Corrosion Behavior of HAZ Between C4 Nickel-Base Alloy/X60 Steel Dissimilar Metal Weldments
C4 nickel-base alloy and X60 steel were fabricated by Tungsten Inert Gas Welding (TIG) process using a CrNiMo-3 nickel base alloy welding wire filler metal under 100A welding current. The microstructure of welding joint was analyzed by SEM. Corrosion behaviors of heat effect zone (HAZ) and X60 steel matrix were investigated by electrochemical measurement. The obtained results show that weld metal zone consists of fully dendrite structure and the austenite grain of C4 nickel-base alloy coarsening in over-heat HAZ. The HAZ of X60 steel includes coarse (GHAZ) and fine grained zones (FGHAZ). Phase change from bulk ferrite with a small amount of pearlite to granular bainite at CGHAZ. Corrosion current density of matrix of X60 steel is between FGHAZ and CGHAZ.