Pt-Al涂层在两种熔盐中的高温热腐蚀行为

采用表面涂盐法研究了镍基高温合金上Pt-Al涂层在Na2SO4和Na2SO4+NaCl两种熔盐中的高温热腐蚀行为.结果表明,在Na2SO4熔盐中,Pt-Al涂层具有很好的抗热腐蚀性能,表面只生成一层致密的氧化膜.在Na2SO4+NaCl混合熔盐中,它的抗热蚀性下降,涂层发生了内氧化和内硫化,并且内层NiAl相的腐蚀比外层富Pt相的更严重     

(NiCoCrAlYSiB+AlSiY)复合涂层热腐蚀行为的研究

采用电弧离子镀（AIP）技术在镍基单晶高温合金基体上制备了NiCoCrAlYSiB涂层（普通涂层）和（Ni-CoCrAlYSiB+AlSiY）复合涂层,研究了高温合金基体与2种涂层分别在900和700℃下的涂盐（Na₂SO₄+K₂SO₄和Na₂SO₄+NaCl）热腐蚀行为.结果表明:高温（900℃）热腐蚀条件下,基体合金表面主要生成NiO;普通涂层表面主要生成Cr₂O₃,而且涂层内部出现内氧化和内硫化现象;复合涂层表面主要生成Al₂O₃,外层出现程度较轻的内氧化,涂层表层Al含量仍然较高,维持表面Al₂O₃膜的形成和修复.低温（700℃）热腐蚀条件下,基体合金表面主要生成NiO;普通涂层表面主要生成Cr₂O₃,涂层内部出现严重的内氧化;复合涂层表面也出现了内氧化,高Cr的内层未受腐蚀,有助于提高涂层的抗腐蚀性能.     

(NiCoCrAlYSiB+AlSiY)复合涂层热腐蚀行为的研究

采用电弧离子镀（AIP）技术在镍基单晶高温合金基体上制备了NiCoCrAlYSiB涂层（普通涂层）和（Ni-COCrAlYSiB+AlSiY）复合涂层,研究了高温合金基体与2种涂层分别在900和700℃下的涂盐（Na₂SO₄+K₂SO₄和Na₂SO₄+NaCl）热腐蚀行为.结果表明:高温（900℃）热腐蚀条件下,基体合金表面主要生成NiO;普通涂层表面上要生成Cr₂O₃,而且涂层内部出现内氧化和内硫化现象;复合涂层表面主要生成Al₂O₃,外层出现程度较轻的内氧化,涂层表层Al含量仍然较高,维持表面Al₂O₃膜的形成和修复.低温（700℃）热腐蚀条件下,基体合金表面主要生成NiO;普通涂层表面主要生成Cr₂O₃,涂层内部出现严重的内氧化;复合涂层表面也出现了内氧化,高Cr的内层未受腐蚀,有助于提高涂层的抗腐蚀性能.     

镁合金表面等离子喷涂Al2O3-TiO2陶瓷涂层的耐腐蚀性研究

采用等离子喷涂技术在AZ31镁合金表面制备Al2O3-13％TiO2陶瓷复合涂层,对涂层的微观组织进行了观察分析,测试了涂层的表面硬度.通过极化曲线和浸泡腐蚀试验,对比研究了镁合金基材及喷涂陶瓷涂层的试样在5％ NaCl溶液中的耐腐蚀性能.结果表明:涂层镁合金试样的硬度和耐腐蚀性优于基体镁合金,但当腐蚀液透过涂层孔隙时...     

真空电弧镀Al-Si-Y涂层的热腐蚀行为研究

采用真空电弧镀技术在镍基高温合金基材上制备Al-Si-Y涂层.通过涂盐试验对涂层的热腐蚀性能进行了测试,利用场发射电子显微镜和X射线能谱仪对显微组织进行了观察和成分检测,研究了高温合金基材及Al-Si-Y涂层在900℃条件下不同NaCl Na2SO4含量熔盐中的热腐蚀行为.结果表明,Al-Si-Y涂层能有效提高合金抗热腐蚀性能,对NaCl的加入量不敏感,这与涂层在热腐蚀过程中生成了连续致密的Al2O3氧化膜有关.     

