STEM Analysis of the Transient Oxidation of a Ni± 20Cr Alloy at High Temperature

摘要: High-spatial scanning transmission electronmicroscopy (STEM) has been used to study the developmentof transient scales on a commercially available Ni-20Cralloy. The samples were examined usingelectron-transparent cross sections of metal and oxide foroxidation times between 0 30 min in furnace at950°C laboratory air. polishedto 1 μm diamond before oxidation, producing recrystallized grain structure within 100 nm ofthe surface. Upon initial scale consistedalmost exclusively chromia. However, at themetal-oxide interface, thin layers silica alumina detected. At longer oxidation times,(>5 min), localized thickening layerwas observed. With increased time, (>25min), these regions spread along metal-oxideinterface until an almost continuous layer hadformed. was present much shorteroxidation than reported by other workers, however,this may be because being undetectable using microprobe techniques. formedwas found adherent, although alloy containedsulfur did not contain reactive elements. However,sulfur segregate metal-oxide interface possibly presence amorphous layer.