Low temperature high density plasma nitriding of stainless steel molds for stamping of oxide glasses

Abstract

-Various kinds of stainless steels have been widely utilized as a die for mold-and direct-stamping processes of optical oxide glasses. Since they suffered from high temperature transients and thermal cycles in practice, they must be surface-treated by dry and wet coatings, or, by plasma nitriding. Martensitic stainless steel mold was first wet plated by the nickel phosphate (NiP), which was unstable at the high temperature stamping condition; and, was easy to crystalize or to fracture by itself. This issue of nuisance significantly lowered the productivity in fabrication of optical oxide-glass elements. In the present paper, the stainless steel mold was surface-treated by the low-temperature plasma nitriding. The nitrided layer by this surface modification had higher nitrogen solute content than 4 mass%; the maximum solid-solubility of nitrogen is usually 0.1 mass% in the equilibrium phase diagram. Owing to this solidsolution with high nitrogen concentration, the nitrided layer had high hardness over 1400 HV within its thickness of 50 lm without any formation of nitrides after plasma nitriding at 693 K for 14.4 ks. This plasma-nitrided mold was utilized for mold-stamping of two colored oxide glass plates at 833 K; these plates were successfully deformed and joined into a single glass plate by this stamping without adhesion or galling of oxide glasses onto the nitrided mold surface.

The effect of RF-DC plasma N2-H2 in the selective hardening process for micro-patterned AISI420

“…Besides for the original α'-Fe peak at 2θ = 44.7 o (cubic space group), a new peak was detected around 40 o < 2θ < 45 o at 2θ = 43.52 o (trigonal-hexagonal axes space group). This peak is related to the extended martensitic lattice by high nitrogen extraordinary solid solution just as stated in [1] and [17]. Structure of the α'-Fe and ε-Fe 3 N was shown in Figure 5.…”

“…The results of lattice parameters of the crystal structure detailed are presented in Table 3-5. After [1], no nitrides were synthesized in the lower temperature plasma nitriding; the nitrogen atoms were present as a solute in the Fe/Cr lattices by occupying their vacancy sites. …”

“…In [1,[4][5][6], the non-traditional processing was proposed to make micro-texturing into dies and molds with aid of the high density RF-DC Plasma N 2 -H 2 . The original two dimensional micro-patterns are directly drawn onto the mold and die surfaces.…”

“…The case-hardened AISI420 martensitic stainless steels, graded by STAVAX in commercial is used as a mold for injection molding [1]. Micro-and nano-textures on the metal and polymer surfaces of parts and components have functions to reduce the friction and wear in [2] and to improve the joining strength in [3].…”

Low Temperature Plasma Nitriding of Inner Surfaces in Stainless Steel Mini-/Micro-Pipes and Nozzles

“…High-density plasma nitriding has been used for hardening metals and alloys such as stainless steels, tool steels, and titanium and aluminum alloys with the use of DC-biased metallic tubes (referred to here as hollow-cathode devices) [ 3 , 4 , 5 , 6 ]. In these processes, these metallic alloy parts and components are efficiently plasma-nitrided in hollow-cathode devices.…”