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1.
Robert O. Ritchie 《Metallurgical and Materials Transactions A》1977,8(7):1131-1140
Interactions between hydrogen embrittlement and temper embrittlement have been examined in a study of fracture and low growth
rate (near-threshold) fatigue crack propagation in 300-M high strength steel, tested in humid air. The steel was investigated
in an unembrittled condition (oil quenched after tempering at 650°C) and temper embrittled condition (step-cooled after tempering
at 650°C). Step-cooling resulted in a severe loss of toughness (approximately 50 pct reduction), without loss in strength,
concurrent with a change in fracture mode from micr ovoid coalescence to inter granular. Using Auger spectroscopy analysis,
the embrittlement was attributed to the cosegregation of alloying elements (Ni and Mn) and impurity elements (P and Si) to
prior austenite grain boundaries. Prior temper embrittlement gave rise to a substantial reduction in resistance to fatigue
crack propagation, particularly at lower stress intensities approaching the threshold for crack growth(x0394;K
o). At intermediate growth rates (10-5 to 10-3 mmJcycle), propagation rates in both unembrittled and embrittled material were largely similar, and only weakly dependent
on the load ratio, consistent with the striation mechanism of growth observed. At near-threshold growth rates (<10−5 to 10−6 mmJcycle), embrittled material exhibited significantly higher growth rates, 30 pct reduction in threshold ΔKo values and intergranular facets on fatigue fracture surfaces. Near-threshold propagation rates (and ΔKo values) were also found to be strongly dependent on the load ratio. The results are discussed in terms of the combined influence
of segregated impurity atoms (temper embrittlement) and hydrogen atoms, evolved from crack tip surface reactions with water
vapor in the moist air environment (hydrogen embrittlement). The significance of crack closure concepts on this model is briefly
described. ntmis]formerly with the Lawrence Berkeley Laboratory, University of California in Berkeley.
Formerly with the Lawrence Berkeley Laboratery, University of California in Berkeley. 相似文献
2.
J. Sojka V. Vodárek P. Váňová I. Schindler L. Kander A. Wenglorzová F. Filuš 《国际钢铁研究》2011,82(7):766-771
We have evaluated the resistance of two samples of TRIP 800 steel prepared under laboratory conditions at the Faculty of Metallurgy and Materials Engineering (FMME) V?B (Technical University of Ostrava, Czech Republic) in a sour environment containing H2S. The first steel investigated had a C–Mn–Si composition, and the second steel had a C–Mn–Si–Al composition. Both TRIP steels were characterized using the yield strength in the range 420 to 450 MPa and tensile strength in the range 880 to 900 MPa. The TRIP steel samples were in the form of sheets with a thickness of 1.5 mm. The residual austenite content was 11% and 13%, respectively, in the two steels studied. The resistance to hydrogen embrittlement was evaluated in a sour environment that contained hydrogen sulphide using hydrogen‐induced cracking (HIC) and sulphide stress cracking (SSC) tests performed in accordance with NACE standards. Both TRIP 800 steels showed a high resistance to hydrogen embrittlement, and no SSC cracks were observed. Some cracking arising from HIC was observed in both steels. The measured parameters showed some variation; in some cases they were lower than recommended limits, but in other cases the measured parameters were higher (e.g., the crack length ratio was up to 70%). The cracks initiated preferentially at non‐metallic inclusions, either at elongated manganese sulphide particles, or at oxide stringers that were rich in Al. 相似文献
3.
The effects of additions of 0.6 to 2.0% Cr on the temper embrittlement behaviour of 0.25 C–1.0 Si–1.3 Mn cast steel under several hardening conditions were studied. The susceptibility to temper embrittlement, transgranular and intergranular fracture were increased as the chromium content increased when the steels were tempered at 350°C and slowly cooled from 550°C. The impact toughness and abrasion resistance of the steels were found to depend to a great extent on the Cr-content and tempering temperature. 相似文献
4.
