表面处理对第二代单晶高温合金胞状再结晶的影响

对第二代镍基单晶高温合金进行表面处理并在1000～1200℃保温,研究表面加工工艺和热处理条件对胞状再结晶行为的影响.结果表明:磨削、吹砂、喷丸试样热处理后表面均发生了胞状再结晶,其生成厚度依次增加.喷丸试样经1200℃/50h后胞状再结晶区厚度可达0.1mm,晶团之间及与基体之间存在取向差小于5°的小角晶界和35～4...     

镍基单晶高温合金凝固组织特征的研究进展

镍基单晶高温合金的凝固组织对其最终的高温力学性能有着重要的影响,由于制造工艺条件限制,单晶高温合金的制备和加工中总会出现杂晶,保持单晶结构的完整性对提高单晶合金的冶金质量和降低维护成本具有重要意义.综述了镍基单晶高温合金在铸造、焊接、表面熔凝工艺条件下的凝固组织特征的研究现状,分析了工艺条件、工艺参数等对凝固组织和性能的影响,并展望了杂晶缺陷的控制、实现单晶叶片连接区的单晶化.     

镍基单晶高温合金的反常屈服行为与变形机制

镍基单晶高温合金是高推重比发动机涡轮叶片的关键材料.综述了镍基单晶高温合金的反常屈服行为,并讨论了导致产生这种反常屈服行为的变形机制及这些变形机制的发展过程.     

单晶镍基高温合金CMSX-486

Cannon- Muskegon Corp.公布了一个具有改进蠕变持久强度的单晶镍基高温合金 CMSX- 486。该合金的化学成分为 9. 3%Co,8. 6%W,5 . 7%Al,5 %Cr,3%Re。并通过 B,C,Hf,Zr含量的最佳匹配 ,实现合金的晶界强化。它设计为铸态使用 ,能使复杂铸件的实收率大幅度提高 ,而不存在固溶热处理的再结晶问题。单晶高温合金零件改进的性能是优良的抗热疲劳、抗低周疲劳和抗氧化性能的结果。这类合金零件也具有高的蠕变强度 ,特别是在叶片前后缘处没有横向晶界对其性能十分有利单晶镍基高温合金CMSX-486@全宏声…     

吹砂、抛光及其电解腐蚀后处理对单晶高温合金表面组织和再结晶行为的影响

采用吹砂处理、砂带抛光、毡轮抛光3种表面处理使铸态单晶(SX)Ni基高温合金叶片表面形成塑性变形层,对叶片表面变形层进行电解腐蚀实验,然后进行标准热处理,研究了单晶高温合金叶片表面处理的变形层及其电解腐蚀后显微组织。结果表明:3种表面处理的铸态单晶高温合金叶片表面变形层深度分别约为6,3.5μm和2μm,并在吹砂处理和砂带抛光的表面变形层周围存在显微裂纹;表面变形层电解腐蚀过渡区内存在大量γ′变形组织,且3种表面处理的塑性变形残存量依次递减,而变形层完全电解腐蚀区内无塑性变形痕迹;标准热处理后,变形层未电解腐蚀区存在凹陷特征和再结晶晶粒,但无塑性变形痕迹;变形层完全电解腐蚀区无明显凹坑和再结晶晶粒。     

脉冲电流对GH4049合金静态再结晶行为的影响

为解决高温合金的难变形问题,研究了高密度脉冲电流对GH4049合金静态再结晶行为的影响规律,分析了再结晶起始温度、再结晶激活能随脉冲电流频率变化的规律及机制,讨论了时效过程中粗化γ’相对合金再结晶行为的影响.研究表明:与常规温度场相比,脉冲电流作用下GH4049合金的静态再结晶起始温度明显降低,且降低幅度随脉冲电流频率、电流密度增加而增大;粗化的γ’相对合金的静态再结晶有促进作用,这对于解决难变形镍基高温合金热加工变形温度区间窄的问题具有积极意义.     

难熔元素对镍基单晶高温合金凝固特性及组织的影响

镍基单晶高温合金的性能与难熔元素Re、W、Ta等的含量之间有着紧密的联系.总结了在镍基单晶高温合金的发展过程中难熔元素添加的特点,综述了难熔元素对镍基单晶高温合金的凝固特性与凝固组织的影响,并指出了其中存在的问题,展望了未来研究发展的方向.     

