Microstructural and Mechanical Modification of Ductile Iron by Niobium Addition

César Becerra, Felipe Hernández, Jesús García, Zianya Gómez and Marissa Vargas

DOI: https://doi.org/10.64486/m.65.3.1
Online publication date: December 19, 2025

Abstract: This study investigated the influence of niobium additions on ductile iron through the production of four alloys containing 0 wt.%, 0.11 wt.%, 0.23 wt.% and 0.32 wt.% Nb. Microstructural phases were characterized, and mechanical properties were evaluated through hardness, impact toughness, tensile and wear tests. Niobium promoted carbide formation, which increased from 0.53 % to 2.48 %, and reduced graphite nodularity from 256.1 nod/mm² to 156.4 nod/mm². Hardness in-creased from 13.72 HRC to 26.6 HRC, while the ultimate tensile strength and yield strength reached 746 MPa and 449 MPa, respectively, in Alloy 4. In contrast, impact toughness decreased from 10.45 J to 5 J. Overall, niobium improved wear re-sistance but reduced the toughness of the material.

Keywords: niobium; ductile iron; pearlite; cementite

This article is published online first and will appear in Metalurgija, Vol. 65, Issue 3 (2026).