POTENTIAL OF HOT-BAOBAB SEED OIL (ADONSONIA DIGITATA) BATH AS AN AUSTEMPERING MEDIUM FOR DUCTILE CAST IRON
Despite the report by many researchers on the suitability of polymer solution, hot bitumen, mineral and vegetable oils as quenching medium for austempering of ductile (nodular)cast iron. These findings minimized the need for the molten salt and lead baths. However, the substantial deficiencies with respect to environmental friendliness, high cost, non-availability and toxicity of molten salt and lead baths justify the search for alternative replacement media. Therefore, the present study focus on using hot baobab seed oil bath as an austempering medium for ductile cast iron. Samples of ductile cast iron were machined to standard dimensions for tensile, impact and microstructural analysis test specimens prior to the austempering process. The samples were normalized and thereafter, austempered in hot baobab seed oil bath at 260oC and 310oC for 1-5hrs from austenitizing temperature of 875oC. Mechanical properties of the test samples were evaluated. The test results obtained showed that samples austempered at 260oC and 310oC for 3hrs exhibited superior mechanical properties than those at 1, 2, 4 and 5hrs. The tensile strength increased from 446 N/mm2 for the as-received samples to the maximum value of 1005 N/mm2 for the austempered samples with percent elongation of 13.6. Impact strength increased from 57 kJ/m2 (as-received) to 128 kJ/m2 (austempered). Microstructures of the samples were analyzed using optical microscopy (OM) and scanning electron microscopy (SEM). In all the test samples, ausferrite (bainite) structures which consist of acicular ferrite and carbon enriched austenite were observed. The research showed that, baobab seed oil produced ausferrite (bainite) structures, hence could be recommended for use as an austempering quenching medium for ductile cast iron.
Authors : Abdulhamid, S.
Category : Open Access Volume (Issue) : 8(2) Date Uploaded : 28th January 2023