Ultrastrong and stress corrosion cracking-resistant martensitic steels

This study aims to reveal the atomic-scale effects of tempering on the complex substructures and stress corrosion cracking (SCC) resistance of high-strength martensitic steels. The SCC resistance and strength of boron-doped Fe-0.3C-0.3Si-1.0Mn-1.0Ni-0.5Cr (wt%) martensitic steel increase concurrently without low-temperature tempering. Notably, the degradation of SCC resistance caused by tempering is in con-trast with the known effect. To explore this unexpected result, subboundaries inside the martensitic mi-crostructure are investigated via atomic-nano-micro-scale analyses. The strongly segregated carbon at the lath boundaries during tempering is a precursor to the harmful cementite, which acts as severe SCC ini-tiation sites. Eventually, intensive crack grew along the lath boundaries, deteriorating the SCC resistance of the material. (c) 2022 The Authors. Published by Elsevier Ltd on behalf of Acta Materialia Inc. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

Automated summary

This study aims to reveal the atomic-scale effects of tempering on the complex substructures and stress corrosion cracking resistance of high-strength martensitic steels. The surprising finding is that tempering leads to a decrease in SCC resistance, contrary to the known effect. Analysis of subboundaries in the martensitic microstructure shows that carbon segregation at the lath boundaries during tempering acts as a precursor to harmful cementite, ultimately degrading the SCC resistance of the material.