高铌γ-TiAl合金表面微弧氧化陶瓷涂层的耐蚀性及高温氧化行为

Corrosion Resistance and High-temperature Oxidation Behavior of Micro-arc Oxidation Ceramic Coating on High Niobium γ-TiAl Alloy

利用微弧氧化技术(MAO)在硅酸钠和氢氧化钾溶液中对高铌γ-TiAl合金表面原位生长陶瓷涂层以提高γ-TiAl合金的抗高温氧化性能。采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、X射线光电子能谱(XPS)、电化学工作站和箱式电阻炉高温氧化测试分析涂层的表面及截面形貌、相组成、元素化学结合状态、耐蚀性和高温氧化行为。XRD和XPS结果表明,陶瓷涂层主要由Al2TiO5、SiO2和Nb2O5组成。涂层与基体界面结合良好,厚度约2.15μm。高铌γ-TiAl合金经微弧氧化处理后,在3.5%NaCl溶液中的腐蚀电流降低近1个数量级。微弧氧化处理试样在800~900℃中的氧化增重仅为基体的8.9%~37.5%。微弧氧化陶瓷涂层将基体的氧化激活能从247.79 kJ/mol增加到涂层试样的574.41 kJ/mol。

The micro-arc oxidation(MAO) technique was used to prepare in-situ ceramic coating on the surface of high niobium γ-TiAl alloy in sodium silicate and potassium hydroxide solution to improve the high-temperature oxidation resistance. The SEM, XRD, XPS, electrochemical workstation and box-type resistance furnace high-temperature oxidation test were used to analyze the surface and cross section morphologies, phase composition, elemental chemical bonding state,corrosion resistance and high-temperature oxidation behavior of the coating, respectively. The results of XRD and XPS show that the ceramic coating is mainly composed of Al2TiO5, SiO2 and Nb2O5. The coating has a good interface with the substrate,with a thickness of 2.15 μm. After micro-arc oxidation treatment, the corrosion resistance of high niobium γ-TiAl alloy in 3.5%NaCl solution is improved by nearly one order of magnitude. The oxidation weight gain of the coated sample at 800-900 ℃ is only 8.9%-37.5%. The oxidative activation energy of the uncoated sample increases from 247.79 kJ/mol to 574.41 kJ/mol for the coated sample due to the formation of the MAO coating.