晶粒尺寸对普碳钢耐工业环境下大气腐蚀性能的影响

用不同轧制及热处理工艺制备了化学成分相同而晶粒尺寸不同的3种普碳钢试样。采周浸、锈层横截面微观分析、交流阻抗测试等手段对晶粒尺寸与普碳钢耐工业环境下大气腐蚀性能之间的规律进行了研究,同时测定了不同晶粒尺寸的普碳钢在10％硫酸溶液中的极化曲线。结果表明,普碳钢晶粒尺寸从50um减小到4um,周浸加速腐蚀试验后锈层中裂纹和空洞的数量也相应减少,耐蚀性能提高;但极化曲线试验表明,晶粒细化可加速普碳钢在10％H2SO4溶液中的腐蚀速度。分析了晶粒尺寸对晶界局部阳极腐蚀电流密度的影响,对其影响耐蚀性的机理进行了讨论。     

304不锈钢在硝酸盐及硫酸溶液中的钝化

利用电化学方法和表面分析技术研究了304不锈钢在 硝酸盐及硫酸溶液中的钝化行为.结果表明，304不锈钢经硝酸盐及硫酸溶液中钝化后在3.5%NaCl溶液中的耐蚀性大为提高.SEM分析表明，经过H2SO4+KNO3钝化后，钝化膜具有网状的结构，膜层结合紧密；而单独在H2SO4溶液中钝化后，表面为有裂纹的钝化膜，微孔较多；单独在KNO3溶液中钝化，与未处理的基本相同.     

CYCLIC DEFORMATION OF COARSE GRAINED POLYCRYSTALLINE PURE Ai——Ⅰ.SLIP CHARACTERISTICS

Comparing with ordinary ploycrystalline materials sized to μm grade,the slip morphology ofthe coarse grained polycrystalline pure Al is characterized by:(1)several slip domains occurin a grain,and in same domain,several slip systems operate at same time or one after anotherintensely,a beautiful and neat slip pattern is forming on the specimen surface;(2)for highΣ-value coincident and random grain boundaries,the grain boundary affecting zone(GBAZ),bout 50—120μm wide,is favourable site to form intergranular crack at early fa-tigue life easily,and migration or slide of the boundaries were often observed.While lowΣ-value near-coincident grain boundaries show a higher degree of slip continuity and straincompatibility than high Σ-value ones.Intergranular crack is not easily nucleated at lowΣ-value near-coincident boundaries;and(3)due to suppression of grain boundary slip attriple grain boundary node,the high Σ-value and random grain boundary among the threeboundaries of tricrystal crack easily during cyclic deformation.     

晶粒尺寸对超低碳IF钢耐大气腐蚀性能的影响

采用不同轧制及热处理工艺制备了化学成分相同而晶粒尺寸不同的3种超低碳IF钢试样.采用浸泡腐蚀、周浸腐蚀、原子力显微镜(AFM)及扫描电镜(SEM)微观分析、电化学阻抗测试等手段对晶粒尺寸与IF钢耐大气腐蚀性能之间的规律进行了研究.AFM及SEM微观分析结果表明,随着晶粒尺寸从15μm增加到220μm,超低碳IF钢浸泡腐蚀后晶界处的局部腐蚀更加严重,腐蚀裂纹处的深度加深,裂纹宽度变宽.超低碳IF钢晶粒尺寸从15μm增加到46μm,周浸腐蚀实验后锈层中空洞和裂纹增多,锈层电阻下降,耐候性下降;晶粒尺寸进一步增大到220μm后,锈层整体致密性得到增加,锈层电阻上升,耐候性得到增加.对晶粒尺寸影响耐大气腐蚀性能的机理进行了讨论.晶粒尺寸增大后晶界能的减少使得腐蚀表面的宏观总体缺陷数量有所减少,耐候性有所提高;但是晶粒尺寸增大后晶界处因局部腐蚀电流密度增大将会在局部造成更深的腐蚀坑槽并降低耐候性;晶粒尺寸的变化对钢铁材料耐大气腐蚀性能的影响不仅要考虑其对晶界局部腐蚀电流密度的影响,而且还必须考虑对基体整体晶界能所造成的影响.     

