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1.
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
2.
Hydrogen-facilitated corrosion and stress corrosion cracking of austenitic stainless steel of type 310 总被引:2,自引:0,他引:2
Qiao Lijie Chu Wuyang Miao Huijun Xiao Jimei Guo Peixin 《Metallurgical and Materials Transactions A》1993,24(4):959-962
The effects of hydrogen précharge and stress on anodic dissolution for Type 310 austenitic stainless steel (ASS) have been
investigated. An experiment determining the effect of hydrogen on stress corrosion cracking (SCC) was carried out in a boiling
42 pct MgCl2 solution and in a 2.5 mo/L H2SO4 + 1 mol/L HC1 solution. The results showed that both hydrogen and stress would increase the dissolution rate, and the effects
of hydrogen and stress on the dissolution rate were synergistic rather than simply additive. Hydrogen lowered the threshold
stress and the shortened fracture time of SCC in a boiling MgCl2 solution by a factor of 1/5 and 10, respectively. 相似文献
3.
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
4.
The solidification behavior of three heats of nitrogen-strengthened austenitic stainless steel was examined and was correlated
with solidification mode predictions and with hot cracking resistance. The heat of NITRONIC* 50 solidified by the austenitic-ferrite
mode, and the NITRONIC 50W and NITRONIC 50W - Nb heats solidified by the ferritic-austenitic mode. This behavior was in good
agreement with predictions based on Espy’s formulas for Cr and Ni equivalents. Both the NITRONIC 50W and NITRONIC 50W + Nb
welds contained primary delta-ferrite, with the latter weld and the NITRONIC 50 weld also containing some eutectic ferrite.
Solute profiles in austenite near the eutectic ferrite showed decreasing Fe and increasing Cr, Ni, Mn, and Mo relative to
austenite in the dendrite cores. Numerous Nb-rich precipitates were found on the eutectic ferrite/austenite interfaces and
within the eutectic ferrite. The precipitates were mainly Nb(C, N), with some Z-phase, a Nb-rich nitride, also detected. One
instance of the transformation of eutectic ferrite to sigma-phase was observed to have occurred during cooling of the NITRONIC
50 weld. Hot cracking was seen in the NITRONIC 50 and NITRONIC 50W + Nb welds and resulted from the formation of a niobium
carbonitride eutectic in the interdendritic regions. In the absence of Nb, the NITRONIC 50W heat formed no observable eutectic
constituents and did not hot crack. The presence of hot cracks in the NITRONIC 50W + Nb weld indicates that solidification
by the ferritic-austenitic mode did not counteract the effects of small Nb additions. 相似文献
5.
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
6.
A fracture mechanics study of stress corrosion cracking (scc) of cold worked AISI 310 austenitic steel, and an experimental
metastable austenite, was conducted in hot aqueous solutions of 44.7 wt pct MgCl2 and the results compared with previous studies on AISI 316 steel. Attention was directed towards Region II behavior where
crack propagation rate (v) was independent of stress intensity (KI). The apparent activation energy of Region II was found to be in the range ~65 to 75 kJ/mol, independent of the relative
proportions of intergranular and transgranular cracking. Also, electron diffraction studies of fracture surfaces showed that
α′-martensite formation was not a pre-requisite for scc, although it may influence crack propagation rates. Cracking was discussed
in terms of a hydrogen embrittlement model under hydrogen transport control in the austenite lattice. However, adsorption
(chemisorption) effects on repassivation and dissolution behavior could not be eliminated from consideration.
Alan J. Russell, Formerly Research Student, University of British Columbia. 相似文献
7.
8.
The effect of high temperature (650 °C) low cycle fatigue on the corrosion behavior of five austenitic stainless steels (Types
304, 316L, 321, and Incoloy Alloys 800 and 800H) has been investigated. For comparison, corrosion tests were also performed
on samples of as-received material as well as material which had been solutionized and material which was sensitized at 650
°C. It was observed that cyclic loading at high temperature reduces the corrosion resistance to a much greater extent than
does just the exposure of unstressed material to elevated temperatures. Formation of chrome carbides during cycling and depletion
of chromium from the matrix is responsible for the decrease in corrosion resistance. Of the alloys tested, Type 304 exhibited
the lowest corrosion resistance. Superior corrosion resistance of the other alloys was due to the following: (a) a lower carbon
content, (b) a higher chromium content, and (c) the presence of a strong carbide forming element (stabilized material). 相似文献
9.
Ruth M. Magdowski Ph.D. Candidate Markus O. Speidel 《Metallurgical and Materials Transactions A》1988,19(6):1583-1596
This work presents the results of a comprehensive study concerning stress corrosion crack growth rates in steam turbine rotor
steels exposed to hot water. The effects of stress intensity, temperature, and dissolved gases in the water have been investigated.