镍基高温合金热塑性变形晶粒细化与粗化的博弈关系及演进

为深入揭示Ni80A镍基高温合金热塑性变形过程中晶粒细化与晶粒粗化之间的博弈关系及演进,基于晶粒细化等温变形实验和晶粒生长粗化实验分别建立了动态再结晶和晶粒生长数学模型.结合所建数学模型和有限元分析发现,Ni80A镍基高温合金在热塑性变形过程中动态再结晶晶粒细化和晶粒生长粗化的博弈关系及演进共同决定了晶粒尺寸的非线性演变.本工作绘制了两种晶粒尺寸演变机制的博弈关系图并分析其对晶粒尺寸的单独及耦合作用.结果表明:变形初期晶粒生长粗化占主导地位,变形中后期动态再结晶晶粒细化占主导地位,整个热塑性变形过程中二者相互博弈,共同影响试样的晶粒尺寸.     

高温镍基单晶合金NiCoCrAlYTa涂层的抗热腐蚀性能

以往,对高温镍基单晶合金上采用低压等离子喷涂制备的NiCoCrAlYTa涂层的热腐蚀性能研究较少.为此,采用低压等离子方法在镍基高温单晶合金上制备了NiCoCrAlYTa涂层,采用涂盐法研究了Na2SO4对试样在1 123 K空气中热腐蚀的影响,同时分析了NiCoCrAlYTa涂层的形貌及结构.结果表明:高温镍基单晶合金遭受了严重的热腐蚀,出现了内硫化和内氧化;NiCoCrAlYTa涂层由于表面生成了致密、保护性的Al2O3膜,以及涂层中Cr和Ta元素的作用而表现出优异的抗热腐蚀性能.结果证实,NiCoCrAlYTa涂层可以很好地提高单晶合金的抗热腐蚀性能.     

不同元素对镍基合金铸态组织的影响

镍基单晶高温合金是一种应用于航空发动机涡轮叶片的重要合金,镍基单晶高温合金能够在航空发动机涡轮叶片工作时的恶劣工况条件下获得良好的使用性能。镍基单晶高温合金的性能与镍基单晶高温合金的凝固组织有着密切的联系,为获取更好的使用性能需要了解不同元素对镍基单晶高温合金铸态组织的影响,并以此为基础开发出性能更好的镍基单晶高温合金用,以提高航空发动机的性能。     

New materials for industrial gas turbines

Abstract

Recent developments in superalloy technology for turbine aerofoil applications are reviewed, such as single crystals (SC), oxide dispersion strengthening (ODS), and rapid solidification (RS). Single crystal and ODS superalloys are in production use in aircraft turbine engines. While ODS superalloys exhibit higher strength at high temperatures, SC superalloys are somewhat stronger at intermediate temperatures. It will depend on engine design which alloy can give greater advantage. The strength potential of RS superalloys is probably less than or equal to SC superalloys which does not justify the complicated processing. If SC or ODS technology is to be applied to industrial engines of high power, more corrosion resistant alloys must be developed and component fabrication methods will have to be scaled-up.

MST/518     

Ru对镍基单晶高温合金凝固特性、TCP相析出及蠕变性能影响的研究进展EI北大核心CSCD

镍基单晶高温合金因优异的高温力学性能而被广泛应用于航空发动机和地面燃气轮机的涡轮叶片等关键热端部件。Ru元素作为第四代、第五代镍基单晶高温合金的主要特征元素,其添加对合金从凝固特性到最终的服役性能都起到关键的影响。本文从镍基单晶高温合金的凝固特性、凝固组织、TCP相析出及蠕变性能等方面出发,综述了Ru元素对镍基单晶高温合金影响的研究进展,系统分析了Ru的添加对合金凝固路径、凝固特征温度、微观偏析等凝固特性及共晶、碳化物等凝固组织的影响规律,并重点探究了Ru的添加能抑制TCP相析出及提高合金蠕变性能的原因。目前由于多组元交互作用对组织与性能影响机理的复杂性,使得含Ru高温合金的成分设计与优化具有更高的挑战,建议未来含Ru高温合金的相关研究从富Ru新相的析出原因及抑制、Ru添加对凝固缺陷的影响及Ru与其他元素交互作用对“逆分配”效应及TCP相析出的影响机制等方面做进一步探究,为发展新型高性能含Ru高温合金的设计提供思路。     

我国航空涡轮高温材料及工艺进展

扼要介绍了北京航空材料研究院近来在航空发动机涡轮部件用铸造热强材料及工艺的新进展，包括：单合金；铸造金属间化合物基叶片金；细晶铸造工艺；生产单晶叶片用的模糊，型芯，壳型。     

Computer-aided characterization of solification processes

The directional solidification process is used to make columnar grained and single crystal turbine blades for the hot section of advanced gas turbine engines. These blades are fabricated using a family of alloys known as the superalloys. The microstructural features of these alloys are dependent upon the thermal characteristics of the solidification process. In this article it will be shown how an improved understanding of such processing has been achieved using computer simulation and advanced graphics techniques. This has led to new insight into cause and effect relative to grain quality and microstructural details concerning dendritic features. Improved processing methods have evolved based on the application of scientific methodology to what has traditionally been the art of casting.     