SO2-4 ,PO3 4- 对曼尼希碱酸化缓蚀剂缓蚀性能的影响

目的：研究废酸液中介质离子对曼尼希碱酸化缓蚀剂缓蚀性能的影响,以解决碳钢在酸液中的腐蚀问题。方法采用静态失重法、极化曲线、扫描电镜及能谱分析法,研究SO2-4,PO3-4对曼尼希碱型酸化缓蚀剂缓蚀性能的影响,并探究其作用机理。结果在10%(质量分数)盐酸、0.1%(质量分数)曼尼希碱的缓蚀介质中,随SO2-4质量分数的增大,腐蚀电流密度由2.81μA/cm2增加至7.32μA/cm2,腐蚀速率显著增大,缓蚀效果变弱;随PO3-4质量分数的增加,腐蚀电流密度由2.81μA/cm2减小至2.41μA/cm2,腐蚀速率减小,缓蚀效果变强。结论 SO2-4会通过钢铁表面已经形成的吸附膜上的细孔和缺陷渗入膜内,使膜发生开裂,从而侵蚀和破坏已经形成的吸附膜,抑制缓蚀剂的缓蚀效果;PO3-4与腐蚀产物Fe3+络合并在钢材表面形成一层致密的保护层,使缓蚀剂形成的吸附膜更加致密,阻止腐蚀性介质与金属表面接触,同时增加对离子或溶解氧的扩散阻力,提高缓蚀剂的缓蚀效果。     

Al/Cr复合涂层对Ti2AlNb合金抗热腐蚀性能的影响

目的改善Ti2AlNb合金在高温腐蚀盐环境中的耐热腐蚀性能。方法在Ti2AlNb合金表面通过双层辉光等离子渗铬及磁控溅射镀铝技术制备Al/Cr复合涂层,分析涂层热腐蚀前后的微观形貌和物相组成,并探究涂覆Na2SO4盐膜的试样在不同温度下(750、850、950℃)的热腐蚀行为。结果Al/Cr复合涂层组织均匀致密,且与基体结合良好,厚度约73μm,由表及里依次由Al沉积层、Al/Cr合金层、Cr沉积层、Cr扩散层四部分组成。经不同温度Na2SO4盐热腐蚀后,Al/Cr复合涂层腐蚀程度均显著小于合金基体。涂层试样经750~850℃Na2SO4盐热腐蚀后质量变化较小,850℃腐蚀增重仅0.525 mg/cm^2,而经历950℃、40 h熔盐热腐蚀后失重达到73.571 mg/cm^2,且试样截面出现剥离、脱落现象,Al/Cr复合涂层抵抗热腐蚀能力减弱。结论具有涂层保护的试样抗热腐蚀性能明显优于合金基体。Al/Cr复合涂层在750~850℃Na2SO4盐环境中具有良好的热腐蚀抗力,而更高温度段(850~950℃)的热腐蚀抗力下降。Al/Cr复合涂层在Na2SO4盐环境中良好的抗热腐蚀性得益于涂层中Al、Cr元素氧化形成以Al2O3、Cr2O3为主的混合氧化膜,有效阻碍外界氧气及腐蚀性介质侵入基体。     

余热锅炉省煤器管腐蚀原因分析

 对在役使用的余热锅炉省煤器管进行了现场取样,经化学成分分析、机械性能测试,省煤器管束符合材质要求.通过外观检验、壁厚测量、扫描电镜、能谱和X射线衍射,对省煤器管腐蚀原因进行了分析.结果表明,余热锅炉以瓦斯气作为燃料,总硫含量波动大,硫分在燃烧时绝大部分变成了SO2,其中有一部分可进一步氧化成SO3,SO3与水汽作用而在省煤器低温部位凝结成H2SO4.腐蚀产物分析证实蚀坑内腐蚀产物为硫酸铁,管外表面附着物经检测也有其它硫酸盐形式.证实管外表面蚀坑处于易于形成露点的位置管材外表面局部腐蚀是因露点腐蚀造成.露点腐蚀蚀坑深达0.9mm,并已连片出现,难以满足省煤器管使用条件.管内表面腐蚀产物主要为Fe2O3,说明管内表面受除氧水均匀腐蚀.      

