Abstract
The solubility of titanium nitride in liquid iron is described by the solubility product log([%Ti][%N])1 = −17040/T + 6.40 reported by Turkdogan. The solubility in δ ferrite measured by Kunze is log<[%Ti][%N])δ = −17205/T + 5.56. Combining the solubilities in both phases and the solubilities of nitrogen the distribution equilibrium of titanium can be derived. It is characterized by the thermodynamic distribution coefficient kδ/Io,Ti = [%Ti]δ/[%Ti] = 0.40. By zone melting and secondary ion mass spectrometry of the titanium distribution kδ/ITi = 0.53 was measured. An analysis of all known data led to kδ/Io,Ti = 0.40…0.50.Measurements of the TiN solubility in austenite by heat treatment were not significant. They led to distribution coefficients between 0.07 and > 1. By zone melting in a carburizing atmosphere a distribution coefficient kγ/ITi = 0.12 was measured. From a thermodynamic analysis performed by Ohtani et al., from the TiN solubility in the melt, and from the solubilities of nitrogen kγ/Io,Ti = 0.13 was deduced. Basing on the distribution equilibria of titanium and nitrogen and on the measured temperature dependence the solubility product log([%Ti][%N])γ = −15000/T + 4.06 was obtained.
Published Version
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