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1.
The tensile and corrosion behaviors of 0.13 pct N-containing CD4MCU cast duplex stainless steels with different Cr contents
ranging from 23 to 28 pct were examined in the present study. The polarization tests were conducted in 3.5 pct NaCl + 5 pct
H 2SO 4 aqueous solution for general corrosion resistance, and the in-situ slow strain rate (SSR) tests were also conducted in air and 3.5 pct NaCl + 5 pct H 2SO 4 aqueous solution to quantify the resistance to stress corrosion cracking (SCC) of the three materials. A substantial microstructural
change in 0.13 pct N-containing CD4MCU cast duplex stainless steel was observed with different Cr contents, which in turn
affected the tensile and corrosion behaviors significantly. Tensile behavior of 0.13 pct N-containing CD4MCU cast duplex stainless
steel, for example, varied in a nonlinear manner with different Cr contents due to the volume change of hard ferritic phase
and the presence of the second precipitates of soft austenitic phase in the ferrite matrix. The beneficial effect of Cr for
improving the general corrosion and the SCC resistances was largely overshadowed by this variation in microstructural characteristics.
The relationship between the microstructural evolution and the tensile and corrosion behavior of 0.13 pct N-containing CD4MCU
cast duplex stainless steels with different Cr contents was discussed based on the optical microscopy and scanning electron
microscopy (SEM) micrographic and fractographic observations. 相似文献
2.
The effect of N addition on the microstructure, tensile, and corrosion behaviors of CD4MCU (Fe-25Cr-5Ni-2.8Cu-2Mo) cast duplex
stainless steel was examined in the present study. The slow strain rate tests were also conducted at a nominal strain rate
of 1 × 10 −6/s in air and 3.5 pct NaCl+5 pct H 2SO 4 solution for studying the stress corrosion cracking (SCC) behavior. It was observed that the volume fraction of austenitic
phase in CD4MCU alloy varied from 38 to 59 pct with increasing nitrogen content from 0 to 0.27 wt. pct. The tensile behavior
of CD4MCU cast duplex stainless steels, which tended to vary significantly with different N contents, appeared to be strongly
related to the volume changes in ferritic and austenitic phases, rather than the intrinsic N effect. The improvement in the
resistance to general corrosion in 3.5 pct NaCl+5 pct H 2SO 4 aqueous solution was notable with 0.13 pct N addition. The further improvement was not significant with further N addition.
The resistance to SCC of CD4MCU cast duplex stainless steels in 3.5 pct NaCl+5 pct H 2SO 4 aqueous solution, however, increased continuously with increasing N content. The enhancement in the SCC resistance was believed
to be related to the volume fraction of globular austenitic colonies, which tended to act as barriers for the development
of initial pitting cracks in the ferritic phase into the sharp ones. 相似文献
3.
The effect of nitrogen additions upon the pitting resistance of 18 pct Cr, 18 pct Mn stainless steel has been investigated
by potentiokinetic techniques in a 1000 ppm NaCl solution. Nitrogen additions increased the pitting resistance of the steel
irrespective of structure, however, the ferritic steel was less pit resistant than the (duplex) steels containing both austenite
and ferrite which, in turn, were less pit resistant than the totally austenitic steels. For steels having a duplex structure,
the effect of nitrogen on the pitting resistance was observed to follow a linear function of the relative amount of austenite
in these steels due to the area effects of the austenite and ferrite which are galvanically coupled in these steels. The addition
of nitrogen was found to increase the amount of austenite at a rate of approximately 200 times the percent nitrogen addition
from 36 pct austenite for the 0.02 pct N steel to 100 pct for the 0.40 pct nitrogen steel. The addition of nitrogen to the
totally austenitic steels increased the pitting resistance at the rate of approximately 0.31 volts per pct nitrogen added,
but no mechanism was found for the increased resistance.
This paper is based on a presentation made at a symposium on “New Developments in Ferritic and Duplex Stainless Steels,” held
at the Fall Meeting in Cleveland, Ohio, on October 19, 1972, under the sponsorship of the Corrosion Resistant Metals Committee
of TMS-IMD and the Corrosion and Oxidation Activity of the ASM. 相似文献
4.
研究了合金元素对双相不锈钢2101耐点蚀性能的影响规律。结果显示,2101系列合金的浸泡点蚀腐蚀速率在1.9~7.0 g/(m^2.h)之间,与304不锈钢在同一数量级;Mo是提高2101系双相不锈钢耐腐蚀性的关键元素,而N对耐腐蚀性的影响不大;点蚀起源和Thermo-Calc计算结果显示2101成分体系中,铁素体相是耐点蚀性较弱相,提高铁素体相耐蚀性是提高合金整体耐蚀性的关键;当Cr含量固定在21.5%时,Mo作为铁素体形成元素将在铁素体相中富集,提高铁素体相的耐点蚀性能,从而提高合金整体耐蚀性。 相似文献
5.
