The Application of Analytical Electron Microscopy to Improving the Sensitization Resistance of Type 304 Stainless Steels

1985 ◽  
Vol 62 ◽  
Author(s):  
H. S. Betrabet ◽  
W. A. T. Clark
Keyword(s):  
Electron Microscopy ◽  
Stainless Steels ◽  
Volume Diffusion ◽  
Discontinuous Precipitation ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Analytical Electron ◽  
Type 304 ◽  
Kinetics Of ◽  
Apparent Conflict

ABSTRACTThe sensitization resistance of austenitic stainless steels can be improved by replacing some of the C with N. Electrochemical potentionkinetic reactivation (EPR) tests indicate that this is effective up to ∼0.16 wt.%N, but that above this level sensitization is enhanced. Thermodynamic calculations indicate that N should continue to reduce sensitization up to at least 0.25 wt.%N, as it retards the growth kinetics of Cr carbides. Analytical electron microscopy was used to investigate this apparent conflict and showed that, while N did decrease the volume diffusion coefficient of Cr beyond 0.16 wt.%, an increase in the amount of discontinuous precipitation of carbides with increasing N was responsible for the sensitization at higher N levels.

Origin and Influence of Pre-Existing Segregation on Radiation-Induced Segregation In Austenitic Stainless Steels

1998 ◽  
Vol 540 ◽  
Author(s):  
E. A. Kenik ◽  
J. T. Busby ◽  
M. K. Miller ◽  
A. M. Thuvander ◽  
G. Was
Keyword(s):  
Electron Microscopy ◽  
Grain Boundaries ◽  
Stainless Steels ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Atom Probe ◽  
Molecular Ions ◽  
Probe Field ◽  
Analytical Electron ◽  
Radiation Induced

AbstractThe pre-existing segregation at grain boundaries in two austenitic stainless steels has been investigated by atom probe field ion microscopy and analytical electron microscopy. In addition, the effect of radiation-induced segregation on the near-grain-boundary composition has been studied by analytical electron microscopy. Pre-existing enrichment of Cr, Mo, B, C and P and depletion of Fe and Ni near grain boundaries has been observed. Significant affinity between Mo and N in both alloys is indicated by the detection of MoN2+` molecular ions during field evaporation. The pre-existing segregation is modified by radiation-induced segregation resulting in Ni and Si enrichment near the boundary as well as depletion of chromium adjacent to the boundary resulting in a “W-shaped” Cr profile.

scholarly journals Application of Analytical Electron Microscopy to design of creep-resistant advanced austenitic stainless steels

1987 ◽  
Vol 45 ◽  
pp. 226-227
Author(s):  
P.J. Maziasz
Keyword(s):  
Electron Microscopy ◽  
Stainless Steels ◽  
Power Plants ◽  
Fine Particles ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
High Brightness ◽  
Aisi Type ◽  
Analytical Electron ◽  
Insight Into

Analytical electron microscopy (AEM) has been used for the last ten years to study precipitation produced in reactor-irradiated austenitic stainless steels, such as AISI type 316. These studies have provided the insight to design irradiation resistant steels based on control of precipitiation. More recently, similar insight into precipitation effects in steels allowed the design of advanced austenitics that also exhibit outstanding thermal creep resistance at 700°C. These steels have direct application for superheater/ reheater tubing materials that will withstand higher temperatures and stresses in advanced steam cycle fossil power plants.Fine particles (<10 nm in diam) on extraction replicas have been studied by AEM using a high brightness electron source to provide sufficient probe currents for reliable analyses. These studies allowed alloy compositional modifications to be selected that produced stable, fine precipitates for creep strength.

scholarly journals Micro-analytical studies of discontinuous precipitation in Fe-13.5 at.% Zn alloy

2020 ◽  
Vol 20 (3) ◽  
Author(s):  
Paweł Zięba ◽  
Mateusz Chronowski ◽  
Jerzy Morgiel
Keyword(s):  
Volume Diffusion ◽  
Discontinuous Precipitation ◽  
Analytical Electron Microscopy ◽  
Solute Concentration ◽  
Original Form ◽  
Left Behind ◽  
Analytical Electron ◽  
First Time ◽  
Zn Alloy ◽  
Boundary Diffusivity

