电子束冷床熔炼TC4合金元素挥发机制研究

建立了TC4合金电子束冷床熔炼过程熔体中各元素饱和蒸气压的数学计算模型,利用该模型计算了TC4合金熔体中各元素的饱和蒸气压及其挥发速率,与实验结果基本一致。计算结果表明,在相同温度下,Al元素的饱和蒸气压最大,是其它两种元素的几百倍,挥发损失也最为严重。随着熔体温度的增加,挥发趋势也增大。V元素的挥发很少,可以忽略。此外,电子束冷床熔炼去除杂质效果显著,熔炼出的铸锭成分符合国家标准。     

钛合金电子束深熔焊钉尖缺陷形成的影响因素

钉尖缺陷是电子束焊接所特有的缺陷,对焊接质量造成严重影响.对于钉尖缺陷的形成机理,目前学术界还没有形成统一的认识.为了对钉尖缺陷形成机理进行研究,采用正交试验法进行了钛合金电子束深熔焊接试验,焊后对每条焊缝进行了X射线探伤,探伤结果显示钉尖缺陷只存在于未熔透焊缝中,钉尖为不规则狭缝状,根部呈圆形.利用光学显微镜和扫描电镜结合能谱分析对钉尖缺陷的形成机理进行了研究.结果表明,电子束脉动是钉尖缺陷产生的直接原因,高饱和蒸气压金属蒸气的存在加剧了钉尖缺陷产生的倾向,是钉尖缺陷产生的重要内在动因.     

Vapor deposition of platinum alloyed nickel aluminide coatings

Platinum-doped NiAl coatings are widely used to increase the oxidation resistance of superalloys. These coatings are usually synthesized by a solid state reaction-diffusion process conducted at high temperature. It requires the chemical vapor deposition of aluminum on a nickel rich superalloy substrate that has been pre-coated with several microns of electrodeposited platinum. Here, we show that an electron beam directed vapor deposition (EB-DVD) technique can be used to deposit well bonded, structurally and chemically homogeneous NiAlPt bond coats of any composition onto superalloy substrates. The approach utilized a high voltage, rapid scan frequency electron beam to independently heat elemental nickel, aluminum and platinum melt pools to create three closely spaced vapor plumes. These vapor plumes were then entrained in an inert gas jet flow, which mixed and directed them to a substrate. By adjusting the electron beam current applied to each elemental source, homogeneous, dense, Pt alloyed β-phase NiAl coatings could be synthesized at substrate temperatures of 1050 °C. The width of the substrate-coating interdiffusion zone was controlled by the deposition temperature and time.     

变焦-临界穿透束流极值法测量电子束流动态焦点——一种焦点测量方法介绍

通过试验研究发现了电子束焊接过程中工件传导电流的传导比均值与输入束流的函数规律，函数的极大值是电子束焊接动态过程工件被穿透的临界状态转变点。利用电子束焊接过程的临界穿透束流特性，讨论了电子束受金属蒸气影响后的焦点状态与漂移空间传输的电子束焦点状态存在不同特性，提出了一种测量电子束焊接过程动态焦点的方法，变焦-临界穿透束流极值焦点测量法。     

钼薄膜制备技术研究

具有体密度的高表面质量金属钼薄膜对材料高压状态方程研究具有十分重要的意义。本文介绍了制备钼薄膜的几种方法,包括:机械轧制、机械研磨抛光、化学气相沉积、电子束蒸发、脉冲激光沉积和磁控溅射。综合比较后认为,采用磁控溅射法制备的钼膜可以基本满足状态方程靶用钼(Mo)薄膜的需要。通过磁控溅射沉积方法可以制备出表面质量高,厚度可达几微米的金属Mo薄膜,其组织结构和密度接近块材而且薄膜表面不易出现硬化、沾污等问题。     

