Influence of chemical composition and solidification rate on the abrasion and impact properties of CADI

Abstract

The use of CADI, a variant of Austempered Ductile Iron (ADI) containing free carbides, is on the increase thanks to its excellent combination of high abrasion resistance and good impact toughness, when compared to other materials with similar wear resistance. The present work focuses on the study of two CADI variants in which carbides were obtained by a combination of alloying elements and the effect of a cooper chill located in the mould. A detailed microstructural characterization of the material was made; and the content and composition of the carbides as well as their stability during the heat treatment were particularly studied. The abrasion wear resistance as evaluated by testing under the ASTM G 65 standard, and comparing the relative wear resistance of samples taken just beside the cooper chill up to locations where the chill did not affect the solidification rate. The relative wear resistance, determined by using ADI as a reference material, ranged from £=3 to £=2 for samples taken from the different locations, close and far to the chill, respectively. For samples taken from the same locations, the impact toughness ranged from 6.5 to 10J, respectively. The results allow establishing a relationship between the solidification rate, the microstructure and the mechanical properties, thereby enabling to predict their effect on current applications. © 2009 ISIJ.