固體滲鋁高熵合金之高溫氣化性質研究

A Study on the High Temperature Oxidation Behaviors of Pack Aluminized High Entropy Alloys

高熵合金自1995年發展至今，其諸多優異性質已獲得產學研界之重視。經研究發現高熵合金具有優良的高溫強度、罕見的高溫析出硬化現象與極優越的耐高溫氧化能力。本研究針對成分為16.89% Fe - 35.06% Cr - 10.11% Al - 22.12% Ni - 15.79% Co（編號9416）與21.66% Fe - 22.57% Cr - 9.37% Si - 9.76% Al - 21.36% Ni - 15.25% Co （編號9417） （皆為at%）之兩種高熵合金進行900℃，4小時之固體滲鋁處理之後，表面分別生成平均厚度26μm與20μm之（Ni,Co,Cr,Fe）Al相鋁化層。基材與鋁化處理之高熵合金進行1100℃，196小時之恆溫氧化試驗發現，固體滲鋁處理之合金能有效生成緊密附著之氧化鋁保護層，因而提昇高熵合金之高溫抗氧化性質。本研究發現兩種高熵合金鋁化層表面均因為高溫氧化導致生成硬度較低之脫鋁層，合金內部基材組織除了產生較硬析出相之外，其餘組織之硬度均產生軟化現象。

Many efforts have been devoted to the High Entropy Alloys (HEA) due to their excellent properties and performance since 1995. It has been found that the HEA exhibits sufficient high temperature strength, unusual high temperature precipitation behavior and excellent high temperature oxidation resistance. In this work, two HEAs, #9416 and #9417, with the following chemical compositions: 16.89% Fe - 35.06% Cr - 10.11% Al - 22.12% Ni - 15.79% Co and 21.66% Fe - 22.57% Cr - 9.37% Si - 9.76% Al - 21.36% Ni - 15.25% Co (in at%), respectively, had been pack aluminized at 900 ℃ for 4 hrs. The (Ni,Co,Cr,Fe)Al layers around 25 μm and 20 μm in thickness, respectively, were observed on surfaces of #9416 and #9417 alloys. Protective and adherent alumina scale was found on both surfaces of the aluminide layers after oxidized at 1100 ℃ for 196 hrs. A better high temperature oxidation resistance was thus achieved by the aluminizing process. It is also concluded that an aluminum depletion layer with lower hardness was formed on the outermost surface of the aluminide layer, which was induced by the outward diffusion of aluminum during high temperature oxidation. In addition, except some precipitation phases, the hardness of HEA substrates decreases after high temperature oxidation tests.