CONICET | Buscador de Institutos y Recursos Humanos

Supermartensíticos stainless steels (SMSS) have been developed as an alternative technology for the gas and oil industry, being an economical choice, offering good corrosion resistance and good mechanical properties, especially in environments containing CO2 (sweet corrosion) and low levels of H2S (mildly sour corrosion). However, under certain conditions of pressure of CO2, temperature and presence of chloride, has been reported the corrosion failure in these materials. Also, aspects related to welding process, strongly affect the microstructural evolution and mechanical properties and may in turn change the corrosion resistance of weld deposits. The aim of this work was to study the effect of shielding gas and post weld heat treatments on localized corrosion resistance and stress corrosion craking (under pressure of CO2, temperature and high chloride concentration) of deposit without dilution of a stainless steel supermartensítico. To this end, two specimens were welded according to ANSI / AWS A5.22-95, using the following protective gas mixtures: 95% Ar-5% He and 80% Ar-20% CO2. We assessed the deposits obtained in condition "as welded and post weld heat treatment of solubilised and double tempering. We determined the chemical composition of deposits and microstructural characterization was carried out by optical microscopy and scanning electron microscopy and X-ray diffraction We measured the microhardness and tensile properties in various conditions tested. Corrosion tests were performed by localized corrosion and stress corrosion craking, using the configuration of three point bending under constant strain. The medium used was a solution concentrated in Cl-(165 g / L of Cl-dissolved) and 10 kg/cm2 pressure of CO2 at a temperature of 100 ° C for 720 hours. We analyzed and discussed the results linking changes in composition and microstructure with the properties obtained.

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