激光熔覆CoCrFeNiSix高熵合金涂层组织及耐蚀性能研究

目的 研究Si含量对CoCrFeNi系高熵合金涂层组织、物相、显微硬度及耐蚀性能的影响.方法 通过激光熔覆技术在45钢基材上制备CoCrFeNiSix(x为物质的量之比,x=0.0,0.5,1.0,1.5,2.0)高熵合金涂层,使用扫描电镜、X射线衍射仪、显微硬度仪、电化学工作站对涂层的显微组织、物相组成、显微硬度、耐蚀性能、腐蚀形貌进行分析研究.结果 CoCrFeNi高熵合金涂层为单一的fcc相,之后随着Si含量的提升,涂层向bcc相转变,当x=2.0时,全部转化为bcc相.涂层的微观组织以等轴晶与枝晶为主,当Si含量较少时,Si元素主要在晶界中偏析,随着Si含量的增加,过多的Si会固溶到晶粒内部.涂层的平均显微硬度随着Si含量的升高而增加,CoCrFeNiSi2.0可达到566.5HV0.5.在3.5％NaCl溶液中,涂层的腐蚀电位随Si含量的增加而变大,CoCrFeNiSi2.0较CoCrFeNiSi0.0的腐蚀电位正移约160 mV,腐蚀电流密度从1.17×10-6 A/cm2减小到6.06×10-7 A/cm2,耐蚀性提高.当Si含量较低时,涂层表面出现连续大面积腐蚀痕迹,随着Si含量的增加,表面腐蚀以点蚀为主.结论 在CoCrFeNi系高熵合金涂层中添加Si元素,可以促进bcc相的生成,提高涂层的显微硬度,同时可以有效抑制合金涂层的腐蚀倾向,以及减缓合金涂层的腐蚀速率,提高耐蚀性能.     

HEPJet多元铝青铜合金涂层在3.5%的NaCl溶液中的腐蚀性能

采用超音速等离子喷涂(HEPJet)技术将新型多元铝青铜合金粉体喷涂在45号钢基体上。通过失重法、极化曲线法、X射线衍射分析(XRD)、扫描电镜(SEM)、能谱(EDS)和电子探针(EPMA-1600)等方法研究多元铝青铜合金涂层在3.5%的NaCl溶液中的腐蚀性能。结果表明,在3.5%的NaCl溶液中,多元铝青铜合金涂层具有良好的耐蚀性能,该涂层的腐蚀速率为0.0636mm/a。腐蚀后试样表面Al元素的含量明显下降,Cu的含量明显增加,可见,涂层发生的主要是脱铝腐蚀。     

NdFeB基体ZrN涂层的耐腐蚀性能

采用离子镀技术在NdFeB基体上沉积ZrN、ZrN/Zr多层和TiN/Ti多层涂层,考察了其耐腐蚀性能,分析了腐蚀过程.采用静态全浸腐蚀试验(20 % NaCl, 20 ℃)测定其失重曲线,扫描电子显微镜(SEM)分析腐蚀前、后的涂层表面形貌变化及腐蚀过程,用CHI600B系列电化学分析仪测试极化电位.试验发现:未镀层NdFeB基体在4 h后明显失重,随时间延长失重速率增加.施加涂层基体10 h后失重,随时间失重速率增加,但小于未镀层试样.NdFeB基体的自腐蚀电位约﹣1.037 V,腐蚀电流1.69×10-3 A/cm2;施加涂层后自腐蚀电位向正向移动0.131V(TiN/Ti)～0.258 V(ZrN),腐蚀电流10-5～10-6 A/cm2;ZrN/Zr涂层由7层增加到14层后,腐蚀电位提高0.037 V,腐蚀电流降低.结果说明:离子镀沉积ZrN系列涂层显著提高NdFeB耐腐蚀性能.增加ZrN/Zr周期能够提高耐蚀性能.腐蚀源首先在涂层表面缺陷与基体结合部位形成.一旦形成腐蚀源,NaCl晶体即在基体上结晶并生长,随着此过程进行,涂层逐步腐蚀.     

