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1.
P. Muraleedharan H. S. Khatak J. B. Gnanamoorthy P. Rodriguez 《Metallurgical and Materials Transactions A》1985,16(1):285-289
The influence of cold work (prestraining) in the range 2.3 to 56 pct on stress corrosion cracking (SCC) properties of types
304 and 316 stainless steels in boiling MgCl2 solution at 154 °C was investigated using a constant load method. In both materials,
SCC initiation was in transgranular mode. Transition in stress corrosion cracking mode from transgranular to intergranular,
as the crack proceeds, was observed at all cold work levels in 316 stainless steel and at cold work levels of 26 pct and 56
pct in 304 stainless steel. Both prestraining and increase in the initial applied stress facilitated the transition in crack
morphology to intergranular mode. Increased tendency to intergranular SCC at high applied stresses and in cold worked specimens
appears to be mechanistically analogous. 相似文献
2.
3.
U. Kamachi Mudali R. K. Dayal J. B. Gnanamoorthy P. Rodriguez 《Metallurgical and Materials Transactions A》1996,27(10):2881-2887
Intergranular corrosion (IGC) resistance of types 304LN and 316LN stainless steels (SS) thermally aged at 823, 873, and 923
K for various durations was assessed by ASTM A262 practice A test (electrolytic etch test) and electrochemical potentiodynamic
reactivation (EPR) test. The results indicated that the type 316LN SS has significantly improved IGC resistance compared to
304LN SS. Based on the results of these tests, time-temperature-sensitization (TTS) diagrams were developed for both alloys.
The secondary precipitates formed during thermal aging treatments were electrochemically extracted and analyzed by X-ray diffraction
(XRD) to determine the types of precipitates formed during the aging treatments. The results indicated that the precipitates
were mostly of M23C6 carbides. 相似文献
4.
R. F. Hehemann 《Metallurgical and Materials Transactions A》1985,16(11):1909-1923
The similarities and differences in the stress corrosion cracking response of ferritic and austenitic stainless steels in
chloride solutions will be examined. Both classes of materials exhibit a cracking potential: similar transient response (to
loading) of the potential in open circuit tests or the current in potentiostatic tests and similar enrichment of chromium
and depletion of iron in the film associated with localized corrosion processes. The ferritic steels are more resistant to
localized corrosion than are the austenitic steels, which is responsible for the difference in the influence of prior thermal
and mechanical history on cracking susceptibility of the two types of steel. Similarities in the fractography of stress corrosion
cracks and those produced by brittle delayed failure during cathodic charging of the ferritic steels indicate that hydrogen
embrittlement is involved in the failure process. 相似文献
5.
6.
The sensitization behavior of types 308 and 316 stainless steel weld metals as internal overlays for reactor pressure vessels
(RPVs) was studied with respect to the effects of postweld heat treatment (PWHT) at about 600 °C during RPV fabrication and
low-temperature aging during operation. For the study, a criterion for the rate of intergranular corrosion (IGC) for detecting
the susceptibility to intergranular stress corrosion cracking (IGSCC) in high-temperature oxygenated pure water was established
by quantitatively evaluating the results from a modified ASTM A262E test. A criterion for expecting satisfactory resistance
to IGSCC was found to be an IGC rate of about 1 μm/h. Type 308 weld metal can be sensitized as indicated by an IGC rate >1 μm/h, and can be healed, as indicated by an IGC rate <1 μm/h, depending on the length of PWHT. However, this healed weld metal can be resensitized by exposing it to 500 °C×24 h; in
this condition, it shows a relatively high susceptibility to IGSCC. On the contrary, type 316 weld metal was almost immune
to sensitization under the same heat treatments. By transmission electron microscopy (TEM), its excellent resistance was attributable
to carbon fixation by molybdenum carbide precipitation within ferrite phases during PWHT. Reheat embrittlement of type 316
weld metal was also examined. 相似文献
7.
W. A. Baeslack W. F. Savage D. J. Duquette 《Metallurgical and Materials Transactions A》1979,10(10):1429-1435
The influence of strain-rate on the stress-corrosion cracking properties of wholly austenitic Type 304 base metal and duplex
austeno-ferritic Type 304 weld metal in boiling MgCl2 was investigated using constant extension rate tensile testing techniques. Transgranular SCC in both base and weld metals
is preferred at low strain-rates, while intergranular cracking in the base metal and interphase cracking along the austenite-ferrite
interface in the weld metal are preferred at higher strain-rates. Promotion of the intergranular stress-corrosion cracking
in the base metal and “interphase-interface” stresscorrosion cracking in the weld metal with increases in strain-rate may
be mechanistically analogous. Stress-induced alterations in the grain or interphase boundary defect structure may make these
regions preferentially susceptible to dissolution.
