The Importance of Operating Conditions and Parameters on Laser Alloying with Silicon During Surface Layer Modification of Nodular Iron

The main goal of this research was to characterize the influence of different cooling rates (generated by combination of laser treatment parameters) during laser alloying with silicon on the microstructure of the surface layer of nodular iron. The alloyed zones contain martensite, austenite, cementite and phases with Si such as C0.12Fe0.79Si0.09 and FeSi. The content of these phases depends on the laser heat treatment parameters. For example, in the case of the alloyed zone cooled at the rate of nearly 10(4)degrees C/s, observation revealed the presence of very-fine-crystalline microstructures characterized by high homogeneity, contrary to the zone cooled at a lower rate. The higher the cooling rate of the alloyed zone was obtained, the higher was the amount of C0.12Fe0.79Si0.09. The higher the silicon concentration in the alloyed zone, the higher the amount of FeSi. The hardness of the alloyed zone was increased along with the increasing cooling rate.