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.     

氢对不锈钢钝化膜纳米力学性能的影响

利用电化学实验方法和纳米力学探针技术,通过测量载荷-位移关系曲线,研究了氢对不锈钢钝化膜纳米力学性能的影响。结果表明:随氢含量的增加,不锈钢钝化膜的临界破裂载荷降低,位移偏移量减小,氢导致钝化膜的径向抗拉强度(应力)和弹性模量降低,钝化膜随氢含量的增加而逐渐软化。

     

Influence of Heat Treatment Temperature on Micro-structure and Property of 00Cr13Ni5Mo2 Su-permartensitic Stainless Steel

The microstructural evolution and mechanical property of 00Cr13Ni5Mo2supermartensitic stainless steel(SMSS)subjected to different heat treatments were investigated.Room tensile tests,hardness tests,scanning electron microscopy,transmission electron microscopy and X-ray diffraction were conducted on the heat-treated steels.It is found that the microstructure of the heat-treated steel is composed of tempered lath martensite,retained austenite andδ-ferrite.The austenitizing temperature and tempering temperature have a significant effect on the microstructural changes,which leads to the complex variations of mechanical properties.The fine tempered lath martensite and more dispersed reversed austenite in the microstructure facilitate improving the comprehensive mechanical properties of the studied steel.The optimal heat treatment process of 00Cr13Ni5Mo2SMSS is obtained by austenitizing at 1 000℃for 0.5h+air cooling followed by tempering at 630℃for 2h+air cooling,where the excellent combination of tensile strength,elongation and hardness can be achieved.     

不锈钢去膜表面在氯化镁溶液中的钝化过程

采用划破电极技术,研究了不锈钢去膜表面在氯化镁溶液中的钝化过程。不锈钢在氯化镁溶液(14%,80℃)中钝化时的真实电流衰减规律为:
i(t)=C₁exp(-a₁t)+C₂exp(-a₂t)
式中第一项反映吸附膜生长速度,第二项反映氧化膜生长速度。不锈钢去膜表面在氯化镁溶液中钝化时膜成长的规律符合高电场离子传导的膜生长机理。     

Influence of Tempering Process on Mechanical Properties of 00Cr13Ni4Mo Supermartensitic Stainless Steel

To investigate the influence of tempering process on microstructural evolutions and mechanical properties of 00Cr13Ni4Mo supermartensitic stainless steel(SMSS),specimens were tempered in the temperature range of 520-720 ℃ for 3 h followed by air cooling and an optimized tempering temperature was chosen to prolong holding time from 3 to 12 h.After heat treatments,microstructure examination was conducted by scanning electron microscope,X-ray diffraction examinations,hardness measurements and tensile tests.The results revealed that the superior mechanical properties were achieved by quenching at 1040 ℃ for 1 h+water cooling and tempering at 600 ℃ for 3 h+air cooling.Increasing isothermal tempering time could improve the toughness notably.It was believed that the property was correlated with the microstructure of tempered lath martensite and retained austenite.More retained austenite content is beneficial to the higher toughness of the SMSS.     

不锈钢裸表面在氯化物溶液中的点腐蚀

研究了不锈钢去膜表面在氯化镁介质中的点腐蚀现象。去膜表面发生点蚀的临界电位低于膜覆盖表面发生点蚀的临界电位。去膜表面的点蚀主要在晶界和夹杂起源。点蚀形貌是敏锐的条纹状花样。根据作者提出的裸表面与氯化物介质反应步骤模型讨论了点蚀特征电位的意义以及裸表面点蚀形成的过程。     

Effects of Welding Procedure on Corrosion Resistance and Hydrogen Embrittlement of Supermartensitic Stainless Steel Deposits

The effects of shielding gas and post weld heat treatment on the pitting resistance, stress corrosion cracking and hydrogen embrittlement of supermartensitic stainless steel deposits were studied. Two all-weld-metal test coupons were prepared using a metal-cored wire under Ar+5% He and Ar+18%CO₂ gas shielding mixtures. Solubilizing and solubilizing plus double tempering heat treatments were done with the objective of achieving different microstructural results. The samples welded under Ar+5% He showed higher pitting corrosion resistance, for all post weld heat treatments, than those welded under Ar+18%CO₂. The different post weld heat treatments generated higher susceptibility to this corrosion mechanism. None of the samples presented signs of stress corrosion cracking, but in those subjected to the heat treatment, grain boundary selective attack was observed, on the surfaces of all the samples studied. The samples with highest hardness were more susceptible to hydrogen damage, thereby leading to reduced tensile strength on this condition.     