电子束定点焊接304不锈钢熔池流动行为数值模拟

基于电子束焊接过程的传热与受力物理过程分析,建立相应模型,对电子束定点焊接304不锈钢的温度场与流场进行数值模拟,研究电子束焊接熔池流动行为及焊缝成形规律.结果表明,电子束加热阶段,熔池上表面温度梯度达到106 K/m,熔池表面峰值温度高,在沸点温度附近波动,强烈的金属蒸汽反作用力成为熔池流动的主要作用力,促使熔池中心下凹并不断波动,熔池冷却凝固阶段,金属蒸汽反作用力下降,熔池金属表面张力梯度引起的Marangoni对流成为熔池金属流动主要驱动力,促使焊缝表面熔宽增大,熔池凝固后焊缝上表面宽度为1.9 mm,中心处宽度为1.6 mm,下表面宽度为1.8 mm.     

电子束熔炼提纯钨中杂质脱除静态动力学研究

研究了电子束熔炼提纯钨过程中典型杂质的脱除,考察了电子束熔炼提纯钨的可行性,对电子束熔炼过程中的除杂动力学进行了分析,并确定了110、130、250 kW功率条件下杂质Fe、Si、Ti的脱除速率控制机制。结果表明:除Mo外,电子束熔炼对基体钨中各种杂质均有不同程度的脱除,其脱除率与饱和蒸气压差存在对应关系;通过分析并结合电子束熔炼实验,确定了Si、Fe、Ti在110 kW时的传质系数分别为0.21、0.56、0.11×10-4 m/s,在130 kW时的传质系数分别为0.83、3.04、1.78×10-4 m/s,在250 kW时的传质系数分别为0.36、2.37、1.48×10-4 m/s,表明其脱除速率控制机制均为液/气界面中的扩散。     

2219铝合金电子束焊接匙孔演变过程的数值模拟

文中主要借助Fluent软件,基于有限体积离散方法建立了2219铝合金电子束点焊熔池传热、流动和匙孔演变的二维耦合数学模型.在模型中,考虑了表面张力、Marangoni剪切力、流体静压力、金属蒸气反冲压力的作用,并采用VOF(volume of fluid)方法跟踪了匙孔的形成与演变过程.结果表明,反冲压力钻取和涡旋输运的综合作用是匙孔加深的根本原因;沿深度方向热源功率密度的降低会导致前者钻取速度的减小.铝合金的点焊工艺试验表明,数值计算结果与实际吻合较好.     

BSAS环境障涂层抗水蒸汽性及其失效机理

采用电子束物理气相沉积(EB-PVD)和等离子喷涂(PS)两种工艺结合,在Cf/SiC基体上制备出了Si/3Al2O3·2 SiO2+BSAS/BSAS(1-xBaO-xSrO-Al2O3-2SiO2,0≤x≤1)环境障涂层(EBC).其中,Si粘结层采用EB-PVD工艺制备,3 Al2O3·2SiO2+BSAS中间层...     

Assessment of damage accumulation in thermal barrier coatings using a fluorescent dye infiltration technique

Thermal barrier coatings, used extensively on hot section gas turbine engine components, weaken and spall after repeated thermal exposure during normal engine operation. A new technique has been developed, involving the use of vacuum impregnation of the porous ceramic with a mixture of epoxy and fluorescent dye (rhodamine-B) and the ASTM C 633–79 direct pull test, to preserve and reveal incipient damage and accumulated damage prior to spallation in thermal barrier coatings. Excellent definition of damage is provided by the dye in electron beam physical vapor deposited coatings, but the damage is more difficult to distinguish in the highly porous plasma coatings. Image processing is used to quantify the area fraction of debonding. For the electron beam physical vapor deposited yttria-stabilized zirconia coating evaluated, a local area fraction of debonding of up to 20% was observed at 80% of spallation life.     

