Metallographic Investigation of Nd: YAG Laser Processed Ductile Iron Surfaces

Abstract

Ductile cast iron is finding increased applications in parts subjected to different types of wear due to sliding contact and hence novel hardening techniques of mating surfaces need to be investigated. Laser hardening has proved to be very effective in enhancing the tribological properties of ductile iron surface. In this work, high power CW-Nd:YAG 600 W laser was used for the processing of ductile iron surfaces at different scanning speeds. The depth and hardness of the processed surface were found to be dependent on the scanning speed. At lower speeds of 25 cm/min, remelting and rapidly solidified layer resulted in the formation of carbidic and graphite free surface layer of microhardness around 1200 HV. Increasing the scanning speed to 125 cm/min results in heating of the surface layer to the austenitic region with the formation of martensitic layer upon rapid cooling. Some microstructural features associated with the laser processing were noticed at the hardened/HAZ transition layer and suggestions were made for their formation. Microhardness profile across the hardened zone were plotted, where different scanning speeds were shown to affect the hardened case depth and hardness.