Process And Mechanism Of Ion-nitriding Under The Atmosphere Of N₂ And N₂-NH₃

In this paper, alloy steel was nitrided under the atmosphere of pure nitrogen, using the ion nitriding technique by high voltage, low air pressure and holding heat with closed furnace, and alloy steel was also nitrided by normal techniques under the atmosphere of the different rate of N2 and NH3 . The hardness gradient, depth , microstructure and phases of nitrided layers were measured with Microhardness Apparatus, Microcopy and X-ray diffractometer . The result shows that under the same nitriding time, better experiment effects was achieved by using pure nitrogen than NH3, and the former technique overcomes the disadvantage of NH3 which is inclined to produce environmental pollutions.After the contrast studies of various techniques of pure nitrogen ion-nitriding , it is found that obvious ion-nitriding effects were achieved only on the condition of sufficiently high voltage. The behavior of molecule or ion around cathode zone on the process of ion nitriding was analyzed, In a mean free path, under the effect of the electric field, positive ion nitrogen has a inelastic collision with neutral nitrogen molecule and releases certain energy that received by the neutral nitrogen molecule, we quantitate this energy. Also we have found out the critical voltage needed in the production of active nitrogen atoms in ion-nitriding. Deduce the relation among the voltage, air pressure and the thickness of cathe zone. It presume the requirement of energy which produce the active nitrogen under some certain mixtured gases in theory, the theoretical quantitation is consistent weith the trial result of literature reports. Meanwhile, the effect of hydrogen and argon in the N2-H2 and N2-Ar ion-nitriding, and the mechanism of pure nitrogen ion nitriding was discussed .