In order to study the nitriding behavior of pulse ion nitriding on the outer surface and inner surface of hole, SACM1 specimens with hole diameters of 3 mm, 4 mm, 5 mm were nitrided at 500℃ for 6hours. The efficiency of nitride layer formation and the penetration depth with various hole diameters were compared between pulse and D.C. ion nitriding.
Faster growth rate of nitride layer was fostered on the outer surface of hole by D.C. ion nitriding while on the inner surface of hole by pulse ion nitriding. The above distinguished phenomena could be explained by virtures of the differences in ionization rate and the hollow cathode discharge caused by D.C. and pulse ion nitriding.
Deeper penetration depthes in holes were obtained by the pulse ion nitriding than by D.C. ion nitriding. From the plot of ( penetration depth )/ ( hole diameter ) vs. hole diameter, the slope was 1.7 in pulse ion nitriding and 2.8 in D.C. ion nitriding respectively. And the penetration depth was considered to be deeply related with H.C.D. effect.
The uniformity of nitride layer was also affected by the size of hole diameter and the mode of ion nitriding. The pulse ion nitriding showed better uniformity in small holes than the D.C. ion nitriding.