Re对单晶高温合金持久性能的强化作用

通过对四种不同Re含量的单晶高温合金1100℃/140MPa持久性能研究,探讨了Re对单晶高温合金持久性能的强化作用.结果表明:合金的稳定性显著影响Re对高温持久性能的强化作用.适量Re提高单晶高温合金的持久寿命,过量Re降低合金的稳定性,明显降低Re对合金的强化作用.     

Crystal plasticity finite‐element modelling of cyclic deformation and crack initiation in a nickel‐based single‐crystal superalloy under low‐cycle fatigue

Nickel‐based single‐crystal superalloys are predominantly used for turbine blades in aircraft engines and land‐based gas turbines. Understanding and predicting the fatigue failure of Ni‐based single‐crystal superalloys are critical to ensure the safety of these components during operation. In this paper, low‐cycle fatigue experiments were carried out to investigate cyclic deformation of a nickel‐based single‐crystal superalloy MD2, recently developed by GE Power, with different crystallographic orientations. Specialty in situ scanning electron microscope (SEM) tests were also conducted to study the slip‐controlled initiation of short cracks under low‐cycle fatigue. In particular, the stress–strain response for both [001] and [111] orientations was used to calibrate a crystal plasticity model, which allowed us to simulate the activation of crystallographic slip systems and predict the initiation of short fatigue crack. Using the accumulated shear strain as a criterion, the simulations confirmed that the slip system with the maximum accumulated shear strain appeared to control the crack initiation. The location and direction of slip traces and short cracks, captured by the crystal plasticity finite‐element simulations, agreed with the in situ SEM observations. The modelling tool will be valuable for assessing the structural integrity of critical gas turbine blades.     

单晶涡轮叶片合金的薄截面尺寸效应

单晶涡轮叶片合金存在明显的薄截面尺寸效应,当截面尺寸小于0.5mm时,持久寿命大幅降低,尤其是中温持久寿命.截面尺寸效应是由于试样厚度减小引起显微组织和表面完整性的变化以及实验误差综合影响所致.     

Rafting in single crystal nickel-base superalloys — An overview

Currently nickel-base single crystal (SX) superalloys are considered for the manufacture of critical components such as turbine blades, vanes etc., for aircraft engines as well as land-based power generation applications. Microstructure and high temperature mechanical properties are the major factors controlling the performance of SX superalloys. Rafting is an important phenomenon in these alloys which occurs during high temperature creep. It is essential to understand the rafting mechanism, and its characteristics on high temperature properties before considering the advanced applications. In this review article, the thermodynamic driving force for rafting with and without stress is explained. The nature and influence of rafting on creep properties including pre-rafted conditions are discussed. In addition, the effect of stress state on γ/γ′ rafting, kinetics and morphological evolution are discussed with the recent experimental results.     

汽车增压器涡轮用铸造高温合金热裂研究进展

采用高温合金浇注汽车增压器涡轮时,叶片极易产生热裂,热裂的存在严重影响了铸造高温合金在增压涡轮上的使用。介绍了几种目前国内广泛使用的汽车增压器涡轮用铸造高温合金,对铸件热裂的形成机理进行了综述,重点探讨了铝、钛、碳、锆和铪等元素对铸造高温合金热裂倾向性的影响。综述了合金凝固方式和铸型性质、浇注条件、铸件结构、浇注系统等铸造工艺参数对热裂的影响,并提出了防止热裂产生的措施。     

镍基单晶高温合金Larson-Miller曲线的预测

提出了一种预测镍基单晶高温合金Ｌａｒｓｏｎ－Ｍｉｌｌｅｒ曲线的新方法,应用于现有镍基单晶高温合金的Ｌａｒｓｏｎ－Ｍｉｌｌｅｒ曲线的预测。对预测的结果与试验结果进行了比较,证明该方法能够准确地预测镍基单晶高温合金的Ｌａｒｓｏｎ－Ｍｉｌｌｅｒ曲线。