涡轮叶片蠕变损伤的恢复处理研究进展

涡轮叶片延寿是航空发动机亟待解决的关键问题,损伤恢复处理技术是保障发动机长寿命、高可靠性和低成本运行的重要手段。介绍了针对涡轮叶片蠕变损伤的延寿技术研究现状与进展,根据各种延寿方法的特点分析了从简单热处理到恢复热处理和热等静压(HIP)修复的延寿技术发展历程,指出了蠕变损伤修复的一般性原则和HIP修复技术的优点。重点阐述了蠕变空洞在HIP作用下的愈合机理,并介绍了主要的空洞烧结模型。指出了延寿技术研究中存在的问题,给出了在我国开展HIP修复技术研究的建议和思路。     

Complicated hollow turbine blades and surface grain refinement process

The control of grain size in superalloys is critical in the manufacture of gas turbine blades. The aim of the present research is to provide the technology for producing complicated hollow turbine blades with fine surface grains and better comprehensive mechanical properties. By melt superheating treatment and coating the internal surfaces of shell mould using a cobalt aluminate-bearing coating material, the influence of cobalt aluminate as inoculant on the surface grain sizes of turbine blade was studied with addition of cobalt aluminate: 0, 35%, 45% - 65% and 100% respectively. At the same time, the effects of cooling circumstances of the blades on surface grain sizes were also experimented under the same addition of cobalt aluminate. The results showed that the melt superheating treatment plays a significant role in the grain size and carbide morphology; and fine surface grains were obtained when the internal surfaces of shell mould were coated using cobalt aluminate coatings. When the addition of cobalt aluminate in coating is between 45% - 65%, and the melt is poured into preheated shell moulds with fine silica sand as backing sand, the blades satisfied the surface grain size requirement is over 90%. In addition, comparisons of the surface grain size and the mechanical properties were also conducted between home-made and foreign-made blades.     

Influence of service-induced microstructural changes on the aging kinetics of rejuvenated Ni-based superalloy gas turbine blades

Rejuvenation of Ni-based superalloy gas turbine blades is widely and successfully employed in order to restore the material microstructure and properties after service at high temperature and stresses. Application of hot isostatic pressing (HIP) and re-heat treatment can restore even a severely overaged blade microstructure to practically “as-new” condition. However, certain service-induced microstructural changes might affect an alloy’s behavior after the rejuvenated blades are returned to service. It was found that advanced service-induced decomposition of primary MC carbides, and the consequent changes of the γ-matrix chemical composition during the rejuvenation, can cause a considerable acceleration of the aging process in the next service cycle. The paper will discuss the influence of the previous microstructural deterioration on the aging kinetics of rejuvenated gas turbine blades made from IN-738 and conventionally cast GTD-111 alloys.     

粉末冶金TiAl合金排气门的研制

利用元素粉末冶金方法制备了TiAl合金排气阀。为提高排气门杆部的致密度、均匀度 ,设计了特有的径向热压工艺 ,并从理论上分析了与该工艺相关的压坯密度、致密化和应力变化规律。制备出高径比为 10 .7,密度为 3.79g/cm3 的粉末冶金TiAl合金汽车发动机排气门     

Evaluation of service-induced damage and restoration of cast turbine blades

Conventionally cast turbine blades of Inconel 713C, from a military gas turbine aircraft engine, have been investigated with regard to service-induced microstructural damage and residual creep life time. For cast turbine blades, service life is defined by statistical values. The statistical methods can prove to be uneconomical, because safe limits must be stated with regard to the statistical probability that some blades will have higher damage than normal. An alternative approach is to determine the service-induced microstructural damage on each blade, or a representative number of blades, to better optimize blade us-age. Ways to use service-induced γ rafting and void formation as quantified microstructural damage pa-rameters in a service lifetime prediction model are suggested. The damage parameters were quantified, in blades with different service exposure levels, and correlated to remaining creep life evaluated from creep test specimens taken from different positions of serviced blades. Results from tests with different rejuvenation treatments, including hot isostatic pressing andJor heat treatment, are discussed briefly.     

