Unexpected failure of cast superduplex stainless steel exposed to high chlorides containing water: From failure analysis to corrosion mechanisms settlement

This work deals with the failure analysis of a super duplex valve operating in technical waters with high chlorides content up to 80 degrees C. A careful fracture surfaces and microstructural characterization was combined with corrosion studies (SKPFM (Scanning Kelvin Probe Force Measurements) and polarization curves) of different valve regions in order to determine the failure mechanism. It was found that the cast material presents a segregated microstructure containing ferritic phases with different PREN (Pitting Resistance Equivalent Number). This strongly affects the corrosion properties of the material, enhancing the susceptibility to localized corrosion and leading to SCC (Stress Corrosion Cracking) failure.

Automated summary

This study focuses on the failure analysis of a super duplex valve operating in technical waters with high chlorides content. The investigation combines careful fracture surfaces and microstructural characterization with corrosion studies to determine the failure mechanism as stress corrosion cracking.