Ti600合金的高温氧化行为研究

研究了Ti600合金在600~750℃下的高温氧化行为。采用连续氧化增重的方法及氧化速度常数、氧化活度等理论计算了合金氧化的热力学和动力学规律;用XRD、SEM、EDS等手段研究保护膜的表面相结构和表面形貌以及截面元素分布。结果表明:Ti600合金在700℃以下均有较好的抗氧化性能,其连续氧化动力学曲线基本符合抛物线规律;在750℃,氧化较严重,其连续氧化动力学曲线近似符合抛物线-直线规律。氧化层由金红石型的TiO2氧化物和少量的Al2O3组成。Al2O3能阻止氧的渗入,降低氧化速度。     

Ti2AlNb合金不同温度下的高温氧化行为

研究了Ti₂AlNb合金在不同温度下的高温氧化行为。采用连续氧化增重的方法计算了合金氧化动力学规律;用XRD、SEM、EDS等手段研究氧化后的表面相结构和表面、截面形貌以及元素分布。结果表明,Ti₂AlNb合金在650 ℃和750 ℃下的连续氧化动力学曲线近似符合抛物线规律,而在850 ℃时符合直线规律。氧化层分层现象明显,且都未形成连续致密的Al₂O₃保护层。氧化产物主要为TiO₂,少量的Al₂O₃、Nb₂O₅,以及微量的AlNbO₄、Nb₂TiO₇、AlNb₂。氧化温度越高,分层越明显,富氧层越厚,危害性氧化物越多。     

高温空气介质下T91钢氧化动力学研究

用热分析天平连续称重法和线性回归分析对高温空气介质下T91钢氧化动力学进行研究。结果表明，T91钢在650、675℃时的水蒸气氧化动力学遵守三次抛物线规律；在700℃和750℃时遵守双直线规律。     

T91钢高温水蒸气氧化动力学研究

利用热分析天平连续称重法和线性回归分析,对T91钢高温水蒸气氧化动力学进行了研究。结果表明,T91钢在550℃、600℃和650℃时的水蒸气氧化动力学遵守y^2=kt＋c二次抛物线规律;在700℃和750℃时遵守y=kt＋c的双直线规律。     

铁基高温金恒温氧化行为研究

采用OM,XRD及SEM/EDX研究了铁基高温合金GH 1140的高温静态空气氧化行为,得到了该合金的氧化动力学曲线、氧化膜形貌及其相组成,评价了合金的抗氧化性能并分析了其氧化机理.结果表明:铁基高温合金GH1140在750～900℃时氧化动力学遵循抛物线规律,无氧化膜剥落;在950℃氧化时氧化动力学近似遵从直线规律,且有少量氧化膜剥落;合金氧化过程中有内氧化现象发生,生成的氧化膜以Cr2O3为主;该合金可满足850℃以下高温使用要求.     

一种铁基多元合金堆焊层的高温氧化动力学

运用静态等温氧化法测定了铁基多元合金堆焊层在650～750℃的氧化动力学曲线,并计算了氧化激活能.结果表明;该堆焊层的氧化动力学曲线近似呈抛物线规律,氧化激活能为349.61KJ/moi.在650℃和750℃氧化40h,平均氧化速率分别为1.598x10-5g/(cm2·h)和2.025x10-5g/(cm2·h).     

BT25Y钛合金在600 ℃—800 ℃的高温氧化行为研究

研究了BT25Y钛合金在600 ℃、700 ℃和800 ℃下的高温氧化行为。采用连续氧化增重法,并结合氧化速度常数、氧化活度等理论计算了合金的氧化动力学和热力学规律;利用XRD、SEM和EDS等表征方法研究了氧化膜的相结构和表面、截面形貌及元素分布。结果表明：BT25Y钛合金在600 ℃和700 ℃均有较好的抗氧化性能,其连续氧化动力学曲线符合抛物线规律,氧化层由细小TiO₂和Al₂O₃组成,氧化膜可有效阻止氧渗入基体,降低氧化速度;BT25Y钛合金在800 ℃氧化严重,其连续氧化动力学曲线近似符合直线规律,氧化层由Al₂O₃层和TiO₂层交替组成,氧化膜疏松多孔,不能有效阻挡氧向基体一侧的扩散。     

