火箭发动机用合金GH202和GH586燃烧事故分析

对GH202、GH586合金部件在高温富氧工况下极短时间内就发生燃烧事故的原因进行了分析。结果表明：合金燃烧的主要原因是环境温度超过了合金的燃烧温度门槛值，而并非材料自身的问题；同时，对如何提高合金的抗燃烧性能及减少燃烧事故提出了建议和措施。     

高温合金GH4169与GH4202在富氧气氛中的燃烧行为

采用富氧燃烧实验方法,通过光学显微镜、扫描电子显微镜和能谱仪等手段对GH4169和GH4202高温合金燃烧试样进行分析,建立合金燃烧质量、热量和氧传输模型,探究两种合金的富氧燃烧机理并提出提高新型高温合金抗燃烧性能的措施.结果表明:GH4202与GH4169合金在富氧条件下均发生燃烧,GH4202抗燃烧性能优于GH4169;两种合金以液相进行燃烧,在合金燃烧前沿存在由未完全燃烧的金属颗粒和氧化物组成"燃烧层",燃烧层中合金元素的燃烧行为是决定合金整体燃烧的关键性因素;合金元素在燃烧前沿呈现"选择性燃烧"规律,Nb、Ti、Al、Cr等元素易于与氧发生燃烧,Ni滞后燃烧且燃烧热低,起到良好的抗燃烧作用.      

高温合金GH4065A的恒温静态氧化行为

研究了新型镍基高温合金GH4065A在650～750℃的静态氧化行为,基于对氧化动力学与氧化产物的分析,探讨了合金的氧化机制.结果表明:采用平均氧化增重速率指标评定GH4065A合金在650～750℃温度范围内均为完全抗氧化级别,试验条件下合金的抗氧化能力与典型涡轮盘材料FGH96、GH4720Li合金相当;合金的氧化产物主要为内层富铝的氧化物颗粒、外侧富铬的氧化物膜及表面金红石型TiO2颗粒,TiO2颗粒在氧化温度超过700℃后开始生成;合金的氧化动力学遵循抛物线型规律,受钛离子与铬离子穿过氧化膜的扩散过程共同控制.     

GH648合金高温抗氧化性能的研究

GH648是一种时效硬化型镍基高温合金,主要用作航空发动机的启动机900℃以下的抗氧化承力件.在高温下,该合金不仅要有较高的强度,而且还要有较好的抗氧化性能.为此,本文探讨了GH648合金高温氧化机理并简单分析了C元素对合金抗氧化性能的影响.结果表明,GH648合金在空气中氧化时,其氧化膜主要为Cr2O3,该合金的氧化是以Cr在Cr2O3中的扩散为控制因素的;合金在低于900℃的空气中氧化时属于完全抗氧化级.随C含量的升高,合金的抗氧化性能降低.     

NiCrAlY涂层对镍基单晶高温合金氧化性能的影响

采用磁控溅射方法在镍基单晶高温合金基体上沉积NiCrAlY微晶涂层.用热重分析(TGA)、X射线衍射(XRD)、扫描电镜(SEM)等手段研究了镍基单晶高温合金及其NiCrAlY微晶涂层在900～1100℃静止空气中的氧化行为.结果表明,镍基单晶合金及其微晶涂层在900℃表现出相同的增重规律,即经初期快速增重后,两者的氧化增重都变得非常平缓;在1000℃,单晶合金的氧化膜不断剥落,使动力学曲线上下起伏,而微晶涂层经初期快速增重后,动力学曲线趋于平缓;在1100℃,单晶合金由于氧化增重远大于氧化膜剥落所造成的失重,使氧化动力学曲线在整个氧化过程中都呈迅速增长趋势,而微晶涂层的氧化动力学基本符合抛物线规律.单晶合金表面形成含Al2O3、Cr2O3、NiO、CrTaO4和Ni(Al,Cr)2O4尖晶石等的复合氧化膜.施加NiCrAlY微晶涂层后,镍基单晶合金表面形成连续、致密且结合良好的单一氧化物Al2O3,使合金的抗氧化性能明显提高.     

