Study of Cooling Rate Influence on SAF 2205 Duplex Stainless Steel Solution Annealed

Abstract

In this work was investigated the microstructural evolution process of the duplex stainless steel SAF 2205 as-cast after solution annealing treatment. The aim was to detect the effects on the material microstructure by the cooling rate variation. The studied material were submitted to solution anneal at 1100 °C for 240 min, followed by cooling in water, air and furnace. The results evaluation was based on micrographic analysis, energy dispersive spectrometry measurements (EDS), X-ray diffraction and hardness tests. The ferrite volume fraction obtained in the microstructure increased with the cooling rate, because it causes diffusion inhibition of the steel constituent elements, promoting retention of the ferrite. The volume fraction of austenite phase increased with a lower cooling rate. The cooling rate is an important factor in defining the steel microstructure, particularly about intermetallic phases precipitation, which occurred by the slow cooling rate. Additionally, it was observed the precipitation of sigma phase.

Temperature and time effect of thermal aging treatment on microstructure and corrosion resistance of UNS S31803 duplex stainless steel

“…The thermal treatment of solubilization is usually performed between 1000-1200°C, followed by cooling in water, to avoid the precipitation of undesirable intermetallic phases (Arturo, Hugo, Rafael, Egberto & Antonio, 2015, Majid & Shahi, 2020, Sáenz et al, 2020, Zeng et al, 2019. The thermal treatment of aging aims at promoting the precipitation of intermetallic phases such as α', σ and χ, and it can be performed after the thermal treatment of solubilization, for the steel to present only the desired phases according to the application (Berecz, Fazakas, Mészáros & Sajó, 2015, Chail & Kangas, 2016, Cronemberger et al, 2014, Cronemberger, M. E. R., Nakamatsu, S., Rovere, C. A. D., Kuri, S. E. & Mariano, N. A., 2015. Phase α' is a precipitate rich in chromium and it occurs inside α, it presents a body-centered cubic (BCC) structure, coherent with the ferritic matrix, and since it has low energy of interface with the ferritic matrix, it presents high resistance to coalescence (Chen & Limin, 2015, Cronemberger et al, 2015, Hilders, Zambrano & Ochoa, 2018, Jinlong, Tongxiang, Lacerda, Cândido, & Godefroid, 2015.…”

Effect of Cooling Rate on the Corrosion Behavior of As-Cast SAF 2205 Duplex Stainless Steel after Solution Annealing Treatment

“…However, the protection potential of the moderately cooled sample was about 80% lower, indicating that the repassivation process was more difficult, probably due to the formation of small depleted regions, which may have favored the instantaneous process of pitting nucleation and repassivation. This can be explained by the variations in volume fraction of ferrite and austenite phases 9 obtained for this sample (demonstrated in a previous work 16 ). On the other hand, the sample cooled slowly presented lower values of corrosion, pitting and protection potential.…”

Effect of Precipitation of Alpha Line and Sigma Phases on the Microstructure and Corrosion Resistance of the Duplex Stainless Steel SAF 2205

“…The thermal treatment of solubilization aims to promote a homogeneous microstructure composed of ferrite (α) and austenite (γ) and redissolve undesired compounds [1][2][3][4][5][6][7][8][9] .…”