未来航空发动机热障涂层材料及制备技术

概述了未来航空发动机热障涂层最有前景的新材料、结构和制备工艺。新材料主要有改进型氧化钇稳定的氧化锆、A2B2O7型材料;新结构主要有双陶瓷层;新工艺主要为制备含垂直裂纹的热障涂层的改进大气等离子体喷涂、等离子喷涂-物理气相沉积、悬浮液等离子喷涂、电子束直接气相沉积。这些相互结合,必将促进高性能热障涂层的快速发展和应用,使其在未来航空发动机中发挥重要作用。     

Effect of chemical composition and heat treatment on mechanical characteristics of microlayer composite materials of the Cu-Zr-Y-Mo System in a wide temperature range

The structure, hardness, and characteristics of short-term strength and ductility in the temperature range 20–800°C are determined for microlayer composite materials of the Cu-Zr-Y-Mo system obtained by the method of electron beam evaporation and layer-after-later condensation from a vapor phase depending on the chemical composition and heat treatment. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 18–22, March, 2006.     

离子束表面工程技术的进展*

综述了离子束表面工程技术近期研究进展,重点讨论了等离子体浸没离子注入(PIII)、强流脉冲离子束技术(HIPIB)、等离子体喷涂物理气相沉积(PS-PVD)、电子回旋共振(ECR)等离子体和磁过滤阴极真空弧沉积等表面工程技术;介绍了离子束表面工程在替代传统电镀技术、航空航天材料表面改性、太阳能利用中材料的表面改性、生物医学材料的表面改性等领域的应用。指出了离子束表面工程技术的未来研究方向,即深入研究离子束与材料表面的作用机理,开发高性能结构涂层和功能涂层,发展新的离子束复合表面技术。     

Effects of deposition conditions on composition and thermal cycling life of lanthanum zirconate coatings

Lanthanum zirconate (La₂Zr₂O₇, LZ) coatings were prepared under four different deposition conditions by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, surface and cross-sectional morphology, cyclic oxidation behavior of these coatings were studied. Elemental analysis indicates that the coating composition has partially deviated from the stoichiometry of pyrochlore, and the existence of excess La₂O₃ is also observed. The deviation could be reduced by properly controlling the electron beam current or by changing the ingot composition. Meanwhile, when the electron beam current was 500 - 600 mA, the thermal cycling life of the coating is superior to other coatings.     

Morphology and texture evolution of FeCrAlTi-Y2O3 foil fabricated by EBPVD

An electron beam physical vapor deposition method was used to fabricate freestanding Y₂O₃ dispersive strengthened FeCrAlTi foils for high-temperature applications. The vapor incidence mode was found to have great impact on the morphology and crystallographic orientation of the foils. Under symmetric vapor incidence mode, an out-of-plane < 100> fiber texture was formed. While under asymmetric vapor incidence mode, both out-of-plane preference of < 111> direction and several in-plane preferences were developed. As the deposition proceeded, the extent of in-plane orientation increased, and the preferred out-of-plane orientation increasingly deviated from the surface normal. The vapor incidence mode played a role on the growth rate of < 100> direction and < 110> direction, by which the morphology and crystallographic orientation of grains were modified.     

Vapor pressure and thermochemical properties of ZrCl4 for ZrC coating of coated fuel particles

Vapor pressure of zirconium tetrachloride（ZrCl4）under vacuum and an argon pressure of 1 × 105 Pa was measured. The thermochemical changes of ZrCl4 during evaporation were studied by thermogravimetry-differential thermal analysis（TG-DTA）, X-my diffractometry（XRD）, scanning electron microscopy（SEM） and energy-dispersive X-ray（EDX） analysis. At the same temperature, vapor pressures of ZrCl4 under vacuum and an argon pressure of 1× 10^5 Pa are approximately the same. The vapor pressure exceeds 1 × 10^5 Pa at 340 ℃, which is high enough for ZrC coating of coated fuel particles. ZrCl4 sample is hydrolyzed to some extent to give ZrO2 and HCl, which however, has little influence on vapor pressure of ZrCl4 at high temperature. No ZrCl3 and Cl2 are produced by decomposition of ZrCl4 during evaporation, which is confirmed by thermodynamic calculation.     

