The solidification characteristics of laser surface-remelted Fe-12Cr-nC alloys

Laser surface remelting experiments have been carried out in Fe-12Cr-nC all oys in order to characterize the effect of growth velocity on the microstru ctural scale and the mode of solidification. Two types of growth morphologi es have been observed: cellular/dendritic at a low carbon content and dendr itic at a high carbon content. The existing band of primary spacings for a given solidification condition was characterized and confirmed. A recent an alytical expression by Hunt and Lu for cellular and dendritic structures wa s compared to the experimentally measured primary arm spacings, and a good agreement was obtained. Further, the relationship between the primary spaci ng and the dendrite-tip radius was also determined and compared to the expe rimental results using a simple geometrical consideration between the dendr ite-tip radius and the primary spacing. Finally, a theoretical microstructu ral map was constructed and compared to the experimental results. A good ag reement between the observed and the calculated phases was obtained.