The effect of nickel content on structure and hardness of ductile iron in thin-walled castings

In the technology of ductile iron manufacture, graphite precipitates take the form of spheroids, and this shape has the least harmful effect on cast iron mechanical properties. The strength of ductile iron depends mainly on its matrix, and hence on the chemical composition, solidification kinetics and heat treatment technology. This article presents the results of micro-hardness and hardness measurements, and the results of metallographic examinations and thermal analysis carried out on thin-walled ductile iron castings with varying nickel content. The main aim of the research was to determine the effect of nickel content on structure and properties of ductile iron in thin-walled castings. To achieve the goal, ductile iron containing 0.001; 1.0; 10 and 24% Ni was manufactured. It has been shown that nickel stabilizes austenite. With the nickel content of 24%, a completely austenitic matrix was obtained, the addition of 10% Ni to the matrix produced martensite, considerably increasing the cast iron hardness. Low content of this additive had a pearlite-forming effect.

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