Electronic Properties of Passive Films Formed on G3 and G30 Nickel-based Alloys in Bicarbonate/Carbonate Buffer Solution

The electronic properties of passive films formed on G3 and G30 alloys in bicarbonate/carbonate buffer solution were comparatively studied by electrochemical impedance spectra(EIS) and Mott-Schottky analysis, the chemical composition of the passive film formed on G3 alloy was detected by X-ray photoelectron spectroscopy (XPS). The results show that passive film on G3 alloy had better protection than that on G30 alloy. The transfer resistance, film resistance and diffusion resistance of the passive films on both alloys increased with increasing formation potential, prolonging formation time, increasing pH value, decreasing formation temperature, and decreasing chloride and sulphide ions concentration. Mott-Schottky plot reveals that the passive films on the two alloys show a p-n semi-conductive character. XPS analysis indicates that the passive film on G3 alloy was composed of an inner Cr oxide and an outer Fe, Mo/Ni oxides.     

铜对奥氏体抗菌不锈钢性能的影响

 研究了不同铜含量的奥氏体抗菌不锈钢的抗菌性能、腐蚀性能和力学性能。样品经过热轧、抗菌热处理、冷轧、退火处理后,进行了抗菌试验、腐蚀试验等。试验结果表明,随着铜含量的增加,抗菌性逐渐提高;其耐点蚀性随着铜含量的增加呈提高的趋势;强度随着铜含量的增加先减后增,塑性先增后减。     

G3镍基合金钝化膜的耐蚀性研究

利用极化曲线和电容测量法(Mott-Schottky曲线),研究了G3镍基合金油管材料在室温空气中以及130℃和205℃同时含H2S和Cl-的腐蚀介质中浸泡720 h所形成的3种钝化膜的电化学行为和半导体性质.结果表明:在室温空气中和130℃腐蚀介质中形成的钝化膜都具有良好的耐蚀性,而在205℃腐蚀介质中形成的钝化膜耐蚀性下降;前者具有双极性n-p型半导体特征,而后者为n型半导体,且由于掺杂浓度增加,耐蚀性能下降.     

氮对304奥氏体不锈钢组织和力学性能的影响

在０Ｃｒ１８Ｎｉ９奥氏体不锈钢成分基础上，加入一定的氮，并使钢中的镍含量控制在标准下限含量的条件下，研究了氮对组织和力学性能的影响。结果表明：加氮后钢的强度提高，奥氏体稳定不变，固溶态组织不变，而敏化后晶界析出物类型有所不同。     

Effect of Solution Annealing Temperature on Pitting Behavior of Duplex Stainless Steel 2204 in Chloride Solutions

The effect of solution annealing temperature ranging from 950 to 1 200℃ on the microstructure and corrosion performance of duplex stainless steel(DSS)2204 were investigated.The proportion of the ferrite phase increased while the austenite phase decreased and the ferrite stabilizing elements diluted in the ferrite phase with the increase of annealing temperature.The critical pitting temperature(CPT)of specimens annealed at 1 000℃ was higher than those annealed at 950 ℃,whereas further increasing the annealing temperature to 1 200 ℃ decreased the CPT.The pitting initiation sites were observed in the austenite phase,at the boundary of ferrite/austenite phase and inside the ferrite phase for specimens annealed at 950,1 000℃ and exceeding 1 100℃,respectively.The evolution trend of the CPT and the pit initiation site were analyzed by the pitting resistance equivalent number.     

Characterization of Passive Film Formed on AISI 316L Stainless Steel after Magnetoelectropolishing in a Broad Range of Polarization Parameters

The aim of the paper is to present the changes in the surface film composition on AISI 316L stainless steel (SS) after electropolishing (EP) and magnetoelectropolishing (MEP) in a broad range of the process conditions. The X‐ray photoelectron spectroscopy surface analyses were performed to reveal the effect of MEP. The EP process has been performed under natural convection (in a stagnant electrolyte), much above the polarization plateau. A series of experiments were carried out on AISI 316L SS samples in accordance with the five‐level composite rotary statistical plan with the variables being the magnetic field intensity B (mT), and the anodic current density i (A dm^?2). XP high resolution spectra have been obtained on AISI 316L SS surface concerning Fe 2p, Cr 2p, O 1s, S 2p, P 2p, and C 1s, respectively. The Cr:Fe ratio regarding both metallic M and compound X was also studied and calculated. At the end, the summary results of Cr/Fe = f(B, i) in relation to the corrosion potential, have been compared. The conclusions, concerning the selection of MEP process conditions, regarding the optimum Cr/Fe ratio and corrosion behavior, have been formulated. It was found the Cr:Fe ratio well correlates with the pitting corrosion potential. MEP process can modify not only the rate of dissolution to a determined extent, but also control the corrosion behavior and Cr:Fe ratio results.     

