Evolution of precipitated phases during prolonged tempering in a 9%Cr1%MoVNb ferritic–martensitic steel: Influence on creep performance

Zavaleta-Gutierrez, Nilthon Emerson; Cicco, Hernan De; Marrero, José M. Cabrera; Danón, Claudio Ariel; Luppo, M.I.

doi:10.1016/j.msea.2011.01.116

Cited by 36 publications

(22 citation statements)

References 21 publications

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“…Figure reveals the microstructures of samples tempered at 730 °C for 2 and 5 h, respectively. According to the morphology and chemical composition, MX phases were generally classified several types: MX with a spherical shape (type I, enriched in Nb), MX with a plate‐like shape (type II, enriched in V), and MX with a more complex V‐wings shape (type III) . In this study, type I precipitates, that is, spheroid‐like MX, and type II precipitates, i.e., plate or rod‐shaped MX, can be seen, as exhibited in Figure b and c. When the tempering period is prolonged, MX phase coarsens along the direction of length.…”

Section: Resultsmentioning

confidence: 72%

Microstructure Evolution in an Advanced 9Cr–1.5Mo–1Co–VNbBN Alloy during Heat Treatment and High Temperature Aging

Gao

Zhang

Ren

et al. 2019

steel research int.

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The 9Cr–1.5Mo–1Co–VNbBN steel is the most successful cast steel developed so far in the COST program. Its microstructure evolution influenced by austenitizing and tempering are investigated in this paper. The microstructure characterization using an optical microscope and transmission electron microscope is carried out after different heat treatments and long‐term aging at 620 °C. After austenitization at 1100 °C, the steel exhibits a martensite structure with Fe‐rich M3C particles. The M23C6 particles are detected in the sample tempered at 500 °C for 2 h, as well as their sizes continue to grow as the tempering temperature raise. The formation of MX phase is identified after tempering at 500 °C, while the size of MX phase remains stable within the tempering temperature 760 °C and below. The structure evolution of martensitic laths shows that tempering reduces the density of dislocation and forms subgrains and dislocation networks. The microstructure of long‐term aged sample still reveals martensite lath structure with increasing width. In addition to M23C6 and MX phases, Laves phase nucleates and grows rapidly as a result of long‐term aging.

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Section: Resultsmentioning

confidence: 72%

Microstructure Evolution in an Advanced 9Cr–1.5Mo–1Co–VNbBN Alloy during Heat Treatment and High Temperature Aging

Gao

Zhang

Ren

et al. 2019

steel research int.

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“…Como se observa en la tabla 3, todas estas aseveraciones no se cumplen en nuestro caso. Según estudios previos [14], esto indicaría que durante el revenido ha ocurrido un proceso de disolución y re-precipitación de los precipitados MX. Para un tiempo de revenido de 5 h, donde se obtiene una drástica caída en la resistencia al creep, es probable que haya ocurrido una disolución de los precipitados, mientras que para 5,5 h, donde se observa una recuperación en la resistencia y un menor tamaño de precipitados (49,3 nm) es muy probable que haya ocurrido una re-precipitación de los mismos.…”

Section: Resultados Y Discusiónunclassified

“…En ambos casos un incremento posterior en el tiempo de revenido produjo la re-precipitación de las partículas NbC y VN, respectivamente. La aparición de este fenómeno fue corroborada en un estudio previo realizado en la aleación comercial T91 con presencia de los 4 elementos aleantes V, Nb, C y N [14].…”

Section: Introductionunclassified

Influencia del tiempo de revenido a 780°C sobre la resistencia al creep del acero ASTM A335 P91