Special attention has been given to the influence of impurities and alloying elements in the steel such as P, S, Mn, Si, Mo,
and Ni, and to the effect of yield strength and fracture toughness on the growth rates of stress corrosion cracks. The results
of this study clearly show that there exists a threshold stress intensity of about 20 MNm−3/2 above which the invariably intergranular stress corrosion cracks grow at a constant, stress-independent velocity. This plateau
stress corrosion crack growth rate isnot affected by the oxygen and carbon dioxide concentration in the water. The temperature and the yield strength of the steel
have a strong influence on the growth rate of stress corrosion cracks. In contrast, there isno effect of the steel composition within the range investigated, neither of the impurity elements such as P and S, nor of the
major alloying elements such as Mn, Si, Mo, and Ni. Steels with low fracture toughness due to temper embrittlement do not
exhibit faster stress corrosion crack growth rates in water than nonembrittled steels. No direct relationship between intergranular
temper embrittlement and intergranular stress corrosion crack growth in water can be demonstrated. 相似文献
10.
The internal nitridation of thin sections of austenitic Fe−Cr−Ni−Ti alloys containing up to 2 pct Ti was studied over the
temperature range 1600° to 2210°F in order to develop a method of strengthening the alloys through the introduction of a dispersoid
of stable titanium nitrides. The interparticle spacing (IPS) of the nitrides was found to increase linearly with depth from
the external surface; the effects of various parameters on the rate of change of IPS vs depth are presented. The mechanical
properties of these alloys at room and elevated temperatures were markedly improved by internally nitriding. Useful mechanical
properties were obtained up to 2200°F, with typical properties at 2000°F of 10 to 20 ksi 0.2 pct offset yield strength and
15 to 25 ksi ultimate tensile strength, but section thickness was limited to about 10 mils because of the increase in IPS
with depth and the long nitriding times needed for thicker material. In order to produce a small interparticle spacing in
a heavier section, internally nitrided 5 mil strip was consolidated by hot roll bonding and evaluated at a 60 mil thickness
by tensile and rupture testing at 2000°F. It is demonstrated that the approach taken in this work offers a feasible technique
for making a high temperature alloy having useful engineering properties. 相似文献
11.
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
12.
P. Muraleedharan H. S. Khatak J. B. Gnanamoorthy P. Rodriguez 《Metallurgical and Materials Transactions A》1985,16(2):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
13.
用U形弯试样浸泡和慢应变速率拉伸实验研究了3Cr17Ni7Mo2SiN和00Cr22Ni5Mo3N(2205)不锈钢在硫化氢介质中的应力腐蚀开裂(SCC)行为.2205不锈钢的SCC萌生孕育期较长,在pH较低的饱和H2S溶液中具有明显的SCC敏感性,其SCC敏感性随溶液pH值的升高或H2S含量的降低而迅速降低.3Cr17Ni7Mo2SiN的SCC孕育期均低于2205不锈钢,在pH ≤ 4.5、H2S的质量浓度 ≥ 103mg·L-1的H2S介质中均具有明显的SCC敏感性,其SCC敏感性受pH值和H2S含量变化影响较小.3Cr17Ni7Mo2SiN的SCC以沿晶裂纹萌生,扩展后转变为穿晶应力腐蚀开裂;2205不锈钢近表面处首先发生奥氏体-铁素体相间氢致开裂,并促进SCC萌生,其SCC为穿晶应力腐蚀开裂. 相似文献
14.
合金元素对铁素体不锈钢耐应力腐蚀开裂性能的影响 总被引:1,自引:0,他引:1
通过42%沸腾氯化镁U型弯曲试验,结合扫描电子显微镜、X射线衍射分析,研究了合金元素Ni、Cu、Mo对铁素体不锈钢耐氯化物应力腐蚀开裂性能的影响规律。结果表明,Ni、Cu元素能够提高铁素体不锈钢应力腐蚀开裂的敏感性,单独添加Mo元素不会降低铁素体不锈钢耐应力腐蚀开裂的能力,但是钢中Mo、Cu元素同时存在时,应力腐蚀开裂的敏感性大大增加。钢中析出的ε-Cu在氯离子环境中形成点蚀,引起了铁素体不锈钢应力腐蚀开裂。 相似文献
15.
John Wareing 《Metallurgical and Materials Transactions A》1977,8(5):711-721
Low cycle fatigue failures occur by the initiation and controlled growth of a surface crack. The development of crack propagation
models, based on continuum mechanics, have enabled successful predictions of fatigue life at both room and elevated temperatures.
