喷砂处理对A7N01铝合金应力腐蚀开裂和点蚀性能的影响

采用慢应变速率试验和循环极化试验,研究了喷砂对A7N01铝合金耐应力腐蚀开裂和点蚀性能的影响。结果表明:在3.5%NaCl(质量分数)溶液中,与未喷砂合金相比,喷砂处理后A7N01铝合金的应力腐蚀敏感指数增大,抗应力腐蚀性能下降。喷砂后合金的点蚀电位、保护电位均降低,滞后环增大,且随浸泡时间增长,点蚀电位和保护电位负移,滞后环增大,喷砂处理使合金的抗点蚀能力和钝化膜修复能力降低。喷砂处理会造成A7N01铝合金表层晶粒细化、硬度增加,但同时喷砂也会造成表面粗糙度增加,并有微裂纹等表面损伤发生,从而降低合金的耐蚀性。     

The chloride stress-corrosion cracking behavior of stainless steels under different test methods

Chloride-induced stress-corrosion cracking (SCC) is one of the failure modes of stainless steels. Highly alloyed austenitic stainless steels S32654, S31254, and N08028, and duplex grades S32750 and S31803 possess much improved resistance to SCC compared with S30400 and S31600 steels. With the development of a database, SSData, experimental data collected from calcium chloride tests, autoclave tests, and drop evaporation tests were evaluated. Stress-corrosion cracking data generated by autoclave tests agreed well with the practical service conditions and can be used to discriminate alloys for SCC resistance in sodium chloride solution. Drop evaporation test data can be used in situations where evaporation may occur and cyclic loading may be involved. The SCC resistance of alloys under each method increased with increasing molybdenum equivalent Mo + 0.25Cr + 0.1Ni. For a given alloy, the testing result depends on the stress state and environment; different test methods can give different ranking orders concerning SCC resistance. The performance of duplex stainless steels in a chloride-containing environment at higher temperatures was not as good as expected when dynamic loading was involved.     

铸造TC4钛合金细节疲劳强度DFRcutoff的研究

细节疲劳额定值法(DFR法)是基于概率疲劳的民机结构疲劳可靠性寿命分析方法之一.针对我国铸造TC4钛合金疲劳性能数据不全而不能满足新型民用涡扇支线飞机研发需要的现状,采用双点法和单点法对热等静压处理的铸造TC4钛合金的细节疲劳强度截至值DFRcutoff进行了对比研究.结果表明:双点法所测DFRcutoff=375.83 MPa,单点法所测DFRcutoff=387.30 MPa,两者之间的相对误差小于3.1%,试验结果准确可靠,可为新型涡扇支线飞机选材、疲劳设计和寿命评估以及民用飞机适航审查提供数据支持.     

The stress corrosion cracking behaviour of heat‐treated Al–Zn–Mg–Cu alloy in modified salt spray fog testing

The stress corrosion cracking behaviour of 7075 (Al–Zn–Mg–Cu) alloy have been studied in a salt spray fog chamber with two vapourised aqueous solutions (0 and 5% NaCl). The paper analyses the stress corrosion resistance of 7075 aluminium alloy with several precipitation‐ageing heat treatments. The results are compared with that obtained in 3.5% NaCl aqueous solution at 20 °C. The salt spray fog testing has permitted a good evaluation of SCC susceptibility in 7075 alloy. All temper conditions studied were susceptible to SCC in the different environments tested. 7075‐T6 temper was the most susceptible, while in all the cases studied 7075‐T73 temper was the least susceptible. Compared to 7075‐T6, 7075‐RRA temper improved the resistance against the SCC process, but the mechanical properties obtained were lower.     

IncoMAPAl—9052合金在3.5%NaCl溶液中的应力腐蚀行为

采用双悬臂梁试样,实验研究了IncoMAP Al-9052合金在3.5％NaCl溶液中的应力腐蚀开裂(SCC)行为。结果表明该种合金的裂纹扩展机制有别于常规的铝合金。其初期阶段的裂纹扩展过程可划分为三个阶段,在每一阶段的裂纹扩展机制可能是不同的,但其裂纹扩展的主要机制为氢脆。     

BEHAVIOUR AND MECHANISM OF STRESS CORROSION CRACKING FOR Al-Li-Cu-Mg ALLOY

Studies were made of the influence of aging conditions and applied potentials on thestress corrosion carcking(SCC)susceptibility for an Al-Li-Cu-Mg alloy by slow strainrate technique.The relationship between the relative hydrogen content on specimensurface,the applied potentials and elapsed time has also been examined.The SCCsusceptibility was found to be dependent on aging conditions in which the peak agedcondition gave the worst SCC resistance and the natural aged condition had the best one.The SCC susceptibility and surface hydrogen content relates to the applied potentials.The anodic potentials increase SCC susceptibility,while the cathodic ones below thecritical potential accelerate SCC.It is considered that both the anodic dissolution and     

