ABSTRACT
Austenitic stainless steel and nickel-base alloys welds are widely used in nuclear reactor components, plants of energy generation, chemical, and petrochemical industries, due to their high corrosion resistance. The post weld heat treatments (PWHT) are generally applied to welding in order to relieve the welding residual stress. The aim of this work was to evaluate the influence of different PWHT on corrosion behavior of a dissimilar weld joint of two AISI 316L austenitic stainless steel plates with a nickel-base alloy as filler material in saline environments. The material was submitted to heat treatments for three hours at 600, 700 and 800 °C. The weld joint was examined by optical microscopy to determine the effects of PWHT in the microstructure. The corrosion behavior of the samples before and after heat treatment was evaluated using cyclic potentiodynamic polarization (CPP) in sodium chloride solutions (19% v/v) and pH 4.0 at room temperature. Metallographic analyses showed that delta ferrite dissolute as PWHT temperature increased. CPP curves demonstrated an increase of pitting corrosion resistance as the PWHT temperature rises, although the pit size has been increased. The heat treated weld joint at 600 °C showed a similar corrosion resistance compared to as-welded material.
Keywords
weld joint; post-weld treatment; polarization; pitting corrosion
