Synthesis and nanoindentation of calcium-silicate inclusions in iron

Non-metallic inclusion formation in iron-based alloys are an inevitable consequence of the steel production process. Although the inclusion content of commercial steels is reduced to around 0.1 wt.%, the detrimental effects of inclusions on the alloy mechanical properties are still present. Oxide inclusions are formed during the deoxidation process of steel, which consists of adding deoxidizing agents (like Si, Al, Mn, etc.) with high-affinity for dissolved oxygen in the iron matrix. Oxide inclusions with hardness and elastic modulus notably different that those of the iron matrix, tend to be detrimental due stress concentrations associated with the inclusion-matrix mistmatch that arise under loading conditions.

After the deoxidization with Si and Al, either silica (SiO2), alumina (Al2O3) or mixed oxides forms, which are solid inclusions in the liquid steel and can cause manufacturing issues, like nozzle clogging during continuous casting. By adding Ca, different Ca-silicate and Ca-aluminate compositions can form, offering a landscape of inclusions compositions and mechanical properties that can be of interest. Adding Ca is however challenging because of its high vapor pressure and reactivity.

The main goal of this semester project is to produce calcium-silicate inclusions based on the CaO – SiO2 pseudo-binary phase diagram that can be tested for their local mechanical properties (hardness and elastic modulus) by nanoindentation. Accordingly, the student will be involved in the production of iron alloys containing calcium-silicate inclusions using laboratory induction and arc melting techniques. The analysis of the samples will be carried out using standard metallographic techniques, including optical microscopy and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS).

Project supervisors: Sandor Lipcsei, David Hernández
Contact: [email protected]