maskless patterning
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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 α’-Fe through expanded phase into ε-Fe3N lattice.

The plasma printing was used to make precise micro-texturing into the stainless steels to have complex textured geometry. First in this plasma printing, the original two dimensional micro-patterns were drawn onto the substrate surface by the maskless patterning with use of the nano-carbon ink. These micro-patterned specimens were further plasma-nitrided at 673 K for 5.4 ks by 70 Pa with use of the hollow cathode device. The unprinted surface areas were selectively nitrided to have high nitrogen solute contents up to 12 mass%. The masked area just corresponded to the carbon-mapping from the printed nano-carbon inks, while the unprinted surface, to the nitrogen mapping. The hardness profile had stepwise change across the borders between these printed and unprinted areas; e.g., the hardness on the unprinted surface was 1200 Hv while it remained to be 350 Hv on the printed surface. This selective nitriding accompanied with the selective hardening. This selective nitriding enabled us to construct the three dimensionally textured miniature dies and products by chemical etching of the printed area.