The effect of impurities on the threshold stress intensity for cracking in H2S (K{ISCC}) has been investigated at various yield strength levels for a low alloy steel. Results show that the effect of
impurities on KISCC is a function of the yield strength level. At low yield strength levels the KISCC of the steel is lowered markedly due to additions of impurities. However, at higher yield strength levels the KISCC data for pure and impure steels converge to a single value. In addition, the effect of yield strength level on Xiscc is a
function of the degree of temper embrittlement caused by impurity segregation. For small degrees of temper embrittlement,
increasing the yield strength decreases the -Kiscc appreciably, while for large degrees of temper embrittlement,K
ISCC is relatively insensitive to the yield strength. At KISCCvalues below about 50 MPa Vm, the percentage of intergranular fracture in H2S is found to be uniquely related to KISCC regardless of the yield strength-impurity combination by which a givenK
ISCC is obtained. Results of the study indicate that the KISCC OF steels is affected by impurities, yield strength and H2S both directly and indirectly via interactive mechanisms. 相似文献
5.
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
6.
Richard L. S. Thomas John R. Scully Richard P. Gangloff 《Metallurgical and Materials Transactions A》2003,34(2):327-344
Near-peak-aged AERMET 100 is susceptible to severe internal hydrogen embrittlement (IHE) at 23 °C, if a sufficient diffusible
hydrogen content is present, compromising the high toughness of this ultrahigh-strength steel (UHSS). Evidence includes the
threshold stress intensity for subcritical IHE (K
TH
) as low as 10 pct of the plane-strain fracture toughness (K
IC
) and a fracture-mode transition from microvoid coalescence to brittle transgranular (TG) cracking, apparently along martensite
lath interfaces and cleavage planes. The K
TH
value decreases from a K
IC
value of 132 to 143 MPa√m to 12 MPa√m, and the amount of brittle TG fracture increases to nearly 100 pct as the concentration
of diffusible H increases from essentially 0 to 8 wppm, with severe embrittlement in the 0 to 2 wppm H regime. The IHE is
time dependent, as evidenced by increasing K
TH
values with increasing dK/dt and K-independent subcritical crack growth rates, and is attributed to diffusional H repartition from reversible trap sites to
the stressed crack tip. The partition distance is ∼1 μm, consistent with the fine-scale microstructure of AERMET 100. The causes of the susceptibility of AERMET 100 to TG IHE are
very high crack-tip stresses and a reservoir of mobile H trapped reversibly at (Fe,Cr,Mo)2C precipitates. These factors enable repartition of H to misoriented martensite lath interfaces and interstitial sites near
cleavage planes, with each prone to decohesion along a connected path. Predissolved H also reduces the ductile fracture toughness
of AERMET 100 at high loading rates, perhaps due to reduced void growth caused by H trapped strongly at undissolved metal
carbides. 相似文献
7.
The crack growth rates and threshold stress intensities,K
TH, for a 3 1/2 NiCrMoV steel (0.2 pct proof stress 1200 MPa) have been measured in a hydrogen environment at various temperatures
and hydrogen pressures. Fractographic evidence and the observation of alternating fast and slow crack growth nearK
TH suggests that the crack advances by the repeated nucleation of microcracks at microstructural features ahead of the main
crack. Transient crack growth is observed following load increases just belowK
TH. Using the idea, from unstable cleavage fracture theory, that for fracture a critical stress must be exceeded over a critical
distance ahead of the crack, and assuming that this critical stress is reduced in proportion to the local hydrogen concentration
(in equilibrium with the external hydrogen atK
TH), a theoretical dependence ofK
TH on hydrogen pressure is derived which compares well with the experimental evidence. 相似文献
8.
《Acta Metallurgica Materialia》1994,42(1):127-132
The effect of cerium on temper embrittlement of P-doped Mn structural steels has been investigated by measurements of the ductile-brittle transition temperature and observations by AES, SIMS and SEM of the fracture surfaces of isothermally embrittled steels. It is shown that P can bring about the temper embrittlement of Mn structural steels; cerium may reduce the temper embrittlement of the steels and the segregation of cerium to grain boundaries may play an important part in reducing the temper embrittlement of the steels. 相似文献
9.
The effects of additions of 0.7 pct Mn and/or 0.6 pct Si on the temper embrittlement behavior of 2.25 Cr-1 Mo steel at several
hardness levels were determined. As in Part I, the tendency for the P segregation was dependent upon the Mo concentration
in the ferrite, which is controlled by the types of carbides formed during heat treatment or aging. Additions of either Mn
or Si increase the fraction of grain boundaries which adsorb P (although they do not increase the P concentration on the embrittled
boundaries significantly) thereby raising the amount of temper embrittlement as measured by the transition temperature shift.
