Evaluation of the stress corrosion resistance of a austenitic stainless steel welded joint with nickel alloy 182 as an addition material in medium containing chloride

Austenitic stainless steel and nickel-base alloys welds are widely used in nuclear reactor components, plants of energy generation, chemical, and petrochemical industries. The welding process and post weld heat treatment results in microstructural variations that may affect the material's mechanical properties and corrosion resistance. The aim of this work is evaluate the electrochemical corrosion and stress corrosion cracking behavior in chloride environments of a dissimilar weld joint of two AISI 316L austenitic stainless steel plates with a nickel-base alloy as filler material. The material was submitted to heat treatments for three hours at 600, 700 and 800 °C. The weld joint was examined by optical microscopy and scanning electron microscope to determine the effects of PWHT in the microstructure. Metallographic analyses showed that delta ferrite dissolute as post weld heat treatments temperature increased. Cyclic potentiodynamic polarization evaluates the weld joint pitting corrosion susceptibility and demonstrated a decrease of pitting corrosion resistance as the PWHT temperature rises. Stress corrosion cracking is evaluated by slow strain rate test in chloride solutions (19% m/m) and pH 4.0 at room temperature and at 80 °C. The material showed no stress corrosion cracking susceptibility in the environment of study at room temperature. The increase in post weld heat treatment temperature decreased mechanical properties and increased stress corrosion cracking susceptibility of welded joint in 19 %wt. NaCl and pH 4.0 at 80 °C medium. (author)