scholarly journals The Effect of Cooling Rate on Structure of Nitrided Layer Formed in Austenitic Stainless Steels.

1995 ◽  
Vol 7 (1) ◽  
pp. 64
Author(s):  
Takao Ohtsuka ◽  
Kuniyasu Gemma ◽  
Mamoru Kawakami
Keyword(s):  
Cooling Rate ◽  
Stainless Steels ◽  
Nitrided Layer ◽  
Austenitic Stainless Steels

scholarly journals Microstructure/Mechanical Characterization of Plasma Nitrided Fine-Grain Austenitic Stainless Steels in Low Temperature

Nitrogen ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 244-258
Author(s):  
Abdelrahman Farghali ◽  
Tatsuhiko Aizawa ◽  
Tomoaki Yoshino
Keyword(s):  
Microstructure Evolution ◽  
Stainless Steels ◽  
Nitrided Layer ◽  
Austenitic Stainless Steels ◽  
Uniaxial Tensile ◽  
Two Phase ◽  
Solute Content ◽  
Fine Grained ◽  
Applied Loading ◽  
Uniaxial Tensile Testing

Fine-grained austenitic stainless steels (FGSS) were plasma nitrided below 700 K to describe their microstructure evolution during the nitrogen supersaturation process and to investigate the post-stressing effect on the microstructure and mechanical properties of nitrided FGSS. Normal- and fine-grained AISI304 plates were nitrided at 623 K and 673 K to investigate the grain size effect on the nitrogen supersaturation process as well as the microstructure evolution during the nitriding process. Fine-grained AISI316 (FGSS316) wires were nitrided at 623 K to demonstrate that their outer surfaces were uniformly nitrided to have the same two-phase, refined microstructure with high nitrogen solute content. This nitrided FGSS316 wire had a core structure where the original FGSS316 core matrix was bound by the nitrided FGSS316 layer. The nitrided wire had higher stiffness, ultimate strength, and elongation in the uniaxial tensile testing than its un-nitrided wires. The core microstructure was refined and homogenized by this applied loading together with an increase of nitrided layer hardness.

Improvement of Wear Resistances of AISI 316L Austenitic Stainless Steels by Anodic Nitriding

2012 ◽  
Vol 268-270 ◽  
pp. 269-274
Author(s):  
Yang Li ◽  
Liang Wang ◽  
Jiu Jun Xu ◽  
Ying Chun Shan
Keyword(s):  
Stainless Steel ◽  
Stainless Steels ◽  
316L Stainless Steel ◽  
Plasma Nitriding ◽  
Nitrided Layer ◽  
Austenitic Stainless Steels ◽  
Strengthening Effect ◽  
Aisi 316L ◽  
Discharge System ◽  
Hardness Tester

The nitriding of AISI 316L stainless steels has been carried out at anodic potential in a space enclosed by an active screen that consists of two cylinders with different diameter. These two cylinders made up a hollow cathode in a discharge system. Nitriding experiments were carried out on AISI 316L stainless steel at 450°C for times ranging from 1 to 24h in ammonia atmosphere. The intensity of electron bombardment on the surface of sample was low due to the anodic sheath, the disadvantages attached to conventional plasma nitriding were completely avoided. The phase composition, the thickness and the surface topography of the nitrided layer, as well as its hardness, were investigated by X-ray diffraction, scanning electron microscopy and a micro-hardness tester. The surface microhardness values and the thickness of the hardened layers increased as the nitriding time increased. Tribology properties of the untreated and nitrided 316L stainless steel have been investigated using a ball-on-disc tribometer with AISI52100 ball as the counterface. The results showed wear resistance of the AISI 316L stainless steels were greatly increased by anodic nitriding, owing to the strengthening effect of expanded austenite formed in the modified surface layer.

scholarly journals HARDNESS OF NITRIDED LAYERS TREATED BY PLASMA NITRIDING

2020 ◽  
Vol 27 ◽  
pp. 53-56
Author(s):  
Zdeněk Joska ◽  
Zdeněk Pokorný ◽  
Jaromír Kadlec ◽  
Zbyněk Studený ◽  
Emil Svoboda
Keyword(s):  
Mechanical Properties ◽  
Corrosion Resistance ◽  
Stainless Steels ◽  
Plasma Nitriding ◽  
Nitrided Layer ◽  
Surface Hardness ◽  
Austenitic Stainless Steels ◽  
Aisi 316L ◽  
Aisi 304 ◽  
Measurement Surface

Stainless steels, particularly the austenitic stainless grades are widely used in many industries due to good corrosion resistance, but very poor mechanical properties as surface hardness and wear resistance limit its possible use. Plasma nitriding is one of the few ways to increase the surface hardness of these steels, even though this will affect its corrosion resistance. This paper focuses on the description of the mechanical properties of nitrided layers in the two most widespread austenitic stainless steels AISI 304 and AISI 316L. The microstructure and properties of nitrided layers were evaluated by metallography and microhardness measurement. Surface properties of nitrided steels were characterized by Martens hardness. The results show that plasma nitriding created very hard nitrided layers with thickness about 40 μm and microhardness about 1300 HV0.05. Surface hardness measurements have shown that the maximum values for both steels are about 8.5 GPa, but have different behaviour under higher loads, when the AISI 316L nitrided layer began to crack on the surface and sink.