2018

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It has been investigated the effect of tempering time at 780°C on the creep strength of ASTM A335 grade P91 steel. The tempering temperature corresponded to the industrial tempering temperature and the times evaluated were chosen in such a way to accumulate, between the tempering prior as received (40 min) and the treatment carried out in the laboratory, times of 3; 4; 5; 5,5; 5,7; 6 and 7 hours, so that in practice a double tempering was applied. Subsequently, the samples were creep tested at 600 ºC and 190 MPa up to rupture. The results show that a tempering time to 780 ºC has a very significant impact on the creep strength of the P91 steel. Up to 3 hours of tempering, the P91 steel retains its creep strength, with a minimum creep rate of 7x10 -9 s -1 . This creep strength falls off sharply to the 5 hours of tempering (1.5x10 -7 s -1 ), and retrieved to the 5.5 hours (3 x10 -8 s -1 ). This creep behavior is probably related to the evolution of the MX particles during tempering. The average size of the particles of the second phase in the samples tempered to 780 °C during different times and subjected to creep to 600 °C, would indirectly indicate a state of dissolution and reprecipitation of MX particles, which occurs during the tempering. Creep rupture occurs by the nucleation, Se investigó el efecto del tiempo de revenido a la temperatura de 780 °C sobre la resistencia al creep del acero ASTM A335 grado P91. La temperatura de revenido correspondió a la temperatura de revenido industrial y los tiempos evaluados se eligieron de tal manera de acumular, entre el revenido previo del material de suministro (40 minutos) y el tratamiento realizado en el laboratorio, tiempos de 3; 4; 5; 5,5; 5,7; 6 y 7 horas, por lo que en la práctica se aplicó un doble revenido. Posteriormente, las muestras fueron ensayadas a 600 ºC y 190 MPa hasta rotura. Los resultados muestran que el tiempo de revenido a 780 ºC, tiene un efecto muy importante en la resistencia al creep del acero P91. Hasta 3 horas de revenido, el acero P91 mostró una buena resistencia al creep con una velocidad mínima de creep de 7x10 -9 s -1 . Una marcada caída en la resistencia al creep se observó para un tiempo de revenido de 5 horas (1.5x10 -7 s -1 ), con una posterior recuperación a las 5.5 horas (3x10 -8 s -1 ). Este comportamiento al creep probablemente esté relacionado a la evolución de las partículas MX durante el revenido. El tamaño promedio de las partículas de segunda fase en las probetas revenidas a 780º C con diferentes tiempos y sometidas a creep a 600º C, indicarían de manera indirecta un estado de disolución y re-precipitación de las partículas MX que ocurre durante el revenido. La rotura por creep ocurre por la nucleación, crecimiento y coalescencia de cavidades en regiones próximas a los límites de grano de austenita previa, resultando en una fisura y propagación de la fisura hasta su rotura. Palabras clave: Acero 9% Cr, Comportamiento a creep, Resistencia a creep, Precipitación.

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“…tempered martensite with different tempering degree, depending on the reached peak temperature during the welding. It is well known from other studies [16][17][18][19] that the normalized and tempered microstructures of T91 steels contain two types of precipitates, namely the intragranular MX (M= V, Nb; X = N, C) carbonitrides and intergranular M 23 C 6 (M= Cr, Fe) carbides at grain and subgrain boundaries. The microstructures of Ni WM Thermanit Nicro 82 close to the interface with T91 steel HAZ are shown in Fig.…”

Section: Microstructure Characterization In Conditions After Pwhtmentioning

confidence: 99%

Microstructure and creep characteristics of dissimilar T91/TP316H martensitic/austenitic welded joint with Ni-based weld metal

Falat

Svoboda

Výrostková

et al. 2012

Materials Characterization

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Evolution of precipitated phases during prolonged tempering in a 9%Cr1%MoVNb ferritic–martensitic steel: Influence on creep performance

Cited by 36 publications

References 21 publications

Microstructure Evolution in an Advanced 9Cr–1.5Mo–1Co–VNbBN Alloy during Heat Treatment and High Temperature Aging

Microstructure Evolution in an Advanced 9Cr–1.5Mo–1Co–VNbBN Alloy during Heat Treatment and High Temperature Aging

Influencia del tiempo de revenido a 780°C sobre la resistencia al creep del acero ASTM A335 P91

Microstructure and creep characteristics of dissimilar T91/TP316H martensitic/austenitic welded joint with Ni-based weld metal

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