Correlation Between Microstructure and Pitting Corrosion Behavior of TLP Bonded DSS-2205/Ni–P/DSS-2205 Specimens

Abstract

The correlation between microstructure and pitting corrosion resistance of transient liquid phase (TLP) bonded 2205 duplex stainless steel (DSS) using BNi-6 interlayer (Ni–10.8 wt% P) was investigated. Experimental results revealed that not only progress of the isothermal solidification (IS), but also cooling procedure after the TLP bonding considerably affected the pitting corrosion resistance of the TLP bonded specimen. Potentiodynamic polarization (PDP) results revealed that pitting potential of the furnace cooled TLP specimen (FC-TLP) was increased from + 0.274 to + 0.557 V by completing the IS. SEM/EDS analyses showed that the bonding zone (BZ) was the weakest zone to pitting corrosion before completing the IS and the pitting attacks severely occurred in the bonding zone (BZ) centerline. After completion of the IS, the pitting corrosion preferentially occurred in vicinity of (Mo–P) rich intermetallic precipitates in the diffusion affected zone (DAZ) of FC-TLP specimen. Microstructural studies also revealed that water quenching after the TLP bonding prevented the formation of (Mo–P) rich intermetallic precipitates in the DAZ. It resulted in the significant increase of the pitting potential of water cooled TLP specimen to + 1.096 V after IS completion, which was very close to that of the as-received BM (+ 1.220 V).