PH13-8Mo不锈钢在半乡村大气环境中长周期腐蚀行为

在北京半乡村大气环境中对未经预钝化及硝酸预钝化后的PH13-8Mo不锈钢进行5 a的长周期暴晒试验,通过表面形貌观察、质量损失分析、表面钝化膜及腐蚀产物膜层分析、力学性能检测及断口分析等方法,研究了硝酸预钝化处理对PH13-8Mo长周期腐蚀行为的影响规律及机理。结果表明,经5 a大气暴晒试验,硝酸预钝化处理减轻了PH13-8Mo不锈钢的点蚀、降低其均匀腐蚀速率,通过降低PH13-8Mo不锈钢钝化膜中的氢氧化物含量、提高Cr/Fe原子比并提高大气暴晒后表面的Kelvin电位,延迟了Cl?对钝化膜的破坏及点蚀的形核,进而提高了表面膜层对基体的保护作用。硝酸预钝化处理能减少在半乡村大气环境中PH13-8Mo不锈钢力学性能的下降,但对试样的断裂方式几乎没有产生影响,二者均为韧性断裂,断口均呈现典型的“杯锥状”。      

Stress corrosion cracking behavior of PH13-8Mo stainless steel in Cl-solutions

The stress corrosion cracking (SCC) behavior of PH13-8Mo precipitation hardening stainless steel (PHSS) in neutral NaCl solutions was investigated through slow-strain-rate tensile (SSRT)test at various applied potentials.Fracture morphology,elongation ratio,and percentage reduction of area were measured to evaluate the SCC susceptibility.A critical concentration of 1.0mol/L neutral NaCl existed for SCC of PH13-8Mo steel.Significant SCC emerged when the applied potential was more negative than-0.15 VSCE,and the SCC behavior was controlled by an anodic dissolution (AD) process.When the applied potential was lower than-0.55 VSCE,an obvious hydrogen-fracture morphology was observed,which indicated that the SCC behavior was controlled by hydrogen-induced cracking (HIC).Between-0.15 and-0.35 VSCE,the applied potential exceeded the equilibrium hydrogen evolution potential in neutral NaCl solutions and the crack tips were of electrochemical origin in the anodic region;thus,the SCC process was dominated by the AD mechanism.     

Delayed failure of PH13-8Mo steel plated with AI-IVD

We have experienced failure of the bolts for aircraft made of PH13-8Mo steel. The failure occurred a short time after the bolts had been fastened for assembly of aircraft parts. These bolts had been aluminum plated with ion vapor deposition (IVD) process. Based on this trouble, delayed failure of PH13-8Mo steel plated with aluminum by IVD was studied to clarify the cause of the trouble. Sustained load tests were performed in distilled water with notched specimens made of PH13-8Mo steel on which aluminum was plated by the same IVD process as defective bolts. From the tests carried out on many heats of PH13-8Mo steel, aged at 783 K (510°C), the following results were obtained: (1) heats containing more than 1.16 pct aluminum exhibited premature delayed failure with a low stress level threshold; (2) the heats containing less than 0.025 pct carbon and less than 1.16 pct aluminum showed extensive scatter in the values of threshold stress; and (3) the heats containing more than 0.025 pct carbon and less than 1.16 pct aluminum did not exhibit the premature delayed failure even at high stress levels. From the measurement of electrical resistivity changes associated with isothermal aging of PH13-8Mo steel, it is evident that the low-temperature phase formed by aging plays an important role in delayed failure and formation of the phase is significantly influenced by carbon and aluminum contents in the steel. Microcracks were found to form on the aluminum film plated by IVD when stress was applied to the specimen. Therefore, a galvanic couple would be constructed between coated aluminum and PH13-8Mo steel with the presence of distilled water which penetrated through the cracks initiated when the load was applied to the specimen. Hydrogen necessary to give rise to the delayed failure is produced by the cathodically polarized condition. Notch toughness was also controlled by carbon and aluminum contents in PH13-8Mo steel; however, it is not thought that the decrease in notch toughness plays a significant role in the cause of delayed failure. It is particularly noteworthy that carbon in the steel is useful to prevent the delayed failure and to keep excellent notch toughness in PH13-8Mo steel aged to high strength levels. Y. ASAYAMA, formarly with Engineering, Nagoya Aircraft Works, Mitsubishi Heavy Industries, Ltd.     

