复杂精密铸件整体式陶瓷铸型间接自由成形工艺

将光固化成形技术和凝胶注模成型技术结合在一起,提出了一种面向复杂精密铸件整体式陶瓷铸型间接自由成形新工艺。讨论了水基陶瓷浆料制备、光固化树脂原型工艺系统设计策略及其热解工艺、陶瓷坯体烧结等问题,并以空心涡轮叶片为实例,证实了新工艺的可行性和有效性。     

提高空心叶片铸型精度的光固化原型内腔结构设计方法

在空心涡轮叶片型芯型壳一体化陶瓷铸型制备过程中,对光固化叶片原型进行整体式内腔结构设计,可显著降低原型烧失过程中铸型的热应力,避免型壳开裂。但在大尺寸叶片铸型的凝胶注模成形过程中,叶片原型榫根部位因刚度偏低,在陶瓷浆料静压力作用下会变形,导致铸型精度较差。为此,提出了一种原型分区域内腔结构设计方法,并基于叶片原型静压力结构刚度-铸型热结构强度有限元模拟,确定了叶身和榫根部位分别采用0.7 mm和0.9 mm的内腔结构尺寸。采用工业CT及逆向精度分析比较了分区域内腔结构设计前后铸型的精度变化,结果表明:分区域内腔结构设计方法降低了凝胶注模过程中原型榫根部分的静压力变形,有效改善了铸型的整体精度,避免了脱脂过程中铸型开裂,可制备出精度高、结构完整的大尺寸叶片陶瓷铸型。     

某型舰船燃气轮机涡轮二级导向叶片精铸技术

介绍了某型舰船燃气轮机复杂三联涡轮导向叶片铸件的研制过程与方法,获得了三联复杂导向叶片陶瓷型芯、蜡模和型壳制备、真空熔炼浇注工艺。重点分析了该导向叶片产生缺陷的原因,并提出了解决措施。     

复杂结构空心高压涡轮导向叶片精密铸造工艺

对双联复杂结构空心高压涡轮叶片的精密铸造工艺进行了研究。结果表明,采用硅基陶瓷型芯为主芯并组合石英管,使制备空心叶片铸造用陶瓷型芯工艺过程明显简单化,提高了陶瓷型芯的成品率。采用该型芯成功制备了合格的双联空心高压涡轮叶片。     

复杂空心定向涡轮叶片高强度型芯技术研究

针对复杂空心定向涡轮叶片精密铸造技术需求,在前期研究基础上,研究了陶瓷粉料级配技术、型芯成型工艺、型芯焙烧工艺、型芯低温强化工艺,制备出满足高推重比发动机空心涡轮叶片浇注要求的陶瓷型芯材料。该材料应用后,某型航空发动机高压涡轮定向空心无余量工作叶片合格率达60%以上,解决了航空发动机定向空心叶片精密铸造行业技术瓶颈。     

燃气轮机涡轮叶片制造工艺现状及发展方向

航空发动机和燃气轮机,被誉为工业"皇冠上的明珠",其涡轮叶片的制造工艺是典型的高科技、高附加值技术.本文概括阐述了近年来铸造涡轮叶片材料和构型的发展现状及未来发展方向,结合现阶段产品介绍了涡轮叶片的制造工艺特点现状,归纳论述了涡轮叶片制造工艺难点,并对涡轮叶片新材料的发展和制造工艺革新进行了展望.     

重型燃机涡轮叶片精铸工艺研究

浇不足、疏松和夹渣等缺陷是铸件浇注时常出现的问题。针对这一问题,以某重型燃机Ⅰ级涡轮叶片无余量精铸工艺作为研究对象,介绍了陶瓷型芯制备与烧结工艺、蜡模与组合方案设计、陶瓷型壳制备工艺和铸件浇注工艺、铸件脱芯工艺等几个关键方面,较好地解决了此类问题。在此基础上,制备出了符合设计要求的合格叶片铸件,并通过了试车考核。     

