Fe—23Cr—5Al合金1000^0C氧化形成的Al2O3膜生长应力研究

采用一种测定氧化膜生长应力的双面氧化弯曲方法,测量了Ｆｅ－２３Ｃｒ－５Ａｌ（Ｆｅ－２２．６Ｃｒ－．４２Ａｌ－０．２１Ｔｉ,ｗｔ％）合金在１０００＾０Ｃ空气中氧化形成的Ａｌ２Ｏ３膜的平均生长应力,研究了氧化膜应力释放机制,Ａｌ２Ｏ３膜的平均生长应力随膜厚增大而减小,其大小从－１ＧＰａ数量级变化到－１００ＭＰａ数量级。基体全金和Ａｌ２Ｏ３膜在１０００＾０Ｃ时均发生蠕变,合金氧化一定时间后于真空保温退火     

表面涂覆CeO2对Fe—23Cr—5Al合金上Al2O3膜生长应力的影响

研究了表面涂覆ＣｅＯ２对Ｆｅ－２３Ｃｒ－５Ａｌ合金９００℃和１０００℃下形成的Ａｌ２Ｏ３膜生长应力的影响。涂覆ＣｅＯ２增大了合金的氧化速率,促进了Ａｌ２Ｏ３膜的起皱同时也增大了Ａｌ２Ｏ３膜的生长应力。涂覆ＣｅＯ２表面形成的起皱的Ａｌ２Ｏ３膜在冷却过程中剥落量较少;而在真空保温过程中应力不容易释放。认为表面涂覆ＣｅＯ２对Ｆｅ－２３Ｃｒ－５Ａｌ的抗氧化并不能起到改善作用。     

离子注入Ce对Fe—23Cr—5Al合金上AI2O3膜生长应力的影响

利用双面氧化弯曲方法原位测量了Ｆｅ－２３Ｃｒ－５Ａｌ合金空气中氧化形成的ＡＩ２Ｏ３膜平均生长应力。ＡＩ２Ｏ３膜内存在压应力。９００℃下氧化２０ｈ,膜内应力从３．５降低到２ＧＰａ,１０００℃下氧化１０ｈ,膜内应力从０．８降低到０．４ＧＰａ,合金表面离子注入１×１０＾１７Ｃｅ＾＋／ｃｍ＾２,增大了ＡＩ２Ｏ３膜的生长应力,其原因是添加稀土促进膜的横向生长,离子注入Ｃｅ同时增大了合金的氧化速率,促进了ＡＩ     

渗铝NiAl－20％Fe金属间合金的高温热腐蚀

本文研究了在９５０℃空气中，表面涂Ｎａ_２ＳＯ_４盐膜的条件下，ＮｉＡｌ，ＮｉＡｌ－２０％Ｆｅ及渗铝后的高温热腐蚀行为。在热腐蚀过程中，ＮｉＡｌ合金表面能形成Ａｌ_２Ｏ_３膜，显示出一定的耐蚀性能。但Ａｌ_２Ｏ_３膜易开裂，Ａｌ_２Ｏ_３膜的溶解及开裂会引发合金发生快速热腐蚀；２０％Ｆｅ的加入则使ＮｉＡｌ合金的耐蚀性能显著变差，合金表面不能形成单一的Ａｌ_２Ｏ_３膜；渗铝处理可以明显提高ＮｉＡｌ－２０％Ｆｅ合金的耐蚀性能，且渗铝涂层的耐蚀性能优于ＮｉＡｌ合金，这与铝化物涂层中的Ａｌ含量较高，Ａｌ_２Ｏ_３膜的开裂倾向较小有关。     