渗铝改性离子镀NiCrAIY涂层的高温热腐蚀行为

为了进一步改善离子镀NiCrAIY涂层的抗热腐蚀性能,采用粉末包埋法在离子镀NiCrAIY涂层表面上进行渗铝,研究了涂层渗铝前后在850℃含氯硫酸盐膜下的热腐蚀行为。结果表明：在25 % NaCl +75 010 Na2 S04熔盐中850℃热腐蚀40h时,未渗铝的NiCrAIY涂层生成的是外层以Cr2 03为主的氧化膜,渗铝后的NiCrAIY涂层仅生成一层Al2 03膜;未渗铝的NiCrAIY涂层在腐蚀50h后失去保护作用,而渗铝涂层在腐蚀lOOh后表面仍形成以Al2 03为主的保护膜。因此,渗铝处理可以明显提高原涂层的抗热腐蚀性能。     

热处理对不锈钢表面耐蚀性SiO_2-TiO_2-Al_2O_3-ZnO复合溶胶涂层性能的影响

以正硅酸乙酯、钛酸正丁酯、硝酸铝和醋酸锌为前驱体,无水乙酸为催化剂,采用溶胶-凝胶法在不锈钢表面制备了SiO_2-TiO_2-Al_2O_3-ZnO复合涂层,并对涂层进行了耐NaCl溶液浸泡腐蚀试验。利用扫描电镜对镀层在NaCl溶液腐蚀环境中的腐蚀形貌进行观察。对复合涂层进行了差热分析(DTA)、失重分析(TG),以此确定复合涂层的最佳烧结温度,还对涂层进行了X射线衍射分析,以此确定复合涂层的成分。结果表明,涂层的最佳烧结温度800℃。通过优化涂层的烧结温度等工艺,制备的溶胶-凝胶复合涂层提高了不锈钢表面的耐腐蚀能力。     

Scanning Kelvin probe analysis of the potential distribution under small drops of electrolyte

The scanning Kelvin probe has been used to map the potential distribution under small drops of NaCl placed on carbon steel, galvanized steel, stainless steel and an aluminum alloy. The concentration of NaCl has been varied and the effect of chromate as inhibitor has been evaluated. In the absence of chromate local anodes and cathodes were established in a short time. For carbon steel similar potential profiles were observed in NaCl and NaClO₄. However for stainless steel a much larger potential decrease in the center of the drop occurred in 0.5 N NaCl than in 0.5 N NaClO₄ and a marked effect of chloride concentration was observed. When dichromate was added to NaCl a very uniform potential distribution was found for stainless steel and Al 2024. The main driving force for development of local anodes arises from oxygen reduction in very thin films of electrolyte surrounding the NaCl drop.     

Morphological Development of Subscale Formation in Fe–Cr–(Ni) Alloys with Chloride and Sulfates Coating

Three types of stainless steel (430, 304, and 310) with a coating of NaCl, NaCl/AlCl₃, or NaCl/Al₂(SO₄)₃ are exposed at 750 and 850°C. Results show that NaCl has a major effect on corrosion and sulfur plays an important role in intergranular corrosion. After high-temperature exposure with a 100% NaCl coating, the morphologies of alloys 304 and 310 show typical uniform subscale attack the depths of attack increasing with temperature, while alloy 430 showed a planar attack. Alloy 310 has the highest chromium content and has the least metal loss. After high-temperature exposure with a NaCl/AlCl₃ coating, the corrosion morphologies and depths of attack are similar to those associated with an NaCl coating, but only voids are larger in the subscale. When coated with NaCl/Al₂(SO₄)₃, the alloys are attacked simultaneously by sulfur and chlorine at 750°C, resulting in a typical sulfur-attack intergranular corrosion. However, as the temperature increases to 850°C, the corrosion morphology changes to a uniform subscale attack.     

