Contribution of Sodium Metasilicate to the Diffusion of Mn in Steel under Tribological Contact at High Temperatures

Abstract

The environmentally friendly sodium metasilicate is regarded as one of the promising lubricants for hot metal formation because of its excellent thermal stability and unique physical chemistry property. This work aims to reveal how alkaline silicate reacts with manganese (Mn) in mild steel during tribological contact at high temperatures. The results suggest that the melted sodium metasilicate contributes to the diffusion of Mn from mild steel because of the combined effects of the chemical potential gradient and the different oxidation states of Mn in the steel substrate and melts. The hierarchical structure of the tribo-interface indicates that a Mn-rich layer containing fingerlike and mushroomlike oxides, such as Mn 2 O 3 , NaMnO 2 , and MnFe 2 O 4 , exists between the iron oxide scale and the sodium-rich layer, which acts as a barrier to the inward diffusion of oxygen.

Tribochemistry and Lubrication of Alkaline Glass Lubricants in Hot Steel Manufacturing

“…Sodium metasilicate (Na 2 SiO 3 •5H 2 O), having a relatively high melting point (920 • C), has proven to be an effective lubricant around 1000 • C [26,27]. The silicate melt stimulates the outward migration of Mn from a steel bulk to the sliding surfaces, which, in combination with Na adsorption, forms a unique tribofilm layer [28].…”

Molecular Dynamics Simulations of Nanolubricant Films of Alkali Glasses under Sliding Asperity Contacts

“…In contrast, silicate outperforms the others at a higher temperature range. 5 Many experimental works have been performed to investigate the tribological performance of these lubricants, yet there is no study to compare these lubricants under the same condition at the nanoscale. This work compares the tribological performance of sodium phosphate and silicate glasses by means of a reactive molecular dynamics (MD) simulation.…”

“…15,16 In comparison with phosphate glass, sodium silicate lubricants performed effectively at a higher temperature. 5,17 However, the friction increased when the temperature rose above 1000 °C. 17 This tribofilm did not only reduce the friction and wear effectively but also simultaneously provided an antioxidation resistance because the sodium silicate molecules adsorbed chemically onto the iron/iron oxide surface by forming multiple Fe−O nb (nonbridging oxygen O nb ) bonds with a stronger covalent characteristic compared with the Si−O.…”

Evaluating the role of composition and local structure on alkali out‐diffusion in glasses for thin‐film solar cells

“…Recently, Neeway et al have suggested that solid‐state diffusion occurs via ion exchange between other available cations at the interface between glass/thin film, and the alkali‐ion exchange rate was determined by the local structure of the glass involving the alkali ion and its role therein 22 . For instance, the diffusion of Mn from crystalline steel substrate to amorphous sodium metasilicate melt lubricated on its surface is attributed to the chemical potential gradient existing between the two structures 26 . Mansas et al elucidated the complexity of glass network and composition in diffusion/water transport.…”

“…22 For instance, the diffusion of Mn from crystalline steel substrate to amorphous sodium metasilicate melt lubricated on its surface is attributed to the chemical potential gradient existing between the two structures. 26 Mansas et al elucidated the complexity of glass network and composition in diffusion/water transport. While the presence of calcium strengthened the glass network and reduced the density of bottlenecks to enhance diffusion, the introduction of boron caused the chemical interaction among H 2 O molecules, Ca and the network former of the glass matrix.…”