Ni基合金在900 ℃75%Na2SO4+25%NaCl盐膜下的热腐蚀

研究了纯Ni、Ni-10Cr和Ni-10Cr-5Al合金在900 ℃空气中涂敷Na2SO4+25%NaCl盐膜时的热腐蚀行为。结果表明,Ni-10Cr合金的腐蚀动力学曲线近似服从抛物线规律,而纯Ni和Ni-10Cr-5Al合金的腐蚀动力学曲线分段服从抛物线规律。Ni-10Cr的腐蚀增重最小,抗热腐蚀性能最好,Ni-10Cr-5Al次之,纯Ni的腐蚀增重最大。Ni-10Cr-5Al合金热腐蚀24 h后氧化产物分为3层,外层氧化产物主要是NiO,中间层氧化产物为Cr2O3和Al2O3,最内层有少量Cr2S3和Al2S3。Ni-10Cr合金热腐蚀24 h后氧化膜分为3层,外层氧化产物是NiO,中间层是不连续的Cr2O3,内腐蚀区有少量Cr2S3。由于熔盐中NaCl的存在,Ni-10Cr-5Al和Ni-10Cr合金的腐蚀产物会变得疏松多孔。     

一种镍基合金在850℃和950℃熔融NaCl中的热腐蚀行为

采用X射线(XRD)、扫描电镜(SEM/EDAX)等手段,研究了一种镍基合金在850℃和950℃熔融Na Cl的热腐蚀行为。结果表明:腐蚀期间,合金发生了高温氧化和热腐蚀行为;合金表面腐蚀产物分为3层,外层氧化物由Al2O3、Al Ta O4和Ni Cr2O4组成,中间层氧化物为Cr Ta O4、Ni WO4和WO3,而内层形成Al2O3内氧化物;且随腐蚀温度提高,合金表面的腐蚀层厚度及Al2O3内氧化层深度增加。     

Ni基合金在900℃75%Na_2SO_4+25%NaCl盐膜下的热腐蚀（英文）

研究了纯Ni、Ni-10Cr和Ni-10Cr-5Al合金在900℃空气中涂敷Na2SO4+25%NaCl盐膜时的热腐蚀行为。结果表明,Ni-10Cr合金的腐蚀动力学曲线近似服从抛物线规律,而纯Ni和Ni-10Cr-5Al合金的腐蚀动力学曲线分段服从抛物线规律。Ni-10Cr的腐蚀增重最小,抗热腐蚀性能最好,Ni-10Cr-5Al次之,纯Ni的腐蚀增重最大。Ni-10Cr-5Al合金热腐蚀24 h后氧化产物分为3层,外层氧化产物主要是NiO,中间层氧化产物为Cr2O3和Al2O3,最内层有少量Cr2S3和Al2S3。Ni-10Cr合金热腐蚀24 h后氧化膜分为3层,外层氧化产物是NiO,中间层是不连续的Cr2O3,内腐蚀区有少量Cr2S3。由于熔盐中NaCl的存在,Ni-10Cr-5Al和Ni-10Cr合金的腐蚀产物会变得疏松多孔。     

三种β-NiAl相材料的短期热腐蚀行为比较研究

在Ni-30Al(mass%,下同)和Ni-20Cr-10Al铸态合金上进行粉末包埋渗铝,分别得到纯β-NiAl相涂层和β-(Ni,Cr)Al相涂层.在这两种渗铝试样和铸态Ni-20Cr-13Al合金(含β-NiAl、γ′-Ni3Al、α-Cr相)上涂覆了硫酸钠薄膜,进行900℃热腐蚀测试.经过10小时热腐蚀测试后,三种试样表面均生成Al2O3膜.腐蚀动力学分析表明,Cr对提高材料的抗热腐蚀性能是有益的;Ni-20Cr-10Al渗铝涂层试样的增重最低,仅为铸态Ni-20Cr-13Al合金试样增重的80%左右,Ni-30Al渗铝涂层试样增重的50%左右.     

