Mar-M247高温合金900℃下的氧化行为研究

Oxidation Behaviour of Mar-M247 Super Alloy at 900℃

为探究燃气轮机用高温合金在服役环境中组织结构变化及其对合金氧化性能的影响,利用扫描电镜和能谱表征了MarM247镍基高温合金在900℃长时效后的显微组织,研究其在1000、3000、5000、8000h时效后的氧化性能。结果表明,时效1000h的氧化初期合金表面氧化物相变化较快,Al_(2)O_(3)氧化膜不完整,氧化膜增厚较快;随着氧化时间增加,富W氧化膜内生成大量孔洞和岛状不连续WO2,导致内层Al_(2)O_(3)膜界面发生剥落,外层氧化膜结构得到简化,内层Al_(2)O_(3)膜增厚且变得均匀;时效8000h后氧化层总厚度和内层Al_(2)O_(3)膜变化幅度明显减小,整个氧化膜结构趋于稳定。由于内层保护性Al_(2)O_(3)膜的增厚和结构均匀连续,使得合金的氧化性能提高。

In order to explore the structural transformation of superalloys for gas turbines in the service environment and their effects on the oxidation performance of the alloys,the microstructure of the Mar-M247 nickelbased superalloy after long-term aging at 900℃was characterized by scanning electron microscope and energy dispersive spectroscopy,and the oxidation performances were investigated after different aging time.The results reveal that surface oxide phases of the alloy is changed fast and the oxide structure is complex at the initial stage of aging 1000 h.The Al_(2)O_(3) film is incomplete with thickness increasing obviously.As the oxidation time increases,a large number of holes and discontinuous island-like WO2 are generated in the W-rich film,Leading to the peeling of the inner Al_(2)O_(3) film interface.The structure of outer oxidation film is simplified and the inner Al_(2)O_(3) film grows and becomes uniform.After aging for 8000 h,the thickness of whole oxidation film and rangeability of the inner Al_(2)O_(3) film are decreased significantly.The whole oxidation structure tends to be stable.Due to the thickening of the protective Al_(2)O_(3) film and homogeneous continuous structure,the oxidation performance of MarM247 superalloy is optimized.