基于光固化成形的快速熔模铸造组树方法

介绍了基于光固化(SL)成形的快速熔模铸造的组树工艺。通过3D打印制作薄壁空心蜂窝结构的光固化树脂原型代替传统蜡型进行熔模铸造,内浇道设置在树脂原型上,采用传统的蜡浇注系统。这种工艺方法降低了快速熔模铸造的生产成本、提高了组树的连接可靠性,有利于连接挂具实现标准化作业,同时也避免了焙烧过程中型壳的开裂现象。     

蜡模误差与叶片精度控制技术研究进展

镍基高温合金涡轮叶片作为航空发动机、燃气轮机的关键热端部件,主要采用熔模铸造制备。介绍了熔模铸件精度的内涵,阐述了精确控形对于叶片性能提升的重要意义,分析了镍基高温合金涡轮叶片铸造用蜡模制备过程中误差形成的影响因素。总结了近年发展起来的叶片尺寸精度控制技术研究成果,并对其发展趋势进行了展望。     

数值模拟技术在制备燃气轮机叶片中的应用

从单晶叶片的选晶过程、HRS定向凝固工艺制备航空叶片及LMC工艺制备重型燃气轮机叶片3方面,简要介绍了数值模拟技术的研究进展。描述了数理模型的建立,对比分析了两种不同的定向凝固工艺的优缺点。螺旋选晶器的设计对单晶叶片的制备影响较大,其设计失效可能会导致选晶效率差,出现杂晶缺陷等。通过对航空叶片温度场及微观组织的模拟,结合试验研究,优化了工艺,成功制备出单晶叶片。重型燃气轮机叶片制备更为复杂,通过数值模拟缩短了研发周期,节约了成本。     

Porous Ceramic Coating for Transpiration Cooling of Gas Turbine Blade

A transpiration cooling system for gas turbine applications has significant benefit for reducing the amount of cooling air and increasing cooling efficiency. In this paper, the porous ceramic coating, which can infiltrate cooling gas, is developed with plasma spraying process, and the properties of the porous coating material such as permeability of cooling gas, thermal conductivity, and adhesion strength are examined. The mixture of 8 wt.% yttria-stabilized zirconia and polyester powders was employed as the coating material, in order to deposit the porous ceramic coating onto Ni-based super alloy substrate. It was shown that the porous ceramic coating has superior permeability for cooling gas. The adhesion strength of the porous coating was low only 20% compared with the thermal barrier coating utilized in current gas turbine blades. Simulation test of hot gas flow around the gas turbine blade verified remarkable reduction of the coating surface temperature by the transpiration cooling mechanism. It was concluded that the transpiration cooling system for the gas turbine could be achieved using the porous ceramic coating developed in this study.     

Rapid fabrication of alumina-based ceramic cores for gas turbine blades by stereolithography and gelcasting

Injection moulding is accepted as one of the most important methods for shaping complex ceramic cores, which are used to form intricate internal cooling passages of gas turbine blades. But the relatively long lead time and high costs involved in the fabrication of hard tooling render it uneconomical for new products development and low-volume production. In the study, a rapid prototyping process is developed to fabricate complex-shaped alumina-based ceramic core by combining stereolithography (SL) with gelcasting. SL is utilized to fabricate an integral sacrificial resin mold, and gelcasting is utilized to form a wet ceramic core green body through polymerization of aqueous ceramic slurry. The freeze-drying process is adopted to treat the wet green body surrounded by the resin mold, the drying shrinkage is decreased, and the generation of crack can be prevented. The sintering shrinkage of ceramic core is controlled by adding magnesium oxide power and developing a novel sintering process. After the resin mold is burnt out, the complex-shaped alumina-based ceramic core is obtained.     

Corrosion-Resistant High-Temperature Alloys for Large Single-Crystal Turbine Blades

Corrosion-resistant castable high-temperature alloys with properties close to those of alloys with directed structure used for casting vanes of aircraft gas turbine engines and the process of casting of large single-crystal turbine blades of stationary gas turbine units are described. These alloys and the casting process are used to develop a new generation of gas turbine engines and units.     

EB-PVD technology in the gas turbine industry: Present and future

Metal coatings of MCrAlY-type and ceramic thermal barrier coatings on blades and vanes are typical examples of electron-beam physical vapor deposition applications in the gas turbine industry. It is most probable that the gradient thermal barrier coatings will become widely accepted in two to three years. This article reviews current technology in the gas turbine industry and describes some of the possible future aspects.     