The feasibility of processing duplex stainless steels with promising properties using a powder metallurgical route, including the consolidation by field-assisted hot pressing, is assessed in this investigation. The influence of the particle size and morphology of the raw austenitic and ferritic powders on the final microstructure and properties is also evaluated for an austenitic content of 60 wt pct. In addition, the properties of a new microconstituent generated between the initial constituents are analyzed. The maximum sintered density (98.9 pct) and the best mechanical behavior, in terms of elastic modulus, nanohardness, yield strength, ultimate tensile strength, and ductility, are reached by the duplex stainless steel processed with austenitic and ferritic gas atomized stainless steel powders. 相似文献
6.
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 (K 1) 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 (AT ISCC) 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
7.
奥氏体-铁素体双相不锈钢中稳定存在奥氏体相和铁素体相,该钢具有较高的机械性能和优异的耐点蚀、晶间腐蚀和应力腐蚀性能,在核电站设备制备中被广泛应用。一般双相不锈钢铸件中铁素体相的体积分数≤20%,服役温度≤425℃,双相不锈钢锻件中铁素体相约占50%,服役温度≤250℃。文中介绍了核电站设备中应用的双相不锈钢铸、锻件的化学成分、制造和焊接工艺要求及组织和性能。 相似文献
8.
为了研究酸性NaCl溶液中双相不锈钢的耐腐蚀性能,以含微量稀土Ce的UNS S31803双相不锈钢为研究对象,采用电化学阳极极化和交流阻抗相结合的方法测试其在NaCl+HCl混合溶液中的耐腐蚀性能。利用扫描电镜(SEM)观测腐蚀后的形貌特征,采用电子探针(EPMA)检测合金元素与杂质元素的分布特征,分析Ce元素的加入对双相不锈钢电化学腐蚀行为的影响机制。结果表明,钢中存在两相的选择性腐蚀并伴有局部点蚀,其中铁素体相是腐蚀较严重的相;阳极极化测试与交流阻抗测试结果相吻合,Ce拓宽了试验钢的钝化区间;Ce通过净化钢液、降低S和P元素在相界的偏聚及使Cr、Ni和Mo等合金元素在两相中的分布更均匀等作用,提高了钢的耐腐蚀性能。 相似文献
9.
The purpose of the current study is to develop austenitic nickel-free stainless steels with lower chromium content and higher manganese and nitrogen contents. In order to prevent nickel-induced skin allergy, cobalt, manganese, and nitrogen were used to substitute nickel in the designed steel. Our results demonstrated that manganese content greater than 14 wt pct results in a structure that is in full austenite phase. The manganese content appears to increase the solubility of nitrogen; however, a lower corrosion potential was found in steel with high manganese content. Molybdenum appears to be able to increase the pitting potential. The effects of Cr, Mn, Mo, and N on corrosion behavior of Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were evaluated with potentiodynamic tests and XPS surface analysis. The results reveal that anodic current and pits formation of the Fe-16Cr-2Co-Mn-Mo-N high nitrogen stainless steels were smaller than those of lower manganese and nitrogen content stainless steel. 相似文献
10.
不锈钢的近代发展目标是超级不锈钢-超级奥氏体,超级铁素体,超级复相不锈钢。这些钢可在大范围内解决局部腐蚀问题并在某些用途中可替代钛和镍基合金。 相似文献
11.
445J2铁素体不锈钢由于高的导热率、低的热膨胀系数以及良好的耐蚀性能使得其作为溴冷机中一些部件的良好候选材料,本文采用电化学测试方法对比研究了445J2超纯铁素体不锈钢(/%:0.01C,22.5Cr, 1.9Mo, 0.27Nb, 0.20Ti, 0.09Al, 0.36Cu, 0.015P,0.001S,0.015N)和316L奥氏体不锈钢(/%:0.002C,16.8Cr, 10.19Ni, 2.02Mo, 0.025P,0.0008S)在20~60℃0.1~1M的溴化锂溶液中的点蚀行为,并采用扫描电镜(SEM)和能谱分析仪(EDS)对电化学结果进行表征。结果表明,随着LiBr温度和浓度的升高,两种钢腐蚀电流密度增大,点蚀电位降低,耐点蚀性变差;氧化物和硫化物夹杂会引起两种钢的点蚀;高含量的Cr以及Mo、Ti、Nb、Al等合金元素使445J2钢具有优异的耐点蚀性能。 相似文献
12.