This paper attempts to extend such models to cover the situations in which creep damage, introduced during periods of stress
relaxation, influences the rate of growth of the surface fatigue crack. Equations predicting fatigue life as a function of
hold period are in good agreement with experimental data, for Type 304 stainless steel, Type 316 stainless steel and Incoloy-800. 相似文献
16.
Raghavan Ayer C. F. Klein C. N. Marzinsky 《Metallurgical and Materials Transactions A》1992,23(9):2455-2467
The effect of aging on the precipitation of grain boundary phases in three austenitic stainless steels (AISI 347, 347AP, and
an experimental steel stabilized with hafnium) was investigated. Aging was performed both on bulk steels as well as on samples
which were subjected to a thermal treatment to simulate the coarse grain region of the heat affected zone (HAZ) during welding.
Aging of the bulk steels at 866 K for 8000 hours resulted in the precipitation of Cr23C6 carbides, σ, and Fe2Nb phases; the propensity for precipitation was least for the hafnium-stabilized steel. Weld simulation of the HAZ resulted
in dissolution of the phases present in the as-received 347 and 347AP steels, leading to grain coarsening. Subsequent aging
caused extensive grain boundary Cr23C6 carbides and inhomogeneous matrix precipitation. In addition, steel 347AP formed a precipitate free zone (PFZ) along the
grain boundaries. The steel containing hafnium showed the best microstructural stability to aging and welding.
Formerly with Exxon Research and Engineering Company. 相似文献
17.
R. Liu N. Narita C. Altstetter H. Birnbaum E. N. Pugh 《Metallurgical and Materials Transactions A》1980,11(9):1563-1574
Orientation studies have been made on several different austenitic stainless steels, using photogrammetric and electron channeling
techniques. The fracture facets produced by SCC in boiling aqueous MgCl2 (155 °C) were large and relatively flat in the case of type 310 steels, and the fracture plane was found to be at or near
{100}. The transgranular stress-corrosion fractures in type 304 steels were more complex, and there was considerably more
scatter in the orientation determinations. However, the orientations of the fracture facets in these steels were clearly not
{100}, but fell into two distributions, one near {211} and the other near {110}. Electron diffraction studies from the fracture
surfaces indicated the presence of α′ and martensites in the type 304 but not in the type 310 cases; the possibility that
this was responsible for the differences in fracture planes is discussed. Studies were also made of a type 304 specimen which
had failed by SCC at 289 °C. No martensitic phases were detected at the fracture surfaces in this case, and the fracture facets
were large and flat, similar to those for type 310. Cleavage-like fracture surfaces were also produced in type 304 steels
by hydrogen embrittlement, using both gaseous hydrogen and cathodic charging, but the facets were too small for precise orientation
determination.
Formerly with the Department of Metallurgy, University of Illinois at Urbana-Champaign.
Formerly with the Department of Metallurgy, University of Illinois at Urbana-Champaign.
Formerly Professor of Metallurgy, University of Illinois. 相似文献
18.
F. Solana C. Takamadate I. M. Bernstein W. Thompson 《Metallurgical and Materials Transactions A》1987,18(13):1023-1028
The ability of retained austenite to affect stress corrosion cracking susceptibility has been examined in two steels, containing mechanically stable and unstable retained austenite of varying amounts and distributions. While limited improvements due to this constituent were observed in both threshold (where it may act as a compcting energy trap) and in growth rates (where it can act as a mechanical barrier and hydrogen sink), these were neither consistent nor more effective than other heterogeneities. Contrary to popular belief, retained austenite does not appear to be a consistently effective microstructural constituent, at least if the aim is to improve SCC performance at strength levels up to about 1000 MPa. 相似文献
19.
F. Solana C. Takamadate I. M. Bernstein W. Thompson 《Metallurgical and Materials Transactions A》1991,22(1):1023-1028
The ability of retained austenite to affect stress corrosion cracking susceptibility has been examined in two steels, containing
mechanically stable and unstable retained austenite of varying amounts and distributions. While limited improvements due to
this constituent were observed in both threshold (where it may act as a compcting energy trap) and in growth rates (where
it can act as a mechanical barrier and hydrogen sink), these were neither consistent nor more effective than other heterogeneities.
Contrary to popular belief, retained austenite does not appear to be a consistently effective microstructural constituent,
at least if the aim is to improve SCC performance at strength levels up to about 1000 MPa. 相似文献
20.
Solana F. Takamadate C. Bernstein I. M. Thompson W. 《Metallurgical and Materials Transactions A》1987,18(6):1023-1028
Metallurgical and Materials Transactions A - The ability of retained austenite to affect stress corrosion cracking susceptibility has been examined in two steels, containing mechanically stable and... 相似文献