Ref.: MmeCo03-001
Apresentador: Andre Rocha Pimenta
Autores (Instituição): Barros, T.S.(Centro Federal de Educação Tecnológica Celso Suckow da Fonseca); Tavares, S.S.(Universidade Federal Fluminense); Pimenta, A.R.(Instituto Federal do Rio de Janeiro); Batista, R.T.(Instituto Nacional de Tecnologia); Velasco, J.A.(Instituto Nacional de Tecnologia);
Resumo:
Due to their excellent mechanical behavior and high corrosion resistance, duplex stainless steels (DSS) may be selected to operation in environments where hydrogen uptake occurs. One of these harsh conditions is the operation in high salinity solutions containing CO2 and H2S in the oil and gas off-shore production. For these uses the NACE 0175/ISO 15156 standard serve as instrument for materials selection and good practices, but operational limits are not completely defined. As observed in other metallic and non-metallic materials, the performance of DSSs depends on fabrication processes. In this work, the susceptibilities of two DSSs 2205 (UNS S31803) to sulfide stress corrosion (SSC) in saline solutions with three pH levels (3.5, 4.5 and 5.5) were investigated. The difference between the two DSSs studied is the fabrication route, which were seamless tube hot rolling (HR) produced by Mannesman process and powder metallurgy with compacting and sintering final operations by hot isostatic pressure (HIP). The steels were solution treated at 1060ºC for 1h and water quenched. The microstructural features of both materials were investigated. The susceptibility parameters were evaluated by slow strain rate tensile (SSRT) tests. Results demonstrated that both materials suffered embrittlement in solutions with pH 3.5 and 4.5, but the susceptibility parameters were slightly better in the hot rolled steel. In tests in the solution with pH 5.5 the hot rolled specimens fractured with ductile behavior, without secondary cracks. In contrast, the HIPed specimens were brittle and very susceptible to SCC in the tests with pH 5.5. The better resistance of DSS hot rolled to SSC can be explained by microstructural features such as the lower grain size and austenite island interspace in comparison to the material produced by PM-HIP.