MA956和Fecraloy两种合金氧化膜的断裂应变

利用四点弯曲／声发射方法在室温下测量了ＨＡ９５６和Ｆｅｃｒａｌｏｙ合金表面形成的氧化膜的断裂应变。结果表明，在张应力作用下，ＭＡ９５６合金在１０００℃、１１００℃和℃三种温度以下及Ｆｅｃｒａｌｏｙ合金在１２００℃下不同时间氧化后形成的膜的断裂应变几乎不变，分别约为０．３４％和０．１３％。这两种合金氧化时都主要形成Ａｌ２Ｏ３。ＭＡ９５６合金氧化膜在实验时间范围内从未发现有开裂，而Ｆｅｃｒａｌｏｙ合金     

渗铝NiAl—20?金属间合金的高温热腐蚀

本文研究了在９５０℃空气中，表面涂Ｎａ２ＳＯ４盐膜的条件下，ＮｉＡｌ，ＮｉａＬ－２０％Ｆｅ及渗铝后的高温热腐蚀行为。在热腐蚀过程中，ＮｉＡｌ合金表面形成ＡｌＯ３膜，显示出一定的耐蚀性能。但Ａｌ２Ｏ３膜易开裂，Ａｌ２Ｏ３膜易开裂，Ａｌ２Ｏ３膜的溶解开裂会引发合工发生快速热腐蚀，２０％Ｆｅ的加入则使ＮｉＡｌ合金的耐蚀性能显著变差，合金表面不能形成单一的Ａｌ２Ｏ３膜；渗铝处理可以明显提高ＮｉＡｌ－２０＾     

Fe—Mn─Al合金的腐蚀性能与钝化膜的研究

应用阳极极化及ＡＥＳ／ＸＰＳ技术,研究了Ｆｅ－３０．８Ｍｎ－８．２Ａｌ奥氏体合金在ｐＨ值为－０．８至１５．３的水溶液中的腐蚀性能,并与Ｆｅ－３０Ｍｎ合金、低碳钢、９％Ｎｉ低温钢及１Ｃｒ１３不锈钢进行对比。在所测试的水溶液中,该合金的腐蚀抗力优于低碳钢和Ｆｅ－３０Ｍｎ合金,与９％Ｎｉ钢相当,但不及１Ｃｒ１３不锈钢。Ｆｅ－３０．８Ｍｎ－８．２Ａｌ合金在１ｍｏｌ／ＬＮａ２ＳＯ个中形成的钝化膜的最表层可能为氢氧化物,而膜的主体由Ｆｅ２Ｏ３、Ｍｎ２Ｏ３及Ａｌ２Ｏ３组成。     

含Mo的Ni_3Al－Fe基合金在900－1100℃空气中的氧化行为

研究了含Ｍｏ的Ｎｉ３Ａｌ－Ｆｅ基合金在９００－１１００℃空气中的等温氧化行为，利用光学显微镜、ＳＥＭ、ＥＰＭＡ、ＸＲＤ分析了氧化膜的形态和结构．研究表明，含Ｍｏ的Ｎｉ３Ａｌ－Ｆｅ基合金由γ和β相组成．对应于γ相的氧化膜由多相组成，合金元素Ｆｅ和Ｍｏ使得γ相的氧化速率增大，氧化膜的粘附性和内聚力下降，其氧化反应激活能为４２．７ｋＪ／ｍｏｌ，Ｆｅ穿过Ａｌ２Ｏ３氧化层的扩散为氧化反应的速率控制步骤．而β相中的Ｆｅ和Ｍｏ，对其抗氧化性无不利影响，氧化膜仅由Ａｌ２Ｏ３．     

Fe－Cr－Al合金在纯SO_2气氛中的高温热循环腐蚀行为

研究了Ｆｅ－２０Ｃｒ－５Ａｌ和Ｆｅ－２０ＣｒＳＡｌ－０．５Ｙ合金在１２００℃ｌａｔｍＳＯ２气氛中热循环条件下的高温腐蚀行为，并与恒温腐蚀相比较．测定了腐蚀动力学曲线，观察腐蚀产物表面，横截面和脆断断口的形貌，并分析元素的分布，确定腐蚀产物相组成．结果表明，在５０００小时实验周期内，不含钇的合金遭受氧化／硫化腐蚀，腐蚀动力学呈直线规律．含钇合金只发生高温氧化反应，腐蚀动力学与恒温腐蚀时的差别不大，仍大体符合抛物线规律．加钇有效地抑制了Ａｌ３＋在α－Ａｌ２Ｏ３中的扩散，合金表面氧化膜依赖氧的传质而成长，发展出粘着性好的柱状晶，在交变热应力作用下不易开裂和剥落，显著提高了合金的耐蚀性．     