Effect of Environmental Factors on Electrochemical Behavior of X70 Pipeline Steel in Simulated Soil Solution

Potentiodynamic polarization measurement was used to investigate the effects of temperature, dissolved ox-ygen concentration and pH on the electrochemical behavior of X70 pipeline steel in simulated solution according to the orthogonal testing method. The results showed that temperature, dissolved oxygen concentration and pH had great influence on corrosion current density (icorr)of X70 steel. Corrosion current density of X70 steel was most influenced by dissolved oxygen concentration in simulated solution. The corrosion degree of X70 steel was the least under the environment of low temperature, deficient oxygen and weak acid.     

Effect of Environmental Factors on Electrochemical Behavior of X70 Pipeline Steel in Simulated Solution

 Potentiodynamic polarization measurement was used to investigate effects of temperature, dissolved oxygen concentration and pH on the electrochemical behavior of X70 pipeline steel in simulated solution according to the orthogonal testing method. The results showed that temperature, dissolved oxygen concentration and pH had great influence on corrosion current density (icorr) of X70 steel. Corrosion current density of X70 steel was most influenced by dissolved oxygen concentration in simulated solution. The corrosion degree of X70 steel was least under the environment of low temperature, deficit oxygen and weak acid.     

钨含量及固溶温度对022Cr25Ni7Mo3.5WCuN钢耐腐蚀性能的影响

研究了钨含量及固溶温度对超级双相不锈钢022Cr25Ni7Mo3.5WCuN耐点腐蚀性能的影响。通过化学浸泡失重法和电化学极化曲线法,测试了超级双相不锈钢022Cr25Ni7Mo3.5WCuN耐点腐蚀性能,并运用Thermo Calc热力学计算辅助分析。结果表明,固溶温度对超级双相不锈钢022Cr25Ni7Mo3.5WCuN耐点腐蚀性能影响效果显著,在1 100 ℃时,022Cr25Ni7Mo3.5WCuN 的耐腐蚀性能达到最佳;在理想的固溶条件下,钨元素有助于钝化膜的形成,钨含量的增加使得022Cr25Ni7Mo3.5WCuN的耐腐蚀性能增强,在钨质量分数为1.5%时,022Cr25Ni7Mo3.5WCuN获得最佳耐腐蚀性能,若钨含量继续增加,打破了α和γ两相的平衡,则耐蚀性能降低。     

Effect of pH on Semiconducting Property of Passive Film Formed on Ultra-High-Strength Corrosion-Resistant Steel in Sulfuric Acid Solution

Because Cr9Ni5MoCo14 is a new ultra-high-strength corrosion-resistant steel, it is important to study its corrosion behavior in sulfuric acid solution, which is used to simulate the aggressive environment. The effect of pH on the electrochemical and semiconducting properties of passive films formed on ultra-high-strength corrosion-resistant steel in sulfuric acid solution was investigated by means of the potentiodynamic polarization technique, electrochemical impedance spectroscopy (EIS), Mott-Schottky analysis, and X-ray photoelectron spectroscopy (XPS). The results indicated that Cr9Ni5MoCo14 steel showed a passive state in acid solutions. The corrosion behavior of this Cr9Ni5MoCo14 alloy was influenced by the passive film formed on the surface, including thickness, stability, and partitioning of elements of the passive film. The passive current density decreases with increasing pH, and the corrosion resistance was enhanced by the increasing thickness and depletion of the defects within the passive film. Moreover, an enrichment of chromium (primarily the oxides of Cr) and depletion of iron in the passive film led to improved corrosion resistance. These results can provide a theoretical basis for use of this alloy and further development of ultra-high-strength corrosion-resistant steel in today’s society.     