Mn and Si appear to act independently and their effects appear to be additive; this is rationalized in terms of their expected
influences on the segregation free energy for P in Fe. 相似文献
10.
Tong-Yi Zhang Wu-Yang Chu Ying Li Chi-Mei Hsiao 《Metallurgical and Materials Transactions A》1986,17(4):717-725
Hydrogen induced cracking (HIC) and stress corrosion cracking (SCC) of a high-strength steel 34CrNi3Mo (T.S = 1700 MPa) under Mode II loading were investigated using notched specimens. The stress field around the notch tip
was analyzed by means of finite element method. The result shows HIC and SCC under Mode II loading initiated at the back of
the notch tip,i.e., θ = -110 deg, where hydrostatic stress has maximum value. However, cracking is oriented along the shear stress direction
at the site, not normal to the direction of maximum principal stress component. On the contrary, if the specimens are loaded
to fracture in air under Mode II loading, cracking at the maximum shear stress site around the notch tip and the cracking
direction coincide with the direction of the maximum shear stress. The above facts indicate that hydrogen induced delayed
plastic deformation is a necessary condition for HIC, and the nature of SCC for high-strength steel in 3.5 pct NaCl solution
is HIC. The results show that HIC and SCC under Mode II loading can occur during dynamic charging with hydrogen and in 3.5
pct NaCl solution, respectively. The normalized threshold stress intensity factors under Mode II loading during dynamic charging
in 1 N H2SO4 + 0.25 g As2O3/L solution and in 3.5 pct NaCl solution are KIIH/KIIX = 0.1 and KIISCC/KIIX = 0.45, respectively. The corresponding values under Mode I loading are KIH/KIX = 0.02 and KISCC/KIX = 0.37, where KIIX and K,IX are critical values loaded to failure in air under Mode II and Mode I loading, respectively. Thus, (KIIH/KIIX)/ KIH/KIX) = 5 and (KIISCC/KIIX)/K,(ISCC/KIX) = 1.2. A typical intergranular fracture was observed during HIC and SCC under Modes II and I loading. But the fracture surfaces
of specimens failed in air are composed of dimples for both kinds of loading.
Formerly Student at Beijing University of Iron and Steel Technology 相似文献
11.
12.
13.
G. M. Spink 《Metallurgical and Materials Transactions A》1977,8(1):135-143
The susceptibility to temper embrittlement of eight different rotor steels has been studied in terms of the effects of composition,
of cooling rate from tempering temperature, of isothermal aging, of steel-making practice and of strength level and tempering
temperature. The Ni Cr Mo V steels tested showed increasing susceptibility to temper embrittlement with increasing nickel
content. The normally marked susceptibility of a high phosphorus 3 pct Cr Mo steel was eliminated by the removal of manganese.
Embrittlement in a 3 pct Ni Cr Mo V steel was caused by the equilibrium segregation of solute atoms to the prior austenite
grain boundaries. Two Cr Mo V steels tested were not susceptible to temper embrittlement. Electroslag remelting and refining
had very little effect on the susceptibility of the steels tested. Strength level and tempering temperature had no effect
on the degree of embrittlement of the 3 pct Ni Cr Mo V disc steel. The possibilities of remedial action include an adjustment
of the post tempering cooling rate, to optimize the conflicting interests of minimum temper embrittlement and adequate stress
relief, and the production of very low manganese rotor steels. 相似文献
14.
Stress corrosion cracking (SCC) of high-strength steel in aqueous environment and hydrogen induced cracking (HIC) during dynamic
charging under Mode III loading were investigated. The threshold stress intensities for SCC and HIC under Modes III and I
were measured and compared. It was found that both SCC and HIC under Mode III loading initiated and propagated on the planes
inclined at 45 deg to the notch plane, differing from that under Mode I loading. The fracture surfaces, however, revealed
intergranular facets, similar to that under Mode I loading. The addition of thiourea decreased the threshold value for SCC
under Mode III and Mode I loading, which was still higher than that for dynamic charging. The threshold values of both SCC
and HIC under Mode III were larger than that under Mode I,i.e., KIIIH> KIH, KIIISCC > KISCC. Based upon the fracture mechanics analysis, this difference is attributed to the different equilibrium hydrogen concentration
between Modes III and I loading. These results give strong evidence that the SCC mechanism in high strength steel under Mode
III loading is also related to hydrogen induced cracking.