Delta Ferrite Formation in Austenitic Stainless Steel Castings

2012 ◽  
Vol 730-732 ◽  
pp. 733-738 ◽  
Author(s):  
Angelo Fernando Padilha ◽  
Caio Fazzioli Tavares ◽  
Marcelo Aquino Martorano
Keyword(s):  
Stainless Steel ◽  
Chemical Composition ◽  
Cooling Rate ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Magnetic Method ◽  
Empirical Formulas ◽  
Delta Ferrite ◽  
Ferrite Formation ◽  
Steel Castings

The effects of chemical composition and cooling rate on the delta ferrite formation in austenitic stainless steels have been investigated. Ferrite fractions measured by a magnetic method were in the range of 0 to 12% and were compared with those calculated by empirical formulas available in the literature. The delta ferrite formation (amount and distribution) was strongly affected by the steel chemical composition, but less affected by the cooling rate. Among several formulas used to calculate the amount of delta ferrite, the best agreement was obtained with those proposed independently by Schneider and Schoefer, the latter being recommended in the ASTM 800 standard.

scholarly journals Nitriding Process Characterization of Cold Worked AISI 304 and 316 Austenitic Stainless Steels

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Waldemar Alfredo Monteiro ◽  
Silvio Andre Lima Pereira ◽  
Jan Vatavuk
Keyword(s):  
Stainless Steels ◽  
Nitrided Layer ◽  
Cold Work ◽  
Austenitic Stainless Steels ◽  
Aisi 304 ◽  
Process Characterization ◽  
Aisi 304 Steel ◽  
Expanded Austenite ◽  
Cold Worked ◽  
Aisi 316

The nitriding behavior of austenitic stainless steels (AISI 304 and 316) was studied by different cold work degree (0% (after heat treated), 10%, 20%, 30%, and 40%) before nitride processing. The microstructure, layer thickness, hardness, and chemical microcomposition were evaluated employing optical microscopy, Vickers hardness, and scanning electron microscopy techniques (WDS microanalysis). The initial cold work (previous plastic deformations) in both AISI 304 and 306 austenitic stainless steels does not show special influence in all applied nitriding kinetics (in layer thicknesses). The nitriding processes have formed two layers, one external layer formed by expanded austenite with high nitrogen content, followed by another thinner layer just below formed by expanded austenite with a high presence of carbon (back diffusion). An enhanced diffusion can be observed on AISI 304 steel comparing with AISI 316 steel (a nitrided layer thicker can be noticed in the AISI 304 steel). The mechanical strength of both steels after nitriding processes reveals significant hardness values, almost 1100 HV, on the nitrided layers.

scholarly journals Study on the effect of nitrogen content and cooling rate on the ferrite number of austenitic stainless steels

2020 ◽  
Vol 7 (11) ◽  
pp. 270-277
Author(s):  
André de Albuquerque Vicente ◽  
Peter Aloysius D'silva ◽  
Sibi Sadanandan ◽  
Tiago Felipe de Abreu Santos ◽  
Jorge Alberto Soares Tenório
Keyword(s):  
Nitrogen Content ◽  
Cooling Rate ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Ferrite Number

Radiation Damage Studies with the HVEM

1972 ◽  
Vol 30 ◽  
pp. 680-681
Author(s):  
J. J. Laidler ◽  
B. Mastel
Keyword(s):  
Radiation Damage ◽  
Stainless Steels ◽  
Volume Expansion ◽  
Austenitic Stainless Steels ◽  
Test Facility ◽  
Fast Breeder Reactors ◽  
Breeder Reactors ◽  
Under Construction ◽  
Development Laboratory ◽  
Insight Into

One of the major materials problems encountered in the development of fast breeder reactors for commercial power generation is the phenomenon of swelling in core structural components and fuel cladding. This volume expansion, which is due to the retention of lattice vacancies by agglomeration into large polyhedral clusters (voids), may amount to ten percent or greater at goal fluences in some austenitic stainless steels. From a design standpoint, this is an undesirable situation, and it is necessary to obtain experimental confirmation that such excessive volume expansion will not occur in materials selected for core applications in the Fast Flux Test Facility, the prototypic LMFBR now under construction at the Hanford Engineering Development Laboratory (HEDL). The HEDL JEM-1000 1 MeV electron microscope is being used to provide an insight into trends of radiation damage accumulation in stainless steels, since it is possible to produce atom displacements at an accelerated rate with 1 MeV electrons, while the specimen is under continuous observation.

Strain-induced martensite effects on transgranular carbide precipitation in type 304 stainless steels

1991 ◽  
Vol 49 ◽  
pp. 604-605
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D. Matlock
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Deformation Twin ◽  
Austenitic Stainless Steels ◽  
Carbide Precipitation ◽  
Strain Induced Martensite ◽  
Type 304

Thermomechanically induced strain is a key variable producing accelerated carbide precipitation, sensitization and stress corrosion cracking in austenitic stainless steels (SS). Recent work has indicated that higher levels of strain (above 20%) also produce transgranular (TG) carbide precipitation and corrosion simultaneous with the grain boundary phenomenon in 316 SS. Transgranular precipitates were noted to form primarily on deformation twin-fault planes and their intersections in 316 SS.Briant has indicated that TG precipitation in 316 SS is significantly different from 304 SS due to the formation of strain-induced martensite on 304 SS, though an understanding of the role of martensite on the process has not been developed. This study is concerned with evaluating the effects of strain and strain-induced martensite on TG carbide precipitation in 304 SS. The study was performed on samples of a 0.051%C-304 SS deformed to 33% followed by heat treatment at 670°C for 1 h.

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