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.     

Development of high corrosion-resistant ferritic stainless steel and its application in the building cladding system

Effects of Mo, Nb, Ti on mechanical properties and corrosion resistance of 22.5%Cr ferritic stainless steel were investigated. The results show that Mo exists in ferritic stainless steel mainly in the solution treatment condition, and it can enhance steel’s strength through solid solution strengthening. In Ti+Nb dual-stabilized ferritic stainless steel, the steel’s toughness decreases obviously because coarse TiN particles form and some metallic compounds precipitate along the grain boundaries. In Nb single-stablized ferritic stainless steel, Nb exists either in the solution treatment condition or in the form of dispersed precipitates Nb(C, N), which will act as the nuclei of precipitation of the fine σ phase. As a result, the precipitation of the coarse σ phase along the grain boundary can be inhibited, leading to significant improvement in steel’s toughness at a low temperature. Based on these, high corrosion-resistant ferritic stainless steel B445R was developed for the building cladding system. Test results show that B445R has a superior corrosion resistance to austenitic 316 L in chloride solution. Besides, it has a good forming property and weldability. All these make it an ideal decorating material for the building cladding system in severe coastal regions.     

Surface Nanocrystallization of Nb-Ti Stabilized 439M Ferritic Stainless Steel

A new nanocrystallization process was designed, which included punching the surface coating to generate dislocation network or cells and recovery treatment to turn the dislocation cells into nano-sized grains. The effort was made to increase the service life of Nb-Ti stabilized 439M stainless steel surface with medium passive ability, particularly to enhance the outmost surface layer by nanocrystallization for improving resistances to corrosion. Electrochemical properties, electron work functions （EWFs）, nano-mechanical properties of the nanocrystallized surfaces were investigated. It was demonstrated that the nanocrystallized 439M stainless steel surface exhibited improved resistance to corrosion in 0.5 mol/L H2 SO4 solution. However, the nanoci＇ystallized 439M stainless steel surface exhibited decreased resistance to corrosion in 3.5% NaCl solution.     

Laser Surface Alloying of Low Carbon Steel Using High-entropy Alloy Precursors

The Al_(0.5)CoCrCuFeNi high-entropy alloy powders with simple face-centered-cubic(FCC)solid solution structure were introduced into the surface layer of a low carbon steel during laser surface alloying.A high performance surface layer with extremely fine martensite as the dominant phase was obtained,resulting in a great improvement in microhardness,wear resistance,and corrosion resistance.The great enhancement of microhardness and wear resistance of the laser alloyed layer is mainly due to the formation of extremely fine martensite hard phase,the solid solution strengthening of the alloying elements in supersaturatedα-Fe solid solution,and the existence of size effect and strain effect under rapid solidification.The enhancement of corrosion resistance is due to the alloying of Al,Co,Ni,Cr and Cu in the laser alloyed layer.     

Microstructure Characteristic and Electrochemical Corrosion Behavior of Surface Nano-crystallization Modified Carbon Steel

The surface nano-crystallization( SNC) of carbon steel was achieved via a high-speed rotating wire-brushing process.Microstructure characteristics of SNC steel were systematically studied.The SNC steel surface exhibited marked deformed plastic flows and high surface roughness.Due to the accumulated strains,a deformed gradient layer with thickness of 40-50 μm was produced,and the grain size of the topmost zone was about 50-100 nm.X-ray photoelectron spectroscopy( XPS) analysis indicated that enhanced Fe oxides and Cr oxides were generated.Electrochemical corrosion tests,including open circuit potential( OCP),electrochemical impendence spectroscopy( EIS),potentiodynamic polarization( PDP) and potentiostatic polarization( PP) were conducted to study the corrosion behavior of SNC steel in 3.5 mass% Na Cl solution,where an improved corrosion resistance was observed.The resulted improvement resulted from the dominated positive effects( the attached Cr alloying element and enhanced oxide film) against the negative effects( the higher roughness and the improved corrosion activity of surface microstructure).     

Effect of Aging Temperature on Erosion-Corrosion Behavior of 17-4PH Stainless Steels in Dilute Sulphuric Acid Slurry

The effect of aging temperature on erosion corrosion （E-C） behavior of 17-4PH stainless steels in dilute sulphuric acid slurry containing solid particles was studied by using self-made rotating E-C apparatus. The effect of impact velocity on EC behavior of 17 4PH steels at different aging temperatures was analyzed. Surface micrographs of the specimens after E C test were observed by using scanning electron microscope （SEM）. The results showed that under the condition of the same solution heat treatment, when aging temperature ranged from 400 ℃ to 610℃, the hardness reached the highest value near the temperature 460℃. The characteristics of E-C for 17-4PH stainless steels at different aging temperatures were as follows： pure erosion （wear） was dominant, corrosion was subordinate and at the same time corrosion promoted erosion. The effect of aging temperature on E-C rate of 17-4PH steels was not significant at low impact velocity, but it was found that E-C resistance of 17-4PH steels aged near 460℃ was the most excellent due to the best precipitation strengthening effect of fine and dispersed e-Cu phase. With a prerequisite of appropriate corrosion resistance, the precipitation hardening could significantly improve the E-C resistance of the materials.     

