Fe-40%Ni合金的高温氧化行为

采用测定高温下保温不同时间后氧化层厚度的方法讨论分析了Fe-40%Ni合金的高温氧化行为,并通过回归分析得到了预测氧化层厚度的数学模型。结果表明,当温度低于1000 ℃时,合金氧化层增加的趋势相对较缓,超过1000 ℃后显著加快。随保温时间的延长,氧化层厚度以一定的速度增加,并与保温时间呈近似线性的关系,而当温度较高时则逐渐向抛物线型转变。回归分析表明,合金的氧化层厚度(μm)可用h=6700×t^0.44×e^-6870/T计算。     

Ni76Cr19AlTi合金的高温氧化行为

采用静态恒温氧化增质法研究Ni76Cr19AlTi合金在600~800℃范围内的高温氧化动力学规律,采用场发射扫描电镜对氧化产物进行表面和横断面形貌观察,用X射线衍射仪分析氧化膜层的物相组成。结果表明,合金在600~800℃范围内氧化增质与氧化时间的关系遵从抛物线规律,氧化速率常数Kp随温度的升高而增大;在800℃下氧化200 h,平均氧化速率为0.002 15 mg.cm-2.h-1,合金属于完全抗氧化级;氧化过程中,氧化膜主要受控于Cr2O3的生长,经过长时间氧化后,表层为比较疏松的TiO2和Cr2O3,内层为起保护作用的Cr2O3和Al2O3,氧化膜的组成以Cr2O3为主。     

Isothermal oxidation behavior of cast Ni-base superalloy K44

The oxidation behavior of a cast Ni-base superalloy K44 in air at 850-1 000℃ for 100 h was studied. The scales on the surface were determined by SEM and EPMA equipped with an EDXS. The results show that oxidation kinetics obey the parabolic law fi＇om which the values of activation energy Qp1=221.1 kJ/mol and Qp2=247.6 kJ/mol are estimated. The oxidation scales are composed of loose outer layer of TiO2/TiO-Cr2O3 and a small amount of NiCr204 and NiAl2O4, compact intermediate layer Cr2O3, and precipitate of internal oxides Al2O3.     

一种含铝奥氏体不锈钢的高温氧化行为

采用称量法研究了新型Cr21Ni35NbAl合金分别在700 ℃、800 ℃和900 ℃空气中的静态氧化行为,并绘制其高温氧化动力学质量增加曲线。结合X射线衍射（XRD）、扫描电镜（SEM）及能谱分析（EDS）对高温氧化膜层的形貌及结构进行表征。结果表明：新合金的高温氧化动力学质量增加曲线遵循抛物线规律,700 ℃氧化膜主要为(Fe0.6Cr0.4)2O3和少量Al2O3;800 ℃氧化膜较为复杂,主要为Al2O3、(Al0.9Cr0.1)2O3和少量Fe(Cr, Al)2O4;900 ℃时氧化膜主要为Al2O3和少量(Al0.9Cr0.1)2O3。     

含纳米ZrO2颗粒复合电铸层高温氧化行为研究

通过间歇式高温氧化实验,建立了纯镍电铸层和Ni—ZrO2纳米复合电铸层高温氧化动力学模型,分析了电铸层表面和横截面的形貌,测定了脉冲复合电铸层横截面中各组织成分的分布状态。结果表明,Ni—ZrO2纳米复合电铸层高温氧化性能明显优于纯镍铸层,复合电铸层表面生成的氧化膜晶粒细小且致密。复合电铸层表面的氧化膜与复合电铸层的黏附性较好,这是由于其较薄,并且所产生的内应力较小所致。     

Ti-16.28Si合金的高温抗氧化行为及添加Cu的影响

选用Ti、Si、Cu粉末通过高能球磨-冷压-无压烧结制备了Ti-16.28Si和Ti-15.46Si-5Cu两种合金,并在800℃、900℃、1000℃空气中对其进行高温氧化试验。利用SEM、EDS及XRD对烧结和氧化试样的表面及横截面形貌、物相组成进行分析,以研究合金的氧化机制。结果表明：两种配方试样烧结之后主要含有Ti、Ti5Si3、Ti5Si4相,加Cu配方出现Cu3Si相;加Cu后致密度升高。高温氧化80 h后,氧化试样的主要物相为TiO2,还含有少量的SiO2、Ti3O5、TiO、TiN、CuO或Cu2O相。两种合金在800℃和900℃氧化温度下都达到抗氧化等级。Ti-16.28Si合金在900?C时氧化膜表层基本上全是金红石TiO2,抗氧化性能最好。800℃下,添加Cu显著改善Ti-16.28Si合金的抗氧化性能;在Cu含量为5 wt%时其平均氧化速度仅为Ti-16.28Si合金的57.8 %;但在900℃和1000℃下,添加Cu后,Cu3Si相可降低合金的抗氧化性能。     