浅论航空发动机涡轮转子叶片再生热处理的主要技术路径

涡轮转子叶片是航空发动机的关键件之一,长期在非常苛刻的环境下工作,当服役到一定寿命时,其组织和性能会发生退化。如能及时对其进行恢复,涡轮转子叶片的使用寿命将会大幅度延长。本文采用再生热处理恢复涡轮转子叶片组织和性能,浅论其主要技术路径。     

镍基单晶高温合金涡轮叶片薄壁效应研究进展

镍基单晶高温合金具有优异的高温综合性能,是航空发动机涡轮叶片和导向叶片等部件的首选材料,承受高温度和高应力的严苛服役环境。目前,高冷效叶片的结构设计中采用多种复杂冷却结构以提高其承温能力,其中以层板冷却和双层壁冷却为代表的微型冷却结构是其主流发展方向。但由于这类复杂涡轮叶片中存在超薄壁结构,已成为叶片制造的关键点和难点。本文综述了镍基单晶高温合金薄壁结构的发展趋势,分析了薄壁受限空间的缺陷产生及枝晶生长规律,阐述了薄壁结构对力学性能的影响,展望了先进涡轮叶片的制备及其组织控制的发展趋势。     

预合金粉对粉末冶金NiFe18.5Al25合金性能的影响

将元素Ni、Fe和Al粉以摩尔比56.5-18.5-25配料,分别按元素粉末高能球磨(300 r/min, 12 h)、元素粉末直接干混、50%元素粉+50%预合金粉末干混3种方式混料;混料在500 MPa的压力下压制成形,1 280 ℃下烧结;对合金烧结态进行相对密度测定、力学性能检测、X射线衍射分析(XRD)和断口形貌观察.结果表明:50%元素粉+50%预合金粉制备的合金性能最好,密度可达到6.61 g/cm3(相对密度94.8%),烧结态抗拉强度可达到868 MPa,说明元素粉末中添加的预合金粉可以控制烧结过程,提高合金的烧结密度,同时增强合金的力学性能.     

高温合金涡轮盘锻造工艺

航空航天发动机涡轮盘材料GH4133B是一种特殊的镍基高温合金新材料,该材料锻造成形时塑性低、变形抗力特别大、可锻温度范围窄、导热性差,且锻件的晶粒尺寸不能通过热处理细化,所以要满足锻件的内在质量要求,必须制定合理的工艺路线.本文从材料的化学成分、锻造工艺、模具设计和生产试制等方面介绍了涡轮盘的生产过程.其中,为了满足对锻造加热火次和每火次的锻造变形量的控制,提出了锻坯准备、表面清理、表面涂料、加热、刻标记和检验的新工艺路线.经验证通过热处理固溶、时效后的涡轮盘锻件,其力学性能完全达到使用要求,并且已批量生产,效果良好.     

高速凝固粉末冶金铝合金(2)

本篇是全文的第二部分,评述国内外工业高速凝固粉末冶金铝合金的发展状况,其中包括:各种高速凝固粉末冶金铝-锂合金的成分和性能,以及它们的制备工艺,重点评述了高模量、高强度铝-锂-铍合金的特点及其应用;各种高速凝固粉末冶金铝-铁耐热合金的成分和性能,重点评述了铝-铁-铈合金和铝-铁-钒-硅合金的特性。     

金刚石锯片浓度设计研究

本文根据金刚石切岩深度图及金刚石锯片切岩受力分析图,推导出了一种新的金刚石锯片浓度设计计算方法。将金刚石锯片施加给岩石单位面积的压力与岩石的抗压强度进行比较,如该压力大于岩石的抗压强度较多,则说明锯片工作面上的金刚石颗粒太少,应增加金刚石浓度;如该压力小于岩石的抗压强度,则说明金刚石锯片工作面上的金刚石颗粒太多,应降低金刚石的浓度。如此调整,直到该压力值略大于岩石的抗压强度为止。根据实例进行了计算,表明本文所提出的金刚石锯片浓度设计方法是可行的。     

高温合金涡轮盘锻件成形工艺研究

高温合金涡轮盘锻造成形工艺对于涡轮盘的制造至关重要。为了达到提高锻造质量的目的,以某GH4169涡轮盘为例,指出了传统涡轮盘锻造工艺存在的缺陷和问题,介绍了新工艺锻件成形过程,锻件技术指标满足要求,对涡轮盘制造具有积极的借鉴和促进作用。     

Evaluation of microstructure and phase relations in a powder processed Ti-44AI-12Nb alloy

Titanium aluminides based on the ordered face-centered tetragonal γTiAI phase possess attractive properties, such as low density, high melting point, good elevated temperature strength, modulus retention, and oxidation resistance, making these alloys potential high-temperature structural materials. These alloys can be processed by both ingot metallurgy and powder metallurgy routes. In the present study, three variations of the powder metallurgy route were studied to process a Ti-44Al-12Nb (at. %) alloy: (a) cold pressing followed by reaction sintering (CPprocess); (b) cold pressing, vacuum hot pressing, and then sintering (HP process); and (c) arc melting, hydride-dehydride process to make the alloy powder, cold isostatic pressing, and then sintering (AM process). Microstructural and phase relations were studied by x-ray diffraction (XRD) analysis, optical microscopy, scanning electron microscopy with an energy-dispersive spectrometer (SEM-EDS), and electron probe microanalysis (EPMA). The phases identified were Ti₃AI and TiAl; an additional Nb₂AI phase was observed in the HPsample. The microstructures of CPand HP processed samples are porous and chemically inhomogeneous whereas the AM processed sample revealed fine equiaxed microstructure. This refinement of the microstructure is attributed to the fine, homogeneous powder produced by the hydride-dehydride process and the high compaction pressures.     

