Influence of nodule count, austenitising variables and matrix on ductile iron decarburisation

Abstract

The surface decarburisation produced during the austenitising stage of ductile iron parts constitutes an issue that needs to be addressed in many manufacturing processes. This work examines the role that nodule count and other variables play on decarburisation onset and decarburised layer thickness. Specimens with noticeable different nodule counts were employed to perform the experiments. The results showed that the thickness of the decarburised layer markedly decreases as nodule count increases, and that the decarburised layer depth increases as the austenitising holding time increases. On the other hand, the austenitising temperature has little influence on the decarburisation process. An equation able to calculate the decarburisation onset, the austenitising holding time and the decarburised layer thickness was developed. This equation yields accurate estimations for austenitising ductile iron parts with prior ferritic matrixes, and is further applicable to a wide range of nodule counts, which even comprise those proper of thin wall ductile iron parts.