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In as-cast material, cracking can occur during assembly or welding processes depending on the manufacturing conditions. This study proposed heat treatment strategies to improve the ductility of as-cast stabilized ferritic stainless cast steel containing Nb, particularly focusing on cooling rate after solution treatment. The specimen cooled at 1.0 ◦C/min (“Slow-cooled sample”) exhibited ductile fracture, while the specimen cooled at 2.0 × 104 ◦C/min (“Rapid-cooled sample”) exhibited low ductility and cleavage fracture. The fracture initiation site of the Rapid-cooled sample was a coarse oxide particle near the grain boundary. In the ferrite matrix surrounding the oxide particles in the Rapid-cooled sample, more dislocations were observed compared to the Slow-cooled sample. These dislocations are likely introduced by local thermal stress generated during rapid cooling, resulting in the suppression of plastic accommodation around the oxide particles during plastic deformation. Consequently, stress concentration at the crack tips of the oxide particles and their Nb(C, N) coating increases, causing the cracks to propagate into the ferrite matrix. Accordingly, we concluded that the dislocations introduced around the oxide particles are one of the major factors reducing the ductility of the Rapid-cooled sample.

Rights:

• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

Keyword: Ferritic stainless cast steel, Nb stabilized steel, Heat treatment, Cooling rate, Ductility, Cleavage fracture

Date published: 2025-08-29

Publisher: Elsevier BV

Journal:

• Materials Science and Engineering: A (ISSN: 09215093) vol. 945 148952

Funding:

• National Institute for Materials Science

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1016/j.msea.2025.148952

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Updated at: 2025-12-19 14:03:10 +0900

Published on MDR: 2025-12-19 16:51:12 +0900