Mathematical modeling of localized melting around graphite nodules during laser surface hardening of austempered ductile iron

An attempt has been made to mathematically predict the optimum conditions o f laser surface hardening (LSH) of austempered ductile iron (ADI) that can ensure a predominantly martensitic microstructure and preclude partial/comp lete dissolution of graphite nodules in the laser hardened zone during lase r irradiation. The exercise involves prediction of the thermal profile (usi ng the Ashby and Easterling model), and consequently, the carbon diffusion profile around the graphite nodules at different depths from the surface fo r the given conditions of LSH. Microstructural investigations have been car ried out by optical and scanning electron microscopy to study the morpholog y, shape and width of the partially/completely melted graphite nodules as a function of the LSH parameters. Finally, the predicted maximum width of th e melted zone around the graphite nodules is compared with the relevant exp erimental data to validate the proposed model. (C) 2001 Published by Elsevi er Science Ltd.