Characterization of chemical information and morphology for in‐depth oxide layers in decarburized electrical steel with glow discharge sputtering

Abstract

A combination of scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy with a sampling method by glow discharge sputtering was successfully employed to characterize the chemical information and microscopic features of oxide layers formed during decarburization annealing of electrical steel in the depth direction at high resolution. The discontinuous surface oxides consisted of SiO 2 , (Fe,Mn)SiO 3 /(Fe,Mn) 2 SiO 4 , and FeO. SiO 2 embedded in the (Fe,Mn) 2 SiO 4 at the surface may be developed by the preferential nucleation and growth kinetics. The discrete or often relatively spherical oxides of internal oxidation by the energetically favorable surface effect were identified as a mixture of SiO 2 and (Fe,Mn) 2 SiO 4 at a depth of~0.5 mm from the surface. The oxides of networks and small particles at a depth greater than~1 mm were solely silica, of which the morphologies were possibly caused by the enhanced diffusion of oxygen atoms and Si atoms at grain boundaries or sub-grain boundaries. The equilibrium and kinetic considerations served by theoretical calculations were introduced to understand the formation and behavior of the observed in-depth oxidation. Figure 6. Spectral line fit of high-resolution spectra for (a) O 1s peak and (b) Si 2p peak after 120 s sputtering of as-received surface; (c) O 1s peak and (d) Si 2p peak after 120 s sputtering of the specific surface C in Fig. 5.

Solid state amorphization in a thin Fe-Si-Mg-O surface film triggered by the reduction of elements from oxides in the temperature range of the α-γ transformation

“…The samples were subjected to decarburizing annealing for 8 minutes in a 75 %H 2 + 25 %N 2 atmosphere humidified to the dew-point temperature of +65°C [21][22]. After annealing, the carbon content did not exceed 0.002 wt.%.…”

“…The surfaces of the initial and heat-treated samples were studied under a scanning electron microscope using energy dispersive X-ray spectroscopy (EDX). An integral depth chemical analysis of the materials in the layers of the samples was carried using glow-discharge optical emission spectroscopy (GDOES) on a GDA-750 [18,21,25]. A Bruker D8 Advance diffractometer and an Anton Paar HTK 1200N thermal vacuum chamber were used to perform an X-ray diffraction analysis (XRD) of the samples using Co Kα -radiation in coldrolled (without coating) and heat-treated states (with coating).…”

“…It is noteworthy that GOES is a composite material consisting of a magnetic base (Fe-3 %Si) and an electrical insulation coating [17] represented by a multi-component film, which is formed on the surface as a result of several thermochemical operations [18]. Despite the fact that the main stages of the GOES production were developed quite a while ago [16,19 -20], some details of the coating formation process are yet to be properly studied [18,[21][22]. The small thickness of the coating of 0.5 -5 μm presents the main difficulty in the study of surface processes.…”

Quantitative determination of carbon concentration profiles by GD‐OES for the study of decarburization in low‐carbon steels

“…The resulting decarburized region changes the surface properties, which may contribute to the failure of the material . However, decarburization may be intentionally induced during annealing in an oxidizing atmosphere to minimize the carbon concentration near the surface …”

“…[3,4] However, decarburization may be intentionally induced during annealing in an oxidizing atmosphere to minimize the carbon concentration near the surface. [5][6][7] The decarburization mechanism can be separated into three simultaneous processes, i.e. the reaction of carbon at the surface, the carbon diffusion towards the surface, and the dissolution of carbides.…”