Ti3Al基合金高温氧化行为的原位X射线衍射研究

用高温原位Ｘ射线衍射技术分析研究了Ｔｉ３Ａｌ基合金在７００℃和８００℃的氧化行为，测定了其１００ｈ的氧化增重曲线，并用电子探针分析了氧化层截面的元素分布。实验结果表明，Ｔｉ３Ａｌ氧化过程中先形成ＴｉＯ２，氧化层组成为ＴｉＯ２与Ａｌ２Ｏ３的混合物，Ｎｂ、Ｓｉ元素可提高Ｔｉ３Ａｌ合金的抗氧化性能。促使合金表面形成ＴｉＯ２与Ａｌ２Ｏ３层，但对Ａｌ２Ｏ３的生成没有促进作用，形成ＴｉＮ层是Ｔｉ３Ａｌ合金抗氧     

二元Ti—Al合金高温氧化机理

研究了Ｔｉ－３３．３％Ａｌ，Ｔｉ－４８％Ａｌ和Ｔｉ－５２％Ａｌ（原子分数）合金在１０７３和１１７３Ｋ空气中的恒温氧化行为，用Ｘ射衍射仪（ＸＲＤ）和配有能谱仪（ＥＤＳ）的扫描电子显微镜（ＳＥＭ）对氧化层表面的相组成，形貌以及氧化层剖面的显微结构和氧化机理进行了分析，结果表明：二元Ｔｉ－Ａｌ合金的氧化层由一系列薄层组成，其氧化过程可以为三个阶段，不同化层的生长方向及氧化反应的控制步骤略有差别，氧化动力     

Cr对TiAl金属间化合物高温氧化性能的影响

研究了Ｔｉ－５０Ａｌ，Ｔｉ－４５Ａｌ－１０Ｃｒ和Ｔｉ－５０Ａｌ－１０Ｃｒ（原子分数，％）合金在８００－１１００℃下的高温氧化性能。结果表明，Ｔｉ－４５Ａｌ－１０Ｃｒ合金在８００和９００℃形成的氧化膜具有与ＴｉＡｌ合金同样的分层结构，外层为ＴｉＯ２，内层为ＴｉＯ２和Ａｌ２Ｏ３的混合氧化物，在内外氧化层中间有一富Ａｌ２Ｏ３４的中间层，但内氧化层中有大量Ｃｒ掺杂，其氧化增重比Ｔｉ－５０Ａｌ的大，而１００     

EFFECT OF Cr ON MICROSTRUCTURE OF Ti_3Al＋TiAl ALLOYS

研究了Ｔｉ－４４．９Ａｌ（ａｔ．－％）和Ｔｉ－４４．３Ａｌ－３Ｃｒ（ａｔ．－％）合金的铸态组织及其在热处理过程中的变化。结果表明：Ｃｒ增加了Ｔｉ－Ａｌ合金中ＴｉＡｌ（γ）相的含量，促使Ｔｉ３Ａｌ（α２）相由片状变成块状；加速了α２＋γ片状组织的不连续粗化过程，形成了尺寸较小的新生α２＋γ晶。因此，加Ｃｒ和１１５０℃长时热处理是细化α２＋γ两相合金铸态粗晶组织的有效途径；Ｃｒ促进有序体心立方β２相的     

Ti－Al系金属间化合物的高温热腐蚀

研究了Ｔｉ３ＡＬ，Ｔｉ３Ａｌ－Ｎｂ及ＴｉＡｌ金属间化合物在９００℃及９５０℃空气中当表面有（０．９Ｎａ，０．１Ｋ）２ＳＯ４盐膜存在时的高温热腐蚀行为．结果表明，Ｔｉ３Ａｌ，ＴｉＡｌ金属间化合物在９００、９５０℃遭受严重的热腐蚀．合金表面均没有形成单一的Ａ１２Ｏ３保护层，而是形成外层为富ＴｉＯ２层，内层为ＴｉＯ２、Ａ１２Ｏ３或Ｎｂ２Ｏ５的混合氧化物层，在氧化膜／合金基体界面形成一些硫化物．合金的腐蚀以电化学机制进行．硫化物的形成也促进了电化学反应的阳极过程．向Ｔｉ３Ａｌ中添加Ｎｂ可以显著地改善其热腐蚀性能，这归因于Ｎｂ促进富Ａｌ氧化物内层的形成．ＴｉＡｌ的耐蚀性能优于Ｔｉ３Ａｌ基合金．     