Comparison of microstructure and property of high chromium bearing steel with and without nitrogen addition

Microstructure and property of bearing steel with and without nitrogen addition were investigated by microstructural observation and hardness measurement after different heat treatment processing. Based on the microstructural observation of both 9Cr18 steel and X90N steel,it was found that nitrogen addition could effectively reduce the amount and size of coarse carbides and also refine the original austenite grain size. Due to addition of nitrogen,more austenite phase was found in X90N steel than in 9Cr18 steel. The retained austenite of X90N steel after quenching at 1 050 °C could be reduced from about 60% to about 7% by cold treatment at-73 °C and subsequent tempering,and thus finally increased the hardness up to 60 HRC after low temperature tempering and to 63 HRC after high temperature tempering. Furthermore,both the wear and corrosion resistance of X90N steel were found much more superior than those of 9Cr18 steel,which was attributed to the addition of nitrogen. It was proposed at last that nitrogen alloying into the high chromium bearing steel was a promising way not only to refine the size of both carbides and austenite,but also to achieve high hardness,high wear property and improved corrosion resistance of the stainless bearing steel.     

Influence of Surface Roughness of Galvanized Steel Sheet on Self-lubricated Coating

Three different thicknesses of self-lubricated coatings were prepared on galvanized steel sheets with different surface roughness(Ra).Performances of the coatings were evaluated by various laboratory tests.Scanning electron microscopy(SEM),atomic force microscope(AFM),neutral salt spraying test(NSST),reciprocating friction and wear test were taken in order to characterize the coatings.Results show that the self-lubricated coating has good corrosion resistance and lubricating property.In 0.857-1.629μm of Ravalue,the relationship between friction coefficients of the self-lubricated steel sheets and the surface roughness of the galvanized steel sheets likes a parabolic curve,and has a peak value of friction coefficient in certain range of Ra.Affected by the hereditary surface topography of the galvanized steel sheet,dents on the surface of self-lubricated steel become deeper and larger with the increase of the surface roughness of the galvanized steel sheets.The influence of the surface roughness of the galvanized steel sheet on the corrosion resistance of the self-lubricated coating steel is similar to that on friction coefficient of self-lubricated coatings,like a parabolic curve.     

Dry Sliding Oxidative Wear in Plain Carbon Dual Phase Steel

 To investigate the tribological potential of the dual phase (DP) steel as a wear resistant material, the wear and the friction characteristics of this steel, which consists of hard martensite islands embedded in a ductile ferrite matrix, have been investigated and compared with those observed in plain carbon hardened (H) steel that has the same carbon content of 02%. Dry sliding wear tests have been carried out using a pin on disk wear testing machine at different normal loads of 213 N, 285 N, 357 N, and 426 N and at a constant sliding velocity of 120 m/s. The analysis of surface and wear debris of samples showed that the wear mechanism was mainly mild oxidative. The friction and the wear rate of the H steel and the DP steel have been explained with respect to the microstructure and the wear mechanism.     

Effects of Cu on Corrosion Resistance of Low Alloyed Steels in Acid Chloride Media

The corrosion resistance of two kinds of low alloyed steels was studied according to the test procedures for qualification of corrosion resistant steel for cargo oil tanks issued by International Maritime Organization.The results indicated that the addition of Cu improved the corrosion resistance of the NS-D36 steel to more than three times that of the conventional D36 steel in the strong acid solution containing chloride(10% NaCl,pH=0.85).The anodic polarization behavior of the copper-bearing steel was studied by polarization curves and electrochemical impedance spectroscopy(EIS),and alloying element Cu showed beneficial effects including an active potential range,low current density and high transfer resistance of electric charge.The rust layer was analyzed by scanning electron microscopy(SEM)and Auger electron spectroscopy(AES),and the results pointed out that the mechanism of copper′s beneficial effects was based on the suppression of anodic dissolution by metallic copper re-deposition on the steel surface immersed in the strong acid chloride media.     

稀土Ce对1Cr18Mn8Ni5N不锈钢耐均匀腐蚀性能影响

利用电化学的极化曲线及交流阻抗技术研究了不同稀土含量的1Cr18Mn8Ni5N不锈钢在硫酸介质中的腐蚀行为。应用扫描电镜对试样的腐蚀形貌及夹杂物形态进行了观察,利用EDS对夹杂物成分进行了分析。结果表明:钢中加入稀土Ce可改变夹杂物形态,并使其交流阻抗的极化电阻增大,极化曲线的腐蚀电位正移,降低了腐蚀电流密度,抵制了均匀腐蚀,改善了1Cr18Mn8Ni5N不锈钢的耐蚀性。当钢中稀土Ce质量分数为0.022%时,1Cr18Mn8Ni5N不锈钢可获得最好的耐均匀腐蚀性能。     

Corrosion resistance of high-strength austenitic chromium–nickel–manganese steel containing nitrogen

