Effect of Austenitization Time on Corrosion and Wear Resistance in Austempered Ductile Iron

Abstract

The temperature and time of austenitization are of great practical importance during the austempering heat treatment of ductile iron, as these factors influence the transformations in the solid state, modifying the matrix microstructure and the resulting mechanical properties of the material obtained after subsequent austempering. The objective of this research is to investigate the influence of austenitization time on the microstructural characteristics, wear, and corrosion rate of ductile iron subjected to an austenitization heat treatment at 1050 °C for 120, 180, and 240 min, followed by austempering at 350 °C for 60 min. To assess the corrosion and wear resistance of the samples, potentiodynamic tests in a 3.5% NaCl solution and pin-on-disk tribological tests were, respectively, conducted. The results demonstrated that increasing the austenitization time results in ausferritic microstructures with a higher content of carbon-rich austenite accompanied by a higher content of carbon, and lower microstructural heterogeneities due to the last to freeze zones in ductile iron. The material's corrosion and wear resistance improved as the austenitization time was increased.