Effects of W on high-temperature antioxidative properties of Nb/Nb5Si3 composite
Effects of W on high-temperature antioxidative properties of Nb/Nb5Si3 composite
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W对Nb/Nb5Si3复合材料高温抗氧化性能的影响
DOI：
10.2991/amcce-17.2017.190
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发表时间：
2017-03
期刊：
影响因子：
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通讯作者：
刘煊
中科院分区：
文献类型：
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作者：
龙文元;刘伟国;刘煊
以Nb-20Si-5Al-15Ti-xW (at。采用火花等离子烧结（SPS）技术制备了%)。采用扫描电子显微镜（SEM）、x射线衍射仪（XRD）和电子探针显微镜（EPMA）研究了合金的高温氧化行为和显微组织。结果表明：复合材料的显微组织由（Nb, Ti， W）ss、α-Nb5Si3、γ-Nb5Si3和（Nb, Ti， W）5Si3相组成；随着W添加量的增加，复合材料在800℃时的抗氧化性能先降低后升高。在1100℃时，W的加入使材料的抗氧化性能在前40h内下降，随后又升高。Nb-20Si-5Al-15Ti-xW表现出害虫氧化行为。复合材料在1100℃时的抗氧化性能优于800℃时的抗氧化性能，因为氧化层结构更加致密。铌硅合金被认为有可能取代镍基超级合金，用于高温（1100°C）应用。在开发NbSS/Nb5Si3复合材料的过程中获得了优异的力学性能[2-5]；最佳组合物的断裂韧性值超过20MPa·m[2,5]。然而，它们在中高温下的抗氧化性差是其在高温应用中的主要障碍。目前，人们一直在努力寻找合金元素并优化其含量，以提高氧化性能。先前的研究表明，添加Cr、Al、Ti、Mo和Hf等元素可以显著提高Nb/Nb5Si3原位复合材料的抗氧化性[1,6 - 10]。添加锗和B作为Si的部分替代，也改善了Nb/Nb5Si3原位复合材料[3]的氧化行为。然而，难熔金属及其合金在中等温度下（< 850°C）会遭受虫害破坏[11-13]。最近的研究[3,14 -18]报道了在Nb/Nb5Si3复合材料中添加锡的有益效果，可以延缓800°C下的害虫现象。这种效应在1200°C时也是有益的[14,15]。相比之下，Bewlay等人报告说，锡在高温下对抗氧化性的影响很小。不幸的是，提高抗氧化性所需的合金化水平可能会牺牲复合材料的室温断裂韧性和高温强度。因此，需要进一步的研究来实现氧化性能和力学性能的平衡。本研究采用SPS技术制备了Nb/Nb5Si3原位复合材料。本研究旨在确定W对Nb/Nb5Si3复合材料在800℃和1100℃静态空气中抗氧化性能的影响。铌（99.9wt）粉末的实验条件和方法。%， -200目),Si(99.9wt。%， -300目),Al(99.8重量。%， -100目),Ti(99.8wt。%， -200目)，W(99.9重量。%， -300目)为原料。Nb-20Si-5Al-15Ti(。Nb-20Si-5Al-15Ti-5W(%)。%)和Nb-20Si-5Al-15Ti-8W(at。在真空气氛下用SPS制备了%)复合材料。这些粉末在第二届自动化、机械控制和计算工程国际会议（AMCCE 2017）上进行了干混合。版权所有©2017，作者。亚特兰蒂斯出版社出版。这是一篇基于CC BY-NC许可（http://creativecommons.org/licenses/by-nc/4.0/）的开放获取文章。工程研究进展，第118卷
The multi-component Nb-Si system in-situ composites with composition of Nb-20Si-5Al-15Ti-xW (at. %) were prepared by Spark Plasma Sintering (SPS) technology. The high temperature oxidation behavior and microstructure of the alloy were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron probe microscopy (EPMA). The results show that the microstructure of the composite consists of (Nb, Ti, W)ss, α-Nb5Si3, γ-Nb5Si3 and (Nb, Ti, W)5Si3 phase. With an increase of W addition, the oxidation resistance of the composites at 800°C decrease firstly and then increase. At 1100°C the addition of W decreased the oxidation resistance during the first 40h, then changed to increase the oxidation resistance. Pest oxidation behavior was exhibited by the Nb-20Si-5Al-15Ti-xW. The oxidation resistance of the composite at 1100°C is better than at 800°C because the oxide scale is more compact structure. Introduction Nb-Si alloys are considered attractive for possible replacement of Ni-base super alloys for high temperature (>1100°C) applications[1]. Excellent mechanical properties have been achieved during the development of NbSS/Nb5Si3 composites [2-5]; The best compositions have fracture toughness values exceeding 20MPa·m[2,5]. However, their poor oxidation resistance at intermediate and high temperatures is a major obstacle to their use in high temperature applications. Now many efforts have been devoted to looking for alloying elements and optimizing their content to enhance the onxidation behavior. Previous work has shown that the oxidation resistance of the Nb/Nb5Si3 in situ composites can be improved significantly by additions such as Cr, Al, Ti, Mo and Hf [1,6–10]. Germanium and B additions, as a partial replacement of Si, also improve the oxidation behaviour of Nb/Nb5Si3 in-situ composites [3]. However, refractory metals and their alloys can suffer from pest damage at intermediate temperatures (< 850°C) [11-13]. Recent works [3, 14-18] reported beneficial effects of adding tin to Nb/Nb5Si3 composites, which delayed the pest phenomena at 800°C. This effect was also beneficial at 1200°C[14,15]. In contrast, Bewlay et al. [3] reported that tin had a minor effect on oxidation resistance at high temperatures. Unfortunately, the level of alloying required for the improvement of oxidation resistance could sacrifice the room temperature fracture toughness and high temperature strength of the composites. Therefore, further investigations are needed to achieve the required balance of oxidation performance and mechanical properties. In this study, the Nb/Nb5Si3 in situ composites were fabricated by SPS technology. This study aims to determine the effect of W on the antioxidative performance of Nb/Nb5Si3 composite materials in static air at 800°C and 1100°C. Experimental conditions and methods Powders of Nb(99.9wt.%, -200 mesh), Si(99.9wt.%, -300 mesh), Al(99.8wt.%, -100 mesh), Ti(99.8wt.%, -200 mesh), and W(99.9wt.%, -300 mesh) were used as raw materials. The Nb-20Si-5Al-15Ti(at.%), Nb-20Si-5Al-15Ti-5W(at.%) and Nb-20Si-5Al-15Ti-8W(at.%) composites were prepared by SPS in a vacuum atmosphere. The powders were dry-mixed in a 2nd International Conference on Automation, Mechanical Control and Computational Engineering (AMCCE 2017) Copyright © 2017, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Advances in Engineering Research, volume 118