Re对Ni_3Al-Mo基合金的1150℃氧化性能的影响(英文)

研究3种Ni3Al-Mo基合金在1150℃时的静态氧化行为。采用XRD、SEM和EPMA对氧化后试样的表面、截面形貌以及元素在氧化膜的分布进行研究。结果表明:氧化膜主要分为3层,最外层为NiO层,中间层由NiO、NiAl2O4及少量NiMoO4组成,最内层主要由富Al的NiAl2O4、Al2O3组成。Re元素主要分布在中间层,在氧化过程中起到"扩散障"作用,降低Al、Mo元素向外扩散的速率,促使在内层形成富铝氧化膜层以降低氧化速率,提高合金的抗氧化能力。     

多弧离子镀Cr涂层对γ-TiAl合金高温氧化性能的影响

采用多弧离子镀技术在γ-TiAl合金表面制备Cr涂层,用SEM/EDS和XRD等手段研究了该涂层对γ-TiAl合金在高温下氧化性能的影响。结果表明,涂层在高温下可形成保护性氧化膜,氧化膜主要分为内外两层,其中外层氧化膜在650℃下主要为Cr2O3,在750℃下为TiO2,在950℃为Al2O3,内层氧化膜均为Ti-Al-Cr的混合氧化膜,Ti-Al-Cr的互扩散层可有效阻止氧向基体扩散,显著提高了γ-TiAl的抗高温氧化能力。     

奥氏体不锈钢热浸镀铝层的抗氧化特性

为进一步提高奥氏体不锈钢0Cr18Ni9Ti的高温使用性能,对该钢进行了热浸镀铝处理和抗高温氧化性能的试验.试验结果表明:经热浸镀铝处理后,奥氏体不锈钢0Cr18Ni9Ti的抗高温氧化性能明显得到改善,其热浸镀铝层的抗高温氧化行为符合抛物线规律.1 000℃抗氧化试验表明:在高温氧化过程中,表层Al2O3氧化膜及扩散层中的金属间化合物FeAl相和β-NiAl相起到抗氧化作用.     

扩散退火对热浸镀铝层组织与抗高温氧化性的影响

借助X射线衍射仪(XRD)和环境扫描电镜(SEM/EDAX)对45钢热浸镀铝镀层及其扩散退火处理后的微观组织进行了研究.结果表明,热浸镀铝镀层由铝层和扩散层组成,外层铝层中主要成分为Al和FeAl3,内层扩散层中则主要为Fe2Al5和FeAl3等.扩散退火处理后镀层亦由内外两层组成,外层成分主要为Fe2Al5,内层则主要为FeAl.通过静态氧化增重法研究了45钢热浸镀铝扩散退火后的抗高温氧化性能,结果表明其抗高温氧化性好于未经扩散处理试样,显著优于45钢基体.     

1Cr18Ni9Ti热浸镀铝扩散层的的抗氧化性

通过高温氧化实验,测定出1Cr18Ni9Ti热浸镀铝前后的氧化增重,分析了扩散层的微观结构和表面氧化产物的物相组成。结果表明：1Cr18Ni9Ti热浸镀铝后的抗氧化温度可达1100℃,扩散层中Fe2Al5退化成FeAl后β-NiAl将发挥抗氧化使用,α-Al2O3相的形成是使材料抗高温氧化性提高的主要原因。     

含铼镍基单晶高温合金在900℃的循环氧化行为

采用X射线衍射(XRD),扫描电镜(SEM)及能谱(EDAX)等手段,研究了一种含铼镍基单晶高温合金在900℃的高温循环氧化行为.结果表明,在氧化初期合金的氧化质量增加较快,随着氧化时间延长氧化增重和失重交替进行,氧化动力学曲线不符合抛物线规律.高温氧化期间,合金发生明显的外氧化和内氧化,900℃氧化形成的氧化膜由三层组成,外层氧化膜由NiO、A12O3和(Ni,Co)Cr2O4组成;中间层为平直的CrTaO4及AlTaO4层;内层氧化物为Al2O3.在合金的氧化期间,分布在中间层的富Re、Ta和W相可抑制基体中Al向外扩散,并抑制氧化膜的生长,使氧化速度降低.     

