Plasma assisted nitriding for micro-texturing onto martensitic stainless steels*
Graduate School of Engineering, Shibaura Institute of Technology, 3-9-14 Shibaura, Minato-City, Tokyo
2 Department of Engineering and Design, Shibaura Institute of Technology, 3-9-14 Shibaura, Minato-City, Tokyo 108-8548, Japan
3 R & D Center, Sanko-Light Industries, Co. Ltd., 6-22-10 Uekotanaka, Nakahara-City, Kawasaki 211-0053, Japan
* e-mail: firstname.lastname@example.org
Accepted: 16 February 2015
Micro-texturing method has grown up to be one of the most promising procedures to form micro-lines, micro-dots and micro-grooves onto the mold-die materials and to duplicate these micro-patterns onto metallic or polymer sheets via stamping or injection molding. This related application requires for large-area, fine micro-texturing onto the martensitic stainless steel mold-die materials. A new method other than laser-machining, micro-milling or micro-EDM is awaited for further advancement of this micro-texturing. In the present paper, a new micro-texturing method is developed on the basis of the plasma assisted nitriding to transform the two-dimensionally designed micro-patterns to the three dimensional micro-textures in the martensitic stainless steels. First, original patterns are printed onto the surface of stainless steel molds by using the dispenser or the ink-jet printer. Then, the masked mold is subjected to high density plasma nitriding; the un-masked surfaces are nitrided to have higher hardness, 1400 Hv than the matrix hardness, 200 Hv of stainless steels. This nitrided mold is further treated by sand-blasting to selectively remove the soft, masked surfaces. Finally, the micro-patterned martensitic stainless steel mold is fabricated as a tool to duplicate these micro-patterns onto the plastic materials by the injection molding.
Key words: Micro-texturing / Plasma nitriding / Martensitic stainless steel / Mask-printing / Sand-blasting / Mold-die for injection molding
Implications and influences: The present paper has contribution to provide a new manufacturing method for micro-texturing of mold-dies with much reduction of leading time. This micro-textured molds are directly used for injection molding. Micro-patterned plastic cover cases for mobile phones are fabricated.
© T. Katoh et al., Published by EDP Sciences, 2015
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