Influence of isothermal aging in LDX 2101 duplex stainless steel on the microstructure and local properties

Type : Publication
Auteur(s) :  N Ouali, B Cheniti, B Belkessa, B Maamache, R Kouba, M Hakem
Année :  2021
Domaine : Sciences des matériaux
Revue : The International Journal of Advanced Manufacturing Technology
Résumé en PDF :  (résumé en pdf)
Fulltext en PDF :  (.pdf)
Mots clés :  microstructure, Interface, precipitates, Nano-hardness, Surface degradation

Résumé : 

In the present work, the interface morphology and the evolution of nitride precipitates in LDX 2101 stainless steel isothermally treated at 750 °C for various aging times were investigated. The microstructure results showed that the Cr2N nitrides precipitated along the δ/γ interface with 200 nm in length and continue to grow to 2 μm after 240 h of aging. However, only Cr2N nitrides were found at the δ/δ interface after long term of aging. Atomic force microscopy (AFM) analysis revealed that Cr2N nitrides andCr23C6 carbides started to precipitate after the first 10 min of aging with a small needle shape of the former and specific triangular morphology of the latter. The evolution of hardness and Young’s modulus of the interfaces, performed with nano-indentation measurements, showed that the δ/γ interface became harder (4.1 ± 0.2 GPa) with increasing aging times, whereas negligible changes in the hardness and elastic modulus were recorded at the δ/δ interface. 3D topographic analysis of the immersed surfaces revealed that the susceptibility of δ phase to preferential dissolution in 3.5% NaCl solution increased with aging time. This behavior was manifested by the important imperfections of δ phase, the high surface roughness (55.7 nm), and the deep corrosion pits (30 nm) along the δ/γ interface and around the Cr2N nitrides.