Nb-Si基超高温合金及其定向凝固工艺的研究进展

具有低密度和高熔点特性的Nb-Si基超高温合金是下一代航空发动机热端部件的重要候选材料之一.但Nb-Si基超高温合金的低室温断裂韧性限制了其工业化应用,合金化和定向凝固是改善室温断裂韧性的有效方法,本文综述了这2个方面的研究进展.合金化方面重点介绍了合金元素通过位错增韧和相改变增韧实现铌基固溶体(Nbss)相的韧化,通过固溶强化和相变提高硅化物相的高温性能,促进硅化物以近"Y"型生长,改善两相的界面等影响,分析发现Ti、Hf、Zr、B和Mg等元素均可改善室温断裂韧性.定向凝固方面综述了Nb-Si基超高温合金的定向凝固方法及特点,不同定向凝固工艺对Nb-Si基合金的组成相、组织形貌、室温断裂韧性以及高温强度的影响,定向凝固过程的组织演变规律及强化机理,分析发现调控工艺可获得Nbss/Nb5Si3良好单向生长的组织.在保证Nbss/Nb5Si3共晶耦合单向生长的情况下,减小Nbss相的厚度,提升其连续性是提高室温断裂韧性的有效方法.还展望了Nb-Si合金化与定向凝固的未来发展趋势.     

Nb-Si基超高温合金研究进展

Nb-Si基超高温合金具有高熔点、低密度和良好的高温力学性能,目标使用温度达到1 200~1 450℃,有望成为新一代高推重比航空发动机热端部件最有潜力的候选材料。综述了该合金的成分设计、组织调控、性能表征及其加工制备技术,重点介绍了该合金成分-组织-性能之间的关联,探讨了定向凝固技术制备Nb-Si合金涡轮叶片存在的问题。     

镍基单晶高温合金DD3制备过程中晶粒演化和选晶行为的EBSD研究

采用选晶法在改进的Bridgman定向凝固炉上进行镍基单晶高温合金DD3定向凝固实验,研究了选晶法制备镍基单晶高温合金过程中晶粒组织演化和螺旋选晶行为,采用电子背散射衍射(EBSD)技术对晶粒的竞争过程进行分析.结果表明,选晶器引晶段的主要作用是优化晶粒取向,获得取向良好的<001>定向凝固组织.在距激冷板36.1 m...     

先进航空高温结构材料的钎焊与扩散焊技术

概述了在先进航空高温结构材料的钎焊与扩散焊技术领域的一些研究结果与进展,其中包括已经获得实际应用的钎焊、扩散焊技术以及相关有价值的探索性研究结果.主要内容:定向凝固高温合金、单晶合金、定向凝固Ni3Al基高温合金、ODS合金、钛合金、钛铝金属间化合物材料、钛基复合材料等高温结构材料的钎焊与扩散焊技术.     

高温合金定向凝固技术研究进展

首先回顾了定向凝固的发展历史,重点分析了液态金属冷却定向凝固的技术特点。总结了高温度梯度下制备的定向凝固法单晶高温合金在组织和性能方面的研究现状,结合作者在本领域的研究,着重分析了定向凝固温度梯度、凝固速率、晶体取向、熔体超温处理、熔体对流控制对组织和性能的作用规律和机制,认为高温度梯度定向凝固是细化组织、减少缺陷、提高合金性能的重要途径。最后展望了高温合金定向凝固的发展趋势。     

定向凝固和单晶高温合金的再结晶

本文系统分析了定向凝固和单晶高温合金再结晶的特点、危害以及影响再结晶的主要因素,阐述了再结晶的物理本质.再结晶行为受合金元素、变形程度、热处理温度及时间、变形速率、变形工艺等的影响.再结晶的物理本质是由铸态γ'相溶解控制的高能态畸变组织向低能态无畸变组织转变的过程.镍基定向凝固高温合金再结晶开始温度在1050℃左右,钴基定向凝固高温合金在1100℃左右.定向凝固和单晶高温合金的动态再结晶行为主要与高温氧污染和自由表面有关.再结晶对高温持久、疲劳性能影响较大,含再结晶层的断口源区表现为沿晶断裂.目前定向凝固构件上的再结晶检测普遍采用金相方法.     

