Estimation of Hydrogen Diffusivity in Austenitic Stainless Steels by Microhardness Gradient Technique

2011 ◽  
Vol 197-198 ◽  
pp. 696-700 ◽  
Author(s):  
Wen Bin Kan ◽  
Yong Feng Li ◽  
Hong Liang Pan
Keyword(s):  
Stainless Steels ◽  
Time Lag ◽  
Austenitic Stainless Steels ◽  
Hydrogen Diffusivity ◽  
Cross Sectional ◽  
Hardening Mechanism ◽  
Hydrogen Recombination ◽  
Microhardness Data ◽  
Gradient Technique ◽  
The One

The present study developed a subsurface microhardness gradient technique to estimate hydrogen diffusivity of stainless steels, as per the similarity between concentration distribution and hardness gradient. Cathodic charging were performed on 304 stainless steels for 24 h in a 0.5 mol/L H2SO4 solution using a current density of 100 mA/cm2, with 0.25g/L Na2S as the hydrogen recombination poison. Microhardness in the cross-sectional region had an increase than the uncharged materials due to the hardening mechanism as found by martensite transformation. Hydrogen diffusivity was estimated using the microhardness data and the diffusion equation. The estimated diffusivity of hydrogen at 306 K in 304 stainless steels is 3.28×10-13 m2/s, which has good agreements with the one measured by time-lag electrochemical method in a previous research.

XTEM microscopy of martensitic transformations in noble gas implanted stainless steel

1990 ◽  
Vol 48 (4) ◽  
pp. 206-207
Author(s):  
E. Johnson ◽  
A. Johansen ◽  
L. Sarholt-Kristensen ◽  
E. Gerritsen ◽  
J. Politiek ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stainless Steels ◽  
Solid Phase ◽  
Noble Gas ◽  
Thick Layer ◽  
Austenitic Stainless Steels ◽  
Martensitic Transformations ◽  
Cross Sectional ◽  
Transmission Electron

Cross-sectional transmission electron microscopy (XTEM) has been used to study the microstructure of noble gas implanted austenitic stainless steels, and in particular to analyse the depth distribution of implantation induced martensite in relation to the general radiation damage distribution.Large discs of low-austenitic stainless steels have been ion implanted with noble gases to fluences in the range l.1020 - 1.1021 m-2. Samples of the implanted discs for cross-sectional transmission electron microscopy (XTEM) were made by electroplating the implanted surface with a 3 mm thick layer of nickel, cutting 3 mm discs from the interface and electropolishing the discs to perforation using a Struers TENUPOL immersion jet apparatus.In samples implanted with low fluences (1-1020 m-2) the implantation zone consists of a heavily damaged top layer containing a dense distribution of microscopic noble gas inclusions, which are visible in defocusing phase contrast. The inclusions are ∽ 3-5 nm in diameter, and the smallest inclusions contain noble gas in the solid phase.

scholarly journals Overview of French Proposal of Updated Austenitic SS Fatigue Curves and of a Methodology to Account for EAF

2015 ◽  
Author(s):  
Thomas Métais ◽  
Stéphan Courtin ◽  
Pierre Genette ◽  
Laurent De Baglion ◽  
Cédric Gourdin ◽  
...  
Keyword(s):  
Environmental Effects ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Fatigue Curve ◽  
Penalty Factor ◽  
Asme Code ◽  
The Mean ◽  
The One

Environmentally Assisted Fatigue is receiving nowadays an increased level of attention not only for new builds but also for the installed bases which are currently having their lives extended to 60 years in various countries. To formally integrate these effects, some international codes have already proposed code cases. More specifically, the ASME code has used the NUREG/CR-6909 [1] as the basis for Code Case N-792 [2] and suggests a modification of the austenitic stainless steels fatigue curve combined with a calculation of an environmental penalty factor, namely Fen, which is to be multiplied by the usual fatigue usage factor. The various methodologies proposed are not finalized and there is still a significant level of discussion as can be illustrated by the recent update of NUREG/CR-6909 [3]. In this context, EDF, AREVA and the CEA have also submitted two RCC-M Rules in Probatory Phase (RPP) (equivalent to ASME code-cases) to AFCEN to propose respectively an update of the fatigue curve for austenitic stainless steels and a methodology to incorporate EAF in fatigue evaluations. The approach is globally similar to the one in the ASME code: it consists in an update of the mean air and design fatigue curves as well as the calculation of an environmental penalty factor. Nevertheless, the methodologies differ in their detailed implementation by especially introducing the Fen-integrated which accounts for the environmental effects already covered by the fatigue curves. This paper is the sequel to the proposal already described in [4] [6].

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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