W. A. BAESLACK III, Lt., USAF, formerly with Rensselaer Polytechnic Institute, Troy, New York 相似文献
8.
S. Jani M. Marek R. F. Hochman E. I. Meletis 《Metallurgical and Materials Transactions A》1991,22(6):1453-1461
Transmission electron microscopy (TEM) was utilized to characterize the deformation substructure of 304 stainless steel tested
for transgranular stress corrosion cracking (TGSCC) in 45 wt pet MgCl2 at 155 °C. The TEM characterization was conducted in thin foils prepared from the fracture surface and from a series of known
depths below the fracture surface. The results indicate that the stacking fault energy (SFE) of the material immediately ahead
of the crack tip is lowered, with the deformation mode at small distances (a few microns) in front of the growing crack front
being entirely coplanar while at larger distances homogeneous. The reduction in the SFE is attributed to absorbed hydrogen
formed during the cathodic reaction. Based on this and previous observations of transgranular stress corrosion characteristics
of aus-tenitic stainless steels in chloride environments, a “hydrogen-induced cleavage” model is proposed. This model is essentially
a modification of a model based on enhanced structural reactivity associated with Lomer-Cottrell locks proposed by Robertson
and Tetelmann in 1962.27 相似文献
9.
This paper reports a study of grain boundary segregation, intergranular corrosion, and intergranular stress corrosion cracking
in austenitic stainless steels. The results show that phosphorus, nitrogen, and sulfur all segregate to grain boundaries in
these materials and that they can affect one another's segregation through site compctition. In particular, the results demonstrate
that phosphorus segregation can be lowered by the presence of nitrogen and sulfur in the steel. Also, if manganese is present
in the steel, sulfur segregation will be greatly decreased as a result of formation of manganese sulfides. Phosphorus, sulfur,
and nitrogen will not initiate intergranular corrosion in the modified Strauss test, although if corrosion is initiated by
chromium depletion, these elements might enhance the corrosion process. Phosphorus segregation does enhance corrosion in the
Huey test, even in steels that have not undergone grain boundary chromium depletion, although there does not appear to be
a precise correlation between the depth of corrosion penetration and phosphorus segregation. Intergranular stress corrosion
cracking in 288 °C water at a pH of 2.5 and electrochemical potential of OVSHE can occur in these steels even in the absence of chromium depletion if sulfur is present on the grain boundaries. Phosphorus
segregation appears to have very little effect. 相似文献
10.
Markus O. Speidel 《Metallurgical and Materials Transactions A》1981,12(5):779-789
The metallurgical influences on the stress corrosion resistance of many commercial stainless steels have been studied using
the fracture mechanics approach. The straight-chromium ferritic stainless steels, two-phase ferritic-austenitic stainless
steels and high-nickel solid solutions (like alloys 800 and 600) investigated are all fully resistant to stress corrosion
cracking at stress intensity (K1) levels ≤ MN • m-3/2 in 22 pct NaCl solutions at 105 °C. Martensitic stainless steels, austenitic stainless steels and precipitation hardened
superalloys, all with about 18 pct chromium, may be highly susceptible to stress corrosion cracking, depending on heat treatment
and other alloying elements. Molybdenum additions improve the stress corrosion cracking resistance of austenitic stainless
steels significantly. The fracture mechanics approach to stress corrosion testing of stainless steels yields results which
are consistent with both the service experience and the results from testing with smooth specimens. In particular, the well
known “Copson curve” is reproduced by plotting the stress corrosion threshold stress intensity (ATISCC) vs the nickel content of stainless steels with about 18 pct chromium.
Formerly with the BBC Brown Boveri Company, Baden, Switzerland 相似文献
11.
Corrosion fatigue and stress corrosion cracking of type 304 stainless steel in boiling NaOH solution
Antwi Boateng James A. Begley R. W. Staehle 《Metallurgical and Materials Transactions A》1979,10(8):1157-1164
Results are reported for corrosion fatigue of Type 304 stainless steel in boiling (140 C) 17.5M NaOH (46 wt pct) solution.
Specimens, of the smooth round bar type, were cycled sinusoidally at 1.0 Hz in tension-tension about mean stresses of 248
MPa (36 ksi) and 124 MPa (18 ksi). Both solution annealed and sensitized specimens cracked readily in a transgranular mode.
Sensitization did not increase the environmental effect. The caustic solution drastically shortened cyclic life and eliminated
the endurance limit observed in air. Cyclic stress was a more important variable than mean stress as the lower mean stress
did not significantly improve life. Anodic passivation did not increase cyclic life as it did for constant load SCC. Comparison
of the SCC tests results with those of corrosion fatigue indicates that cyclic stresses, even when confined to the elastic
region, accelerate failure more than sustained loads in the plastic region; this accelerative effect was most intense under
anodic passivation.
