表面状态对DD6镍基单晶合金在950℃氧化行为的影响

采用X射线衍射、扫描电子显微镜及电子探针等分析手段,研究不同打磨表面状态(180^#、400^#、1000^#砂纸打磨和抛光)下DD6镍基单晶合金在950℃的氧化行为。表面状态对合金的氧化速率有重要的影响。随粗糙度增加,表面增重速率逐渐下降。抛光和1000#砂纸打磨的表面具有多层氧化膜结构,氧化膜从外表面向基体分别由NixCo1?xO、Cr-Co-rich、Ta-Cr-rich、Al2O3和无析出相区域组成;而在180^#和400^#砂纸打磨的表面,氧化膜由单一、连续的Al2O3组成。另外,在抛光和1000#砂纸打磨的表面,氧化动力学呈现两个阶段;而在180^#和400^#砂纸打磨的表面,并没有观察到氧化动力学转折点的出现。表面变形促进Al由内氧化向外氧化转变。

Effect of surface signature on oxidation behavior of DD6 alloy at 950℃

X-ray diffraction,scanning electron microscopy,and electron microprobe techniques were used to investigate the oxidation behavior of DD6 nickel-based single crystal alloys at 950℃ with different surface signature(ground to 180^#,400^#,and 1000^# and polished).The results show that the surface signature has a significant effect on the oxidation rate of the alloy.The mass gain rate of the specimens gradually decreases as the surface roughness increases.Multi-layers structure is developed on the surface after ground to 1000^# and polished.And the oxide film structure,from the top surface to the base metal,is NixCo1?xO,Cr-Co-rich,Ta-Cr-rich,Al2O3 and γ′-free zone.However,the oxide films only consist of a single Al2O3 layer of the alloy after ground to 180#and 400#.In addition,two stages are displayed in the oxidation kinetics of the alloy under the polished and 1000^# surface signature,whereas no turning point is observed under the 180^# and 400^# surface signature.Surface deformation promotes the transformation of Al from internal oxidation to external oxidation.And the morphology of Al2O3 has a significant role on the oxidation kinetics,oxide film evolution and oxidation mechanism.