Microtexturing Into AISI-SUS420 Molds for Injection Molding Via Plasma Nitriding

Abstract

The initial microdot and microline patterns were first ink-jet printed onto the surface of polished AISI420 stainless steel mold. This masked mold substrate was nitrided at 693 K for 7.2 ks at 70 Pa by using the high-density plasma nitriding system. The unmasked parts were selectively nitrided to have higher hardness than 1200 HV. This hardness-profiled substrate was mechanically sand-blasted to fabricate the microtextured mold. Microdisk patterned plastic cover-case for cellular phones were injection-molded by using this method for practical demonstration. Both the selective hardening and anisotropic inner nitriding processes were experimentally discussed as a key step in the present processing.