High-temperature wettability and structure of the TiO2–MnO–SiO2–Al2O3 welding flux system

• Compositional effect on wettability properties of silicate based slag system at high temperature using structural analysis
• Higher TiO2 content decreased the interfacial tension between the flux and substrate
• Higher Al2O3 content decreased the interfacial tension between the flux and substrate
• Both the O− and O2− oxygen anions affect the interfacial tension

The effect of TiO2/SiO2 and SiO2/Al2O3 ratio on the wettability of the TiO2–MnO–SiO2–Al2O3 quaternary welding flux system was studied using the sessile drop method by measuring the contact angle at the liquid/solid interface. The contact angle was measured at 1773 K to determine the relationship between wettability and flux structure, which is affected by the flux composition. The surface and interfacial tensions of the TiO–MnO–SiO2–Al2O3 flux system were calculated using Boni's equation and Young's equation, respectively, based on the measured contact angle. The adhesion energy, which corresponds to the energy required to separate the flux from a substrate, was calculated using Dupre's equation. The interfacial tension between the liquid flux and Pt-10Rh decreased and the surface tension increased with higher TiO2 and Al2O3. The results of the Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses of as-quenched fluxes from 1773 K also support the structural relationship with the wettability. It was found that both O− (non-bridged oxygen) and O2 − (free oxygen) affect the interfacial tension between the flux and the substrate.