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 was 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 EϷ3 to EϷ2 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 10 J, 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.

Wear Behavior of CADI Operating Under Different Tribosystems

“…18) On the other hand, the impact toughness decreased from ϳ100-130 J/cm 2 for ADI to ϳ7 J/cm 2 for CADI variants with the highest carbide contents. Notwithstanding this, it should be considered that these values are higher than those of high abrasion resistance alloys like white cast irons (up to ϳ3 J/cm 2 ).…”

“…The first studies on CADI were undertaken by researchers from the American company Applied Process, who obtained and characterized two variants of this material, particularly evaluating its laboratory abrasion resistance (pin on disk and ASTM G 105 abrasion tests), and compared it to that of traditional abrasion resistant materials such as steels and cast irons. 15,16) Previous works by the authors 17,18) have dealt with different CADI variants, in which carbide precipitation was obtained by alloying with chromium contents between 0.5 and 2.5 wt% in almost eutectic compositions, combined with a chill in the mould to vary the solidification rate. A hypoeutectic composition was also analyzed.…”

Development and Characterization of a New Type of Ductile Iron with a Novel Multi-phase Microstructure

“…It has been documented that ADI behaves satisfactorily under low and high stress abrasion when heat treatment parameters are properly selected. 2,3) Furthermore, regarding heavy abrasive conditions, a new type of ADI containing free carbides (CADI) has recently burst into the market. 4,5) The presence of carbides reinforces the matrix against abrasive particles penetration, reducing impact toughness at the same time.…”

Production of surface chilled ductile iron

“…There is no enough time for dendritic growth at high cooling rate. The results can be explained with the effects of high cooling rate on the carbide formation [1][2][3][4][5][36][37][38][39][40].…”

“…The microstructure of surface chilled ductile iron consists of ferrite, pearlite and carbide as a distinct from conventional ductile iron [1][2][3]. Especially, surface chilled ductile iron has been used in the production of machine parts having high toughness and wearing properties [4][5].…”