Failure analysis of fillet welds with premature corrosion in 316L stainless steel slide gates using constitution diagrams

Abstract

The service environment of the slide gates may cause localized corrosion at welds. In this work, a failure analysis was conducted to determine the causes of the premature corrosion of the fillet welds before the commissioning. According to the contractor, the slide gates were manufactured in ASTM A240 Type 316L stainless steel and welded with GMAW using an ER316LSi filler metal. Test samples of the fillet weld metals were extracted from gates after a preliminary visual inspection. The samples were analyzed using ferrite number measurements, Optical Emission Spectrometry, chemical analysis, metallographic examination and Scanning Electron Microscopy with microanalysis. The analysis of results using the Schaeffler and WRC-92 constitution diagrams showed that the estimated chemical composition of the filler metal differs with the filler metal specified in the WPS suggesting that an incorrect carbon steel filler metal was used during the construction of the gates.

Keywords

• corrosion
• stainless steel
• filler metal selection
• Schaeffler diagram
• WRC-1992 diagram
• slide gate