微量元素Zr,Hf对Ni47Cr6Fe玻封合金氧化膜生长的影响

研究了微量元素Ｚｒ，Ｈｆ对Ｎｉ４７Ｃｒ６Ｆｅ玻封合金在高温湿氢气中的氧化速度，氧化膜形貌，应力及组成的影响。结果表明，Ａ１，Ｓｉ的少量添加促进合氧化，但Ｚｒ，Ｈｆ的微量添加抑制合金氧化，Ｚｒ与Ｈｆ对合金氧化速度的影响基本相同；Ａｌ，Ｓｉ促使氧化膜凸起生长，Ｚｒ，Ｈｆ促使氧化膜平滑生长，Ｚｒ，Ｈｆ的添加增加氧化膜内应力，而添加Ｓｉ，Ａｌ降低氧化膜内应力。Ｎｉ４７Ｃｒ６Ｆｅ合金氧化膜主要由Ｃｒ２Ｏ３和     

Determination of Oxide Growth Stress by a Novel Deflection Method

A new technique has been developed to monitorthe growth stresses in oxide scales by measuringspecimen deflection. Compared to the conventionaldeflection method, the new technique does not require acoating for protecting one side of the specimen fromoxidation. This new method does not have temperaturelimits and has improved precision for stress measurementin alumina scales. Two alumina-forming alloys, Fe-22Cr-5Al-0.3Y and Fe-22.6Cr4.42Al-0.21Ti,were studied with this method. During oxidation at1000°C in air, the average compressive stresses inthe alumina scales were found to decrease from ~1000 to ~100 MPa with increasing scale thickness on thetwo alloys. The growth stress in alumina scales wasdirectly proportional to the oxide growth rates. Thestresses in the substrate alloys were much lower, on the order of 1 MPa. Creep occurred in thesubstrate alloys and was taken into consideration in thestress analysis. It is believed that creep in the alloysubstrates allowed stresses in the oxide scales to relax. Annealing tests showed that thestresses relaxed much easier in thin than in thickscales.     

The Effect of Si Additions on the High-Temperature Oxidation of a Ternary Ni–10Cr–4Al Alloy in 1 ATM O2 AT 900–1000 °C

The oxidation of four Ni–10Cr–ySi–4Al alloys has been studied in 1 atm O₂ at 900 and 1000 °C to examine the effects of various Si additions on the behavior of the ternary alloy Ni–10Cr–4Al, which during an initial stage formed external NiO scales associated with an internal oxidation of Cr + Al, later replaced by the growth of a chromia layer at the base of the scale plus an internal oxidation of Al. The addition of 2 at.% Si was able to prevent the oxidation of nickel already from the start of the test, but was insufficient to form external alumina scales at 1000 °C, while at 900 °C alumina formed only over a fraction of the alloy surface. At 1000 °C the addition of 4 at.% Si produced external chromia scales plus a region of internal oxidation of Al and Si, a scaling mode which formed over a fraction of the alloy surface in combination with alumina scales also by oxidation at 900 °C. Conversely, the presence of about 6 at.% Si produced external alumina scales over the whole sample surface at 900 °C, but only over about 60 % of the alloy surface at 1000 °C. The changes in the oxidation modes of the ternary Ni–10Cr–4Al alloy produced by Si additions have been interpreted by extending to these quaternary alloys the mechanism of the third-element effect based on the attainment of the critical volume fraction of internal oxides needed for the transition to the external oxidation of the most-reactive-alloy component, already proposed for ternary alloys.     