无金属粘结相硬质合金的电化学腐蚀行为

采用1 700℃、20 MPa高温高压固相烧结工艺制备WC-0.5Cr3C2-0.3VC、WC-3.65TiC-2.45TaC-0.47Cr3C2-0.28VC和WC-6Mo2C-0.47Cr3C2-0.28VC等3种无金属粘结相硬质合金。采用CHI 660C电化学工作站研究在pH=1的H2SO4溶液、pH=7的Na2SO4溶液和pH=13的NaOH溶液中3种合金的电化学腐蚀行为。结果表明,在pH=1的H2SO4溶液和pH=7的Na2SO4溶液中WC-6Mo2C-0.47Cr3C2-0.28VC合金的耐腐蚀性能最好,在pH=13的NaOH溶液中WC-3.65TiC-2.45TaC-0.47Cr3C2-0.28VC的耐腐蚀性能最好。3种无金属粘结相硬质合金在pH=13的NaOH溶液中的耐腐蚀性能均优于其在pH=1的H2SO4溶液中的耐腐蚀性能。综合比较合金的硬度、耐腐蚀性能以及原材料价格,3种合金中WC-6Mo2C-0.47Cr3C2-0.28VC合金具有更佳的性价比。     

Effect of plasma nitriding parameters on corrosion performance of 17-4 PH stainless steel

This study investigates the effect of plasma nitriding parameters on corrosion susceptibility of 17-4 PH stainless steel in 3.5?wt-% NaCl solution. In this regard, 17-4 PH stainless steel was plasma nitrided at 400°C for 5 and 10?h, 450°C for 5?h and 500°C for 5?h. Cross-sectional images after nitriding process showed that a uniform nitrided layer has been formed on steel substrate. Depending on the temperature and time of the nitriding process, different phases were formed in the nitrided layer. This affected general corrosion and pitting corrosion performance of 17-4 PH stainless steel in 3.5?wt-% NaCl solution. While precipitation of chromium nitrides for nitrided specimens at 450°C and higher increased the susceptibility to pitting and general corrosion, formation of expanded martensite (EM) in nitriding at 400°C improved the pitting corrosion resistance of 17-4 PH stainless steel. This is believed to be due to the release of nitrogen atoms from EM phase to form ammonium ions and increase the pH of the solution, supressing pit growth.     

The partitioning of alloying elements in vacuum arc remelted,Pd-modified PH 13-8 Mo alloys

The partitioning of alloying elements in as-solidified PH 13-8 Mo stainless steel containing up to 1.02 wt pct Pd has been investigated. The as-solidified structure is composed of two major phases, martensite and ferrite. Electron probe microanalysis reveals that Mo, Cr, and Al partition to the ferrite phase while Fe, Ni, Mn, and Pd partition to the martensite (prior austenite) during solidification and cooling from the solidus. In addition to bulk segregation between phases, precipitation of the intermetallic, PdAI, in the retained ferrite is observed. Precipitation of the normal hardening phase, β-NiAl, is also observed in the retained ferrite. Partition ratios of the various alloying elements are determined and are compared with those observed previously in duplex Fe-Cr-Ni stainless steel solidification structures. The martensite start temperature (M_s) was observed to decrease with increasing Pd concentration.     

445J2超纯铁素体不锈钢和316L超低碳奥氏体不锈钢在溴化锂溶液的点蚀分析

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。     

The influence of palladium on the hydrogen-assisted cracking resistance of PH 13-8 Mo stainless steel

We compare the hydrogen-assisted cracking resistance of wrought PH 13-8 Mo stainless steel alloyed with 0.4 to 1.0 wt pct palladium to the conventional alloy when aged to yield strengths of 1170 to 1250 MPa. Intergranular hydrogen cracking is suppressed with Pd in both static load and constant extension rate tests conducted with electrochemical hydrogen charging. These results are analyzed to elucidate the role of Pd in suppressing intergranular cracking. Palladium is found both in substitutional solid solution in the martensitic phase and also in the form of randomly distributed PdAl precipitates in all Pd-modified alloys. Interfacial segregation of Pd to grain boundaries and lath boundaries is not observed at any levels above a detection limit of approximately 0.5 monolayers. Hydrogen permeation analyses indicate that hydrogen ingress is not inhibited by Pd but that apparent diffusion coefficients are lowered relative to the conventional alloy. Lower diffusion coefficients are consistent with the creation of a strong but reversible hydrogen trap, identified as the uniformly distributed PdAl phase. We hypothesize that PdAl trap sites force a redistribution of trapped hydrogen, which lowers the amount of interfacially segregated hydrogen at prior austenite grain boundaries for the electrochemical conditions applied. These assertions are supported by a simplistic trapping model for PH 13-8 Mo which shows that both the hydrogen trap binding energy and the trap density for the PdAl trapping site are greater than the hydrogen trap binding energy and density for prior austenite grain boundaries. J.R. SCULLY, formerly with Sandia National Laboratories.     