扩散处理热浸镀铝钢高温抗氧化行为的研究

对经不同扩散工艺处理的热浸镀铝层高温抗氧化性进行了研究,通过SEM、TEM、XRD分析了经扩散处理后,热浸镀铝层高温氧化过程中组织结构的变化情况,分析了热浸镀铝层高温抗氧化性能和微观结构的关系,确定了提高热浸镀铝层高温抗氧化性的适宜扩散温度.结果表明,经750℃扩散处理,热浸镀铝层结构由较厚的外表层(Fe2Al5+FeAl2)及内层(FeAl+条状FeAl2)组成,条状FeAl2的形成为氧提供了扩散通道,其抗氧化性较差;经950℃扩散处理,镀层外表层变薄,外表层转为单一FeAl2、内层为FeAl,并出现早期内氧化裂纹,其抗氧化性较差:当扩散处理温度为850℃时,镀层外表层变薄,结构转为FeAl2+少量Fe2Al5,而内层增厚,其结构为FeAl+球状FeAl2,而内层FeAl2球化,增强了氧由内层向基体扩散的阻碍作用,使氧只能逐层形成Al2O3+Fe2O3的氧化膜,提高了镀层的高温抗氧化性.     

扩散处理热浸镀铝钢高温抗氧化行为的研究

对经不同扩散工艺处理的热浸镀铝层高温抗氧化性进行了研究,通过SEM、TEM、XRD分析了经扩散处理后,热浸镀铝层高温氧化过程中组织结构的变化情况,分析了热浸镀铝层高温抗氧化性能和微观结构的关系,确定了提高热浸镀铝层高温抗氧化性的适宜扩散温度.结果表明,经750℃扩散处理,热浸镀铝层结构由较厚的外表层(Fe2Al5+FeAl2)及内层(FeAl+条状FeAl2)组成,条状FeAl2的形成为氧提供了扩散通道,其抗氧化性较差;经950℃扩散处理,镀层外表层变薄,外表层转为单一FeAl2、内层为FeAl,并出现早期内氧化裂纹,其抗氧化性较差当扩散处理温度为850℃时,镀层外表层变薄,结构转为FeAl2+少量Fe2Al5,而内层增厚,其结构为FeAl+球状FeAl2,而内层FeAl2球化,增强了氧由内层向基体扩散的阻碍作用,使氧只能逐层形成Al2O3+Fe2O3的氧化膜,提高了镀层的高温抗氧化性.     

Al和C0对K4169合金950℃高温氧化行为的影响

利用热重分析法、X射线衍射、扫描电镜和能谱分析研究了Al和Co含量对K4169高温合金950℃高温氧化行为的影响,结果表明:合金氧化动力学符合抛物线规律;添加Al和Co的合金氧化产物颗粒比原始成分合金的细小;Al含量的增加增强了合金的高温抗氧化能力,而Co含量的增加降低了合金的高温抗氧化性能.当Al含量为1.45 wt%、Co含量为0.3 wt%时,合金的高温抗氧化性能最好,而原始成分合金的高温抗氧化性能最差.不同Al、Co含量K4169合金氧化膜都分为3层:外层主要是疏松的Cr2O3和TiO2的混合层,还含有少量的NiO和NiCr2O4尖晶石相;中间层是Cr2O3保护层;内氧化物层是Al2O3.     

Al和Co对K4169合金950℃高温氧化行为的影响

利用热重分析法、X射线衍射、扫描电镜和能谱分析研究了Al和Co含量对K4169高温合金950℃高温氧化行为的影响,结果表明:合金氧化动力学符合抛物线规律;添加Al和Co的合金氧化产物颗粒比原始成分合金的细小;Al含量的增加增强了合金的高温抗氧化能力,而Co含量的增加降低了合金的高温抗氧化性能。当Al含量为1.45 wt%、Co含量为0.3 wt%时,合金的高温抗氧化性能最好,而原始成分合金的高温抗氧化性能最差。不同Al、Co含量K4169合金氧化膜都分为3层:外层主要是疏松的Cr2O3和TiO2的混合层,还含有少量的NiO和NiCr2O4尖晶石相;中间层是Cr2O3保护层;内氧化物层是Al2O3。     

