The Impact of Wall Thickness on the Microstructure and Mechanical Properties of Austenitic High-Nickel Ductile Iron

Abstract

Austenitic ductile iron belongs to the cast iron group characterized by high nickel content, ranging from 18% to 36% by weight, which allows the formation of an austenitic metallic matrix. As a consequence, this cast iron group exhibits a combination of highly beneficial properties allowing utilization under extreme conditions and justifies the increased price of these cast iron grades. Some of the applications require complex castings with changing geometry and wall thicknesses. For this reason, the main objective of this study was to determine the possibility of obtaining castings with various degrees of wall thickness, including thin-walled: 3 mm, 5 mm, 13 mm and 25 mm, and good quality microstructures without defects as well as with mechanical properties on a similar level. For our investigations the austenitic ductile cast iron grade EN-GJSA-XNi22 was selected. Material characterization was carried out using optical microscopy, and static tensile test measurements. Additionally, the thermal analysis during crystallization was also determined. The investigations showed the highly homogeneous mechanical properties of castings with various wall thicknesses. The main differences in the microstructure parameters concerned the number and diameter of the graphite nodules.