Solubility of Titanium Carbosulfide in Austenite

A titanium carbosulfide solubility product of log [Ti][C]0.5[S]0.5 = -14 646/T15.51 and a Gibbs free energy of formation for titanium carbosulfide of Δ°GTi4C2S2 = -1 121.9+0.196 T kJ/mol were calculated from dissolution temperature experiments using a series of titanium-modified secondary hardening ultra-high strength steels. The presence of other precipitates such as TiN, TiC and TiS could be neglected for this class of steels. The effect of the alloying additions on the activity of carbon and hence on the dissolution temperature of titanium carbosulfide was also found to not be significant for these steels. The experimentally determined solubility product and Gibbs free energy of formation are compared with previously published data for titanium carbosulfide.