钽双极微弧氧化陶瓷膜层的抗高温氧化性能

High-temperature oxidation resistance of bi-electrodes micro-arc oxidation ceramic coating on tantalum

在硅酸盐体系、双脉冲恒压模式下,采用双极微弧氧化和传统微弧氧化技术在金属钽表面原位生长陶瓷膜层。使用测厚仪进行膜层厚度测试。通过X射线衍射仪、扫描电镜与能谱仪对膜层相组成、表面形貌与元素含量进行分析。利用高温氧化增量试验研究膜层的抗高温氧化性能。结果表明,传统微弧氧化和双极微弧氧化反应后生成膜层的相组成为Ta2O5相。传统微弧氧化模式下生成的膜层厚度要大于双极微弧氧化模式下生成的膜层。经过高温焙烧后膜层表面相较焙烧前更为平整,说明氧化物经焙烧后出现熔融塌陷,且有明显烧结痕迹,残留一些类似火山口状小孔。高温焙烧使氧化物挤压膨胀,出现微裂纹。与基体相比,微弧氧化的试样具有更好的抗高温氧化性能。双极微弧氧化技术原位生成的陶瓷膜层相较于传统微弧氧化技术,高温氧化质量增加更少,抗高温氧化性能更优。

Under silicate system and dual pulse constant pressure mode,the bi-electrodes micro-arc oxidation and traditional micro-arc oxidation techniques were used to grow ceramic coating in situ on the surface of tantalum metal.The thickness of the coating was tested by using thickness gauge.The phase composition,surface morphology and element content of the coating were analyzed by using X-ray diffractometor,scanning electron microscope and energy dispersive spectrometer.The high-temperature oxidation resistance of the coating was studied by using high-temperature oxidation mass gain test.The results indicate that the phase composition of the coating formed by traditional micro-arc oxidation and bi-electrodes micro-arc oxidation reactions is Ta2O5 phase.The coating thickness generated under traditional micro-arc oxidation mode is greater than that under bi-electrodes micro-arc oxidation mode.After high-temperature oxidation,the surface of the coating is smoother compared to that before oxidation,indicating that the oxides melt and collapse after oxidation,and there are obvious sintering traces,with some remained volcanic crater-like small pores.High temperature oxidation causes the oxide to extrude and expand,resulting in microcracks.Compared with the matrix,the specimens subjected to micro-arc oxidation have better resistance to hightemperature oxidation.The ceramic coating generated in situ by bi-electrodes micro-arc oxidation technology has less high-temperature oxidation mass gain and better resistance to high-temperature oxidation compared to that of traditional micro-arc oxidation technology.