镍基高温合金粉末的室温吸氧特性与高温氧化行为

本文研究了不同粒径镍基高温合金粉末的球形度、比表面积、氧含量、表面氧状态和高温氧化特征,总结了粉末在室温下的吸氧特性与高温氧化行为。将氩气雾化粉末筛分为<30 μm、30 ~ 49 μm、50 ~ 60 μm、61 ~ 73 μm和74 ~ 105 μm等不同粒度。发现粒径为61 ~ 73 μm的粉末平均球形度最低,比表面积最小,且氧含量最低;粒径为30 ~ 49 μm的粉末球形度最高,比表面积最大。但粒径小于30 μm的粉末氧含量最高。粉末在950 ℃高温氧化的过程可分为两个阶段。氧化初期(0~12 h),粉末表面形成致密的NiO、Cr2O3和TiO2混合氧化层。氧化后期(大于12 h),混合氧化层脱落,抗氧化性失效。氧化24 h后氧化层明显脱落并暴露基体,抗氧化性彻底失效。高温曝露100 h后,粉末已氧化为NiO,表面无明显层状氧化物。     

激光辅助热喷涂NiCoCrAlYTa-Cr2O3-Cu-Mo涂层高温静态氧化行为

为探究高温润滑耐磨涂层抗高温氧化行为,采用激光辅助等离子喷涂技术(LPHS)在GH4065A镍基高温合金上制备NiCoCrAlYTa-Cr₂O₃-Cu-Mo涂层,研究了该涂层在(850～1000)℃×220 h的抗高温氧化行为。计算得出氧化激活能约为128.5 kJ·mol^-1,850、900、1000℃氧化速率常数分别为1.44×10^-2、3.61×10^-2、7.71×10^-2 mg²·cm^-4·h^-1。结果表明,850℃×220 h氧化后表面生成Al₂O₃为主的连续致密氧化膜,阻碍涂层内部的进一步氧化;1000℃×220 h氧化后表面生成疏松NiO为主,致密Cr₂O₃·NiO为辅的氧化膜。致密氧化膜的生成阻止了涂层及基体的进一步氧化。     

中碳钢盘条的高温氧化行为研究

针对中碳钢盘条的高温氧化问题,利用热重分析仪对45钢和40Cr钢盘条的高温氧化行为进行了试验研究;采用场发射电子探针表征了氧化铁皮厚度及截面微观形貌,对氧化铁皮形貌演变规律以及合金元素在氧化铁皮与基体界面处的分布规律进行了研究分析。结果表明:45钢和40Cr钢盘条的氧化增重曲线在1 050~1 250 ℃范围内遵循抛物线规律,当氧化条件相同时,相比于常规低碳钢,其氧化激活能较高,抗氧化性能更好;氧化铁皮呈典型的3层结构,从外到里分别为Fe₂O₃、Fe₃O₄及FeO,并且在氧化铁皮与基体界面处存在合金元素富集层;45钢盘条在高温氧化时,Cr元素分布不明显,Si元素在氧化铁皮与基体界面处有少量富集,Mn元素在氧化铁皮中均匀分布;40Cr钢盘条在氧化铁皮与基体界面处不仅有富Si层,还明显存在一层均匀完整的富Cr层,由于合金元素富集层阻碍了Fe²⁺向外扩散,提高了盘条的高温抗氧化性能。     

氧化时间及铬含量对Fe-Cr钢高温氧化行为的影响

为了测定不同氧化时间以及铬含量对高温条件下钢材表面氧化铁皮组织和厚度的影响,将Fe-5Cr钢与Fe-10Cr钢在1000℃空气条件下氧化60～180 min,采用增重法绘制其氧化动力学曲线,并利用光学显微镜、能谱仪和X射线衍射仪对氧化铁皮的断面形貌和物相进行研究.结果表明,两试验钢氧化初期为气-固反应,中后期为气...     

High-temperature oxidation of pure titanium in CO2 and Ar-10%CO2 atmospheres

The oxidation behavior of pure titanium has been investigated in the temperature range of 1000 K to 1300 K in CO₂ or Ar-10%CO₂. Optical microscopy, electron probe microanalyses, and X-ray measurements on the oxide scales formed during oxidation indicate that their structures are nearly independent of temperature and the corrosion atmosphere. The scales consisted of two layers, an external one and an internal one, having a rutile (TiO₂) structure. The parabolic rate law was confirmed for growth of the external scale and the permeation depth of oxygen in titanium with apparent activation energies of 266 and 226 kJ/mol, respectively. The rate-determining diffusion species in the oxidation processes are discussed.     

2507双相不锈钢高温氧化行为

通过高温氧化试验(1200℃,保温5 min,氧化气氛A和B)模拟了2507双相不锈钢热轧初期的氧化过程,并应用扫描电子显微镜( SEM)、辉光放电光谱仪(GDS)、X射线衍射仪(XRD)和X射线光电子能谱仪(XPS)等手段,分析了不同气氛下氧化膜的组成和结构以及初期氧化特性.结果表明:氧化膜主要由Fe3O4、Cr2O3和尖晶石型(FeCr2O4、MnCr2O4等)等复合氧化物组成;气氛中氧含量的变化可改变氧化膜中氧化物结构、组成,铁素体优先于奥氏体氧化.     