原位反应合成Mo-Ni-B系三元硼化物熔覆层的研究

利用氩弧熔覆的方法,在镍基高温合金基体上原位反应合成了Mo∶B原子比从0.8到1.2的Mo-Ni-B系三元硼化物熔覆层,利用X射线衍射仪、扫描电镜、能谱仪、显微硬度计分析了熔覆层的物相组成、显微组织和显微硬度.结果表明,熔覆层主要为三元硼化物M3B2硬质相和Ni、Mo组成的粘结相,其显微硬度在700～800 HV之间.在5vol%H2SO4溶液中,熔覆层的腐蚀速率在(0.19～0.94)μm/h,其中Mo∶B原子比为1的熔覆层显示了最好的抗腐蚀性.     

EFFECT OF CERIUM ION IMPLANTATION ON THE AQUEOUS CORROSION BEHAVIOR OF ZIRCONIUM

1.IntroductionBecause of the low thermal neutron capture cross section, adequate mechanical properties and good corrosion resistance, zirconium and its alloys are often specified for engineering in the nuclear industry. For example, it can serve as fuel cladding and core structure material. However, with the concept of high burn-up developing, enhancement of performance of zirconium and its alloys increasingly required. It is well known that ion beam surface processing (IBP) techniques can s…     

CORRELATION BETWEEN MICROSTRUCTURE AND STRESS CORROSION CRACKING SUSCEPTIBILITY OF 2091 ALLOY

The stress corrosion cracking(SCC) susceptibility of an Al-Li-Cu-Mg-Zr alloy(2091),heat-treated under different regime,has been investigated hy means of tensile tests atslow strain rate.The microstructure has been examined with TEM.The deformationcharacteristic has also been analysed.The stress corrosion resistance of the alloy wasrevealed to be mainly affected by the covering rate of T_2-phase over grain boundariesand by the average distance between T_2-phase particles.SCC resistance can be obviously improved by predeforming the alloy at room temper-ature to reduce the precipitation of T_2-phase along grain boundaries.     

Enhancing the intergranular corrosion resistance of high Mg-alloyed Al–Mg alloy by Y addition

Microalloying is thought to improve the performance of Al–Mg alloys commonly used in transport applications. The effect of Y addition (0–0.4%) on the microstructure, mechanical properties, and corrosion resistance of Al–9.2Mg–0.7Mn alloy is investigated for potential use in engineering applications. The generation of the β-Al₃Mg₂ phase along the grain boundaries is suppressed in the as-cast alloy due to the formation of the AlMgY ternary phase. The average intergranular corrosion mass loss of the alloy with 0.1% Y addition decreases about 53.1% almost at no expense of mechanical performance in the as-rolled alloy after annealing. Moreover, the alloy with 0.1% Y addition shows the corrosion mass loss about 30.2% lower than the Y-free alloy in the sensitized state. The enhanced corrosion resistance of the alloy can be ascribed to the reduced β-Al₃Mg₂ precipitation along the grain boundaries associated with Y addition.     

Interfacial diffusion in Cu with a gradient nanostructured surface layer

A graded microstructure was produced in the surface layer of a pure Cu sample by means of surface mechanical attrition treatment (SMAT) [Wang K, Tao NR, Liu G, Lu J, Lu K. Acta Mater 2006;54:5281.]. The diffusion behavior of ⁶³Ni in such a surface layer was investigated by the radiotracer technique at temperatures <438 K. It is shown that the effective diffusivity in the top 10 μm surface layer is more than 2 orders of magnitude higher than that along conventional high-angle grain boundaries (HAGB) in Cu of similar purity. The diffusion rate increases gradually with increasing depth up to 30–50 μm, and then decreases with further increasing depth. The enhanced diffusivities reveal higher-energy states of various interfaces in the SMAT surface layer. The excess free energy of HAGB in this layer is estimated to be ～30% higher than that of conventional grain boundaries. An apparent retardation of the effective diffusion rate in the top 25 μm surface layer is induced by tracer leakage into numerous twin-boundary-like interfaces, while the gradual decrease in interface excess free energy correlates with the observed decrease in diffusivity in the subsurface layer at depths exceeding 50 μm.     