TC4钛合金焊接接头中压电子束局部热处理技术

电子束局部热处理技术是对整体热处理的一种有益补充,针对TC4钛合金进行中压电子束局部热处理研究。电子束局部热处理后TC4钛合金接头的组织形态与电子束焊态基本相同,但焊缝区的晶粒组织略有细化,焊缝区显微硬度也得到了改善,电子束局部热处理后焊接接头的拉伸力学性能均高于焊态。优化的电子束局部热处理工艺完全可以使TC4钛合金接头的组织力学性能超过焊态。     

Impurities evaporation from metallurgical-grade silicon in electron beam melting process

The purification of metallurgical-grade silicon (MG-Si) has been investigated during electron beam melting (EBM) process. The results show that the phosphorus, calcium and aluminum contents decrease significantly after melting, and magnesium is partially removed. However, no significant change in content for boron and iron has been found. Langmuir’s equation and Henry law were used to derive the removal effi-ciency for each impurity element. The free surface temperature was estimated by the Hertz-Knudsen-Langmuir equation and silicon’s vapor pressure equation. Good agreement was found between measured and calculated impurities’ removal efficiency for phosphorus, calcium and aluminum, magnesium, boron and iron. The deviation between the two results was also analyzed in depth.     

Plasma Spray-PVD: A New Thermal Spray Process to Deposit Out of the Vapor Phase

Plasma spray-physical vapor deposition (PS-PVD) is a low pressure plasma spray technology recently developed by Sulzer Metco AG (Switzerland). Even though it is a thermal spray process, it can deposit coatings out of the vapor phase. The basis of PS-PVD is the low pressure plasma spraying (LPPS) technology that has been well established in industry for several years. In comparison to conventional vacuum plasma spraying (VPS) or low pressure plasma spraying (LPPS), the new proposed process uses a high energy plasma gun operated at a reduced work pressure of 0.1 kPa (1 mbar). Owing to the high energy plasma and further reduced work pressure, PS-PVD is able to deposit a coating not only by melting the feed stock material which builds up a layer from liquid splats but also by vaporizing the injected material. Therefore, the PS-PVD process fills the gap between the conventional physical vapor deposition (PVD) technologies and standard thermal spray processes. The possibility to vaporize feedstock material and to produce layers out of the vapor phase results in new and unique coating microstructures. The properties of such coatings are superior to those of thermal spray and electron beam-physical vapor deposition (EB-PVD) coatings. In contrast to EB-PVD, PS-PVD incorporates the vaporized coating material into a supersonic plasma plume. Owing to the forced gas stream of the plasma jet, complex shaped parts such as multi-airfoil turbine vanes can be coated with columnar thermal barrier coatings using PS-PVD. Even shadowed areas and areas which are not in the line of sight of the coating source can be coated homogeneously. This article reports on the progress made by Sulzer Metco in developing a thermal spray process to produce coatings out of the vapor phase. Columnar thermal barrier coatings made of Yttria-stabilized Zircona (YSZ) are optimized to serve in a turbine engine. This process includes not only preferable coating properties such as strain tolerance and erosion resistance but also the simultaneous coverage of multiple air foils.     

Numerical analysis of thermal fluid transportation during electron beam welding of 2219 aluminum alloy plate and experimental validation

A three-dimensional mathematical model using volume-of-fluid method is developed to investigate the heat transfer,fluid flow and keyhole dynamics during electron beam welding of 2219 aluminum alloy plate.In the model,an adaptive heat source is employed to simulate the heating process of electron beam.Fluid flow is mainly driven by surface tension,thermo-capillary force,recoil pressure,hydrostatic pressure and thermal buoyancy.The thermal-fluid transport behaviors of welding pool during the drilling and backfilling stages of keyhole and the formation reason of the nail-shaped weld with an arc crater are systematically analyzed.Finally,all calculation results are validated by experiments and show good agreements.