748 K (475 °C) Embrittlement of Duplex Stainless Steel: Effect on Microstructure and Fracture Behavior

Abstract

22Cr-5Ni duplex stainless steel (DSS) was aged at 748 K (475°C) and the microstructure development correlated to changes in mechanical properties and fracture behavior. Tensile testing of aged microstructures confirmed the occurrence of 748 K (475°C) embrittlement, which was accompanied by an increase of strength and hardness and loss of toughness. Aging caused spinodal decomposition of the ferrite phase, consisting of Cr-enriched a¢¢ and Fe-rich a¢ and the formation of a large number of R-phase precipitates, with sizes between 50 and 400 nm. Fracture surface analyses revealed a gradual change of the fracture mode from ductile to brittle delamination fracture, associated with slip incompatibility between ferrite and austenite. Ferrite became highly brittle after 255 hours of aging, mainly due to the presence of precipitates, while austenite was ductile and accommodated most plastic strain. The fracture mechanism as a function of 748 K (475°C) embrittlement is discussed in light of microstructure development.

Time-dependent in situ measurement of atmospheric corrosion rates of duplex stainless steel wires

“…The wires were then anodically etched using 40 wt.% KOH at 5 V for a few seconds, which preferentially stains the ferrite phase. 31,67 The microstructure was analysed in an SEM using 10-20 kV with a spot size of 3-4, and secondary electron (SE) and backscattered electron (BSE) images are reported here.…”

Efeito Do Envelhecimento Térmico Nas Propriedades Mecânicas E Microestruturais Do Aço Inoxidável Uns S31803

“…Os resultados estão apresentados por meio da gráfico de barras da Figura 4, com os respectivos desvios padrões. Em um trabalho realizado por Örneket al (2017) [19]mostram que a deformação das amostras tratadas à 475ºC já apresentaram uma redução significativa após 20 horas, o que indica sinais claros de fragilização. A deformação é considerada medida de ductilidade e formabilidade dos materiais.…”

“…Áreas de fratura por clivagem e a presença de dimples, podem ser observada pela Figura 6c. Em um trabalho realizado por Örneket al (2017) [19] foi estudado a fragilização causada pela fase α' no aço inoxidável duplex do tipo 2205. Observaramque a fratura apresenta trincas com aparência profunda e fibrosa, Figura 6a.…”

“…Bandas de deslizamentos nas regiões com os dimplesalongados. As bandas de deslizamentos como indicado na Figura 6b, com presença de alguns dimplesalongados, foram descritos por Örneket al (2017) [19] como aspecto dedelaminação. Esse fenômeno ocorre devido a incompatibilidade na interface de contorno de grãoferrita/austenita [19].…”

Hydrogen Distribution in a Duplex Stainless Steel Investigated by Means of Hydrogen Microprint Technique

“…Hydrogen diffusion in the ferrite proceeds much faster than in the austenite, despite the lower solubility than in the austenite. [10][11][12] Several researches and experiments have been devoted to characterizing and determining the factors affecting HE, [13][14][15][16][17]…”