The mechanical and fracture properties of austenitic stainless steels (SSs) alloyed with gallium require assessment in order
to determine the likelihood of premature storage-container failure following Ga uptake. AISI 304 L SS was cast with 1, 3,
6, 9, and 12 wt pct Ga. Increased Ga concentration promoted duplex microstructure formation with the ferritic phase having
a nearly identical composition to the austenitic phase. Room-temperature tests indicated that small additions of Ga (less
than 3 wt pct) were beneficial to the mechanical behavior of 304 L SS but that 12 wt pct Ga resulted in a 95 pct loss in ductility.
Small additions of Ga are beneficial to the cracking resistance of stainless steel. Elastic-plastic fracture mechanics analysis
indicated that 3 wt pct Ga alloys showed the greatest resistance to crack initiation and propagation as measured by fatigue
crack growth rate, fracture toughness, and tearing modulus. The 12 wt pct Ga alloys were least resistant to crack initiation
and propagation and these alloys primarily failed by transgranular cleavage. It is hypothesized that Ga metal embrittlement
is partially responsible for increased embrittlement. 相似文献
13.
不锈钢可通过压制与烧结水雾化粉末来制取.粉冶品级的不锈钢有铁素体、奥氏体、马氏体、两相(铁素体+奥氏体)、双相(铁素体+马氏体)以及沉淀硬化(马氏体)等不锈钢.开发双相粉冶不锈钢反映了对较高强度、较高延性与韧性的需求在增长.在本研究中,开发出一种新的低成本粉冶不锈钢,它将双相(铁素体+马氏体)显微结构与沉淀硬化的优点结合在一起.它与其他沉淀硬化合金不同,尽管这种不锈钢在时效后强度与韧性有所提高,但延性与冲击韧度的提高更大.借助组成与显微结构评估了新合金的力学性能. 相似文献
14.
The effect of nitrogen content on the stress corrosion cracking (SCC) behavior of 22 pct Cr duplex stainless steel (DSS) in
chloride solutions was investigated in this study. Slow strain rate testing (SSRT) was employed to evaluate the SCC susceptibility.
The experimental results showed that the tensile strength and ductility of 22 pct Cr DSS increased with increasing amount
of nitrogen (in the range of 0.103 to 0.195 wt pct). Slow strain rate testing results indicated that 22 pct Cr DSSs were resistant
to SCC in 3.5 wt pct NaCl solution at 80 °C. However, environmentally assisted cracking occurred in 40 wt pct CaCl 2 solution at 100 °C and in boiling 45 wt pct MgCl 2 solution at 155 °C, respectively. The effects of environment and nitrogen content in DSS on the cracking susceptibility are
discussed in this article. Selective dissolution of ferrite phase was found to participate in the SCC process for tests in
CaCl 2 solution. At temperatures above 80 °C, dynamic strain aging was found to occur in various environments at a strain beyond
plastic deformation. 相似文献
15.
The microstructural modifications in three austenitic stainless steels (types 308, 310, and 312) were evaluated after rapid
solidification. These three steels are commonly used weld filler metals. Two methods of rapid solidification were investigated,
autogenous laser welding and arc-hammer splat quenching. The structure of 310 stainless steel was found to be 100 pct austenite,
and did not vary over the range of conditions studied. On the contrary, the structures of types 308 and 312 steels were very
sensitive to the cooling rates and solidification conditions. With the highest cooling rates, the type 308 structure was fully
austenitic while the type 312 structure was fully ferritic. At lower cooling rates, the structures were duplex ferrite plus
austenite. The results were interpreted in terms of faster kinetics of solidification of austenite compared to ferrite under
the conditions examined. A comparison of the structures produced by the two rapid solidification techniques indicated the
cooling rates are comparable. 相似文献
16.
The kinetics of hydrogen-induced slow crack growth (SCG) under constant load was studied in two stainless steel alloys containing
mixtures of bcc and fcc phases. FERRALIUM 255, a duplex stainless steel, consisting of ∼50 pct austenite in a ferrite matrix,
was tested in hydrogen gas at 0 to 100 °C with the loading axis both perpendicular and parallel to the rolling direction.
In addition, specimens of AISI 301 were deformed in air in different ways to produce various amounts of bcc phase in an austenite
matrix prior to testing in H 2 gas at room temperature. The kinetics of subcritical slow crack growth (SCG) in these alloys was compared with that for austenitic
and for ferritic stainless steels. The SCG rates were rationalized in terms of differences in hydrogen permeation in the two
phases. The results confirm that a higher rate of supply and accumulation of hydrogen in the region ahead of the crack tip
allows a higher cracking velocity. 相似文献
17.
