Potential of Hot Sesame Oil (sesanum indicum oil) Bath as Quenchant for Austempering of Ductile Cast Iron

Potential of sesame oil (sesanum indicum oil) as quenching medium for austempering heat treatment of ductile cast iron has been studied. Samples of ductile iron were machined and then normalized prior to austempering heat treatment. Samples were austenitized at 900oC. They were then soaked for 1 hour and then austempered in hot sesame oil bath held at 300oC for periods of 1, 2, 3, 4 and 5 hours. Mechanical properties (tensile strength, percent elongation, and impact strength) of the test samples were evaluated. The test results obtained showed that the highest value of tensile strength (1029 N/mm2) and percentage elongation (14.6) were obtained from sample austempered for 3 hours. Maximum impact strength (163 kJ/m2) was also obtained from sample austempered for 4 hours. Microstructures of the samples were analyzed using optical microscopy (OM) and scanning electron microscopy (SEM). The microstructure, which consist of graphite nodules embedded in a matrix of ausferrite (acicular ferrite and carbon enriched austenite) was observed. The research showed that sesame oil was able to cause the formation of ausferrite structure, hence could be recommended to be used as an austempering quenching medium for ductile cast iron.