铸造镍基合金K444在900℃空气中的长期氧化行为

用热重法研究镍基高温合金K444在900℃下氧化1000 h的动力学。结果表明,K444合金氧化动力学遵从抛物线规律,以x射线衍射、扫描电镜和能谱分析及电子探针成分分析测定氧化膜的组成,结果表明氧化膜由多层组成,外层为TiO₂,内层以Cr₂O₃为主还包括内氧化层和贫Υ′层。观察到沿晶界偏聚的碳化物氧化,提出了氧化饥制。     

Oxidation characteristics of Ti-25Al-10Nb-3V-1Mo

Static oxidation kinetics of Ti-25Al-10Nb-3V-1Mo (atomic percent) were investigated in air over the temperature range of 650–1000°C using thermogravimetric analysis. The oxidation kinetics were complex at all exposure temperatures and displayed up to two distinct stages of parabolic oxidation. Breakaway oxidation occurred after long exposure times at high temperatures. Oxidation products were determined using x-ray diffraction techniques, electron microprobe analysis, and energy dispersive x-ray analysis. Oxide scale morphology was examined using scanning electron microscopy of the surfaces and cross-sections of oxidation specimens. The oxides during the parabolic stages were compact and multilayered, consisting primarily of TiO₂ doped with Nb, a top layer of Al₂O₃ and a thin bottom layer of TiN. The transition between the first and second parabolic stage is linked to the formation of a TiAl layer at the oxide-metal interface. Porosity also formed in the TiO₂ layer during the second stage, causing degradation of the oxide and breakaway oxidation.     

Effects of aluminum on the oxidation of 25Cr-35Ni cast steels

The oxidation kinetics and morphological development during reaction of two cast austenitic steels at 1000°C in pure dry oxygen at 20 kPa are reported. Both steels contained approximately 25 wt.% Cr and 35 wt.% Ni and, in addition, one steel contained 3.3 wt. %. Both steels oxidized to form external scales consisting mainly of Cr₂O₃ with a thin outer layer of manganese rich spinel. Scale growth kinetics were parabolic, and somewhat faster rates were observed for the aluminum bearing steel. In both steels, deep internal oxidation occurred at the site of primary (interdendritic) carbides. The kinetics of this process were parabolic, and rate control was attributed to oxygen diffusion along the interface between internal oxide and matrix metal. In the aluminum-free steel, interdendritic carbides were converted to chromium rich oxide, but when aluminum was present, a sheath of aluminum rich oxide formed around the carbides. In this latter case, the rate of interdendritic penetration was somewhat slower. The aluminum bearing steel also formed large numbers of rod-shaped Al₂O₃ precipitates within the austenitic dendrites. Deepening of the Al₂O₃ precipitate zone also proceeded according to parabolic kinetics at a rate consistent with rate control by diffusion of oxygen along the oxide-alloy interfaces.     

等离子喷涂NiCrCoAlY涂层氧化控制研究

利用等离子喷涂技术制备了NiCrCoAlY粒子和涂层,研究了等离子喷涂过程中NiCrCoAlY粒子的氧化行为以及屏蔽气体对NiCrCoAlY涂层抗高温氧化性能的影响。结果表明,粒子在飞行过程中存在对流氧化和扩散氧化两种氧化机制,对NiCrCoAlY粒子来说,在距喷嘴55 mm以内的射流中心处以对流氧化为主,在距离喷嘴55 mm以外将以扩散氧化为主;除飞行中的氧化外,粒子在喷涂过程中还发生形成涂层后的氧化,NiCrCoAlY粒子以飞行中的氧化为主;添加屏蔽气体能减少喷涂过程中涂层的氧化,提高涂层的抗高温氧化性能     

纯钛TIG焊接接头的高温氧化行为

对纯钛氩弧焊焊接接头在550 ℃下氧化不同时间（2,4,6,8 h）以及在不同温度（650,750,850,950 ℃）下氧化4 h的氧化动力学、氧化形态和氧化产物进行了研究。结果表明,在550 ℃下,氧化时间对焊接接头氧化行为的影响有限,而氧化温度对纯钛焊接接头的氧化行为有显著影响,且温度越高,氧化越严重。在低温下,纯钛焊接接头的氧化动力学接近准线性定律,随着温度升高,氧化速率呈指数增长。此外,焊接接头表面产生的氧化产物是具有锐钛矿和金红石结构的TiO₂,温度对TiO₂的类型没有明显影响。纯钛焊接接头的氧化过程可描述为：氧气在表面被吸收;氧化物优先在缺陷区形核;氧化物横向生长、增厚。在较高温度下,氧化膜中出现裂纹或空隙,成为O原子传输通道,导致O和Ti原子的高扩散速率和氧化速率。     

