TITLE:
Effect of Cast Thickness and Austenitizing Temperature on Microstructure and Mechanical Properties of ADI and IADI Castings
AUTHORS:
A. M. Negm, S. S. Mohamed, Mervat M. Ibrahim, Moussa Ibrahim, Khaled M. Ibrahim
KEYWORDS:
DI, ADI, IADI, Retained Austenite, Wear Resistance
JOURNAL NAME:
Open Journal of Metal,
Vol.11 No.3,
September
21,
2021
ABSTRACT: This investigation studies the impact strength, tensile strength, hardness, and wear behavior of thin wall austempered and intercritically austempered ductile iron samples with a chemical composition of 3.37% C, 2.7% Si, 0.30% Mn, 0.01% S, and 0.01% P. The austempered samples were austenitized at 900?C for 1 h and rapidly quenched in a salt bath furnace at 375?C for 1 h. The intercritically austempered samples were sub-austenitized at 810?C for 1 h and rapidly quenched in a salt bath furnace at 375?C for 1 h. The properties of the austempered and intercritically austempered thin wall plates of 5, 10, and 15 mm thickness were evaluated and compared to the as-cast samples. Austempering process affects greatly the tensile properties of all cast thicknesses where ultimate strength reached 1004 MPa for 5-mm thickness. Optimum impact toughness of 40 J was obtained for the austempered samples of 10- and 15-mm thicknesses. The intercritically austempered samples showed properties between the austempered and as-cast samples. Maximum wear resistance was also reported for the austempered samples due to containing retained austenite in the structure which in turn transformed into martensite that increases well the wear resistance. Maximum ultimate strength (1056) MPa and hardness (396 HV) were obtained for 5 mm ADI sample. Maximum impact toughness (43 J) was achieved for 15 mm IADI sample due to existing of pro-eutectoid ferrite in matrix. For all As-cast, ADI and IADI irons, wear resistance decreased with increasing sample thickness. Minimum wear rate (2.22 × 10?6 g/s) was reported for 5-mm ADI sample and maximum one (15.8 × 10?6 g/s) was registered for 15-mm as-cast DI sample, at a sliding speed of 2 m/s.