Abstract For the first time, the analytical electron microscopy has been used to determine the solute concentration profiles left behind the moving reaction front (RF) of the discontinuous precipitation (DP) reaction in a Fe-13.5 at.% Zn alloy. These profiles have been converted into grain boundary diffusivity (sδDb) values, using Cahn’s diffusion equation in its original form and the data of the growth rate of the discontinuous precipitates obtained from independent measurements. This approach has essentially removed existing difference in comparison to sδDb values obtained from Cahn′s simplified and Petermann–Hornbogen models relevant for the global approach to the DP. Simultaneously, the local values of sδDb have been up to 8–10 orders of magnitude higher than the data for volume diffusion coefficients and much greater than for diffusion at the stationary grain boundaries of Zn in pure Fe. This is clear indication that the rate controlling factor for DP reaction in the Fe-13 at.% Zn alloy is diffusion at the moving RF.

scholarly journals Radiation-induced segregation in austenitic stainless steels

1991 ◽  
Vol 49 ◽  
pp. 556-557
Author(s):  
E. A. Kenik ◽  
K. Hojou
Keyword(s):  
Stainless Steels ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Test Facility ◽  
X Ray ◽  
Analytical Electron ◽  
Radiation Induced ◽  
Analysis System ◽  
Property Changes ◽  
Composition Fluctuations

Radiation-induced segregation (RIS) is driven by fluxes of point defects to sinks. RIS can induce composition fluctuations in irradiated stainless steels, which can result in microstructural and property changes, including precipitation, austenite instability, strengthening, embrittlement, and irradiation-assisted sensitization and stress corrosion cracking. Analytical electron microscopy (AEM) provides a powerful technique to study such segregation. RIS in several irradiated stainless steels has been investigated. AEM was performed in a Philips EM400T/FEG equipped with an EDAX 9100/70 analysis system. The specimens were neutron irradiated to 15 displacements per atom (dpa) at 520 ° C in the Fast Flux Test Facility (FFTF) and were only mildly radioactive (<50/μCi = 1.85 MBq), thus permitting high spatial resolution X-ray microanalysis to be employed. Typical acquisitions were performed for 100 s in the STEM mode with <2-nm-diam probes containing >0.5 nA current. Subtraction of “in-hole” spectra from the measured spectra corrected for both the normal “in-hole” counts and those associated with the radioactivity of the specimen.

Sensitization of Austenitic Stainless Steels, I. Controlled Purity Alloys

CORROSION ◽  
1982 ◽  
Vol 38 (9) ◽  
pp. 468-477 ◽  
Author(s):  
C. L. Briant ◽  
R. A. Mulford ◽  
E. L. Hall
Keyword(s):  
Carbon Content ◽  
Stainless Steels ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Carbide Formation ◽  
Beneficial Effects ◽  
Acid Etch ◽  
Parameter Versus ◽  
Type 304 ◽  
Sensitization Time

Abstract This paper presents a study of the effects of carbon, nitrogen, molybdenum, and manganese on the sensitization of high-purity austenitic stainless steels of composition similar to Type 304. The modified Strauss test (ASTM-A262-E), the oxalic acid etch test (ASTM-A262A) and analytical electron microscopy were used to determine the degree and nature of sensitization in the steels. The alloy compositions are considered in terms of effective chromium content, and from plots of this parameter versus sensitization time a strong effect of carbon content is seen. Additions of nitrogen, molybdenum, and manganese are found to delay sensitization at any given carbon concentration. In the case of nitrogen, the amount of improvement depends on both the carbon content and the sensitization temperature. Strong evidence is presented that nitrogen acts to retard the nucleation and/or growth of carbides at grain boundaries and hence increase the time necessary for sensitization. Molybdenum appears to increase the ease with which the steel passivates; thus more chromium depletion is required before sensitization will be detected. The combination of molybdenum plus nitrogen is found to be particularly effective in retarding nucleation and/or growth of carbides; molybdenum alone does not have this effect. Only limited experimental evidence is presented concerning the role of manganese. Beneficial effects of this element are primarily seen at low sensitizing temperatures, where manganese assists nitrogen in slowing carbide formation.

