Nitrogen Supersaturation Process in the AISI420 Martensitic Stainless Steels by Low Temperature Plasma Nitriding

Farghali, Abdelrahman; Aizawa, Tatsuhiko

doi:10.2355/isijinternational.isijint-2017-451

Cited by 27 publications

(22 citation statements)

References 34 publications

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“…Although detail information is not written in a few papers, relatively high-nitrogen surface content and formation of a nitrided layer with the thickness of 10-20 μm are common to those previous studies [31][32][33][34][35]. More precise analysis and discussion are needed to investigate the essential processes, governing the inner nitriding behavior at a lower temperature than 700 K. High-density RF-DC plasma systems [36][37][38][39][40] provides a new way to further analyze this low temperature plasma nitriding by experiments.…”

Section: Introductionmentioning

confidence: 99%

Low Temperature Plasma Nitriding of Austenitic Stainless Steels

Aizawa¹

2019

Stainless Steels and Alloys

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A low temperature plasma nitriding process has become one of the most promising methods to make solid-solution hardening by the nitrogen super-saturation, being free from toxicity and energy consumption. High-density radio-frequency and direct current (RF/DC) plasma nitriding process was applied to synthesize the nitrided AISI304 microstructure and to describe the essential mechanism of inner nitriding in this low temperature nitriding (LTN) process. In case of the nitrided AISI304 at 673 K for 14.4 ks, the nitrided layer thickness became 66.5 μm with the surface hardness of 1550 HV and the surface nitrogen content of 9 mass%. This inner nitriding process was governed by the synergetic interrelation among the nitrogen super-saturation, the lattice expansion, the phase transformation, the plastic straining, the microstructure refinement, and the acceleration of nitrogen diffusion. When this interrelation is sustained during the nitriding process, the original austenitic microstructure is homogeneously nitrided to have fine-grained microstructure with the average size of 0.1 μm. Once this interrelation does not work anymore, the homogeneous microstructure changed itself to the heterogeneous one. The plastic straining took place in the selected coarse grains so that the parts of them were only refined. This plastic localization accompanied with the localized phase transformation.

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Section: Introductionmentioning

confidence: 99%

Low Temperature Plasma Nitriding of Austenitic Stainless Steels

Aizawa¹

2019

Stainless Steels and Alloys

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“…In addition, the plastic straining was also induced to compensate for the strain 2 of 10 incompatibility between nitrogen saturated and unsaturated α'-lattices [13]. The original coarse grains were refined by this large plastic distortion so that the nitrogen supersaturated layer consisted of an α'-γ two-phase, fine-grained structure [14,15].…”

Section: Introductionmentioning

confidence: 99%

Microstructure of Plasma Nitrided AISI420 Martensitic Stainless Steel at 673 K

et al. 2019

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Martensitic stainless steel type AISI420 was plasma nitrided at 673 K for 3.6 ks to investigate the initial stage of the nitrogen supersaturation process without the formation of iron and chromium nitrides. SEM-EDX, electron back-scattering diffraction (EBSD), and TEM analyses were utilized to characterize the microstructure of the nitrided layer across the nitriding front end. The original coarse-grained, fully martensitic microstructure turned to be α’- γ two phase and fine-grained by high nitrogen concentration. Below this homogeneously nitrided layer, α’-grains were modified in geometry to be aligned along the plastic slip lines together with the α’ to γ-phase transformation at these highly strained zones. Most of these α’-grains in the two-phase microstructure had a nano-laminated structure with the width of 50 nm.

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“…This plasma nitriding at a lower temperature than 700 K was characterized by the nitrogen supersaturation; after [5], this processing was expected to be applied to various surface treatments such as carburizing and nitrocarburizing as the S-phase engineering. In addition, this nitrogen supersaturation process accompanied by two-phase nano-structuring to harden and strengthen the stainless steel parts and members as pointed in [8,9]. As demonstrated in [9][10][11], the corrosion toughness was also improved in these nitrogen supersaturated stainless steels.…”

Section: Introductionmentioning

confidence: 82%

“…Their deposition layer is often limited by several to 10 µm, and inner surfaces as well as holes are difficult to coat [4]. Among some candidate alternatives, low-temperature plasma nitriding has been highlighted to provide the thick nitrided layer up to 0.1 mm with higher hardness than 1200 HV and less nitride precipitates [5][6][7][8]. This plasma nitriding at a lower temperature than 700 K was characterized by the nitrogen supersaturation; after [5], this processing was expected to be applied to various surface treatments such as carburizing and nitrocarburizing as the S-phase engineering.…”

Section: Introductionmentioning

confidence: 99%

Low-Temperature Plasma Nitriding of Mini-/Micro-Tools and Parts by Table-Top System

Aizawa

Morita²,

Wasa

2019

Applied Sciences

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Miniature products and components must be surface treated to improve their wear resistance and corrosion toughness. Among various processes, low-temperature plasma nitriding was employed to harden the outer and inner surfaces of micro-nozzles and to strengthen the micro-springs. A table-top nitriding system was developed even for simultaneous treatment of nozzles and springs. A single AISI316 micro-nozzle was nitrided at 673 K for 7.2 ks to have a surface hardness of 2000 HV0.02 and nitrogen solute content up to 10 mass%. In particular, the inner and outer surfaces of a micro-nozzle outlet were uniformly nitrided. In addition, the surface contact angle increased from 40° for bare stainless steels to 104° only by low-temperature plasma nitriding. A stack of micro-nozzles was simultaneously nitrided for mass production. Micro-springs were also nitrided to improve their stiffness for medical application.

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Nitrogen Supersaturation Process in the AISI420 Martensitic Stainless Steels by Low Temperature Plasma Nitriding

Cited by 27 publications

References 34 publications

Low Temperature Plasma Nitriding of Austenitic Stainless Steels

Low Temperature Plasma Nitriding of Austenitic Stainless Steels

Microstructure of Plasma Nitrided AISI420 Martensitic Stainless Steel at 673 K

Low-Temperature Plasma Nitriding of Mini-/Micro-Tools and Parts by Table-Top System

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