一种定向凝固Co基合金的热腐蚀行为

利用箱式电阻炉、SEM等手段,研究了一种定向凝固Co基合金在不同介质中的热腐蚀行为及机理。研究结果表明:合金在Na2SO4中的热腐蚀最为严重,在75%Na2SO4+25%NaCl中的热腐蚀程度最轻。合金在Na2SO4中的热腐蚀过程中主要发生了酸性熔融反应,形成了Al2(SO4)3,Cr2Ni3,Cr4Ni15W和Al4CrNi15等腐蚀产物,而在NaCl中的热腐蚀主要发生了活性氧化反应,合金在75%Na2SO4+25%NaCl中热腐蚀时,部分酸性熔融反应和活性氧化反应受到抑制,主要形成了一系列的Ni-S化合物。     

Ni-Cr-Al-Fe基合金粉末的高温抗氧化行为

研究Ni-Cr-Al-Fe基合金粉末在600 ℃空气中的高温抗氧化性能,分析铝含量和预氧化处理对合金粉末高温抗氧化行为的影响.利用水雾化法制备不同铝含量的Ni-Cr-Al-Fe基合金粉末,利用静态质量增加法研究不同铝含量合金粉末的氧化动力学,分别利用FE-SEM(EDS)和XRD观察分析不同合金粉末氧化膜的形貌及成分,结合氧化动力学及氧化膜的组成进一步分析不同合金粉末的高温氧化机理.结果表明:Ni-Cr-Al-Fe基合金粉末在600 ℃时的氧化质量增加遵循抛物线规律,铝含量的增加及预氧化处理均可提高合金粉末的抗氧化能力;铝含量的增加使氧化膜的组成由Cr2O3和Al2O3的混合结构转变为单一的Al2O3氧化膜结构,这有利于提高合金粉末的抗氧化性能;预氧化处理所形成的氧化膜有效地抑制Ni-Cr-Al-Fe基合金粉末的进一步氧化.     

电弧离子镀NiCrAlY涂层900℃的热腐蚀行为

采用电弧离子镀技术在镍基单晶合金上沉积Ni28Cr11Al0.5Y涂层,并研究了镍基单晶合金及有Ni28Cr11Al0.5Y涂层镍基单晶合金在900℃的75%Na2SO4+25%K2SO4熔盐中的热腐蚀行为。结果表明,镍基单晶合金遭受了破坏性的热腐蚀,出现了严重的内硫化和内氧化;而由于Ni28Cr11Al0.5Y涂层在熔盐中生成连续的Al2O3氧化膜,阻止了熔盐对单晶合金的腐蚀,有涂层镍基单晶合金表现出优良的抗热腐蚀性能。     

Al-Si涂层在900℃硫酸盐中的热腐蚀行为

采用料浆法在Ni基高温合金上制备了Al-Si扩散涂层，研究了表面涂覆75mass%Na2SO4+K2SO4盐膜的基体合金和Al-Si涂层在900℃空气中的热腐蚀行为.结果表明，铸态合金遭受了灾难性的热腐蚀，合金出现严重的内硫化和内氧化，而Al-Si涂层由于表面生成致密的、保护性Al2O3膜，以及涂层中Cr元素和一些富Si相的有益作用而表现出优异的抗热腐蚀性能.       

Ni-16Cr-xAl合金在600℃Na2SO4-NaCl混合盐中的热腐蚀行为（英文）

研究Ni-16Cr-xAl(x=4.5%,6.8%,9.0%)合金在600°CNa2SO4-NaCl混合盐中的热腐蚀行为,分析预氧化及铝含量对合金抗热腐蚀行为的影响。结果表明,随着铝含量由4.5%增加到9.0%(质量分数),Ni-16Cr-xAl(x=4.5%,6.8%,9.0%)合金在Na2SO4-NaCl混合盐中的抗热腐蚀性能提高。因为β-NiAl相的存在能修复热腐蚀中被破坏的Al2O3膜,所以Ni-16Cr-9.0Al合金表现出最优异的抗热腐蚀性能。在预氧化后的样品表面形成了一层具有保护性的氧化膜,其抗热腐蚀性能优于原始态样品的。     

电弧离子镀NiCrAlY涂层对镍基单晶合金热腐蚀行为的影响

采用电弧离子镀技术在镍基单晶合金表面沉积Ni28Cr11Al0.5Y涂层,研究镍基单晶合金及其Ni28Cr11Al0.5Y涂层在900℃的75%Na2SO4+25%K2SO4(质量分数)熔盐中的热腐蚀行为。结果表明:镍基单晶合金受到了严重的热腐蚀,镍基单晶合金内部出现了严重的内硫化和内氧化现象,且内硫化物区域和内氧化物区域出现明显分层结构,与外腐蚀层相邻的区域为内氧化区域,远离外腐蚀层的基体内部形成内硫化区域;而Ni28Cr11Al0.5Y涂层在热腐蚀过程中,表面生成连续的Al2O3氧化膜,且随腐蚀时间延长,Al2O3氧化膜的厚度增大,表现出优良的抗热腐蚀性能。     

