Nb对TiNiAl合金高温氧化行为的影响

对Ti50Ni44Al6和Ti50Ni41Al6Nb3合金在1073K循环氧化行为的测试表明,Nb的加入显著改善合金的高温抗氧化性能．Ti50Ni44Al6合金在1073K经过100h循环氧化后形成外层以TiO2为主并含有少量Al2NiO4、内层为TiNiO3的氧化层,合金的氧化动力学服从线性规律;Ti50Ni41Al6Nb3合金生成以TiO2为主的氧化膜,在外氧化层下面形成了一层富Nb和Al的复合氧化物,显著阻碍氧以及合金元素的扩散,降低了合金的氧化速率,合金高温氧化动力学遵从抛物线规律．     

Ti50Al和Ti45Al8Nb合金高温初期氧化行为

利用SEM、XPS和AES研究了Ti50Al和Ti45Al8Nb(原子分数,%)合金在900 ℃空气中的初期氧化行为.结果表明:Nb的加入显著提高了合金的抗氧化性.氧化90 min后,Ti50Al合金表面为粗大的富TiO2颗粒,冷却过程中部分表层氧化膜脱落,脱落后内层为多孔、疏松的Ti和Al的混合氧化物(可能有氮化物);Ti45Al8Nb合金表面生成很薄的氧化膜,其外层为细小富Al2O3颗粒,Nb只存在于内层(富TiO2层)和混合层,在外层Al2O3内没有发现,Nb5 取代TiO2中的Ti4 ,降低氧空位浓度从而减慢氧的向内扩散,抑制TiO2的生成,同时促进了外层纯Al2O3层的形成,该层阻碍氧以及合金元素的进一步扩散.     

Ni-Al涂层对Ti-22Al-26Nb合金抗氧化性能的影响

采用爆炸喷涂技术在Ti-22Al-26Nb(原子分数,％)基体上制备了Ni-68．5Al(原子分数,％)合金涂层,涂层在退火后与基体结合良好．XRD分析表明,退火后涂层主要由β-NiAl以及少量Al3Ti和Al3Nb组成．研究了Ni—Al涂层对Ti-22Al-26Nb合金在800℃静态空气中氧化性能的影响．Ti-22Al-26Nb合金氧化后主要生成了疏松多孔的TiO2,其抗高温氧化性能很差．施加Ni—Al涂层后,高温下生成了一层致密的Al2O3,氧化动力学曲线满足抛物线规律,抗氧化性能显著提高．     

基于卤素效应的阳极氧化技术提高Ti48Al5Nb合金抗高温氧化性能

采用电化学阳极氧化技术在含NH_4F的乙二醇电解液中对Ti48Al5Nb合金进行阳极氧化处理,以获得富铝含氟阳极氧化膜。研究了阳极氧化处理对Ti48Al5Nb合金在1000℃空气中的氧化行为及氧化膜组成和结构的影响。结果表明:阳极氧化处理的Ti48Al5Nb合金经高温氧化后表面可形成连续、致密的Al_2O_3氧化膜,且氧化膜与基体具有良好结合力,有效阻止了氧向内扩散,进而显著提高了合金的抗高温氧化性能。经1000℃氧化100 h后,阳极氧化试样增重由未经阳极氧化处理试样的26.73 mg/cm~2降至1.18 mg/cm~2。同时,阳极氧化处理改变了合金的氧化机制,抑制了氧化膜/基体界面处富Nb层的出现。阳极氧化提高Ti48Al5Nb合金抗高温氧化性能是由于氧化膜中F在高温氧化过程中表现出的"卤素效应"所致。     

合金元素对Nb-Ti-Al-C合金氧化行为的影响

利用真空非自耗电弧炉制备不同Al含量的Nb-25Ti-8C合金,研究Nb-Ti-Al-C合金的组织结构及其高温氧化行为。研究表明,Nb-25Ti-8C-(0,5,10)Al合金由Nbss和(Nb,Ti)C两相构成;Nb-25Ti-8C-15Al合金由Nbss、(Nb,Ti)C和Nb3Al三相构成。800~1000℃氧化过程中,合金氧化膜为由Nb2O5,Ti O2,Al2O3,Nb O2及Ti Nb2O7多种氧化物构成的混合氧化膜。Ti、Al活性元素可优先与氧发生选择性氧化,抑制氧化物Nb2O5生成,提高氧化膜致密度和合金抗氧化性,并且氧化温度越高,Al元素改善铌合金抗氧化性能效果越明显。Nb-25Ti-8C合金800℃氧化时表现出良好的抗氧化性能,1000℃氧化时Nb-25Ti-8C-x Al合金的抗氧化性能明显优于C-103。随氧化温度升高,氧化膜中Nb2O5含量增加,导致氧化膜与合金基体的内应力增大,引起外层氧化膜脱落。碳化物中C元素以CO2形式挥发导致氧化层表面形成氧化空洞。     