Comparison of accelerated SCC tests performed on the aluminium alloy 2014-T651

The stress corrosion cracking (SCC) behaviour of plates of the Al-Cu-Si-Mn-Mg alloy 2014-T651 was investigated in short transverse direction performing various accelerated tests. Corrosive media used were: aqueous 3.5% NaCl solution, an aqueous solution of 2% NaCl + 0.5% Na₂CrO₄ at pH = 3 (according to LN 65666), and substitute ocean water according to ASTM D1141. C-ring and tensile specimens were loaded under constant deformation, constant load and slow strain rate conditions. Alternate immersion tests in 3.5% NaCl solution clearly indicate the low SCC resistance of the alloy 2014-T651 in short transverse direction. Under continuous immersion conditions the acidified 2% NaCl solution containing chromate is an appropriate synthetic environment, while neutral 3.5% NaCl solution does not promote severe stress corrosion cracking. The SCC susceptibility of 2014-T651 is also observed in slow strain rate tests using substitute ocean water as well as acidified 2% NaCl solution inhibited by chromate. In 3.5% NaCl solution the evaluation of slow strain rate data is complicated by pre-exposure effects.     

Zum Spannungsrißkorrosionsverhalten rekristallisierter Bleche der AlLi-Legierung 8090-T81

On the stress corrosion cracking behaviour of recrystallized 8090-T81 Sheets The stress corrosion cracking behaviour of a recrystallized sheet of the Al-Li-Cu-Mg-Zr alloy 8090-T81 was studied performing accelerated tests under constant deformation, constant load, and slow strain rate conditions. The used electrolytes were an aqueous 3.5% NaCl solution, an aqueous solution of 2% NaCl + 0.5% Na₂CrO₄ at pH = 3, and synthetic seawater according to ASTM D1141. Alternately immersed in 3.5% NaCl solution according to ASTM G44 the investigated alloy was found to be susceptible to stress corrosion cracking was not promoted by continuous immersion in aerated 3.5% NaCl solution, 3.5% NaCl solution saturated with carbon dioxide, and in acid chromate inhibited 2% NaCl solution. Using the slow strain rate technique with continuously immersed flat tensile specimens stress corrosion cracking was only observed in synthetic seawater. Under specific environmental conditions hydrogen embrittlement can occur in the investigated material.     

Corrosion Behavior of GH4169 Alloy in NaCl Solution Spray Environment at 600°CEI北大核心CSCD

The corrosion behavior of engine materials of airplanes working in marine environments is accelerated by the synergistic effects of NaCl particles and water vapor at high temperatures. This work examined the corrosion behavior of GH4169 alloy with a NaCl solution spraying at 600 degrees C using an oxidation kinetics test and micro characterization technology in the aspects of corrosion kinetics, corrosion layer phase composition, and microstructure. The weight gain of the GH4169 alloy corroded in the NaCl solution spraying environment was much lower than that in solid NaCl + wet O-2 after 20 h corrosion at 600 degrees C. The corrosion products of the GH4169 alloy in the NaCl solution spray environment were less complex than those in the solid NaCl + wet O-2 environment, but they were denser. In addition, Cl was concentrated in the inner layer of the corrosion products and accelerated the corrosion of GH4169 alloy via an "active oxidation" mechanism at the initial stage. When NaCl deposition was increased, the corrosion mechanism of GH4169 alloy changed gradually to Cl-induced "active oxidation." The sensitivity of GH4169 alloy in the NaCl solution spray environment at 600 degrees C was analyzed. Overall, the sensitivity of elements in GH4169 alloy to chlorine activated corrosion was Ti > Al > Nb, Cr > Fe > Mo, Ni, whereas the sensitivity of the oxides was TiO2 > MoO2 > Cr2O3(Nb2O5) > Fe2O3 > Al2O3 > NiO.     

Synergistic Effect of NaCl and Water Vapor on the Corrosion of 1Cr-11Ni-2W-2Mo-V Steel at 500-700°C

The corrosion behavior of 1Cr-11Ni-2W-2Mo-Vsteel was studied in the presence of a NaCl deposit andwater vapor at 500-700°C. Results indicated thatcorrosion was not obvious without an NaCl deposit, while corrosion was accelerated remarkably by thesimultaneous presence of NaCl and water vapor at anytemperature. Optical microscopy (OM), X-ray diffraction(XRD), scanning electron microscopy (SEM), andelectron-probe microanalysis (EPMA) were used to analyze thecorrosion products. A mechanism of the synergisticeffect of water vapor and NaCl on corrosion of the steelis proposed.     

