Corrosion Resistance of 904L Super Austenitic Stainless Steel Welded Joints

Abstract

In order to study the corrosion resistance of 904L super austenitic stainless steel welded joints in a simulated nuclear power plant tertiary loop water environment, the Kelvin probe force microscope (KPFM), electron backscatter diffraction (EBSD), electrochemical experiments and immersion corrosion experiments were used. These methods were employed to investigate the influence of the characteristic distribution of grain boundaries of welds and base materials, surface contact potential difference and medium temperature on the corrosion resistance of 904L welded joints and base metal. Results showed that the 904L base metal had higher Σ3 special grain boundaries and exhibited better corrosion resistance than the weld. The average potential differences on the surfaces of the weld and the weld fusion line were 318 mV and 295 mV, respectively, and a potential difference valley existed in the local area, which exhibited higher electrochemical activity. The critical pitting temperatures (CPT) of the base metal and the weld were 50 ℃ and 43 ℃, respectively, CPT Weld <CPT Base Metal. The change in temperature had a greater impact on the pitting potential (Eb) of the weld. With the increase in temperature, the pitting potential Eb of weld decreased sharply, and the corrosion rate increased significantly.

Keywords

• the kelvin probe force microscope (kpfm)|electron backscatter diffraction (ebsd)|contact potential difference|critical pitting temperature|pitting potential