Regular Article

Effect of rare earth addition on the heterogeneous nucleation behavior of TiN in duplex stainless steel

State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 100083 Beijing, PR China

Received: 5 November 2016
Accepted: 16 August 2017

Abstract

The effect of rare earth addition on the heterogeneous nucleation behavior of TiN was investigated by analyzing inclusions behaviors in a commercial duplex stainless steel. The results showed that the rare earth oxides and oxysulfides could induce the precipitation of fine TiN particles to form the composite TiN (TiN + cores) with a size less than 4 µm. It was found that TiN was more likely to precipitate on the rare earth oxides than rare earth oxysulfides, the number of composite TiN with rare earth oxides core was larger than composite TiN with a rare earth oxysulfides core. In addition, more than 60% rare earth oxides were completely surrounded by TiN, further indicating that rare earth oxide was favor to induce the precipitation of TiN. When a_[Ti] and a_[Ce] met the relationship of  rare earth oxides Ce₂O₃ could stably form to promote the precipitation of fine TiN particles. Decreasing the sulphur content of steel was an efficient way to form Ce₂O₃ and suppress the formation of Ce₂O₂S.