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Abstract
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The effect of friction stir welding (FSW) on the
pitting corrosion resistance of a lean duplex stainless steel
was investigated in chloride-containing and chloride-free electrolytes.
FSW was carried out by employing a constant rotation
speed of 800 rpm at the welding speeds of 50, 100, and
150 mm/min using WC-based tool. Cyclic polarization results
showed the same corrosion resistance of the base metal and
welded joints in 0.1 MH2SO4. The optical microscopy observations
after cyclic polarization tests revealed that no signs of
pitting corrosion were evident for the base metal and different
FS welds in chloride-free 0.1 M H2SO4 solution. In contrast,
a wide positive hysteresis loop indicative of pitting corrosion
susceptibility was displayed for the base metal and FS welds
in 0.1 M H2SO4 0.1 M NaCl solution. The optical micrographs
of pitting corrosion in the base metal and various FS
welds demonstrated that the size of pits was decreased and the
number of pits was increased after FSW. It was also found that
increasing the welding speed led to an increase in the number
of pits and a decrease in the size of pits. In other words, the
resistance to pit growth was improved by decreasing the heat
input during FSW. These results were interpreted with respect
to the noticeable grain refinement that occurred during FSW.
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