non-treated surface. 8.4.4 Process Stage A stage is a part of a process cycle, defined by temperature, time, atmosphere composition and nitriding potential. It shall differ from other stages by at least one of these parameters, except time, to be recognized as a stage.