WEB Size Distribution and Chemical Composition Determination of Ti/NbCN Nanoparticles Extracted from Microalloyed Steels
Microalloyed steels find applications in numerous industrial sectors for the production of structural parts due to their compelling mechanical properties and good weldability. Such steels contain small amounts (< 0.5 wt%) of niobium, titanium, vanadium, or combinations of the three as alloying elements. If the parameters during steel production are adequate, they lead to the formation of desirable precipitates that contain titanium, niobium, vanadium, carbon and/or nitrogen. The microstructure and hence the mechanical properties of microalloyed steels, depend upon precipitate size distribution. Analysing the carbonitrides’ particle size distribution is therefore of great interest for material engineering.
Particle size distributions (PSDs) in steel are traditionally assessed by investigating electron transparent foils or carbon replica using electron microscopy. Such techniques only give access to a small number of particles and hence may not be representative of the sample volume. We use an alternative, volume-based method to investigate the particle size of carbonitrides contained in microalloyed steels. The particles are extracted from a steel sample with a representative volume by chemical dissolution of the iron matrix. After purification of the obtained suspension the size distribution and chemical composition of the extracted particles is determined by Scanning Transmission Electron Microscopy (STEM)/Energy-Dispersive X-Ray Spectroscopy (EDS), Single-Particle Inductively Coupled Plasma Mass Spectrometry (SP-ICP-MS) and Analytical Ultracentrifugation (AUC).
Here, we evaluate the suitability of the different characterization techniques for providing a complete and statistically meaningful analytical picture of the extracted particles. We compare the obtained datasets, discuss the limitations related to the techniques employed to determine PSDs and chemical compositions of the carbonitride nanoparticles and present the most adequate characterization technique combination.