蒸汽量对T91钢高温氧化动力学的影响

利用热分析天平连续称重法对T91钢的高温蒸气氧化动力学进行研究。结果发现:不同蒸汽量时,T91钢在550～600℃的氧化动力学曲线的抛物线规律不变,腐蚀量的差异可忽略;650～680℃的氧化动力学曲线在氧化初期完全吻合,氧化进入慢速阶段后,蒸汽量大时曲线仍遵守抛物线规律,蒸汽量小到200 mL.h-1左右时遵守直线规律;750℃的慢速氧化阶段动力学曲线均为直线规律,此时氧化量随蒸汽量的增加而增加。另外,T91钢在空气中的抗氧化性比在蒸汽中的好。     

金属型铸造Fe3Al合金的高温抗氧化行为

采用静态增重法测定了中频感应炉熔炼、金属型冷却制备的Fe3Al合金在700、850、1000℃的高温氧化行为,700、850℃时合金的氧化动力学曲线基本符合抛物线规律,1000℃的则不符合;合金在氧化过程中表现为完全抗氧化级.X射线衍射、扫描电镜和能谱分析表明,700℃×125h的氧化膜主要由FeAl2O4、Cr2O3和少量的Al2O3组成;850、1000℃时氧化膜分为两层,内层主要由FeAl2O4和Fe2O3组成,表层为Al2O3,在实验时间内Al2O3氧化膜没有完全覆盖内层氧化膜;随着氧化温度的升高,氧化时间的延长,合金表层的Al2O3氧化膜将由θ-Al2O3向α-Al2O3转变.     

一种镍基高温合金在850℃和950℃的氧化行为

利用热重分析法及x射线衍射（XRD）、扫描电镜（SEM／EDX）等手段，研究一种镍基高温合金在850℃和950℃的高温氧化行为．结果表明，氧化动力学曲线遵循抛物线规律，随着氧化时间的延长，氧化增重变得缓慢．在850℃和950℃时氧化膜由三层组成，外层为复杂氧化物和尖晶石化合物等，中间过渡层和内氧化层均为Al2O3氧化过...     

Cyclic Oxidation Behavior of the Ti–6Al–4V Alloy

The cyclic oxidation behavior of the Ti–6Al–4V alloy has been studied under heating and cooling conditions within a temperature range from 550 to 850 °C in air for up to 12 cycles. The mass changes, phase, surface morphologies, cross-sectional morphologies and element distribution of the oxide scales after cyclic oxidation were investigated using electronic microbalance, X-ray diffractometry, scanning electron microscopy and energy dispersive spectroscopy. The results show that the rate of oxidation was close to zero at 550 °C, obeyed parabolic and linear law at 650 and 850 °C, respectively, while at 750 °C, parabolic—linear law dominated. The double oxide scales formed on surface of the Ti–6Al–4V alloy consisted of an inner layer of TiO₂ and an outer layer of Al₂O₃, and the thickness of oxide scales increased with an increasing oxidation temperature. At 750 and 850 °C, the cyclic oxidation resistance deteriorated owing to the formation of voids, cracks and the spallation of the oxide scales.     

低氧分压下NiTi记忆合金氧化行为的研究

本文研究了NiTi形状记忆合金在H₂-H₂O气氛下400-700 °C的氧化行为。合金的氧化过程遵循立方规律,氧化激活能127.52 kJ/mol。氧化显著降低了试样表面的Ni含量。400 °C氧化的试样,其表面形貌与其他试样不同,并且氧化膜较薄,截面结构无法用SEM分析。500 °C、600 °C、700 °C氧化的试样,表面有两种形貌的氧化物,一种是颗粒状氧化物,另一种是晶须状氧化物。截面分析表明,氧化膜分为两层,上层由TiO₂构成,下层由Ni₃Ti构成,两层界面处有孔洞生成。     

The Isothermal and Cyclic Oxidation Behavior of a Titanium Aluminide Alloy at Elevated Temperature

The isothermal and cyclic oxidation behavior of Ti-47Al-2Mn-2Nb with 0.8 vol.% TiB₂ particle-reinforced alloy was investigated in air between 700 and 1000 °C. In the study, the kinetics of isothermal and cyclic oxidation were performed by using a continuous thermogravimetric method which permits mass change measurement under oxidation conditions. The oxide scales and substrates were characterized by scanning electron microscopy with energy-dispersive x-ray analysis and x-ray diffraction. At 700 and 800 °C, the alloy showed an excellent oxidation resistance under isothermal and cyclic conditions. After exposure to air above 800 °C, the outer scale of the alloy was dominated by a fast-growing TiO₂ layer. Under the coarse-grained TiO₂ layer was the Al₂O₃-rich scale, which was fine-grained. At 900 and 1000 °C, the extent of oxidation increased clearly. The oxidation rate follows a parabolic law at 700 and 800 °C. However, the alloy, upon isothermal oxidation at 900 °C, can be divided into several stages. During the cyclic oxidation at 900 and 1000 °C, partial scale spallation takes place, leading to a stepwise mass change.     

