Characterization of the Weld Structure in a Duplex Stainless Steel Using Color Metallography

A three-step etching technique, utilizing a Glyceregia etch, a 10% oxalic acid electrolytic etch, and a boiling Murakamiʹs reagent etch, was employed to reveal the weld structure in a commercial duplex stainless steel alloy. Color metallography indicated that chromium segregation, which is residual from significant phase composition differences in the original ferrite-austenite base metal structure, existed in all areas of the weld heat-affected zone. Evidence of fine chromium-rich precipitates distributed homogenously within the ferrite grains and heterogenously at ferrite subgrain boundaries in the middle and near heat-affected zone regions was observed and correlated with local variations in chromium content.