Caracterización de acero inoxidable super dúplex mediante técnicas de nanoindentación a 475ºC.
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Date
2025
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Universidad de Concepción
Abstract
El presente trabajo investiga la evolución microestructural y mecánica de un acero inoxidable súper dúplex sometido a envejecimiento térmico a 475 °C. Se analizaron muestras en estado de solubilizado (T0) y después del tratamiento térmico (T2) mediante microscopía óptica, microscopía de sonda de barrido, EDS y nanoindentación, con énfasis en el mapeo estadístico (XPM). A temperatura ambiente, las fases ferrita y austenita se distinguieron claramente tanto microestructural como mecánicamente, registrando valores promedio de 5.42 GPa de dureza y 225 GPa de módulo elástico para la ferrita, y de 4.03 GPa y 204 GPa para la austenita, respectivamente. Tras el envejecimiento, la ferrita sufrió una severa descomposición espinodal, lo que condujo a la formación de fases secundarias con respuestas mecánicas distintas. La austenita secundaria exhibió una dureza media de 4.19 GPa y un módulo elástico de 170 GPa. La ferrita descompuesta (α′) presentó valores notablemente superiores, con una dureza de 6.56 GPa y un módulo de 220 GPa. La fase sigma (σ), identificada en regiones localizadas, mostró la mayor rigidez, con una dureza de 9.7 GPa y un módulo elástico de 277 GPa. El principal aporte de este estudio radica en la aplicación de XPM a alta temperatura, lo que permitió obtener mediciones estadísticamente robustas en condiciones experimentales desafiantes y entregar evidencia directa de la evolución mecánica de las fases secundarias durante el envejecimiento. Los resultados son consistentes con la literatura, demostrando que el tratamiento térmico a 475 °C promueve un endurecimiento significativo de la ferrita mediante descomposición espinodal y precipitación de fases secundarias, lo que tiene implicaciones directas en las condiciones de servicio.
This work investigates the microstructural and mechanical evolution of a super duplex stainless steel subjected to thermal aging at 475 °C. Samples in the solution-annealed condition (T0) and after heat treatment (T2) were analyzed using optical microscopy, scanning probe microscopy, EDS, and nanoindentation, with an emphasis on statistical property mapping (XPM). At room temperature, the ferrite and austenite phases were clearly distinguished both microstructurally and mechanically, with recorded average values of 5.42 GPa hardness and 225 GPa elastic modulus for ferrite, and 4.03 GPa and 204 GPa for austenite, respectively. Following aging, the ferrite underwent severe spinodal decomposition, leading to the formation of secondary phases with distinct mechanical responses. The secondary austenite exhibited an average hardness of 4.19 GPa and an elastic modulus of 170 GPa. The decomposed ferrite (α′) showed notably higher values, with a hardness of 6.56 GPa and a modulus of 220 GPa. The sigma (σ) phase, identified in localized regions, showed the highest stiffness, with a hardness of 9.7 GPa and an elastic modulus of 277 GPa. The main contribution of this study lies in the application of high-temperature XPM, which enabled statistically robust measurements under challenging experimental conditions and provided direct evidence of the mechanical evolution of the secondary phases during aging. The results are consistent with the literature, demonstrating that the 475 °C heat treatment promotes significant hardening of the ferrite through spinodal decomposition and the precipitation of secondary phases, which has direct implications for service conditions.
This work investigates the microstructural and mechanical evolution of a super duplex stainless steel subjected to thermal aging at 475 °C. Samples in the solution-annealed condition (T0) and after heat treatment (T2) were analyzed using optical microscopy, scanning probe microscopy, EDS, and nanoindentation, with an emphasis on statistical property mapping (XPM). At room temperature, the ferrite and austenite phases were clearly distinguished both microstructurally and mechanically, with recorded average values of 5.42 GPa hardness and 225 GPa elastic modulus for ferrite, and 4.03 GPa and 204 GPa for austenite, respectively. Following aging, the ferrite underwent severe spinodal decomposition, leading to the formation of secondary phases with distinct mechanical responses. The secondary austenite exhibited an average hardness of 4.19 GPa and an elastic modulus of 170 GPa. The decomposed ferrite (α′) showed notably higher values, with a hardness of 6.56 GPa and a modulus of 220 GPa. The sigma (σ) phase, identified in localized regions, showed the highest stiffness, with a hardness of 9.7 GPa and an elastic modulus of 277 GPa. The main contribution of this study lies in the application of high-temperature XPM, which enabled statistically robust measurements under challenging experimental conditions and provided direct evidence of the mechanical evolution of the secondary phases during aging. The results are consistent with the literature, demonstrating that the 475 °C heat treatment promotes significant hardening of the ferrite through spinodal decomposition and the precipitation of secondary phases, which has direct implications for service conditions.
Description
Tesis presentada para optar al título de Ingeniero/a Civil Mecánico/a.
Keywords
Acero inoxidable, Microestructura Mediciones, Nanotecnología