高温高压环境下不同浓度KBr溶液对13Cr不锈钢的腐蚀行为影响

油气工业中溴盐完井液的使用极易导致油套管腐蚀失效的发生, 尤其是局部腐蚀风险.针对这一问题, 采用高温高压腐蚀模拟试验、扫描电镜观察与分析、电化学测试等试验研究方法, 研究了高温高压环境下不同浓度溴盐溶液对普通13Cr和超级13Cr两种典型油套管材腐蚀行为的影响.结果表明: 从平均腐蚀速率来看, 两种13Cr管材在三种浓度溴盐溶液中均表现出较好的耐蚀性能, 属于轻度或中度腐蚀, 但从局部腐蚀速率来看, 两种材料均达到严重或极严重腐蚀; 随着溴盐浓度的提高, 普通13Cr的自腐蚀电位和点蚀电位均明显负移, 对应材料的平均腐蚀速率和局部腐蚀速率均明显上升, 而超级13Cr仅点蚀电位明显负移, 自腐蚀电位则相对稳定, 对应其平均腐蚀速率变化幅度较小, 局部腐蚀速率则明显上升, 这说明相比普通13Cr, 超级13Cr对溴盐溶液具有更强的整体耐受能力, 但局部腐蚀敏感性仍然较高; 激光共聚焦(LSCM)三维表征结果表明, 在高质量浓度溴盐溶液(1.40 g·cm-3)中, 不论是普通13Cr还是超级13Cr都有明显的点蚀倾向, 这主要与溶液中高浓度的侵蚀性阴离子Br-有关, 相比于普通13Cr, 超级13Cr的点蚀敏感性相对较低, 但其点蚀风险仍不可忽视.      

时效处理对00Crl3Ni7Co5Mo4W马氏体时效不锈钢组织及耐蚀性的影响

采用动电位极化曲线、均匀腐蚀全浸试验研究了50 kg真空感应炉冶炼的00Cr13Ni7Co5Mo4W马氏体时效不锈钢（/%:0.007C,13.23Cr,7.02 Ni,5.06Co,3.72Mo,0.96W）1100℃1 h固溶,450510℃8 h时效后的耐蚀性能,通过金相显微镜、透射电镜、XRD分析了马氏体时效不锈钢的组织。结果表明,随时效温度升高时效过程析出R相增加,导致钢的耐点腐蚀性下降,同时由马氏体逆转变的奥氏体数量增加,可改善该钢的耐腐蚀性能。00Cr13Ni7Co5Mo4W马氏体时效不锈钢适宜的热处理工艺为1100℃1 h固溶+470℃8 h时效,其年腐蚀速率为1.259 0 μm/a,点蚀击穿电位为252 mV。     

钙离子的浓度对X80钢腐蚀行为的影响

采用失重法、电化学测试、扫描电镜、X射线衍射等方法研究了钙离子浓度对X80钢在哈密土壤模拟溶液中的腐蚀行为影响.在60d浸泡期内,X80钢在不同钙离子浓度模拟溶液中的腐蚀形态均为全面腐蚀,腐蚀产物都为B-FeOOH;X80钢在模拟溶液中的腐蚀速率随钙离子浓度的降低而呈逐渐增大的趋势.在180d浸泡期内,在钙离子浓度为63.5mmol·L-1的模拟溶液中,钙盐随时间的增加在X80钢基体表面不断结晶析出;钙盐层有效阻碍了溶解氧的迁移,并促进其覆盖区域下形成氧浓差电池,最终导致基体表面点蚀的萌生.同时,在内层腐蚀产物表面连续析出的钙盐层的致密性也随时间不断得到改善,在一定程度上起到了抑制氯离子和溶解氧对基体的侵蚀作用,X80钢的全面腐蚀逐渐减缓.      

