Production and Mechanical Properties of Austempered Ductile Iron (ADI) Using Periwinkle and Alloy Nodularizers for Crankshaft Applications

Abstract

The excellent mechanical properties of austempered ductile iron (ADI) have been harnessed to significantly increase its application in automobile parts and improve its performance. The produced ADI crankshaft in this research from investment casting using periwinkle shell as nodularizers technique is labelled A, B, C, D, E, F and G. The ADI has shown a good combined mechanical property, exceptional wear resistance, these properties are unavailable in forged steel crankshaft taking advantage of the significant savings in energy, and the resulting advancement of light weight, durable materials, and less expensive, is an evident in replacing forged steel crankshaft. The elemental composition of 25 microns calcined periwinkle ash at 600 °C used as nodularizers in the treatment of ductile iron was carried out with an X-ray fluorescence (XRF) machine (PANanalytical), for the concentration of specific elements attained was good enough as an alternative to ferrosilicon magnesium. The optimisation of the lost-wax crankshaft produced was analysed using the response surface methodology-version 17 MINITAB software of fractional factorial design, using variables such as calcined periwinkle ash because of their economic viability and desirable properties. In the ductile iron melt, the higher temperature of 1000 °C used for calcination offered a higher value of calcium oxide that produced poor mechanical properties of ductile iron from higher carbide formation, hence, the choice of 600 °C with less value of calcium oxide is evident which produce 96% nodularity and 200 nod/mm2 nodule count. The ductile iron produced conforms to ASTM A536 65 – 45 - 12 grade, cast into round rods, and isothermally heat treated at 300 °C austempering temperature at varied times of 30, 45 and 60 minutes that produced the ADI crankshaft. The increase in volume fraction of retained austenite and its carbon content provides favourable ductility and toughness. The good combined mechanical properties exhibited by sample G as a result of copper and vanadium addition were attributed to its high–volume fraction of acicular ferrite and fine ausferritic matrix. Thus, ADI produced from G is recommended for the production of the tricycle crankshaft.