Microstructural phase transformation of a super duplex steel powder sintered by hot isostatic pressing
Abstract
In this study, phase transformations and microstructural evolution in F55 (UNS S32760) super duplex stainless steel powder processed by hot isostatic pressing (HIP) were investigated. Two kinds of HIP cycles were performed: a complete cycle carried out at 1200 °C under a pressure of 102 MPa with a holding time of 4 hours, and a series of interrupted tests (without holding time) performed at 800, 900, 1000, 1100, and 1200 °C. Microstructural characterizations revealed that after the complete HIP cycle, the material exhibits a biphasic microstructure, consisting of nearly equal fractions of austenite and ferrite, similar to conventionally processed duplex steels. During interrupted tests, σ phase precipitation was observed at temperatures of 900 °C and above, resulting from ferrite decomposition via the eutectoid reaction α → σ + γ2. This transformation led to the formation of needle-shaped secondary austenite (γ2), denoted as Widmanstätten austenite. At temperatures above 1100 °C, significant σ phase dissolution occurred, accompanied by a progressive increase in ferrite fraction and a gradual disappearance of the Widmanstätten austenite. The precipitation of the σ phase increases the hardness of the sintered samples, while its dissolution subsequently leads to a decrease. In the absence of the σ phase, ferrite appears to provide higher hardness than austenite.
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BibTeX
@article{eba2026microstructural,
title = {{Microstructural phase transformation of a super duplex steel powder sintered by hot isostatic pressing}},
author = {R. Mvodo Eba and Maria-Rosa Ardigo-Besnard and J.-P. Chateau-Cornu and F. Herbst and N. Geoffroy and Arnaud Proietti},
journal = {Journal of Materials Research and Technology},
year = {2026},
month = sep,
doi = {10.1016/j.jmrt.2026.09.059},
url = {https://ube.hal.science/hal-05742806v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Microstructural phase transformation of a super duplex steel powder sintered by hot isostatic pressing
AU - R. Mvodo Eba
AU - Maria-Rosa Ardigo-Besnard
AU - J.-P. Chateau-Cornu
AU - F. Herbst
AU - N. Geoffroy
AU - Arnaud Proietti
PY - 2026
DA - 2026/09/08
JO - Journal of Materials Research and Technology
DO - 10.1016/j.jmrt.2026.09.059
UR - https://ube.hal.science/hal-05742806v1
AB - In this study, phase transformations and microstructural evolution in F55 (UNS S32760) super duplex stainless steel powder processed by hot isostatic pressing (HIP) were investigated. Two kinds of HIP cycles were performed: a complete cycle carried out at 1200 °C under a pressure of 102 MPa with a holding time of 4 hours, and a series of interrupted tests (without holding time) performed at 800, 900, 1000, 1100, and 1200 °C. Microstructural characterizations revealed that after the complete HIP cycle, the material exhibits a biphasic microstructure, consisting of nearly equal fractions of austenite and ferrite, similar to conventionally processed duplex steels. During interrupted tests, σ phase precipitation was observed at temperatures of 900 °C and above, resulting from ferrite decomposition via the eutectoid reaction α → σ + γ2. This transformation led to the formation of needle-shaped secondary austenite (γ2), denoted as Widmanstätten austenite. At temperatures above 1100 °C, significant σ phase dissolution occurred, accompanied by a progressive increase in ferrite fraction and a gradual disappearance of the Widmanstätten austenite. The precipitation of the σ phase increases the hardness of the sintered samples, while its dissolution subsequently leads to a decrease. In the absence of the σ phase, ferrite appears to provide higher hardness than austenite.
SN - 2238-7854
SN - 2214-0697
ER -