新型低Cr镍基合金GH3535高温氧化行为

采用静态增重法,研究了GH3535合金在700~980℃温度范围内空气中的恒温氧化行为。利用扫描电镜(SEM)、X射线衍射仪(XRD)和电子探针(EPMA)分析了GH3535合金高温氧化膜表面与截面形貌、表面氧化膜的相组成以及氧化层中元素分布情况。结果表明GH3535合金在700℃氧化后表面氧化膜无明显剥落,氧化动力学曲线遵循立方规律,氧化膜厚度4μm左右。870和980℃时氧化物出现剥落,870℃下无内氧化现象发生。GH3535合金在3个温度下的氧化速率分别为0.064,0.073和0.200 g·(m2·h)-1,根据氧化等级评定,700和870℃时属于完全抗氧化等级;而980℃时GH3535合金转变为抗氧化等级。GH3535合金700℃时氧化膜主要组成是外层Ni O和Ni Fe2O4等复合氧化物,中间层是Cr2O3,Ni Cr2O4,Mo O2和Ni Mn2O4等氧化物;870℃氧化膜分层同700℃一致,但外层Ni O含量降低,内层Cr2O3厚度增加;980℃时外层Ni O已剥落掉,露出内部Cr2O3等氧化层,并出现了Al2O3内氧化层。     

Ce对铁硅合金高温氧化行为的影响

通过光学显微镜、热重分析、X射线衍射和扫描电镜等研究了Ce对Fe-Si合金在900℃、0.1 MPa纯氧气中高温氧化行为的影响。结果表明,随着Ce含量的增加,Fe-Si合金及其氧化膜的晶粒尺寸明显降低,晶界浓度增加,这促进了合金元素和氧的"短路扩散"。在此过程中,"短路扩散"对合金氧化抗力产生的正影响大于负影响,添加Ce明显提高了Fe-Si合金的氧化抗力。过量的Ce优先参与氧化反应导致了Fe-3Si-5.0Ce较Fe-3Si-0.5Ce合金具有更大的氧化增重。添加Ce改变了合金的氧化机制,氧穿透氧化膜并与富Ce相优先发生氧化反应,产生"钉扎效应",可改善氧化膜的粘附性。     

艾萨炉入炉物料生球的熔炼过程研究

采用TG(热重)-MS(质谱)以及X射线衍射成像等分析实验手段,对艾萨入炉物料生球的高温富氧熔炼过程机理特性进行了系统的研究。结果表明:在以50ml/min通入75%O_(2),升温速度25℃/min的条件下,氧化还原熔炼体系经历了失重→增重→失重的过程,氧化顺序为CuFeS_(2)→Cu_(2)S→CuO·CuSO_(4)→CuSO_(4)→CuO。从MS(质谱)研究结果可知:熔炼过程ZnO、AS_(2)O_(3)、PbO及Bi_(2)O_(3)均在持续挥发,说明Zn、As、Pb、Bi等杂质可通过富氧熔炼定向调控技术手段,将其氧化挥发到烟气中进行综合回收,从而降低产品中的杂质含量。     

GH 4169合金的高温氧化

研究了不同温度和时间条件下,GH4169合金的氧化动力学规律,并且深入地分析了合金元素的作用、氧化机理及合金在氧化条件下形成的氧化层结构及产生的规律.研究结果表明,该合金在氧化气氛条件下不能形成致密的抗氧化保护膜结构,氧化层剥落或蒸发,呈现失重状态.当温度超过800℃时产生加速氧化现象,合金的扩散导致试件表层抗氧化元素贫化.生产中必须严格控制固溶处理温度和时间,否则合金出现严重的表面氧化而报废.此研究对高温合金抗氧化理论与生产实际有重要的参考价值.     

钼合金表面MoSi2涂层氧化行为和氧化机理的研究

采用包埋渗硅法在钼合金表面制备了MoSi2涂层,研究了涂层的氧化行为和抗氧化机理.结果表明,钼合金基体经历30 min高温氧化后,样品表面鼓泡严重,质量失重率在11%左右;在钼合金基体表面形成MoSi2涂层后,抗氧化能力大幅度提高,经过60min的高温氧化后,样品表面完好,质量增重率为0.58%;在高温氧化过程中,Mo...     

