Environmental resistance of a Ti₂AlC-type MAX phase in a high pressure burner rig

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• 作者：James L. Smialek ^{James.L.Smialek@nasa.gov" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Ti2AlC MAX phase ; Oxidation ; Scale volatility ; Water vapor ; Burner rig
• 刊名：Journal of the European Ceramic Society
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：37
• 期：1
• 页码：23-34
• 全文大小：4223 K

文摘

Alumina-forming commercial Ti₂AlC (MAXthal 211)™ phase samples were exposed in a jet-fueled, high pressure burner rig (HPBR) at 1100°, 1200°, and 1300 °C, operating at 6 atm (bar) and 25 m/s, in ∼10% water vapor. Weight change exhibited a rapid initial uptake associated with a TiO₂ transient phase followed by cubic kinetics of a slow-growing α-Al₂O₃ underlayer. The cubic rate constants, k_c, were approximately 20% of those measured in static thermo-balance furnace tests. A small recession rate of −0.012 mg/cm²/h was measured at 1300 °C for a pre-oxidized sample. The loss rate was ∼15% that observed for SiO₂ scales subject to volatile Si(OH)₄ formation for SiC tested under similar conditions. These kinetic features were fitted in a modified cubic-linear law. From thermodynamic, XRD, and SEM analyses, it is proposed that volatile TiO(OH)₂ was formed by the reaction of water vapor with TiO₂ and TiAl₂O₅ outer layers.