R. W. STAEHLE, formerly Professor of Metallurgical Engineering, and Director of The Fontana Corrosion Center, Ohio State University 相似文献
12.
Microstructural effects on the stress corrosion cracking behavior of medium and high strength steels
R. Kerr F. Solana I. M. Bernstein A. W. Thompson 《Metallurgical and Materials Transactions A》1987,18(13):1011-1022
The effects of variations in microstructure and strength level on the stress corrosion cracking susceptibility of three medium to high strength steels, H13, 300M, and HY-130, in 3.5 pct NaCl have been systematically studied. Superimposed on the expected inverse dependence of KISCC on yield strength was more than an order of magnitude reduction in crack growth rate, with no strength penalty. These results have been analyzed in terms of the possible relative roles of different microstructural features, in particular retained austenite, whose detailed behavior is the subject of a companion paper. 相似文献
13.
Microstructural effects on the stress corrosion cracking behavior of medium and high strength steels
Kerr R. Solana F. Bernstein I. M. Thompson A. W. 《Metallurgical and Materials Transactions A》1987,18(6):1011-1022
Metallurgical and Materials Transactions A - The effects of variations in microstructure and strength level on the stress corrosion cracking susceptibility of three medium to high strength steels,... 相似文献
14.
Microstructural effects on the stress corrosion cracking behavior of medium and high strength steels
R. Kerr F. Solana I. M. Bernstein A. W. Thompson 《Metallurgical and Materials Transactions A》1991,22(1):1011-1022
The effects of variations in microstructure and strength level on the stress corrosion cracking susceptibility of three medium
to high strength steels, H13, 300M, and HY-130, in 3.5 pct NaCl have been systematically studied. Superimposed on the expected
inverse dependence of KISCC on yield strength was more than an order of magnitude reduction in crack growth rate, with no strength penalty. These results
have been analyzed in terms of the possible relative roles of different microstructural features, in particular retained austenite,
whose detailed behavior is the subject of a companion paper. 相似文献
15.
The effects of cold working on sensitization and intergranular corrosion behavior of AISI 304 stainless steel 总被引:1,自引:0,他引:1
Raghuvir Singh I. Chattoraj A. Kumar B. Ravikumar P. K. Dey 《Metallurgical and Materials Transactions A》2003,34(11):2441-2447
The effects of prior cold rolling of up to an 80 pct reduction in thickness on the sensitization-desensitization behavior
of Type AISI 304 stainless steel and its susceptibility to intergranular corrosion have been studied by electrochemical potentiokinetic
reactivation (EPR) and Strauss-test methods. The results indicate that the prior deformation accelerated the sensitization
as compared to the undeformed stainless steel. The deformed Type 304 stainless steel experienced desensitization at higher
temperatures and times, and it was found to be enhanced by increased cold deformation. This could be attributed to the increased
long-range chromium diffusion, possibly brought on by increasing pipe diffusion and vacancies. The role of the deformation-induced
martensite (DIM) and texture, introduced by uniaxial cold rolling, on the sensitization-desensitization kinetics has also
been discussed. This study could not reveal any systematic relationship between texture and the degree of sensitization (DOS)
obtained. The effect of DIM on DOS seems to be pronounced at 500 °C when the steel retained significant amounts of DIM; however,
the retained DIM is insignificant at higher sensitization times and temperatures. 相似文献
16.
Deformation-induced martensitic characteristics in 304 and 316 stainless steels during room-temperature rolling 总被引:1,自引:0,他引:1
Vijay Shrinivas S. K. Varma L. E. Murr 《Metallurgical and Materials Transactions A》1995,26(3):661-671
The effect of grain size on the deformation-induced martensite (α′) in 304 and 316 stainless steels (SS) during room-temperature
rolling has been studied. Samples of four grain sizes of 52, 180, 229, and 285 μ in 304 and three grain sizes of 77, 125,
and 200 /μm in 316 SS have been rolled from 16 to 63 pct reduction in thicknesses to characterize the microstructures during
the rolling deformation. The amount of α′ formed increases with increase in the amount of deformation in both SS for a given
grain size. The volume fraction of martensite formed increases with a decrease in grain size in 304 SS, while the α’ martensite
formation has been found to be grain size insensitive in 316 SS. The volume fraction of α’ formed in 304 SS is always higher
than that in 316 SS for a fixed percent reduction in thickness and grain size. This is attributed to the higher number of
shear band intersections observed in 304 SS, which are considered to be the nucleation sites for the α’ embryos. The lath
martensite obtained at small true rolling strains changes to blocky type at higher true strains. The morphology of α′ formed
has been discussed and its characteristics obtained from rolling deformation have been compared with those earlier reported
from the room-temperature tensile deformation. 相似文献
17.