Fe-Si-B非晶带材高温氧化行为及回收工艺

??In order to reduce the oxidative burning loss of Fe78Si9B13 amorphous ribbon in the recovery process?? the oxidation behavior of Fe78Si9B13 amorphous ribbon was studied. The results show that the oxidation of Fe78Si9B13 amorphous ribbon at high temperature is related to the heating rate. The oxidation weight gain of Fe78Si9B13 amorphous ribbon at 5 and 10K/min from room temperature to 1223K are 44% and 31% respectively. There is an oxide layer with loose texture and a small amount of microcrack at the interface between the sample and atmosphere by SEM. The oxide layer contains a large amount of Fe2O3 and a little SiO2 by XRD. Oxidation kinetics curve shows that the oxidation weight gain of the samples follows a linear rule within 5hours at 1073 and 1173K?? then a parabolic rule. At 1273K?? however?? it only follows a linear rule?? meanwhile the oxidation speed is very fast?? with the oxidation weight gain reaches 40% in 12min. The oxidation weight gain in the amorphous ribbon recycling process can be reduced through cutting down the furnace gas temperature?? compressing the waste ribbon and unqualified products in the packaging process and blowing argon to reduce the partial pressure of oxygen in the furnace. Thus the slag decreases to 9-10g when 1kg waste ribbon is recovered?? and the Si content of liquid alloy increases to 8. 9%.     

Oxidation of low carbon steel in multicomponent gases: Part II. Reaction mechanisms during reheating

Oxidation behavior of low carbon steel during reheating in an industrial walking-beam steel reheat furnace was investigated. It was observed that scaling (oxidation) rates were reduced by reducing the input air/fuel ratio to the furnace, thereby lowering concentrations of free oxygen in the combustion products from about 3 to 1.5 pct. Laboratory experiments involving isothermal and nonisothermal oxidation were carried out in atmospheres consisting of oxygen, carbon dioxide, water vapor, and nitrogen. A general equation for the prediction of weight gains due to oxidation during reheating, using isothermal oxidation rate constants, was developed. The prediction of weight gains from nonisothermal oxidation conducted in the laboratory was poor, owing to a separation of the scale from the metal substrate which took place at about 900 °C. The predicted weight gains during reheating in the industrial reheat furnace indicated that oxidation rates during reheating were intermediate between linear and parabolic, especially during reheating with high air/fuel ratio. However, the linear mechanism predominated. Laboratory isothermal experiments for oxidation in atmospheres containing free oxygen showed that the magnitude of the linear oxidation rates was determined by the oxygen concentration in the atmosphere. It was concluded that the observed reduction in scaling rates during reheating of low carbon steel in the industrial reheat furnace was a result of the lower free oxygen level in the furnace atmosphere.     

High-Temperature Oxidation Behavior of Two Nickel-Based Superalloys Produced by Metal Injection Molding for Aero Engine Applications

For different high-temperature applications like aero engines or turbochargers, metal injection molding (MIM) of superalloys is an interesting processing alternative. For operation at high temperatures, oxidation behavior of superalloys produced by MIM needs to match the standard of cast or forged material. The oxidation behavior of nickel-based superalloys Inconel 713 and MAR-M247 in the temperature interval from 1073 K to 1373 K (800 °C to 1100 °C) is investigated and compared to cast material. Weight gain is measured discontinuously at different oxidation temperatures and times. Analysis of oxidized samples is done via SEM and EDX-measurements. MIM samples exhibit homogeneous oxide layers with a thickness up to 4 µm. After processing by MIM, Inconel 713 exhibits lower weight gain and thinner oxide layers than MAR-M247.     

2种600℃超临界锅炉用奥氏体钢的高温氧化行为

采用热重法研究了Super304H和HR3C两种奥氏体耐热钢于750℃静态空气中的循环氧化行为。结果表明,Super304H由于氧化膜的大量剥落很快出现失重,其质量随循环周次的增加而线性减小。在循环氧化条件下,Super304H表面形成由外层FeCr_2O_4和内层(Cr,Mn)_2O_3组成的双层氧化膜,2层膜的层间形成大量的空洞,导致FeCr_2O_4在冷却时压应力作用下剥离并进一步剥落。相反地,HR3C的氧化增重遵循抛物线规律,而在300个循环周次后增重呈线性加速的趋势。氧化增重加速的原因在于:HR3C表面形成单层(Cr,Mn)_2O_3膜,膜局部与基体分离并拱起,拱起的氧化膜在冷却过程中开裂,导致膜下方的基体在后续的氧化过程中直接暴露于高温空气并与之发生化学反应形成新鲜的富Cr氧化物。     