定向凝固高温合金的研究进展

论述了定向凝固高温合金的概念和特色,总结了国内外定向凝固高温合金的发展历程。分析了化学成分、制备技术以及热处理工艺对定向凝固合金组织及性能的影响。     

航空航天焊接专题：先进航空高温结构材料的钎焊与扩散焊技术

概述了在先进航空高温结构材料的钎焊与扩散焊技术领域的一些研究结果与进展,其中包括已经获得实际应用的钎焊、扩散焊技术以及相关有价值的探索性研究结果。主要内容：定向凝同高温合金、单晶合金、定向凝固Ni3Al基高温合金、ODS合金、钛合金、钛铝金属间化合物材料、钛基复合材料等高温结构材料的钎焊与扩散焊技术。     

镍基高温合金定向凝固特性的研究

本文以不含钴的镍基铸造高温合金为对象,研究在快速凝固法定向结晶的条件下,合金温度场和温度梯度的变化,以及某些冶金参数对定向凝固特性的影响,探讨高温合金的定向凝固规律。     

焊接结构与设计

20093211先进航空高温结构材料的钎焊与扩散焊技术/李晓红//焊接.-2008(11):9~18概述了在先进航空高温结构材料的钎焊与扩散焊技术领域的一些研究结果与进展,其中包括已经获得实际应用的钎焊、扩散焊技术以及相关有价值的探索性研究结果。主要内容:定向凝固高温合金、单晶合金、定向凝固Ni3Al基高温合金、ODS合金、钛合金、钛铝金属间化合物材料、钛基复合材料等高温结构材料的钎焊与扩散焊技术。图14表11参32焊接结构与设计     

Manufacturing Processes for Long-Life Gas Turbines

Dual-alloy turbine wheels produced by solid-state diffusion bonding of vacuum investment cast blade rings of one superalloy to preconsolidated powder metal hubs of a second superalloy have the long cyclic lives characteristic of wrought or powder superalloys combined with the high creep strength and net-shape blades characteristic of cast superalloys. A wide variety of superalloys and turbine configurations are compatible with this technology. Improved temperature capability turbine blades and vanes of the MAR-M 247 alloy made by directional solidification casting processes are now in volume production for Garrett gas turbines. Single-crystal alloys derivative to MAR-M 247 further extend the temperature capability of turbine blades and have been successfully engine tested. These blades are produced by a relatively simple modification of the processes used to manufacture directionally solidified blades.     

Microstructure and Tensile/Corrosion Properties Relationships of Directionally Solidified Al–Cu–Ni Alloys

Al–Cu–Ni alloys are of scientific and technological interest due to high strength/high temperature applications, based on the reinforcement originated from the interaction between the Al-rich phase and intermetallic composites. The nature, morphology, size, volume fraction and dispersion of IMCs particles throughout the Al-rich matrix are important factors determining the resulting mechanical and chemical properties. The present work aims to evaluate the effect of the addition of 1wt%Ni into Al–5wt%Cu and Al–15wt%Cu alloys on the solidification rate, macrosegregation, microstructure features and the interrelations of such characteristics on tensile and corrosion properties. A directional solidification technique is used permitting a wide range of microstructural scales to be examined. Experimental growth laws relating the primary and secondary dendritic spacings to growth rate and solidification cooling rate are proposed, and Hall–Petch type equations are derived relating the ultimate tensile strength and elongation to the primary dendritic spacing. Considering a compromise between ultimate tensile strength and corrosion resistance of the examined alloys samples from both alloys castings it is shown that the samples having more refined microstructures are associated with the highest values of such properties.     

Solidification of high-refractory ruthenium-containing superalloys

The effect of alloy chemistry on single crystal solidification has been investigated in a series of model high refractory Ni-base superalloys with variations in ruthenium, rhenium and aluminum. Over the range of composition investigated, the initial phase to form during solidification was either the γ phase (FCC Ni-solid solution) or the δ phase (HCP Re-rich phase). In a quaternary Ni-Al-Ta-Re alloy containing 1.7 at.% (5.6 wt.%) Re, δ-Re nucleated at a temperature well above the liquidus temperature of pure Ni and grew unconstrained into six-fold Re-rich dendrites. These dendrites served as potent nucleation sites for γ grains as temperature decreased during directional solidification. Ruthenium additions in the range of 2.5∽9.0 at.% (4.1∽14.1 wt.%) lowered the temperature at which the δ nucleated and eventually suppressed the formation of this phase during solidification. Ru additions also increased the liquidus temperatures of the multicomponent superalloys. The implications for the design of Ru-containing superalloys are discussed.     