Corrosion Resistance and Semiconducting Properties of Passive Films Formed on 00Cr13Ni5Mo2 Supermartensitic Stainless Steel in Cl- Environment

The semiconducting properties of passive films grown on 00Crl3Ni5Mo2 supermartensitic stainless steel were investigated in comparison with conventional 2Cr13 martensitic stainless steel. Cyclic vohammetry and electro- chemical impedance spectroscopy （EIS） were used for the studies. 00Crl3NiSMo2 steel exhibited a good corrosion resistance performance, attributing to its passive capability. The results of Mott-Schottky analysis demonstrated n- type semiconductors for the passive films with doping densities of about 1020- 1021 cm -3, and the thickness of space- charge layers was also calculated. The experimental results confirmed that Mo plays an important role in improving the corrosion resistance of 00Crl3Ni5Mo2 steel due to its impact on the doping density.     

氧化性杀菌剂对X70管线钢电化学腐蚀的影响

采用动电位极化和电化学阻抗方法，研究了X70管线钢在加入不同浓度氧化性杀菌剂(二氯异氰尿酸钠)的层流冷却水中的电化学腐蚀行为。极化曲线表明，随着层流冷却水中加入氧化性杀菌剂浓度的增大，X70管线钢的腐蚀电流密度(Icorr)呈逐渐上升的趋势。EIS结果表明，随着氧化性杀菌剂浓度的增大，电荷转移电阻逐渐减小，电化学反应的...     

硫化氢质量浓度和温度对碳钢在NACE溶液中腐蚀行为的影响

采用动电位极化曲线和电化学阻抗谱等电化学实验方法以及扫描电镜和能谱等表面分析技术对20#碳钢在不同H₂S质量浓度(0,95.61,103.22,224.16 mg·L-1)、不同温度(25,35,45℃)下的NACE溶液(含CO₂)中腐蚀行为进行了研究,同时对该环境下腐蚀产物的形成机制进行了探讨.发现在含有CO₂的NACE溶液中,加入少量H₂S,能加剧碳钢腐蚀,加速阳极铁的溶解和阴极氢气的析出.随着H₂S质量浓度的增加,腐蚀电流密度增大,碳钢腐蚀加剧.温度升高,腐蚀极化电阻变小,腐蚀也会加剧.腐蚀试样外层絮状腐蚀产物主要是铁碳化物,接近基体表面的腐蚀产物主要是铁硫化物.      

固溶温度对00Cr13Ni7Co5Mo4W马氏体时效不锈钢组织和耐点腐蚀的影响

通过显微组织分析、动电位极化曲线和均匀腐蚀全浸试验研究了00Cr13Ni7Co5Mo4W马氏体时效不锈钢固溶温度1050~1150℃对该钢组织和人工海水中的耐蚀性的影响。结果表明,固溶温度影响马氏体时效不锈钢的组织均匀性和晶粒尺寸,进而影响该钢的抗点腐蚀能力;00Cr13Ni7Co5Mo4W马氏体时效不锈钢适宜的固溶温度为1100℃,经1100℃ 1 h固溶处理后,其年腐蚀速率仅为1.09μm/a,击穿电位为300 mV。     

库尔勒土壤环境中X70管线钢剥离涂层下的腐蚀特征

利用矩形剥离缝隙模型研究了库尔勒土壤模拟溶液中X70管线钢剥离涂层下的滞留液化学特征以及X70钢腐蚀特征.随着浸泡时间的延长,缝内滞留液的p H值逐渐下降直至稳定.Cl-在缝内滞留液中有不同程度的聚集,其中在缝隙底部的质量浓度最高.SO₄2-的质量浓度在腐蚀初期表现为随距离增加而降低,到腐蚀后期表现为随距离增加而升高.HCO₃-和NO₃-的质量浓度从漏点至缝底有小幅降低.阳离子的质量浓度变化不明显.缝内X70钢的腐蚀形貌表现为明显的点蚀,且随距漏点距离的增加,点蚀越严重.