Formerly Student at Beijing University of Iron and Steel 相似文献
15.
The effect of transformation product on the temper embrittlement susceptibility of a Cr-Mo-V steel doped with P and Sn has
been investigated at different strength levels. Results show that at low strength levels (< 10R
C
) embrittlement susceptibilities of tempered bainite and ferrite-pearlite structures are comparable to each other, but lower
relative to tempered martensite. The lower susceptibility of tempered bainite relative to tempered martensite obtains up to
about 40R
C
, above which the susceptibilities for the two structures are similar. Variation of embrittlement susceptibility with microstructure
is completely consistent with the degree of grain boundary segregation of P and Sn. The segregation is smaller in bainite
than in martensite at a given strength level and increases with increasing strength level for a given structure. When compared
at the same degree of embrittlement (i.e., same shift in FATT), the amount of grain boundary segregate and the extent of intergranular fracture are lower in tempered
bainite compared to martensite indicating that embrittlement of interfaces other than prior austenite boundaries might be
an important factor in the embrittlement of bainite structures. 相似文献
16.
B. London D. V. Nelson J. C. Shyne 《Metallurgical and Materials Transactions A》1988,19(10):2497-2502
Fatigue crack growth in compact tension samples of high purity 4140 steel quenched and tempered to various strength levels
was investigated. Tempering temperatures of 200, 400, 550, and 700 °C produced yield strengths from 1600 to 875 MPa, respectively.
Crack propagation and crack closure were monitored inK-decreasing tests performed underR = 0.05 loading conditions in laboratory air. Results indicated that as the yield strength increased the crack growth rate
increased at a given ΔK and ΔKth decreased. Threshold values varied from 2.8 MPa m1/2 (200 °C temper) to 9.5 MPa m1/2 (700 °C temper). Cracks in the 200 °C tempered samples grew by an intergranular mechanism following prior austenite grain
boundaries probably caused by hydrogen embrittlement or tempered martensite embrittlement. Tempering above 200 °C produced
transgranular fatigue crack growth. The level of crack closure increased with tempering temperature and with crack propagation
in a given tempered condition. Crack closure was caused by a combination of plasticity-induced and oxide-induced mechanisms.
The use of an effective stress intensity range based on crack closure consolidated the fatigue crack growth curves and the
threshold values for all tempering temperatures except 200 °C.
Formerly Graduate Research Assistant, Department of Materials Science and Engineering, Stanford University, Stanford, CA.
Formerly Professor, Department of Materials Science and Engineering, Stanford University, Stanford, CA. 相似文献
17.
随着汽车行业的快速发展,轻量化汽车用钢的研发和应用越来越广泛。抗拉强度超过1000 MPa的第二、三代汽车用钢往往是复相组织,通过固溶、析出、变形、细晶强化等各种强化方式,在基体中形成大量缺陷,导致钢材服役过程中对氢更加敏感,容易在很小的氢溶解条件下发生氢脆。Fe?Mn?C系、Fe?Mn?Al?C系等含Mn量高的汽车结构用钢因层错能较高,不仅直接决定了其强韧性机制,还对其服役性能有重要影响。在Fe?Mn?C系TWIP钢的成分基础上,添加少量Al元素,形成Fe?Mn?(Al)?C钢,不仅能降低钢材密度,提高钢材的强韧性,也因Al元素改变了钢材的微观组织构成,一定程度上令氢脆得到缓解。但当Al含量较高时,形成低密度钢,其组织构成更加复杂,析出物更多,导致氢脆敏感性更显著。本文从Fe?Mn?(Al)?C高强韧性钢的组织构成、第二相、晶体缺陷等特征出发,综述了H在Fe?Mn?(Al)?C钢中的渗透、溶解和扩散行为,H与基体组织、析出相、晶格缺陷的交互作用,H在钢中的作用模型、氢脆机制、氢脆评价手段和方法等。并评述了Fe?Mn?(Al)?C高强韧性钢氢脆问题开展的相关研究工作和最新发展动态,指出通过第一性原理计算、分子动力学模拟和借助氢原子微印技术、三维原子探针等物理实验相结合的方法是从微观层面揭示高强韧性钢氢脆机制的未来发展方向。 相似文献
18.
