FE-SEM Study of Fine Nb Precipitates in Carbon Extraction Replicas
Precipitation strengthening is an important parameter controlling the mechanical properties of low carbon steels. These precipitates are very fine and are normally analyzed using either thin foils or carbon extraction replicas under a transmission electron microscopy (TEM). In this work, field emission gun scanning electron microscope (FE-SEM) was applied successfully in the characterization of niobium (Nb) carbo-nitride (C,N) precipitates using carbon extraction replicas. FE-SEM observation of high strength linepipe steel replicas before and after aging at 400°C for 1 hr confirmed the presence of Nb(C,N) precipitates in ferrite. The FE-SEM could analyze small particles (below 50 nm) embedded in the steel but the analysis had to be carried out at low voltages to maximize spatial resolution resulting in a poor signal. However, carbon extraction replicas in the FE-SEM can be analyzed using high voltages, since the interaction volume effect is no longer a problem.
J.M. Rodriguez-Ibabe, I. Gutiérrez, B. López and A. Iza-Mendia
R. Varano et al., "FE-SEM Study of Fine Nb Precipitates in Carbon Extraction Replicas", Materials Science Forum, Vols. 500-501, pp. 663-668, 2005