基于Ti1100合金的微量元素添加对合金抗氧化性能的影响

本文利用固溶体合金中的‘团簇加连接原子’模型解析了典型高温近α-Ti合金Ti1100的成分,其团簇成分式为[Al-(Ti13.7Zr0.3)](Al0.69Sn0.18Mo0.03Si0.12)。在此基础上,采用相似元素替代原则设计了微量元素Hf、Ta和Nb添加的系列合金成分,即 [Al-(Ti13.7Zr0.15Hf0.15)](Al0.69Sn0.18Si0.1(Mo/Ta/Nb)0.03)。对该系列合金进行950 ℃/1 h固溶+560 ℃/6 h时效处理,然后进行组织结构、硬度、抗高温氧化及电化学腐蚀性能测试。研究结果表明,Zr0.15Hf0.15合金与参比合金具有相同片层β转变组织,而在此基础上Ta和Nb的添加会使合金中产生大量等轴α组织;但组织的改变对系列合金的显微硬度影响不大,介于330-370 HV。650 ℃氧化100 h后系列合金均具有较强的抗氧化能力,氧化增重小于1.0 mg/cm2,而在800 ℃氧化100 h后,添加Hf、Ta、Nb元素的合金氧化增重明显低于Ti1100合金,氧化层厚度为25~27 μm,且氧化层致密,其中[Al-(Ti13.7Zr0.15Hf0.15)](Al0.69Sn0.18Si0.1Ta0.015Nb0.015)合金具有最优的抗高温氧化性能,800 ℃/100 h后的氧化增重仅为2.6 mg/cm2。此外,该系列合金在在3.5 %NaCl溶液中也具有较好的耐蚀性。     

Ti对Nb基合金高温抗氧化性能的影响

采用热重分析(TG)、X射线衍射(XRD)、透射电镜(TEM)及能谱分析(EDS)等方法,研究Nb-Si-Ti(15%~26%,摩尔分数)-Hf-Al-Cr多元合金、Nb-Ti(0~50%)二元合金在1250℃大气中的高温氧化行为。通过Ti含量变化对合金氧化产物种类及氧化物PBR值的影响,探讨Ti含量对Nb基合金高温抗氧化性能的作用。结果表明:随着Ti含量的增加,合金的高温氧化产物从Nb2O5、Ti2Nb10O29、TiNb2O7和TiO2依次过渡。通过计算发现:Nb基合金的氧化产物Nb2O5、Ti2Nb10O29、TiNb2O7及TiO2的PBR值随着Ti含量的升高依次减小。氧化产物PBR值的下降,可以有效地降低Nb基合金氧化膜的生长应力、提高氧化膜的完整性、增大氧化膜的失效周期,提高Nb基合金的高温抗氧化性能。     

合金元素Nb在TiAl高温氧化行为中的作用

研究了Ti-45Al-10Nb(at%)合金在800℃－960℃氧气和空气中的氧化行为，并与Ti-50Al(at%)合金作一对比，表明该合金具有较好的高温抗氧化性能，其氧化增重速率略优于文献报道的铁基耐热不锈钢，发现了Ti-45Al-10Nb合金在空气中的氧化增重速率明显低于在纯氧中的氧化增重速率，X－射线相分析与能谱分析表明氧化产物主要由TiO2与Al2O3组成，但空气中氧化后的氧化产物中含TiN相，认为它是降低氧化速率的主要原因，并且认为合金元素Nb稳定了氧化层中的TiN相，因而提高了合金在空气中的抗氧化性能。     

合金元素对Co-Al-W合金高温氧化行为的影响

研究新型Co-Al-W合金在800和900℃空气中氧化动力学及元素Mo、Nb、Ta和Ti对合金高温氧化行为的影响。结果表明:在800℃氧化100 h后,Co-8.8Al-9.8W(摩尔分数,%)和Co-8.8Al-9.8W-2Ta合金的质量增加较小,表明其抗高温氧化能力较强;在900℃氧化时,Co-8.8Al-9.8W-2Mo、Co-8.8Al-9.8W-2Nb、Co-8.8Al-9.8W-2Ta和Co-8.8Al-9.8W-2Ti合金的质量增加小于Co-8.8Al-9.8W合金的,表明加入合金元素可以提高合金的抗高温氧化能力;在不同温度下,Co-Al-W合金氧化膜表面出现团聚、开裂和脱落现象;氧化膜分为3层,外层为Co3O4氧化物,中间层为W、Al和合金元素的复杂氧化物,内层为Co和Al的氧化物。从合金氧化动力学曲线来看,在800℃时合金元素增强Co-Al-W合金抗高温氧化能力由强至弱依次为Ta、Ti、Mo、Nb;在900℃时按Ti、Ta、Mo、Nb顺序依次减弱。     

合金元素及搪瓷涂层对Ti3Al系列合金抗氧化性能的影响

研究了Nb,V,Ta等合金元素及搪瓷涂层对Ti3Al基合金抗氧化性能的影响.结果表明只有加入中等浓度(约17%)的Nb及合适浓度的Ta才有利于提高合金的抗氧化性能;V的添加可使TiO2产物疏松多孔,加速了O在氧化膜中的扩散而使合金氧化严重,但随着浓度的进一步增加,V可能起有益作用;搪瓷涂层由于具有稳定的热化学稳定性及与基体合金相近的热膨胀系数,能够显著提高合金的抗高温氧化性能.     

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.