The High-Temperature Corrosion Behavior of Feconi-Based High-Entropy Alloys

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Project title

Code/計畫編號

MOST103-2221-E019-007-MY2

Translated Name/計畫中文名

鐵鈷鎳基高熵合金之高溫腐蝕行為研究

Project Coordinator/計畫主持人

Wu Kai

Funding Organization/主管機關

National Science and Technology Council

Department/Unit

Department of Optoelectronics and Materials Technology

Website

https://www.grb.gov.tw/search/planDetail?id=11277717

Year

2015

Start date/計畫起

01-08-2015

Expected Completion/計畫迄

31-07-2016

Bugetid/研究經費

1046千元

ResearchField/研究領域

材料科技

本計畫擬以兩年為一期，研究主題是探討「鐵鈷鎳基高熵合金之高溫腐蝕行為研究」，茲將各年度之研究要點分述如下: (1) 本研究第一年度將評估三種FeCoNi-基五元高熵合金(以FeCoNiCrAl、FeCoNiCrSi、以及FeCoNiAlSi為主) 的高溫腐蝕行為，結果將與FeCoNi等莫耳合金的腐蝕行為做比較，以瞭解不同元素添加對高熵合金抗蝕特性之差異。首先，對選定合金在600~900oC間的TGA中進行恆溫氧化(含不同氧分壓之氧氣及空氣)，研究重點是利用高靈敏之熱重分析儀(TGA)以連續監測氧化後的質量變化量，來探討合金氧化的動力學行為及確立氧化的反應機制，同時，利用水汽增濕控制器來探討水汽效應對氧化速率之快慢差異，並評估水汽效應對氧化膜附著性之差異。其次，本研究以將連續升/降溫的方式來探討循環氧化對合金氧化行為之影響，以評估高熵合金循環氧化之特性。另外，本研究也針對高熵合金表面披覆1~2 mg/cm2 之NaCl/Na2SO4 (含100/0, 50/50, 0/100之不同比例)進行600~800oC 之熱腐蝕研究。所有腐蝕實驗後之試片將分別利用X-光繞射分析儀及金相顯微(OM) 分析來探討腐蝕物組織及成分分布情形，並配合電子探測儀(EPMA)、掃瞄(SEM) 及穿透電子顯微鏡(TEM) 來分析腐蝕物形貌與腐蝕物空間分佈之差異。 (2) 本研究第二年度將彙整前一年度的研究成果及累積經驗，針對最佳的FeCoNi-基五元高熵合金進行成分微調以及添加微量的反應元素（如Y、 Zr或B等），擬將找出最佳的五元或六元高熵合金，深入瞭解其顯微組織之差異對高熵合金抗蝕特性之影響，並與前一年度之高熵合金進行差異性分析。本年度的恆溫氧化(含不同氧分壓之氧氣及空氣)、水汽效應之影響、循環氧化、以及熱腐蝕研究皆如第一年度相同；而所有腐蝕實驗後之試片分析亦如第一年度所述。This two-year research proposal is to study “the high-temperature corrosion behavior of FeCoNi-based high-entropy alloys”. The main goals of this research are annually described as follows; (1) The first-year proposal is to evaluate the corrosion behavior of three FeCoNi-based high-entropy alloys (HEAs), containing the nominal composition of FeCoNiCrAl, FeCoNiCrSi, and FeCoNiAlSi, and the results will be compared to those of FeCoNi equi-molar alloy for comparative purposes. The initial isothermal oxidation of the alloys will be tested in air and O2-containing atmospheres with various oxygen partial pressures at 600~900oC. The important feature of this work is to continuously monitor the mass change of the samples using high-sensitive thermal gravimetric analysis (TGA). The detailed oxidation kinetics and reaction mechanism will be studied. Secondly, the effect of water vapor on the oxidation rates of the HEAs will also be discussed using a humidity generator and controller. The presence of the water-vapor environment with respect to the scale adherence to the substrate will be explored. Thirdly, the cyclic oxidation of the alloys will be studied using TGA under an alternative heating and cooling process. The effects of the cyclic-oxidation on the oxidation behavior of the alloys will be further addressed. In addition, the hot-corrosion behavior of the alloys deposited with 1~2 mg/cm2 NaCl/Na2SO4 (at various ratios of 100/0, 50/50, 0/100) will also be carried out at 600~800oC. The characterization of the corroded samples will be performed using X-ray diffraction (XRD) and optical microscopy (OM) for the scale constitution and phases, electron probe micro-analyzer (EPMA) together with scanning and transmission electron microscopy (SEM and TEM) for the topography and cross-sectional scales with respect to the spatial distribution. (2) Based on the experiences and results in the first year, the better performance of the multiple-component HEAs (with five or six alloying compositions) will be further investigated in the second year. The optimal compositional adjustment and small additional amounts of reactive elements (Y, Zr, or B) will also be studied, particularly in their effects of microstructural difference on corrosion resistance of modified HEAs under the same corrosive environments as described in the first year. The characterization of the scales in this year will also be the same as that in the first year.

Keyword(s)

鐵鈷鎳基高熵合金
高溫腐蝕
恆溫氧化
水汽環境
循環氧化
熱腐蝕
反應機制

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The High-Temperature Corrosion Behavior of Feconi-Based High-Entropy Alloys

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