Microstructure evaluation of UNS S32205 duplex stainless steel friction stir welds

Abstract

UNS S32205 duplex stainless steel welds were performed by friction stir welding (FSW). Advancing and retreating sides showed distinct characteristics in the welded joint. The advancing side shows the strongest grain refinement which is corroborated by microhardness measurements. The microstructure characterization was carried out by optical, scanning and transmission electron microscopy. The thermomechanically affected zone displays austenite islands deformed in a ferrite matrix. The stir zone (SZ) showed a fine recrystallized microstructure providing an outstanding increase of hardness associated with better corrosion performance. Transmission electron microscopy and corrosion tests have corroborated the absence of intermetallic phases on welded joints.

Effects of Heat Input on Microstructure, Corrosion and Mechanical Characteristics of Welded Austenitic and Duplex Stainless Steels: A Review

“…Although these levels of nitrogen are soluble in ferrite at high temperatures, Cr2N precipitates in the ferrite upon rapid cooling because nitrogen is relatively High toughness can be obtained by implementing suitable solution temperatures and cooling rates [61][62][63]. This finding is consistent with a previous report [64] indicating that the optimal solution temperature and cooling rate result in high toughness. In addition to austenite and ferrite, other phases may occur depending on the thermal history of the steel, when DSS is exposed to a temperature range of 300 to 1000 • C [65][66][67][68].…”

Friction stir welding of duplex and superduplex stainless steels and some aspects of microstructural characterization and mechanical performance

“…Figure 1 shows a schematic drawing of FSW with all the zones mentioned above. DSS 28 and SDSS 29 do not show HAZs on both sides (AS and RS) of the welded joint. The formation of different regions and the presence of several metallographic phases cause variations in the mechanical and microstructural properties of the metal, which makes it necessary to determine whether such features are improved or worsened.…”

Desenvolvimento de sistema de apoio com depósito cerâmico para soldagem e processamento por atrito com pino não consumível

“…Dentre elas, pode-se ressaltar a união no estado sólido excluindo os problemas decorrentes da solidificação. Adicionalmente, a microestrutura favorável tem sido mantida durante o processo de SAPNC e a precipitação de fases deletérias não tem sido observada [26][27][28]. Poucos trabalhos têm estudado processo de soldagem por atrito de aços inoxidáveis duplex com especial atenção à penetração completa.…”

“…A falta de penetração completa deixa uma superfície livre próxima à raiz que faz o papel de um entalhe no material favorecendo o rompimento do mesmo naquela região. Santos et al [28,30] estudando a soldagem por atrito com pino para o AID S32205 obteve penetração completa para chapas de espessura de 6 mm usando a chapa de apoio com depósito cerâmico.…”

“…Na Figura 8b e Figura 8c são mostradas as vistas frontal e lateral da junta soldada após ensaio de dobramento; observa-se que não houve abertura de raiz corroborando a penetração completa para o aço inoxidável duplex UNS S32101. Resultados semelhantes foram encontrados para o aço inoxidável duplex UNS S32205 [28,30] e os superduplex UNS S32750 e S32760 [31]. O resumo das propriedades mecânicas para o metal de base e para a junta soldada está apresentado na Tabela 2.…”