Thermal Scratch on Surface of SUS430 Stainless Steel Strip in Cold Rolling Process

The thermal scratch significantly influences the surface quality of the stainless steel in cold strip rolling.The thermal scratch has a close relation to the rolling parameters,the rolls surface and the emulsions used in rolling.In order to explain the thermal scratch on the strip surface,the cold rolling process of SUS430stainless steel strip was investigated in the laboratory.The thermal scratch defect occurs frequently in the second rolling pass(maximum reduction in height is 32.3%),especially on the lower surface of strips.When concentration and temperature of the emulsion are the same,the thermal scratch on the surface of the strip is aggravated with increasing the roll surface roughness.With the same roll surface roughness and emulsion concentration,the thermal scratch is obviously more severe at an emulsion temperature of 63℃than 55℃.With the same roll surface roughness and emulsion temperature,the thermal scratch is distinctly weaker at the emulsion concentration of 6%than that of 3%.     

Effect of Additive Cu-10Sn on Sintering Behavior and Wear Resistance of 316L Stainless Steel

 Austenitic 316L stainless steel has good corrosion resistance; however, the relative softness often limits its application. Severe adhesive wear often occurs between the 316L stainless steel and the metal counterpart. Cu-10Sn alloy is often used to improve the wear resistance of powder metallurgy 316L stainless steel. The influence of Cu-10Sn on sintering behavior and wear resistance of powder metallurgy 316L stainless steel was investigated. The parameters investigated included sintering temperature and volume percent of Cu-10Sn. A maximum relative density of 97% was achieved with 25% (in volume percent) Cu-10Sn content at a sintering temperature of 1300 ℃ for 60 min. The irregular and sharp angles of 316L stainless steel particles become round, and the pores are removed completely as a result of large amount of liquid phase formed during sintering. The minimum friction mass loss was achieved with 25% Cu-10Sn content.     

高氮不锈轴承钢中的碳氮化物对力学性能的影响

 440C等高碳马氏体轴承钢中由于存在大量粗大的共晶碳化物,降低其耐蚀性和疲劳性能,影响了其广泛应用。40Cr15Mo2VN作为一种新型高氮不锈轴承钢,通过降低碳含量,增加氮含量和微合金化来改善其性能。氮的加入一方面析出细小弥散的氮化物,强化了基体;另一方面改善了钢中析出的碳化物的形态、尺寸和分布,使其由原来的带状和网状连续分布变为近圆形颗粒,最大碳化物尺寸由原来的70μm以上减小到小于18μm,弥散分布,从而使Rm达到2000MPa以上,ReL达到1700MPa以上,有些超过1800MPa,表面硬度≥585(HRC),U型缺口冲击功保持在8J以上,并具有优异的耐蚀性和疲劳性能,满足轴承钢的服役要求。     

Effects of Sulphate-reducing Bacteria on Corrosion Behaviour of 2205 Duplex Stainless Steel

The effects of sulphate-reducing bacteria(SRB)on the 2205 duplex stainless steel in the sea water and oil industry environments were studied by electrochemical impedance spectroscopy(EIS),potentiodynamic polarization and microorganism analysis.The results showed that the detected SRB was the non-spore bacillus of about 0.8μm×(1.8-2.2)μm in size and the content of S was about 7.59% in the corrosion products.SRB contributed to the corrosion evolution which caused the corrosion failure of 2205 duplex stainless steel pipe in the liquid hydrocarbon cooler.During the corrosion process,the produced H2S could significantly influence the anodic process and finally accelerate the corrosion.SEM observation indicated that the distribution of SRB on the surface of 2205 duplex stainless steel was nonuniform.X-ray photoelectron spectroscopy analysis revealed that the surface film was composed of Cr2O3,MoO3,FeS,FeS2,Fe(OH)2 and FeO after immersing the sample in the SRB medium for 14d.     

Effect of Cold Deformation on Phase Evolution and Mechanical Properties in an Austenitic Stainless Steel for Structural and Safety Applications

 Abstract： The effects of cold deformation on the formation of strain induced α′ martensite and mechanical properties of an austenitic stainless steel have been examined. X-ray diffraction analysis has revealed that 30% and 40% cold rolling have resulted in the formation of 24% and 315% martensite respectively. Microstructural investigation has demonstrated that the formation of martensite is enhanced with increase in the percent deformation at 0 ℃. Investigation of mechanical properties reveals that hardness, yield strength and tensile strength values increase where as percent elongation drops with increasing deformation. The fractographic observation corroborates the tensile results. Examination of sub-surface at the fractured end of the tensile sample manifests that void/microcrack nucleation occurs in the interfacial regions of the martensite phase as well as at the austenite-martensite interface.     

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.