Advanced high-velocity oxygen-fuel coating and candidate materials for protecting LP steam turbine blades against droplet erosion

This paper describes the water droplet erosion characteristics of advanced high-velocity oxygen-fuel (HVOF) coating and the materials used for steam turbine blading. For droplet erosion study, round samples as per ASTM G73-98 (“Standard Practice for Liquid Impingement Erosion Testing,” Vol 03.02, Annual Book of ASTM Standards, ASTM, 2004) were selected. The materials commonly used for steam turbine blading are X20Cr13, X10CrNiMoV122, and Ti6Al4V. During incubation as well as in the long run, advanced HVOF coating has performed much better than all these materials. This is due to enhanced particle kinetic energy caused by optimum flow of oxygen and fuel injection by modifying the fuel injector. Droplet erosion test results of these materials and advanced HVOF coating along with their properties and damage mechanism are reported and discussed in this paper.     

Ti-6Al-4V合金汽轮机动叶片的热处理工艺

针对Ti-6Al-4V合金汽轮机动叶片出现的组织异常,研究了两种热处理工艺对Ti-6Al-4V合金组织与性能的影响,并对锻造加热温度对该材料显微组织的影响进行了探讨。研究结果表明,Ti-6Al-4V合金汽轮机动叶片的组织异常是由于锻造加热温度过高或加热时间过长引起的,Ti-6Al-4V合金锻后采用固溶+时效或直接时效的热处理的方案都能满足产品毛坯性能要求,且锻后直接时效性能更优异。     

单晶高温合金的中温Ⅰ阶蠕变--涡轮叶片伸长的重要因素

单晶镍基高温合金已广泛用于制造先进燃气涡轮叶片,但这种合金至今仍被忽视的薄弱环节是它的中温Ⅰ阶蠕变伸长量远高于高温蠕变,而且与高温蠕变相比,中温Ⅰ阶蠕变对取向偏离、合金成分和热处理组织的变化更为敏感.虽然预蠕变引进较高的位错密度能有效抑制中温蠕变,但在实用上仍有困难.在选用单晶合金作为涡轮叶片时,应考虑到先进的二代和三代单晶在中温下的抗变形能力不如一代单晶,同时中温大应力状态下的叶片根部可能过度伸长.     

中间齿轮粉末冶金压制工艺及模具设计

根据现有铸钢中间齿轮的使用要求 ,提出了粉末冶金生产新工艺 ,设计了压制工艺及压制模具 ,简要介绍了模具结构特点。     

粉末冶金制备TiAl合金研究进展

轻质高强耐高温的TiAl合金一直是备受瞩目的先进结构材料,在航空航天、汽车等领域应用潜力巨大。但TiAl合金热加工性差,采用传统方法热成形难度大。而粉末冶金由于近净成形的特点,在制备复杂TiAl合金零部件上具有显著优势。近年来,科研工作者在TiAl合金粉末烧结技术上展开了大量工作,并取得一定进步。本文结合TiAl合金粉末成形技术的国内外发展现状,综述了放电等离子烧结(SPS)、热等静压、热压烧结、喷射成形、金属注射成形等方法制备TiAl合金的工艺、显微组织、力学性能和零部件,论述了上述制备方法的特点以及目前存在的不足,并提出了粉末冶金成形TiAl合金零部件的建议与未来发展方向。     

钛及钛合金粉末的制备现状

钛及钛合金具有优良的综合力学性能，在航空航天、航海、化工等领域得到日益广泛的应用。用粉末冶金法制造零部件，材料的利用率几乎可以达到100％，是降低钛及钛合金零部件生产成本的重要途径。本文评述了钛及钛合金粉末的制备技术及其现状,指出HDH钛粉和雾化钛粉是当今工业中主要应用的钛粉。伴随着钛粉末制备技术的成熟与发展，还原法直接生产钛粉和新兴的TiO2熔盐电解法生产钛粉，将成为制备低成本、高性能钛粉新的工业生产方法，是降低钛粉末冶金零部件成本的新的发展方向。元素混合法制备钛合金粉，因其较预合金化法成本低廉，工艺成熟。且性能优越，必将成为钛合金粉的主要生产方法。