R. L. Bodnar T. Ohhashi R. I. Jaffee 《Metallurgical and Materials Transactions A》1989,20(8):1445-1460
Three high-temperature bainitic alloy steels were evaluated in the laboratory to determine the effects of Mn, Si, and impurities
(i.e., S, P, Sn, As, and Sb) on microstructure and mechanical properties. The alloy steels were 3.5NiCrMoV and CrMoV, which are
used for turbine rotors, and 2.25Cr-1Mo, which is used in pressure vessel applications. The important effects of Mn, Si, and
impurities, which should control the design of these high-temperature bainitic steels, are presented. Key results are used
to illustrate the influence of these variables on cleanliness, overheating, austenitizing, hardenability, tempering, ductility,
toughness, temper embrittlement, creep rupture, and low-cycle fatigue. Low levels of Mn, Si, and impurities not only result
in improved temper embrittlement resistance in these steels but also lead to an improvement in creep rupture properties (i.e., improved strength and ductility). These results have produced some general guidelines for the design of high-temperature
bainitic steels. Examples illustrating the implementation of the results and the effectiveness of the design guidelines are
provided. Largely based on the benefits shown by this work, a high-purity 3.5NiCrMoV steel, which is essentially free of Mn,
Si, and impurities, has been developed and is already being used commercially.
T. OHHASHI was formerly Research Scientist, Japan Steel Works, Ltd., Muroran Research Laboratory, 4 Chatsumachi, Muroran,
051 Japan. 相似文献
19.
A critical evaluation of the stress-corrosion cracking mechanism in high-strength aluminum alloys 总被引:3,自引:0,他引:3
Seong-Min Lee Su-Il Pyun Young-Gab Chun 《Metallurgical and Materials Transactions A》1991,22(10):2407-2414
Attempts have been made to elucidate the mechanism of stress-corrosion cracking (SCC) in high-strength Al-Zn-Mg and Al-Li-Zr
alloys exposed to aqueous environments by considering the temperature dependence of SCC susceptibility based upon the anodic
dissolution and hydrogen embrittlement models. A quantitative correlation which involves the change of threshold stress intensity,K
ISCC, with temperature on the basis of anodic dissolution has been developed with the aid of linear elastic fracture mechanics.
From the derived correlation, it is concluded that the threshold stress intensity decreases as the test temperature increases.
This suggestion is inconsistent with that predicted on the basis of hydrogen embrittlement. It is experimentally observed
from the Al-Zn-Mg and Al-Li-Zr alloys that the threshold stress intensity,K,ISCC, decreases and the crack propagation rate,da/dt, over the stress intensity increases with increasing test temperature. From considering the change in SCC susceptibility
with temperature, it is suggested that a gradual transition in the mechanism for the stress-corrosion crack propagation occurs
from anodic dissolution in stage I, where the crack propagation rate increases sharply with stress intensity, to hydrogen
embrittlement in stage II, where the crack propagation rate is independent of stress intensity. 相似文献
20.
H. E. Townsend 《Metallurgical and Materials Transactions A》1975,6(3):877-883
The effects of electroplated and hot-dip zinc coatings on the fracture of low-alloy steel AISI 4140 bars tempered to hardnesses
in the range Rc 33 to 49 were studied. Either electroplated or hot-dip zinc coatings decrease resistance to stress corrosion
cracking,i.e., they reduceK
sc, the threshold stress intensity for stress corrosion cracking in 3.5 wt pct NaCl solution. AboveK
scelectroplated-zinc coatings do not appear to affect the crack-growth rate, although the incubation period prior to the onset
of crack growth is reduced. Hot-dip zinc coatings increase stress corrosion crack growth rates slightly because of the additive
effect of internal dissolved hydrogen. Hot-dip zinc coatings reduce the critical stress intensity for fracture in the absence
of a corrosive environment because of embrittlement by internal hydrogen which is released from traps during hot-dip coating
and confined by the inter metallic coatings which form on the steel surface in the hot dip bath. A simple fracture mechanics
analysis indicates that either increasing diameter or the presence of a zinc coating lowers the critical hardness at which
the stress corrosion cracking of structural bolts can occur. 相似文献