涡轮叶片X射线黑白线显示缺陷的工艺控制

涡轮叶片在X射线无损检测时,X射线底片上存在黑白线显示。运用视频显微镜、光学显微镜对叶片黑白线显示部位的表面形貌和显微组织进行了观察分析。结果表明,黑白线显示是由于陶瓷型芯表面错位或微裂纹,使得叶片内腔表面存在具有一定高差的台阶。而陶瓷型芯表面形成错位或微裂纹主要与型芯表面质量和材料高温强度有关。通过控制陶瓷型芯材料纯度和粒度,选择合适的工业氧化铝填料以及加强压芯工艺参数和修芯工艺过程控制,提高型芯表面质量和高温强度,可明显减少甚至消除X射线黑白线显示。     

定向凝固过程中型芯、型壳温度场数值模拟

以空心涡轮叶片作为典型件，开展了定向凝固过程中叶片、陶瓷型芯和陶瓷型壳温度场的数值模拟，分析了陶瓷在定向凝固过程中的膨胀特点，对空心叶片铸造过程中陶瓷型芯的定位进行了设计。     

PVD TBC experience on GE aircraft engines

The higher performance levels of modern gas turbine engines present significant challenges in the reli-ability of materials in the turbine. The increased engine temperatures required to achieve the higher per-formance levels reduce the strength of the materials used in the turbine sections of the engine. Various forms of thermal barrier coatings have been used for many years to increase the reliability of gas turbine engine components. Recent experience with the physical vapor deposition process using ceramic material has demonstrated success in extending the service life of turbine blades and nozzles. Engine test results of turbine components with a 125 μm (0.005 in.) PVD TBC have demonstrated component operating tem-peratures of 56 to 83 °C (100 to 150 °F) lower than non-PVD TBC components. Engine testing has also revealed that TBCs are susceptible to high angle particle impact damage. Sand particles and other engine debris impact the TBC surface at the leading edge of airfoils and fracture the PVD columns. As the impacting continues, the TBC erodes in local areas. Analysis of the eroded areas has shown a slight increase in temperature over a fully coated area ; however, a significant temperature reduc-tion was realized over an airfoil without TBC.     

氧化铝基陶瓷型芯溶失性的研究进展

介绍了涡轮空心叶片用铝基陶瓷型芯的应用背景,探讨了铝基陶瓷型芯强化及溶失性能的重要意义。阐述了造型材料、成孔剂、脱芯方法对氧化铝基陶瓷型芯溶失性能增强的研究现状,并展望了铝基陶瓷型芯未来发展面临的挑战。     

定向凝固过程中型芯型壳温度场数值模拟

以空心涡轮叶片作为典型件,开展了定向凝固过程中叶片、陶瓷型芯和陶瓷型壳温度场的数值模拟研究,分析了陶瓷在定向凝固过程中的膨胀特点,对空心叶片铸造过程中陶瓷型芯的定位进行了设计。     

Current status of thermal barrier coatings — An overview

The science and technology of thermal barrier coatings has advanced considerably since reports of the first test on turbine blades in a research engine in 1976. Today thermal barrier coatings are flying in revenue service in a low risk location within the turbine section of certain gas turbine engines. The state-of-the-art coating system for gas turbine applications is currently a plasma-sprayed ZrO₂-(6%–8%) Y₂O₃ ceramic layer over an MCrAlY (M ≡ Ni, Co or NiCo) bond coat layer plasma sprayed at low pressure.Although the potential for meeting current and short-term goals is high, longer-range goals may not be attainable with current coating concepts. These longer-range goals will involve high risk designs where coating loss could lead directly to component loss. Several steps must be taken to help meet these goals. Improved understanding of coating failure mechanisms is required. Models are needed to predict lifetimes. Process automation and quality control procedures must be instituted. Finally, new concepts in plasma-sprayed coatings must be developed and alternatives to the plasma- spraying process may be required.The current status of thermal barrier coatings and prospects for future progress in the above areas are summarized.