An alloy development program has been undertaken with the aim of identifying an Fe-Cr-Mn stainless steel with ferritic-martensitic
microduplex phase balance of sufficient stability to produce moderate strength and ductility, good impact resistance and acceptable
as-welded properties. A microduplex, low C and N, Ti stabilized composition of Fe-11.5 pct Cr-3 pct Mn has been found to provide
a yield strength of ⋍550 MPa, a tensile strength of ≃650 MPa, tensile elongation of 20 pct, a CVN impact transition temperature
of-115°C (at 0.33 cm gage) and good weldability as determined by bend, impact, and intergranular corrosion testing. The alloy
possesses general corrosion resistance roughly comparable to T405 and T430 ferritic stainless steels. The impact resistance
achieved with the mixture of ferrite and martensite is inconsistent with previous concepts of second phase toughening in microduplex
alloys, with the mixture apparently being significantly tougher than either of its components in bulk form.
J.R. WOOD formerly with Allegheny Ludlum Steel Corporation, Brackenridge, PA 相似文献
18.
采用浸泡失重法和电化学方法研究Ce和W对铁素体不锈钢在含Cl-溶液中耐点蚀性能的影响,并通过恒电位极化法测定不同Ce和W含量的铁素体不锈钢临界点蚀温度(CPT)。结果表明,W和Ce都可显著抑制铁素体不锈钢在FeCl 3溶液中的腐蚀溶解,且含W的不锈钢蚀坑坑底有W元素富集。Ce和W的添加提高了不锈钢在5%NaCl溶液中的临界点蚀温度,并且当W的质量分数达到1%时,可以显著增强蚀坑的再钝化能力。添加Ce和W可提高不锈钢的点蚀电位,降低腐蚀电流密度,提高不锈钢的耐点蚀性能。不同成分的铁素体不锈钢在中性氯溶液中都表现出稳定的钝态,而Ce和W的添加可以提高钝化膜的稳定性,扩大钝化区范围。 相似文献
19.
The effect of Nb microalloying on microstructure, mechanical properties, and pitting corrosion properties of quenched and tempered 13?pct Cr-5?pct Ni-0.02?pct C martensitic stainless steels with different Mo and N contents was investigated. The microstructure, density, and dispersion of high-angle boundaries, nanoscale precipitates, and amount of retained austenite were characterized by using electron backscattered diffraction, transmission electron microscopy, and X-ray diffraction to correlate with properties. The results show that the combined effects of lowering nitrogen content in 13?pct Cr-5?pct Ni-1~2?pct Mo-0.02?pct C steels to 0.01?wt pct, and adding 0.1?pct Nb are to decrease the amount of Cr-rich precipitates, as Nb preferentially combines with residual carbon and nitrogen to form carbonitrides, suppressing the formation of Cr 2N and Cr 23C 6. Austenite grain refinement can be achieved by Nb microalloying through proper heat treatment. If the nitrogen content is kept high, then Cr-rich precipitates would occur irrespective of microalloying addition. The NbN would also occur at high temperature, which will act as substrate for nucleation of coarse precipitates during subsequent tempering, impairing the toughness of the steel. It was shown that the addition of Nb to low interstitial super martensitic stainless steel retards the formation of reversed austenite and results in the formation of nanoscale precipitates (5 to 15?nm), which contribute to a significant increase in strength. More importantly, the pitting corrosion resistance was found to increase with Nb addition. This is attributed to suppression of Cr-rich precipitates, which can cause local depletion of Cr in the matrix and the initiation of pitting corrosion. 相似文献
20.
Three two-phase Fe-Mn-Al alloys with nominal compositions, Fe-24Mn-9Al, Fe-27Mn-9Al-3Cr,. and Fe-27Mn-9Al-6Cr, were prepared
in the solution-treated and cold-rolled conditions. The fractions of ferrite in the solution-treated condition were controlled
at 46 to 60 pct, mainly by adjusting the carbon content and the relative amounts of Mn and Al. The ferrite fractions were
reduced to 30 to 37 pct after 75 pct deformation by cold-rolling. Specimens were tensile tested at open circuit in aerated
3.5 pct NaCl solution at slow strain rates ranging from 4 × 10 -7 to 4 × 10 -5 s -1 at room temperature. All of the alloys were quite susceptible to environmentally assisted cracking (EAC). The deformed specimens
showed less susceptibility, presumably because the plasticity was already too limited. The EAC appeared to occur at or after
the onset of plastic deformation. In this alloy system, the ferritic phase was less resistant to EAC than the austenitic phase,
in contrast to the Fe-Cr-Ni stainless steels. The crack propagated preferentially through the ferrite grains or along the
ferrite/austenite grain boundaries. The addition of up to 6 pct Cr did not improve the EAC resistance.
Formerly Graduate Student, Department of Materials Science and Engineering, National Tsing Hua University 相似文献
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