掺废渣混凝土抗冻融性能的超声检测

用超声波法检测了掺废渣混凝土在水溶液、3．5％氯化钠溶液以及3．5％氯化钠与5．0％硫酸钠复合溶液中冻融前后的声速变化。结果表明，生态混凝土在氯化钠溶液中冻融循环的质量损失比水和复合溶液中冻融循环的质量损失大，氯化钠溶液对生态混凝土冻融循环产生的剥蚀是不能忽略的；声速变化比质量损失变化明显，说明超声波法是一种检测混凝土冻融损伤的简单可靠的方法。     

Corrosion behaviour of AZ31B magnesium alloy in NaCl solutions saturated with CO2

Corrosion behaviour of AZ31B magnesium alloy in different concentrations of NaCl solution saturated with CO₂ was studied by electrochemical techniques, Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray. The corrosion rate increases with increasing NaCl concentration both in the presence and absence of CO₂. The corrosion rate in NaCl solution saturated with CO₂ is bigger than that in single NaCl solution. The inhibitive effect of CO₂ is also observed with immersion time increased in NaCl solution saturated with CO₂, showing that CO₂ reduces the average corrosion rate due to the formation of insoluble products.     

Hierarchical open cellular porous TiAl manufactured by space holder process

Open-cellular porous TiAl was synthesized by a chemical reaction between titanium and aluminum with a space holder powder (NaCl). Self-propagation of the combustion reaction occurred throughout the specimen when the NaCl addition was below 40vol%, while such a propagating behavior was not observed with higher NaCl additions. TiAl was synthesized after the reaction. Pores were formed in places where the NaCl particles were present. This process shows the hierarchical structure with a bimodal size distribution.     

Open circuit potentials of metallic chromium and austenitic 304 stainless steel in aqueous sulphuric acid solution and the influence of chloride ions on them

Open circuit potential measurements and cyclic voltammetry of chromium and 304 stainless steel in deaerated aqueous H₂SO₄ solution of pH 1, without and containing NaCl in the concentration range 1–4 M revealed that chromium exhibits two stable open circuit potentials both having the character of a Wagner–Traud corrosion potential. One, E_corr.1, was established on the passive surface formed by previously exposing Cr to air or by potentiostatic passivation in a controlled manner, and the second one, E_corr.2, at the bare Cr surface obtained by prolonged cathodic activation. There was a small difference in the E_corr.1 values depending on the properties of the passive layer. Addition of NaCl accelerates to some extent, the hydrogen evolution reaction on the passive surface, while the same reaction on the bare surface was somewhat inhibited by NaCl. On the other hand, presence of NaCl accelerates the anodic reaction on the bare surface, and it activates the dissolution of the passive layer so that the passivation currents increase with addition of NaCl. This effect is so large that at concentrations of NaCl larger than 3 M, the destruction of the passive layer was so fast that in a matter of seconds the Cr is activated, and the only stable corrosion potential observed was E_corr.2. No pitting of Cr in the presence of NaCl was observed up to the transpassive potentials. 304 stainless steel could not be activated in sulphuric acid solution, and its open circuit potential, unlike the corrosion potential of the 400 types of stainless steel, was established by the hydrogen evolution reaction on the passive steel surface. The small anodic peak often observed on 304 stainless steel if the metal had been cathodically pre-treated is a pseudo-peak due to the anodic oxidation of hydrogen absorbed inside the metal. This finding should be elaborated more in recommendations (e.g. ASTM standards) for the application of electrochemical corrosion rate measurement to 304 stainless steel corrosion. Addition of NaCl activates the anodic dissolution of steel with the current of the passivation peak being proportional to the NaCl concentration. Unlike chromium, austenitic 304 stainless steel achieves only one corrosion potential in sulphuric acid, both in the presence and absence of NaCl, with the value of ca. −0.200 to −0.350 V (SCE) in the absence and −0.450 V (SCE) in the presence of NaCl, when steel corrodes as the active metal.