The Effect of Crystallographic Orientation on the Oxidation Behavior of a Single-Crystal Nickel-Base Superalloy

The oxidation kinetics of DD100 nickel-base single-crystal alloy, with (221) and (100) surface orientations were tested in this study by thermogravimetry. A pronounced anisotropy in both the cyclic and isothermal oxidation resistance of DD100 alloy was observed. The (221) crystallographic surface of DD100 had a slower oxidation rate than the (100) surface when isothermally exposed to stationary air at 950°C, whereas the opposite results were obtained at 1050°C. When cyclically oxidized at 1100°C, the weight loss of samples with (221) surfaces was significantly greater than that of (100) surfaces, so that the cyclic-oxidation anisotropy was more remarkable at 1100°C than at 950°C. The different spatial alignment of the / interface is thought to be responsible for the anisotropic oxidation behavior of the nickel-base single crystal alloy.     

High temperature oxidation of metals under time-dependent gas pressure

A theoretical study on the high-temperature oxidation of thick oxide films grown under a time-dependent gas partial pressure is reported. The diffusion across the film is assumed to be the rate-limiting step of the overall reaction, and Wagner's hypotheses were used as the starting point for our reasoning. A general formulation for the oxidation under no time constant gas pressure, in terms of a time-dependent answer function is given. The effect of an external electric field on the reaction rate is also reported when a constant current density,J, is applied to the oxide scale. If the oxide is a good electronic conductor atJ=0 andt , we found that the reaction rate assumes formally the well-known Wagner's expression of the rate constant but with a gas partial pressure at oxide/gas interface which is a time function. If the oxide is a good ionic or electronic conductor, the effect due to an external electric field,J 0, on the reaction rate is the same as predicted by the Wagner's theory.     

Fe-Y合金在800℃空气中的氧化行为

研究了Fe-5Y和Fe-10Y合金在800℃空气中的氧化行为。结果表明：二元Fe-Y合金氧化动力学曲线不规则,此温度下Fe-10Y合金的氧化速率高于Fe-5Y合金的氧化速率。Fe-5Y合金及Fe-10Y合金形成了相似的氧化膜结构,且它们都发生了内氧化现象。同时合金未形成单一的Y₂O₃层,这归结于Y在Fe中非常低的溶解度及合金中两相共存而阻碍了Y通过合金向外扩散。     

V/Nb对Ti-45Al-9(V, Nb, Y)合金抗氧化性能的影响

βγ-TiAl合金具有良好的高温变形能力,为TiAl合金的发展开辟了新的途径。成功制备了不同x=V/Nb(x=1,1.5,2,3.5)的βγ-TiAlTi-45Al-9(V,Nb,Y)合金,研究了上述合金在800℃静止空气中的氧化行为。结果表明:当x=1时,Ti-45Al-9(V,Nb,Y)合金中形成条带状、连续致密的Al2O3氧化层,显著提高了合金的抗氧化能力。随着x=V/Nb的增加,Al2O3氧化层厚度变薄,合金的抗氧化能力下降。     

Oxidation resistance of eight heat-resistant alloys at 870°, 980°, 1095°, and 1150°C

Oxidation testing of heat-resistant alloys is described. The testing procedure utilized weight-gain measurements using one specimen, which was withdrawn and weighed at intervals of 1 week, for 10–18 weeks. The specimen was placed in a porcelain cup during exposure and covered upon cooling to retain spalled oxide. Weight gain was used to determine the kinetics of oxidation and was extrapolated to 3000 hr. The specimen was withdrawn at the end of the exposure, weighed, cathodically descaled, and reweighed. The ratio of oxygen ions to metal ions was determined for each alloy and test temperature. This ratio approaches the stoichemetric ratio for Fe₃O₄ or Cr₂O₃. The ratio for each test is used to convert weight gain to weight loss. The amount of adherent oxide was determined as well as the total amount of oxide, leading to an expression for oxide adherency. The oxidation resistance of Fe-Cr-Ni alloys increased with increasing Cr and Ni, with Cr being the most critical element. Additions of Si, Al, or Ce were shown to extend the usefulness of Fe-Cr-Ni alloys.