Microstructure, mechanical parameters, and corrosion resistance of austenitic ductile iron castings

Abstract Austenitic ductile iron, also known as Ni-resist cast iron, belongs to the cast iron group, which is characterized by a high-nickel content ranging from 18% to 36% by weight. Although this level of nickel content significantly increases the production costs, it imparts numerous beneficial properties that justify the price. One notable property is its ability to operate across a wide temperature range, with a minimum service temperature of − 200 °C, and a maximum, depending on the grade, reaching up to 1050 °C. This family of high-quality alloys demonstrates mechanical properties, where grades without carbide-forming elements achieve elongation exceeding 40%. On the other hand, by adding Cr, which is a carbide-forming element, the Ni-resist cast iron’s plasticity decreases, while its corrosion resistance properties increase. However, a comprehensive investigation into the correlation between mechanical properties and corrosion resistance, particularly in relation to various nickel contents in the presence of Cr in high-nickel cast iron, is scarce. Therefore, the primary aim of this study was to elucidate the role of nickel content and chromium content in influencing the mechanical and corrosion resistance properties of austenitic ductile iron. The addition of 21, 25, 28, and 35 wt% of nickel with and without 2.5 wt% of chromium was investigated. Characterization of the materials was carried out using optical and scanning electron microscopy, static tensile tests, impact strength tests, and corrosion resistance assessments at room temperature in a 3.5 wt% NaCl solution. The investigation revealed a significant influence by changing the nickel and chromium content on the properties of high-nickel cast iron. In addition, it was proved that by controlling the content of these elements, the cast iron with establish properties can be achieved—depending on expected final properties, results show that it is possible to substitute part of the nickel content with smaller amount of chromium to get similar corrosion resistance properties and reduce the production costs, but it will influence to mechanical properties, which dependent on plasticity.