Wear behavior of austempered ductile irons with dual matrix structures

An unalloyed ductile iron containing 3.42 C wt.%, 2.63 Si wt.% and 0.318 Mn wt.% was intercritically austenitized in two-phase region (alpha + gamma) at various temperatures of 795 degrees C, and 815 degrees C for 20 min and then quenched into salt bath held at austempering temperature of 365 degrees C for various times to obtain austempered ductile iron (ADI) with different ausferrite volume fractions distributed in soft proeutectoid ferrite matrix. Some samples were also conventionally austempered for comparison reason. For austempered samples, the tensile strength and hardness decreased with increasing the austempering time, whereas the elongation increased considerably. In addition, the abrasive wear behavior of as cast and ADI's with dual matrix structure was studied under different loads without lubrication. It was found that the wear resistance of ADI with dual matrix structure was superior to that of as cast iron. Among the austempered samples, the lowest weight loss was observed for conventionally austempered samples with its wholly ausferritic structure throughout the specimen while the highest weight loss was obtained for the samples having the lowest ausferrite volume fractions in those samples with dual matrix structures. Moreover, wear resistance increased with increasing ausferrite volume fraction and decreasing austempering time in all tested samples. (c) 2006 Elsevier B.V. All rights reserved.