压水堆核电站蒸汽发生器用600合金管在含铅高温碱溶液中的应力腐蚀行为研究

    采用U型弯曲试样研究了高、低温工厂退火状态的压水堆蒸汽发生器（SG）商用化600合金管在330℃、含10g/L PbO的10%NaOH高温水溶液中的应力腐蚀开裂（SCC）行为.结果表明,在氢浓度很高时,600合金表现为较严重的晶间腐蚀（IGA）,最大侵蚀深度约270μm;没有观察到明显的应力腐蚀开裂,腐蚀晶界中有铅的沉积;冷拉预变形、退火温度对材料的腐蚀和应力腐蚀行为的影响不明显.     

Environmentally assisted cracking behaviour of plasma electrolytic oxidation coated AZ31 magnesium alloy

Abstract

A wrought AZ31 magnesium alloy was plasma electrolytic oxidation (PEO) coated in phosphate and silicate based alkaline electrolytes. The effect of these PEO coatings on the stress corrosion cracking (SCC) behaviour of the alloy was investigated by slow strain rate tensile (SSRT) tests in ASTM D1384 solution. The untreated and PEO coated AZ31 magnesium alloy specimens were found to be susceptible to SCC, despite the fact that the PEO coatings offered an excellent general corrosion resistance. The results of the polarisation tests on the untreated AZ31 alloy specimen after prolonged immersion in ASTM D1384 electrolyte suggested the formation of a film on the surface constituted by the corrosion products. The cracking of this film and the evolution/ingress of hydrogen at these defective sites during the SSRT tests in the corrosive environment was believed to be responsible for the SCC of the untreated alloy. Similarly, the cracking of the PEO coatings during the SSRT test, the consequent exposure of the underneath magnesium alloy substrate and the associated electrochemical reactions were attributed as reasons for the SCC of the PEO coated specimens. The transgranular mode of fracture in all the cases avowed that the hydrogen induced cracking was the mechanism of SCC.     

Effects of laser shock processing on stress corrosion cracking susceptibility of AZ31B magnesium alloy

Laser shock processing (LSP) is a new technique for strengthening metals. The effects of LSP on the stress corrosion cracking (SCC) susceptibility of AZ31B magnesium (Mg) alloy were investigated. Water-immersed specimens of AZ31B magnesium alloy were shocked by Q-switched Nd: glass laser with a wavelength of 1064 nm. A fine-grained structure with an average sub-grain size of 5.8 μm was obtained after four laser impacts. Residual stress distribution as a function of depth was assessed by using X-ray diffraction technology. It was observed that with increasing the number of laser impacts, the compressive residual stress near the surface increased. The depth of the compressive residual stress induced by LSP exceeded 0.8 mm from the surface. SCC test in 1 wt.% NaOH solution showed that LSP retarded the SCC initiation and growth in AZ31B Mg alloy.     

时效工艺对2519A铝合金力学性能及抗应力腐蚀开裂性能的影响

通过常温拉伸实验、慢应变拉伸应力腐蚀实验、极化曲线测试及透射电镜等研究了不同时效工艺对2519A合金的力学性能和抗应力腐蚀开裂性能的影响。结果表明:与传统的2519A-T87合金相比,再时效时间为19 h的2519A-T9I7合金同时具有优异的力学性能和良好的抗应力腐蚀开裂性能。这是由于2519A-T9I7合金在T9I6态的基础上延长了再时效时间,使晶界析出相聚集球化,相间距增加,破坏了腐蚀通路,提高了抗应力腐蚀开裂性能。     

Development of a simulated bird-strike test method

An inexpensive test method has been developed to predict the dynamic impact response (bird-strike resistance) of aircraft turbine engine fan blade materials. The test utilizes an instrumented pendulum to transfer energy to a machined fan blade cross section. To validate the test, the relative performance of one wrought and four cast Ti-6Al-4V materials subjected to the simulated bird-strike test was compared to that of the same materials tested at Wright-Patterson Air Force Base by conventional bird-strike testing. The relative ranking of crack initiation loads determined from the simulated test corresponded to fan blade failure velocities determined by the Air Force test, thereby validating the simulated method as a screening tool for fan blade material development.     

