(大连理工大学 材料科学与工程学院,大连 116024)
摘 要: 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。
关键字: 镍基单晶合金;氧化;表面状态;氧化膜;动力学;变形
(School of Materials Science and Engineering,Dalian University of Technology, Dalian 116024, China)
Abstract: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.
Key words: nickel-based single alloy; oxidation; surface signature; oxide film; kinetics; deformation