On the high-temperature oxidation protection behavior of plasma-sprayed Stellite-6 coatings

High-temperature oxidation resistance of the superalloys can be greatly increased by plasma-sprayed coatings, and this is a growing industry of considerable economic importance. The purpose of these coatings is to form long-lasting oxidation protective scales. In the current investigation, Stellite-6 coatings were deposited on two Ni-base superalloys, Superni 601 and Superni 718, and one Fe-base superalloy, Superfer 800H, by a shrouded plasma spray process. Oxidation studies were conducted on the coated superalloys in air at 900 °C under cyclic conditions for 50 cycles. Each cycle consisted of 1 hour heating followed by 20 minutes of cooling in air. The thermogravimetric technique was used to approximate the kinetics of oxidation. All of the coated superalloys nearly followed the parabolic rate law of oxidation. X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray (SEM/EDAX), and electron probe microanalysis (EPMA) techniques were used to analyze the oxidation products. The Stellite-6 coating was found to be successful in maintaining its continuous surface contact with the superalloy substrates in all cases. The oxide scales formed on the oxidized coated superalloys were found to be intact and spallation free. The main phases analyzed for the coated superalloys were oxides of cobalt and chromium and spinel of cobalt and chromium, which are suggested to be useful for developing oxidation resistance at high temperatures.     

Fe-2.2%Si钢在不同气氛下的高温氧化行为

为了探究硅元素、加热工艺参数(气氛、温度以及时间)对Fe-2.2%Si钢表面氧化铁皮形成过程的复合作用及影响机理,利用热重分析仪(TGA)研究了Fe-2.2%Si钢在600～1 150℃干燥空气和水蒸气条件下的高温氧化行为,利用试验得到的氧化增重数据计算出了氧化速率常数和氧化激活能,并建立了氧化动力学模型。此外,还明确了在2种气氛下氧化铁皮的生长机制与结瘤机理。试验结果表明,在2种不同氧化气氛下得到的氧化增重曲线均符合抛物线规律。当氧化气氛中含有水蒸气时,试验钢的氧化速率提高,氧化激活能降低,导致了试验钢的氧化增重增加。在2种氧化气氛下,试验钢的氧化产物均由氧化铁皮和氧化铁皮与基体界面处的富硅层组成,但在水蒸气下得到的试验钢的富硅层疏松多孔,且氧化铁皮中出现大量的孔洞以及裂纹。其氧化机制主要是氧化铁皮生长过程的生长应力以及水蒸气的存在导致生成的H₂向外扩散,造成氧化铁皮出现大量孔洞和裂纹,为氧化介质的扩散提供了通道,有利于气相物质扩散,进而促进了试验钢的氧化行为。此外,由于在氧化铁皮与基体界面形成的富硅层消耗了基体中的硅元素,导致基体表层出现贫硅区,氧化介质可以通...     

Air embrittlement of a cobalt-base superalloy

The stress-rupture and tensile properties of a cast cobalt base superalloy, MM509, are compared after high temperature exposure in air and vacuum. A loss in tensile ductility after air exposure is observed over the entire temperature range from room temperature to 1000 °C with the effect being most severe at 400 ° to 600 °C. This appears to be related to grain boundary oxygen penetration and is compared and contrasted with similar observations in nickel base alloys. The cobalt base alloy has high intrinsic ductility at high temperatures and, even after air exposure, there is no loss in creep life associated with the embrittlement. It is argued that in this alloy the critical strain for fracture of embrittled grain boundaries is much higher than that for high strength nickel base superalloys.     

The embrittlement of nickel following high temperature air exposure

The embrittlement of three grades of nickel following air exposure at 1000 °C is reported. This embrittlement manifests itself in a dramatic loss in tensile ductility around the 800 °C range, and is accompanied by a transition to intergranular failure. Similar behavior has previously been reported in nickel-base superalloys, but is now shown to be a general property of nickel. Tests in a variety of atmospheres have established that the damaging species is oxygen, and that this can have a profound effect, even when present at very low partial pressures. Grain boundaries are observed to be pinned and recrystallization suppressed after oxygen exposure. This lack of boundary mobility has been used to explain the temperature dependence of the embrittlement observed, and has been related to some of the results seen in superalloys. Finally, a few implications for environment-property interactions are considered.