Abstract

Water pump machine impeller is made of gray cast iron with some variation of wall thickness. According to it, the thin part undergoes a very rapid cooling so as to form a ledeburite. This study removes the formed ledeburite ((α + Fe3C) + Fe3C) by mean of heat treatment. The first step to remove the presence of ledeburite is by calculating the retained carbide at the level of 5%. Since the material consists only carbon as the main alloying element, the temperature of the heat treatment can be determined by using the Fe-Fe3C diagram. After 2 hours of holding at 830 ° C ledeburite changes to ferrite and graphite. Based on the metallographical observation it is found that graphite forms discrete shape and is located at the grain boundary. The boundary of pearlite grain in the ledeburite itself does not change after the completion of heat treatment. The graphite resembles a randomly oriented eutectic undercooling type D and accompanied by a decrease of hardness to 115HV which occurs at the tip of the impeller blade

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