Current Status of Carbidic Austempered Ductile Iron

Grinding balls in wet ball mill are important consumables in mine grinding equipment, which have poor wear resistance and large consumption. It is imperative to find excellent wear-resistant materials for the grinding balls. Carbidic Austempered Ductile Iron (referred to as CADI) was used as small and medium-sized wet ball mills. This grinding ball has the advantages of less wear, low crushing rate, power saving and low noise. However, the CADI grain boundaries are distributed with net-like eutectic carbides, which seriously damage the continuity of the matrix. In addition, the mechanism of corrosion wear and impact fatigue is lack of research due to complex phase composition and unclear mechanism of phase properties on improving performance. So CADI can’t be applied to the grinding balls in large wet ball mill. Based on the above problems, this paper first analyzed the heteronucleation mechanism and adsorption mechanism of M3C type carbides by using the first principle of microalloying elements, and then verified it by combining with experimental results. Then the thermodynamics and kinetics of austenite homogenization and isothermal transformation of ductile iron containing carbides were analyzed by means of modeling calculation and experiment. On this basis, a new type heat treatment process comprising super-high temperature pretreatment and austempering treatment (S&A treatment) was used to process CADI, which provides a new idea for further improving toughness of CADI. Finally, the CADI corrosion wear and impact fatigue failure mechanism were revealed by analyzing the change rule of the sample surface and cross section after corrosion wear and impact fatigue.