Quantitative Studies of Machining-Induced Microstructure Alteration and Plastic Deformation in AISI 316 Stainless Steel Using EBSD

Surface machining can result in a heavily plastic deformed layer in the subsurface. The microstructure alterations and the extent of plastic deformation of a milled 316 austenitic stainless steel were investigated using electron backscatter diffraction (EBSD) technique in this study. The microstructure alteration of the deformed layer was characterized by the generation of grain and subgrain boundaries. The plastic deformation was evaluated by kernel average misorientation (KAM) and grain average misorientation (GAM). The local deformation within grains was assessed by the misorientation from adjacent point (MFAP). The EBSD results indicated gradients of microstructure and plastic deformation along the depth direction. High-angle grain boundaries were generated within the depth of 40 μm, and subgrain boundaries were produced up to the depth of 150 μm. Estimated by KAM and GAM, the plastic strain was about 0.7 at the depth of 25 μm and decreased to 0.1 at the depth of 115 μm The MFAP analysis revealed that the local deformation varied within individual grains. Additionally, the change of micro-hardness along the depth direction showed a strong correlation with KAM and GAM values.     

锆合金在HCl和H2SO4溶液中的耐蚀性能研究

采用化学浸泡、电化学测试和物理检测技术,研究了HCl和H2SO4溶液中锆合金的腐蚀行为.结果表明,锆合金在还原性的HCl和低浓度H2SO4溶液中,具有优异的耐蚀性,而在高浓度的氧化性H2SO4溶液中腐蚀速率显著增大.物理检测结果显示,腐蚀的锆合金表面均匀地覆盖着弥散分布的微小颗粒状ZrO2.还原性的HCl和低浓度H2SO4溶液中ZrO2膜保持了原有的致密性,增强了锆合金的耐蚀性能.而高浓度H2SO4溶液中,在其强氧化作用下,锆合金基体/膜界面处不断生成ZrO2.当膜增加到一定厚度时,氧化膜的晶格参数与金属的晶格参数不一致,产生内应力,降低了氧化膜的附着力,直至氧化膜破裂,露出新鲜的锆合金表面.继之,新鲜的锆合金再次被氧化,以此循环往复,导致锆合金在浓H2SO4溶液中腐蚀加剧.     

铁基非晶基涂层的HVOF制备及耐腐蚀性能(英文)

以工业原材料制备的铁基非晶合金、镍铬合金、碳化钨颗粒的混合粉末为原材料,采用高速火焰喷涂技术制备铁基非晶基涂层。通过分析铁基非晶基涂层分别在1 mol/L盐酸、氯化钠、硫酸和氢氧化钠溶液中的动态极化特性,研究其腐蚀阻抗。采用扫描电子显微镜(SEM)分析涂层的腐蚀形貌。结果表明:铁基非晶基涂层具有优良的耐蚀性能,而且在含氯离子溶液中,表现出比304L奥氏体不锈钢更高的腐蚀阻抗。在1 mol/L盐酸溶液中,铁基非晶基涂层的腐蚀电流密度和钝化电流密度分别为132.0μA/cm2和9.0 mA/cm2,在1 mol/L氯化钠溶液中分别为2.5μA/cm2和2.3 mA/cm2,且表现出一个宽的自钝化区间。其优异的耐蚀性能表明铁基非晶基粉末可以作为一种耐腐蚀、耐磨损的工程材料。     

单相和双相不锈钢纳米涂层的电化学腐蚀行为

用磁控溅射技术在玻璃基体上制备由两种相组成(单相和双相)的不锈钢纳米涂层,利用动电位极化､交流阻抗技术及扫描电子显微镜研究两种不锈钢纳米涂层在0.25 mol/L Na2SO4 + 0.05 mol/L H2SO4 和 0.5 mol/L NaCl + 0.05 mol/L H2SO4溶液中的电化学腐蚀行为,观察相组成对纳米不锈钢涂层耐蚀性能的影响｡结果表明,与不锈钢单相涂层相比,不锈钢双相纳米涂层具有较差的抗局部腐蚀能力,其钝化膜的载流子密度远远大于不锈钢单相钝化膜的载流子密度,使得钝化膜的离子传输能力大大增强,从而降低了钝化膜的稳定性｡     