Cyclic Oxidation Behavior of IN 718 Superalloy in Air at High Temperatures

Ni-base superalloy IN 718 was cyclically oxidized in laboratory air at temperatures ranging from 750 to 950 °C for up to 12 cycles (14 h/cycle). The kinetic behaviour as well as the surface morphology, and the oxide phases of the scales were characterized by means of weight gain measurements, cyclic oxidation kinetics, scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) analysis techniques. The results showed that as the oxidation temperature increased, the oxidation rate, the external scale thickness, and internal oxidation zone increased. It was suggested that the oxidation rate was controlled by the diffusion of substrate elements in the alloy and the inward diffusion of oxygen through the oxide scale. The oxidation kinetics followed a sub-parabolic rate law and, the activation energy of oxidation was 249 ± 20 kJ mol^?1. The scaling process was controlled mainly by the diffusion of chromium, titanium, manganese, and oxygen ions through the chromia scale. IN 718 showed low weight gain and very slow reaction rates of substrate elements at 750 °C. At 850 °C, a continuous and very thin oxide scale was formed. At 950 °C, XRD and EDS-elemental mapping analysis revealed that a complex oxide scale had formed. It consisted of an outermost layer of TiO₂?CMnCr₂O₄ spinels, inner layer of Cr₂O₃, and the inner most layer composed of Ni₃Nb enriched with Nb, Ti and Al oxides underneath the chromia layer. The oxide scale at this temperature seemed to be thicker layer, significant spallation and volatilization had apparently occurred, and greater internal corrosion was identified. The doping effect of titanium was observed, where it was found to be diffused through the chromia scale to form TiO₂ at the oxide-gas interface as well as internally and at the oxide alloy interface. The amount of rutile (TiO₂) at the oxide surface increased with temperature. In view of Mn contents in the alloy, the manganese?Cchromium spinel oxide was inferred to have played an important role in cyclic oxidation behaviour of IN 718, where the change in oxidation kinetic was noted. The Al contents would cause internal Al-rich oxide formation at grain boundaries.     

Si对625合金激光熔覆层高温氧化特性的影响

利用循环氧化法,研究了不同Si含量（0%,1%,3%,质量分数）的625合金熔覆层在700、800、900 ℃下氧化144 h后的高温氧化行为。用XRD分析了氧化物相。通过SEM/EDS研究了氧化物表面和截面的形貌、元素组成和氧化膜的厚度。结果表明,不同温度下试样的氧化动力学都保持抛物线规律,随着温度的升高,氧化增重逐渐增加。通过观察,在900 ℃时,0% Si含量的625合金熔覆层出现了氧化膜大面积剥落的情况,3% Si含量的合金熔覆层氧化膜保持完整。在700 ℃时,随着Si含量增加,氧化膜表面的氧化颗粒尺寸减小且更加致密,同时促进了Cr₂O₃氧化物的生成。在700 ℃下,0 % Si含量的试样出现了大片的内氧化区域;1% Si含量的试样基体部分出现了2处条状的含Ni,Cr,Mo的氧化物相区;而3% Si含量的试样氧化后由于生成了富Si的内氧化层,这阻止了内氧化的发生。外层Cr₂O₃氧化膜和内层SiO₂的联合作用既阻止了O阴离子的渗入也抑制了Fe等金属离子的扩散,提高了合金熔覆层的抗氧化性。     

预氧化温度对GH3128合金抗高温循环氧化性能的影响

采用热重法并结合SEM、EDAX等分析手段,研究了预氧化温度对GH3128合金抗高温(1100℃)循环氧化性能的影响。结果表明:在适当温度下进行预氧化处理可有效提高合金的抗高温循环氧化性能。GH3128合金经预氧化处理后抗高温循环氧化性能的优劣主要取决于两种因素的综合作用,其一是合金表面元素Cr的选择性氧化,形成致密均匀的保护性预氧化膜,提高合金抗高温循环氧化性能;其二是合金中元素Ti、Cr的晶界偏析加剧,加速晶界氧化并导致显微裂纹等缺陷产生,降低合金的抗高温循环氧化性能。900℃预氧化处理的GH3128合金试样具有最佳的抗高温循环氧化性能,该温度下预氧化膜形成较好且合金元素Ti、Cr的晶界偏析作用相对较弱。     

