CHARACTERIZATION OF FUSION LINES OBTAINED BY LASER WELDING ON AUSTEMPERED DUCTILE IRON PLATES WITHOUT PREHEATING

Austempered Ductile Iron (ADI) is a new engineering material with an exceptional combination of mechanical properties and important applications in different fields. ADI is obtained from Ductile Iron (DI) after austenitization at 850...950 °C for 0.5...3.5 hours, followed by rapid cooling to isothermal transformation temperature 235...450 °C, kept 0.5...4 hours at this temperature. The present research has the objective to investigate the weldability of ADI using laser welding technology without preheating. Having the geometry of the fusion lines and the lack of the welding defects as decision criteria, the parametrical window power (P) - welding speed (V) was explored by carrying out the fusion lines on ADI plates without preheating. The power-welding speed diagram for feasible domains of laser welding was generated by eliminating the unsatisfactory domains, characterized by collapse of the melted metal, incomplete penetration and low fusion lines quality (geometry, compactness). Each obtained fusion line was examined using optical microscopy, SEM, EDS and XRD. Vickers method was used to determine the microhardness in the welding specific areas: base material, heat affected zone and melted metal. In addition, the influence of the welding parameters on the geometry and chemical composition of the fusion lines is presented.

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