The corrosion resistance of high-strength Cr–Ni–Mn austenitic steel containing nitrogen and copper is compared with that of Cr18Ni9 and Cr18Ni10N chromonickel steel by means of the Zive MP2 electrochemical system. The polarization curves and electrochemical characteristics of the alloys are determined in general, pitting, and intercrystallite corrosion by various media: aqueous solutions of NaCl (3%); FeCl₃ 6H₂O (100 g/L); H₂SO₄ (0.5 M); H₂SO₄ (0.5 M) + injected H₂S; and H₂SO₄ (0.5 M) + KSCN (0.01 M). The corrosion rates are calculated. The results indicate that all the steel samples are corrosion-resistant: they exhibit high resistance to intercrystallite corrosion and also to pitting and general corrosion in chloride-bearing media. No pitting corrosion is observed when Cr–Ni–Mn steel of balanced composition containing nitrogen (and especially steel containing both nitrogen and copper) is immersed in sea water, even when the steel’s nickel content is low. This steel outperforms traditional Cr18Ni9 steel in terms of strength and corrosion resistance, even in an acidic medium (0.5 M H₂SO₄).     

新型CrMnNiN奥氏体不锈钢的抗空穴腐蚀及磨损性能

对新型CrMnNiN不锈钢JA2（0．23C－13Mn-17Cr-1.90Ni-1.5Mo-1Si-0.33N)的抗空穴腐蚀及磨损性能进行了测试，结果表明，这种奥氏体高锰不锈钢具有高的加工硬化率和好的韧性，比目前水轮机转轮及叶片常用的0Cr13Ni5Mo有更高的抗空穴腐蚀性能及耐泥沙磨损性能。     

双辊薄带连铸0Cr18Ni9不锈钢的直接冷轧研究

为了改善双辊薄带连铸技术得到的0Cr18Ni9不锈钢薄带的表面质量和综合力学性能,对0Cr18Ni9不锈钢薄带进行了直接冷轧的研究.结果表明,不锈钢薄带经直接冷轧后,组织和性能都有明显的改善,各向异性不明显,耐腐蚀性能大大提高,从而论证了0Cr18Ni9不锈钢薄带直接冷轧的可行性.     

易切削奥氏体不锈钢303F和316F的机加工性能

仪器仪表用３０３Ｆ，３１６Ｆ，Ｃａ－Ｓ易切削奥氏体不锈钢的切削，钻削加工性能分别优于０Ｃｒ１８Ｎｉ９和０Ｃｒ１８Ｎｉ１２Ｍｏ２不锈钢。     

Electrochemical polarization and passive film of a cryogenic and non-magnetic steel in aqueous solution

The corrosion behaviour of the austenitic steel Fe-23Mn-4Al-5Cr-0.3C in different aqueous solutions of pH-0.8 to 15.3 and the corrosion protection mechanism induced by adding Al or Al and Cr have been investigated by electrochemical measurements and AES/XPS analysis. The corrosion behaviour of Fe-Mn base steel have been compared with those of mild steel, cryogenic 9 % Ni steel, stainless steels 1Cr13 and 1Cr18Ni9Ti. The addition of manganese to mild steel is very detrimental to the corrosion resistance. Fe-25Mn steel passivates with difficulty even in such neutral aqueous electrolytes as 1 M Na₂SO₄ solution. The addition of 5 % aluminum to Fe-25Mn steel confers passivity to the steel in neutral or oxidizing, chloride-free solution. The addition of 5 % Cr to Fe-Mn-Al steel further improves resistance to corrosion. The passivity of Fe-23.5Mn-4Al-5Cr-0.3C steel in aqueous electrolytes tested is superior to that of 9 % Ni steel and approximate to that of 1Cr13 stainless steel. The corrosion resistance is probably imparted by a thin barrier film of oxides. The outer part of the passive film formed on the surface of Fe-23.5Mn-4Al-5Cr-0.3C steel in 1 M Na₂SO₄ solution is enriched in Al³⁺, Cr³⁺ and Fe³⁺, and this means that the film is probably made up of a mixture of Al₂O₃, Cr₂C₃ and Fe₂O₃.     

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。     

Influence of Microalloying on the Strength and Corrosion of Low-Carbon Stainless Steel

Attention focuses on how nitrogen and rare-earth metals modify the mechanical properties and corrosion characteristics of unstabilized low-carbon Fe–Cr–Ni stainless steel, additionally alloyed with silicon and molybdenum. The influence of the selected microalloying method on the mechanical properties of unstabilized low-carbon chromonickel stainless steel and its resistance to local corrosion is studied experimentally. Nitrogen-bearing 03X17H9AC2, 03X17H9AM3, and 03X18H15AM3 stainless steel microalloyed with rare-earth metals is investigated.     

AOD炉冶炼含氮不锈钢氮合金化工艺开发

介绍了AOD炉运用氮气在不锈钢中溶解与脱除理论所开发的氮合金化工艺。在40tAOD炉上冶炼0Cr19Ni9N,0Cr19Ni9NbN,1Cr17Mn6Ni5N,00Cr18Ni5Mo3Si2（N）,00Cr22Ni5Mo3N等舍氮不锈钢钢种。不需在线分析钢中氮含量，较为准确地预测与控制钢中氮溶解度值及舍氮不锈钢成品的氮含量。     

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。