Stress Corrosion Cracking of an Austenitic Stainless Steel Pipe Weld

摘要

Stress corrosion cracking is an issue for nuclearpower plants and can affect many different components.This investigation was initiated because a stainless steelpipe weld was identified to have a leak. Breaking openthe cracked pipe and conducting fractography using ascanning electron microscope identified intergranularcracking, indicating stress corrosion cracking as thefailure mode. Pitting corrosion and large areas ofintergranular attack were identified on the inner diameterof the pipe. As austenitic stainless steel is not typicallysusceptible to stress corrosion cracking in the pressurizedwater reactor (PWR) environment, additional tasks wereconducted to identify the source of the materialssusceptibility.Hardness testing did not identify any elevated hardness.An ASTM A262 practice A etch test identified somepotential low levels of sensitization. Energy dispersive Xrayspectroscopy identified sulfur at levels greater thanone percent on much of the inner diameter of the pipe. Assulfur can cause SCC at relatively mild conditions, thiswas likely the factor that caused stress corrosion crackingsusceptibility.