The Effect of B on the Co-Segregation of C-Cr at Grain Boundaries in Austenitic Steels

In austenitic steels, the co-segregation of C and Cr at grain boundaries can result in the formation of Cr23C6. However, the addition of B to steels can effectively reduce the amount of Cr23C6 formed and inhibit its ripening in experiments, simultaneously transforming it into Cr-23(BC)(6). Therefore, the effect of B on the co-segregation of C and Cr at the & sigma;5(210), & sigma;9(221) and & sigma;11(113) grain boundaries in austenitic steels was investigated using density functional theory. The results indicate that B, C, and Cr all tend to segregate at the three grain boundaries, with B and C showing a stronger segregation tendency. Furthermore, co-segregation of C and Cr with short distances occurs readily at the & sigma;5(210), & sigma;9(221) and & sigma;11(113) grain boundaries. The presence of B at grain boundaries can impede the segregation of Cr, particularly at the & sigma;9(221) and & sigma;11(113) grain boundaries. When B is pre-segregating at the & sigma;5(210) grain boundary, B, C, and Cr tend to co-segregate at the grain boundary. The grain boundary B hinders the accumulation of Cr near it for most grain boundaries, thereby inhibiting the co-segregation of Cr and C, making it difficult for B, C, and Cr to aggregate at most grain boundaries. This is beneficial for controlling the nucleation of Cr-23(BC)(6).