The Sulfidation/Oxidation Resistance of Two Ni-Cr-Al-Y Alloys at 700℃

The high temperature corrosion resistance of Ni-25.9Cr-13.5Al-1.2Y-0.6Si and Ni-10.2Co-12.4Cr-16.0Al-0.5Y-0.2Hf alloys was assessed in sulfidation/oxidation environments.In the environment with a sulfur partial pressure of 1Pa. and an oxygen partial pressure of 10^-19Pα,both these alloys exhibited three distinct stages in the weight gain-time curve when tested at 700℃.In the initial stage, selective sulfidation of Cr suppressed the formation of the other metal sulfides,resulting in lower weight gains.In the transient stage, breakdown and cracking of Cr sulfides and insufficient concentration of Cr at the outer zone led to the rapid formation of Ni sulfides and a rapid increase in weight.In the steady-state stage, corrosion was controlled by the diffusion of anions and/or cations, which led to a parabolic rate law.     

THE SULFIDATION/OXIDATION RESISTANCE OF TWO Ni-Cr-Al-Y ALLOYS AT 700℃

The high temperature corrosion resistance of Ni-25.gCr-13.5Al-1.2Y-0.6Si and Ni-10.2Co-12.4 Cr-16.0A l-0.5 Y-0.2Hf alloys was assessed in sulfidation/oxidation environments.In the environment with a sulfur partial pressure of 1Pa.and an oxygen partial pressure of 10-19Pa,both these alloys exhibited three distinct stages in the weight gain-time curve when tested at 700℃.In the initial stage,selective sulfidation of Cr suppressed the formation of the other metal sulfides,resulting in lower weight gains.In the transient stage,breakdown and cracking of Cr sulfides and insufficient concentration of Cr at the outer zone led to the rapid formation of Ni sulfides and a rapid increase in weight.In the steady-state stage,corrosion was controlled by the diffusion of anions and/or cations,which led to a parabolic rate law.     

Microstructure and Electrochemical Corrosion Behavior of Fe-Cr System Alloys as Substitutes for Ni-Based Brazing Filler Metal

Two new Fe-Cr system alloys,Fe-20Cr-43Ni-10P(mass%)and Fe-20Cr-20Ni-8P-5Si-2Mo(mass%),have been developed as substitutes for the expensive Ni-based brazing filler metal used in brazing exhaust gas recirculation coolers.The microstructures and melting properties of the alloys were analyzed by electron probe X-ray microanalyzer and differential scanning calorimetry.The electrochemical characteristics of the alloys were investigated by potentiodynamic polarization testing in an electrolyte solution made in accordance with the standards of the Automobile Manufacturers Association of Germany.Furthermore,the corrosion behaviors of the alloys were investigated by constant-potential polarization testing and surface characterization.It is found that both alloys are composed of solid-solution phases and phosphide phases.The solid-solution phases serve as the anode,and the phosphide phases serve as the cathode in the corrosion reaction for both alloys.Fe-20Cr-43Ni-10 P exhibits galvanic corrosion on the entire surface.In contrast,Fe-20Cr-20Ni-8P-5Si-2Mo is attacked at a few localized areas so that the cavities form on the surface.The corrosion potential(E_(corr)) is lower than that of Ni-29Cr-6P-4Si(mass%)for both alloys.This means that the Fe-Cr system alloys are more easily corroded than Ni-29Cr-6P-4Si.The corrosion rate and corrosion resistance cannot be investigated by the corrosion current density(i_(corr)) and polarization resistance(R_p),respectively,because of localized corrosion of the two alloys.     

