Effect of Ce content on precipitation behavior in S31254 super austenitic stainless steel

Abstract

The precipitation of Cr- and Mo-rich σ phases will seriously deteriorate the corrosion resistance and mechanical property of super austenitic stainless steel S31254. The precipitation of σ phase in S31254 containing B and Ce can be effectively inhibited by heat treatment to regulate trace elements. In this study, slow cooling combined low-temperature diffusion treatment (SCLDT) was adopted in S31254 containing B and Ce. Furthermore, the role of Ce was explored by comparing the precipitation behavior of samples with different Ce content. The results show that this new heat treatment strategy can better exert the inhibition effect of B and Ce on the precipitation of σ phase, and the inhibition effect is more obvious when the content of Ce is higher. It was found that the distribution of elements in the adjacent area of Ce at the GBs was almost the same as that in the matrix, which indicated that Ce could inhibit the formation of the precipitates along the GBs, and thus resulting in the precipitates distributed discontinuously. Besides, the B element was soluble in Mo-rich precipitates, and the B-containing precipitates was distributed in serrated pattern at GBs. In the 50Ce samples, serrated precipitates are more likely to form at the GBs, and the amount of precipitates was significantly reduced and discontinuities increased. Due to the homogeneous distribution of Cr in the serrated precipitates and their adjacent matrix zones, the phase interface has better resistance to intergranular corrosion.