G. Sasikala S. L. Mannan M. D. Mathew K. Bhanu Rao 《Metallurgical and Materials Transactions A》2000,31(4):1175-1185
The creep properties of a nuclear-grade type 316(L) stainless steel (SS) alloyed with nitrogen (316L(N) SS) and its weld metal
were studied at 873 and 923 K in the range of applied stresses from 100 to 335 MPa. The results were compared with those obtained
on a nuclear-grade type 316 SS, which is lean in nitrogen. The creep rupture lives of the weld metals were found to be lower
than those of the respective base metals by a factor of 5 to 10. Both the base and weld metals of 316L(N) SS exhibited better
resistance to creep deformation compared to their 316 SS counterparts at identical test conditions. A power-law relationship
between the minimum creep rate and applied stress was found to be obeyed for both the base and weld metals. Both the weld
metals generally exhibited lower rupture elongation than the respective base metals; however, at 873 K, the 316 SS base and
weld metals had similar rupture elongation at identical applied stresses. Comparison of the rupture lives of the two steels
to the ASME curves for the expected minimum stress to rupture for 316 SS base and weld metals showed that, for 316L(N) SS,
the specifications for maximum allowable stresses based on data for 316 SS could prove overconservative. The influence of
nitrogen on the creep deformation and fracture behavior, especially in terms of its modifying the precipitation kinetics,
is discussed in light of the microstructural observations. In welds containing δ ferrite, the kinetics of its transformation
and the nature of the transformation products control the deformation and fracture behavior. The influence of nitrogen on
the δ ferrite transformation behavior and coarsening kinetics is also discussed, on the basis of extensive characterization
by metallographic techniques. 相似文献
18.
The effects of tempering temperature and carbon content on the stress corrosion cracking (SCC) behavior of high-strength CrMo
steels in 3.5 pct NaCl aqueous solution have been studied by means of Auger electron spectroscopy (AES) and scanning and transmission
electron micros- copy (SEM and TEM). Experimental results show that the specimens with higher carbon content and tempered
at lower temperatures have a higher tendency for intergranular fracture and lower threshold stress intensity KISCC The SCC behavior is significantly affected by the distribution of carbide particles, especially carbide coverage on prior
austenitic grain boundaries, through a carbide-matrix interface mechanism as the interface is the preferential site for the
nucleation and propagation of microcracks because of its strong ability to trap hydrogen atoms. In low- temperature tempered
states, there is the serious segregation of carbon in the form of carbide particles at prior austenitic grain boundaries,
causing low-stress intergranular fracture. After tempering at high temperatures (≥400 °C), both the coalescence of the carbide
particles at the grain boundaries and the increase of carbide precipitation within grains cause the decrease of the tendency
for intergranular fracture and the rise of KISCC. The higher the carbon content in steels, the more the carbide particles at the grain boundaries and, subsequently, the higher
the tendency for low-stress intergranular fracture. The carbide effect on KISCC makes an important contribution to the phenomenon that KISCC decreases with the rise of yield strength of the steels. 相似文献
19.
A. Chambreuil-Paret Ph.D. T. Magnin 《Metallurgical and Materials Transactions A》1999,30(5):1327-1331
Austenitic stainless steels are known to be sensitive to stress corrosion cracking (SCC) in hot chloride solutions. The aim
of the present study is to find improvements in the SCC behavior of 316L-type austenitic stainless steels in 117°C MgCl2 solutions. Previously, the authors have proposed the “corrosion-enhanced plasticity model” (CEPM) to describe the discontinuous
cracking process which occurs in SCC. This model is based on localized corrosion (anodic dissolution, and hydrogen absorption)-deformation
(dislocations) interactions (CDI). From the framework of this model, it is proposed that a prestraining in fatigue at saturation
decreases the SCC sensitivity. This idea is experimentally confirmed for both crack initiation and crack propagation, through
the analysis of the SCC behavior by slow-strain-rate tests of single and polycrystals after different prestraining conditions. 相似文献
20.
采用恒应力强度因子K=33 MPa·m1/2的加载方法,利用直流电压降方法在线监测核辅管道316L不锈钢在高纯水中应力腐蚀裂纹扩展速率.对比200、250、280和325℃温度下,氩气除氧和含有2 mg·L-1溶解氧的水化学环境中材料的裂纹扩展速率发现:溶解氧为2 mg·L-1时的裂纹扩展速率明显比氩气除氧时的裂纹扩展速率高.氩气除氧时,裂纹扩展速率在250℃时有一个最高点;溶解氧为2 mg·L-1的条件下,裂纹扩展速率随温度的升高而升高. 相似文献