Growth of Lamellar Products During Discontinuous Solid State Reactions

1999 ◽  
Vol 580 ◽  
Author(s):  
P. Zieba ◽  
W. Gust
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Discontinuous Precipitation ◽  
Analytical Electron Microscopy ◽  
Morphological Features ◽  
Solid State Reactions ◽  
Analytical Electron ◽  
Nucleation Growth

AbstractThe nucleation, growth and dissolution of lamellar precipitates formed due to discontinuous solid state reactions like: discontinuous precipitation, coarsening and dissolution, are reviewed. Emphasis is given on recent studies based on analytical electron microscopy in describing the microchemistry, and in situ electron microscopy for revealing the morphological features of the reactions.

Precipitation at α/γ interfaces in duplex stainless steel

1992 ◽  
Vol 50 (1) ◽  
pp. 60-61
Author(s):  
M.G. Burke ◽  
E.A. Kenik
Keyword(s):  
Electron Microscopy ◽  
Stainless Steel ◽  
Grain Boundaries ◽  
Duplex Stainless Steel ◽  
Stainless Steels ◽  
Analytical Electron Microscopy ◽  
Nuclear Industry ◽  
Temperature Range ◽  
Α Phase ◽  
Analytical Electron

Duplex (austenite/ferrite) stainless steels are used in a variety of applications in the nuclear industry, particularly for coolant pipes, valves and pumps. These materials may become embrittled after prolonged ageing in the temperature range ∼350 - 550°C due to precipitation of G-phase, an FCC-based Ni silicide, and the formation of a Cr-rich α' phase in the ferrite. In addition to the intragranular G-phase precipitates, preferential precipitation of other phases is often observed at grain boundaries, particularly α/γ interfaces. In this examination, the precipitates formed in a Nb-containing duplex stainless steel have been identified using analytical electron microscopy.

Electron Beam Damage of Biomolecules Assessed by Energy Loss Spectroscopy

1978 ◽  
Vol 36 (3) ◽  
pp. 61-69
Author(s):  
M. Isaacson ◽  
M.L. Collins ◽  
M. Listvan
Keyword(s):  
Electron Microscopy ◽  
Radiation Damage ◽  
Structural Integrity ◽  
Analytical Electron Microscopy ◽  
High Dose ◽  
Dose Rates ◽  
Special Cases ◽  
Analytical Electron ◽  
Atom Migration ◽  
Beam Damage

Over the past five years it has become evident that radiation damage provides the fundamental limit to the study of blomolecular structure by electron microscopy. In some special cases structural determinations at very low doses can be achieved through superposition techniques to study periodic (Unwin & Henderson, 1975) and nonperiodic (Saxton & Frank, 1977) specimens. In addition, protection methods such as glucose embedding (Unwin & Henderson, 1975) and maintenance of specimen hydration at low temperatures (Taylor & Glaeser, 1976) have also shown promise. Despite these successes, the basic nature of radiation damage in the electron microscope is far from clear. In general we cannot predict exactly how different structures will behave during electron Irradiation at high dose rates. Moreover, with the rapid rise of analytical electron microscopy over the last few years, nvicroscopists are becoming concerned with questions of compositional as well as structural integrity. It is important to measure changes in elemental composition arising from atom migration in or loss from the specimen as a result of electron bombardment.

Analytical Electron Microscopy (AEM) of Meningeal Cells Exposed to Particulate Cobalt During Studies of Experimental Epilepsy

1982 ◽  
Vol 40 ◽  
pp. 186-187
Author(s):  
R.G. Frederickson ◽  
R.G. Ulrich ◽  
J.L. Culberson
Keyword(s):  
Electron Microscopy ◽  
Analytical Electron Microscopy ◽  
Experimental Epilepsy ◽  
Metallic Cobalt ◽  
Experimental Animals ◽  
X Ray ◽  
Brain Surface ◽  
Meningeal Cells ◽  
Analytical Electron ◽  
The Brain

Metallic cobalt acts as an epileptogenic agent when placed on the brain surface of some experimental animals. The mechanism by which this substance produces abnormal neuronal discharge is unknown. One potentially useful approach to this problem is to study the cellular and extracellular distribution of elemental cobalt in the meninges and adjacent cerebral cortex. Since it is possible to demonstrate the morphological localization and distribution of heavy metals, such as cobalt, by correlative x-ray analysis and electron microscopy (i.e., by AEM), we are using AEM to locate and identify elemental cobalt in phagocytic meningeal cells of young 80-day postnatal opossums following a subdural injection of cobalt particles.

Sign in / Sign up

Export Citation Format

Share Document