Thermodynamics of surfaces and adsorption in the Fe-C-S-O system

Surface tension experiments have been conducted on Fe-C-S-O alloys using the sessile drop technique at 1823, 1873, and 1923 K in a purified argon atmosphere. The experimental data indicate lowering of surface tension values for alloys with low carbon and oxygen contents relative to the corresponding tenary Fe-S-O system of comparable compositions. The data exhibit an increasing trend of the surface tension values as a function of carbon and oxygen contents and temperature of the melt. Modified Butler’s equations have been used in conjunction with the consistent thermodynamic relations for a dilute quaternary system to calculate the surface tensions and adsorption functions of the system. The calculated values are in excellent agreement with those of the experimental data for compositions having lower oxygen at 1823 K, however, the values for the alloys containing higher oxygen contents depart from those of the experimental data. The calculated surfact tension values agree within 150 mN/m with those of the experimental data at 1873 K. The agreement, in general, has been favorable despite the constraints involved in the calculations as discussed in the text.