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 th e sessile drop technique at 1823, 1873, and 1923 K in a purified argon atmo sphere. The experimental data indicate lowering of surface tension values f or alloys with low carbon and oxygen contents relative to the corresponding ternary Fe-S-O system of comparable compositions. The data exhibit an incr easing trend of the surface tension values as a function of carbon and oxyg en contents and temperature of the melt, Modified Butler's equations have b een used in conjunction with the consistent thermodynamic relations for a d ilute quaternary system to calculate the surface tensions and adsorption fu nctions of the system, The calculated values are in excellent agreement wit h those of the experimental data for compositions having lower oxygen at 18 23 K, however, the values for the alloys containing higher oxygen contents depart from those of the experimental data. The calculated surface 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 invo lved in the calculations as discussed in the text.