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

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.