TiAlCr涂层对TiAl金属间化合物抗高温氧化性能的影响

研究了溅射Ｔｉ－５０Ａｌ－１０Ｃｒ涂层在８００－１０００℃对ＴｉＡｌ金属间化合物抗高温氧化性能的影响。结果表明,ＴｉＡｌ合金由于形成Ａｌ２Ｏ３和ＴｉＯ２的混合氧化物而表现出较差的抗高温氧化性能,而ＴｉＡｌＣｒ层由于形成粘附性了的Ａｌ２Ｏ３膜而大大提高了ＴｉＡｌ的恒温及循环氧化性能,经９００℃１０００ｈ长时间氧化。ＴｉＡｌＣｒ涂层对ＴｉＡｌ合金仍能提供很好的防护,涂层和基格结合我孔洞及裂纹出现,表现     

表面涂少量氯化锰提高Ti47Al2Cr2Nb合金高温抗氧化性

研究了表面涂少量ＭｎＣｌ２ 对Ｔｉ４７Ａｌ２Ｃｒ２Ｎｂ 合金９０００Ｃ 恒温氧化行为的影响。涂少量ＭｎＣｌ２ 后合金的氧化速率降低了５０ ％ 以上,氧化膜也由ＴｉＯ２ 和Ａｌ２Ｏ３ 的混合物变为以Ａｌ２Ｏ３ 为主的氧化物。发生上述变化的原因可能在于氧化开始时合金中钛与Ｃｌ 反应形成钛的亚稳态氯化物挥发掉,合金表面形成一层致密的氧化铝膜,阻碍合金中的Ｔｉ 向外扩散氧化,因此提高了合金的高温抗氧化性能     

TiAl基合金高温氧化动力学分析

关于ｉＡｌ的高温氧化问题，国内外已有广泛报道［１，２］，但缺乏对氧化产物的系统分析．本文从氧化物生成热力学角度讨论了二元ＴｉＡｌ及三元ＴｉＡｌ－Ｃｒ合金氧化产物的生成趋势，旨在为ＴｉＡｌ氧化层构造研究提供理论基础．１ＴｉＡｌ氧化物的热力学计算 二元ＴｉＡｌ在９７３Ｋ以上高温氧化时，生成两种稳定的氧化物［３］：Ｒ－ＴｉＯ２和α－Ａｌ２Ｏ３。由于ＴｉＯ２与Ａｌ２Ｏ３的生成自由能相近［４］，在原子比约为 １：１的 ＴｉＡｌ基合金中，将几乎同时生成两种氧化物，故不能形成单一致密的Ａｌ２Ｏ３保护层． 式中：气…     

几种Ni-Cr-Al墓低偏析高温合金的抗氧化性能研究

在１０００～１１００℃之间,对三种Ｃｒ、Ａｌ含量及微量元素Ｓ、Ｚｒ含量不同的Ｎｉ－Ｃｒ－Ａｌ基合金进行了恒温和循环氧化实验。结果表明,高Ｃｒ（１６Ｗｔ％）,低Ａｌ（３．５Ｗｔ％）、Ｓ（０．００５ｗｔ％）含量,且不含Ｚｒ的合金其氧化膜层主要由连续致密的Ｃｒ２Ｏ３外氧化层和树根状Ａｌ２Ｏ３内氧化层构成,氧化膜的粘附性较好。高Ａｌ（５ｗｔ％）,低Ｃｒ（９ｗｔ％）、Ｓ（０３００５ｗｔ％）含量,且不含Ｚｒ的合金其氧化膜主要由Ａｌ２Ｏ３,ＴｉＯ２,Ｃｒ２Ｏ３构成,氧化膜的粘附性较差,但在该合金中加入０．１Ｗｔ％Ｓ和０．１Ｗｔ％Ｚｒ,氧化膜的粘附性变好,而恒温氧化速率增加。文中对实验结果进行了综合分析。     

几种Ni—Cr—Al基低偏析高温合金的抗氧性能研究

在１０００－１１００℃之间，对三种Ｃｒ，Ａｌ含量及微量元素，Ｓ，Ｚｒ含量不同的Ｎｉ－Ｃｒ－Ａｌ基合金进行了恒温和循环氧化实验。结果表明，高Ｃｒ，低Ａｌ，Ｓ含量，且不含Ｚｒ的合金其氧化膜层主要由连续致密的Ｃｒ２Ｏ３外氧化层和树根状Ａｌ２Ｏ３内氧化层构成，氧化膜的粘附性较好。     

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.     

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.     

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     

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.     

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。     

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.     

Preferential oxidation of carbon during the initial stage of oxidation of an Fe-0.8%C alloy at 400°C

The preferential oxidation of carbon in an Fe-0.8%C alloy during the first 60 min of oxidation in air at 400°C was studied by a thermogravimetric method and by measuring the quantity of evolved carbon oxides. The morphology of the external oxide surface depended on the type of exposed phase—a rosettelike oxide grows over ferrite, whereas the oxide surface over cementite is relatively smooth. A possible mechanism for the preferential oxidation of carbon and its subsequent cessation is proposed.Formerly of Institute of Materials Engineering, Academy of Mining and Metallurgy, Cracow, Poland.     

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。     

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 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.