Different aspect of pitting corrosion and interphase corrosion in the weld heat-affected zone of high-nitrogen Fe-18Cr-10Mn-N steel

摘要

Phase transformation and its effects on corrosion behavior in the weld heat-affected zone (HAZ) of a metastable high-nitrogen Fe-18Cr-10Mn-N austenitic stainless steel were investigated through electrochemical tests, electron probe micro analysis and electron microscopy analysis. Electrochemical tests showed that pitting corrosion and interphase corrosion were significantly affected by δ-ferrite formation in the HAZ and showed changing characteristics with increasing δ-ferrite fraction. Pitting corrosion resistance was reduced by the formation of a Cr-depleted zone along the δ-ferrite/austenite phase boundary due to δ-ferrite formation. However, pitting corrosion resistance did not change with increased peak temperature in the HAZ despite the increasing δ-ferrite fraction. Sensitivity to interphase corrosion was strongly affected by the amount of δ-ferrite/austenite phase boundary and δ-ferrite area, gradually increasing with increasing δ-ferrite fraction. These dissimilar corrosion behaviors were carefully investigated and are discussed in terms of phase transformation and alloying element partitioning in the HAZ.