Comparisons of high temperature oxidation behavior between reactive-sintered and melted Ti-45at.%Al-1.6at.%Mn intermetallics

In order to investigate high temperature oxidation behavior, isothermal oxidation experiments for Ti-45at.%Al-1.6at.%Mn intermetallics prepared by both reactive sintering and melting were carried out in both oxygen and air environments at temperatures of 900, 1000 and 1100°C. In the oxygen environment, reactive sintered Ti-45at.%Al-1.6at.%Mn was found to have excellent oxidation resistance due to the formation of a continuous A1₂O₃ layer at temperatures up to 1100°C; however, when melted it showed very poor oxidation resistance at and above 1000°C. Weight gains of the melted specimen after 12 hours, especially at the temperature of 1000°C and 1100°C, were nearly 12 times that of the reactive sintered one. In air, the reactive-sintered intermetallics showed a poorer oxidation resistance man did that in the oxygen environment. Especially, the weight gains in air were 6 times larger than the weight gains in oxygen when oxidized at 1100°C for 12 hours.     

Cu-20Ni-30Cr合金在700℃和800℃纯氧气中的氧化

研究了三元复相合金Cu-20Ni-30Cr（at%）在700℃和800℃纯氧气中的氧化行为，合金由三相组成，具有最大Cu浓度和最小Cr浓度的α相为合金的基体，中间浓度的Ni和Cr的β相和富Cr的γ相以颗粒状态分布在合金基体中。合金在2个温度下的氧化动力学曲线偏离抛物线规律，其氧化增重随时间延长而降低，合金氧化速率随温度升高而加快，合金形成了复杂的氧化膜结构，外层为富Cu氧化物，中间层为尖晶石层，最内层为不规则但连续的Cr2O3膜，合金中的复相组织限制Cr在合金中的扩散，抑制了外氧化膜的形成。     

Oxidation behavior of TiAl coated with a fine-grain Co-30Cr-4Al film

The oxidation behavior of TiAl coupons coated with a fine-grain Co-30Cr-4Al (mass %) film of about 30-m thickness has been studied at 1100–1400 K in a flow of purified oxygen at atmospheric pressure for up to 500 ks. Three oxidation stages were recognized: initial transient, parabolic, and accelerated stages. However, at 1100 K a parabolic stage continues for more than 800 ks. The activation energy for parabolic oxidation agrees with reported values for the oxidation of alumina-former alloys, although the mass gains during the parabolic stages are relatively small at 1200 and 1300 K. Micropores developed mainly at the scale/coating and coating/substrate interfaces as oxidation proceeded. This is attributable to recrystallization of the coating during oxidation and a Kirkendall effect due to preferential diffusion of Co into the substrate. The accelerated oxidation can be explained in terms of the formation of rutile mounds on the scale.     

300M钢的高温氧化行为

研究了300M钢在700~1200 ℃高温下的氧化行为,利用扫描电镜(SEM)和X射线衍射仪等手段观察分析了氧化层的表面形貌、微观组织结构成分,并结合氧化动力学曲线,分析了300M钢在700~1200 ℃高温氧化的氧化机理。研究结果表明,300M钢在700~1200 ℃的氧化遵循抛物线规律。高温条件下其氧化皮为典型的3层结构,即内氧化层、中间氧化层及外氧化层,中间氧化层又分为多孔层和疏松层。当氧化温度为1200 ℃时,FeO层晶粒内部的合金化元素Si、Cr等快速聚集并形成粗大的氧化物,此时FeO层完全失去抗氧化作用,氧化速率急剧加快。     

Oxidation and sulfidation behavior of Fe-20Cr-16Ni-4Al-1Y2O3 oxide-dispersion-strengthened alloy

High-temperature oxidation and sulfidation studies were conducted on an oxide-dispersion-strengthened alloy of composition Fe-20Cr-16Ni-4Al-1Y₂O₃. The oxidation studies were conducted in air and low-PO₂ environments over a temperature range of 650–1200°C. Results are also reported on the sulfidation resistance of preformed oxide scales and the influence of reoxidation of preformed sulfide scales. Detailed microstructural results and x-ray diffraction analysis data are presented to substantiate the corrosion behavior of the alloy over the wide range of conditions anticipated in fossil-energy systems. Data are also presented on the corrosion behavior of the alloy in oxygen/sulfur mixed gas atmospheres, and the results are used to compare the corrosion behavior of the present alloy with other chromia- and alumina-forming alloys.     

High-temperature oxidation of Fe-16.7% Mn-2.1% Ni-6.6% Si alloy in SO2

The oxidation of an austenitic Fe-16.7% Mn-2.1% Ni-6.6% Si (by weight) alloy in SO₂ in the temperature range 600–900°C is described. The corrosion products formed on this alloy in this environment below 800°C consist only of oxides, rather than a mixture of oxides and sulfides as is observed for unalloyed Fe or Mn. The kinetics of oxidation of the alloy in SO₂ in this temperature range are similar to those in O₂. It is proposed that these characteristics result from the presence of a thin silicate layer near the scale-metal interface that alters the gradient of oxygen potential within the scale.