The adhesion of alumina films to metallic alloys and coatings

The adherence of protective oxide scales to alloy substrates is governed by the stored elastic energy in the scale which drives delamination and the fracture resistance of the alloy oxide interface. Clearly, any modifications to the alloy or the exposure environment which decreases the former or increases the latter will improve the durability of a given system. The stored elastic energy is determined by the stress level in the scale and the scale thickness. The stress state in the scale is determined by stresses which arise during the oxide formation (Growth Stresses), stresses produced during temperature changes as the result of thermal expansion mismatch between the oxide and the alloy (Thermal Stresses), and any stress relaxation which occurs as the result of creep of the scale or alloy. The fracture energy of the interface is a function of the composition at the interface, the microstructure in the interfacial region, and the composition of the exposure environment. This paper focuses on the results of studies of a variety of alloys and coatings, all of which form continuous alumina scales, in which it has been attempted to evaluate the effects of various alloy and exposure parameters on the stress state in the scale, the microstructure of the alloy/oxide interface, and the fracture resistance of the interface. The alloy parameters include alloy type, sulfur content, and reactive element content. The exposure parameters include oxidation temperature, temperature profile during exposure, and water vapor and sulfur contents of the atmosphere.     

Growth Stresses in the Oxide Scales on TiAl Alloys at 800 and 900°C

In the oxidation of TiAl alloys, the role of scale-growth stresses formed during oxidation has, thus far, been unknown. In the present paper the oxide-growth stresses were investigated by the deflection-test method in monofacial oxidation (DTMO) accompanied by acoustic-emission measurements. On unmodified surfaces the growth stresses are compressive and reach levels of around –100 MPa. At the same time, significant acoustic emission occurs indicating that even under isothermal conditions, stresses are relieved by a scale-cracking mechanism. For oxide scales on TiAl surfaces, which had been ion implanted with chlorine before oxidation, a very thin protective alumina layer is formed which, however, develops growth stresses in the range of several GPa, accompanied by intensive acoustic emission. In all stress–time curves, a dynamic situation is observed. This consists of phases of stress relief by scale microcracking and phases of stresses increase due to crack healing and further oxide growth. As a result, the level of stress as a function of oxidation time, is characterized by an oscillating course.     

微晶化对Ni20Cr合金热生长氧化膜应力的影响

利用氧化膜应力原位测量装置对Ni20Cr微晶涂层/合金体系在1000℃空气中氧化过程中发生的弯曲挠度变化进行测量.结果表明,微晶涂层1000℃氧化所形成的Cr_2O_3氧化膜中存在压应力,应力绝对值高于相同厚度的合金表面的热生长氧化膜,其原因在于涂层/Cr_2O_3界面结合好,应力释放较小.降温冷却过程中,通过微晶涂层...     

Investigation of average growth stresses in Cr2O3 scales measured by a novel deflection method

1　ＩＮＴＲＯＤＵＣＴＩＯＮＤｕｒｉｎｇｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｏｘｉｄａｔｉｏｎ ,ｔｈｅｓｔｒｅｓｓｅｓａｒｅｄｅｖｅｌｏｐｅｄｇｅｎｅｒａｌｌｙｉｎｏｘｉｄｅｓｃａｌｅｓ .Ｔｈｅｓｔｒｅｓｓｅｓｍａｉｎｌｙｒｅｓｕｌｔｆｒｏｍｔｈｅｉｓｏｔｈｅｒ     

