Influence of Nb Addition on Impact Toughness of As-Quenched Martensitic Stainless Steel for Automotive Applications

Abstract:

This study presents how Nb addition allowed improving the Charpy impact toughness of a martensitic stainless steel by comparing a conventional AISI410 (12%Cr-0.1%C) and a 12%Cr-0.1%C-0.1%Nb steel after the same austenitization and quenching heat treatment. Adding niobium decreased the ductile-to-brittle transition temperature by 100°C with respect to the Nb-free steel. To identify quantitative fracture criteria for the two materials, the values of critical cleavage fracture stress were determined by the local approach to fracture, combining low temperature tensile tests on notched specimens and mechanical analysis by the finite element method. The main effects of niobium were to refine the grain size and to promote retained austenite films, resulting in a similar resistance to cleavage crack initiation but in a strong improvement of the ductile-to-brittle transition behavior by increasing the resistance to cleavage crack propagation.

• Periodical: Materials Science Forum (Volume 941)
• Pages: 245-250
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.941.245
• Online since: December 2018
• Authors: Jean Denis Mithieux*, Hélène Godin, Anne Françoise Gourgues-Lorenzon, Coralie Parrens
• Keywords: Cleavage Fracture Stress, Hot Forming, Impact Toughness, Martensitic Stainless Steel, Niobium

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