Ni-P/Ni-Zn-P双层复合镀层制备及耐蚀性的研究

目的提高金属材料在海洋环境下的耐蚀性。方法采用化学镀方法在Q235碳钢表面施镀Ni-Zn-P合金镀层和Ni-P/Ni-Zn-P双层复合镀层,采用扫描电镜(SEM)和能谱分析仪(EDS)对镀层表面形貌和断面成分进行了分析。结果 Ni-P/Ni-Zn-P双层复合镀层相对于Ni-Zn-P合金镀层胞状组织更加均匀平滑,胞与胞的边界结合更加连续致密。Ni-Zn-P合金镀层断面厚度为6.5μm左右,锌和磷的质量分数分别约为4%和14%。Ni-P/Ni-Zn-P双层复合镀层断面总厚度约7.5μm,内层镀层的厚度约2.3μm,磷的质量分数约为9%;外层镀层厚度约5.2μm,锌和磷的质量分数分别约为5%和11%。在5%Na Cl溶液中腐蚀144 h后,Ni-Zn-P合金镀层遭到了严重的破坏,有许多裂纹,而Ni-P/Ni-Zn-P双层复合镀层仍然连续完整,没有严重的破损,只是局部腐蚀,这说明双层镀层更耐蚀。结论 Ni-P/Ni-Zn-P双层复合镀层腐蚀速率明显低于Ni-Zn-P合金镀层,相对于Ni-Zn-P合金镀层耐蚀性更好。     

腐蚀高强Q690D钢板耐腐蚀性能及其机理研究

针对矿井用耐蚀高强钢的开发,介绍了新型耐蚀高强Q690D钢板化学成分、组织及力学性能。主要通过盐雾试验及电化学试验对普通Q690D、耐蚀Q690D钢板的耐蚀性能进行了测试,分析了耐蚀钢的多因素耦合的腐蚀规律,揭示了耐蚀钢的腐蚀机制。结果表明:耐蚀Q690D钢板中较高的Cr元素有利于降低试验钢基体表面的电位差,降低腐蚀倾向;钢板组织状态不同,表面电位差也有一定差异,耐蚀Q690D钢板经淬火+回火处理后得到的回火马氏体/贝氏体组织,强韧良好,耐蚀性较普通Q690D钢板提高1.5倍。EBSD表征结果表明:小角度晶界由于其高度有序结构,具有较小的自由体积和较低的界面能,能够打断大角度晶界的连通性,能够有效地阻断腐蚀沿着大角度晶界的扩展,所以腐蚀速率会随着小角度晶界比例的上升而下降。     

2091合金的显微组织与应力腐蚀敏感性

用慢应变速率拉伸试验研究不同热处理状态Al—Li—Cu—Mg—Zr(2091)合金的应力腐蚀敏感性,用透射电镜观察显微组织结构并分析变形特性。结果指出,T_2相在晶界上的复盖程度及T_2相之间的平均间距是影响合金应力腐蚀敏感性的主要因素,室温预形变处理可减少晶界上T_2相的数量,使合金应力腐蚀抗力得到明显提高。     

Effects of cooling rate on the precipitation behavior of grain boundary carbide and corrosion resistance of 5Cr15MoV stainless steel

High-carbon and high-chromium alloy steels are prone to pitting and intergranular corrosion, which reduces corrosion resistance. The precipitation behavior of the carbides of high-carbon and high-chromium alloy steels is one of the main factors affecting pitting and intergranular corrosion of stainless steel. In this study, 5Cr15MoV stainless steel was heated to 1,200℃ and then cooled by cooling rates varying from 25 to 150°C/min. The precipitation behavior of grain boundary carbides of 5Cr15MoV steel at different cooling rates, and its effect on the corrosion resistance of materials was studied. The results show that the carbides of 5Cr15MoV steel mainly precipitate along the grain boundaries, which leads to the formation of chromium-depleted zones near the grain boundaries and reduces resistance to intergranular corrosion. It has been found that a higher cooling rate shortens the width of the Cr-depleted zone near the boundary from 0.871 to 0.569 μm, reduces the Cr-concentration gradient near the grain boundary from 36.422% to 12.667%, and suppresses the nucleus growth rate of grain boundary carbides. As the cooling rate increases, the corrosion current density decreases from 13.29 to 2.42 μA/cm². The corrosion rate is the lowest, while the cooling rate is 150°C/min. The corrosion rate decreases from 218.339 to 158.488 mm/a. The phenomenon of intergranular corrosion and pitting corrosion was found to be weakened; and thereby, it is shown that an intensive cooling rate can improve the corrosion resistance of 5Cr15MoV steel.