微量元素磷在铁镍基变形高温合金中的作用

综述了磷对铁镍基变形合金的影响及机理。简述了磷的性质,来源及冶炼控制,介绍了磷的凝固偏析及对合金凝固过程的影响与机理,以微量元素对晶界能,晶界扩散和晶界结合力的影响机理为基础,比较并分析了磷对合金组织结构和力学性能的各种影响机制。     

热腐蚀环境中高温合金的蠕变与断裂

研究了分别为轧制、普通铸造、定向凝固及单晶的6种高温合金在热腐蚀条件下的蠕变断裂性能.其中涉及到试验温度、晶粒尺寸、晶界状态等对性能的影响.探讨了蠕变应变与热腐蚀交互作用下,合金中所产生的灾害性侵蚀及断裂过程.     

Use of plasma spray technology for deposition of high temperature oxidation/corrosion resistant coatings – a review

High temperature oxidation is one of the main failure modes of the hot‐section components in gas turbines, boilers, waste incinerations, diesel engines, coal gasification plants, chemical plants and other energy generation systems. In such applications the use of Fe‐, Ni‐ and Co‐based alloys, especially of superalloys is well known. The superior mechanical strength and good corrosion resistance of the superalloys at high temperature make them favorites for such applications. However, the presence of combustion gases constitutes an extreme environment and hot corrosion is inevitable when superalloys are used at high temperatures for long durations of time. Therefore these alloys need to be protected against this type of oxidation. Several countermeasures have been suggested in the literature to combat the same. One such countermeasure against hot corrosion and oxidation constitutes the deposition of protective coatings on these alloys. Among the various techniques used for deposition of coatings, plasma spraying is a versatile technology that has been successful as a reliable cost‐effective solution for many industrial problems. It allows the spraying of a wide range of high performance materials from superalloys and refractory intermetallic compounds to ceramics with continuously increasing commercial applications. Furthermore it does not cause deterioration of the substrate alloys, and relatively thick coatings can be formed with high deposition rates. In this paper the technique of plasma spraying has been detailed and the role of plasma sprayed coatings to arrest high temperature oxidation has been discussed with the help of a comprehensive literature survey. The main focus of this investigation is the studies related to plasma sprayed NiCrAlY, Ni‐Cr, Nickel aluminide and Co‐based coatings.     

合金元素和凝固技术对NiAl金属间化合物的影响

本文介绍了金属间化合物NiAl的合金化与凝固技术的研究现状.介绍了合金化对NiAl的塑性、韧性和强度的影响,以及定向凝固、普通铸造和单晶制备技术对NiAl强度的影响,其中由定向凝固技术制备的NiAl与难熔金属相组成的共晶合金具有良好的高温强度和室温韧性.     

Secondary dendrite arm migration caused by temperature gradient zone melting during peritectic solidification

During dendritic solidification of Al–Ni and Sn–Ni peritectic alloys in a temperature gradient, it is observed that a thick peritectic layer forms on the front edge of the secondary dendrite arm of the primary phase, while there is almost no peritectic phase on the back edge. This observation is explained satisfactorily by a new version of secondary dendrite arm migration caused by temperature gradient zone melting during peritectic solidification, which involves both primary and peritectic phases. Experimental and theoretical analysis in the present work demonstrates that temperature gradient zone melting can cause extensive melting/solidification of the primary and peritectic phase during peritectic solidification.     

新型真空熔化定向凝固装置的研制

对真空感应熔炼与双区加热结合在一起的定向凝固装置的可行性进行了研究，并研制出一套新型真空熔化定向凝固装置。该装置的主要特点是：（１）可定向凝固出较大尺寸的样品；（２）兼有熔炼和定向凝固的功能，熔炼好的合金液能自动底注到加热器内的型壳中；（３）定向凝固部分采用了先进的双区加热技术，既提高了温度梯度又减少了合金元素的烧损；（４）抽拉速度能在很大范围内调节。