Lo Kai-Chi, Chang Yao-Jen, Murakami Hideyuki, Yeh Jien-Wei, Yeh An-Chou
Department of Materials Science and Engineering, National Tsing Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu, 30013, Taiwan, China.
Research Centre for Structural Materials, National Institute for Materials Science, Sengen 1-2-1, Tsukuba, Ibaraki, 305-0047, Japan.
Sci Rep. 2019 May 13;9(1):7266. doi: 10.1038/s41598-019-43819-x.
Although refractory high entropy alloys (RHEAs) have shown potentials to be developed as structural materials for elevated temperature applications, most of the reported oxidation behaviours of RHEA were associated with short term exposures for only up to 48 hours, and there is a lack of understanding on the oxidation mechanism of any RHEA to-date. In this work, by using thermogravimetric analysis, isothermal oxidation was conducted on a novel RHEA at 1000 °C and 1100 °C for up to 200 hours, which is an unprecedented testing duration. The external oxide layer strongly influenced the weight gain behaviours, and it consisted of CrTaO-based oxide with some dispersion of AlO and CrO. At 1000 °C, the inability to form dense CrTaO-based oxide layer resulted an exponential dependence of weight gain throughout 200 hours. At 1100 °C, mass gain curve showed two parabolic dependences associated with the formation of protective CrTaO-based oxide layer and the weight gain after 200 hours was 4.03 mg/cm, which indicates that it is one of the most oxidation resistant RHEAs comparing to literature data to-date. This work can also provide insights on how to further develop RHEA to withstand long term oxidation at elevated temperatures.
尽管难熔高熵合金（RHEAs）已显示出有潜力被开发为高温应用的结构材料，但大多数已报道的RHEA氧化行为仅涉及长达48小时的短期暴露，并且迄今为止对任何RHEA的氧化机制都缺乏了解。在这项工作中，通过热重分析，在1000°C和1100°C下对一种新型RHEA进行了长达200小时的等温氧化，这是前所未有的测试持续时间。外部氧化层强烈影响重量增加行为，它由基于CrTaO的氧化物组成，并伴有一些AlO和CrO的分散。在1000°C时，无法形成致密的基于CrTaO的氧化层导致在整个200小时内重量增加呈指数依赖关系。在1100°C时，质量增加曲线显示出与保护性基于CrTaO的氧化层形成相关的两个抛物线依赖关系，200小时后的重量增加为4.03 mg/cm，这表明与迄今为止的文献数据相比，它是最抗氧化的RHEAs之一。这项工作还可以为如何进一步开发RHEA以承受高温下的长期氧化提供见解。