Effect of yttrium on the sulfidation behavior of Ni-Cr-Al alloys at 700°C

The sulfidation of Ni-10Cr-5Al, Ni-20Cr-5Al, and Ni-50Cr-5Al, and of the same alloys containing 1% Y, was studied in 0.1 atm sulfur vapor at 700°C. The sulfidation process followed linear kinetics for all the alloys except Ni-50Cr-5Al-1Y, and possibly Ni-50Cr-5Al, which followed the parabolic law. The reaction rates decreased with increasing chromium content in alloys without yttrium, and the addition of yttrium reduced the rates by at least a factor of two for the alloys containing 10 and 20% Cr and by an order of magnitude for Ni-50Cr-5Al. Alloys containing 10 and 20% Cr (with and without yttrium) formed duplex scales consisting of an outer layer of NiS_1.03 and an inner lamellar layer of a very fine mixture of Cr₂S₃ and A1₂O₃ in a matrix of NiS_1.03. The two alloys containing 50% Cr formed only a compact layer of Cr₂S₃, which was brittle and spalled during cooling. The lamellae in the duplex scales were parallel to the specimen surface and bent around corners. The lamellae were thicker than those on Ni-Al binary alloys. The lamellae were also thicker in scales on the 20% Cr alloy than on the 10% Cr alloy. The presence of yttrium refined the lamellae and increased the lamellae density near the scale/metal interface in the 10% alloy, but in the 20% Cr alloy the lammellae were thicker and more closely spaced. Platinum markers were found in the inner portion of the exterior NiS_1.03 layer close to the lamellar zone. A counter-current diffusion mechanism is proposed involving outward cation diffusion and inward sulfur diffusion, although diffusion was not rate controlling for alloys containing 10 and 20% Cr. Auger analysis of scales formed on Ni-50Cr-1Y showed an even distribution of yttrium throughout the layer of Cr₂S₃, suggesting that some yttrium dissolved in the sulfide. The reduced sulfidation rate of samples containing yttrium is explained by the possible dissolution of yttrium as a donor. The presence of Y⁴⁺ would then decrease the concentration of interstitial chromium ions in the N-type layer of Cr₂S₃, which would decrease the reaction rate.     

A TEM study of the oxide scale development in Ni-Cr-Al alloys

In the present study the isothermal oxidation behaviours of Ni-10Cr-5Al, Ni-20Cr-5Al and Ni-30Cr-5Al alloys were investigated. The alloys were oxidised in air for 50 h at 1000 °C. Analytical transmission electron microscopy was used to characterize the morphology, structure and composition of the oxide scale. The oxide formed adjacent to the alloy was α-Al₂O₃ such that the higher was the Cr content of the alloy the easier was its formation. The Ni-30Cr-5Al alloy formed a complete layer of α-Al₂O₃ in the initial stages of oxidation through ‘oxygen gettering’ by Cr. A decrease in scale thickness and an increase in scale adherence were observed with an increase in Cr content from 10 to 30 wt.%.     

几种含铌镍基合金的热腐蚀研究

用硫酸钠沉积法研究了四种镍基合金-Ni-16Cr,Ni-16Cr-2Nb,IN738和537合金-在900～1000℃之间的热腐蚀行为。用热天平测量了热腐蚀动力学曲线,用金相、SEM、电子探针、X 射线衍射和~(3δ)S 示踪法观察和分析了腐蚀产物。研究发现,Ni-16Cr-2Nb 合金中的铌富集在表面氧化膜内,形成 NaNbO_3而降低熔盐中的 O~(2-)浓度,抑制 Cr_2O_3膜与熔盐的反应;但在复杂成份的合金中。铌的上述作用可能促进氧化膜的酸性熔融。鈪同时能促进硫在 Ni-16Cr-2Nb 变形合金晶界上的连续分布,加速内硫化过程。     

Effects of mode-I stresses on the oxidation and failure mechanisms of Ni-20Cr and Ni-15Cr-8Fe alloys in sulfur dioxide

Two alloys, Ni-20Cr and Ni-15Cr-8Fe, as wire specimens, were exposed to sulfur dioxide between 325 and 800°C, with applied external stresses (mode I). Their mechanical properties have been investigated, and the variation of their radius has been precised by conductivity measurements. For the Ni-20Cr alloy, below 550°C, the failure process combines cracking and corrosion: Cr₂S₃ crystals formed at the tip of the cracks facilitate their propagation. Above 550°C, no barrier effect is observed, and intergranular corrosion takes place. For the Ni-15Cr-8Fe alloy, mode-I stresses bolster intergranular corrosion.