两种铸造镍基合金的高温氧化行为

利用热重分析法、XRD和SEM (EDS)对比研究了700℃超超临界发电机组用K317和K325铸造合金在900和1000℃大气环境下氧化行为。结果表明,K317的氧化性能要优于K325。在900℃氧化时,2种合金的氧化增重遵循抛物线规律,而在1000℃氧化时,氧化增重均分段遵循抛物线规律。K317的氧化膜分3层,外层是NiO、TiO_2和NiCr_2O_4,中间层是致密的Cr_2O_3,内层是内氧化产物Al_2O_3。而K325的氧化膜分2层,外层是NiO, NiCr_2O_4和Nb_2O_5,内层是致密的Cr_2O_3和嵌入的Nb_2O_5颗粒,没有内氧化现象发生。在1000℃氧化时,K325中的Mo严重被氧化形成挥发性MoO_3;同时氧化膜发生了局部剥落现象,氧化膜的附着性相对较差。     

Oxidation Behavior of Tribaloy T-800 Alloy at 800 and 1,000 °C

The oxidation behavior of Co-based Tribaloy T-800 alloy has been studied isothermally in air at 800 and 1,000 °C, respectively. The results showed that the oxidation mechanism was dependent on the exposure temperature. The oxidation of the alloy followed subparabolic oxidation kinetics at 800 °C. The oxide scale at this temperature exhibited a multi-layered structure including an outer layer of Co oxide, a layer composed of complex oxide and spinel, a nonuniform Mo-rich oxide layer, an intermediate mixed oxides layer and an internal attacked layer with different protrusions into Laves phase. During 1,000 °C exposure, it followed linear kinetics. The oxidation rendered a relatively uniform external Cr-rich oxide layer coupled with a thin layer of spinel on the top surface and voids at local scale/alloy interface and intergranular region together with internal Si oxide at 1,000 °C.     

Cyclic oxidation behavior of Ni3Al-7.8% Cr-1.3% Zr-0.8% Mo-0.025% B between 900 and 1100°C

A Ni₃Al-based alloy, the composition of which was Ni-16.0% Al-7.8% Cr-1.3% Zr-0.8% Mo-0.025%B, was cyclically oxidized in the temperature range of 900 to 1100°C in air for up to 500 hr. The alloy displayed good cyclic oxidation resistance up to 1000°C, with little scale spallation. It, however, lost cyclic oxidation resistance during oxidation at 1100°C after about 200 hr, displaying large weight losses due to serious scale spallation. NiO, α-Al₂O₃, NiAl₂O₄ and ZrO₂ were formed. The oxide scales consisted primarily of an outer Ni-rich layer which was prone to spallation, and (Al, Cr, Zr, Mo, Ni)-containing internal oxides which were adherent due mainly to the formation of (Al₂O₃, ZrO₂)-containing oxides that keyed the oxide scale to the matrix alloy.     

ZrB₂含量对Nb-Mo-ZrB₂复合材料氧化行为的影响

利用热压烧结法,在2400℃烧结温度下,制备了NbMo固溶体（此后记作(Nb,Mo)ss）基陶瓷颗粒增强复合材料。其中,ZrB2陶瓷增强相的体积分数分别为15%,30%,45%和60%。本文研究了在800℃,1000℃和1200℃下,ZrB2含量对复合材料抗氧化性和氧化产物演变的作用。试验结果表明,氧化温度和ZrB2含量均对复合材料的氧化行为有影响。从氧化速率常数角度讲,ZrB2-(Nb,Mo)ss复合材料的抗氧化性随ZrB2含量的增加而提高,随氧化温度的提高而降低。800℃-1000℃的氧化产物中含有膜状Nb2Zr6O17相,能作为屏障阻止氧气向基体扩散,因此在800℃-1000℃时,复合材料氧化速率较低。然而,在1200℃氧化时未发现Nb2Zr6O17相,MoO3的剧烈挥发和ZrO2的体积效应破坏了Nb2Zr6O17保护层,导致了氧化层严重剥落,材料的抗氧化性极差。综上,本文结合观察到的氧化产物形貌,详细阐述了不同ZrB2含量的复合材料在不同温度下的抗氧化机制。