  The high density of RF-DC plasma N2-H2 was used to make precise
micro-texturing onto AISI420 has complex textured geometry. The original 2D
micro-patterns were drawn onto substrate surface by maskless patterning using
by of nano-carbon ink. These micro-patterned specimens were further
plasma-nitrided at 673 K for 5.4 ks by 70 Pa using the hollow cathode device.
The emissive light spectroscopy shows species in plasma were nitrogen atoms
together with NH radicals and nitrogen molecular ions. Unprinted surface areas
had selectively nitrided, have high nitrogen solute contents up to 12 mass%.
Masked area just corresponded to carbon-mapping from printed nano-carbon inks,
while unprinted surface to nitrogen mapping. The hardness profile had stepwise
change across the borders between these printed and unprinted areas; e.g., the
hardness on unprinted surface was 1200 Hv while it remained to be 350 Hv on
printed surface. This selective nitriding and hardening enabled to construct
the 3D textured miniature dies and products by chemical etching of printed
area. These two peaks were related to extended martensitic lattice by high
nitrogen extraordinary solid solution. The phase transformation from
martensitic lattice {\alpha}prime-Fe through expanded phase into
{\epsilon}-Fe3N lattice.
