Insights into the tribochemistry of sliding iron oxide surfaces lubricated by sodium silicate glasses: An ab initio molecular dynamics study

Tribochemistry and Lubrication of Alkaline Glass Lubricants in Hot Steel Manufacturing

“…In fact, the confined system of Na 2 O.SiO 2 and Na 2 O•2SiO 2 displayed this layer at surface-silicate interfaces due to the migration of Na atoms out of the glass network to adsorb onto Fe 2 O 3 (0001) surfaces. The rearrangement of sodium elements promoted the polymerization process in the middle of the glass lubricant [37]. When considering the influence of a shearing effect on silicate glass, Tran et al [37] confirmed the previous observation by Ta et al [36] for sodium borate glass that silicate lubricants with a higher Na 2 O concentration provided a better tribological performance than the lower one because of it greater adhesive strength.…”

“…Similarly, with borate glass [35], the level of polymerization increased when the proportion of Na 2 O decreased from 50% to 33% [37]. Silicate glass also formed covalent bonds between O nb and surface iron atoms, while some Si atoms formed direct covalent bonds with surface oxygen [37]. As presented in Figure 6, an AIMD simulation at 1361 K and 1 GPa demonstrated a continuous process of polymerization and depolymerization in the glass lubricant.…”

“…surface iron atoms, while some Si atoms formed direct covalent bonds with surface oxygen [37]. As presented in Figure 6, an AIMD simulation at 1361 K and 1 GPa demonstrated a continuous process of polymerization and depolymerization in the glass lubricant.…”

“…Similarly, with borate glass [35], the level of polymerization increased when the proportion of Na 2 O decreased from 50% to 33% [37]. Silicate glass also formed covalent bonds between O nb and surface iron atoms, while some Si atoms formed direct covalent bonds with surface oxygen [37].…”

“…It is important to investigate the chemical mechanism of how a glassy lubricant works when it is applied in practice at high temperature and pressure in metal forming. We have carried out some theoretical investigations of the adsorption and thin film lubrication of Na [25,35,36], as well as sodium silicate, Na 6 Si 2 O 7 , on iron and iron oxide surfaces [37,38]. These studies have overcome the drawbacks of previous experiments and provided a deep insight into the chemical reactions in the tribofilm.…”