Corrosion Behavior of a Sputtered K38G Nanocrystalline Coating with a Solid NaCl Deposit in Wet Oxygen at 600 to 700°C

A nanocrystalline coating of K38G alloy was obtained by means of magnetron sputtering. The corrosion behavior of cast K38G alloy and its sputtered nanocrystalline coating with a solid NaCl deposit in dry air or wet oxygen at 600 and 700°C have been studied and compared. The results indicated that the mass gain of the coating is higher than that of the cast alloy at 600 and 700°C. Therefore, nanocrystallization reduced the corrosion resistance at these temperatures. Furthermore, the mass gains of the coating and the cast alloy with a NaCl deposit in wet oxygen were less than that with a NaCl deposit in dry air. The relevant corrosion mechanisms are discussed.     

1Cr18Ni9Ti不锈钢微晶的耐局部腐蚀性能研究

利用磁控离子溅射技术得到bcc结构的1Cr18Ni9Ti不锈钢微晶溅射层,在不同溅射条件下可以得到(110)和(211)两种择优取向的微晶。用电化学方法研究表明,这两种微晶的耐局部腐蚀性能都较正常晶粒有明显提高,且(110)择优取向微晶的耐局部腐蚀性能较(211)择优取向微晶的耐局部腐蚀性能更好。     

K38G合金及其溅射微晶层的高温氧化

研究了K38G铸造镍基高温合金及其用平面磁控离广溅射工艺制备的微晶涂层在800-1000℃500小时内的抗高温氧化性。结果表明,微晶化极大改善合金的抗氧化能力,并改变合金表面生成的氧化物类型,由Cr_2O_3变为α-Al_2O_3。还讨论了铸态K38G合金及溅射微晶层的氧化机理。     

LOCALIZED CORROSION OF MICROCRYSTALS OF 1Crl8Ni9Ti STAINLESS STEEL

The resistances against localized corrosion of 1Cr18Ni9Ti microcrystals with normal grainsize and bcc structure obtained hy magnetron sputtering have been compared.The two kindsof microcrystals with (110) and (211) textures respectively were obtained under differentsputtering conditions.Both microcrystals were found to have better resistance against local-ized corrosion than the crystal with normal grain.The microcrystal with (110) preferredorientation has larger resistance to localized corrosion than that with (211) preferredorientation.     

钼酸铵复合缓蚀剂对LY12铝合金的缓蚀作用

采用电化学方法研究了钼酸盐、锌盐和苯并三氮唑 (BTA)对LY12铝合金在 3 5 %NaC1溶液中的缓蚀作用。结果表明 ,随着钼酸盐浓度的增大 ,缓蚀效率增大 ,达到一个最大的值后基本保持不变。钼酸盐通过抑制铝合金的阴极反应和阳极溶解实现缓蚀作用。钼酸盐与锌盐和BTA复合后 ,明显提高了对铝合金的缓蚀作用 ,表现出良好的协同效应     

The characterization and corrosion resistance of cerium chemical conversion coatings for 304 stainless steel

A golden yellow-colored cerium conversion coating was obtained on 304 stainless steel surface by immersing the steel into a solution containing cerium (III), KMnO₄ and sulfuric acid. The corrosion resistance of the coatings was evaluated by electrochemical methods, potentiodynamic polarization experiments and electrochemical impedance spectrum. The experimental results indicated that the corrosion resistance for the conversion coated 304SS in 3.5% NaCl solution increased markedly. The corrosion potential of the treated steel increased to a more noble level, the pitting corrosion potential increased also, the passive potential range was enlarged markedly and the passive current density decreased about one order compared to that of the untreated steel. The cathodic and anodic reaction were both inhibited to some extent. The chemical state of the elements in the coatings was investigated by XPS. The cerium element was in the form of tetravalent state. And AES depth profile analysis suggested that the thickness of the conversion coatings was less than 66 nm. The mechanisms of coatings formation and corrosion resistance are discussed.     

Oxidation behavior of TiAl coated with a fine-grain Co-30Cr-4Al film

The oxidation behavior of TiAl coupons coated with a fine-grain Co-30Cr-4Al (mass %) film of about 30-m thickness has been studied at 1100–1400 K in a flow of purified oxygen at atmospheric pressure for up to 500 ks. Three oxidation stages were recognized: initial transient, parabolic, and accelerated stages. However, at 1100 K a parabolic stage continues for more than 800 ks. The activation energy for parabolic oxidation agrees with reported values for the oxidation of alumina-former alloys, although the mass gains during the parabolic stages are relatively small at 1200 and 1300 K. Micropores developed mainly at the scale/coating and coating/substrate interfaces as oxidation proceeded. This is attributable to recrystallization of the coating during oxidation and a Kirkendall effect due to preferential diffusion of Co into the substrate. The accelerated oxidation can be explained in terms of the formation of rutile mounds on the scale.     

电弧离子镀氮化铬涂层的高温氧化

利用电弧离子镀设备在1Cr11Ni2W2MoV不锈钢基体上沉积了CrN涂层，对涂层的抗氧化性能进行了研究。结果表明，CrN氧化生成Cr2O3，氧化反应激活能小于Cr和Cr2N的氧化反应激活能，具有低的氧化速率常数，抗氧化性能良好。氧化过程中发生CrN向Cr2N的相转变，涂层中大的压应力的存在对这一转变起了关键作用。     

纳米Fe-10Cr涂层电化学腐蚀行为影响研究Ⅰ.钝化性能

利用磁控溅射技术制备出了晶粒尺寸为20nm-30nm的Fe—10Cr合金涂层．通过动电位极化曲线、电化学阻抗谱图（EIS）和Mott—Schottky分析等电化学测试手段，探讨了Fe—10Cr纳米涂层在0．05mol／LH2SO4＋0．25mol／LNa2SO4溶液中的钝化性能。发现纳米化使材料的活性溶解增强；在钝化膜形成过程中Cr更容易富集，从而更容易钝化；纳米化后，材料表面钝化膜中的载流子密度下降，化学稳定性提高。     

The influence of TiAlN and enamel coatings on the corrosion behavior of Ti6Al4V alloy in the presence of solid NaCl deposit and water vapor at 450 °C

The corrosion behavior of Ti6Al4V alloy with solid NaCl deposit and water vapor at 450 °C has been investigated. Serious corrosion occurred. In order to improve the corrosion resistance, TiAlN and enamel coatings were prepared, and their effectiveness and corrosion resistance were evaluated. The results indicated that both coatings were effective in protecting the alloy against corrosion induced by NaCl deposit and water vapor at 450 °C. The protection mechanisms of these two coatings were also studied.