Slow strain rate testing of high-strength aluminium alloy plate in an aqueous solution of 3% NaCl + 0.3% H2O2

The stress corrosion cracking (SCC) behaviour of aluminium alloy plate materials was investigated in the short transverse direction using the slow strain rate (SSR) testing technique. The synthetic environment used was an aqueous solution of 3% NaCl + 0.3% H₂O₂. Reference tests under constant deformation and alternate immersion conditions according to ASTM G44 were performed, too. Both static and dynamic loading tests indicate high SCC susceptibility with the alloys 2024-T351, 2091-T8X51, 7050 T651 and 7475-T651. For the alloy 8090-T8171, a low SCC resistance is found in the alternate immersion tests, whereas a rather moderate sensitivity is observed performing SSR tests. The SSR testing technique fails to indicate the SCC sensitivity of the more resistant alloys 2024-T851 and 7050-T7651. As demonstrated by pre-exposure tests, the reduction of fracture energy observed with the latter alloys as well as with the immune alloys 7050-T7351 and 7475-T7351 is caused by pitting and intergranular corrosion. Using an aqueous solution of 3% NaCl + 0.3% H₂O₂, the SSR testing technique is a useful rapid method to screen wrought aluminium alloys which are quite sensitive to environmentally assisted cracking. Because chloride-peroxide solutions are also conducive to corrosion processes independent of stress, pre exposure tests are required to be incorporated into such sorting tests.     

Effects of polarisation on mechanical properties and stress corrosion cracking susceptibility of 7050 aluminium alloy

The effects of polarisation (including cathodic and anodic polarisation) on mechanical properties and stress corrosion cracking (SCC) susceptibility (I_SCC) of 7050 aluminium alloy have been investigated by means of polarisation and slow strain rate test. The results of cathodic polarisation experiments showed that the I_SCC increased with shifting negatively the polarisation potential when the cathodic potential E_C≧?1100 mV(SCE), while it decreased with shifting negatively the polarisation potential when the cathodic potential E_CI_SCC increased severely with increasing the polarisation potential. In addition, the extents for the effect of polarisation potential on I_SCC were different among the 7050 aluminium alloy under various aging states. Polarisation was of the biggest effect on the I_SCC of under aged state, the smallest effect of over aged state and the middle effect of peak aged state. The SCC mechanism of aluminium alloy was a combination of anodic dissolution and hydrogen embrittlement, and the effects of hydrogen on SCC increased with increasing the hydrogen concentration.     

X70钢焊接接头在近中性溶液中应力腐蚀行为研究

采用慢应变速率试验(SSRT)、扫描电镜以及电化学测量技术研究了X70管线钢焊接接头在近中性模拟土壤溶液中的应力腐蚀开裂(SCC)行为。结果表明,断口和柱面SCC裂纹均发生在热影响区(HAZ)。在试验溶液中,随着外加极化电位降低管线钢SCC敏感性增强,电位负移到一定电位值后,SCC敏感性减弱;随着溶液pH值降低,腐蚀速率增大,敏感电位区间负移。施加阴极电位时,在试样断口观察到明显的准解理脆断特征,断口和柱面有穿晶SCC裂纹。分析了焊接接头试样HAZ的SCC机理,在试验介质中,管线钢应力腐蚀开裂主要受阳极溶解和氢致开裂两种机理的联合作用,适当的电位可以使阳极溶解和氢致开裂的联合作用达到最大,从而造成较严重的应力腐蚀开裂。     

A comprehensive assessment of the performance of corrosion resistant alloys in hot acidic brines for application in oil and gas production

Four stainless steels and alloys (17-4 PH, X4CrNiMo 16-5-1, F6NM and UNS N09935) were evaluated in relation to their application in the oil and gas industry. These materials were tested in solutions exhibiting a range of chloride concentrations, pH values and temperatures of interest for the oil and gas producing environments. The pitting sensitivity was investigated by means of potentiodynamic polarisation measurements, based on the ASTM G61 standard, in conjunction with a morphological study performed by scanning electron and optical microscopy. The resistance to stress corrosion cracking (SCC) was evaluated in compliance with the ASTM G123 standard. Erosion–corrosion was assessed by exposing the materials under electrochemical control to a flux of erodent glass microspheres in a rotating disc electrode device. A ranking of the materials resistance was derived, based on appropriate parameters, devised to effectively and synthetically represent the complex sets of environments of interest for the relevant application. Our results showed, as expected, that UNS N09935 displays the best performance with respect to pitting resistance and susceptibility to SCC as well as a very good resistance to erosion–corrosion. Among the other investigated materials, 17-4 PH showed higher resistance to pitting, X4CrNiMo 16-5-1 and F6NM longer time to SCC failure while 17-4 PH and X4CrNiMo 16-5-1 exhibited superior ability to withstand erosion–corrosion damaging.     

