Nitride Inclusion Evolution During Unidirectional Solidification of Fe-18Cr-2Mo Alloy

抄録

Titanium nitride (TiN) is detrimental to the mechanical properties of steel products and should be properly controlled. For this purpose, the precipitation and evolution of nitride inclusions during the unidirectional solidification of Fe-18Cr-2Mo alloy simulating stainless steel SUS444 were studied using thermodynamic calculations and experimental methods. The relationship between inclusion evolution and solid fraction (f_s), solidification rate, and especially dendritic microstructure was analyzed. (Ti,Nb)N was revealed to be the major inclusion type in all samples. Inclusion number density increased and peaked at intermediate f_s and then decreased towards unity. Cooling rate had limited influence on number density and size variation in the range between 1.25 and 20 K/min. Nitride average composition was found to evolve from Ti_0.75Nb_0.25N to TiN throughout the solidification process.