High temperature oxidation behavior of an equimolar refractory metal-based alloy 20Nb-20Mo-20Cr-20Ti-20Al with and without Si addition
High temperature oxidation behavior of an equimolar refractory metal-based alloy 20Nb-20Mo-20Cr-20Ti-20Al with and without Si addition
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DOI：
10.1016/j.jallcom.2016.07.219
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发表时间：
2016-12-15
影响因子：
6.2
通讯作者：
Heilmaier, M.
中科院分区：
文献类型：
--
作者：
Gorr, B.;Mueller, F.;Heilmaier, M.
研究了难熔高熵合金20Nb-20Mo-20Cr-20Ti-20Al在900℃、1000℃和1100℃下的高温氧化行为。发现合金的氧化动力学在所有温度下都是线性的。由于富铬氧化物鳞片的不连续形成，形成的氧化鳞片在很大程度上是不均匀的，既有较厚的多孔层，也有很薄的氧化鳞片。然而，加入1 at可适度提高其抗氧化性。%如果。含硅合金在1000℃和1100℃的氧化过程中获得的热重数据显示了明显的抛物线氧化期，然而，随着暴露时间的延长，这种抛物线氧化转变为线性氧化。利用扫描电子显微镜（SEM）和透射电子显微镜（TEM）进行的显微结构研究表明，Si的加入产生了一个几乎连续的富铝层，这似乎是防止进一步氧化的良好保护。在两种合金中观察到由不同氧化物和氮化物组成的明显的内腐蚀攻击区。为了确定腐蚀产物的化学成分及其质量分数，采用x射线衍射（XRD）对合金在不同氧化时间后形成的粉末氧化层进行了定量分析。在氧化过程中，金红石被确定为氧化鳞片的主要相，从而使氧化过程中相对较高的质量增益得到合理解释。(C) 2016 Elsevier B.V.版权所有
The high temperature oxidation behavior of a refractory high-entropy alloy (HEA) 20Nb-20Mo-20Cr-20Ti-20Al at 900 degrees C, 1000 degrees C and 1100 degrees C was investigated. The oxidation kinetics of the alloy was found to be linear at all temperatures. Oxide scales formed are largely inhomogeneous showing regions with thick and porous layers as well areas with quite thin oxide scales due to formation of discontinuous chromium-rich oxide scales. However, the oxidation resistance can be moderately improved by the addition of 1 at.% Si. The thermogravimetric data obtained during oxidation of the Si-containing alloy at 1000 degrees C and 1100 degrees C reveal pronounced periods of parabolic oxidation that, however, change towards linear oxidation after prolonged exposure times. Microstructural investigations using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) document that the Si addition gives rise to a nearly continuous alumina-rich layer which seems to be responsible for the good protection against further oxidation. Pronounced zones of internal corrosion attacks consisting of different oxides and nitrides were observed in both alloys. In order to determine the chemical composition of the corrosion products and their mass fraction, quantitative X-ray diffraction (XRD) analysis was performed on powdered oxide scales that formed on the alloys after different oxidation times. Rutile was identified as the major phase in the oxide scales rationalizing the relatively high mass gain during oxidation. (C) 2016 Elsevier B.V. All rights reserved.