A New Understanding of Stress Corrosion Cracking Mechanism of X80 Pipeline Steel at Passive Potential in High-pH Solutions

Susceptibilities to stress corrosion cracking(SCC) of X80 pipeline steel in relatively concentrated carbonate/bicarbonate solutions with different chloride ion concentrations or p H value at a passive potential of-200 m V vs SCE were investigated by slow strain rate tensile test.In order to explore the SCC mechanism and the evaluation criterion for the SCC susceptibility of the steel in passive state,electrochemical measurements were taken.Potentiodynamic polarization curves were obtained at different potential sweep rates,and electrochemical impedance spectroscopy measurements were taken after fast polarization to the passive potential.The effects of chloride ion and p H on SCC behaviors of X80 steel at the passive potential were also discussed.The results showed that the SCC mechanism of X80 pipeline steel was greatly influenced by the passive film formed in these solutions.The SCC behaviors followed the film suppressed anodic dissolution mechanism in these circumstances,because the filming process accounted for a considerable proportion of the overall electrode process.The criteria for evaluating the SCC susceptibility of the steel at passive potential were proposed and validated.Decreasing in the concentration of chloride ion or increasing in p H value resulted in the reduction in SCC susceptibility.The existence of chloride ion greatly lowered the passivation tendency and the film stability,while its concentration determined the dissolution rate of the steel matrix.Higher p H value was responsible for the stable and tenacious passive films and the high repassivation capability.It was also inclined to lower the anodic dissolution rate at crack tips by retarding the cathodic oxygen reduction.     

5083铝合金慢应变速率拉伸下的应力腐蚀行为

采用慢应变速率拉伸(SSRT)测试法及扫描电镜(SEM)与透射电镜(TEM)分析手段,研究了预变形量及应变速率对5083铝合金在空气和3.5%NaCl溶液中应力腐蚀开裂(SCC)行为的影响。结果表明:在空气中,5083铝合金几乎不发生SCC现象,其断口均呈现韧性断裂形貌;在3.5%NaCl溶液中,5083铝合金具有SCC敏感性,其断口呈现局部沿晶界或相界断裂形貌,随着应变速率的减小,应力腐蚀敏感指数(ISSRT)增大,当应变速率减至1×10-6s-1时,其应力腐蚀断口呈现典型的解理脆断特征;(Mg5Al8)等第二相析出及预变形后位错增多是导致5083铝合金SCC敏感性增大的主要原因。     

淬火速度对7085铝合金显微组织和应力腐蚀的影响(英文)

采用力学性能测试、慢应变速率拉伸实验,结合扫描电镜和透射电镜及电化学测试等方法,研究淬火速度对7085铝合金组织和应力腐蚀性能的影响。结果表明,随着淬火速度的降低,合金晶界析出相的尺寸和间距增大,晶界析出相的Cu含量降低;合金的抗应力腐蚀性能随着淬火速度的减少先增强后减弱。晶界析出相的尺寸和分布以及Cu含量是影响合金抗应力腐蚀性能的主要因素。     

Application limits of stainless steels in the petroleum industry

Stainless steels have a great variety of potential applications in the petroleum industry, mainly as an alternative to carbon steel in corrosive environments. Within a number of media that can cause corrosion problems with these materials, only chloride solutions and hydrogen sulfide are of importance in oilfield service. A reliable tool that permits the proper selection of stainless steels has yet been missing. In order to provide engineering diagrams for this purpose, pitting and stress corrosion cracking (SCC) tests were performed. Specimens were exposed to NaCl solutions containing from 3 to 100,000 ppm Cl^? at temperatures from 40 to 200 °C. This test configuration was chosen to give a better representation of actual service conditions than accelerated standard test procedures do. Tested materials were the austenitic stainless steel grades 321, 316Ti (API LC30‐1812) and 254 SMO, and 22Cr duplex (austenitic‐ferritic) steel (API LC65‐2205). Based on an optical examination of the specimens, no‐risk regions of chloride concentration vs. temperature have been identified. Subsequently, service temperature limits have been deduced for each tested material. Thus, material failures by pitting and SCC can be prevented without overdesigning. The results of the testing series are applicable to all chloride environments without presence of H₂S, as they have to be handled by primary production equipment, as well as transportation and gas processing facilities.     

Al—Li—Cu—Mg合金应力腐蚀性能及机理研究

利用恒应变速率方法研究了Al—Li—Cu—Mg合金的应力腐蚀开裂,包括时效条件及外加电位对应力腐蚀的影响,同时研究了试样表面相对氢浓度与外加电位及应力腐蚀时间的关系,实验结果表明,合金的应力腐蚀性能取决于时效条件,其中峰时效条件下最差,自然时效条件下最好,应力腐蚀敏感性及试样表面氢浓度与外加电位有关,阳极电位增加应力腐蚀敏感性,阴极电位低于临界电位时加速应力腐蚀,认为合金在应力腐蚀过程中阳极溶解与氢脆机制联合作用。