Modeling of Residual Stress in Oxide Scales

The magnitude of the residual stress in an oxidescale, and how this varies with temperature, is of majorimportance in understanding the failure mechanisms ofoxide scales. This stress encompasses both growth stresses introduced at the oxidationtemperature and thermal-expansion-mismatch stressesinduced on heating and cooling, as well as anyexternally applied stresses or stress relaxation whichtakes place in the scale/substrate system. Althoughsome of these components are reasonably well understood(e.g., thermal stresses), growth stresses and therelaxation of the total scale stress by creep orfracture processes are much less well understood. Inthis study a model has been developed to predict stressgeneration and relaxation in oxide scales as a functionof time and temperature for both isothermal exposure and cooling to room temperature. The modeldetermines growth stress and thermal-stress generationin the scale and how this is balanced by stresses in thesubstrate. The substrate stresses are then allowed to relax by creep and the scale stressesrecalculated. This model accurately predicts theroom-temperature scale stresses for a range ofscale/alloy systems. The model can be used to show howthe scale stress depends on oxidation temperature,cooling rate, substrate, and scale thickness. The modelpredictions are discussed in light of experimentalobservations for alumina scales on FeCrAlY.     

The Oxidation of Two Ternary Ni–Cu–5 at.%Al Alloys in 1 atm of Pure O2 at 800–900°C

The oxidation of a Ni-rich and a Cu-rich single-phase ternary alloy containing about 5at.% aluminum has been studied at 800 and 900°C under 1atm O₂. The behavior of the Ni-rich alloy is similar to that of a binary Ni–Al alloy with a similar Al content at both temperatures, with formation of an external NiO layer coupled to the internal oxidation of aluminum. The Cu-rich ternary alloy shows a larger tendency to form protective alumina scales, even though its behavior is borderline between protective and non-protective. In fact, at 800°C, after an initial stage of fast reaction during which all the alloy components are oxidized, this alloy is able to develop a continuous layer of alumina at the base of the scale which prevents the internal oxidation of aluminum. On the contrary, at 900°C the innermost alumina layer undergoes repeated rupturing followed by healing, so that internal oxidation of Al is only partly eliminated. As a result, the corrosion kinetics of the Cu-rich ternary alloy at 900°C are much faster than at 800°C and very similar to those of pure copper and of Al-dilute binary Cu–Al alloys. Possible reasons for the larger tendency of the Cu-rich alloy to form external alumina scales than the Ni-rich alloy are examined.     

Effect of Zr on the Oxidation Properties of Fe3Al Intermetallic Compound

This review is concerned with the effect of the addition of zirconium as a third element on the heat-resisting properties of Fe3Al intermetallic compounds and explains their high-temperature oxidation mechanism. The Fe3Al and Fe3Al-0.05Zr specimens were isothermally oxidized in the temperature range of 1173～1473 K in synthetic air for 100 h. The formation of the alumina layer approximately obeyed the parabolic rate law, with the exception of short initial stage. The parabolic rate constant values for the Zr-doped Fe3Al decreased at all tested temperatures. Fe3Al revealed massive spallation, whereas Fe3Al-Zr produced a fiat, adherent oxide layer. The microstructure investigations of the alumina scales grown thermally on the Fe3Al-Zr alloy by means of SEM-EDS showed that they were 1.5～2 μm thick and consisted of a small inner columnar layer and an equiaxed outer grain layer. Additionally, very fine (50～150 um) oxide particles rich in Zr were found across the alumina scales. The addition of Zr significantly affected the oxidation behavior of Fe3Al by improving the adherence of the α-Al2O3 scale. TEM-SAD investigations of the alumina scales on samples prepared using the FIB (Focused Ion Beam) method confirmed the presence of small tetragonal zirconia grains near the scale/gas and alloy/scale interfaces, most of which were formed along alumina grain boundaries(gbs). Zr gb-segregation was found using HRTEM. The role of preferential formation of zirconium oxide along the alumina scale grain boundaries and the effect of Zr gb-segregation on oxidation and scale growth mechanisms were analyzed by means of two-stage oxidation experiments using 16O2/18O2. The SIMS oxygen isotope profiles for the Fe3Al-Zr alloy oxidized at 1373 K, after two-stage oxidation experiments, revealed that oxygen anion diffusion is predominant compared to that of aluminum cation diffusion.