Stereological Evaluation of Precipitates within Ferrite Grains in Heat-Treated 1.25Cr0.5Mo Steel Previously Exposed to Service

Rafael Fernández-Fuentes (Universidad Central Marta Abreu de Las Villas– UCLV, Cuba)
Americo Scotti (Universidade Federal de Uberlândia–UFU, Brazil;University of West, Department of Engineering Science, Trollhättan, Sweden)
Amado Cruz-Crespo (Universidad Central Marta Abreu de Las Villas–UCLV, Cuba)
Roberto Silva González (Universidad Central Marta Abreu de Las Villas–UCLV, Cuba)
Rafael Ariza (Universidade Federal de Uberlândia–UFU,Brazil)
Nelson Guedes de Alcântara (Universidade Federal de São Carlos–UFSCar, Brazil)

Article ID: 1017

DOI: https://doi.org/10.30564/jmmr.v2i2.1017

Abstract


The objective of this work was to study the effect of the heat treatment and further operation aging on the stereological parameters (size, quantity and volume fraction) of precipitates within ferrite grains of a creep-resistant 1.25Cr0.5Mo steel after long-term operation. The heat treatment was similar to the treatment that is carried out in industrial steam pipelines after welding (post weld heat treatment - PWHT) during installation and/or repairing. The operation aging corresponds to a subsequent long in-service operation after repairing. To determine the stereological parameters, SEM digital images were taken from samples of this material after conditions of in-service-aged (after long-term operation), in-service-aged and heat-treated (simulating repairing) and in-service-aged, heat-treated and in-laboratory aged (simulating subsequent long-term operation after repairing). The results indicate that the changes in the stereological parameters of the precipitates within ferrite grains after PWHT is associated with the coarsening process of the within-ferrite-grain precipitates as well as stabilizing the microstructure, since the material aging after PWHT of an in-serviced aged material would not change the stereological parameters.


Keywords


Creep-resistant 1.25Cr0.5Mo Steel; Repairing; PWHT; Precipitation coarsening

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Copyright © 2019 Rafael Fernández-Fuentes, Americo Scotti, Amado Cruz-Crespo, Roberto Silva González, Rafael Ariza Gonçalves, Nelson Guedes Alcântara


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