Study on the High-Temperature Oxidation of Fenicral-Based High-Entropy Alloys

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Project title

Code/計畫編號

MOST105-2221-E019-003

Translated Name/計畫中文名

鐵鎳鉻鋁基高熵合金之高溫氧化研究

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=11879952

Year

2016

Start date/計畫起

01-08-2016

Expected Completion/計畫迄

31-07-2017

Bugetid/研究經費

1216千元

ResearchField/研究領域

材料科技

本研究計晝擬以兩年為一期，主題是探討「鐵鎳鉻鋁基高熵合金之高溫氧化研究」，茲將各年度之研究要點分述如下： (1)第一年度將評估四種FeNiCrAl-基五元系高熵合金（以 FeNiCrAlCex、 FeNiCrAlNbx、FeNiCrAlSix以及 FeNiCrAlYx為主，其中 x 可為 0.25~ 0.50)的高溫氧化行為，結果將與FeCrAl及FeNiCrAl兩種等莫耳合金的氧化行為做比較，以瞭解添加不同元素對高熵合金抗氧化特性之差異。首先，對選定合金在600〜900°C間的TGA及橫式高溫爐中進行恆溫空氣（含乾式及水汽環境）、不同氧分壓之氧氣以及CO2/CO混和氣的氧化；研究重點是利用連續監測之高靈敏度熱重分析儀(TGA) 以及橫式高溫爐監測氧化後單位面積之質量變化量，來探討合金在不同含氧氣氛及水汽效應下的氧化動力學、反應機制及氧化膜附著性之差異。另外，本研究也針對高熵合金進行600~ 750oC高壓蒸汽環境之蒸汽氧化研究(steam oxidation)。所有氧化後之試片將分別利用光繞射儀(XRD)及光學顯微鏡(OM)來分析氧化生成物的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)來探討氧化物形貌與其空間分佈之差異性。 (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FeNiCrAlMx-基五元高熵合金進行成分微調，並添加微量的特性元素（如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氧化特性之效應，並與前一年度之高熵合金進行差異性分析。另外，本年度的研究重點更將探討連續升/降溫方式的循環氧化（例如，高溫600%，而低溫300。匚各持溫兩小時為一次升/降溫循環）對合金氧化行為之影響，以評估高熵合金循環氧化之特性；相關的氧化氣氛環境及氧化後之試片分析皆如第一年度所述如。This two-year research proposal of “Study on the high-temperature oxidation of FeNiCrAl-based high-entropy alloys” is proposed. The main goals of this proposal are annually described as follows; (1) In the first year, the oxidation behavior of four FeNiCrAl-based quinary high-entropy alloys (HEAs), containing the nominal composition of FeNiCrAlCex, FeNiCrAlNbx, FeNiCrAlSix, and FeNiCrAlYx (where x could be 0.25〜0.50) is studied. For comparison, the results will be compared to those of FeCrAl and FeNiCrAl equi-molar alloys to understand the additional-element effects on the oxidation kinetics of selected HEAs. The isothermal oxidation of the alloys will be studied in dry and wet (water-vapor environment) air, O2-containing atmospheres with various oxygen partial pressures, and CO2/CO mixed gases with various ratios at 600 〜900oC. The important feature is to apply a continuously high-sensitive thermal gravimetric analysis (TGA) and a horizontal tube-furnace to monitor the mass change per sample area after oxidation. The detailed oxidation kinetics, reaction mechanism, and scale adherence to the substrate will be studied typically when the water-vapor environment is present. In addition, the steam oxidation of the selected alloys will also be studied in a high-pressure steam-environment at 600〜750oC. The characterization of all the oxidized samples will be performed using XRD and OM for the scale constitution and phases, EPMA together with 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 special-purpose elements (Zr or B) will also be studied, particularly in their effects of microstructural difference on oxidation resistance of modified HEAs under the same oxidation environments of the first year. In addition, the typical cyclic oxidation (e.g. a cyclic exposure contained for a 2-hour period at 600oC and another 2-hour period at 300oC) of the selected alloys will be further addressed under an alternative heating and cooling process. The characterization of the scales in this year will also be similar to that in the first year.

Keyword(s)

鐵鎳鉻鋁基髙熵合金
髙溫氧化
恆溫氧化
水汽環境
蒸汽環境
循環氧化
反應機制
FeNiCrAlMx-based high-entropy alloys
high-temperature oxidation
isothermal oxidation
water-vapor environment
steam oxidation
cyclic oxidation
reaction mechanism

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Study on the High-Temperature Oxidation of Fenicral-Based High-Entropy Alloys

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