EFFECT OF GRAPHITE FLAKES ON THE MICROSTRUCTURE OF MELTED, TRANSITION AND HEAT AFFECTED ZONES IN GREY CAST IRON REMELTED BY TIG

Abstract:transition and heat affected zones formed during surface remelting (in order to improve wear resistance) with TIGprocess has been investigated. Relationship between various TIG parameters and thickness of remelted and heataffected zones revealed that a high concentrated heat energy is imposed by TIG process which makes it a proper optionfor focused surface treatment. Based on microstructural examinations five areas with different microstructure andmicrohardness were identified within the surface area. Graphite flakes were totally dissolved within the first arealeading to the transformation of denderitic austenite to plate martensite and the formation of ledeburite withininterdenderites. The main feature of the second area, resulted from the presence of graphite flakes, was the localmelting with a gap in the vicinity of graphite flakes and that of third area was the formation of finer and densermartensite plates closer to the graphite flakes compared with those formed at a further distance. In the fourth layerthere is a mixture of martensitic and pearlitic matrix while the matrix of fifth layer has no change of microstructure.In this study the effect of graphite flakes present in a pearlitic grey cast iron on the microstructure of melted,

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Keywords: surface remelting ، grey cast iron ، TIG ، local remelting