Characterization of surface oxides on water-atomized steel powder by XPS/AES depth profiling and nano-scale lateral surface analysis

• Published in: Applied surface science Vol. 268; pp. 496 - 506
• Main Authors: Chasoglou, D., Hryha, E., Norell, M., Nyborg, L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2013; Elsevier
• Subjects: Alloyed sintered steels; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Depth profiling; Exact sciences and technology; HR SEM + EDX analysis; HR SEM plus EDX analysis; Physics; Surface coverage; Surface oxides; Water atomized powder; XPS/AES analysis; Surface coverage; Surface oxides; Alloyed sintered steels; XPS/AES analysis; Water atomized powder; HR SEM+EDX analysis; Depth profiling; Water; Scanning electron microscopy; Sintered alloy; X-ray spectra; Surface analysis; Coverage rate; Dispersive spectrometry; AES; HR SEM + EDX analysis; Depth profiles; X-ray photoelectron spectra
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2012.12.155

► More than 90% of the powder surface is covered by thin (∼6nm) Fe-oxide layer. ► Fine oxides rich in Cr, Mn and Si are also present on the powder surface. ► Cr-oxide is present only in the fine oxides and not in the surface oxide layer. ► 2 categories of the fine oxides are recognized according to composition and size. ► In the agglomerates the oxide phases appear as “glued” adjacent particulates. Characterization of oxide products on the surface of water-atomized steel powder is essential in order to determine the reducing conditions required for their removal during the sintering stage which in turn will result in improved mechanical properties. Pre-alloyed powder with 3wt% Cr and 0.5wt% Mo was chosen as the model material. Investigation of the powder surface characteristics with regard to composition, morphology, size and distribution of surface oxides was performed using X-ray photoelectron spectroscopy, Auger electron spectroscopy and high resolution scanning electron microscopy combined with X-ray microanalysis. The analysis revealed that the powder is covered by a homogeneous (∼6nm thick) Fe-oxide layer to ∼94% whereas the rest is covered by fine particulate features with the size below 500nm. These particulates were further analyzed and were divided into three main categories (i) Cr-based oxides with simultaneous presence of nitrogen, (ii) Si-based oxides of “hemispherical” shape and (iii) agglomerates of the afore mentioned oxides.